Effect of two connector designs on the fracture resistance of all-ceramic core materials for fixed dental prostheses

• Published in: The Journal of prosthetic dentistry 2009-03, Vol.101 (3), p.166-173
• Main Authors: Plengsombut, Kwansiri, DDS, MS, Brewer, Jane D., DDS, MS, Monaco, Edward A., DDS, Davis, Elaine L., PhD
• Format: Article
• Language: English
• Subjects: Analysis of Variance; Ceramics; Dental Clasps; Dental Porcelain; Dental Restoration Failure; Dental Stress Analysis; Dentistry; Denture Design; Denture, Partial, Fixed; Humans; Materials Testing; Tensile Strength
• ISSN: 0022-3913; 1097-6841
• DOI: 10.1016/S0022-3913(09)60022-6

Statement of problem Most all-ceramic fixed dental prostheses (FDPs) fail at the connectors. Purpose The purpose of this study was to determine the effect of 2 connector designs on the fracture resistance of core materials used for all-ceramic FDPs. Material and methods Three materials were tested: (1) heat-pressed lithium disilicate glass ceramic (IPS e.max Press (Press)), (2) milled lithium disilicate glass ceramic (IPS e.max CAD (CAD)), and (3) milled yttrium-stabilized tetragonal zirconia polycrystals (Y-TZP) (IPS e.max ZirCAD (ZirCAD)). Specimens were made into 30 × 4 × 4-mm bars to represent 3-unit FDPs. Two connector designs, round (0.60 ±0.01-mm radius of curvature) and sharp (0.06 ±0.001-mm radius of curvature), with a 3.00 ±0.05-mm cross-section for each connector, were studied (n=5). Each specimen was loaded to fracture in a universal testing machine with a crosshead speed of 0.1 mm/min. Data were analyzed with a 2-way univariate ANOVA and Tukey HSD test (α=.05). Results Mean (SD) failure loads for round connector designs were 684.2 (70.1) N for ZirCAD, 260 (7.8) N for CAD, and 172.9 (35.5) N for Press. Mean (SD) failure loads for sharp connector designs were 386.3 (51.5) N for ZirCAD, 87.9 (7.0) N for CAD, and 125.1 (15.1) N for Press. The 2-way univariate ANOVA indicated statistically significant differences ( P