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Several in vitro studies employ the confection of cavity preparations that are difficult to standardize by means of manual high speed handpieces. This study presents the development of a cavity preparation machine designed to standardize in vitro cavity preparations. A metal base of 25 mm x 25 mm x 4 mm (length x width x height) was coupled to a small mobile table which was designed to be able to move by means of two precision micrometers (0.01-mm accuracy) in the horizontal directions (right-left, and back-front). A high speed handpiece was coupled to a metallic connecting rod which had an accurate dial indicator enabling control of the vertical movement. The high speed handpiece is also able to move 180 degrees around its longitudinal axis and 360 degrees around its transversal axis. The suggested cavity preparation machine precisely helps in the standardization of cavity preparations for in vitro studies.

Four commercial brands of chemically activated acrylic resin were compared through photoelastic analysis. Photoelastic resin blocks were made with 2 implants placed parallel to each other and 2 square transfer copings splinted. Both transfers were splinted with chemically activated acrylic resin: Dencrilay, Duralay I, Duralay II, and GC. Data were analyzed by 2-way analysis of variance and Tukey test (P < .05). Statistically significant differences were found among the 3 brands of chemically activated acrylic resin. Dencrilay showed greater dimensional alteration. Duralay I and GC are recommended for the transfer of the position of the multi-implants.

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The purpose of this article was to compare through photoelastic analysis the stress distribution in 3 direct transfer techniques for implants with splinting. Three photoelastic resin blocks were made with 2 implants placed parallel to each other and 2 square transfer copings splinted. Both transfers were splinted with acrylic resin chemically activated in 3 different techniques: metallic sticks (T1), prefabricated acrylic bars (T2), or dental floss (T3). A circular polariscope was used, and the distortion energy (E) was calculated in 4 periods: 20 minutes and 3, 24, and 36 hours. Statistically significant differences were found among the 3 techniques (P < .05). The dental floss presented the greatest distortion energy values (T3 = 0.469 Kgf/mm(2)) and the metallic sticks the lowest values (T1 = 0.0 Kgf/mm(2)). Thus, the metallic sticks technique (T1) appears to be the most accurate protocol to be used for implant-supported prosthesis with multiple abutments.