In spite of biomechanical advantages, use of two standard implants to support a single molar restoration is often limited. The mesial distal dimension for most single molars is less than 12mm. However, a one-piece abutment-implant system can offer small 2.8mm diameter implants. A combination of one-piece devices in standard 3.8mm and the smaller 2.8mm diameters can be used to replace a single molar. The different sized implants can be placed to mimic the natural multi-rooted configuration of molars.
A simplified prosthetic solution has been developed to overcome the root-analog (implant) convergence problem. Two prefabricated castable copings designed to fit the hexagonal shape of the abutment and its shouldered margin were splinted together.The path of insertion was established by removing only the inner walls of the converging abutments. Pull-out tests were performed using an Instron material testing machine to evaluate the retentive strength of the splinted prefabricated copings cemented onto the modified hex abutment and also the custom round abutment copings. The splinted coping casted from prefabricated components produces the highest retentive strength (98.86 Kgf, SD 13.85 Kgf). The retentive strength obtained from the custom casted round coping was only 43.61 Kgf, SD 8.04 Kgf.
Clinically, selective removal of three adjacent surfaces on one side of the hexagonal abutment in this one-piece device permits the simple restoration of molars and multiple tooth implants.

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This research is supported by Biomedical Implant Technology Inc.