9 Intraoral Radiographic Technique










80
9
Intraoral Radiographic Technique:
The Paralleling Method
EDUCATIONAL OBJECTIVES
Upon completing this chapter, the student will be able to:
1. Dene the key terms listed at the beginning of the chapter.
2. Discuss the following related to the radiographic survey:
• Knowtheimportanceofradiographsintreatment
planning and diagnosis.
• Explainwhatfactorsareinvolvedinprescribingdental
radiographs.
• Statethecomponentsofageneralfull-mouthsurvey
(FMS),apediatricFMS,andanedentulousFMS.
• Describewhatshouldbeseenonperiapicaland
bitewing projections and what the indications for use
are for both projections.
• Knowthe8criteriaforacceptableintraoralradiographs.
3. Listtheprinciples,advantages,anddisadvantagesofthe
paralleling technique.
4. Recitetheroutineinpreparingforandexposingdental
radiographs,andexplainthepurposeofhavingasystematic
sequencewhenexposingradiographicimages.
5. Discusstheadvantageofusingaparallelingreceptor-
holdingdevice(i.e.,extensionconeparalleling[XCP]
instrument)whenexposingintraoralradiographs.
6. Discuss the following related to the paralleling method:
• Listthesixfactorsthatmustbeconsideredinany
periapical projection.
• Knowwhatfactorsareconsideredindeterminingthe
exposuretimesettingfordentalradiographicexposures.
• Beabletoapplytheprinciplesoftheparallelingintraoral
radiographictechniquetoexposingallperiapicaland
bitewing radiographs indicated for their dental patients.
7. Knowthecauses,appearances,andremediesforthe
discussedexposureerrors,aswellaslistthethree
mostcommonbitewingerrors,includingtheircauses,
appearance,andremedies.
produce the most diagnostically acceptable radiographs
possible while keeping the patient’s exposure to x-radiation
at a minimum. Furthermore, only those radiographs that
address the patients immediate dental health needs should
be taken. Radiographers should rene their technique in an
eort to reduce the number of retakes and ultimately the
amount of radiation exposure to their patients. is chapter
Introduction
e radiographic examination is an integral component of
formulating a diagnosis and treatment plan for the dental
patient. It is of the utmost importance that the radiographic
images of the patient’s oral structures be diagnostically
acceptable. It is the dental professional’s responsibility to
KEY TERMS
bitewing projection
chair position
collimator cuto (cone cutting)
dimensional accuracy
dimensional distortion
double exposure
elongation
exposure routine
extension cone paralleling (XCP)
technique
lm reversal
foreshortening
full-mouth survey (FMS)
hemostat
horizontal angulation
localizing ring
long axis
long cone technique
occlusal plane
overexposure
overlapping
patient movement
periapical projection
point of entry
receptor position
right-angle technique
sagittal plane
underexposure
vertical angulation
vertical bitewings

81CHAPTER 9 Intraoral Radiographic Technique: The Paralleling Method
root and 2 to 3 mm of surrounding periapical bone. is
projection is necessary to diagnose normal or pathologic
conditions of tooth crowns and root, bone, and tooth
formation and eruption (Fig. 9.2).
e bitewing projection can be taken only if there are
opposing teeth to hold the receptor in position with their
occluding surfaces. is projection shows the upper and
lower teeth in occlusion in one image. Only the crowns
and alveolar crest of the bone of adjacent teeth are seen.
It is used for detecting interproximal decay, periodontal
bone loss, recurrent decay under restorations, and faulty
restorations (Fig. 9.3). Bitewing projections can be taken
of the anterior teeth but are usually taken in the posterior
regions. Proponents of the use of vertical bitewings point
out that, in this position, more root is seen and thus can
be more diagnostic for root caries, receding alveolar bone
levels, and in pediatric patients to see the progress of the
secondary dentition.
e FMS shows all of the teeth in the mandible and
maxilla, as well as the surrounding bone. Each tooth is shown
at least twice in the survey; that is, the maxillary second
premolar can be seen on the premolar periapical image and
on the premolar bitewing projection. Some teeth may be
seen in three or four views. is gives the diagnostician an
opportunity to view the tooth from dierent radiographic
angles, eliminating the possibility that an artifact could be
mistaken for caries or other pathologic conditions.
Pediatric Full-Mouth Survey
Depending on the child’s age and the size of the child’s
mouth, the composition of the FMS may vary. A report
of the Selection Criteria Panel recommends that only two
bitewing images be taken for the asymptomatic clinically
negative pediatric patient with closed posterior contacts.
For asymptomatic and clinically negative pediatric patients
with open posterior contacts, no radiographs are necessary.
For patients up to 5 years old who are in need of an
FMS, the operator should use the pediatric-size receptor #0
for anterior, posterior, and bitewing projections (Fig. 9.4).
e FMS at this age entails 12 projections: three maxillary
anterior projections, three mandibular anterior projections,
four mandibular and maxillary molar projections, and two
bitewing projections. Only one molar bitewing projection
is taken on each side.
In the 6-year-old to 9-year-old group, the pediatric
receptor (#0) or narrow adult receptor (size #1) can be
used for anterior projections, because the child’s arch shape
at this age can still be very narrow. For posterior projections,
adult size #2, narrow adult, or pediatric receptor (#0) is
used, depending on the size of the arch. At this age, two
posterior periapical projections in each quadrant are taken,
because the 6-year molars have erupted and the dental arch
has lengthened. One bitewing projection on each side is
also used.
After 9 years old, the full adult series is taken, with the
narrow adult receptor being used where necessary. ese age
discusses the types of intraoral radiographs available; the
paralleling exposure technique; receptor-holding devices;
and the appearance, cause, and remedy for various common
exposure errors in dental radiography. Film-based and
digital radiographic techniques are discussed here; the
digital radiographic techniques are further discussed in
Chapter 15.
The Radiographic Survey
Intraoral radiography is a dental imaging technique uti-
lized when the image receptor is placed inside the patients
mouth and the source of radiation is positioned outside of
the patient’s mouth. e x-ray prescription for intraoral
radiographs is custom t to a patients dental health needs.
e number and type of images exposed can vary depend-
ing on the needs of the patient. e full-mouth intraoral
radiographic survey is one option in choosing the neces-
sary radiographs for a particular patient to complete the
patient’s oral diagnosis. A dental examination or treatment
plan cannot be considered complete without current or
valid radiographs; in some cases, the full-mouth survey
(FMS) is the radiographic procedure of choice. e FMS
is a challenging procedure to perform correctly; it requires
time and meticulous attention to detail. It bears with it the
responsibility of exposing the patient to the least amount of
ionizing radiation to obtain the maximum diagnostic yield.
Unnecessary radiographs or those of poor quality that do
not have diagnostic value do not serve the patient’s needs
and only add to the patient’s radiation burden. Regardless
of which member of the dental team takes the radiographs,
the same quality standards are maintained for all dental
professionals.
e radiographic FMS is usually composed of 14 or more
periapical projections and, where possible, four posterior
bitewing projections (Fig. 9.1). e bitewing projections
can be held vertically or horizontally. is text discusses
a 14-periapical and a four-horizontal bitewing image
technique. Some series of more than 14 periapical projec-
tions include distal maxillary molar projections, vertical
bitewings, anterior bitewings, and individual radiographs
using #1 size narrow anterior projections of the six maxillary
and four mandibular anterior teeth.
e number of radiographs in an FMS can be modied
to include extra or fewer projections, depending on the size
of the patient’s mouth or tooth position. In all cases, the
minimum number of images that satises the diagnostic
requirements of an FMS should be used. Film mounts and
digital templates are available in various combinations of
numbers and sizes of receptors. e radiographic survey
should not be determined by the lm mount or digital
template available or by any other reason not related to
dental health but strictly by the diagnostic needs of the
patient. e recommended intraoral projections are listed
in Table 9.1.
A periapical projection shows the entire tooth from
the incisal edge or the occlusal surface to the apex of the

82 CHAPTER 9 Intraoral Radiographic Technique: The Paralleling Method
A
Figure 9.1 A, A 19-image full-mouth survey (FMS). B, An 18-image FMS.
guidelines are exible and depend on the growth and devel-
opment of the child. As a rule, it is best to use the largest
receptor size that the patient can accommodate comfortably
(Fig. 9.5). Keep in mind that the extraoral panoramic image
can also be used with pediatric dental patients, especially to
evaluate eruption patterns and growth and development.
Edentulous Series
A radiographic examination can be performed even though
the patient may be wholly or partially edentulous. e
absence of teeth in an area of clinical examination does
not preclude the possibility of retained roots, impacted
teeth, cysts, or other occult pathologic conditions that
may be present in the bone. e edentulous examination
may use periapical projections, occlusal projections, or a
panoramic radiograph. e intraoral edentulous series is
usually composed of 13 periapical projections. e bitewing
images are not taken, because there are no opposing teeth
to support the bitewing receptor-holding device or bitewing
tabs, and only one image is taken in the maxillary central,
lateral, and canine regions (Fig. 9.6). In small edentulous
mouths, a survey consisting of 11 projections may suce
by use of only one mandibular periapical projection and

83CHAPTER 9 Intraoral Radiographic Technique: The Paralleling Method
Maxillary Mandibular
Central and lateral incisors Central and lateral incisors
Right and left canines Right and left canines
Right and left premolars Right and left premolars
Right and left molars Right and left molars
Bitewing
Right and left premolars
Right and left molars
The Recommended Projections of the
Radiographic Survey
TABLE
9.1
Figure 9.2 Anterior (A) and posterior (B) periapical radiographs.
Note that the entire tooth and surrounding periapical bone are shown.
B
Figure 9.3 A, Bitewing radiograph. Note that only the crowns,
alveolar ridge, and a small part of the roots of opposing teeth are seen.
B, Bite-wing tab for digital sensors. (Courtesy Dentsply Rinn, York, PA.)
Figure 9.4 Size #0 pediatric lm for anterior, posterior, and bitewing
projections.
extension of the premolar projection anteriorly to include
the canine area.
e receptors are positioned in the same way as in a
regular dentulous series but with certain modications. e
crest of the edentulous ridge replaces the occlusal plane
of the teeth as the plane of orientation. e receptor is
positioned either
1
8
inch above (for mandibular projec-
tions) or
1
8
inch below the ridge (for maxillary projections).
Because there are no teeth and there may be a great deal
of ridge resorption, it may be dicult to parallel the long
axis of the receptor with the long axis of the edentulous
ridge. us, the receptor lies atter against the palate or in
the oor of the mouth. In these cases, it may be possible to
support the receptor with cotton rolls to achieve parallelism
or, if necessary, to increase the vertical angulation and use
the bisecting angle technique. e best guideline in the
edentulous series is to adjust the vertical angulation so
that the central ray is almost perpendicular to the receptor
(similar to the angulation used for occlusal projections).
Any slight foreshortening that may result will not aect the
diagnosis of any intrabony conditions.
ere are two possible alternatives for the edentulous
periapical survey. e rst is a panoramic survey (Fig. 9.7).
e second is the use of an occlusal projection (Fig. 9.8),
the technique of which is discussed in Chapter 10. e
entire maxillary and mandibular ridges usually can be seen
on their respective occlusal projections. Both the panoramic
and the occlusal are survey projections; if any suspicious
areas are seen, a periapical projection of the area can be
done to obtain better denition for formulating a denitive
diagnosis.
e criteria for judging whether a single radiograph or
a FMS is diagnostically acceptable are listed in Box 9.1.

