Conditions Related to Loss of Tooth Structure










Atlas of Oral and Maxillofacial Radiology, First Edition. Bernard Koong.
© 2017 John Wiley & Sons Ltd. Published 2017 by John Wiley & Sons Ltd.
54
4.1 Caries (Figures4.1–4.12)
Bacterial demineralisation of tooth structure.
Related to bacterial dental plaque formation and presence of
simple sugars.
The clinical features are well described.
Usually asymptomatic until the lesion approximates or
involves the pulp.
Most common direct and indirect cause of pulpal pathology
and associated periapical inflammatory lesions.
Several factors contribute to the presence of caries, notably
xerostomia.
Treatment varies from improved oral hygiene, topical fluoride
to a range of restorative (‘fillings’) procedures as well as the
management of contributing factors, when present.
Recurrent caries are lesions which occur at the margins of
restorations (Figure4.12).
Clinical and radiological diagnosis of caries can be challenging.
Radiological identification of a carious lesion, unless obvi-
ous, should be verified clinically.
While not without limitations, intraoral 2D radiography
remains the imaging modality of choice.
Caries cannot be fully excluded with the panoramic radi-
ograph, although many lesions can be identified, espe-
cially moderate and large lesions.
Although the precise morphology and extent of carious
lesions can be well demonstrated with cone beam com-
puted tomography (CBCT) and multidetector computed
tomography (MDCT), the application of these tech-
niques in caries diagnosis requires further clarification.
There has been concern with specificity. When present,
artefacts related to restorations substantially reduce the
ability to identify carious lesions.
Interproximal caries (Figures4.1–4.7)
Originate at the mesial and distal surfaces of the crowns, usu-
ally between the contact point and the gingival margin.
Radiological features
Within the enamel, the early lesion presents as a relatively well‐
defined triangular‐shaped lucency with the base at the enamel
surface. This triangular morphology is lost as the lesion enlarges.
Enamel lesions can also present with a more linear morphology.
When the lesion reaches the dentinoenamel junction (DEJ), it
spreads out along the DEJ, resulting in the appearance of a rela-
tively ill‐defined triangular lucency within the dentin. Thebase
of this second triangular lucency is at the DEJ with the apex
directed towards the pulp. However, other presentations, such
as more linear or rounded appearances, are possible.
As the lesion progresses, it takes on a generally rounded
morphology, usually progressing quicker within the dentin than
within the enamel. Large lesions usually present with more sub-
stantial dentin involvement, undermining the overlying enamel,
which may fracture. Extremely large lesions often contribute to
complete or near complete loss ofthe entire tooth crown.
On CBCT and MDCT, the lucent lesions usually demonstrate
a more well‐defined appearance than is seen on intraoral or
panoramic radiographs, especially the lesions within dentin.
Differential diagnosis
Key radiological differences
Cervical burnout Artefactual and seen on intraoral and
panoramic radiographs. Present as
lucencies in the interproximal regions
but usually extends from the cementoe-
namel junction to the interdental
alveolar crest.
Lucent or absent
(lost)restoration
Usually more well defined and may
demonstrate sharp surgically prepared
angles.
Pit and fissure caries (Figures4.8–4.10; see alsoFigure 5.4)
Caries originating at developmental pits and fissures, usually
at the occlusal, buccal and palatal aspects of the crown, most
common at the occlusal pit or fissure.
CHAPTER 4
Conditions Related toLoss ofTooth Structure
Tom Huang and Bernard Koong

Radiological features
2D radiographs: the dentin lucency is usually seen first,
subjacent to enamel. The enamel lesion is usually not seen
unless large. It is difficult to identify if these lesions are buccal,
lingual or occlusal although the occlusal dentin lesion appears
more centred against the occlusal enamel.
On CBCT and MDCT: the dentin lucency is usually more
well defined and the location is better demonstrated. The
enamel lesion may be seen.
When large, cavitation often occurs.
Differential diagnosis
Key radiological differences
Deep pits and fissures It is often difficult to differentiate
these from carious lesions. Clinical
correlation is important.
