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

The effect of time lapse on the accuracy of two acrylic resins used to assemble an implant framework for soldering
July 2004
By Therese McDonnell, Francis Houston, Declan Byrne, Catherine Gorman and Noel Claffey
The Journal of Prosthetic Dentistry
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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.