Morphometric analysis of the primary and permanent dentitions in hemifacial microsomia: a controlled study

Hemifacial microsomia (HFM), a developmental abnormality involving the first and second branchial arches, is one of the most common craniofacial abnormalities. Although the general presentations of hemifacial microsomia--such as unilateral microtia, macrostomia, and hypoplasia of the mandibular ramus and condyle--are wellknown, the effects on the teeth are not well-documented. This study examined the primary and permanent tooth dimensions of dental casts of 50 hemifacial microsomia patients compared with those of 50 normal control patients matched for sex and dental status. The results showed that the mesiodistal dimensions of the mandibular second primary molar and the mandibular permanent first molar teeth on the affected side in hemifacial microsomia were significantly smaller compared with those of control teeth (p < 0.001). Furthermore, in the maxillary and mandibular first permanent molars and the maxillary and mandibular first and second primary molars, the teeth in the apparently "normal" side of hemifacial microsomia were also significantly reduced in the mesiodistal dimensions. Comparison of overall dimensions revealed that all primary and permanent molars in hemifacial microsomia were significantly smaller in the mesiodistal dimensions compared with control teeth. A general gradient effect was observed, with the most posterior tooth in each arch being the most severely affected and no effect being seen in the canines and the incisors. These findings suggest that the dental lamina in hemifacial microsomia is affected, and support the hypothesis that its pathogenesis involves an abnormality of the neural crest. Furthermore, these results also support the concept that hemifacial microsomia is a bilateral rather than a unilateral condition.