Developmental abnormalities

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Chapter 24

Developmental abnormalities

Introduction

There are many developmental abnormalities that can affect the teeth and facial skeleton. In most cases, clinicians need little more than to be able to recognize these abnormalities – this recognition being based on both the clinical and radiographic findings. Therefore, the bulk of this chapter is designed like an atlas to show examples of some of the more common and important abnormalities that have characteristic radiographic features. A broad classification of the main conditions is also included.

Two important developmental anomalies are often encountered: unerupted mandibular wisdom teeth and malpositioned maxillary canines. These two topics are described in more detail.

Classification of developmental abnormalities

Developmental anomalies of the maxillofacial region are usually classified into:

• Anomalies of the teeth

• Skeletal anomalies.

Anomalies of the teeth

These include abnormalities in:

Abnormalities in number

Missing teeth

• Localized anodontia or hypodontia – usually third molars, upper lateral incisors or second premolars

• Anodontia or hypodontia associated with systemic disease – e.g. Down’s syndrome, ectodermal dysplasia.

Additional teeth (hyperdontia)

• Localized hyperdontia

– Supernumerary teeth

– Supplemental teeth

• Hyperdontia associated with specific syndromes, e.g. cleidocranial dysplasia, Gardner’s syndrome.

Abnormalities in structure

Abnormalities in shape

Anomalies affecting whole teeth

• Fusion – two teeth joined together from the fusion of adjacent tooth germs

• Gemination – two teeth joined together but arising from a single tooth germ

• Concrescence – two teeth joined together by cementum

• Dens-in-dente (invaginated odontome) – infolding of the outer surface of a tooth into the interior usually in the cingulum pit region of maxillary lateral incisors.

Anomalies affecting the crowns

• Extra cusps

• Congenital syphilis

– Hutchinson’s incisors – crowns small, screwdriver or barrel-shaped, and often notched

– Moon’s/mulberry molars – dome-shaped or modular

• Tapering pointed incisors – ectodermal dysplasia.

Anomalies affecting roots and/or pulp canals

• Number – additional roots, e.g. two-rooted incisors, three-rooted premolars or four-rooted molars

• Morphology, including:

– Bifid roots

– Excessively curved roots

– Dilaceration – sharp bend in the root direction

– Taurodontism – short, stumpy roots and longitudinally enlarged pulp chambers

• Pulp stones – localized or associated with specific syndromes, e.g. Ehlers–Danlos (floppy joint syndrome)

• Cementoma (see odontogenic tumours in Ch. 27).

Odontomes

• Compound odontome – made up of one or more small tooth-like denticles (see Ch. 27)

• Complex odontome – complex mass of disorganized dental tissue (see Ch. 27)

• Enameloma/enamel pearl.

Abnormalities in position

Delayed eruption

• Local causes

– Loss of space

– Abnormal crypt position – especially and

– Overcrowding

– Additional teeth

– Retention of deciduous predecessor

– Dentigerous and eruption cysts

• Systemic causes

– Metabolic diseases, e.g. cretinism and rickets

– Developmental disturbances, e.g. cleidocranial dysplasia

– Hereditary conditions, e.g. gingival fibromatosis and cherubism.

Other positional anomalies

• Transposition, two teeth occupying exchanged positions

• Wandering teeth, movement of unerupted teeth for no apparent reason (distal drift)

• Infraocclusion, second deciduous molars apparently descend into the jaws. These teeth in fact remain in their original position while the adjacent alveolar bone grows normally. As these teeth appear to submerge the original term for this positional anomaly was submersion.

Skeletal anomalies

These include:

• Abnormalities of the mandible and/or maxilla

• Other rare developmental diseases and syndromes.

Abnormalities of the mandible or maxilla

Micrognathia

• True micrognathia – usually caused by bilateral hypoplasia of the jaw or agenesis of the condyles

• Acquired micrognathia – usually caused by unilateral early ankylosis of the temporomandibular joint.

Macrognathia (prognathism)

• Genetic

• Relative prognathism – mandibular/maxillary disparity

• Acquired, e.g. acromegaly owing to excessive growth hormone from a pituitary tumour.

Other mandibular anomalies

• Condylar hypoplasia

• Condylar hyperplasia

• Bifid condyle

• Coronoid hyperplasia.