84 CHAPTER 9 Intraoral Radiographic Technique: The Paralleling Method
Figure 9.5 Pediatric full-mouth survey (FMS) of a 9-year-old patient.
Figure 9.6 A 13-image edentulous survey.
Figure 9.7 Edentulous panoramic survey.
If a single radiograph does not meet these criteria and
cannot provide diagnostic value, it must be retaken. In an
FMS, those areas and structures that do not appear on
the primary image may be seen on adjacent projections
in the series. Although a technically perfect FMS is ideal,
retakes should not be performed unless they are necessary
for proper diagnosis.
Quality Assurance
e criteria for diagnostically acceptable radiographs (as
shown in Box 9.1) should be used to evaluate radiographs
taken by dentists and dental professionals as part of a
quality assurance program. is can be accomplished
either by self-evaluation and criticism of ones own work
or by peer review. In this manner, technical errors can be
corrected and high-quality diagnostic radiographs will be
produced. Quality assurance is discussed further in a later
chapter.
Paralleling Technique
e basic principles of the paralleling technique for intraoral
periapical projections is that the receptor and the long axis
of the tooth being radiographed must be parallel to each
other, and the central ray of the x-ray beam must be directed
perpendicular to both (see Fig. 3.13). To accomplish this

85CHAPTER 9 Intraoral Radiographic Technique: The Paralleling Method
Figure 9.8 A, Edentulous occlusal survey of maxilla. B, Edentulous occlusal survey of mandible.
BOX 9.1 Criteria for Intraoral Radiographs
1. The radiograph should show proper denition and detail and
a degree of density and contrast so that all structures can be
delineated easily.
2. The structures should not be distorted either by elongation or
by foreshortening.
3. The radiograph should show the teeth from the occlusal or
incisal edges to 2 to 3 mm beyond their apices.
4. In a full-mouth survey (FMS), the entire alveolar processes of
the mandible and maxilla must be seen, as far distal as the
tuberosity in the maxilla and the beginning of the ascending
ramus in the mandible.
5. All interproximal surfaces of the teeth should be seen without
overlapping provided that the teeth are not overlapped in the
mouth.
6. The x-ray beam should be centered on the receptor so that
there are no unexposed parts on the image (“collimator
cutoff” or “cone cuts”).
7. The radiograph should not be cracked or bent or have any
other artifacts.
8. The radiograph should be processed properly.
parallelism, the object-receptor distance must be increased.
is distance can be sizable in some areas, such as the maxil-
lary molar projection, where the receptor may have to be
held at the midline of the palate to achieve this parallelism.
e increased object-receptor distance results in loss of
image sharpness, which is a problem that can be compensated
Figure 9.9 Bisecting 8-inch target-receptor distance (FFD) technique and paralleling 16-inch extended-
cone technique. Note superimposition of zygomatic arch on apices of maxillary molar in bisecting
technique. (Courtesy DENTSPLY Rinn, Elgin, IL.)
for by using an increased, 16-inch, target-receptor distance
(or focal-lm distance [FFD]; Fig. 9.9).
e paralleling technique has often been called the long
cone technique. is terminology is not as accurate in con-
temporary dentistry, in which the target-receptor distance
may be from 12 to 16 inches because of a recessed target (in
the x-ray tube head) rather than as a result of the length of
the position-indicating device (PID). Other names for the
paralleling technique are the extension cone paralleling
(XCP) technique or right-angle technique, both of which
stress two important principles of the technique.
Advantages and Disadvantages of the
Paralleling Technique Compared with the
Bisecting Angle Technique
When the paralleling and bisecting techniques are com-
pared, the consensus is that dental professionals prefer
the paralleling method as the technique of choice. e
American Academy of Oral and Maxillofacial Radiology
(AAOMR) states the following through its Parameters of
Care Committee: “e paralleling technique should be used
with its appropriate armamentarium, when possible, as it
provides the most geometrically accurate image of the denti-
tion.” e paralleling technique produces better diagnostic
images, less exposure to critical organs (such as, the thyroid
gland and the lens of the eye), a smaller exit dose, and easier
standardization and execution than the bisecting technique.

86 CHAPTER 9 Intraoral Radiographic Technique: The Paralleling Method
could assume the presence of adequate bone for restora-
tions, xed splinting, and so forth, on the basis of distorted
radiographic images.
With the paralleling technique, it is possible to diagnose
and evaluate caries and alveolar bone height accurately on
all radiographs and not rely on the bitewing projections, as
users of the bisecting technique do. It is interesting to note
that bitewing projections in both techniques are paralleling
projections due to the inherent parallel relationship between
the receptor and the tooth in the bitewing radiographic
technique.
In the bisecting technique, the radiopaque image of the
zygomatic arch is often superimposed on the apices of the
maxillary molars, making diagnosis dicult if not impos-
sible. is superimposition is understandable, because the
point of entry of the central ray for molar projections is
along the zygomatic arch.
e paralleling technique produces no superimposition of
the zygomatic arch, because the central ray, which is perpen-
dicular to the long axis of the molars, enters below the level
of the zygomatic arch. Also, in the paralleling technique,
the vertical angulation of the primary beam is rarely more
than plus or minus 10 degrees, compared with the vertical
angulation of 40 to 50 degrees in the bisecting technique.
e lack of extreme vertical angulation with the paralleling
method reduces the exposure to the thyroid gland and the
lens of the eye, because they no longer lie in the path of
the primary beam. In addition, the 16-inch target-receptor
distance (or FFD) used with the paralleling technique
reduces the volume of tissue irradiated when com-
pared with the recommended 8-inch target-receptor
Advantages of the Paralleling Technique
e major advantage of the paralleling technique is that,
when performed correctly, it forms an image with both
linear and dimensional accuracy to support a more valid
diagnosis. e key terms are dimensional accuracy and
dimensional distortion.
e bisecting technique, if used properly, correctly
represents the teeth linearly but produces dimensional
distortion. e bisecting technique can project the images
and surrounding structures on the receptor in a true linear
relationship without elongation or foreshortening. e
teeth and bone, however, are three-dimensional objects; and
although their overall length may be recorded accurately,
the relationship of one part of the tooth to another is
distorted dimensionally (Fig. 9.10). ose parts of the tooth
that lie farthest from the receptor, such as the buccal plate
of bone and buccal roots, are foreshortened; although their
lingual linear counterparts are not. A classic clinical example
consists of comparing the length of the buccal roots with
that of palatal roots in maxillary rst molars. Clinicians
who have used the bisecting technique for many years may
come to believe that the buccal roots are much shorter
than they really are because of dimensional distortions.
One may argue that this may not be clinically important
except in an initial endodontic measurement, but when this
distortion is applied to periodontal evaluation of alveolar
bone levels, the clinical importance becomes apparent (Fig.
9.11). In the bisecting technique, the image of the buccal
bone level is guratively added to the palatal bone height
to give a distorted image. A diagnosis and treatment plan
B
A
Figure 9.10 Radiographs of maxillary molar taken with bisecting
technique (A) and the paralleling technique (B). (Courtesy DENTSPLY
Rinn, Elgin, IL.)
Figure 9.11 Radiographs of the same area taken with the parallel-
ing technique (A) and the bisecting technique (B). Note the difference
in alveolar bone height, as indicated by arrows.

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809 Intraoral Radiographic Technique: The Paralleling MethodEDUCATIONAL OBJECTIVESUpon completing this chapter, the student will be able to:1. Dene the key terms listed at the beginning of the chapter.2. Discuss the following related to the radiographic survey:• Knowtheimportanceofradiographsintreatmentplanning and diagnosis.• Explainwhatfactorsareinvolvedin“prescribing”dentalradiographs.• Statethecomponentsofageneralfull-mouthsurvey(FMS),apediatricFMS,andanedentulousFMS.• Describewhatshouldbeseenonperiapicalandbitewing projections and what the indications for use are for both projections.• Knowthe8criteriaforacceptableintraoralradiographs.3. Listtheprinciples,advantages,anddisadvantagesoftheparalleling technique.4. Recitetheroutineinpreparingforandexposingdentalradiographs,andexplainthepurposeofhavingasystematicsequencewhenexposingradiographicimages.5. Discusstheadvantageofusingaparallelingreceptor-holdingdevice(i.e.,extensionconeparalleling[XCP]instrument)whenexposingintraoralradiographs.6. Discuss the following related to the paralleling method:• Listthesixfactorsthatmustbeconsideredinanyperiapical projection.• Knowwhatfactorsareconsideredindeterminingtheexposuretimesettingfordentalradiographicexposures.• Beabletoapplytheprinciplesoftheparallelingintraoralradiographictechniquetoexposingallperiapicalandbitewing radiographs indicated for their dental patients.7. Knowthecauses,appearances,andremediesforthediscussedexposureerrors,aswellaslistthethreemostcommonbitewingerrors,includingtheircauses,appearance,andremedies.produce the most diagnostically acceptable radiographs possible while keeping the patient’s exposure to x-radiation at a minimum. Furthermore, only those radiographs that address the patient’s immediate dental health needs should be taken. Radiographers should rene their technique in an eort to reduce the number of retakes and ultimately the amount of radiation exposure to their patients. is chapter Introductione radiographic examination is an integral component of formulating a diagnosis and treatment plan for the dental patient. It is of the utmost importance that the radiographic images of the patient’s oral structures be diagnostically acceptable. It is the dental professional’s responsibility to KEY TERMSbitewing projectionchair positioncollimator cuto (cone cutting)dimensional accuracydimensional distortiondouble exposureelongationexposure routineextension cone paralleling (XCP) techniquelm reversalforeshorteningfull-mouth survey (FMS)hemostathorizontal angulationlocalizing ringlong axislong cone techniqueocclusal planeoverexposureoverlappingpatient movementperiapical projectionpoint of entryreceptor positionright-angle techniquesagittal planeunderexposurevertical angulationvertical bitewings 81CHAPTER 9 Intraoral Radiographic Technique: The Paralleling Methodroot and 2 to 3 mm of surrounding periapical bone. is projection is necessary to diagnose normal or pathologic conditions of tooth crowns and root, bone, and tooth formation and eruption (Fig. 9.2).e bitewing projection can be taken only if there are opposing teeth to hold the receptor in position with their occluding surfaces. is projection shows the upper and lower teeth in occlusion in one image. Only the crowns and alveolar crest of the bone of adjacent teeth are seen. It is used for detecting interproximal decay, periodontal bone loss, recurrent decay under restorations, and faulty restorations (Fig. 9.3). Bitewing projections can be taken of the anterior teeth but are usually taken in the posterior regions. Proponents of the use of vertical bitewings point out that, in this position, more root is seen and thus can be more diagnostic for root caries, receding alveolar bone levels, and in pediatric patients to see the progress of the secondary dentition.e FMS shows all of the teeth in the mandible and maxilla, as well as the surrounding bone. Each tooth is shown at least twice in the survey; that is, the maxillary second premolar can be seen on the premolar periapical image and on the premolar bitewing projection. Some teeth may be seen in three or four views. is gives the diagnostician an opportunity to view the tooth from dierent radiographic angles, eliminating the possibility that an artifact could be mistaken for caries or other pathologic conditions.Pediatric Full-Mouth SurveyDepending on the child’s age and the size of the child’s mouth, the composition of the FMS may vary. A report of the Selection Criteria Panel recommends that only two bitewing images be taken for the asymptomatic clinically negative pediatric patient with closed posterior contacts. For asymptomatic and clinically negative pediatric patients with open posterior contacts, no radiographs are necessary.For patients up to 5 years old who are in need of an FMS, the operator should use the pediatric-size receptor #0 for anterior, posterior, and bitewing projections (Fig. 9.4). e FMS at this age entails 12 projections: three maxillary anterior projections, three mandibular anterior projections, four mandibular and maxillary molar projections, and two bitewing projections. Only one molar bitewing projection is