[Study on the thickness and morphology of lingual bone of impacted mandibular third molar based on CBCT and Simplant 3D reconstruction].

Purpose: The potential relationship between impacted mandibular third molar and lingual bone thickness was investigated by quantitative measurement of lingual bone thickness, and a three-dimensional visualization model of lingual bone was established.

Methods: Image data of 200 cases of mandibular impacted third molar were collected from the database of Hefei Stomatological Hospital. Thickness measurement and three-dimensional reconstruction of lingual bone at different measurement sites were performed by Simplant Pro software. Statistical analysis was performed using SPSS 22.0 software package, and the comparison of lingual thickness at different measurement sites was performed using rank sum test. Whether the thickness of bone plate was "high-risk type" was taken as the result variable, different related factors were analyzed by logistic regression.

Results: The lingual bone at the middle point of the root of the third molar was the thinnest. Multiple teeth, mesio-inclined and dial-inclined teeth, and Class Ⅱ and Ⅲ impacted teeth had thin lingual bone(P＜0.05). The mesial and distal inclines were observed, and the lingual bone was thin in the root apical region of the teeth in Class Ⅱ and Class Ⅲ(P＜0.05). In the lower impacted teeth, the thin lingual bone at the central crown site was more likely to be found in Class Ⅲ teeth(P＜0.05).

Conclusions: The thickness of lingual bone was related to the number of impacted tooth roots, tilt direction and impacted type. In the extraction of impacted teeth, the above factors should be considered, and the injury of lingual nerve, lingual bone and surrounding soft tissue should be vigilant.