Effect of joining the sectioned implant-supported prosthesis on the peri-implant strain generated in simulated mandibular model

Aim: The aim of this study is to evaluate the strain developed in simulated mandibular model before and after the joining of an implant-supported screw-retained prosthesis by different joining techniques, namely, arc welding, laser welding, and soldering. Materials and Methods: A specimen simulating a mandibular edentulous ridge was fabricated in heat-cured acrylic resin. 4-mm holes were drilled in the following tooth positions; 36, 33, 43, 46. Implant analogs were placed in the holes. University of California, Los Angeles, abutment was attached to the implant fixture. Eight strain gauges were attached to the acrylic resin model. Six similar models were made. Implant-supported screw-retained fixed prosthesis was fabricated in nickel-chromium alloy. A load of 400 N was applied on the prosthesis using universal testing machine. Resultant strain was measured in each strain gauge. All the prostheses were sectioned at the area between 36 and 33, 33 and 43, and 43 and 46 using 35 micrometer carborundum disc, and strain was measured in each strain gauge after applying a load of 400 N on the prosthesis. Specimens were joined by arc welding, soldering, and laser welding. After joining, a load of 400 N was applied on each prosthesis and the resultant strain was measured in each strain gauge. Results: Highest mean strain values were recorded before sectioning of the prostheses (889.9 microstrains). Lowest mean strain values were recorded after sectioning the prosthesis and before reuniting it (225.0 microstrains). Conclusions: Sectioning and reuniting the long-span implant prosthesis was found to be a significant factor in influencing the peri-implant strain

A Study on Self Centering of Face Bows

Hanau spring bow has been in use since 1986. Hanau spring bow is claimed to maintain self centering property when it is positioned in the patient as well as in the articulator. However there is no documented evidence to prove that feature. Mainly it was due to the absence of a testing device. Exclusively for the present study, the testing device consisting of a platform, stops and distance measuring system was designed by the third author. This study proved that Hanau has the capability of self centering