Effect of IMC in Screw-Retained IMZ Implant Superstructure. Superstructure with Misfit.

A screw-retained prosthesis is frequently used as an implant prosthesis. However, the superstructure is screwed to its abutments, stress is produced in bone around the implant or in the superstructure, and if incompatibility exists between them, the stress becomes larger. The objective of this study was to evaluate the stress buffer function of the IMC (intramobile connector) on a screw retained superstructure with vertical incompatibility. Two specimens were prepared for this experiment: In the 1 st specimen, three IMZ implants were embedded perpendicularly to the upper surface of the PMMA block in a straight line. In the 2 nd specimen, three implants were embedded in the same way as the 1 st but one terminal implant inclined 10 degrees mesially to the longitudinal axes of other implants. Strain produced on the block surface around each implant was measured with a strain gauge, because a torque wrench was screwed to the superstructure with vertical incompatibility (50μm, 100μm) to abutments. The dimensional compensation function of IMC was marked with 50μm incompatibility, but its function was decreased, and moreover IMC was permanently distorted with 100μm incompatibility. The effect of IMC in specimen 1 was similar to specimen 2. The incompatibility condition produced strain with IMC was less than that without IMC. Strain tended to be larger in the central implant.