Anomalies Related to the Teeth










28
3.1 Supernumerary teeth (Figures3.1–3.5)
Synonyms: hyperdontia, supplemental teeth, mesiodens,
paramolars.
Teeth developing in addition to the normal 32 permanent and
20 deciduous teeth.
1–4% of population.
More common in the permanent dentition. The anterior
maxilla and mandibular premolar regions are quite common
locations.
Multiple supernumerary teeth may be associated with some
syndromes.
May affect the normal dentition. For example, crowding,
impaction and, less commonly, resorption of the normal teeth.
Ultra‐low‐dose cone beam computed tomography (CBCT) or
multidetector computed tomography (MDCT) may be
required to accurately locate these teeth for removal and also
to assess the effects on the adjacent teeth.
Radiological features
Resemble teeth but the size and morphology may or may not
resemble the normal dentition.
Differential diagnosis
Key radiological differences
Compound
odontoma
Dental tissue arrangements are not as close to
normal tooth architecture, often demonstrating
a clump of multiple tooth‐like structures.
CHAPTER 3
Anomalies Related totheTeeth
Horizontally oriented small
supernumerary tooth with
crown directed mesiopalatally
(a)
(b)
(c)
Figure3.1 Supernumerary tooth left premaxilla: surface-rendered CBCT (a), cropped panoramic radiograph (b) and corrected sagittal CBCT (c) images.
Atlas of Oral and Maxillofacial Radiology, First Edition. Bernard Koong.
© 2017 John Wiley & Sons Ltd. Published 2017 by John Wiley & Sons Ltd.

Supernumerary tooth
superimposed over the 44 root.
Associated root resorption
cannot be excluded in this view
Figure3.2 Supernumerary tooth: cropped panoramic radiograph.
Right anterior mandibular
supernumerary
deciduous and per
manent
teeth resembling incisors
Figure3.3 Supernumerary teeth: cropped panoramic radiograph.
Supernumerary teeth in the 18,
11/21 and 28 regions. The
ant
erior supernumerary tooth is
not well demonstrat
ed, being at
the edge of the focal trough
Figure3.4 Supernumerary teeth: cropped panoramic radiograph.
Supernumerary tooth
contributes to the
impaction of the molar
Figure3.5 Supernumerary tooth left maxilla: coronal CBCT image.

30 Atlas of Oral and Maxillofacial Radiology
3.2 Congenital absence (Figures 3.6 and3.7)
Synonyms: hypodontia, partial or complete anodontia,
oligodontia.
Third molars are most commonly affected, followed by sec-
ond premolars, maxillary lateral incisors and mandibular
central incisors.
May be seen in ectodermal dysplasia.
Occasionally, ultra‐low‐dose CBCT or MDCT may be
required to confirm absence where there is suspicion that the
tooth is ectopic and may not be visualised within the field of
view of the intraoral radiograph or is outside of the focal
trough of the panoramic radiograph.
Radiological features
Absence of normal dentition.
Differential diagnosis
Key radiological differences
Delayed development This is occasionally challenging
as there is a large variation in the
chronology of tooth development
and contralateral teeth may also
be absent.
Ectopic teeth Present but not located in the
normal position.
C
ongenital absence of 25, 35
and 45; 65, 75 and 85 are
retained
Figure3.6 Congenital absence: cropped panoramic radiograph.
Several congenitally absent permanent teeth.
Note several retained deciduous teeth
Figure3.7 Partial anodontia: panoramic radiograph.
Anomalies Related totheTeeth 31
3.3 Delayed andearly development/eruption
Many tables identifying the mean development/eruption
times of teeth in relation to chronological age are widely avail-
able. However, the wide variation in the chronology of tooth
development and eruption is noted.
Eruption is when a tooth is seen in the oral cavity.
Several local conditions, including impactions, presence of
supernumerary teeth and pathology, can delay tooth eruption
and alter development. Ultra‐low‐dose CBCT or MDCT may
be useful for these cases.
Radiological features
Radiological investigations are often performed to evaluate
whether all the teeth are present, and whether entities are
present that may interfere with the development and eruption
of the teeth.

32 Atlas of Oral and Maxillofacial Radiology
3.4 Ectopic development anderuption
(Figures 3.8–3.16)
When a tooth develops and erupts away from its expected
native location.
