Implant Prosthodontics: An in-vitro photoelastic stress analysis

Abstract

Arguably the greatest controversy in implant dentistry is that of linking a natural tooth and an implant together in a fixed restoration. Some researchers have absolutely contradicted the inclusion of the two, while others have suggested different options such as design considerations in the restoration or in the implant itself. Further more an outcome of a situation in linking a periodontally compromised abutment with an implant in a restoration itself lacks investigation. The study was designed to evaluate stresses transmitted to supporting structures by a fixed partial restoration under different abutment situations using a rigid / movable connector in the prosthesis. Also to evaluate stresses transmitted and the outcome of linking a periodontally compromised abutment with the implant in a fixed restoration. Photoelastic models were fabricated depicting a partially edentulous posterior mandible. The situations depicted were of a completely tooth supported, tooth implant supported and a completely implant supported situations. 20% and 35 % periodontal damages were also incorporated in the anterior abutment in the models. The fixed restorations were fabricated with movable and rigid type connectors. Vertical point loads were applied on fixed points on the restoration and the transmitted stresses under different simulated situations of the study were then recorded and analyzed. The fringe orders were recorded photographically and the fringe orders were tabulated for interpretation. After thorough analysis of the results obtained the study concluded that it is indeed beneficial to connect natural tooth to implants in a fixed partial restoration and that the type of connector advocated is a rigid one. Also conclusive is the fact that periodontally compromised teeth can be integrated in the restoration in combination with an implant as a conservative treatment option. The use of non rigid connectors in any situation may be erroneous.