The effect of time lapse on the accuracy of two acrylic resins used to assemble an implant framework for soldering

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Abstract

Statement of problem

There are insufficient data on the accuracy of resin indexing materials for the assembly of implant prostheses in vivo.

Material and methods

This in vitro study assessed the fit of an implant framework with the use of 2 common acrylic resins.

Purpose

A standardized type IV gold alloy cast framework with 3 stainless steel implant replicas secured to 3 premachined gold cylinders placed 200 mm apart using a parallelometer was fabricated on a flat type IV stone model. Wax was placed around the center of each bar section, and a silicone matrix was fabricated to enable the same quantity of material to be used for each assembly. Each bar was sectioned at the center of the matrix, and indices (n=20) were fabricated from Duralay and GC Pattern acrylic resins. The materials were allowed to polymerize for 15 minutes before the assemblies were removed from the model. Frameworks were visually assessed for fit after an additional 15 minutes, after 2 hours, and after 24 hours, using the Sheffield 1-screw test. Observational outcomes are presented indicating visually perceived fit relative to the type of indexing resin.

Results

Both indexing materials were judged to be visually accurate at the 15-minute time interval only.

Conclusion

Within the limitations of this in vitro study, both resin-indexed implant assemblies were judged visually accurate for fit 15 minutes after polymerization but not at subsequent test intervals.

Section snippets

Material and methods

Three stainless steel implant replicas (Nobel Biocare USA, Yorba Linda, Calif) were secured 20 mm apart in a flat, type IV stone (Suprastone; KerrLab, Orange, Calif) model with the use of a parallelometer. A type IV gold alloy cast framework (PBVI; Phoenix, Shannon, Ireland) was fabricated with the use of premachined gold cylinders (DCA073; Nobel Biocare, Gothenberg, Sweden). The framework was sectioned carefully with a 0.25-mm-blade saw (Antiope, Germany) at 2 points; each cylinder was thereby

Results

All specimens, regardless of resin type, exhibited passive fit at the 15-minute interval (Table I). At the 2-hour interval, none of the assemblies fabricated with Duralay but 2 of the 20 assemblies fabricated with GC Pattern resin were deemed adequate. None of the assemblies of either resin exhibited visual passive fit at the 24-hour time point.

Discussion

This study was designed to compare the relative visual accuracy of 2 materials commonly used to make soldering indexes for implants. No attempt was made to determine absolute accuracy. Visual accuracy of fit was obtained for both types of resin assemblies after a 15-minute time lapse, but after 24 hours, none of the indexed assemblies exhibited visual passive fit. The probable cause for this finding is continued polymerization and shrinkage of the materials.

Conclusions

The results of this investigation suggest that implant assemblies joined with acrylic resin materials should be invested as soon as possible after polymerization.

References (9)

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