The flexural strength of CAD/CAM polymer crowns and the effect of artificial ageing on the fracture resistance of CAD/CAM polymer and ceramic single crowns.

ABSTRACT

OBJECTIVES: The purpose of this study was to investigate the fracture resistance, flexural strength and Weibull modulus of an innovative CAD/CAM polymer and to compare its fracture resistance with that of glass ceramics. MATERIALS AND METHODS: A total of 32 (n = 16 IPS e.max CAD (LIDI); n = 16 LuxaCam Composite (LUXA)) first mandibular molar crowns were fabricated and cemented onto metal dies by use of luting composite. Half of the specimens were loaded until fracture without prior artificial ageing. The other half were subjected to thermal (5°/55 °C) and mechanical (1,200,000 cycles, 80 N) cycling before fracture loading. Scanning electron microscopy was used to analyse fracture behaviour. A three-point bending test of the flexural strength of LUXA was performed according to ISO 68722008. Data were analysed by means of the Kolmogorov-Smirnov test, Mann-Whitney U-test (p < 0.05) and Weibull statistical analysis. RESULTS: Initial fracture resistance of LIDI was significantly higher than that of LUXA. However, the initial fracture resistance of LIDI decreased significantly after artificial ageing. After ageing, fracture resistance was 1050.29 ± 325.08 N for LUXA and 1250.09 ± 32.53 N for LIDI. Three-point bending test yielded a mean flexural strength value for LUXA of 145.28 ± 18.21 MPa and a Weibull modulus of m = 9.51. CONCLUSIONS: Polymer-based material tested in this study had a lower fracture resistance than that of the glass-ceramic material. Fracture resistance and flexural strength of LuxaCam Composite are sufficient for use in the first molar region. CLINICAL RELEVANCE The mechanical properties of this innovative polymer-based material indicate it can be used in the first molar region as a suitable alternative to glass ceramics. Further clinical studies are required to confirm this. The study presents an innovative material as an alternative to glassceramic for the clinical use in dentistry. The materials investigated were differently affected by artificial aging. Clinical use for patients with bruxism may be considered.