BEHR* M, ROSENTRITT M, LEDWINSKY E, LANG, R, HANDEL, G.
(Department of Prosthetic Dentistry, University of Regensburg, Germany)
Adhesive cementation is recommended for fiber-reinforced composite (FRC) fixed partial dentures (FPD). However, there are clinical situations where a conventional cementation is necessary or the only possible procedure. The aim of this in-vitro study was to investigate the fracture strength of conventional and adhesive cemented three-unit FRC-FPDs after simulation of five years oral stress. A polyethylen-fiber system (belleGlass, BG), a glass-fiber system with manual fiber adaptation (FibreKor, FK) and a glass-fiber system with a vacuum/pressure procedure (Vectris/Targis, VT) was used to construct the FRC-frameworks. The reconstructions (n=72) were assigned into subgroups of eight FPDs. Adhesive cementation was applied using Variolink II (Var) in the case of BG and VT and Lute-It (Lut) for FK. Conventional cementation was carried out using the resin-reinforced glass ionomere ProTecCEM (Pro) and FujiPlus. After cementation all FPDs were thermally-cycled and mechanically loaded (TCML: 6000x5°/55°C; 1.2x10 6;x50N, 1.66Hz), and then the fracture strength was determined with a Zwick universal testing machine. Mean, std. dev. were calculated. One-way- ANOVA was used to demonstrate differences between the groups.
When fixed with ProTecCEM, 7 of 8 FK and BG FPDs lost retention during TCML (=failure); in the case of VT 1 of 8 FPDs failed retention. No loss of retention was observed for FujiPlus and Variolink during TCML. If the FPDs were set using FujiPlus, VT and FK had significant lower fracture strength means compared with the adhesive fixed FPDs. BG did not demonstrate differences between FujiPlus and Variolink. Conclusion: loss of retention and considerable lower fracture strength demonstrate that the use of conventional cementation can lead to failure.