Transposition is where two adjacent teeth have exchanged
positions, most commonly involving the maxillary canines
and first premolars.
It is noted that pathological entities, such as cysts and tumours,
can displace teeth.
Radiological features
A key radiological role in the evaluation of ectopic teeth is to
ensure that the ectopic position is developmental in nature
and not related to tooth displacement by a pathological
entity.
Ultra‐low‐dose CBCT or MDCT should be considered, espe-
cially if the precise location is required or if there isconcern
for possible associated abnormality which is not clearly
depicted on intraoral and/or panoramic radiography.
Mesiopalatally ectopically positioned
impacted 13 and 23. The MDCT scan
demonstrates no root resorption, which
cannot be excluded with the panoramic
radiograph
(a) (b)
Figure3.8 Impacted 13 and 23: cropped panoramic radiograph (a) and axial MDCT image (b).
Mesiopalatally positioned
impacted 23. Resorption of the
22 root is demonstrated on the
MDCT scan
Labially positioned impacted 13
with no 12 root resorption
(a) (b)
Figure3.9 Impacted 13 and 23: axial MDCT image (a) and cropped panoramic radiograph (b).

Anomalies Related totheTeeth 33
Mesiolabially positioned
impacted 13 with no 12 root
resorption
(a) (b)
(c)
Figure3.10 Impacted 13: surface-rendered (a,b) and cross-sectional (para-axial) (c) CBCT images.
Mesially positioned
ect
opic, impacted 13
contacts the 12 root
with severe 12
root resorption
(a) (b)
Figure3.11 Impacted tooth: corrected sagittal and cross‐sectional (para‐axial) CBCT images (a,b).

The position of the ectopic 33 is
precisely demonstrated on the
CBCT scan
(a) (b)
Figure3.13 Ectopic 33: cropped panoramic radiograph (a) and axial CBCT image (b).
Ectopic 43 with the crown
superimposed over the
32 apex where root
r
esorption cannot be excluded
Figure3.12 Ectopic 43: cropped panoramic radiograph.
Tooth 23 is locat
ed
between 24
and 25 labially
T
ooth 24
(a)
(b) (c)
Figure3.14 Transposition 23 and 24: reconstructed panoramic (a), surface‐rendered (b) and axial CBCT (c) images.

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283.1 Supernumerary teeth (Figures3.1–3.5)• Synonyms: hyperdontia, supplemental teeth, mesiodens, paramolars.• Teeth developing in addition to the normal 32 permanent and 20 deciduous teeth.• 1–4% of population.• More common in the permanent dentition. The anterior maxilla and mandibular premolar regions are quite common locations.• Multiple supernumerary teeth may be associated with some syndromes.• May affect the normal dentition. For example, crowding, impaction and, less commonly, resorption of the normal teeth.• Ultra‐low‐dose cone beam computed tomography (CBCT) or multidetector computed tomography (MDCT) may be required to accurately locate these teeth for removal and also to assess the effects on the adjacent teeth.Radiological features• Resemble teeth but the size and morphology may or may not resemble the normal dentition.Differential diagnosisKey radiological differencesCompound odontomaDental tissue arrangements are not as close to normal tooth architecture, often demonstrating a clump of multiple tooth‐like structures.CHAPTER 3Anomalies Related totheTeethHorizontally oriented small supernumerary tooth with crown directed mesiopalatally(a)(b)(c)Figure3.1 Supernumerary tooth left premaxilla: surface-rendered CBCT (a), cropped panoramic radiograph (b) and corrected sagittal CBCT (c) images.Atlas of Oral and Maxillofacial Radiology, First Edition. Bernard Koong. © 2017 John Wiley & Sons Ltd. Published 2017 by John Wiley & Sons Ltd. Supernumerary toothsuperimposed over the 44 root. Associated root resorption cannot be excluded in this viewFigure3.2 Supernumerary tooth: cropped panoramic radiograph.Right anterior mandibularsupernumerarydeciduous and permanentteeth resembling incisorsFigure3.3 Supernumerary teeth: cropped panoramic radiograph.Supernumerary teeth in the 18,11/21 and 28 regions. The anterior supernumerary tooth isnot well demonstrated, being at the edge of the focal troughFigure3.4 Supernumerary teeth: cropped panoramic radiograph.Supernumerary toothcontributes to theimpaction of the molarFigure3.5 Supernumerary tooth left maxilla: coronal CBCT image. 30 Atlas of Oral and Maxillofacial Radiology3.2 Congenital absence (Figures 3.6 and3.7)• Synonyms: hypodontia, partial or complete anodontia, oligodontia.• Third molars are most commonly affected, followed by sec-ond premolars, maxillary lateral incisors and mandibular central incisors.