The relationship between the variables of mandible and the impaction of mandibular third molar

Objective:Analysing the relationship between the between the variables of mandible and the impaction of mandibular third molar to understand the mechanism of the impaction of mandibular third molar.Method:83 orthopanto mographics were used in this paper.The inclination angle of mandibular third molar,the gonial angle,the crystal-marginal angle,the length of retromolar space,the length of the mandibular alveolar ridge,and the mesiodistal crown width of mandibular third molar were measured in 146 sides without missing teeth or suplimental teeth and crowded dentition.The results were analysed.Result:The length of retromolar space,the length of the mandibular alveolar ridge and the mesiodistal crown width of mandibular third molar were related to the impaction of mandibular third molar,but the gonial angle,the crystal-marginal angle were not.Conclusion:The impaction of mandibular third molar were related to the development of the mandible.The length of retromolar space,the length of the mandibular alveolar ridge and the ratio of the length of retromolar space and the mesiodistal crown width were the main affecting factors.