taken on each side.In the 6-year-old to 9-year-old group, the pediatric receptor (#0) or narrow adult receptor (size #1) can be used for anterior projections, because the child’s arch shape at this age can still be very narrow. For posterior projections, adult size #2, narrow adult, or pediatric receptor (#0) is used, depending on the size of the arch. At this age, two posterior periapical projections in each quadrant are taken, because the 6-year molars have erupted and the dental arch has lengthened. One bitewing projection on each side is also used.After 9 years old, the full adult series is taken, with the narrow adult receptor being used where necessary. ese age discusses the types of intraoral radiographs available; the paralleling exposure technique; receptor-holding devices; and the appearance, cause, and remedy for various common exposure errors in dental radiography. Film-based and digital radiographic techniques are discussed here; the digital radiographic techniques are further discussed in Chapter 15.The Radiographic SurveyIntraoral radiography is a dental imaging technique uti-lized when the image receptor is placed inside the patient’s mouth and the source of radiation is positioned outside of the patient’s mouth. e x-ray prescription for intraoral radiographs is custom t to a patient’s dental health needs. e number and type of images exposed can vary depend-ing on the needs of the patient. e full-mouth intraoral radiographic survey is one option in choosing the neces-sary radiographs for a particular patient to complete the patient’s oral diagnosis. A dental examination or treatment plan cannot be considered complete without current or valid radiographs; in some cases, the full-mouth survey (FMS) is the radiographic procedure of choice. e FMS is a challenging procedure to perform correctly; it requires time and meticulous attention to detail. It bears with it the responsibility of exposing the patient to the least amount of ionizing radiation to obtain the maximum diagnostic yield. Unnecessary radiographs or those of poor quality that do not have diagnostic value do not serve the patient’s needs and only add to the patient’s radiation burden. Regardless of which member of the dental team takes the radiographs, the same quality standards are maintained for all dental professionals.e radiographic FMS is usually composed of 14 or more periapical projections and, where possible, four posterior bitewing projections (Fig. 9.1). e bitewing projections can be held vertically or horizontally. is text discusses a 14-periapical and a four-horizontal bitewing image technique. Some series of more than 14 periapical projec-tions include distal maxillary molar projections, vertical bitewings, anterior bitewings, and individual radiographs using #1 size narrow anterior projections of the six maxillary and four mandibular anterior teeth.e number of radiographs in an FMS can be modied to include extra or fewer projections, depending on the size of the patient’s mouth or tooth position. In all cases, the minimum number of images that satises the diagnostic requirements of an FMS should be used. Film mounts and digital templates are available in various combinations of numbers and sizes of receptors. e radiographic survey should not be determined by the lm mount or digital template available or by any other reason not related to dental health but strictly by the diagnostic needs of the patient. e recommended intraoral projections are listed in Table 9.1.A periapical projection shows the entire tooth from the incisal edge or the occlusal surface to the apex of the 82 CHAPTER 9 Intraoral Radiographic Technique: The Paralleling MethodA• Figure 9.1 A, A 19-image full-mouth survey (FMS). B, An 18-image FMS. guidelines are exible and depend on the growth and devel-opment of the child. As a rule, it is best to use the largest receptor size that the patient can accommodate comfortably (Fig. 9.5). Keep in mind that the extraoral panoramic image can also be used with pediatric dental patients, especially to evaluate eruption patterns and growth and development.Edentulous SeriesA radiographic examination can be performed even though the patient may be wholly or partially edentulous. e absence of teeth in an area of clinical examination does not preclude the possibility of retained roots, impacted teeth, cysts, or other occult pathologic conditions that may be present in the bone. e edentulous examination may use periapical projections, occlusal projections, or a panoramic radiograph. e intraoral edentulous series is usually composed of 13 periapical projections. e bitewing images are not taken, because there are no opposing teeth to support the bitewing receptor-holding device or bitewing tabs, and only one image is taken in the maxillary central, lateral, and canine regions (Fig. 9.6). In small edentulous mouths, a survey consisting of 11 projections may suce by use of only one mandibular periapical projection and 83CHAPTER 9 Intraoral Radiographic Technique: The Paralleling MethodMaxillary MandibularCentral and lateral incisors Central and lateral incisorsRight and left canines Right and left caninesRight and left premolars Right and left premolarsRight and left molars Right and left molarsBitewingRight and left premolarsRight and left molarsThe Recommended Projections of the Radiographic SurveyTABLE 9.1 • Figure 9.2 Anterior (A) and posterior (B) periapical radiographs. Note that the entire tooth and surrounding periapical bone are shown. B• Figure 9.3 A, Bitewing radiograph. Note that only the crowns, alveolar ridge, and a small part of the roots of opposing teeth are seen. B, Bite-wing tab for digital sensors. (Courtesy Dentsply Rinn, York, PA.)• Figure 9.4 Size #0 pediatric lm for anterior, posterior, and bitewing projections. extension of the premolar projection anteriorly to include the canine area.e receptors are positioned in the same way as in a regular dentulous series but with certain modications. e crest of the edentulous ridge replaces the occlusal plane of the teeth as the plane of orientation. e receptor is positioned either 18 inch above (for mandibular projec-tions) or 18 inch below the ridge (for maxillary projections). Because there are no teeth and there may be a great deal of ridge resorption, it may be dicult to parallel the long axis of the receptor with the long axis of the edentulous ridge. us, the receptor lies atter against the palate or in the oor of the mouth. In these cases, it may be possible to support the receptor with cotton rolls to achieve parallelism or, if necessary, to increase the vertical angulation and use the bisecting angle technique. e best guideline in the edentulous series is to adjust the vertical angulation so that the central ray is almost perpendicular to the receptor (similar to the angulation used for occlusal projections). Any slight foreshortening that may result will not aect the diagnosis of any intrabony conditions.ere are two possible alternatives for the edentulous periapical survey. e rst is a panoramic survey (Fig. 9.7). e second is the use of an occlusal projection (Fig. 9.8), the technique of which is discussed in Chapter 10. e entire maxillary and mandibular ridges usually can be seen on their respective occlusal projections. Both the panoramic and the occlusal are survey projections; if any suspicious areas are seen, a periapical projection of the area can be done to obtain better denition for formulating a denitive diagnosis.e criteria for judging whether a single radiograph or a FMS is diagnostically acceptable are listed in Box 9.1. 84 CHAPTER 9 Intraoral Radiographic Technique: The Paralleling Method• Figure 9.5 Pediatric full-mouth survey (FMS) of a 9-year-old patient. • Figure 9.6 A 13-image edentulous survey. • Figure 9.7 Edentulous panoramic survey. If a single radiograph does not meet these criteria and cannot provide diagnostic value, it must be retaken. In an FMS, those areas and structures that do not appear on the primary image may be seen on adjacent projections in the series. Although a technically perfect FMS is ideal, retakes should not be performed unless they are necessary for proper diagnosis.Quality Assurancee criteria for diagnostically acceptable radiographs (as shown in Box 9.1) should be used to evaluate radiographs taken by dentists and dental professionals as part of a quality assurance program. is can be accomplished either by self-evaluation and criticism of one’s own work or by peer review. In this manner, technical errors can be corrected and high-quality diagnostic radiographs will be produced. Quality assurance is discussed further in a later chapter.Paralleling Techniquee basic principles of the paralleling technique for intraoral periapical projections is that the receptor and the long axis of the tooth being radiographed must be parallel to each other, and the central ray of the x-ray beam must be directed perpendicular to both (see Fig. 3.13). To accomplish this 85CHAPTER 9 Intraoral Radiographic Technique: The Paralleling Method• Figure 9.8 A, Edentulous occlusal survey of maxilla. B, Edentulous occlusal survey of mandible. • BOX 9.1 Criteria for Intraoral Radiographs1. The radiograph should show proper denition and detail and a degree of density and contrast so that all structures can be delineated easily.2. The structures should not be distorted either by elongation or by foreshortening.3. The radiograph should show the teeth from the occlusal or incisal edges to 2 to 3 mm beyond their apices.4. In a full-mouth survey (FMS), the entire alveolar processes of the mandible and maxilla must be seen, as far distal as the tuberosity in the maxilla and the beginning of the ascending ramus in the mandible.5. All interproximal surfaces of the teeth should be seen without overlapping provided that the teeth are not overlapped in the mouth.6. The x-ray beam should be centered on the receptor so that there are no unexposed parts on the image (“collimator cutoff” or “cone cuts”).7. The radiograph should not be cracked or bent or have any other artifacts.8. The radiograph should be processed properly.parallelism, the object-receptor distance must be increased. is distance can be sizable in some areas, such as the maxil-lary molar projection, where the receptor may have to be held at the midline of the palate to achieve this parallelism.e increased object-receptor distance results in loss of image sharpness, which is a problem that can be compensated • Figure 9.9 Bisecting 8-inch target-receptor distance (FFD) technique and paralleling 16-inch extended-cone technique. Note superimposition of zygomatic arch on apices of maxillary molar in bisecting technique. (Courtesy DENTSPLY Rinn, Elgin, IL.)for by using an increased, 16-inch, target-receptor distance (or focal-lm distance [FFD]; Fig. 9.9).e paralleling technique has often been called the long cone technique. is terminology is not as accurate in con-temporary dentistry, in which the target-receptor distance may be from 12 to 16 inches because of a recessed target (in the x-ray tube head) rather than as a result of the length of the position-indicating device (PID). Other names for the paralleling technique are the extension cone paralleling (XCP) technique or right-angle technique, both of which stress two important principles of the technique.Advantages and Disadvantages of the Paralleling Technique Compared with the Bisecting Angle TechniqueWhen the paralleling and bisecting techniques are com-pared, the consensus is that dental professionals prefer the paralleling method as the technique of choice. e American Academy of Oral and Maxillofacial Radiology (AAOMR) states the following through its Parameters of Care Committee: “e paralleling technique should be used with its appropriate armamentarium, when possible, as it provides the most geometrically accurate image of the denti-tion.” e paralleling technique produces better diagnostic images, less exposure to critical organs (such as, the thyroid gland and the lens of the eye), a smaller exit dose, and easier standardization and execution than the bisecting technique. 