| The anterior maxillary jaw is frequently called the "esthetic zone" because of its high visibility and influence on facial appearance. Implant placement and single-tooth restoration in this region can present some esthetic challenges for the clinician. The underlying titanium abutment, for example, can diminish porcelain translucency and result in a darkened prosthesis. Subsequent changes in soft-tissue margins can also result in the visibility of titanium at the gingival crevice. Therefore, the application of zirconia abutment in implant prosthetics of maxillary anterior part is increasing gradually, but the biomechanics study concerning it is less .This experiment will establish three-dimensional finite element models by Altair Hypermesh software, then analyzing the stress distribution of five different zirconia abutments,bolts and the bone around the implant under different surrounding by Altair Hyperview software to investigate the effect of the different zirconia abutment types on the stress distribution in bone,abutment and bolt using three-dimensional finite element analysis and provide instruction for clinical application.The maximum Von Mises stress in bone with Replace abutment was higher than that generated with the lifecore hollow abutment and the lifecore solid abutment, while the maximum Von Mises stress in abutment with Replace abutment was always lower than that generated with the lifecore hollow abutment and the lifecore solid abutment ; The maximum Von Mises stress in bone with lifecore solid abutment was lower than that generated with the lifecore hollow abutment, while the maximum Von Mises stress in abutment higher than that generated with the lifecore hollow abutment; The maximum Von Mises stress that exist in bone and abutment increased as the angulation increased; There are no remarkable difference between zirconia abutment and titanium abutment.This experiment result manifest that the stress distribution tendency of different zirconia abutments,bolts and the bone around the implant under different surrounding is similar,the Von Mises stress of implant-bone is concentrate in cervical cortical bone,that can be explained by stress dodge principle: the element has bigger elastic modulus will bear more load in the system constituted by two or more different elements. Cortical bone bears more stress when the stress transmit from implant to bone because the elastic modulus of cortical bone is bigger than the elastic modulus of cancellous bone. The Von Mises stress of abutment is concentrate in the junction of abutment and implant which is similar to the study of Gehrke. This experiment also find that the compressive stress distribution of Replace abutment model and Lifecore solid abutment model,Lifecore hollow abutment model is different which may be relate to the morphology of implant bottom. The different of maximum Von Mises stress exists in the different zirconia abutment model is related to the different conjunction of abutment and implant. In addition, the stress distribution also may be influenced by the contact area and morphology of implant and abutment. There are no remarkable difference between zirconia abutment and titanium abutments which states the influence of abutment material to the stress distribution is little. We can find from the result of the experiment that the maximum Von Mises stress in bone with Replace abutment was higher than that generated with the lifecore hollow abutment and the lifecore solid abutment, while the maximum Von Mises stress in abutment with Replace abutment was always lower than that generated with the lifecore hollow abutment and the lifecore solid abutment, so we should select the Replace system when the bone is not ideal while the bone is ideal but exist the occlusion tightness and odontoprisis we should select the Lifecore system at best to reduce the incidence rate of mechanical complicationThis experiment result manifest that the stress distribution tendency of different angular abutments in the bone around the implant under different surrounding is similar,the Von Mises stress of implant-bone is concentrate in cervical cortical bone. The study of Saab to angular abutment and straight abutment also confirmed it .In addition, Brosh did the similar experiment of normal titanium abutments, studying the stress distribution of 0°abutment,15°abutment and 25°abutment by photoelasticity analytical method, and found that the maximum Von Mises stress exist in bone of angular abutment increased is higher than that exist in bone of straight abutment and the maximum Von Mises stress increased as the angulation increased ,that is similar to the conclusion of this experiment. This experiment also find that the Von Mises stress of abutment is concentrate in the junction of abutment and implant. The Von Mises stress that exist in bone and abutment concentrate level increased as the angulation increased, especially the 25°abutment.As a word,there has the influence of the abutment types on the stress distribution in bone and abutment , so we should select the appropriate abutment for different patients; The abutment angulation had a significant influence on the stress distribution in the abutment,bolt and bone , rised as the angulation increased , that suggest that we should take more attention to the implant orientation and use straight abutment or little angular abutment;The zirconia abutment can be used safely as there are no noticeable difference between zirconia abutment and titanium abutment on stress distribution. However,this experiment has a few deficient which should be improved:(1)Material character and experiment surrounding of the experiment all be supposed for ideal appearance, the higher accuracy research method should be exhibited in further, for example not line three-dimensional finite element stress analysis etc;(2) experiment term Limited by the experiment surrounding, this experiment did not can apply the dynamic load but static load, in fact the dynamic load is more correspond to the physiology appearance of oral cavity. |
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