The effect of placement and quantity of glass fibers on the fracture resistance of interim fixed partial dentures

Purpose: Polymers used in interim fixed partial dentures (FPD) have recentl y been reinforced with fibers. The aim of this study was to determine the i nfluence of the position of the fiber reinforcement on the fracture resista nce of interim FPDs. In addition, the influence of quantity of fibers and t he length of span of the FPD on the fracture resistance was investigated. M aterials and Methods: FPDs were fabricated from a resin mixture of polyethy lmethacrylate powder and n-butylmethacrylate liquid. Five FPDs from each gr oup were made, and the FPDs were stored in water for 30 days before testing . The FPDs in the control group were unreinforced, and in the other groups the FPDs were reinforced either with two or three unidirectional continuous glass-fiber reinforcements and one woven glass-fiber reinforcement. Differ ent quantities of fibers were used and the fibers were placed in different locations in the FPD. The load was applied to the FPD by a steel ball place d in the cavity in the middle fossa of the pontic tooth. Results: The load required to fracture the unreinforced FPDs varied from 372 to 1061 IV. Mean fracture load of reinforced FPDs varied from 508 to 1297 N. One-way analys is of variance showed that the length of span and the quantity of fibers si gnificantly affected the fracture load (P < 0.001, n = 5). By lengthening t he span of the FPD, the reinforcing effect of glass fibers became more obvi ous. Conclusion: The results of this study suggest that the effectiveness o f glass-fiber reinforcement is most evident in interim FPDs with long spans and that the positioning of reinforcement considerably influences the stre ngth of the FPD.