86 CHAPTER 9 Intraoral Radiographic Technique: The Paralleling Methodcould assume the presence of adequate bone for restora-tions, xed splinting, and so forth, on the basis of distorted radiographic images.With the paralleling technique, it is possible to diagnose and evaluate caries and alveolar bone height accurately on all radiographs and not rely on the bitewing projections, as users of the bisecting technique do. It is interesting to note that bitewing projections in both techniques are paralleling projections due to the inherent parallel relationship between the receptor and the tooth in the bitewing radiographic technique.In the bisecting technique, the radiopaque image of the zygomatic arch is often superimposed on the apices of the maxillary molars, making diagnosis dicult if not impos-sible. is superimposition is understandable, because the point of entry of the central ray for molar projections is along the zygomatic arch.e paralleling technique produces no superimposition of the zygomatic arch, because the central ray, which is perpen-dicular to the long axis of the molars, enters below the level of the zygomatic arch. Also, in the paralleling technique, the vertical angulation of the primary beam is rarely more than plus or minus 10 degrees, compared with the vertical angulation of 40 to 50 degrees in the bisecting technique. e lack of extreme vertical angulation with the paralleling method reduces the exposure to the thyroid gland and the lens of the eye, because they no longer lie in the path of the primary beam. In addition, the 16-inch target-receptor distance (or FFD) used with the paralleling technique reduces the volume of tissue irradiated when com-pared with the recommended 8-inch target-receptor Advantages of the Paralleling Techniquee major advantage of the paralleling technique is that, when performed correctly, it forms an image with both linear and dimensional accuracy to support a more valid diagnosis. e key terms are dimensional accuracy and dimensional distortion.e bisecting technique, if used properly, correctly represents the teeth linearly but produces dimensional distortion. e bisecting technique can project the images and surrounding structures on the receptor in a true linear relationship without elongation or foreshortening. e teeth and bone, however, are three-dimensional objects; and although their overall length may be recorded accurately, the relationship of one part of the tooth to another is distorted dimensionally (Fig. 9.10). ose parts of the tooth that lie farthest from the receptor, such as the buccal plate of bone and buccal roots, are foreshortened; although their lingual linear counterparts are not. A classic clinical example consists of comparing the length of the buccal roots with that of palatal roots in maxillary rst molars. Clinicians who have used the bisecting technique for many years may come to believe that the buccal roots are much shorter than they really are because of dimensional distortions. One may argue that this may not be clinically important except in an initial endodontic measurement, but when this distortion is applied to periodontal evaluation of alveolar bone levels, the clinical importance becomes apparent (Fig. 9.11). In the bisecting technique, the image of the buccal bone level is guratively added to the palatal bone height to give a distorted image. A diagnosis and treatment plan BA• Figure 9.10 Radiographs of maxillary molar taken with bisecting technique (A) and the paralleling technique (B). (Courtesy DENTSPLY Rinn, Elgin, IL.)• Figure 9.11 Radiographs of the same area taken with the parallel-ing technique (A) and the bisecting technique (B). Note the difference in alveolar bone height, as indicated by arrows. 87CHAPTER 9 Intraoral Radiographic Technique: The Paralleling Methodsuch a way that the jaw can be radiographed correctly. Except when paralleling instruments are used, the occlusal plane of the jaw being radiographed must be parallel to the oor when it is in the open position.e patient should remove any nonxed prosthetic appliances from the mouth, as well as eyeglasses and facial jewelry (i.e., in the direct path of the primary beam, such as nose or lip rings). Failure to do this would cause a superimposed radiopaque error on the image. In the case of eyeglasses and facial jewelry, any metallic component will appear radiopaque and may be superimposed on any image in which they are worn. e patient should be draped with a lead apron and thyroid collar. is is done routinely for all patients, regardless of the number of projections taken. en, the operator turns on the x-ray machine. e infection control procedures outlined in Chapter 8 should be followed. When using lm packets, the unexposed and exposed lms can be placed in a cup and should be positioned outside of the operatory away from primary and scatter (secondary) radiation. Many diagnostic dental lms are fogged by secondary radiation and thus made unacceptable if left in the dental operatory when other images are being exposed.e desired number of receptors, as well as additional supplies, such as receptor-holding devices, should be brought near the operatory at this time. One of the more important general principles of taking intraoral radiographs is to have the positioned receptor in the patient’s mouth for as short a time as possible. is decreases the likelihood of gagging and patient movement. e desired exposure time on the machine always should be set before the receptor is placed in the patient’s mouth. Precious moments can be wasted in setting the time while the receptor is already in the patient’s mouth.While the exposure is being made from the required 6-foot distance, the operator should watch the patient. If the patient moves, the operator will be able to see the movement and avoid having to retake the image. A simple command to the patient (such as, “Please hold still”) can be helpful at this time. A well-designed oce permits observa-tion from behind a suitable barrier.After the exposure has been made, the operator removes the receptor from the patient’s mouth, dries o the saliva, and places it in the exposed receptor receptacle. Some denite order should be followed for a series of radiographs. Skipping from area to area without a set pattern often results in an omitted projection when utilizing a lm-based radiographic technique. A good place to start is with the maxillary central incisor projection; it is probably the easiest for the patient to tolerate. One should never start with the maxillary molar projection, because this is the projection most likely to excite the gag reex; once the reex is excited, the patient may gag on projections that normally could be tolerated. After starting with the maxillary central incisor projection, the maxillary canine, premolar, and molar are radiographed in that order. e opposite side of the maxilla is then radiographed. It is poor technique to radiograph distance (or FFD) used in the bisecting technique (see Fig. 6.10).e paralleling technique is easier to standardize than the bisecting technique, and serial comparison radiographs of the same area have greater validity. is is especially important in evaluating alveolar bone levels of periodontal patients at recall examinations.If a receptor-holding device with a localizing ring (i.e., XCP instruments) is used with the paralleling technique, the patient does not have to be positioned so that the occlusal plane of the jaw being radiographed is parallel to the oor. is is especially helpful in contour chairs or when patients are treated in the supine or semi-supine position. In these instances, it is dicult to position the patient with the occlusal plane parallel to the oor.Disadvantages of the Paralleling TechniqueOne of the objections most often raised about the paralleling technique is the diculty in placement and the degree of discomfort caused by the devices used to hold the receptor parallel to the long axis of the tooth. is may present some problems for patients with small mouths or large tori, children, and patients with low palatal vaults, but the more adept an operator becomes with the technique, the less these problems are a factor. In the pediatric patient, if it is impos-sible to position the receptor for the paralleling method, decrease the receptor size; and then if a backup strategy is needed, use the bisecting method. At least the time element is the same, and learning the paralleling technique is as easy as or easier than learning the bisecting technique, especially when using paralleling instruments (i.e., XCP instruments).Objections to the paralleling technique in the past focused on the “long, bulky” 16-inch PID that is used in this technique. e claim is that these PIDs were dicult to work with, especially in small operatories. is objection has no validity with the newer x-ray machines, with the extended target-receptor distance (or FFD) within the tube head as a result of a recessed target (see Fig. 3.10).Another supposed disadvantage of the paralleling tech-nique in the past was that with the 16-inch target-receptor distance (or FFD), longer exposure times are necessary, resulting in a greater chance of patient movement. With the use of faster-speed lm and digital receptors, this is no longer true. Previously, with the use of slower lm, the possibility of patient movement was greater.Exposure RoutineRegardless of which technique (paralleling or bisecting) is used, certain basic rules must be followed for the barrier technique, infection control preparation of the patient, and radiation hygiene. Operators should develop an exposure routine to avoid mistakes that necessitate the retaking of images. Retaking a radiograph because of operator error adds unnecessarily to the patient’s radiation burden.e patient should be seated comfortably in the chair, with the back well supported and the head positioned in 88 CHAPTER 9 Intraoral Radiographic Technique: The Paralleling MethodFilm Holderse use of receptor holders is strongly recommended for a variety of reasons, including avoiding the use of the patient’s (or operator’s) nger to hold the receptor. In the paral-leling technique, the receptor must be held in its proper position by one of a variety of receptor-holding devices all serving one purpose—to position the receptor parallel to the long axis of the tooth. Some examples of devices include hemostats, Stabes, XCPs, RAPDs, and other acceptable receptor holders (Fig. 9.12). e localizing rings on left canine, right canine, left premolar, and so forth. is necessitates moving the tube head constantly from one side of the patient to the other, which is time-consuming and can result in an omitted projection.e bitewing projections can be taken after the maxillary periapicals if the operator so chooses. It is suggested that the mandibular periapical projections should be taken in the same order as the maxillary projections. However, the ultimate choice of exposure sequence is the operator’s, as long as all of the prescribed radiographs are successfully taken with the patient’s comfort and time in mind.BDECAFG• Figure 9.12 Beam alignment devices. A, Rinn XCP instruments (blue: anterior; yellow: posterior; red: bite-wing; green: endodontics). B, Rinn XCP-ORA devices. C, Rinn Flip-Ray eliminates the need for multiple devices. D, Snap-A-Ray intraoral lm holder. E, Rinn Snap-A-Ray is color coded. F, Disposable Stabe bite block. G, Snap-a-Ray Bisecting option for sensor with arm and ring kit attached. (A-C, E-G Courtesy Dentsply Rinn, York, PA.) 89CHAPTER 9 Intraoral Radiographic Technique: The Paralleling Methodparalleling receptor-holding devices align the PID with the receptor in both the horizontal and vertical planes, helping reduce the incidence of collimator cuto (formerly known as cone cutting). e localizing rings are also a great aid with radiographic procedures performed in contour dental chairs. ese chairs can make it dicult to position the patient so that the occlusal plane is parallel to the oor. However, as long as the open-ended PID can be brought into at contact with the localizing ring, strict adherence to occlusal plane orientation is not necessary. Also, the relationship between the end of the PID and the ring can alert the operator to exposure errors before they get a chance to happen. For example, if there is spacing on the right or left of the ring, the operator should correct the horizontal angulation. In addition, if the spacing is on the top or bottom, the operator should correct the vertical angulation. Furthermore, some manufacturers have included notches on circular localizing rings to assist operators with proper placement of a rectangular PID.Receptor holders are either disposable (e.g., Styrofoam bite blocks [Stabes]) or non-disposable (e.g., XCP) and can be used for holding lms, digital sensors, or (in some cases) both lms and digital sensors. Non-disposable receptor holders must be sterilized and not just disinfected. As described in Chapter 8, the choice method of sterilization is steam autoclaving. Be aware that some receptor-holding devices have parts that are not considered autoclavable.Methode following six factors must be considered in any peri-apical projection: exposure time, chair position, receptor position and placement, point of entry of the beam, vertical angulation, and horizontal angulation.Exposure TimeExposure time is determined by the area being radio-graphed, receptor speed, kilovoltage, milliamperage, and target-receptor distance (or FFD). e type of time setting controls vary depending on the manufacturer and model of the radiographic unit. Some units have up and down arrows to control the desired increase or decrease in the time setting. is type of exposure time setting control system requires that operators know the appropriate time setting for each exposure that they are taking. is can be established when the unit is calibrated; then, each time setting for the respective area being exposed is listed and posted in the operatory for the radiographer’s use. It is recommended to post such a chart near the machine so that exposure times need not be committed to memory. For a majority of the newer-model x-ray units, the time can be set automatically simply by choosing an icon representing the area of exposure on the control panel (see Fig. 2.6). In any event, the timer should be set before the receptor is placed in the patient’s mouth.