IADR Abstract Archives
Flexural Strength of Zirconia-Based Fixed Dental Prostheses With Different Connector Designs
Objectives: Fixed dental prostheses (FDPs) with small connector size are required for optimal esthetics and limited inter-arch space; however, final strength is endangered.The purpose of this study was to evaluate the effect of different connector designs on the flexural strength of simulated three-unit zirconia-based (FDPs).
Methods: To simulate a three-unit (FDP), rectangular bar-shaped specimens were fabricated with the dimensions of 4x4x30-mm using CAD/CAM technology (n=20). Each bar specimen had two constricted parts at both sides representing the connector and defining a central pontic of 10-mm in length. The Specimens (n=5/gp) were divided according to the connector’s design as follows: group І: 2-mm(H) x3-mm(W), round (0.6-mm radius of curvature);groupІІ:2-mm(H)x3-mm(W),sharp (0.1-mm radius of curvature);group ІІІ:3-mm(H)x3-mm(W),round; and group ІV:3-mm(H)x3-mm(W),sharp. Additional specimens were fabricated with no constriction and served as the control (n=5). All specimens were subjected to a 3-point flexural strength test in a universal testing machine at a cross head speed of 0.5mm/min until failure. Two specimens from each group were selected for examination of the fracture pontic-connector interface under scanning electron microscope. The data were statistically analyzed (ANOVA, Tukey’s, (P = 0.05).
Results: Mean (SD) failure loads were 891.8 (57.9) MPa for the control group, 583.6 (49.7) MPa for group І, 486.7 (35.6) MPa for group ІІ, 682.9 (36.8) MPa for group ІІІ, 502.8 (23.3) MPa for group ІV. The two-way ANOVA results revealed that the connector diameter, shape and the interaction between the two variables had a statistically significant effect (P ≤ 0.05) on the mean flexural strength.
Conclusions: The minimum connector size for zirconia-based (FDPs) was 2-mm (H) x3-mm (W), provided the radius of curvature is round and not sharp
Methods: To simulate a three-unit (FDP), rectangular bar-shaped specimens were fabricated with the dimensions of 4x4x30-mm using CAD/CAM technology (n=20). Each bar specimen had two constricted parts at both sides representing the connector and defining a central pontic of 10-mm in length. The Specimens (n=5/gp) were divided according to the connector’s design as follows: group І: 2-mm(H) x3-mm(W), round (0.6-mm radius of curvature);groupІІ:2-mm(H)x3-mm(W),sharp (0.1-mm radius of curvature);group ІІІ:3-mm(H)x3-mm(W),round; and group ІV:3-mm(H)x3-mm(W),sharp. Additional specimens were fabricated with no constriction and served as the control (n=5). All specimens were subjected to a 3-point flexural strength test in a universal testing machine at a cross head speed of 0.5mm/min until failure. Two specimens from each group were selected for examination of the fracture pontic-connector interface under scanning electron microscope. The data were statistically analyzed (ANOVA, Tukey’s, (P = 0.05).
Results: Mean (SD) failure loads were 891.8 (57.9) MPa for the control group, 583.6 (49.7) MPa for group І, 486.7 (35.6) MPa for group ІІ, 682.9 (36.8) MPa for group ІІІ, 502.8 (23.3) MPa for group ІV. The two-way ANOVA results revealed that the connector diameter, shape and the interaction between the two variables had a statistically significant effect (P ≤ 0.05) on the mean flexural strength.
Conclusions: The minimum connector size for zirconia-based (FDPs) was 2-mm (H) x3-mm (W), provided the radius of curvature is round and not sharp
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