Orthopantomographic comparative research of mandibular molar morphologic of crown and root of tooth.

Objective:Statistical analysis of mandibular molar mesiodistal crown width and tooth length and development of root. Method:To measure orthopantomographic of mandibular none loose and the root of mandibular third molar finish developed 249 subjects. Result:First molar tooth length was longer than second ,and second molar was longer than third; first molar mesiodistal crown width was biggest, second and third molar did not differ; first malor ratio of root division was biggest, second and third molar did not differ; first malor degree of root division was biggest, second and third molar did not differ; third molar erupted groups tooth length and ratio of root division was bigger than impacted groups, and there was positive relationship between third molar erupted groups tooth length and mesiodistal crown width, third molar width single root groups were differences with double root groups; third molar tooth crown width/eruption space ratio was inversely associated with third molar tooth length ratio. Conclusion:Mandibular first molar crown and root form were best. Third molar crown and root form was the same with second molar, as long as enough room third molar root can well development.