Porcelain Fracture Resistance in Metal-Ceramic Crowns with Different Veneer Thickness
Date Issued
2008
Date
2008
Author(s)
Chin, Chun-Cheong
Abstract
Purpose: Fracture of ceramic veneers is frequently observed in clinical practice and poses an esthetic and functional dilemma both for the patient and the dentist. The purpose of this study was to compare the porcelain fracture resistance between two different thickness of porcelain on the cement-retained implant metal-ceramic crowns. Material and methods: Forty (8×8×8 mm, W×H×L) cubic-shaped single metal-ceramic crowns were fabricated with two different thickness (1.5 mm or 2.5 mm) of porcelain and divided into four groups (10 crowns each): Groups 1 & 3 (1.5 mm), Groups 2 & 4 (2.5 mm). All the samples were cemented on 1mm Easy abutment above a Brånemark RP implant analog embedded in a 30×30×84 mm type IV die stone block. Groups 3 & 4 were first exposed to a vertically dynamic loading of 80N for 100,000 cycles to simulate masticatory function at mesial marginal ridge of the occlusal surface. Afterwards, all the samples were positioned in a custom testing apparatus and vertically loaded on the mesial marginal ridge of the occlusal surface with a universal testing machine (Instron 5566) at a crosshead speed of 0.5 mm/min until fracture. SEM fractographic analysis was utilized to determine the fracture patterns. Mean values of load at fracture (kgf) were recorded in each group and compared with a 2-way ANOVA and independent t-test (p<0.05)(factors: porcelain thickness, with/without dynamic loading).esults: 1. No obvious ceramic fracture except digging pits was observed in Groups 3 & 4 after dynamic loading. 2. Mean values of loads required to fracture the crowns were as follow: Group 1: 129.63 ± 12.65 kgf; Group 2: 116.08 ± 10.83 kgf; Group 3: 84.18 ± 3.98 kgf; Group 4: 66.94 ± 11.05 kgf. 3. Dynamic loading prior to fracture test reduced the mean fracture loads significantly in Groups 3 & 4. 4. Cohesive or adhesive fracture of the porcelain can be observed in all four groups in fracture test.onclusions: From a clinical viewpoint, to diminish the porcelain thickness of about 1.5mm, can decrease the probability of porcelain fracture of metal-ceramic crowns.
Subjects
fracture resistance
metal-ceramic crowns
veneer
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