Abstract: Objective To investigate the relationship between the cross-sectional area of different connectors and the fracture resistance of three-unit polyetheretherketone fixed bridge , and discuss the minimum cross-sectional area of the connectors. Methods 30 pieces of freshly isolated teeth in the mandibular molar area were selected to make 15 pairs of models, which were randomly divided into three groups(A、B and C) with 5 in each group. The cross - sectional areas were respectively 5.0 mm2, 7.0 mm2 and 9.0 mm2 by CAD/CAM systems. The actual cross-sectional area of the connector was measured by vernier caliper. The fixed bridge was put on the model, fracture load was measured, the maximum load was recorded automatically by the computer , and the damage mode of the fixed bridge was observed. Results The average actual cross-sectional areas of three groups(A、B and C) were 5.40 mm2 ,7.62 mm2 and 9.73 mm2 respectively, the fracture resistances were (657.44+45.17) N, (877.94+71.11) N and (1244.64 +62.38) N. The one-way ANOVA and SNK revealed that there were statistically significant differences in fracture resistance between cross-sectional areas（P＜0.05）. The connectors of the fixed bridge was completely broken. Conclusions The connector is the weak area of the fixed bridge, and the fracture resistance of the fixed bridge can be increased by increasing the cross-sectional area of the connector. It is recommended that the cross-sectional area of three-unit polyetheretherketone fixed bridge be≥7.62 mm2.

Key words: polyetheretherketone, fixed bridge, fracture resistance, CAD/CAM