Chinese Journal of Tissue Engineering Research ›› 2026, Vol. 30 ›› Issue (36): 9505-9518.doi: 10.12307/2026.903

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Three-dimensional finite element analysis of the biomechanical effects on surrounding tissues following crown-by-crown treatment of impacted mandibular third molars

Li Shenghao1, Zhang Borui1, Ma Yufeng1, 2   

  1. 1School of Stomatology, Shanxi Medical University, Taiyuan 030000, Shanxi Province, China; 2Department of Stomatology, The Second Hospital of Shanxi Medical University, Taiyuan 030000, Shanxi Province, China
  • Received:2025-10-15 Revised:2026-03-07 Online:2026-12-28 Published:2026-05-22
  • Contact: Ma Yufeng, Chief physician, School of Stomatology, Shanxi Medical University, Taiyuan 030000, Shanxi Province, China; Department of Stomatology, The Second Hospital of Shanxi Medical University, Taiyuan 030000, Shanxi Province, China
  • About author:Li Shenghao, MS, Physician, School of Stomatology, Shanxi Medical University, Taiyuan 030000, Shanxi Province, China

Abstract: BACKGROUND: Extraction of impacted mandibular third molars is one of the common procedures in oral and maxillofacial surgery. Traditional crown-splitting and bone-removing techniques are prone to complications such as adjacent tooth injury, inferior alveolar nerve damage, and jaw fracture. Although minimally invasive extraction techniques have significantly reduced intraoperative trauma, the parameters for sectioning operations (e.g., cutting depth, width, and angle) still rely on empirical judgment and lack biomechanical quantitative standards.  
OBJECTIVE: To construct a three-dimensional finite element model of a horizontally and mesially impacted mandibular third molar and surrounding tissues, and to analyze the biomechanical effects of varying cutting depths, widths, and angles on crown fracture and surrounding tissues, thereby providing quantitative standards for precise crown sectioning.  
METHODS: Cone-beam CT data of the mandibular third molar region from a healthy volunteer with complete dentition were extracted. The mandibular third molar region model, including the mandibular third molar, mandibular second molar, mandibular bone (cortical and cancellous bone), and inferior alveolar nerve canal, was generated using three-dimensional reconstruction software Mimics 21.0, reverse engineering software Geomagic 21.0, and three-dimensional computer-aided design software SolidWorks 2022. Finite element software Ansys 2021 R1 was used to simulate clinical crown sectioning by applying a 35 N vertical load to investigate the effects of cutting parameters (depth: 11 mm, 10.5 mm, 10 mm, 9.5 mm, 9 mm; width: 1.5 mm, 1 mm; angle: 0°, 10°, 20°, 30°) on crown fracture, stress distribution characteristics in surrounding tissues, and displacement response patterns.  
RESULTS AND CONCLUSION: Three-dimensional finite element models of crown sectioning with different cutting parameters were successfully constructed. Through three-dimensional finite element analysis, the following conclusions were drawn: (1) When sectioning the crown using a 1.5 mm diameter bur, the optimal parameter combination is a cutting depth of 10-11 mm and a cutting angle of 0°-10°. This ensures complete crown fracture (maximum Von Mises stress value of the crown ≥ 250 MPa) while protecting adjacent teeth, the inferior alveolar nerve canal, and the mandibular bone, providing precise biomechanical guidance for crown sectioning in minimally invasive extractions. (2) In the extraction of horizontally and mesially impacted mandibular third molars, the choice of cutting depth and width should be based on ensuring complete crown fracture, fully eliminating resistance structures around the crown to provide ideal space for subsequent procedures and avoid damage to surrounding tissues. (3) In the extraction of horizontally and mesially impacted mandibular third molars, the cutting angle should be chosen as parallel as possible to the long axis of the second molar (0°-10°) to ensure crown fracture efficiency and protection of surrounding tissues.  

Key words: three-dimensional finite element analysis, mandibular third molar, cone-beam CT, minimally invasive extraction, crown sectioning

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