OBJECTIVES: To compare the bond strength of a ceramic veneer material to two different ceramic core materials using shear strength testing and finite element analysis (FEA). METHODS: 15 blocks of ceramic cores were made of each of IPS e.max ZirCAD (Ivoclar-Vivadent, Schaan, Liechtenstein) (ZirCAD) and lithium disilicate IPS e.max CAD (LS). These were veneered using IPS e.max Ceram (Ceram) according to the manufacturers' instructions. Samples were then mounted, placed inside a shear testing jig and loaded at their core/veneer interfaces with a universal testing machine. Fractured specimens were then examined fractographically at 45×. An independent t-test and a Mann-Whitney U test were used to detect differences in bond strengths and the patterns of failure between the two groups, respectively (p>0.05). Two-dimensional plane stress FE-models were constructed and subjected to shear loading simulating the experimental conditions. RESULTS: Mean shear stresses (MPa) were 28.8 (9.5) for ZirCAD/Ceram and 29.1 (8.3) for LS/Ceram. Differences were not statistically significant. Fracture patterns were significantly different between the 2 groups as all ZirCAD/Ceram samples broke adhesively at their interface while LS/Ceram samples broke cohesively in the veneer or the core or had mixed adhesive/cohesive failure. Stress distributions in the FEA models were also different, corresponding to the variable fracture patterns in the 2 groups. SIGNIFICANCE: Although shear stresses were similar, fractographic analysis and finite element modeling suggested better bonding between the veneering ceramic and the glass-ceramic than to the zirconia cores. Improved bonding techniques are necessary to prevent clinical delamination of veneered zirconia restorations.
OBJECTIVES: To compare the bond strength of a ceramic veneer material to two different ceramic core materials using shear strength testing and finite element analysis (FEA). METHODS: 15 blocks of ceramic cores were made of each of IPS e.max ZirCAD (Ivoclar-Vivadent, Schaan, Liechtenstein) (ZirCAD) and lithium disilicate IPS e.max CAD (LS). These were veneered using IPS e.max Ceram (Ceram) according to the manufacturers' instructions. Samples were then mounted, placed inside a shear testing jig and loaded at their core/veneer interfaces with a universal testing machine. Fractured specimens were then examined fractographically at 45×. An independent t-test and a Mann-Whitney U test were used to detect differences in bond strengths and the patterns of failure between the two groups, respectively (p>0.05). Two-dimensional plane stress FE-models were constructed and subjected to shear loading simulating the experimental conditions. RESULTS: Mean shear stresses (MPa) were 28.8 (9.5) for ZirCAD/Ceram and 29.1 (8.3) for LS/Ceram. Differences were not statistically significant. Fracture patterns were significantly different between the 2 groups as all ZirCAD/Ceram samples broke adhesively at their interface while LS/Ceram samples broke cohesively in the veneer or the core or had mixed adhesive/cohesive failure. Stress distributions in the FEA models were also different, corresponding to the variable fracture patterns in the 2 groups. SIGNIFICANCE: Although shear stresses were similar, fractographic analysis and finite element modeling suggested better bonding between the veneering ceramic and the glass-ceramic than to the zirconia cores. Improved bonding techniques are necessary to prevent clinical delamination of veneered zirconia restorations.
Authors: Márcia Borba; Maico D de Araújo; Erick de Lima; Humberto N Yoshimura; Paulo F Cesar; Jason A Griggs; Alvaro Della Bona Journal: Dent Mater Date: 2011-10-06 Impact factor: 5.304
Authors: Hugo-Alberto Vidotti; Jefferson-Ricardo Pereira; Elizeu Insaurralde; Luiz F Plaça; José R Delben; Accácio-Lins do Valle Journal: J Clin Exp Dent Date: 2017-08-01