Effect of Orthodontic Bracket Type and Mouthguard Presence on the Stress and Strain during a Frontal Impact

Abstract The aim of this study was to analyze the influence of orthodontic bracket type (metallic or ceramic) and mouthguard on biomechanical response during impact. Two-dimensional plane-strain models of a patient with increased positive overjet of the maxillary central incisor was created based on a CT scan, simulating the periodontal ligament, bone support, gingival tissue, orthodontic brackets (metallic or ceramic) and mouthguard. A nonlinear dynamic impact finite element analysis was performed in which a steel object hit the model at 1 m/s. Stress distributions (Von Mises and Modified Von Mises) and strain were evaluated. Stress distributions were affected by the bracket presence and type. Models with metallic and ceramic bracket had higher stresses over a larger buccal enamel impact area. Models with ceramic brackets generated higher stresses than the metallic brackets. Mouthguards reduced the stress and strain values regardless of bracket type. Mouthguard shock absorption were 88.37% and 89.27% for the metallic and ceramic bracket, respectively. Orthodontic bracket presence and type influenced the stress and strain generated during an impact. Ceramic brackets generated higher stresses than metallic brackets. Mouthguards substantially reduced impact stress and strain peaks, regardless of bracket type.

摘要 本研究旨在分析正畸托槽（orthodontic bracket）类型（金属托槽或陶瓷托槽）与护齿器（mouthguard）对撞击过程中生物力学响应的影响。研究基于CT扫描数据，构建了上颌中切牙（maxillary central incisor）前牙覆盖（positive overjet）增大患者的二维平面应变模型，模拟对象包括牙周膜（periodontal ligament）、骨支持组织、牙龈组织、正畸托槽及护齿器。随后开展非线性动态撞击有限元分析，以1 m/s的钢质物体撞击该模型，并评估了冯·米塞斯（Von Mises）应力、修正冯·米塞斯应力的分布情况与应变数据。结果表明：托槽的存在与类型会对应力分布产生影响；佩戴金属或陶瓷托槽的模型，其颊侧牙釉质撞击区域的应力水平更高且影响范围更广；陶瓷托槽模型产生的应力高于金属托槽模型。无论托槽类型如何，护齿器均可降低应力与应变数值；金属托槽组与陶瓷托槽组的护齿器减震率分别为88.37%与89.27%。综上，正畸托槽的存在与类型会对撞击过程中产生的应力与应变产生影响，陶瓷托槽相较于金属托槽会产生更高的应力水平；无论托槽类型如何，护齿器均可显著降低撞击应力与应变峰值。