• Figure 9.13 Proper patient position for maxillary periapical radiographs and bitewing projections. Note that the occlusal plane of maxillary teeth, or the ala-tragus line, is parallel to the oor. • Figure 9.14 Proper patient position for mandibular periapical radiographs. Note that when the mouth is open, the occlusal plane of lower teeth is parallel to the oor. Chair Position: Occlusal and Sagittal Plane Orientationse patient is positioned so that when the mouth is open and the receptor is in position, the occlusal plane of the jaw being radiographed is parallel to the oor. In the maxilla, this plane corresponds to the ala-tragus line on the face. When the maxilla is radiographed, the headrest is positioned high on the back of the patient’s head, helping to position the chin downward toward the oor (Fig. 9.13). When the mandible is radiographed, the headrest is placed below the occipital protuberance (lower rear part of the human skull) in what would be the normal dental chair position (Fig. 9.14). For both upper and lower jaws, the patient’s head is positioned so that the sagittal plane is perpendicular to the oor (Fig. 9.15). Note that when using paralleling 90 CHAPTER 9 Intraoral Radiographic Technique: The Paralleling Methodreceptor-holding devices with an aiming bar and localizing ring, the position of the patient’s head is not as important, such as in the case in which the holding device does not have these components.Receptor Positione receptor is held with its long dimension vertical for anterior projections and horizontal for posterior periapical and bitewing projections (unless vertical bitewings are being exposed). e edge of the receptor always should extend evenly either 18 inch below (maxillary) or 18 inch above (mandibular) the occlusal plane. is receptor position en-sures that adequate surface area of the receptor remains at the apical areas and at the incisal or occlusal surfaces to record the image in its entirety. If a lm packet is being used as the receptor of choice, it should be placed in the patient’s mouth so that the mounting orientation button is toward the occlusal surface (Fig. 9.16). is helps in mounting and precludes the possibility of the dots being superimposed over the apex of a tooth, possibly creating an artifact that resembles a periapical radiolucency. One useful way of re-membering the correct positioning of the lm packet in the holding device is by use of the slogan “dot in the slot and the white toward me.” is ensures that the operator prevents having the dot superimposed over the apex of the root and reducing the incidence of reversed lms by ensuring that the front or white side of the lm packet is toward the tooth and not reversed in the patient’s mouth. Whichever recep-tor is being used, it is held in position by the patient with a receptor-holding device as opposed to the unacceptable option of the patient holding the receptor with their nger.Point of Entrye point of entry is the anatomic position on the patient’s face at which the central ray of the x-ray beam is aimed. It corresponds to the middle of the receptor in the patient’s • Figure 9.17 Vertical angulation is measured in degrees on the outside of the tubehead. (Courtesy of Dr. Kamran Azmoudeh, Santa Rosa, CA.)mouth. e localizing ring, when used, determines the point of entry by its predetermined relationship to the receptor. e use of rectangular collimation does not change this relationship between the localizing ring, PID, and point of entry.Vertical AngulationIn the paralleling technique, the vertical angulation is set to aim the central ray perpendicular to the receptor. In the bisecting technique (see Chapter 10), the vertical angula-tion is determined by the bisection of the angle. Vertical angulation of the x-ray beam in the paralleling technique is set by ensuring that the central ray is perpendicular to the tooth and the receptor (Fig. 9.17). When using a paral-leling instrument with a localizing ring and aiming bar, the vertical angulation can be set by making sure that the • Figure 9.15 Proper patient position for orientation of sagittal plane of head perpendicular to the oor. • Figure 9.16 Placement of receptor-holding device in patient’s mouth by operator. Note that the correct side of lm packet faces the tube head and the mounting dot is toward the occlusal surface. 91CHAPTER 9 Intraoral Radiographic Technique: The Paralleling MethodPROCEDURE 9.1 THE FULL-MOUTH SURVEYMaxillary Central Incisors (Fig. 9.18)Chair Position. The maxillary occlusal plane is positioned parallel to the oor and the sagittal plane of the patient’s face is perpendicular to the oor.*When using paralleling receptor-holding devices with an aiming bar and localizing ring, the position of the patient’s head is not as important as in the case in which the holding device does not have these components.Receptor Position. The receptor is held vertically and positioned in the palate away from the lingual surfaces of the teeth so that the long axis of the receptor is parallel to the long axis of the teeth. The center of the receptor is positioned at the junction between the central incisors. The receptor is placed in the palate so that the entire lengths of the teeth are shown. This parallel placement of the receptor is held in position by one of the devices previously mentioned.Point of Entry. The central ray is directed at the center of the receptor.*If a localizing ring is used, the open face of the position-indicating device (PID) contacts the ring; this determines the point of entry of the x-ray beam.Vertical Angulation. The central ray is perpendicular to the tooth and receptor in the vertical plane.ContinuedCA• Figure 9.18 Maxillary central and lateral incisors. A, Receptor holder and position-indicating device (PID). B, Radiograph. C, Diagram. Text continued on p. 104NOTEThe recommended paralleling technique procedure box is very detailed in terms of the preferred chair position, receptor position, point of entry, vertical angulation, and horizontal angulation. However, note the italicized recommendations for use of the extension cone paralleling (XCP) holding device for each projection listed, because the use of these instruments simplies the exposure technique.PID is parallel to the aiming bar and the open end of the rectangular or circular collimator (PID) is in equidistant close proximity to the localizing ring.Horizontal AngulationTo achieve horizontal angulation, the central ray is directed so that it is perpendicular to the receptor in the horizontal plane. e central ray is directed through the interproximal spaces to avoid overlapping of structures. When using a holding device with a localizing ring, the operator should make sure that there is no uneven space between the end of the PID and the localizing ring on either the right or left side of the ring and PID. Furthermore, to avoid horizontal overlap, the dental professional should place the receptor parallel to the teeth in both the horizontal plane and vertical plane. 92 CHAPTER 9 Intraoral Radiographic Technique: The Paralleling MethodPROCEDURE 9.1 THE FULL-MOUTH SURVEY—cont’d*When using a paralleling instrument with a localizing ring and aiming bar, the vertical angulation can be set by making sure that the PID is parallel to the aiming bar and the open end of the rectangular or circular collimator (PID) is in equidistant close proximity to the localizing ring.Horizontal Angulation. The central ray is perpendicular to the tooth and receptor in the horizontal plane (Fig. 9.19).*When using a holding device with a localizing ring, the operator should make sure that there is no uneven space between the end of the PID and the localizing ring on either the right or left side of the ring and PID.*To avoid horizontal overlap, the dental professional should place the receptor parallel to the teeth in both the vertical and horizontal planes.Maxillary Canines (Fig. 9.20)Chair Position. The maxillary occlusal plane is parallel to the oor, and the sagittal plane of the patient’s face is perpendicular to the oor.*When using paralleling receptor-holding devices with an aiming bar and localizing ring, the position of the patient’s head is not as important as in the case in which the holding device does not have these components.Receptor Position. The receptor is held vertically, away from the lingual surface of the canine and parallel to its long axis. The center of the receptor is behind and centered on the canine and positioned in the palate so that the entire length of the canine is shown. The receptor is held in position by a holding device.HELPFUL HINTWhen using a localizing device, make sure that it is as close to the patient’s face without touching as possible. This prevents the ring position away from the receptor thereby increasing the target-receptor distance (or focal-lm distance [FFD]), which would result in a thin (light) image exhibiting an application of the inverse square law.CA• Figure 9.20 Maxillary canine. A, Receptor-holding device and position-indicating device (PID). B, Radiograph. C, Diagram. A• Figure 9.19 Right and left maxillary central and lateral incisors. A, Receptor-holding device and position-indicating device (PID). B, Radiograph. 93CHAPTER 9 Intraoral Radiographic Technique: The Paralleling MethodPROCEDURE 9.1 THE FULL-MOUTH SURVEY—cont’dPoint of Entry. The central ray is directed at the center of the receptor or, if a localizing ring is used, it is brought into at contact with the open-ended PID.*If a localizing ring is used, the open face of the PID contacts the ring; this determines the point of entry of the x-ray beam.Vertical Angulation. The central ray is perpendicular to the receptor in the vertical plane.*When using a paralleling instrument with a localizing ring and aiming bar, the vertical angulation can be set by making sure that the PID is parallel to the aiming bar and the open end of the rectangular or circular collimator (PID) is in equidistant close proximity to the localizing ring.Horizontal Angulation. The central ray is perpendicular to the receptor in the horizontal plane.*When using a holding device with a localizing ring, the operator should make sure that there is no uneven space between the end of the PID and the localizing ring on either the right or left side of the ring and PID.*To avoid horizontal overlap, the dental professional should place the receptor parallel to the teeth in both the vertical and horizontal planes.Maxillary Premolars (Fig. 9.21)Chair Position. The maxillary occlusal plane is parallel to the oor, and the sagittal plane of the patient’s face is perpendicular to the oor.*When using paralleling receptor-holding devices with an aiming bar and localizing ring, the position of the patient’s head is not as important as in the case in which the holding device does not have these components.Receptor Position. The receptor is held horizontally and positioned away from the lingual surfaces of the premolar so that its long axis is parallel to the long axis of the premolar. In the maxillary premolar and molar region, the receptor position may be in the middle of the palate. The center of the receptor aligns with the second premolar. The receptor is positioned in the palate so that the entire length of the teeth is shown on the receptor. The receptor is held in position by a holding device.Point of Entry. The central ray is directed at the center of the receptor or, if a localizing ring is used, it is brought into at contact with the open-ended PID.*If a localizing ring is used, the open face of the PID contacts the ring; this determines the point of entry of the x-ray beam.Vertical Angulation. The central ray is perpendicular to the receptor in the vertical plane.*When using a paralleling instrument with a localizing ring and aiming bar, the vertical angulation can be set by making sure that the PID is parallel to the aiming bar and the open end of the rectangular or circular collimator (PID) is in equidistant close proximity to the localizing ring.Horizontal Angulation. The central ray is perpendicular to the receptor in the horizontal plane.*When using a holding device with a localizing ring, the operator should make sure that there is no uneven space between the end of the PID and the localizing ring on either the right or left side of the ring and PID.*To avoid horizontal overlap, the dental professional should place the receptor parallel to the teeth in both the vertical and horizontal planes.ContinuedHELPFUL HINTReceptor placement of the maxillary canine may be very difcult. In order to achieve parallelism, the receptor may have to be positioned across the arch, resulting in an increased object-receptor distance. Also, the operator should make sure that if a lm packet is used, it is curved away from the source of radiation to accommodate the palatal arch. If the lm is curved toward the radiation, the lead foil backing will be superimposed over the superior aspect of the radiograph. Furthermore, the operator must make sure that the lm does not come out of the holder when it contacts the palate so as not to cut off the incisal edge.AC• Figure 9.21 Maxillary premolars. A, Receptor-holding device and position-indicating device (PID). B, Radiograph. C, Diagram. HELPFUL HINTMake sure as the arch starts to turn that the receptor remains parallel to the long axis, as well as the horizontal axis of the premolar teeth being radiographed. 94 CHAPTER 9 Intraoral Radiographic Technique: The Paralleling MethodMaxillary Molars (Fig. 9.22)Chair Position. The maxillary occlusal plane is positioned parallel to the oor, and the sagittal plane of the patient’s face is perpendicular to the oor.