Root caries (Figure4.11)
Caries involving the root surface, usually accompanied with
gingival recession.
Radiological features
Seen as lucent lesions apical to the cemento enamel junction.
Usually coronal to the alveolar crest. Occasionally extend
beyond the alveolar crest.
Differential diagnosis
Key radiological differences
Cervical burnout Artefactual and seen on bitewings or
periapical radiographs. Present as
lucencies in the interproximal
regions but usually extends from the
cementoenamel junction to the
interdental alveolar crest.
Well-defined triangular-shaped lucency
within the enamel with the apex directed
towards the DEJ
Figure4.1 Proximal (mesial and distal) enamel caries: cropped intraoral bitewing radiograph.
Linear lucency
in the enamel
Small subtle
lucency
Figure4.2 Proximal enamel caries, 36 and 37: cropped intraoral bitewing radiograph.
Conditions Related toLoss ofTooth Structure 55

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Atlas of Oral and Maxillofacial Radiology, First Edition. Bernard Koong. © 2017 John Wiley & Sons Ltd. Published 2017 by John Wiley & Sons Ltd.544.1 Caries (Figures4.1–4.12)• Bacterial demineralisation of tooth structure.• Related to bacterial dental plaque formation and presence of simple sugars.• The clinical features are well described.• Usually asymptomatic until the lesion approximates or involves the pulp.• Most common direct and indirect cause of pulpal pathology and associated periapical inflammatory lesions.• Several factors contribute to the presence of caries, notably xerostomia.• Treatment varies from improved oral hygiene, topical fluoride to a range of restorative (‘fillings’) procedures as well as the management of contributing factors, when present.• Recurrent caries are lesions which occur at the margins of restorations (Figure4.12).• Clinical and radiological diagnosis of caries can be challenging. ◦Radiological identification of a carious lesion, unless obvi-ous, should be verified clinically. ■ While not without limitations, intraoral 2D radiography remains the imaging modality of choice. ■ Caries cannot be fully excluded with the panoramic radi-ograph, although many lesions can be identified, espe-cially moderate and large lesions. ■ Although the precise morphology and extent of carious lesions can be well demonstrated with cone beam com-puted tomography (CBCT) and multidetector computed tomography (MDCT), the application of these tech-niques in caries diagnosis requires further clarification. There has been concern with specificity. When present, artefacts related to restorations substantially reduce the ability to identify carious lesions.Interproximal caries (Figures4.1–4.7)• Originate at the mesial and distal surfaces of the crowns, usu-ally between the contact point and the gingival margin.Radiological features• Within the enamel, the early lesion presents as a relatively well‐defined triangular‐shaped lucency with the base at the enamel surface. This triangular morphology is lost as the lesion enlarges. Enamel lesions can also present with a more linear morphology.• When the lesion reaches the dentinoenamel junction (DEJ), it spreads out along the DEJ, resulting in the appearance of a rela-tively ill‐defined triangular lucency within the dentin. Thebase of this second triangular lucency is at the DEJ with the apex directed towards the pulp. However, other presentations, such as more linear or rounded appearances, are possible.• As the lesion progresses, it takes on a generally rounded morphology, usually progressing quicker within the dentin than within the enamel. Large lesions usually present with more sub-stantial dentin involvement, undermining the overlying enamel, which may fracture. Extremely large lesions often contribute to complete or near complete loss ofthe entire tooth crown.