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A clinical and statistical study of etiologic aspects related to associated tooth anomalies in number, size, and position.

BACKGROUND
The study was aimed to reveal patterns of association among five types of dental anomalies (aplasia of second premolars, small size of maxillary lateral incisors, infraocclusion of primary molars, ectopic eruption of first molars, and palatal displacement of maxillary canines) in an untreated orthodontic population, aged 7-14 years.


METHODS
The prevalence of associated tooth anomalies in five groups of 100 subjects each and characterized by the constant presence of one primarily diagnosed dental anomaly was compared to the prevalence for the examined dental anomalies in a control group of 1,000 subjects, deriving from a common initial sample of 4,850 subjects.


RESULTS
Significant reciprocal associations (p < 0.008) were found among four dental anomalies (aplasia of second premolars, small size of maxillary lateral incisors, infraocclusion of primary molars, and palatal displacement of maxillary canines), suggesting a common genetic origin for these conditions. Ectopic eruption of first molars appeared to be a rather separate pathological entity with respect to all other examined tooth anomalies.


CONCLUSIONS
The statistically demonstrated existence of associations among different tooth anomalies is clinically relevant, since the diagnosis of those anomalies that appear earlier may indicate potential risk for later developing tooth and eruption disturbances.