*When using paralleling receptor-holding devices with an aiming bar and localizing ring, the position of the patient’s head is not as important as in the case in which the holding device does not have these components.Receptor Position. The receptor is held horizontally and positioned away from the lingual surfaces of the molars so that the long axis of the receptor lies parallel to the long axes of the molars. The center of the receptor aligns with the middle of the second molar and the receptor is positioned in the palate so that the entire length of the teeth is shown. The receptor is held in position by a holding device.Point of Entry. The central ray is directed at the center of the receptor or the localizing ring is brought into at contact with the open-ended PID.*If a localizing ring is used, the open face of the PID contacts the ring; this determines the point of entry of the x-ray beam.Vertical Angulation. The central ray is perpendicular to the receptor in the vertical plane.*When using a paralleling instrument with a localizing ring and aiming bar, the vertical angulation can be set by making sure that the PID is parallel to the aiming bar and the open end of the rectangular or circular collimator (PID) is in equidistant close proximity to the localizing ring.Horizontal Angulation. The central ray is perpendicular to the receptor in the horizontal plane.*When using a holding device with a localizing ring, the operator should make sure that there is no uneven space between the end of the PID and the localizing ring on either the right or left side of the ring and PID.*To avoid horizontal overlap, the dental professional should place the receptor parallel to the teeth in both the vertical and horizontal planes.Bitewing ProjectionsThe technique for bitewing projections is the same in the paralleling and bisecting-angle techniques except for the use of the 16-inch target-receptor distance (or FFD) used in the paralleling as opposed to the bisecting technique. Bitewing projections are always paralleled projections, no matter what technique is used for the periapical projections. The receptor is positioned by the bite piece parallel to the crowns of both upper and lower teeth, and the central ray is directed perpendicular to the receptor.Premolar and Molar Bitewing Projections (Fig. 9.23)Chair Position. The maxillary occlusal plane is positioned parallel to the oor, and the sagittal plane of the patient’s face is perpendicular to the oor.*When using paralleling receptor-holding devices with an aiming bar and localizing ring, the position of the patient’s head is not as important as in the case in which the holding device does not have these components.Film Position. When the premolars are radiographed, the bitewing holder is placed on the occlusal surface of the second mandibular premolar. This depresses the receptor into the oor of the mouth. While the operator holds the bite piece down with one’s thumb and forenger, the patient is instructed to bite on the bite piece. The operator should be sure that the patient is biting on the back teeth and not just bringing the incisors together. If the back teeth are not moved to centric occlusion, the receptor is not secure; consequently, it may move and not be oriented correctly. The procedure for radiographing the molars is the same as that previously mentioned for the premolars except that the bite piece is centered over the occlusal surface of the second molar.Point of Entry. The central ray is directed at the bitewing bite piece, which is held in position by the patient’s teeth.*If a lm holder with a localizing ring and aiming arm are used, the open end of the PID is placed against the ring.PROCEDURE 9.1 THE FULL-MOUTH SURVEY—cont’dCA• Figure 9.22 Maxillary molars. A, Receptor-holding device and position-indicating device (PID). B, Radiograph. C, Diagram. HELPFUL HINTIf you are not using a localizing ring, you can offset the receptor by placing the receptor distally in the bite piece and by having the center of the bite piece over the rst molar.If the mouth is unusually small or the teeth crowded, it may be necessary to use a smaller receptor, such as #0 or #1. Remember that it is the anatomic variants of the teeth and bone that dictate the receptor size that should be used.If the operator is having difculty placing the receptor to include the third molar region, the operator can place the receptor on the rst molar when the mouth is fully open and ask the patient to close slightly, then slide the receptor onto the second molar before nally securing the receptor. 95CHAPTER 9 Intraoral Radiographic Technique: The Paralleling MethodPROCEDURE 9.1 THE FULL-MOUTH SURVEY—cont’dVertical Angulation. The central ray is perpendicular to the receptor in the horizontal plane.*When using a paralleling instrument with a localizing ring and aiming bar, the vertical angulation can be set by making sure that the PID is parallel to the aiming bar and the open end of the rectangular or circular collimator (PID) is in equidistant close proximity to the localizing ring.Horizontal Angulation. Horizontal angulation is a critical factor in the bitewing projection; utmost attention should be paid to horizontal positioning. An overlapping image on the bitewing projection renders the image useless. The central ray should be perpendicular to the receptor in the horizontal plane and should go through the contact points of the premolars or molars.*When using a holding device with a localizing ring, the operator should make sure that there is no uneven space between the end of the PID and the localizing ring on either the right or left side of the ring and PID.*To avoid horizontal overlap, the dental professional should place the receptor parallel to the teeth in both the vertical and horizontal planes.Vertical Bitewings (Fig. 9.24)Vertical bitewings are used when the desired area would not be seen on the image with the usual bitewing placement; this could be the case in advanced bone loss, root caries, or tooth eruption. The receptor is placed in the patient’s mouth with the longer side vertically positioned. All other exposure factors remain the same. It is necessary to use the paste-on tabs and not the loops or the XCP vertical bitewing instruments with this technique. The vertical bitewing can be used in a posterior or anterior region. There are paralleling instruments available in the contemporary market that now include vertical bitewing attachments (i.e., XCP vertical bitewing instrument).Mandibular Incisors (Fig. 9.25)Chair Position. The patient is positioned so that when the mouth is open the mandibular occlusal plane is parallel to the oor and the sagittal plane of the patient’s face is perpendicular to the oor.*When using paralleling receptor-holding devices with an aiming bar and localizing ring, the position of the patient’s head is not as important as in the case in which the holding device does not have these components.Receptor Position. The receptor is held vertically and positioned away from the lingual surfaces of the incisors so that the long axis of the receptor is parallel to the long axes of the incisors. The center of the receptor is positioned at the midline between the two mandibular central incisors so that all four incisors appear on the image. The receptor is depressed into the oor of the mouth so that the entire length of the teeth is shown. It may be necessary to displace the tongue distally and to gently depress the oor of the mouth to achieve this. The receptor is held in position by a holding device.Point of Entry. The central ray is directed at the center of the receptor.*The localizing ring is brought into at contact with the open-ended PID.Vertical Angulation. The central ray is perpendicular to the receptor in the vertical plane.*When using a paralleling instrument with a localizing ring and aiming bar, the vertical angulation can be set by making sure that the PID is parallel to the aiming bar and the open end of the rectangular or circular collimator (PID) is in equidistant close proximity to the localizing ring.FCBA• Figure 9.23 Bitewing projection. A, Receptor-holding device being placed on occlusal surfaces of lower teeth. B, Patient bites on bite block. C, Position-indicating device (PID) positioned. D, Radiograph of premolar area. E, Radiograph of molar area. F, Diagram. ContinuedHELPFUL HINTWhen taking bitewings without the use of a localizing ring, it helps to align the beam by having your index nger touching the bitewing tab in the buccal sulcus of the patient’s mouth, using your nger as an extension of the position-indicating device (PID). You can also ask the patient to smile so that the tab is revealed. 96 CHAPTER 9 Intraoral Radiographic Technique: The Paralleling MethodPROCEDURE 9.1 THE FULL-MOUTH SURVEY—cont’dHorizontal Angulation. The central ray is perpendicular to the receptor in the horizontal plane.Mandibular Canines (Fig. 9.26)Chair Position. The patient is positioned so that when the mouth is open the mandibular occlusal plane is parallel to the oor and the sagittal plane of the patient’s face is perpendicular to the oor.*When using paralleling receptor-holding devices with an aiming bar and localizing ring, the position of the patient’s head is not as important as in the case in which the holding device does not have these components.Receptor Position. The receptor is held vertically and positioned away from the lingual surface of the canine so that its long axis is parallel to that of the canine. The receptor is positioned so that the canine is in the center of the receptor. The receptor is depressed into the oor of the mouth so that the entire length of the tooth is shown on the image. The receptor is held in position by a holding device.Point of Entry. The central ray is directed at the center of the receptor or the localizing ring is brought into at contact with the open-ended PID.Vertical Angulation. The central ray is perpendicular to the receptor in the vertical plane.CA• Figure 9.24 Vertical bitewing. A, Posterior receptor position. B, Posterior radiograph. C, Anterior projection position. D, Anterior radiograph. HELPFUL HINTWhen taking this projection, remember that in order to achieve parallelism between the teeth and the receptor in some cases it may be necessary to position the receptor far back in the oor of the mouth at the level of the molars. You may also start out with the receptor on an angle and then bring the receptor into a parallel position slowly with the closure of the mandible. The operator may also place an opened gauze pad under the receptor to prevent it from irritating the oor of the mouth. 97CHAPTER 9 Intraoral Radiographic Technique: The Paralleling MethodPROCEDURE 9.1 THE FULL-MOUTH SURVEY—cont’d*When using a paralleling instrument with a localizing ring and aiming bar, the vertical angulation can be set by making sure that the PID is parallel to the aiming bar and the open end of the rectangular or circular collimator (PID) is in equidistant close proximity to the localizing ring.Horizontal Angulation. The central ray is perpendicular to the receptor in the horizontal plane.*When using a holding device with a localizing ring, the operator should make sure that there is no uneven space between the end of the PID and the localizing ring on either the right or left side of the ring and PID.* To avoid horizontal overlap, the dental professional should place the receptor parallel to the teeth in both the vertical and horizontal planes.Mandibular Premolars (Fig. 9.27)Chair Position. The patient is positioned so that when the mouth is open the mandibular occlusal plane is parallel to the oor and the sagittal plane of the patient’s face is perpendicular to the oor.ContinuedCA• Figure 9.25 Mandibular incisors. A, Receptor-holding device and position-indicating device (PID). B, Radiograph. C, Diagram. CA• Figure 9.26 Mandibular canine. A, Receptor-holding device and position-indicating device (PID). B, Radiograph. C, Diagram. HELPFUL HINTBe sure that the receptor is placed below and not on top of the tongue, because it is a muscle and sometimes very difcult to displace. As it is said, “In a war with the tongue, the tongue always wins.” 98 CHAPTER 9 Intraoral Radiographic Technique: The Paralleling MethodPROCEDURE 9.1 THE FULL-MOUTH SURVEY—cont’d*When using paralleling receptor-holding devices with an aiming bar and localizing ring, the position of the patient’s head is not as important as in the case in which the holding device does not have these components.Receptor Position. The receptor is held horizontally and positioned so that it is parallel to the long axis of the premolar. The object-target distance in both the mandibular premolar and molar regions is almost minimal, because the anatomy allows the receptor to be positioned very close to the tooth and still be parallel. The receptor is centered on the center of the second premolar. The receptor is depressed into the oor of the mouth so that the entire length of the teeth shows on the image. The receptor is held in position by a holding device.Point of Entry. The central ray is directed at the center of the receptor, or if a localizing ring is used, it is brought into at contact with the open-ended PID.Vertical Angulation. The central ray is directed perpendicular to the receptor in the vertical plane.Horizontal Angulation. The central ray is perpendicular to the receptor in the horizontal plane.Mandibular Molars (Fig. 9.28)Chair Position. The patient is positioned so that when the mouth is open the mandibular occlusal plane is parallel to the oor, and the sagittal plane of the patient’s face is perpendicular to the oor.Receptor Position. The receptor is held horizontally and positioned lingually to the molar so that the long axis of the receptor is parallel to the long axes of the molars. The receptor is centered behind the second molar and depressed into the oor of the mouth so that the entire length of the teeth appears on the lm. The packet is held in position by a holding device.Point of Entry. The central ray is directed at the center of the receptor or, if a localizing ring is used, it is brought into at contact with the open-ended PID.Vertical Angulation. The central ray is directed perpendicular to the receptor in the vertical plane.