해면골 밀도 및 임플란트 나사산 형태에 따른 응력분석

Abstract

The purpose of this study was to compare the stress distribution on the type of implant thread according to the density of the alveolar bone on the finite element models of the two implant crowns with the same vertical alveolar bone level. The finite element model was designed with the parallel placement of the two fixtures (4.0 mm × 11.5 mm) with three types of implant thread (square type thread, triangular thread, and reverse buttress thread) on the mandibular 1st and 2nd molars. As the bone quality, the inner cancellous bone and the outer 2 mm cortical bone were designed, and the inner cancellous bone was classified into 2 models according to the density of the bone(2 different Young's modulus : high modulus, model 1; low modulus, model 2). The cortical and cancellous bone were assumed to be perfectly bonded to the implant fixture. Each group was loaded with 200 N magnitude in the vertical directions on the loading point position on the central position of the crown, the 2 mm and 3 mm buccal offset point from the central position. Von Mises stress value was recorded and compared in the fixture-bone interface in the bucco-lingual and mesio-distal sections. The results were as follows; 1. In comparison with the maximum Von-Mises stress in the cortical and cancellous bone according to the implant thread type, the square thread and reverse buttress thread in model 2 was more stressful in the cortical bone than model 1 regardless of the loading position. On the other hand, the triangular thread, square thread and reverse buttress thread in model 2 was more stressful in the cancellous bone than model 1 regardless of the loading position. 2. The triangular thread in both model 1 & 2 is more stressful in the implant fixture and surrounding bone than the square thread and the reverse buttress thread. 3. Regardless of the implant thread type, displacement of cortical and cancellous bone is increased more and more in the uniform pattern when the loading point is positioned more buccally from the center of occlusal surface in the first and second molar. Above the results, the stress in implant fixture and surrounding bone of the triangular thread was greater than the other thread(square thread and reverse buttress thread) according to the density of alveolar bone. Therefore, it was concluded that the triangular thread implant could not effect to the stress distribution and the implant failure would be possible during the continuous loading.