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UBC Theses and Dissertations

Mechanical properties of dental resin composite CAD/CAM blocks Thornton, Ian


Objective: The goal of this study was to determine the flexural strength (σf), flexural modulus (Ef) and fracture toughness (KIC) of two new commercially available nano-ceramic resin composite CAD/CAM blocks (Lava Ultimate and Enamic) and compare them to those of a widely-used ceramic CAD/CAM block (IPS e.max), that served as a control, in order to evaluate the clinical suitability of the former. Materials and Methods: Fifty bars of Lava Ultimate and Enamic and twenty-five bars of e.max were made for three-point bending testing (to determine σf and Ef). Testing was completed on an Instron machine whereby a force was applied at a constant crosshead speed of 1 mm/min until failure occurred. Twenty-four 6x6x6x12 mm equilateral triangular prisms were fabricated from Lava Ultimate and Enamic and twelve from e.max for fracture toughness (KIC) testing using the notchless triangular prism specimen (NTP) KIC test. Half of the prepared Lava Ultimate and Enamic samples were stored in 37°C water for 30 days prior to testing, to analyze the aging effect. Weibull statistics were used to evaluate the characteristic strength and the reliability of each material. Two-way ANOVA and post-hoc Scheffé comparisons were used to further analyze the results. Results: The σf, Ef and KIC of Lava Ultimate and Enamic were considerably lower than that of IPS e.max. Aging of Lava Ultimate and Enamic lowered the σf by 27 % and 12 % but increased the KIC by 10 % and 40 %, respectively. Aging also significantly lowered Ef of both samples. The σf of Enamic was statistically significantly lower than that of Lava Ultimate, while the Ef of Enamic was statistically significantly higher. Only in the aged samples were significant differences between KIC detected. Conclusion: When compared to conventional resin composites, the presence of ceramic nano-particles in Lava Ultimate and Enamic did not greatly improve σf or KIC of these materials. The flexural modulus of Enamic was greatly improved to levels not seen before in dental resin composites. Based on the mechanical testing results obtained in this study, their consideration and clinical use should be similar to that of conventional dental resin composites.

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