Developmental Anomalies of Teeth

Number, size and shape

Anomaly	Key facts
Hypodontia / oligodontia / anodontia	Oligodontia = 6 or more missing (excluding third molars); commonly missing: third molars, then mandibular second premolars and maxillary lateral incisors (order varies by source); ectodermal dysplasia gives hypodontia with conical teeth
Hyperdontia	Mesiodens (maxillary midline) is the most common supernumerary; multiple supernumeraries suggest cleidocranial dysplasia (RUNX2) or Gardner syndrome
Microdontia	Peg lateral incisor is the classic localized form
Gemination	One tooth germ tries to divide: a bifid crown with one root and canal; tooth count is normal when the double tooth is counted as one
Fusion	Two germs join at the dentin: tooth count is one less (unless fused with a supernumerary); may have separate canals
Concrescence	Two formed teeth joined by cementum only, most often maxillary molars; matters for extraction
Dilaceration	Sharp bend in the root or crown, often after trauma during development
Taurodontism	Tall pulp chamber with apically displaced furcation; associated with Klinefelter and some syndromes
Dens invaginatus	Enamel-lined infolding, usually the maxillary lateral incisor; early pulp necrosis risk
Dens evaginatus / talon cusp	Extra cusp on premolar occlusal surfaces or anterior lingual surfaces; may contain pulp, so fracture or wear can expose it
Enamel pearl	Small ball of enamel in a furcation, usually maxillary molars; plaque trap

Condition	Teeth	Radiograph
Amelogenesis imperfecta (hypoplastic, hypomaturation, hypocalcified)	Enamel thin, pitted, soft or discolored; all teeth of both dentitions	Enamel thin or as dense as dentin; normal pulps and roots
Dentinogenesis imperfecta (DSPP; type I occurs with osteogenesis imperfecta)	Amber to gray-blue opalescent teeth; enamel chips off	Bulbous crowns, cervical constriction, short roots, pulps obliterated
Dentin dysplasia type I (radicular)	Normal-looking crowns, mobile teeth	Short or absent roots ('rootless'), crescent-shaped pulp remnants, periapical lucencies
Dentin dysplasia type II (coronal)	Primary teeth look like DI; permanent teeth near normal	Thistle-tube pulp chambers with pulp stones
Regional odontodysplasia	One quadrant, often maxillary anterior	'Ghost teeth' with thin enamel and dentin and wide pulps
Turner tooth	One permanent tooth (often a premolar) with hypoplasia	Caused by infection or trauma of the primary predecessor
Congenital syphilis	Hutchinson incisors (screwdriver-shaped, notched) and mulberry molars

Calling a joined tooth fusion when the tooth count is normal: that is gemination (unless a supernumerary fused).
Expecting pulp obliteration in amelogenesis imperfecta: pulps are normal; DI obliterates them.
Linking dentinogenesis imperfecta type I to an enamel gene: it accompanies osteogenesis imperfecta (type I collagen).
Treating a talon cusp casually: it may contain a pulp horn.

Pick an answer to see right away whether it is correct and why.

A double-crowned mandibular incisor is present and the tooth count is one fewer than normal. The most likely anomaly is:
Opalescent gray-blue teeth with bulbous crowns, short roots and obliterated pulps suggest:
Which radiographic feature best separates amelogenesis imperfecta from dentinogenesis imperfecta?
Multiple supernumerary teeth, delayed eruption and hypoplastic clavicles point to:
A mandibular second premolar has localized enamel hypoplasia after the primary second molar above it had a large abscess. This is a:

0 of 5 answered

Answer key: 1 B · 2 C · 3 A · 4 B · 5 B

Dental School Map · Original study material, written and checked by our team; always confirm clinical decisions against current guidelines.