Malposition Of Teeth With Or Without Hypodontia/oligodontia

Description

Malpositioning, or ectopic placement, of teeth is believed to result from a disturbance of the tooth developmental structure. Various forms of the disorder tend to be associated with one another and with hypodontia. It is important to recognize any associations of tooth anomalies as early diagnosis of developmental disturbance in a single tooth may reveal a potential risk of future position or eruption disturbances of other teeth and thus allow early intervention (Bjerklin et al., 1992).

Clinical Features

In each of 4 Finnish kindreds, Svinhufvud et al. (1988) found a typical type of malposition of cuspids (canine teeth): palatal displacement of upper lateral incisor(s) and/or cuspid(s) in kindred A; labial displacement of upper cuspids, sometimes also lower cuspids, in kindred B; rotated upper cuspid(s) in kindred C; and labial cuspid(s), with rotated, malpositioned, or missing second bicuspids in kindred D. In each kindred other anomalies occurred, such as malposition, malformation, or hypodontia of upper lateral incisors, second bicuspids, and lower central incisors.

Alexandrakis et al. (2000) described 2 patients with nasolacrimal duct obstruction (NLDO), presenting as epiphora, caused by ectopic eruption of teeth. Surgical removal of the ectopic teeth compressing the nasolacrimal duct resulted in resolution of the lacrimal drainage obstruction. The authors concluded that ectopic eruption of teeth should be added to the differential diagnosis of NLDO.

Inheritance

Bjerklin et al. (1992) evaluated and provided follow-up of 4 groups of children selected by a disturbance of tooth development. Ninety-two had ectopic eruption of maxillary first permanent molars; 93 had infraocclusion of primary molars; 91 had ectopic eruption of maxillary canines; and 97 aplasia of premolars. Among all children, 69 to 79% had only a single type of disturbance. There was an additional disturbance in 18 to 28% of children, and 2 additional disturbances in 2 to 3% of children. Chi-square contingency testing showed that infraocclusion of primary molars and aplasia of premolars exhibited a higher prevalence in both directions compared to the expected population prevalence. Ectopic eruption of maxillary canines showed a significantly higher prevalence than expected in all the other 3 groups. Finally, ectopic eruption of maxillary first permanent molars increased the likelihood of infraocclusion of primary molars. Bjerklin et al. (1992) concluded that there is a common, presumably hereditary, etiology for the 4 conditions. This would be consistent with different manifestations of a single syndrome with incomplete penetrance for each manifestation.

Canine displacement can occur in either of 2 directions: palatal or facial. Palatal displacement more often results in maxillary canine impaction, which occurs in 1 to 3% of the population. Peck et al. (1994) provided a review of published papers that found that palatal canine displacement occurs with other dental anomalies, such as tooth agenesis or other ectopically positioned teeth, can occur bilaterally, and has been demonstrated in families. Differences in frequencies of the trait between population groups have also been observed, with relatively higher expression among Europeans. All of these findings suggested a genetic component to palatal canine displacement.

Pirinen et al. (1996) found that 38 (36%) of 106 Finnish probands with palatal displacement of the canine also had congenital absence of permanent teeth, or hypodontia, which was 4.5 times the prevalence of hypodontia in the general population. Among these probands, family history allowed for the construction of 35 informative pedigrees. Autosomal dominant inheritance of missing teeth was noted in 13 of 35 pedigrees, and hypodontia was noted in about 20% of both first and second-degree relatives of probands with palatally impacted canines. Six of 35 pedigrees had a palatally impacted canine in several generations. The prevalence of this anomaly was 4.9% in the studied group, which was 2.5 times that of the general population. Pirinen et al. (1996) concluded that palatally displaced canine belongs to a spectrum of dental anomalies related to incisor-premolar hypodontia.

In Malta, the prevalence of ectopic canines is 4 to 5.5%, possibly due to a founder effect. In a study of 63 affected Maltese probands and their families, Camilleri et al. (2008) found evidence for a single autosomal dominant gene with incomplete penetrance and variable expression. However, only 2 of 7 pairs of monozygotic twins were concordant for ectopic canines, suggesting that environmental or epigenetic factors may also be important. There was a female predominance (F:M of 1.89), which had been noted in earlier studies (Peck et al., 1994).