• On CBCT and MDCT, the lucent lesions usually demonstrate a more well‐defined appearance than is seen on intraoral or panoramic radiographs, especially the lesions within dentin.Differential diagnosisKey radiological differencesCervical burnout Artefactual and seen on intraoral and panoramic radiographs. Present as lucencies in the interproximal regions but usually extends from the cementoe-namel junction to the interdental alveolar crest.Lucent or absent (lost)restorationUsually more well defined and may demonstrate sharp surgically prepared angles.Pit and fissure caries (Figures4.8–4.10; see alsoFigure 5.4)• Caries originating at developmental pits and fissures, usually at the occlusal, buccal and palatal aspects of the crown, most common at the occlusal pit or fissure.CHAPTER 4Conditions Related toLoss ofTooth StructureTom Huang and Bernard Koong Radiological features• 2D radiographs: the dentin lucency is usually seen first, subjacent to enamel. The enamel lesion is usually not seen unless large. It is difficult to identify if these lesions are buccal, lingual or occlusal although the occlusal dentin lesion appears more centred against the occlusal enamel.• On CBCT and MDCT: the dentin lucency is usually more well defined and the location is better demonstrated. The enamel lesion may be seen.• When large, cavitation often occurs.Differential diagnosisKey radiological differencesDeep pits and fissures It is often difficult to differentiate these from carious lesions. Clinical correlation is important.Root caries (Figure4.11)• Caries involving the root surface, usually accompanied with gingival recession.Radiological features• Seen as lucent lesions apical to the cemento enamel junction.• Usually coronal to the alveolar crest. Occasionally extend beyond the alveolar crest.Differential diagnosisKey radiological differencesCervical burnout Artefactual and seen on bitewings or periapical radiographs. Present as lucencies in the interproximal regions but usually extends from the cementoenamel junction to the interdental alveolar crest.Well-defined triangular-shaped lucencywithin the enamel with the apex directedtowards the DEJ Figure4.1 Proximal (mesial and distal) enamel caries: cropped intraoral bitewing radiograph.Linear lucencyin the enamelSmall subtlelucencyFigure4.2 Proximal enamel caries, 36 and 37: cropped intraoral bitewing radiograph.Conditions Related toLoss ofTooth Structure 55 Large ill-defined diffuseand more rounded lucency within the dentin reflects a large dentin lesion Well-defined enamel lucent lesion remains relatively small Figure4.4 Caries within distal enamel and dentin, 25: cropped intraoral bitewing radiograph.Lucency in enamel at the mesial surface of 27. Within dentin, the lucencyextends along the DEJ (a) (b)Figure4.5 Caries in mesial enamel and dentin, 27: corrected sagittal (a) and axial (b) CBCT images.Ill-defined triangular-shaped lucency in the dentinwith the apex directedtowards the pulp Enamel lucent cariouslesion with early extensionalong the DEJ Small well-definedlucent triangular-shapedearly enamel caries Figure4.3 Proximal enamel and dentin caries: intraoral bitewing radiograph. Conditions Related toLoss ofTooth Structure 57Lucency in the enamelat the mesial surface of 16.Within the dentin, the lucencyextends along the DEJ Hypodense focus at the occlusal enamel. Lucency withinthe dentin extends along the DEJ (a) (b)Figure4.6 Caries in mesial and occlusal enamel and dentin, 16: corrected sagittal (a) and axial (b) CBCT images.Large carious lesion within the dentin extending tothe 17 pulp. The margins are relatively well defined. Note thatdentinal lesions usually appearrelatively ill defined on intraoraland panoramic radiographs Note is made of the artefact associated with the metallic restorations.Allowing for this, lucencyin the 16 mesial surfaceprobably reflects caries This overlying enamel has been undermined by the largedentinal lesion (which originated fromthe mesial surface). This enamel is likelyto fracture under normal functional load (a) (b)Figure4.7 Caries in mesial enamel and dentin, 17 and 16: corrected sagittal (a) and axial (b) CBCT images. Occlusal caries within 46 is better demonstrated on the periapical radiograph,with a slight negative angulation Large ill-defined lucent occlusal caries within 47 (a) (b)Figure4.9 Occlusal caries: intraoral bitewing (a) and periapical (b) radiographs.Small round lucency at the centre of 46 at the DEJ reflects the buccal pit, a normal anatomical feature Figure4.10 Buccal pit: cropped panoramic radiograph.Relatively large ill-defined lucency within the dentin centred at the occlusal DEJ of the 38 and 37 crowns. The enamel lesions are not demonstrated Figure4.8 Occlusal caries, 37 and 38: cropped panoramic radiograph. Conditions Related toLoss ofTooth Structure 594.2 Attrition (Figure4.13)• Gradual loss of tooth structure from contact of teeth; related to mechanical forces.