Objective The purpose of this study was to investigate the possible absence of teeth in the postcanine region of the upper jaw of the unoperated adult cleft patient. Method The study was performed on 266 dental casts of fully unoperated adult cleft patients. The patients were divided into four groups according to the type of the cleft: unilateral cleft lip and alveolus, unilateral cleft lip and palate, bilateral cleft lip and alveolus, and bilateral cleft lip and palate. Results No absence of permanent teeth in the canine and postcanine area of the upper jaw could be found. Conclusion The results are in contradiction with the established hypothesis that absence of teeth outside the cleft area of the maxilla is due to an unknown congenital factor. On the contrary, the findings support the hypothesis that surgery for the closure of the hard palate in early childhood is the most important etiological factor for the absence of teeth outside the cleft area in the early operated cleft patient. The superficial position of the tooth germs (at the time of the palatal surgery), especially those of the premolars, supports this hypothesis.

The results are in contradiction with the established hypothesis that absence of teeth outside the cleft area of the maxilla is due to an unknown congenital factor. On the contrary, the findings support the hypothesis that surgery for the closure of the hard palate in early childhood is the most important etiological factor for the absence of teeth outside the cleft area in the early operated cleft patient. The superficial position of the tooth germs (at the time of the palatal surgery), especially those of the premolars, supports this hypothesis.

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