The purpose of this study was to analyze the stress distribution at supporting bone according to the types of connection modality between implant and tooth in the superstructure. This investigation evaluated the stress patterns in a photoelastic model produced by three different types of dental implants such as Branemark, Steri-Oss, IMZ and resin tooth using the techniques of quasi three dimensional photoelasticity. The teeth-supported bridge had a first molar pontic supported by second premolar and second as a control group. The implant and tooth-supported bridge had a first molar pontic supported by second premolar and implant posterior retainer as an experimental group. Prostheses were mechanically connected to an adjacent second premolar by the rigid or nonrigid connection. Nonrigid connection used an attachment placed between the tooth-supported and fixture-supported component. The female(keyway) of attachment was placed on the distal end of the retiainer supported by the tooth; the male(Key) of attachment connected to the osseointegrated bridge was engaged into the keyway. All prostheses were casted in the same nonprecious alloy and cemented and screwed on
their respective abutments and implants. 16kg of vertical loads on central fossae of second premolar, first molar pontic, implant of second molar were applied respectively and 6.5kg of inclined load on middle buccal surface of first molar pontic was applied. @ES The results were as follows: @EN 1. Under the vertical load on the central fossa of first molar pontic, the stress developed at the apex of tooth or implat was more uniformly distributed in the case of nonrigid connection than in the case of rigid connection. 2. Under the vertical load on the central fossa of first molar pontic, the stress developed around the cervical area of tooth or implant was larger in the case of rigid connection than in the case of nonrigid connection because the bending moment was more occured in the case of rigid connection than in the case of nonrigid connection. 3. Stress was more restricted to the loaded side of nonrigid connection than to that of rigid connection. 4. Under the inclined, load, the screw loosening of implant was more easily occured in the case of nonrigid connection than in the case of rigid connection due to torque moment. 5. In the case of Branemark implant, the stress concentration in second premolar was larger and the stress developed around the cervical area of implant was lower than any other cases under the vertical load, because Branemark implant with the flexible gold screw was showed in inlcine toward second premolar by a bending moment. 6. The stress developed around the apex of tooth or implant was more uniformly distributed in the case of Steri-Oss implant with stiff screw than in the case of Branemark implant under the vertical load. But, the stress developed around the cervical area of the Steri-Oss implant was larger than that of any other implants because bending moment was occured by vertical migration of second premolar. 7. The stress distribution in the ase of IMZ implant was similar to the case of natural teeth under small vertical load. But, the residual stress around the implant was showed to occur due to deformation of IMC and sinking of screw under larger vertical load.
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