• Most often seen at the incisal and occlusal surfaces where oppos-ing teeth contact. Occasionally at the interproximal surfaces.• May eventually involve the dentin.• When the degree of attrition is age appropriate, it is usually considered physiological.• Parafunctional activities, including clenching and bruxism (‘grinding’), are common causes of excessive or pathological attrition.• Other factors, including diet, saliva and resistance of the tooth crown to mechanical wear, may influence the rate of attrition.• Only affects erupted teeth, so this condition is clinically observable.• Not uncommonly seen in the deciduous teeth in children, presumably related to bruxism, which often ceases as perma-nent teeth erupt.• May require management if excessive for age.Radiological features• Flattened appearance of the incisal edges of the anterior teeth and occlusal surfaces of the posterior teeth. Where more severe, the crowns appear short.• Flattened interproximal surfaces are much less common.• Reduction in the size of the pulp chamber is usually evident in moderate to severe attrition, related to increased formation of secondary/tertiary dentin. Narrowing of the root canals is sometimes seen.The cervical aspect of this lucentdefect demonstrates thetypically ill-defined borderof root caries. The well-definedborder superiorly is relatedto toothbrush abrasion.Note the periodontal bone lossFigure4.11 Root caries at abrasion defect, 43: intraoral periapical radiograph.Ill-defined lucency subjacent to the 35 restoration reflects recurrent caries Figure4.12 Recurrent caries: intraoral bitewing radiograph. 60 Atlas of Oral and Maxillofacial Radiology4.3 Abrasion (Figure4.14)• Non‐physiological gradual loss of tooth structure related to repeated contact of teeth with a foreign object.• Most commonly related to excessive incorrect tooth brushing and, less commonly, flossing. Occasionally seen in associa-tion with repeated biting of hard items such as pins, pipes, etc.• May expose dentin and contribute to tooth hypersensitivity.• Clinically evident.Radiological features• Most commonly presents as a V‐shaped groove defect or a concave dish‐shaped defect at the cervical aspects of the teeth, usually the buccal/labial surfaces. Sometimes seen interproxi-mally, related to dental flossing.• Usually appears as a relatively well‐defined lucency on 2D intraoral and panoramic radiographs. The morphology is appreciated on CBCT and MDCT.• Focal narrowing of the cervical pulp chamber and root canals is often seen with moderate and severe lesions, related to tertiary dentin formation.Flattening of the incisal edges and the occlusal surfaces Figure4.13 Attrition: cropped panoramic radiograph.V-shaped groove/concave defects centred at the cervical aspects of 24, 25 and 26(a) (b)Figure4.14 Abrasion: cross‐sectional (para‐axial) (a) and surface‐rendered (b) CBCT images. Conditions Related toLoss ofTooth Structure 61Flattening of the incisal edge of the with a ‘cupping’ appearance Figure4.15 Erosion: cropped panoramic radiograph.Differential diagnosisKey radiological differencesCaries Differentiation can be difficult. Abrasion lesions demonstrate more well‐defined margins. The V‐ or concave‐shaped morphology is typical, better demonstrated on CBCT and MDCT. However, abrasion lesions are usually clinically obvious.4.4 Erosion (Figure4.15)• Non‐microbial chemical‐related gradual loss of tooth structure.• Most commonly related to acidic foods and drinks.• Gastric acids can also cause erosion. For example, acid reflux and chronic vomiting.• Usually seen in the younger person.• Clinically observable and the location of the erosive lesions may provide clues to the probable cause.Radiological features• These defects appear lucent on 2D intraoral/panoramic radio-graphs and often demonstrate a concave ‘cupping’ morphology at the incisal/palatal surfaces of the crowns. The margins often appear ‘feathered’ on intraoral and panoramic radiographs.• Most commonly affects anterior teeth, usually several teeth.Differential diagnosisKey radiological differencesAbrasion Abrasion lesions usually demonstrate the typical morphology and the margins are more well defined.4.5 Internal resorption (Figures4.16 and4.17)• Resorption of the pulpal walls (dentin) by activation of odontoclastic cells.