*When using a paralleling instrument with a localizing ring and aiming bar, the vertical angulation can be set by making sure that the PID is parallel to the aiming bar and the open end of the rectangular or circular collimator (PID) is in equidistant close proximity to the localizing ring.Horizontal Angulation. The central ray is perpendicular to the receptor in the horizontal plane.*When using a holding device with a localizing ring, the operator should make sure that there is no uneven space between the end of the PID and the localizing ring on either the right or left side of the ring and PID.CA• Figure 9.27 Mandibular premolar. A, Receptor-holding device and position-indicating device (PID). B, Radiograph. C, Diagram. HELPFUL HINTIf a lm packet is being used as the receptor in this instance, in a small mouth, it may be helpful to roll (not bend) the lower anterior corner of the lm packet to ensure the patient’s comfort.CA• Figure 9.28 Mandibular molars. A, Receptor-holding device and position-indicating device (PID). B, Radiograph. C, Diagram 99CHAPTER 9 Intraoral Radiographic Technique: The Paralleling MethodPROCEDURE 9.1 THE FULL-MOUTH SURVEY—cont’d*To avoid horizontal overlap, the dental professional should place the receptor parallel to the teeth in both the vertical and horizontal plane.Common Dental Radiographic Exposure ErrorsNote: Refer to the Appendix for a detailed description of each of the following exposure errors.All of the errors mentioned and illustrated in this chapter are also possible with the bisecting technique, but the incidence differs. Although elongation and foreshortening are the most common bisecting errors, they are not as common in the paralleling technique. The most common error in the paralleling technique, even with the use of positioning devices, is in receptor placement. If the receptor and holder are not placed correctly in the patient’s mouth, the paralleling technique does not work. The most common error is not placing the receptor deep enough in the oor of the mouth or high enough in the palate, thus cutting off the apices of the teeth as a result of inadequate closure.With the use of the localizing ring, which is aligned with the center of the receptor, collimator cutoff (formerly known as cone cutting) can be practically eliminated.Occlusal plane and sagittal plane orientation of the patient’s head is not important if the localizing ring on the receptor-holding device is used, as long as the open end of the PID is brought into at contact with the localizing ring.Horizontal overlapping of the images also is eliminated with the proper use of the positioning device and localizing ring and the correct parallel placement of the receptor to the teeth in the horizontal plane.The rest of the errors mentioned in this chapter (i.e., lm reversal, overbending, crescent marks, overexposing and underexposing, double exposure, and failure to remove dental appliances) are all possible with the bisecting technique and their remedies are the same. However, lm reversal, overbending of the lm packet, overexposing and underexposing, and double exposure are errors that could occur with conventional (lm-based) radiography but are not likely to occur with digital radiography.An unexposed area on the radiograph occurs when the x-ray beam is not centered on the receptor. This is called collimator cutoff (formerly known as cone cutting; Fig. 9.29) and is caused by improper alignment of the x-ray beam and the receptor. Collimator cutoff can occur with both conventional and digital radiography.Remedy. The central ray of the x-ray beam should be aligned carefully with the center of the receptor. With circular collimation, the aperture of the diaphragm allows for a beam diameter, measured at the face, of 234 inches (2.75 inches; 7 cm). Size #2 adult lm is 114 × 158 inches, which leaves almost 14- to 12-inch leeway for human error in all directions. It is not sufcient to simply identify collimator cutoff; it should be analyzed to pinpoint the error and thus remedy it accordingly. For example, if it is always the distal part of a radiograph in a projection that is cut off, then the point of entry must be moved mesially. The localizing ring on a paralleling receptor-holding device aligns the beam and the receptor and aids in eliminating collimator cutoff with both circular and rectangular collimation.Film reversal (Fig. 9.30). Film reversal was formerly referred to as the herringbone effect, because the herringbone pattern that was embossed on the lead foil backing was transferred to the processed reversed radiograph. The herringbone, light (thin) image results from placing the lm packet backward in the patient’s mouth. The x-rays are attenuated in a pattern by the lead foil before striking the lm. The geometric pattern embossed by the lead foil backing distinguishes this light radiograph from other underexposure errors. The original geometric pattern was that of a herringbone; the name has survived even though the present pattern now resembles tiny adjacent boxes, a checkerboard, or even tire tracks. Because of the nature of this error, it can ContinuedHELPFUL HINTWhen positioning the receptor, make sure that the middle of the receptor is aligned with the middle of the second molar.B• Figure 9.29 A, Collimator cutoff (cone cutting). Central ray positioned too far distal. B, Diagram of collimator cutoff (“cone cutting”). Central ray positioned too far mesial. C, Cone cutting with rectangular collimation. 100 CHAPTER 9 Intraoral Radiographic Technique: The Paralleling MethodPROCEDURE 9.1 THE FULL-MOUTH SURVEY—cont’donly occur with conventional, lm-based radiography and does not occur with digital radiography.Remedy. The front and the back of the lm packet should be identied. Some manufacturers color-code or change the texture of the back of the lm packet to distinguish the front side from the back side of the lm packet. Operators should develop the habit of looking for these aids.Poor receptor placement (Fig. 9.31). The receptor has been poorly positioned if the whole tooth does not show on the image. The receptor is not sufciently placed to record the apex or biting surface of the tooth or teeth being radiographed or the tooth that should be centered is not. Poor receptor placement also occurs if the patient does not bite on both sides of the biting surface of the receptor holder. This error is known as inadequate closure. Furthermore, if the receptor is not positioned correctly in the patient’s mouth and does not show all of the desired teeth and surrounding structures, the error exhibited is also attributed to poor receptor placement. Poor receptor placement can occur with both conventional (lm-based) and digital radiography.Remedy. Only 18 inch of the receptor should project above or below the occlusal or incisal edges of the teeth. Also, the patient should adequately close on both sides of the bite piece. In addition, the receptor should be positioned correctly so that the image includes the desired teeth and their surrounding structures.Overlapping (Figs. 9.32 and 9.33). Overlapping of the images of the teeth results if the central ray is not perpendicular to the receptor and the teeth in the horizontal plane. Another cause of horizontal overlap is when the receptor is not placed parallel to the teeth in the horizontal plane. Horizontal overlap can occur with both conventional (lm-based) and digital radiography.Remedy. Make sure that the central ray is perpendicular to the receptor in the horizontal plane. This ensures that the central ray is directed straight through the contacts instead of crossing the contacts diagonally and causing overlapping of the interproximal surfaces of the teeth. When using a holding device with a localizing ring (i.e., XCP), the operator should make sure that there is no uneven space between the end of the PID and the localizing ring on either the right or left side of the ring and PID. If the receptor is placed parallel to the teeth, the localizing ring aligns the beam perpendicular to the receptor.Crescent marks and bent lms (Figs. 9.34 and 9.35). Black crescent-shaped marks or black marks from overbending the lm packet can be caused by excessive bending or excessive manipulation of the lm packet, which cracks the emulsion. These marks show on the lm after it is processed. In addition, if the lm packet is bent but does not crack the emulsion, the tooth appears as if it had been • Figure 9.30 Film reversal. Film packet placed in mouth with the wrong side toward the tube. B• Figure 9.31 A, Nondiagnostic image caused by poor lm packet placement. Note that apices of teeth are not seen. B, Poor lm place-ment. Note how much lm is visible above occlusal plane of tooth. • Figure 9.32 Overlapped images. Central rayCentral rayAB• Figure 9.33 Proper (A) and improper (B) horizontal angulation of x-ray beam. 101CHAPTER 9 Intraoral Radiographic Technique: The Paralleling MethodPROCEDURE 9.1 THE FULL-MOUTH SURVEY—cont’dstretched on the resultant image. Because of the nature of this error, it can only occur with conventional, lm-based radiography and does not occur with digital radiography.Remedy. Films can be made more pliable by rolling them slightly against one’s index nger, which also may allow them to t better in the patient’s mouth. Films should not be bent to adapt to anatomic surfaces; they should be gently shaped or curved to conform to the arch. X-rays travel in straight lines; they do not turn corners to expose bent lms.Light lms (Fig. 9.36). Light (thin) lms without adequate density can result from underexposure or underdevelopment assuming that an improper time setting has been used. If less exposure time than is needed is set, the dental structures are not adequately penetrated, and the lm does not differentiate structures of different densities. Also, the operator should avoid removing one’s nger from the exposure button prematurely, because this can cause an underexposed lm as well. Another radiographer’s error that can cause underexposure is unwittingly increasing the target-receptor distance (or FFD) by failing to bring the open end of the PID close to the patient’s face. The exposure times are calculated for a target-receptor distance (or FFD) that assumes a PID placement that is as close to the face as possible. If the PID is carelessly positioned away from the face, the inverse square law intensies the error, not just by the increased distance but by the square of that distance (Fig. 9.37).Light or thin images generally occur with the use of conventional lm-based radiography. Although it is possible to underexpose a digital image, the digital system has tools for rectifying this error. The resultant image can be altered by adjusting the contrast of the digital image before the image is saved.Remedy. For preventing underexposure, the proper time settings on the machine should be set before an exposure is made. Underexposed lms can also occur as a result of improper kilovoltage and milliamperage settings. However, the newer dental x-ray units have preset kilovoltage and milliamperage settings; thus, they currently are not Continued• Figure 9.34 Black line caused by cracking of lm emulsion. • Figure 9.35 Result of overbending lm packet. Note upper-right corner. • Figure 9.36 Underexposed radiograph. • Figure 9.37 Light lm can be caused by increased focal-lm distance (FFD) without compensatory increase in exposure time. Note distance between the patient’s face and position-indicating device (PID) in both photos. 