Influence of implantoplasty on stress distribution of exposed implants at different bone insertion levels

Abstract This study evaluated the effect of implantoplasty on different bone insertion levels of exposed implants. A model of the Bone Level Tapered implant (Straumann Institute, Waldenburg, Switzerland) was created through the Rhinoceros software (version 5.0 SR8, McNeel North America, Seattle, WA, USA). The abutment was fixed to the implant through a retention screw and a monolithic crown was modeled over a cementation line. Six models were created with increasing portions of the implant threads exposed: C1 (1 mm), C2 (2 mm), C3 (3 mm), C4 (4 mm), C5 (5 mm) and C6 (6 mm). The models were made in duplicates and one of each pair was used to simulate implantoplasty, by removing the threads (I1, I2, I3, I4, I5 and I6). The final geometry was exported in STEP format to ANSYS (ANSYS 15.0, ANSYS Inc., Houston, USA) and all materials were considered homogeneous, isotropic and linearly elastic. To assess distribution of stress forces, an axial load (300 N) was applied on the cusp. For the periodontal insert, the strains increased in the peri-implant region according to the size of the exposed portion and independent of the threads’ presence. The difference between groups with and without implantoplasty was less than 10%. Critical values were found when the inserted portion was smaller than the exposed portion. In the exposed implants, the stress generated on the implant and retention screw was higher in the models that received implantoplasty. For the bone tissue, exposure of the implant’s thread was a damaging factor, independent of implantoplasty. Implantoplasty treatment can be safely used to control peri-implantitis if at least half of the implant is still inserted in bone.

摘要：本研究评估了种植体成形术（implantoplasty）对不同骨内植入深度的暴露种植体的影响。采用犀牛（Rhinoceros）建模软件（版本5.0 SR8，美国西雅图McNeel北美公司）构建了来自瑞士瓦登堡斯特曼研究所（Straumann Institute, Waldenburg, Switzerland）的骨水平锥形种植体（Bone Level Tapered implant）模型。通过固位螺丝将基台固定于种植体，并在粘接线处构建一体式全冠模型。构建了6组种植体螺纹暴露量依次递增的模型：C1（1mm）、C2（2mm）、C3（3mm）、C4（4mm）、C5（5mm）及C6（6mm）。所有模型均制作双份，每组双份模型中的一份通过去除螺纹模拟种植体成形术处理，分别记为I1、I2、I3、I4、I5及I6。将最终模型几何以STEP格式导出至ANSYS软件（ANSYS 15.0，美国休斯顿ANSYS公司），并假设所有材料均为均质、各向同性且线弹性材料。为评估应力分布，在牙尖施加轴向载荷（300N）。结果显示，对于牙周相关结构，种植体周围区域的应变随暴露部分的尺寸增大而升高，且与螺纹是否存在无关；种植体成形术处理组与未处理组之间的差异小于10%。当种植体骨内植入部分小于其暴露部分时，出现应力临界值。在暴露种植体模型中，经种植体成形术处理的模型，其种植体与固位螺丝上产生的应力更高。对于骨组织而言，种植体螺纹暴露是损伤性因素，且与是否进行种植体成形术无关。若种植体至少有一半仍植入骨内，则种植体成形术可安全用于控制种植体周围炎（peri-implantitis）。