• May be seen in ectodermal dysplasia.• Occasionally, ultra‐low‐dose CBCT or MDCT may be required to confirm absence where there is suspicion that the tooth is ectopic and may not be visualised within the field of view of the intraoral radiograph or is outside of the focal trough of the panoramic radiograph.Radiological features• Absence of normal dentition.Differential diagnosisKey radiological differencesDelayed development This is occasionally challenging as there is a large variation in the chronology of tooth development and contralateral teeth may also be absent.Ectopic teeth Present but not located in the normal position.Congenital absence of 25, 35 and 45; 65, 75 and 85 are retainedFigure3.6 Congenital absence: cropped panoramic radiograph.Several congenitally absent permanent teeth.Note several retained deciduous teethwith variable resorptionFigure3.7 Partial anodontia: panoramic radiograph. Anomalies Related totheTeeth 313.3 Delayed andearly development/eruption• Many tables identifying the mean development/eruption times of teeth in relation to chronological age are widely avail-able. However, the wide variation in the chronology of tooth development and eruption is noted.• Eruption is when a tooth is seen in the oral cavity.• Several local conditions, including impactions, presence of supernumerary teeth and pathology, can delay tooth eruption and alter development. Ultra‐low‐dose CBCT or MDCT may be useful for these cases.Radiological features• Radiological investigations are often performed to evaluate whether all the teeth are present, and whether entities are present that may interfere with the development and eruption of the teeth. 32 Atlas of Oral and Maxillofacial Radiology3.4 Ectopic development anderuption (Figures 3.8–3.16)• When a tooth develops and erupts away from its expected native location.• Transposition is where two adjacent teeth have exchanged positions, most commonly involving the maxillary canines and first premolars.• It is noted that pathological entities, such as cysts and tumours, can displace teeth.Radiological features• A key radiological role in the evaluation of ectopic teeth is to ensure that the ectopic position is developmental in nature and not related to tooth displacement by a pathological entity.• Ultra‐low‐dose CBCT or MDCT should be considered, espe-cially if the precise location is required or if there isconcern for possible associated abnormality which is not clearly depicted on intraoral and/or panoramic radiography.Mesiopalatally ectopically positionedimpacted 13 and 23. The MDCT scandemonstrates no root resorption, whichcannot be excluded with the panoramicradiograph (a) (b)Figure3.8 Impacted 13 and 23: cropped panoramic radiograph (a) and axial MDCT image (b).Mesiopalatally positioned impacted 23. Resorption of the 22 root is demonstrated on the MDCT scanLabially positioned impacted 13 with no 12 root resorption(a) (b)Figure3.9 Impacted 13 and 23: axial MDCT image (a) and cropped panoramic radiograph (b). Anomalies Related totheTeeth 33Mesiolabially positioned impacted 13 with no 12 rootresorption(a) (b)(c)Figure3.10 Impacted 13: surface-rendered (a,b) and cross-sectional (para-axial) (c) CBCT images.Mesially positionedectopic, impacted 13contacts the 12 rootwith severe 12root resorption(a) (b)Figure3.11 Impacted tooth: corrected sagittal and cross‐sectional (para‐axial) CBCT images (a,b). The position of the ectopic 33 isprecisely demonstrated on the CBCT scan(a) (b)Figure3.13 Ectopic 33: cropped panoramic radiograph (a) and axial CBCT image (b).Ectopic 43 with the crownsuperimposed over the32 apex where rootresorption cannot be excludedFigure3.12 Ectopic 43: cropped panoramic radiograph.Tooth 23 is locatedbetween 24 and 25 labiallyTooth 24(a)(b) (c)Figure3.14 Transposition 23 and 24: reconstructed panoramic (a), surface‐rendered (b) and axial CBCT (c) images. Anomalies Related totheTeeth 35Ectopic 28 interrupts theeruption of 27(a) (b)Figure3.15 Ectopic 28: axial MDCT image (a) and cropped panoramic radiograph (b).Ectopic mandibularpremolars Figure3.16 Two ectopic mandibular premolars: panoramic radiograph. 36 Atlas of Oral and Maxillofacial Radiology3.5 Impaction (Figures 3.17–3.23)• Usually refers to failure of eruption of a tooth where there is a physical obstruction, such as another tooth, dense bone or occasionally soft tissue. ◦The term non‐eruption is sometimes used to refer to teeth which do not erupt but do not demonstrate any particular dense physical barrier or pathology obstructing the erup-tion pathway.