In vitro resistance of reinforced interim fixed partial dentures

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Statement of Problem. Comprehensive restorative dental treatment often necessitates the use of interim fixed partial dentures (FPDs) with high stiffness, especially in long-span restorations or areas of heavy occlusal stress. Purpose. This in vitro study evaluated the fracture load of interim FPDs made with various materials and span lengths. Material and Methods. Groups (n = 3) of interim FPDs were fabricated with prosthodontic resin materials on 2 abutments with 3 different pontic widths of 3 units (12 mm), 4 units (19 mm), and 5 units (30 mm). The following materials were tested: (1) a thermoplastic polymer (Promysan Star), (2) Promysan Star with a veneering composite (Vita Zeta), (3) a nonimpregnated polyethylene fiber reinforced resin (Ribbond) with a veneering composite (Sinfony), (4) an impregnated fiber reinforced composite system (Targis/Vectris), and (5) a conventional polymethyl methacrylate, Biodent K+B, (control group). After 5000 thermocycles in 2 water baths at 5° and 55° C, the FPDs were temporarily fixed with a provisional cement on the corresponding abutments and subjected to 3-point bending until fracture by a universal testing machine. Statistical analysis consisted of an analysis of variance (ANOVA, 1-way, 2-way) and Bonferroni-Dunn's multiple comparisons post hoc analysis for test groups (α =.05). Results. Fracture resistance (N) differed significantly for 3 (mean: 640 ± 146 N), 4 (626 ± 229 N), and 5 unit (658 ± 98 N) Targis/Vectris FPDs compared with the corresponding Promysan (284 ± 21 N to 125 ± 73 N), Biodent K+B (247 ± 91 N to 218 ± 85 N), and Promysan/Vita Zeta (95 ± 15 N to 82 ± 6 N) groups (P <.05). Significant differences were obtained for the 4 and 5 unit Targis/Vectris FPDs compared with the Sinfony/Ribbond FPDs (281 ± 25 N − 252 ± 74 N) for the corresponding pontic spans. Conclusion. Within the limitations of this in vitro study the impregnated fiber reinforcement may considerably enhanced the fracture resistance of interim FPDs of different span lengths. (J Protshet Dent 2003;89:170-4.)