Analysis of Marginal Misfit and Strain Gauge in Implant-Supported Frameworks Using Straight Line and Offset Placement

(Pages: 62-69)

C.W. Abreu, R.S. Nishioka, I. Balducci, M.F. Mesquita and R.L.X. Consani

Jose Sampaio Luz, 340 – Ponta Verde, Maceió, Alagoas, Brazil




Abstract: Objective: The aim of this in vitro study was to quantify the strain development during axial loading on the straight line and offset placement using strain gauge analysis and to analyze microscopically the vertical and passive misfit.

Material and Method: Six Morse taper implants were inserted into two polyurethane blocks, with three arranged in a straight line (L) and three in an offset configuration (O). Microunit abutments were screwed onto the implants with a torque of 20Ncm. Metallic collar (M) and plastic copings (P) were screwed onto the abutments, which received standard wax patterns that were cast in Co-Cr alloy (n=5). Four strain gauges (SG) were bonded on the surface of each block. The superstructure’s occlusal screws were tightened onto the microunit abutments and then an axial load was applied. The magnitude of microstrain on each strain gauge was recorded in units of microstrain (µε). An optical microscope, with 0.5 µm of measurement accuracy and 120x magnification, was used to evaluate the levels of vertical and passive fit. The data were analyzed statistically by two-way ANOVA and Tukey’s test (p<0.05).

Results: There was not statistically significant difference in passive fit for the factor coping and configuration, but a significant difference existed in vertical fit for the factor of configuration (p=0.0257). A significant difference was also observed for strain for the factor of configuration (p=0.0005).

Conclusion: There was evidence of an advantage of offset implant placement in reducing the strain around the implant. The type of coping used did not interfere with the vertical and passive fit.

Keywords: Plastic coping, Implant, Marginal fit.