• Most commonly affecting the third molars (especially the mandibular), followed by the maxillary canines. Impacted teeth may be ectopic and/or abnormal in morphology. Supernumerary teeth are often impacted.• May be associated with: ◦Pericoronitis (refer to Chapter5). ◦Periodontal bone loss of the adjacent teeth (refer to Chapter5). ◦Caries (refer to Chapter4). ◦Root resorption. ◦Cystic and odontogenic tumours (refer to Chapters 8 and10).• Like any surgical procedure, extraction of the impacted teeth is associated with potential complications. A particular poten-tial risk associated with the removal of mandibular third molars is damage to the inferior alveolar nerve.Radiological features• Ultra‐low‐dose CBCT and MDCT are the imaging techniques of choice for: ◦Precise location and orientation of the impacted tooth and when the relationship with adjacent anatomical structures is required. Useful features demonstrated by these techniques include the number of roots, root morphology, mandibular and incisive canals, mental foramen, preservation of jaw cor-tices over the roots and relationship with the maxillary sinus. ◦Evaluation of associated pathology, such as root resorption of the adjacent teeth.• Third molars: ◦Panoramic radiograph is often employed initially. While it does not depict these impacted teeth as accurately and with as much detail as CBCT and MDCT, it may provide suffi-cient information. Based upon the appearances in this view, ultra‐low‐dose CBCT and MDCT are sometimes indicated. Indications include: ■ Mandibular canal appears projected over the third molar roots in the panoramic view.• There are radiological criteria (on panoramic radio-graphs) which have been used. Examples include dark-ening, narrowing, deviation of the canal and absence of the canal borders when projected over the third molar root. However, the absence of these criteria does not mean that there is no contact of the mandibular canal with the third molar. ■ Complex root anatomy including root dilacerations. ■ Suspicion for substantial cortical fenestrations over the roots. ■ Concern for possible resorption of adjacent teeth. For example, it is not uncommon that impacted teeth are projected over the adjacent teeth on panoramic and den-tal intraoral radiographs. Root resorption cannot be fully excluded in these views. ■ Suspicion for associated pathology. ◦Classification: ■ Assists in identifying the orientation and relative complexity in extracting the tooth, usually applied to the impacted mandibular third molars. ■ The most commonly used classification describes the orientation of the long axis third molar in relation to those of the adjacent molars.• Mesioangular impaction: third molar is mesially inclined.• Vertical impaction: third molar demonstrates a similar mesiodistal orientation to the other molars.• Distoangular impaction: third molar is distally inclined.• Horizontal impaction: third molar is essentially hori-zontally oriented, with the crown directed mesially. ■ Other additional descriptors sometimes used refer to the direction in which the crown is inclined in the other planes, namely buccal and lingual.• Impacted canines and supernumerary teeth: ◦Many of these cases are eventually examined with CBCT as it is often difficult to plan the surgical extraction/ exposure with panoramic and intraoral radiography, e.g. whether the surgical approach should be buccal or palatal for an impacted maxillary canine. Also, root resorption cannot be excluded nor the extent reliably evaluated with 2D radiography. Anomalies Related totheTeeth 37Verticallyimpacted 38Distoangularlyimpacted 48 Horizontally impacted 38 and 48 Mesioangularly impacted 38 and 48Mesioangularlyimpacted 48 with distal root dilacerationImpacted 18 and 28 Impacted 28(a) (b)(d)(c)(e)(f) (g)Figure3.17 Impacted third molars of several cases: cropped panoramic radiographs (a–g).Mesioangularly impacted 38.MDCT demonstratesthe mandibular canal flattenedbetween the roots (a) (b)Figure3.18 Impacted 38: cropped panoramic radiograph (a) and axial MDCT image (b). 