Increased occurrence of dental anomalies associated with infraocclusion of deciduous molars.

OBJECTIVE: To test the null hypothesis that there is no relationship between infraocclusion and the occurrence of other dental anomalies in subjects selected for clear-cut infraocclusion of one or more deciduous molars. MATERIALS AND METHODS: The experimental sample consisted of 99 orthodontic patients (43 from Boston, Mass, United States; 56 from Jerusalem, Israel) with at least one deciduous molar in infraocclusion greater than 1 mm vertical discrepancy, measured from the mesial marginal ridge of the first permanent molar. Panoramic radiographs and dental casts were used to determine the presence of other dental anomalies, including agenesis of permanent teeth, microdontia of maxillary lateral incisors, palatally displaced canines (PDC), and distal angulation of the mandibular second premolars (MnP2-DA). Comparative prevalence reference values were utilized and statistical testing was performed using the chi-square test (P < .05) and odds ratio. RESULTS: The studied dental anomalies showed two to seven times greater prevalence in the infraocclusion samples, compared with reported prevalence in reference samples. In most cases, the infraoccluded deciduous molar exfoliated eventually and the underlying premolar erupted spontaneously. In some severe phenotypes (10%), the infraoccluded deciduous molar was extracted and space was regained to allow uncomplicated eruption of the associated premolar. CONCLUSION: Statistically significant associations were observed between the presence of infraocclusion and the occurrence of tooth agenesis, microdontia of maxillary lateral incisors, PDC, and MnP2-DA. These associations support a hypothesis favoring shared causal genetic factors. Clinically, infraocclusion may be considered an early marker for the development of later appearing dental anomalies, such as tooth agenesis and PDC.

Concomitant occurrence of canine malposition and tooth agenesis: evidence of orofacial genetic fields.

Certain discrete malpositions of the human canine tooth and agenesis of at least 1 tooth (hypodontia) are abnormalities known to occur together frequently. This study examines the specificity of tooth-agenesis sites associated with the occurrence of 3 unambiguous canine malpositions: palatally displaced canine (PDC; n = 58), mandibular lateral incisor-canine transposition (Mn.I2.C; n = 60), and maxillary canine-first premolar transposition (Mx.C.P1; n = 43). A fourth sample was formed from 4 cases of combined occurrence of PDC and Mn.I2.C, the only combination-phenotype noted among the 161 subjects. Oral panoramic radiographs were used to identify agenesis of at least 1 third molar (M3), mandibular second premolar (MnP2), and maxillary lateral incisor (MxI2)-the 3 most frequently absent tooth types among people of European descent. PDC and Mn.I2.C transposition appear to be associated with significantly increased M3 agenesis (P <.01), representing the posterior orofacial field, and Mx.C.P1 transposition appears to be associated with conspicuously elevated MxI2 agenesis (P <.001), representing the anterior orofacial field. MnP2 agenesis appears to represent an intermediate field, found in significantly elevated frequencies with all 3 canine positional anomalies. Coupling these new clinical findings with results from recent molecular studies, we suggest that transcription factors such as MSX1 and PAX9, which have been associated with agenesis of molars, might be involved in the genetic control of Mn.I2.C transposition and PDC, tooth malpositions connected here with the specific expression of posterior-field (M3) hypodontia.

Malposition of unerupted mandibular second premolar associated with agenesis of its antimere.

Aberrant tooth positions--such as infraocclusion, mesially ectopic maxillary first molar, palatally displaced canine, tooth transposition, and tooth rotation--are gaining attention as variables in a putative, genetically related pattern of dental anomalies. This study, using panoramic roentgenograms, was undertaken to measure the angular position of the unerupted mandibular second premolar (MnP2) in children. The experimental subjects were 17 children with an unerupted MnP2 and agenesis of the other MnP2, a likely indicator of site-specific genetic disturbance. An age/sex-matched control-reference group was similarly measured for comparison. The hypothesis tested was that the unerupted, developing MnP2 teeth in the experimental subjects would show measurably greater malpositions than those of the control sample. The results indicated a 10 degrees increase in distoangular inclination for the unerupted MnP2 in the agenesis sample; this was a highly significant difference statistically (P = .003), compared with the MnP2 inclinations in the control sample. These findings, associating exaggerated distoangular malposition of the unerupted MnP2 in children with agenesis of the contralateral MnP2, identify a new phenotype of dental developmental disturbance to add to the accumulated evidence supporting shared genetic mechanisms for dental anomaly patterns.