Tolerance Measurements on Internal- and External-Hexagon Implants

Purpose: To measure the horizontal machining tolerances of the interface between internal-and external-hexagon implants and analogs with corresponding components after delivery from the manufacturer. These values may be a valuable tool for evaluating increasing misfit caused by fabrication, processing, and wear. Materials and Methods: Seven implants and seven analogs with external-and internal-hexagon connections (Biomet 3i) with corresponding prefabricated gold cylinders and gold screws, prefabricated cylindric plastic cylinders, and laboratory screws were studied. One set of components from the external and internal groups was measured manually and digitally. Measurements from the test subjects were compared with identical measurements from the virtual model to obtain threshold values. The virtual model was then used to obtain optimally oriented cuts. Results: The horizontal machining tolerances for castable plastic abutments on external implants were 12 +/- 89 mu m, and for internal implants they were 86 +/- 47 mu m. Tolerance measurements on prefabricated gold abutments for external implants were 44 +/- 9 mu m, and for internal implants they were 58 +/- 28 mu m. Conclusion: The groups with metallic components showed the smallest tolerance at < 50 mu m for the external group and < 90 mu m for the internal group. The prefabricated plastic cylinder groups ranged from < 100 mu m for external and < 130 mu m for internal connection.