38 Atlas of Oral and Maxillofacial RadiologyMesioangularly impacted 38 with severely dilacerated roots.Mandibular canal contacts the inferior surfacesFigure3.19 Impacted 38: corrected sagittal CBCT image.Mandibular canal traverses through (‘perforates’) the roots of the impacted 48(a) (b)Figure3.20 Impacted 48: corrected coronal (a) and axial (b) MDCT images. Mesioangularly impacted 38 contributes to the resorption of 37. Note also the associated distal periodontal bone loss of 37(a)(b)Figure3.21 Impacted 38: corrected sagittal (a) and axial (b) CBCT images.Mesioangularly impacted 38. The lingualposition of the root ‘external’ to the body ofthe mandible, with lingual cortical fenestration,is demonstrated on the MDCT image(a) (b)Figure3.22 Impacted 38: cropped panoramic radiograph (a) and corrected coronal MDCT image (b).26 is impacted against the distalaspect of 65 with associatedresorption of the deciduous molarFigure3.23 Impacted 26: cropped panoramic radiograph. 40 Atlas of Oral and Maxillofacial Radiology3.6 Macrodontia (Figure 3.24)• Larger than normal teeth.• Most are likely to be developmental in nature.• Occasionally seen in association with a vascular malforma-tion or haemangioma.Radiological features• Larger than normal tooth.• Most demonstrate essentially normal morphology.• May contribute to impactions and crowding.Differential diagnosisKey radiological differencesGemination May demonstrate morphology suggesting attempted division of a tooth into two, e.g.grooving of the crown/root.Fusion A tooth should be absent.Larger mesiodistal dimension of 11compared with 21(a) (b)Figure3.24 Macrodontic 11: axial (a) and surface‐rendered (b) CBCT images. Anomalies Related totheTeeth 413.7 Microdontia (Figures 3.25–3.27)• Smaller than normal teeth.• Most are likely to be developmental in nature. May be familial.• Most commonly affecting third molars and maxillary lateral incisors.• Occasionally related to childhood incident, e.g. chemotherapy.Radiological features• Smaller than normal tooth.• Often demonstrates altered morphology, e.g. a microdontic lateral incisor often has a conical crown.Small 22 with conical (‘pegged’)coronal morphologyEctopic 23Figure3.25 Microdontic 22: cropped panoramic radiograph.Small crowns of maxillarysecond molars Figure3.26 Microdontic 17 and 27: cropped panoramic radiograph.Small root of 35 withdiminutive crown Figure3.27 Microdontic 35 related to chemotherapy: corrected sagittal CBCT. 42 Atlas of Oral and Maxillofacial Radiology3.8 Dilaceration (Figure 3.28)• A distinct bend of a tooth crown or root. Root dilacerations are much more common.• Most are likely to be developmental in nature. Some may be related to trauma during tooth development.• May interfere with orthodontic tooth movement.Radiological features• Appearance of a distinct bend in the crown or root of a tooth.• This may not be appreciated on 2D intraoral or the panoramic radiograph or it may appear as a focal increased density.• CBCT or MDCT more accurately identify and demonstrate the precise morphology of dilacerations.Severe sigmoid dilaceration of the 22 rootSevere root dilacerations of 38,with root apices directedposterosuperiorly(a) (b)Figure3.28 Root dilacerations of two separate cases: cropped panoramic radiograph (a) and corrected sagittal CBCT image (b).Focal enamelprominence with central smallamount of dentinat the distalsurface of 28cervically Figure3.29 Enamel pearl 28: axial CBCT image.3.9 Enamel pearl (Figure 3.29)• Synonym: enameloma.• A small focal enamel prominence on the root, usually less than 3 mm, developmental in nature. Larger pearls may dem-onstrate a small amount of dentin at the base centrally.• Almost all are seen on molar roots, often at the cervical and furcation regions.• May have relevance to the progression and management of plaque‐related inflammatory periodontal disease.Radiological features• Smooth, round, well‐defined enamel density focus.• May not be detected with 2D intraoral or panoramic radiographs.Differential diagnosisKey radiological differencesPulp stone Within the pulp chamber or root canal of the tooth. The enamel pearl is more opaque than the pulp stone. Anomalies Related totheTeeth 433.10 Talon cusp (Figure 3.30)• An additional cusp of an incisor, thought to be related to an extremely prominent cingulum.• Developmental in nature.Radiological features• Appearance of an opaque cusp‐like structure over the incisor crown on 2D intraoral or panoramic radiographs. Clinically obvious when erupted.Differential diagnosisKey radiological differencesSupernumerary tooth May require volumetric imaging (CBCT or MDCT) to clarify.Odontoma May require volumetric imaging (CBCT or MDCT) to clarify.Additionalpalatal cusp(a) (b)Figure3.30 Talon cusp of two cases: cropped panoramic radiograph (a) and surface‐rendered CBCT image (b). 