Establishment of normal value of posterior arch length of adolescence in Chengdu / 华西口腔医学杂志

ABSTRACT

<p><b>OBJECTIVE</b>To investigate the development of third molar embryo and establish the normal value of posterior arch length of adolescence in Chengdu.</p><p><b>METHODS</b>The samples consisted of 40 males and 41 females with Class 1 dentitions, normal second molar occlusion, no history of orthodontic treatment, and good facial balance. Cephalometry and statistic analysis were conducted for all the subject.</p><p><b>RESULTS</b>The normal value of posterior arch length of maxilla in male was(16.52 +/- 2.35) mm and in female was(16.42 +/- 2.55) mm. The normal length of mandible was(13.00 +/- 2.44) mm in male and(12.43 +/- 2.18) mm in female. But statistic analysis showed no gender difference. Most of the third molar embryo had been formed and their tooth crowns had been calcified, the occurrence ratio was 84.0% in maxilla and 85.2% in mandible. Most of them located in the middle and inclined mesially.</p><p><b>CONCLUSION</b>The data obtained in this study will be valuable for our clinical practice and be helpful for the study concerning dento-facial growth and development.</p>