Journal of Dental Medicine

Background and Aims: Freestanding fixed partial prosthesis is considered the first choice whenever possible. However, anatomical limitations for implants and other reasons may create situation in which it would be preferable to connect the implants to teeth. A biomechanical dilemma in a tooth/implant-supported system comes from dissimilar mobility. This disparity cause the bridge to function as a cantilever and a series of potential problems such as osseointegration loss, screw loosening arise. The aim of this study was to analyze the tooth-implant supported bridges in rigid/non-rigid connectors in cemented prostheses using finite element stress analysis.

Materials and Methods: In this study four three-dimensional models were simulated by use of Solid works software. These models are: 1-RCCP: rigid connector between tooth and implant, 2-NRC CP1: non-rigid connector at mesial side of implant, 3-NRC CP2: non-rigid connector at distal side of second premolar, 4-NRC CP3: non-rigid connector at the middle of pontic, The stress values of four models loaded with vertical forces (150 N) were analyzed.

Results: The maximum stress concentration was located at the crestal bone around implant and stress distribution was more balanced around the teeth except in the model of NRCCP2. Stress distribution was imbalanced in non-rigid connection especially in the NRCCP1 model. The presence of non-rigid connector in bridge increases the stress values in suprastructure and transfers to the adjacent structures. Conclusion: The tooth-implant supported prosthesis should be considered as a valuable prosthetic option. It could be suggested that if tooth and implant abutments are to be used together as fixed prostheses supports, rigid connector is the choice because the prosthesis and implant possess the inherent flexibility to accommodate dissimilar mobility characteristics.

  Background and Aims : According to the common application of non-metal prefabricated posts in dentistry and lack of enough information about the stress distribution in the root canal walls by these posts, this study was performed to compare the effect of two simple taper and double taper posts on the stress distribution on root canal walls by photo elastic method .

  Materials and Methods: The design of this study was experimental in photoelastic system. The posts, used in this investigation, were double taper and simple taper fiber posts with 0.9 mm diameter and 20 mm length and epoxy resin. First two photo elastic models with tooth dimensions were fabricated and the posts were placed inside the model. Then the core of the each post was fabricated on the model. Each models were loaded in polariscope and the formed fringe order colored ring were photographed.

  Results: In 100 N, 90 degree angle loading in cervical and apical fringe order showed 2.50 and 1.39 in simple taper posts and 1.39 and 2.35 in double taper post. In 150 N, 30 degree angle loading in cervical and apical fringe order showed 4 and 2.65 in simple taper posts, and 4 and 2.5 in double taper post.

  Conclusion: In the vertical and oblique loads, double taper fiber post showed better stress distribution than that of simple tapered posts.