• Often idiopathic. May be related to insult to the pulp/tooth. For example, trauma and pulpotomies. Also not infrequently seen within longstanding impacted third molars.• If it involves the coronal pulp of an erupted tooth and is of sufficient size, a pink hue may be clinically observed. Enamel fracture may occur with large coronal lesions.• Larger radicular lesions may extend to the cemental surface. There is also an associated risk for pathological root fracture.• More cervically positioned radicular lesions involving theroot surface may be associated with periodontal bone loss.Radiological features• Identification and evaluation of the extent/morphology of these lesions are more accurately performed with CBCT or MDCT.• Usually presents as a focal lucent/hypodense widening of the pulp chamber or root canal with a well‐defined, sometimes scalloped or irregular, margin.• May extend to the root surface, where it can be difficult to differentiate from external resorption. Can range from mini-mal to extensive lesions.Differential diagnosisKey radiological differencesCaries The margins of carious lesions are usually less well defined. Caries begins at the tooth surface.External resorption Usually larger at the tooth surface, as the resorption begins at the surface. 62 Atlas of Oral and Maxillofacial Radiology4.6 External resorption (Figure4.18; see also Figures3.9, 3.11, 3.21, 3.23, 5.8, 5.39, 7.13, 7.16–7.18, 8.15, 10.1,10.5, 10.6,12.9)• Resorption of the external surface of the tooth, more com-monly affecting the root. Associated with activation of osteo/odontoclastic cells. ◦Physiological: ■ Exfoliation process of deciduous teeth, as permanent suc-cessors erupt. ◦Pathological: ■ Often seen in association with pressure exerted upon the tooth. For example, orthodontic forces, impacted teeth, cysts and benign tumours. ■ Also seen in association with chronic periapical inflam-matory lesions. ■ Can be idiopathic.• Larger lesions may extend to the pulp. There is associated risk for pathological root fracture.• More cervically positioned radicular lesions may be associ-ated with periodontal bone loss.Radiological features• Identification and evaluation of the extent/morphology of these lesions are more accurately performed with CBCT or MDCT.• Well‐defined focal absence of tooth structure, with variable morphology. Begins at the tooth surface.• Radicular lesions are most commonly seen at the apex and cervically.• Apical lesions often result in a blunted appearance of the residual apex.Well-defined lucency within thecrown and root breaching the toothsurface at a few sites(a) (b)Figure4.16 Internal root resorption, 18: axial (a) and coronal (b) CBCT images.Relatively well-definedhypodense focus within the rootcentred upon the root canal whichdoes not extend to the root surface Torusmandibularis Figure4.17 Internal root resorption, 43: axial CBCT image. Conditions Related toLoss ofTooth Structure 63• The adjacent periodontal ligament space and lamina dura are almost always preserved, unless the resorption is related to a chronic inflammatory lesion or an entity (e.g. impacted tooth, cyst or tumour) which is in contact with the root surface.• When the resorption is related to direct pressure (e.g. impacted tooth, cyst or tumour) the morphology of the resorptive defect often matches the surface of the entity exerting the pressure (e.g. impacted third molar or canine, cysts and benign tumours).• Can be severe, where an entire tooth root is largely absent. For example, resorption of a lateral incisor, related to an ectopic impacted canine.Differential diagnosisKey radiological differencesInternal resorptionIt may be difficult to differentiate with intraoral and panoramic radiography. These are much better demonstrated with CBCT or MDCT although it can be occasionally difficult to differentiate large lesions where much of the root structure is resorbed.4.7 Fracture related totrauma• Refer to Chapter17.Well-defineddistopalatallucency(a) (b)Figure4.18 Invasive cervical root resorption, 21: axial (a) and sagittal (b) MDCT images.

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