Cleft lip and palate

• Cleft lip

– Unilateral, with or without alveolar ridge

– Bilateral, with or without alveolar ridge

• Cleft palate

– Bifid uvula

– Soft palate only

– Soft and hard palate

• Clefts of lip and palate (combined defects)

– Unilateral (left or right)

– Cleft palate with bilateral cleft lip.

Localized bone defects

• Exostoses (see Ch. 27)

– Torus palatinus

– Torus mandibularis

• Idiopathic bone cavities (see Ch. 26)

– Stafne’s bone cavity.

Other rare developmental diseases and syndromes

• Cleidocranial dysplasia (see Ch. 28)

• Gorlin’s syndrome (nevoid basal cell carcinoma syndrome) (see Ch. 26)

• Eagle syndrome

• Crouzon syndrome (craniofacial dysostosis)

• Apert syndrome

• Mandibular facial dysostosis (Treacher Collins syndrome).

Typical radiographic appearances of the more common and important developmental abnormalities

Fig. 24.1 Panoramic radiograph showing hypodontia in a patient with ectodermal dysplasia. Numerous teeth are missing.

Fig. 24.2 Periapical showing a supernumerary or mesiodens (arrowed) between .

Fig. 24.3 Oblique lateral showing two supplemental lower premolars (arrowed) and a developing .

Fig. 24.4 Right bitewing showing the enamel defects of amelogenesis imperfecta (arrowed) in both the deciduous and permanent dentitions.

Fig. 24.5 Periapical of maxillary premolars and molars showing the defects of dentinogenesis imperfecta. Note the near obliteration of the pulp chamber (black arrow) and loss of the overlying enamel (white arrows).

Fig. 24.6 Bitewing showing so-called *shell teeth* – a type of dentinogenesis imperfecta. The enamel is essentially normal but there is almost no dentine and the pulp chambers are very large (arrowed).

Fig. 24.7 Periapical showing a microdont (arrowed).

Fig. 24.8 Periapical of showing the typical gnarled enamel defects of a Turner tooth (arrowed), caused by previous infection of the deciduous predecessor.

Fig. 24.9 Periapical showing fusion of (arrowed).

Fig. 24.10 Part of a panoramic radiograph showing a macrodont (arrowed).

Fig. 24.11 A Periapical showing gemination of (arrowed). B Cross-sectional cone beam CT image showing gemination of (arrowed).

Fig. 24.12 Periapical suggesting concrescence of (arrowed). Note it is not possible to be certain simply from the radiograph that are joined together with cementum.

Fig. 24.13 Periapical showing a dens-in-dente or invaginated odontome involving (open arrows). There is an associated periapical area of infection (solid arrows) – a common occurrence with dens-in-dente.

Fig. 24.14 Congenital syphilis. A Periapical of maxillary incisors and canine showing Hutchinson’s teeth. Note the tapering screwdriver-shaped crowns (solid arrows) and the incisal edge notching (open arrow). B Bitewing showing Moon’s/mulberry molars. Note the dome-shaped, nodular appearance of the molars (arrowed).

Fig. 24.15 Periapical showing a bifid lower premolar root (arrowed).

Fig. 24.16 Periapical showing a three-rooted lower first molar (arrowed) (right).

Fig. 24.17 Periapical showing the typical tapering pointed incisor teeth (arrowed) of ectodermal dysplasia.

Fig. 24.18 A Periapical showing a dilacerated with a near right angle bend in the root (arrowed). B *Surface rendered*

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Essentials of Dental Radiography and Radiology

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Developmental abnormalities

Developmental abnormalities

Introduction

Classification of developmental abnormalities

Anomalies of the teeth

Abnormalities in number

Missing teeth

Additional teeth (hyperdontia)

Abnormalities in structure

Genetic defects

Acquired defects

Abnormalities in size

Abnormalities in shape

Anomalies affecting whole teeth

Anomalies affecting the crowns

Anomalies affecting roots and/or pulp canals

Odontomes

Abnormalities in position

Delayed eruption

Other positional anomalies

Skeletal anomalies

Abnormalities of the mandible or maxilla

Micrognathia

Macrognathia (prognathism)

Other mandibular anomalies

Cleft lip and palate

Localized bone defects

Other rare developmental diseases and syndromes

Typical radiographic appearances of the more common and important developmental abnormalities

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