The etiology of palatal displacement of maxillary canines.

OBJECTIVES: To test the hypothesis that palatal displacement of the maxillary canine is completely under genetic influence. DESIGN: A randomized controlled design studied cases affected by a severe expression of lateral incisor anomaly on one side and by milder expression of the same anomaly on the other. Comparison of frequency of occurrence of unilateral palatally displaced canine measured in each. Each side acted as control for the other within the same individual. SETTING AND SAMPLE POPULATION: The Departments of Orthodontics of the Universities of Jerusalem and Tel Aviv and in private practice. From approximately 12,000 consecutively treated patients, all those exhibiting an anterior maxilla with a missing lateral incisor on one side, a peg-shaped or reduced lateral incisor on the other, and a palatally displaced canine (n = 19). OUTCOME MEASURE: Missing lateral incisors, peg-shaped, and reduced lateral incisors (all genetically determined characters) have been shown to be associated with palatal displacement of the canine. The canine displacement is presumed by some authorities to be similarly genetically determined. If this is so, then the impacted canine should occur with equal frequency on either side in the patient with a missing lateral incisor on one side and a peg-shaped or reduced lateral incisor on the other. RESULTS: The canine aberration occurred far more frequently on the side of the diminutive lateral incisor. CONCLUSION: There is an environmental factor involved in the palatal displacement of maxillary canines.