title: Influence of ceramic thickness and ceramic materials on fracture resistance of posterior partial coverage restorations.
abstract: This study evaluated the influence of ceramic thickness and ceramic materials on fracture resistance of posterior partial coverage ceramic restorations. Forty extracted molars were allocated into four groups (n=10) to test for two variables: 1) the thickness of ceramic (1 mm or 2 mm) and 2) the ceramic materials (a lithium disilicate glass-ceramic [IPS e.max] or leucite-reinforced glass ceramic [IPS Empress]). All ceramic restorations were luted with resin cement (Variolink II) on the prepared teeth. These luted specimens were loaded to failure in a universal testing machine, in the compression mode, with a crosshead speed of 1.0 mm/min. The data were analyzed using two-way analysis of variance and the Tukey Honestly Significantly Different multiple comparison test (α =0.05). The fracture resistance revealed a significant effect for materials (p<0.001); however, the thickness of ceramic was not significant (p=0.074), and the interaction between the thickness of ceramic and the materials was not significant (p=0.406). Mean (standard deviation) fracture resistance values were as follows: a 2-mm thickness of a lithium disilicate bonded to tooth structure (2505 [401] N) revealed a significantly higher fracture resistance than did a 1-mm thickness of leucite-reinforced (1569 [452] N) and a 2-mm thickness of leucite-reinforced ceramic bonded to tooth structure (1716 [436] N) (p<0.05). There was no significant difference in fracture resistance values between a lithium disilicate ceramic at 1-mm thickness (2105 [567] N) and at 2-mm thickness. Using a lithium disilicate glass ceramic for partial coverage restoration significantly improved fracture resistance compared to using a leucite-reinforced glass ceramic. The thickness of ceramic had no significant effect on fracture resistance when the ceramics were bonded to the underlying tooth structure.
authors.forename: E M
authors.initials: EM
authors.lastname: Bakeman
authors.forename: N
authors.initials: N
authors.lastname: Rego
authors.forename: Y
authors.initials: Y
authors.lastname: Chaiyabutr
authors.forename: J C
authors.initials: JC
authors.lastname: Kois
mesh_terms: D000538:Aluminum Silicates / Q000627:therapeutic use; D002516:Ceramics / Q000009:adverse effects / Q000627:therapeutic use*; D003764:Dental Materials / Q000009:adverse effects / Q000627:therapeutic use*; D003776:Dental Porcelain / Q000627:therapeutic use; D019232:Dental Restoration Failure; D003793:Dental Restoration, Permanent / Q000009:adverse effects / Q000379:methods*; D003799:Dental Stress Analysis; D006801:Humans; D008963:Molar / Q000601:surgery
chemical_list: D000538:Aluminum Silicates; D003764:Dental Materials; C493120:lithia disilicate; D003776:Dental Porcelain; C078519:leucite; C023506:Glass ceramics