Adhesive FPD fracture strength: glass-fiber reinforcement and resin viscosity effects

Objectives: To evaluate the influence of glass fiber reinforcement and resin viscosity on fracture strength of adhesives composite resin fixed partial denture (FPD). Methods: A stain steel mold was fabricated simulating occlusal preparations for adhesive FPD in upper first pre-molar (4x4x2mm) and molar teeth (6x4x2mm), with a proximal box (2x1x4mm) and a 7mm of distance between them. These molds were duplicated in polyurethane (n=60) and divided in two groups according to resin viscosity: G - Grandio SO (VOCO) (n=30) and GHF - Grandio SO Heavy flow (VOCO) (n=30). These groups were subdivided in three subgroups according to the glass-fiber reinforcement used (n=10): Subgroup N – no glass-fiber reinforcement was used; Subgroup V – GrandTEC (VOCO); Subgroup S – everStickC&B (Stick Tech). Four increments divided in two layers, two in the bottom and two in the top of preparations were cured according to manufacturers' instructions. A vertical force was loaded in the center of the specimens at a crosshead speed of 1mm/min. Data were obtained in Kgf and submitted to 2-way ANOVA and Tukey test (a;=0.05). Results: ANOVA showed significant differences for glass-fiber reinforcement. Subgroup N (24.45±3.60)^a was significantly different from Subgroup S (32.54±6.94^b) and Subgroup V (37.18±5.33)^c. Conclusion: The glass fibers tested were able to improve fracture strength of the simulated adhesive PFD, GrandTEC showed the highest values of fracture strength and for these resins, the viscosity had no influence on the fracture strength of adhesive PFD.