102 CHAPTER 9 Intraoral Radiographic Technique: The Paralleling MethodPROCEDURE 9.1 THE FULL-MOUTH SURVEY—cont’dthe cause of an underexposed lm. For a discussion of underdevelopment, see Chapter 11.Dark lms (Fig. 9.38). Dark (dense) lms are the result of overexposure or overdevelopment, the opposites of the causes of light lms. The predetermined length of the target-receptor distance (or FFD) with a recessed target or the predetermined length of the PID (if the target is not recessed) prevents the possibility of a decreased target-receptor distance (or FFD) as the cause for an overexposed lm. However, if the operator sets the exposure time higher than is needed for a particular projection, an overexposed lm can be produced. If a lm is over penetrated, it is black and no dental structures show or they are difcult to differentiate.Dark or dense images generally occur with the use of conventional, lm-based radiography. Although it is possible to overexpose a digital image, the digital system has tools for rectifying this error. The resultant image can be altered by adjusting the contrast of the digital image before the image is saved.Remedy. To avoid overexposure, operators should check all settings on the control panel before taking an exposure. Overexposed lms can also occur as a result of improper kilovoltage and milliamperage settings. However, the newer dental x-ray units have preset kilovoltage and milliamperage settings; thus, they currently are not the cause of an overexposed lm. For a discussion of overdevelopment, see Chapter 11.Double exposure (Fig. 9.39). A double exposure results from using the same lm packet twice. This is a careless error and indicates lack of attention to detail. Because of the nature of this error, it can only occur with conventional lm-based radiography and does not occur with digital radiography.Remedy. After the lm packet has been exposed, it should be placed in a receptacle meant for exposed lms only. Exposed and unexposed lms should never be kept together in the same receptacle. When barrier envelopes are used, they can be removed between exposures to easily distinguish exposed lms from unexposed lms.Blurred images (Fig. 9.40). Blurred images are the result of patient, receptor, PID, or tube head movement during the exposure. Blurred images can occur with both conventional (lm-based) and digital radiography. However, with the current use of fast-speed lm or (especially) digital radiography, there is less of a chance for movement during exposure because of the very short exposure times utilized.Remedy. Tube heads, PIDs, and arms should be adjusted to prevent vibration and drifting. In most states, drifting is a serious health code violation. It is also suggested to make sure that the unit arm is stabilized on a nearby wall to prevent drifting. In addition, good chairside technique by the dental professional can help to prevent receptor and patient movement.Failure to remove dental appliances, eyeglasses (with metallic components) or facial jewelry (Figs. 9.41 and 9.42). If dental appliances or facial jewelry is not removed, the metallic portions will be superimposed on the teeth and surrounding structures.Remedy. It should be a part of the work routine to have patients remove all dentures, nose and lip jewelry, and eyeglasses. For panoramic and extraoral projections, patients also must remove earrings, hearing aids, necklaces, hair clips, and any other metallic objects from the entire head and neck region.Common bitewing errors (Fig. 9.43). The three most common errors seen on bitewing radiographs are overlapping, collimator cutoff, and poor receptor placement.• Figure 9.38 Overexposed radiograph. • Figure 9.39 Double exposure on a radiograph. • Figure 9.40 Blurred image caused by patient movement. 103CHAPTER 9 Intraoral Radiographic Technique: The Paralleling MethodPROCEDURE 9.1 THE FULL-MOUTH SURVEY—cont’dOverlapping (see Fig. 9.43A). Overlapping results from improper horizontal beam alignment or improper placement of the receptor in the horizontal plane. Bitewing overlap can occur with conventional and digital radiography.Remedy. The beam should be aligned in the horizontal plane so that it is at right angles to the receptor. Also, the receptor should be placed parallel to the teeth in the horizontal plane.Collimator cutoff (cone cutting; see Fig. 9.43B). Collimator cutoff is failure to align the central ray with the center of the receptor. It can also occur when bitewing tabs instead of XCP instruments are being used, because the operator loses sight of the bite tab when the patient closes the mouth. This error can occur with bitewing exposures in conventional and digital radiography.Remedy. It is recommended to use paralleling instruments (i.e., XCP devices) with localizing rings to decrease the incidence of collimator cutoff. A localizing ring can be used to help center the x-ray beam. When using bitewing tabs, the bite tab should be kept visible by asking the patient to smile while biting. If this is not possible, the operator can touch the tab with one hand while aligning the beam with the other. The central ray is then directed at the tab.Poor receptor placement (see Fig. 9.43C). Poor receptor placement occurs with bitewing lms in various ways. When the patient is allowed to bite the receptor into position after the operator has let go of the holder or when the patient bites in protrusive instead of centric relation, allowing the receptor to oat free and be repositioned by the tongue. Also, inadequate closure can occur when the patient is not biting completely on both sides of the bite piece or when the patient holds the bitewing holder with the lips instead of with the teeth, which can produce an image that does not show the teeth of both arches equally represented. If all of the desired structures are not represented on the image because of improper receptor placement in the patient’s mouth, this is considered a poor Continued• Figure 9.41 Patient’s metal-based partial denture was not removed. • Figure 9.42 Facial jewelry (nose ring) was not removed. • Figure 9.43 A, Overlapped bitewing. B, Collimator cutoff on bitewing. C, Improper lm placement on a bitewing. 104 CHAPTER 9 Intraoral Radiographic Technique: The Paralleling MethodChapter Summary• eradiographicexaminationisanimportantpartofthedental examination that stresses the need for radiographs that are diagnostically acceptable and are taken only when necessary for the patient’s immediate dental health needs. e goal of dental radiography is to produce the most diagnostically acceptable radiographs for the least amount of exposure to the patient.• Aperiapical projection shows the entire tooth from the incisal edge or the occlusal surface to the apex of the root and 2 to 3 mm of surrounding periapical bone. is projection is necessary to diagnose normal or pathologic conditions of tooth crowns and root, bone, and tooth formation and eruption (see Fig. 9.2). e bitewing projection shows the upper and lower teeth in occlusion in one image. Only the crowns and alveolar crest of the bone of adjacent teeth are seen. It is used for detecting interproximal decay, interproxi-mal calculus, periodontal bone loss, recurrent decay under restorations, and faulty restorations. Vertical bitewings can be used diagnostically for root caries, bone loss of 5 mm or more, and in pediatric patients to see the growth and development of the secondary dentition.• e basic principles of the paralleling technique forintraoral periapical projections is that the receptor and the long axis of the tooth being radiographed must be parallel to each other, and the central ray of the x-ray beam must be directed perpendicular to both. e paral-leling technique is preferred when compared with the bisecting technique, because it produces better diagnostic images (dimensional accuracy), less exposure to critical organs (such as, the thyroid gland and the lens of the eye), a smaller exit dose, and easier standardization and execution. However, placement of the receptors with the paralleling technique may be dicult and uncomfortable for the patient.• Before exposing intraoral radiographs, the operatorshould follow infection control procedures; exhibit radiation safety precautions, including placing the lead apron and thyroid collar on the patient and maintaining the recommended 6-foot distance standing behind an acceptable barrier when exposing radiographs; set up the receptor-holding devices; gather and place all necessary supplies near the exposure area; adjust the dental chair; ask the patient to remove any metallic objects that will be in the direct path of the primary beam; turn on the x-ray unit; and set the exposure parameters that are appropriate for the patient.• Foreachexposure,thedentalradiographershouldplacethe receptor in the holding device, ensure that the recep-tor is placed parallel to the teeth being exposed, aim the central ray perpendicular to the teeth and receptor in both the vertical and horizontal planes, place the receptor so that all the teeth that are desired will appear on the resultant image, and direct the central ray at the center of the receptor.• Receptor-holdingdeviceswithaimingarmsandlocalizingrings are recommended to simplify the intraoral parallel-ing exposure technique and to aid the radiographer in reducing the incidence of errors, including collimator cuto, overlapping, foreshortening, and elongation.• eerrorsthatcouldpotentiallyoccurwithbothcon-ventional lm-based radiography and digital radiography are collimator cuto, horizontal overlapping, blurred images, and failure to remove metallic objects. ose errors that are related to both lm-based radiography and digital radiography but are more likely to happen with conventional (lm-based) radiography are underexposed (light) and overexposed (dark) images. e errors that transpire only with conventional (lm-based) radiogra-phy are reversed lm, double exposure, and overbending of the lm packet.PROCEDURE 9.1 THE FULL-MOUTH SURVEY—cont’dreceptor placement error as well. For example, if the operator takes a premolar bitewing and the distal surface of the canine and the rst and second premolars are not shown completely, that would be considered a receptor placement error. All of these errors can occur with bitewing exposures in conventional and digital radiography.Remedy. The operator should not let go of the receptor holder (or bitewing tab) until the patient is biting on it in centric occlusion. The operator should make sure that the patient is biting completely on the bite piece and not using the lips to stabilize the bitewing holder in place. Also, the operator is responsible for centering the bitewing holder and receptor correctly so that all of the desired structures for that specic projection will appear on the image. 105CHAPTER 9 Intraoral Radiographic Technique: The Paralleling MethodChapter Review QuestionsMultiple Choice1. A full-mouth survey (FMS): a. Varies in need b. Varies in number c. Is prescribed based on a patient’s radiation history d. Can be prescribed based on the patient’s immediate dental health needs e. All of the above2. Interproximal caries, interproximal calculus, recurrent caries, periodontal bone loss, and the t of metallic restorations are best seen on: a. Panoramic radiographs b. Bitewing radiographs c. Periapical radiographs d. Topographic occlusal radiographs e. Right-angle occlusal radiographs3. Vertical bitewings can be used for viewing: a. Root caries b. Tooth eruption c. Advanced bone loss d. Bone loss of more than 5 mm e. All of the above4. e advantage in using a lm holder with a localizing ring is that it primarily: a. Reduces the incidence of collimator cuto b. Reduces the incidence of double exposure c. Keeps the lm in place more securely than another lm holder d. Reduces the incidence of overlapping e. Under all circumstances, guarantees a more diagnostic image5. Blurred images are a result of movement during an exposure. is error can be remedied by making sure that the white side of the lm packet is toward the source of radiation. a. Both statements are false. b. Both statements are true. c. e rst statement is true, and the second statement is false. d. e rst statement is false, and the second statement is true. e. ere is not enough information to answer the question.Identify the Following Intraoral Radiographic Errors1. is image: a. Was produced by too much vertical angulation b. Was produced by too little vertical angulation c. Is known as elongation d. Both a and c are correct. e. Both b and c are correct.2. is error can be remedied by: a. Centering the lm on the lm holder b. Centering the central ray while using a cylindrical column c. Centering the central ray while using a rectangular column d. Centering the tooth on the lm e. Making sure the developer solution contacts the entire lm 106 CHAPTER 9 Intraoral Radiographic Technique: The Paralleling MethodBibliographyAmerican Academy of Oral and Maxillofacial Radiology: Standards of care, intraoral imaging, AAOMR Newsletter 25:1998.American Dental Association Council on Scientic Aairs: An update on radiographic practices: information and recommendations, J Am Dent Assoc 132:234–238, 2001.Iannucci JM, Howerton LJ: Dental radiography: Principles and tech-niques, ed 5, St Louis, MO, 2016, Elsevier Saunders.Langland OE, Langlais RP: Principles of dental imaging, Baltimore, MD, 1997, Williams & Wilkins.National Center for Health Care Technology: Dental radiology: A summary of recommendations from the Technology Assessment Forum, J Am Dent Assoc 103:423–425, 1981.Stabulas JJ: Vertical bitewings, the other option, J Prac Hyg 11(3):46–47, 2002.ompson EM, Johnson ON: Essentials of dental radiography for dental assistants and hygienists, ed 9, Upper Saddle River, NJ, 2012, Pearson Education, Inc.U.S. Department of Health and Human Services, Public Health Service FDA: e selection of patients for dental radiographic examinations, HHS/PHS/FDA, 88-827310-21, 1987.White SC, Pharoah MJ: Oral radiology: Principles and interpretation, ed 7, St Louis, MO, 2013, Mosby. a. Using the same lm packet more than once b. Reversing a lm packet c. Using a slow-speed lm d. Tube head movement e. Improper safelighting5. e accompanying bitewing radiograph: a. Is not diagnostic b. Shows collimator cuto c. Shows incorrect horizontal angulation d. Both a and b are correct. e. Both a and c are correct.3. e dark diagonal artifact on the molar in the accompa-nying image can be remedied by: a. Avoiding excess exposure time b. Avoiding excess lm manipulation c. Centering the central ray d. Correcting the horizontal angulation e. Correcting the vertical angulation4. e associated image depicts the intraoral exposure error caused by:

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