Comparison of strains transferred to a bone simulant between as-cast and postsoldered implant frameworks for a five-implant-supported fixed prosthesis.

PURPOSE

To measure and compare the strains transferred by screw-fastening one-piece full-arch prostheses as cast and after sectioning and soldering.

MATERIALS AND METHODS

Photoelastic resin was applied directly to five 3.75 x 13-mm Brånemark implants, situated 7 mm apart, in a silicone mold of an edentulous mandible. Four strain gauge rosettes were also incorporated in the resin to allow strain measurements at four locations. Three frameworks were made from a single master cast produced from an impression of the five-implant model with 4-mm abutments. These frameworks were sequentially secured to the master model with five gold slot screws tightened to 10 N cm. Strain indicator readings were recorded at a standardized time following the initial fastening of each prosthesis. The test was repeated three times. Each of the three castings were subsequently sectioned and soldered in two locations, mesial to the two terminal fixtures. After soldering, the three superstructures were returned to the master model for measurement of postsolder strains three times each. A one-way repeated-measures ANOVA was performed to determine differences between mean principal strains between the as-cast and postsoldered groups.

RESULTS

A statistically significant difference was found in the principal strains between the as-cast and soldered frameworks. Overall, there was a decrease in the magnitude of strain for the soldered frameworks.

CONCLUSIONS

Sectioning and soldering improved the as-cast accuracy as far as the amount of strain transferred to the bone simulant.