SA3 - An Optimal Tooth Section Method for Mandibular Low-Level Impacted Third Molar: A Finite Element Study

Abstract:

Background: During complex tooth extraction, tooth section is an important factor affecting surgical efficiency and surrounding tissue trauma. This study applied finite element software to reconstruct a horizontally low-impacted mandibular third molar model and analyzed the effects of various factors on tooth section efficiency and surrounding tissue trauma using dental high-speed handpieces and elevators.Materials and methods: This study included the cone beam computed tomography data of a patient with a horizontally low-impacted mandibular third molar. Digital software was used to segment models of third mandibular molar (M3M), M2M and the nearby local mandibular bone. A 3D finite element model was established to further simulate the process of tooth section using dental high-speed handpieces and elevators. Many factors were included, such as the thickness of remaining tooth tissue (1-5 mm), the width of tooth section fissure (1-3 mm), the width of elevator (2-5 mm), the depth of elevator into the tooth section fissure (2-6 mm), the location of elevator (buccal, lingual, central) and the way to load force (rotating, levering). The impact of these factors on the stress distribution of M3M and surrounding tissues was analyzed, and their impact on tooth section efficiency and surrounding tissue trauma was further evaluated.

Results: The stress distribution on M3M was affected by many factors. When the thickness of remaining tooth tissue≤3 mm, the width of tooth section fissure≈2 mm, the width of elevator ≥4 mm, and the elevator located in the center of tooth section fissure, the stress distribution at the tooth section fissure is relatively uniform. Levering the elevator puts greater stress on M3M than rotating it. The depth of elevator into the tooth section fissure has no significant effect on stress distribution. In addition, the higher the tooth section efficiency, the greater the force loaded on the distobuccal side of M2M.

Conclusion: Adjusting the way of using dental high-speed handpieces and elevators can effectively improve tooth section efficiency. However, more attention should be paid to the trauma to adjacent tooth during this process.

Effect of the thickness of remaining tooth tissue on stress distribution on third mandibular molar and surrounding tissue.
Effect of the location of elevator on stress distribution on third mandibular molar and surrounding tissue.
Effect of the force-loading method of dental elevator on stress distribution on third mandibular molar and surrounding tissue.