Objective: To investigate effect of the contact surface between the bridge and the adjacent teeth on the stress distribution of the implant and bone tissue and the displacement of the prosthesis in the cantilever fixed implant bridge restoring missing mandibular central incisors. Methods: Two-dimensional images of the mandible and dentition in healthy adults were obtained using CT data. A three-dimensional finite element model of cantilever fixed bridge supported by implants with mandibular central incisor was established by computer reconstruction technique.The contact surface between the bridge and the adjacent natural tooth was designed as "oval" and "trapezoid". The "trapezoid" has a slightly smaller median diameter on the labial side and a slightly larger medial diameter on the lingual side. Loading of 120 N was applied on the tangential margin of the middle line of the long axis of the bridge 41. The direction was set at 0°, which was parallel to the long axis of the tooth and downward. The buccal to lingual and downward angles were 30°, 45° and 60°, respectively, perpendicular to the long axis of the tooth and 90° to the lingual side.The stress distribution of the implant and surrounding bone tissue and the displacement of the prosthesis were compared between the two models. Results: Under axial and buccolingual loading, the maximum equivalent stress peak in the implant and surrounding bone tissue in the cantilever with trapezoidal contact surface design and the maximum displacement of the prosthesis were lower. Moreover, the distribution of stress was more balanced and the concentration range of stress was smaller. With the loading angle increasing, this trend was more obvious. When loading angle increased to 90°, the maximum equivalent stress and the maximum displacement of the elliptic contact surface model implant and surrounding bone tissue were 196 and 101 MPa and 0.196 mm, respectively, while the trapezoidal contact surface model were 157 and 72 MPa and 0.164 mm, respectively. Conclusions: The trapezoidal contact surface of the bridge and the adjacent teeth in the cantilever fixed bridge supported by implants with mandibular central incisor is beneficial to reduce the impact of the leverage on the implant and surrounding bone tissue.
目的： 比较下颌中切牙种植单端固定桥桥体与邻牙接触面形状对种植体、骨组织应力分布及修复体位移的影响。 方法： 采用CT扫描获取健康成人下颌骨及牙列影像数据，建立下颌中切牙种植体单端固定桥修复的三维有限元模型，其中与桥体接触的邻近天然牙的接触面分别设计为椭圆形和梯形（唇侧底边略小而舌侧底边略大）。在桥体41长轴中线切缘处加载120 N载荷，方向分别设定为平行于牙体长轴且向下的0°角，颊侧至舌侧并向下与牙体长轴分别呈30°、45°、60°角，垂直于牙体长轴且向舌侧的90°角。比较两种模型种植体、周围骨组织的应力分布情况以及修复体的位移变化。 结果： 在相同条件加载下，与椭圆形接触面模型相比，梯形接触面模型种植体及周围骨组织的最大等效应力和修复体的最大位移均较小，且应力分布更均匀，应力集中范围更小，随着加载角度的增加，此种趋势更明显，即当加载角度增大至90°时，椭圆形接触面模型种植体及周围骨组织的最大等效应力、修复体的最大位移分别为196和101 MPa、0.196 mm，而梯形接触面模型分别为157和72 MPa、0.164 mm。 结论： 下颌中切牙种植单端固定桥桥体与邻牙的梯形接触面有利于减小杠杆作用对种植体及周围骨组织产生的影响。.
Keywords: Dental implants; Dental stress analysis; Denture, partial, fixed; Finite element analysis.