Prevalence of tooth agenesis and peg-shaped maxillary lateral incisor associated with palatally displaced canine (PDC) anomaly

Tooth anomalies associated with failure of eruption of first and second permanent molars

The occurrence of tooth anomalies in association with failure of the first and second molars to erupt was assessed in a sample of 1520 nonsyndromic subjects with uncrowded dental arches (mean age, 14 years 4 months) and compared with the prevalence rate calculated in a matched control group of 1000 subjects. The tooth anomalies examined included infraocclusion of deciduous molars, palatal displacement of maxillary canines, rotation of maxillary lateral incisors, aplasia of second premolars, and small size of maxillary lateral incisors. Associations among arrested eruption of first and second permanent molars and anomalies in tooth eruption and position (infraoccluded deciduous molars, palatally displaced canines, rotated maxillary lateral incisors) were highly significant (P <. 001). No significant association was found among the occurrence of molar eruption disturbances, aplasia of premolars, and small-sized laterals. These findings point to a common biologic cause for the appearance of failure of eruption of molar teeth and other disturbances in tooth eruption and position, most likely under genetic influence.

Adequacy of maxillary dental arch width in patients with palatally displaced canines

This study investigates maxillary dental arch width in subjects with palatally displaced canines. Pretreatment dental casts of orthodontic patients with one or both maxillary canines palatally displaced (n = 31; male, 10; female, 21) were collected. This sample was matched according to sex and age with pretreatment dental casts from unaffected orthodontic patients. Arch widths were recorded between the maxillary first premolars and between the maxillary first molars. Interpremolar arch width and intermolar arch width comparisons between the sample with palatally displaced canines and the reference sample showed no statistically significant differences in their means, thus indicating that there was no statistically significant difference in the anterior and posterior arch width between the affected subjects and the control subjects. Thus, affected patients exhibit adequacy of maxillary dental arch width. This evidence refutes earlier conclusions that deficiency in maxillary transverse arch width is an associated contributing factor in the genesis of the anomaly of palatally displaced canines. Clinically, adequacy of dental arch width helps explain the "nonextraction" diagnostic appearance of most of these patients when they present for treatment.

Eruption of the permanent upper canine: a radiologic study

The early detection of eruptive anomalies of the upper canine requires an understanding of its normal eruptive pattern. We studied this pattern in terms of upper canine inclination and its relation to the lateral incisor, on the basis of the panoramic radiographic records of 305 children aged 4 to 12 years. The study sample comprised 554 maxillary canines in the oral pre-emergence phase of eruption. Subject age, sex, inclination of the canine (CI), its relation to the lateral incisor (RCLI), and development of the lateral incisor (DLI) were evaluated. The results show that the canine erupts, increasing its inclination mesially until a maximum is reached, at about 9 years of age, after which the tooth begins to progressively upright itself. The individual variability of the degree of CI at a given age is considerable. In the initial stages, the RCLI is most commonly characterized by overlapping, a situation rarely seen in the final stages. The DLI effectively discriminates both periods, because when DLI is incomplete, more than half of the cases have an overlapping RCLI. In contrast, when the DLI is complete, this overlapping is seen in only 7% to 11% of the cases. This variable therefore increases the capacity to detect a possible eruptive anomaly at an early stage. In patients with complete DLI and overlapping RCLI, particularly when associated with other clinical signs such as the nonpalpation of the cuspid bulge in the alveolar process, the presence of dental agenesis, ankylosis, malformations, or ectopic eruptions, extraction of the primary canine is advised to prevent impaction.