44 Atlas of Oral and Maxillofacial Radiology3.11 Dens invaginatus (Figures 3.31 and3.32)• Synonym: dens in dente.• Invagination of enamel into the crown, to varying extents.• Occurs most frequently in the maxillary lateral incisors.• Associated with increased risk of pulpal and periapical inflammatory disease: ◦Infolded enamel is often defective, including canals which lead to the pulp. ◦Usually, a deep pit connects this with the oral cavity, with resultant increased caries risk.• Radicular invaginations are rare, and involve infolding of cementum.Radiological features• Variable invagination of the pit or incisal edge.• Larger invaginations are associated with altered crown morphology.• There may be incomplete root development and/or peria-pical inflammatory lesions, related to the death of the pulp tissues.Intracoronal fold ofenamel with centrallucency Figure3.31 Dens invaginatus 22: cropped panoramic radiograph.Enamel-lined invagination at the cingulum region Lucent apicalinflammatorylesion(a) (b)Figure3.32 Dens invaginatus 22: cross‐sectional (para‐axial) (a) and axial (b) CBCT images. Anomalies Related totheTeeth 453.13 Taurodontism (Figure 3.34)• Longer body of the tooth with shorter roots.• Likely to be a normal variant in most cases. Reported to occur more frequently in trisomy 21 syndrome.Radiological features• Appearance of a longer body with short roots, and a normal crown.3.12 Dens evaginatus (Figure 3.33)• Small focal enamel prominence at the occlusal surfaces of posterior teeth or lingual surfaces of anterior teeth.• Often demonstrates dentin centrally and there may be an associated pulp horn.• More commonly affecting premolars and lateral incisors.• Associated with increased risk of pulpal and periapical inflammatory disease.Radiological features• Focal enamel prominence, usually with dentin centrally. A fine pulp horn is often only visualised in volumetric (CBCT or MDCT) imaging.• There may be incomplete root development and/or periapi-cal inflammatory lesions, related to the death of the pulp tissues.While evagination is (typically) not well demonstrated on this image, a patient will sometimes present with an apicalinflammatory lesion, with no other identifiable potential cause (e.g. substantialcaries or a deep restoration)Figure3.33 Dens evaginatus: cropped panoramic radiograph.Elongated body of tooth with apicallypositioned furcation and shorter roots Figure3.34 Taurodontic first and second molars: cropped panoramic radiograph. 46 Atlas of Oral and Maxillofacial Radiology3.14 Fusion (Figures 3.35 and3.36)• Union of two normally separate tooth germs, to varying extents.• More common in the deciduous dentition.• More commonly associated with anterior teeth.Radiological features• Appearance of the two fused teeth varies depending on the stage and anatomic relationship.• Effectively, one tooth is absent. Rarely, there may be fusion of a normal tooth with a supernumerary tooth.Differential diagnosisKey radiological differencesGemination No missing teeth.Large appearance of the fused root.Note the residual cleft at the incisal edge, related to the incomplete fusion Figure3.35 Fusion 33 and 32: cropped panoramic radiograph.Communicationof the root canalsof both teeth(a) (b)(c) (d)Figure3.36 Fusion 22 and 23: axial (a–c) and surface‐rendered (d) CBCT images. Anomalies Related totheTeeth 473.15 Gemination (Figure 3.37)• Incomplete division of a single tooth bud, to varying extents.• More common in the deciduous dentition.Radiological features• Appearances vary depending on the degree of division.Differential diagnosisKey radiological differencesFusion One tooth is absent, unless there is fusion with a supernumerary tooth.3.16 Concrescence (Figure 3.38)• The joining of roots of normally separate teeth with cementum.• Most commonly affects the maxillary molars.• May interfere with tooth eruption.• Extraction of these teeth can be challenging.Radiological features• Definite identification of concrescence with 2D intraoral and panoramic radiography is difficult.