Agenesis of the lateral incisor on the non-cleft side may be considered as an incomplete form of bilateral cleft of the lip

Retrospective study of 500 Brazilian subjects with cleft lip and/or cleft palate but with no history of syndromic clefting. Presence of dental anomalies was recorded for each individual and included “tooth agenesis (including hypodontia and oligodontia), microdontia, supernumerary teeth, tooth malposition (rotation or inclination), impaction, shape anomalies, and transposition.” However, anomalies adjacent to the cleft area were not included because of the likelihood of them being a consequence of developmental anomalies at the cleft site. Control subjects were 500 healthy non-related individuals.

Literature has noted that “individuals with clefts present considerably more dental anomalies than do individuals without clefts, and, moreover, that severity of anomalies appears to be directly related to severity of the cleft.” The authors considered cleft phenotypes and associated dental anomalies to develop new definitions of cleft sub-phenotypes.

In the present study, individual with clefts were more likely to manifest dental anomalies than did control subjects. “The presence of multiple anomalies occurred most commonly in persons with complete and incomplete unilateral left cleft lip and palate.” “The absence of maxillary left lateral incisors was significantly associated with unilateral right clefts” whereas “right lateral incisors were most commonly absent with unilateral left clefts.”

The authors observed that “dental anomalies can be considered an extended phenotype for clefts.” They noted that “the consistent presence of dental anomalies on the opposite side of unilateral clefts, with preferential agenesis of the lateral incisor, leads us to believe that these specific unilateral clefts could be “unsuccessful” bilateral clefts, and should be considered carefully regarding the genetic etiology of different cleft types.”