PR5 Histopathology of Dental Development Defects

Types of Amelogenesis Imperfecta (AI)

Hypoplastic: deposition of enamel matrix is defective

• (too smooth or rough enamel)

Hypocalcified: defect in the mineralization of matrix

• (Soft enamel)

Hypomaturated: maturation of enamel is affected

• (too brittle enamel)

Dentinogenesis Imperfecta (DGI)

dentin defect involving dentine sialophosphoprotein (DSPP)

affects both primary and permanent teeth

(more common in primary dentition; and incisor and first molars of the permanent dentition)

(less common in the 2nd and 3rd molars of the permanent dentition)

Dentin Dysplasia Type I

autosomal dominant with prevalence of 1:100000

radicular dentin dysplasia (rootless teeth)

causes increased tooth movement and exfoliation

Dentin Dysplasia Type II

coronal dentin dysplasia; variation of dentinogenesis imperfecta

affects primary (discolouration) and permanent (no discolouration) teeth

Regional odontodysplasia (Ghost Teeth)

localized and nonhereditary developmental dental defects

often associated with other conditions

affects primary and permanent dentition casing affected teeth to fail to erupt

Double Teeth/Connate Teeth

Types:

Gemination

Fusion

Concrescence

Gemination

single tooth bud where the crown of the tooth is bifurcated into two bifid crowns

affects primary and permanent teeth

generally affects maxillary incisors and canines

Fusion

two tooth buds fuse into one single tooth

generally affects mandibular teeth

Concrescence

two developed adjacent teeth are fused at the root by cementum

generally affects posterior maxillary teeth

can be Developmental (entire roots are fused) or Post-inflammatory (only tips of the root are fused)

Types of accessory cusps

Cusp of Carabelli

Talon Cusp

Dens evaginatus

Cusp of Carabelli

extra mesiolingual cusp on the maxillary molar (near the palate)

Talon cusp

extra cusp on lingual side of anterior teeth (more common in the maxillary incisors)

Dens evaginatus

cusp-like elevation on lingual ridge of the buccal cusp of premolars (more common) and molars

generally bilateral and found in maxillary teeth

Enamel Pearl

pearl shaped structure on root of upper permanent molars

Cervical enamel extensions

extra enamel bleeding into the root of mandibular molars on the buccal surface

common in the the 3rd molar

Taurodontism

enlargement of the pulp chamber

3 classifications: mild, moderate, severe

can be unilateral or bilateral

can be associated with AI or down syndrome

Dilaceration

unusual bending of the root or crown

often caused by injury or due to location (adjacent to cyst/tumor)

affects impaction

more common in mandibular third molars and anterior teeth