• CBCT or MDCT is more accurate; absence of the periodontal ligament space is often a key feature. ◦However, it is sometimes difficult to fully exclude root contact with no cemental bridging, where the periodontal ligament space is present but extremely narrow and subresolution.Differential diagnosisKey radiological differencesFusion Can be difficult to differentiate when fusion is limited to the roots. It is difficult to radiologically identify whether the roots are connected with cementum (concrescence) or dentin (fusion).24 with two crowns, the distalbeing smaller. Note the singleroot with a bifurcate root canalFigure3.37 Gemination: corrected sagittal CBCT image.Continuity of the roots (a) (b)Figure3.38 Concrescence 27 and 28: corrected sagittal (a) and surface-rendered (b) CBCT images. 48 Atlas of Oral and Maxillofacial Radiology3.17 Amelogenesis imperfecta (Figure 3.39)• Inherited abnormal enamel formation not associated with other diseases.• Related to malfunction of the proteins which form the largely mineral content of enamel.• Many variants with variable enamel abnormalities. Four main types have been described: hypoplasia, hypomaturation, hypocalcification and hypomaturation/hypocalcification. The clinical appearances are well described.• Rare.• May be more susceptible to caries.Radiological featuresCompared with normal enamelHypoplasia Thinner but normal density. Flatter occlusal surfaces, especially when fully erupted (attrition), contribute to a square appear-ance of the crowns. Focal lucent defects may be seen. The anterior teeth may dem-onstrate the ‘picket fence’ appearance.Hypomaturation Normal thickness but decreased density, usually isodense with dentin. Post erup-tion attrition and enamel fractures are often seen.Hypocalcification Normal thickness but decreased density, hypodense to dentin. Post eruption attrition and enamel fractures are often seen.Hypomaturation/hypocalcificationUsually isodense with dentin. The enamel may be thin.All four types The dentin and the roots are normal. Pulpal obliteration (opacification) may occur when there is severe attrition.Differential diagnosisKey radiological differencesDentinogenesis imperfectaBulbous crowns and narrow roots are features of dentinogenesis imperfecta.The enamel isnot visualised.Square appearanceof the crowns notedFigure3.39 Amelogenesis imperfecta: cropped panoramic radiograph. Anomalies Related totheTeeth 493.18 Dentinogenesis imperfecta (Figure 3.40)• Hereditary abnormal dentin formation.• Three types (types I, II and III), each associated with specific genetic defects.• Can be associated with osteogenesis imperfecta (type I).• Clinical appearances are well described.• Dental restorative management is often challenging.Radiological features• Narrow cervical aspect of the crown, resulting in a bulbous crown appearance.• There is often substantial attrition of erupted teeth.• Usually short and narrow roots.• Varying degrees of pulpal obliteration (opacification), although some may demonstrate large pulp chambers early in development.Differential diagnosisKey radiological differencesDentin dysplasia Can be similar in appearance.Type I dentin dysplasia: presence of crescent-shaped pulp morphology favours dentin dysplasia.Type II dentin dysplasia: bulbous crown morphology is a feature of dentinogenesis imperfecta.Bulbous crown appearances. Marked pulpal opacificationFigure3.40 Dentinogenesis imperfecta: cropped panoramic radiograph. 50 Atlas of Oral and Maxillofacial Radiology3.19 Dentin dysplasia (Figures 3.41 and3.42)• Hereditary dentin abnormality.• Similar appearance to dentinogenesis imperfecta but rarer.• Two types: type I (radicular) and type II (coronal).• There may be misalignment of teeth and abnormal exfoliation.Radiological features• Type I (radicular): ◦Short and/or abnormal (often conical) root morphology. Usually normal crown morphology. ◦Pulps are largely obliterated (opacified) pre‐eruption. Aresidual crescent‐shaped pulp chamber may be seen. ◦Higher risk of non‐caries‐related periapical inflammatory lesions.• Type II (coronal): ◦Normal roots. Usually normal crown morphology. ◦Obliteration (opacification) of the pulp occurs post eruption. ◦‘Thistle tube’ pulp morphology of the permanent teeth (usually single‐rooted teeth) may be seen, sometimes with pulp stones. ◦Higher risk of non‐caries‐related periapical inflammatory lesions.Differential diagnosisKey radiological differencesDentinogenesis imperfectaCan be similar in appearance.Type I dentin dysplasia: presence of crescent-shaped pulp morphology favours dentin dysplasia.Type II dentin dysplasia: bulbous crown morphology is a feature of dentinogenesis imperfecta.Opacificationand reductionin the size ofcoronal pulpchambers andthe root canalsFigure3.41 Dentin dysplasia: cropped panoramic radiograph.Opacification and reduction in the size of the pulp chambers, some demonstrating ‘thistle tube’ morphology. Decrease in the dimension of the root canals Figure3.42 Dentin dysplasia: cropped panoramic radiograph. Anomalies Related totheTeeth 513.20 Secondary andtertiary dentin (Figures 3.43 and3.44)• Secondary dentin is considered as the physiological continued laying down of dentin post completion of root development.