Study On The Effect Of Different Connection Area On The Flexural Strength Of Three-unit Polyetheretherketone Fixed Bridge

Objectives:To investigate the effect of different connection area on the flexural strength of three-unit PEEK fixed bridge,and discuss minimum area of the connectors.At the same time,to provide theoretical basis for researchers and clinical medical staffs to select PEEK materials.Methods:30 pieces of freshly isolated teeth in the mandibular molar area were selected to be made into model of three-unit fixed bridge 15 pairs,we used silicone rubber impression material to simulate the periodontal membrane of 0.35mm thickness,and they were randomly divided into three groups(A、B and C)with 5 in each group.The cross-sectional area was 5.0mm~2(The occluso-gingival height=The buccolingual width=2.52mm),7.0mm~2(The occluso-gingival height = The buccolingual width=2.99mm)and 9.0mm~2(The occluso-gingival height = The buccolingual width=3.3 9mm)by CAD/CAM system,and the cross-sectional shape of the connector was designed to assume a circular shape.The actually cross-sectional area of the connector was measured by vernier caliper.The fixed bridge was put on the model,fracture load was measured by Universal material testing Machine,the maximum load was recorded automatically by the computer,and the damage mode of the fixed bridge was observed.The date were analysed by SPSS 17.0 statistical software,Whether there is statistical significance by the one-way ANOVA between cross-sectional area and the fracture resistance when the experimental data conform to normal distribution and homogeneity of variance(P<0.05,α=0.05),if the one-way ANOVA revealed statistically significant differences in fracture resistance and cross-sectional areas,and then we used SNK to compare the data(a=0.05).Results:The average actually cross-sectional area of three groups(A、B and C)was 5.40 mm~2,7.62 mm~2 and 9.73 mm~2;the average actually occluso-gingival height was 2.63mm、3.09mm and 3.53mm;the average actually buccolingual width was 2.55mm、3.09mm and 3.45mm;the fracture resistance was 609.84N～711.94 N,812.78 N～970.00 N and 1163.63 N～1330.44 N;the average fracture resistance was(657.44 ± 45.17)N,(877.94 ± 71.11)N and(1244.64 ± 62.38)N.The one-way ANOVA and SNK revealed statistically significant differences in fracture resistance between cross-sectional areas(P<0.05).Observing all prostheses with the eye,we found that the cracks mainly occurred at two locations of the prosthesis,one was the crack in the gingival side near the bridge,the cracks diffuses to the loading point,and the other was the vertical crack at the near bottom crown of the connector.Conclusions:1.Effect of the connection area on the flexural strength of Three-unit PEEK fixed bridge,and the flexural strength of the fixed bridge can be increased by increasing the connection area.2.In clinical practice,the connection area of the three-unit PEEK fixed bridgeshould be greater than 7.62 mm~2.