Sloped Dental Implants Applied To Different Types Of Jaw Bone:a Three-dimensional Finite Element Analysis

Objective: Made an biomechanical analysis through the establishment of 0 °, 5 °, 10 °,15 °, 20 °, 25 ° six angle of sloped dental implants implanted in type Ⅰ ~ Ⅳ bone model, and observed the situation of bone stress and strain around sloped implant, in order to know whether different types bone could fit sloped implant.Method: According to the basic data of ITI cylindrical dental implant, implant models were established in three-dimensional finite element analysis software ANSYS12.0,what’s more, the axis of the implant obliqued to the axis of abutment upon the implant 0 °, 5 °, 10 °, 15 °, 20 °, 25 ° respectively, forming 6 kinds of implant model. At the same time built porcelain cubes instead of crowns and jaw bone block models. The jaw bone models were constructed based on Lekholm and Zarb bone classification method: TypeⅠ: whole composed of compact bone; Type Ⅱ: compact bone was 3 mm thick; Type Ⅲ: compact bone was 1 mm thick; Type Ⅳ: compact bone was 1 mm thick,elastic modulus of cancellous bone decreased. The bone block, implants, crowns were assembled, keeping the axis of abutment parallel to the axis of bone block. After giving constraints on experimental conditions, vertical loading 300 N, and then stress and strain distribution situations in compact bone and cancellous bone around implants were analyzed.Results: This study successfully built six tilt dental implants implanted in the four types of bone models in three-dimensional finite element. When implants dental implanted in bone vertically, the maximum Von Mises stress in the compact bone distributed aroundimplants neck. While dental implanted sloped, maximum Von Mises stress in the compact bone distributed on the first thread of implant in the reverse direction of tilting.The maximum Von Mises of cancellous bone in Type Ⅱ bone distributed at the bottom of implant(the last thread), and the distribution of cancellous bone’s Von Mises stress in Type Ⅲ, Ⅳ bone was uniform, but the first thread in the reverse direction of tilting,had appeared in the stress concentration. The maximum Von Mises stress of compact bone was as one order of magnitude more as the maximum Von Mises stress of the cancellous bone. With increasing of implant tilting angle in the same type of bone, the maximum Von Mises stress and strain of both compact bone and cancellous bone rised gradully. However, when the same angle implant applied to different type of jaw,development trend of maximum Von Mises stress were:compact bone:Type Ⅳ>TypeⅢ > Type Ⅱ > Type Ⅰ; cancellous bone : Type Ⅲ > Type Ⅳ > Type Ⅱ;development trend of maximum strain were:compact bone:Type Ⅳ>Type Ⅲ>TypeⅡ>Type Ⅰ;cancellous bone:Type Ⅳ>Type Ⅲ>Type Ⅱ.Conclusion: ①When dental implants implanted in bone vertically, the maximum Von Mises stress in the compact bone distributed around implants neck. While dental implanted sloped, maximum Von Mises stress in the compact bone distributed on the first thread of implant in the reverse direction of tilting. The maximum Von Mises of cancellous bone in Type Ⅱbone distributed at the bottom of implant(the last thread),and the distribution of cancellous bone’s Von Mises stress in Type Ⅲ, Ⅳ bone was uniform, but the first thread in the reverse direction of tilting, had appeared in the stress concentration. The maximum Von Mises stress of compact bone was as one order of magnitude more as the maximum Von Mises stress of the cancellous bone.This suggested compact bone shoulder the bulk of bite stress when implant functioned.② When the same angle dental implant applied to different type of jaw, developmenttrend of maximum bone stress were: Type Ⅳ>Type Ⅲ>Type Ⅱ>Type Ⅰ. Von Mises stress of Type Ⅲ、Ⅳ bone grow rapidly. Therefore, in biomechanics, implanting in TypeⅠ、Ⅱbone were better than Type Ⅲ、Ⅳ bone.③ With increasing of dental implant tilting angle in the same type of bone, the maximum Von Mises stress and strain of both compact bone and cancellous bone rised gradully. That meaned implant tilting angle and the Von Mises stress of bone around implant were positively correlated.④ TypeⅠbone could be carried out sloped dental implanting under 25°;Type Ⅱ bone could be carried out under 20°.However, Type Ⅲ、Ⅳ bone didn’t apply to sloped dental implant.