Effect of mandibular third molar teeth angulation on mandibular angle fracture ;A finite element analyses

The mandibular bone is the largest and strongest bone in comparison to the other bones in the face skeleton. However, it is the bone broken mostly in face injuries. The location of the fracture in mandibula depends on various factors. These can be listed as follows: the location of trauma vector, the movements of masticatory muscles, the condyle position at the moment of fracture, occlusion, the quality of bone, and the direction of traumatic force. The relationship of the impacted lower third molar teeth to mandibular angle fractures has been subjected for many epidemiological studies. It is argued that the risk of fracture in mandibular angle is two to four times more when there are particularly an impacted or partially impacted third molar teeth. However, the effect of the position of the impacted tooth inside a bone on angle fraction is not clear yet. This study seeks to reveal the effect of third molar teeth that are impacted in various positions on the angle fragilty. Third molar teeth are impacted in mandibula bone in the following positions: mesioangular, vertical, horizontal, and distoangular positions. There are additional classification positions made from the change in the distance of adjacent tooth and anterior border of ramus. In this study, impacted teeth in various positions mentioned above were modelled on computer separately. The stress values created by impacted third molar teeth inside the bone depending on their positions on the angle were determined in the face of trauma on different points of mandibula. This is a three-dimensional finite element analysis study conducted with static linear analysis. The study showed that the force that created the highest stress in the angle among the modelled groups is the force by ipsilateral angle. With a force by symphysis, there is more stress accumulation near buccal compared to lingual area for all the types of impacted teeth. The comparison of control model with other models showed that there is not a difference in stress values measured in angle lingual area. With ipsilateral force, there are more stress in lingual area for class II and class III models whereas stress accumulation is more near buccal area for class I model. Key Words: impacted third molar teeth, trauma, finite element analysis, mandibular angle