To survey molars roots separate degree and meaning explored

AIM:To survey molars roots separate degree and explore their physiological importance. METHODS: 400 molars from stomatological hospital were researched (maxillary first and second molars 200, mandibular first and second molars 200 ). The appearance of tooth was printed on papers with oil ink firstly. Then the line was drawn along dental root long axis. Finally the angle between two root axis lines was measured with protractor. The measures were counted and estimated. RESULTS: ①The angle between medical and distal buccal roots of the first maxillary molars was 14.5°±8.3°(mean); the angle between mediobuccal and palatal roots of the first maxillary molars was 30.8°±8.3°(mean). ②There was only 28% of the second maxillary molars formed angle, the angle between medical and distal buccal roots was 12.1°±2.8°(mean), the angle between mediobuccal and palatal roots of the second maxillary molars was 19.6°±2.8°(mean). ③ The angle between medical and distal roots of the first mandibular molars was 11.5°±3.5°(mean). ④ There was only 40% of the second mandibular molars formed angle, its mean was 10.5°±3.3°(mean). CONCLUSION: ① The more occlusal force, the separeted angle between roots is larger. ② The roots separated angle of maxillary molars is different with that of the same tooth of mandibular molars. ③ It is important in tooth extraction.