Misfit level of implant-supported frameworks: influence of veneering technique

Objective: This study evaluated the influence of veneering application and porcelain firing cycle on misfit level of implant-supported frameworks.

Methods: Forty CoCr alloy frameworks (Remanium 2000, Dentaurum, Germany) were fabricated from a metallic index containing 5 Branemark multi unit abutments. Analogs were positioned to the framework, to construct an index for each framework, which allowed the evaluation of marginal gaps caused only by the application of the veneering material. The frameworks were grouped: G1) heat acrylic resin (Clįssico, Clįssico, Brazil); G2) light polymerized resin (Versyo.com, Heraeus Kulzer, Brazil); G3) porcelain application (Carmen, Dentaurum, Germany); G4) simulation of porcelain firing cycle. Marginal refinement with spark erosion was conducted on specific equipment (Tel Med Technologies, USA), and marginal gap evaluated before and after this procedures, following the single screw test protocol. A traveling microscope (STN – Olympus, Japan - 120X) was used, tightening 10Ncm in the titanium screw. Data were subject to ANOVA and Tukey test (5%).

Results: All procedures increased significantly the misfit mean values of all groups: G1: 170.01 µm (±53.98); G2: 72.32 µm (±27.49); G3: 164.84 µm (±27.67); e G4: 86.28 µm (±20.01). After spark erosion, marginal gap mean values decreased significantly for the following groups: G1: 108. 54 µm (±40.75); G3: 109.61 µm (±24.42); and G4: 59.63 µm (±22.13). Light curing group decreased marginal gap mean values, but not significantly after spark erosion: G2: 49.70 µm (±16.65).

Conclusion: It can be concluded that heat cured acrylic resin and porcelain produced the highest mean values of marginal gaps, while light cured resin, the lowest. The application of porcelain produced higher misfit values than the simulation of porcelain firing cycles only. The spark erosion procedure was efficacious in reducing the frameworks marginal gaps to the levels clinically accepted for all groups evaluated. FAPESP(Grant no 2004/13629-5)/CNPQ (Grant no 141149/2005-1).