• Tertiary dentin (reparative or sclerotic dentin) usually refers to the dentin which is laid down as a response to a specific stimulus, e.g. caries.Radiological features• Secondary and tertiary dentin are isodense with primary dentin (dentin formed during tooth development).• Secondary dentin formation reduces the size of the pulp. Thepulp morphology is generally maintained but the pulp chamber often appears to be relatively smaller than the root canals with age, especially the pulp horns.• The morphology of tertiary dentin can vary, depending on the stimulus, usually altering the morphology of the pulp chamber.Differential diagnosisKey radiological differencesPulpal sclerosis (diffused pulpal calcifications)With age, substantial secondary dentin formation (± tertiary dentin) may almost or completely obliterate the pulp and this can appear similar to pulpal sclerosis, especially on intraoral and panoramic radiography.Reduction in the size of rootcanals in the visualised teeth(a) (b)Figure3.43 Secondary dentin: axial (a) and corrected sagittal (b) CBCT images.Reduction in the sizeof pulp chamber and rootcanals of 34. Note the patentroot canals of the other visualised teethComplete opacification of the 21pulp chamber and root canal isprobably related to tertiary dentin formation although severe pulpal sclerosis (diffused pulpalcalcifications) can appear similar. The root canals of the other visualised teeth demonstrate normal root canal calibre(a) (b)(c) (d)Figure3.44 Tertiary dentin of two different cases: axial (a,c), coronal (b) and sagittal (d) CBCT images. 52 Atlas of Oral and Maxillofacial Radiology3.21 Pulp stones (Figure 3.45)• Relatively common calcific foci within the pulp.• Generally considered idiopathic, possibly a normal variant.• May be seen in type II dentin dysplasia.Radiological features• Opaque foci within the pulp chamber and/or root canal. Variable in numbers and morphology.• Many pulp stones are subresolution or insufficiently dense to be identified radiologically.Differential diagnosisKey radiological differencesPulpal sclerosis (diffused pulpal calcifications)Multiple extremely small pulp stones can appear similar to pulpal sclerosis, especially on intraoral and panoramic radiography.Enamel pearl Can appear similar on intraoral and panoramic radiography if the enamel pearl is projected over the pulp. The enamel pearl is denser.Opaque foci withinthe pulp chambersof many teethFigure3.45 Pulp stones: cropped panoramic radiograph. Anomalies Related totheTeeth 533.22 Hypercementosis (Figures 3.46 and3.47; see also Figure 5.39)• Non‐neoplastic excessive deposition of cementum over tooth roots.• Most cases are idiopathic.• May be seen in association with increased/decreased occlusal loading, chronic periapical inflammatory lesions, Paget dis-ease and hyperpituitarism.• Asymptomatic and the hypercementosis itself does not require treatment. A primary cause, if present, may require management.• Extraction can be more difficult.Radiological features• Bulbous enlargement of the root with preservation of the per-iodontal ligament space. Occasionally irregular morphology.• The excessive cementum often appears slightly hypodense to dentin.Differential diagnosisKey radiological differencesOther opaque entitiesMay be projected over a root on 2D intraoral and panoramic radiography. CBCT or MDCT may be required to clarify.Ankylosis It can be difficult to identify the presence and location of the periodontal ligament space. Therefore, it can be difficult to differentiate hypercementosis from ankylosis with dense per-iradicular bone. CBCT or MDCT may be useful although the periodontal ligament space may bepresent but thin and subresolution.Prominent bulbous radicular appearance isodense with cementum. Note the classicallypreserved periodontal ligamentspace surrounding this prominenceFigure3.46 Hypercementosis 38: corrected sagittal MDCT image.Bulbous prominencesof the posterior toothroots with slightly variable morphologyFigure3.47 Hypercementosis posterior teeth: cropped panoramic radiograph.

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