Vivian Marie Ducke1, Nicoleta Ilie2. 1. Department of Conservative Dentistry and Periodontology, University Hospital, LMU Munich, Germany. Electronic address: vivian.ducke@campus.lmu.de. 2. Department of Conservative Dentistry and Periodontology, University Hospital, LMU Munich, Germany.
Abstract
OBJECTIVE: The aim of this study was to investigate the influence of artificial aging on the mechanical properties and fracture patterns of novel CAD/CAM resin-based composite blocks (RCB). METHODS: Flexural strength and modulus of RCBs from seven manufacturers (Voco, Grandio Blocs, GB; Ivoclar Vivadent, Tetric®CAD, TC; DMG, Luxacam Composite, LC; Shofu Block HC, SF; 3M, Lava™ Ultimate, LU; GC, Cerasmart®, CS; Coltene, BRILLIANT Crios, CB) were assessed in a three-point-bending test after an aging process consisting of three sequential steps (14 days storage in artificial saliva, 10,000 thermo-cycles in distilled water between 5/55 °C, 48 h storage in ethanol 75%). Fracture origins were determined in a fractographic examination using reflected light stereomicroscopy combined with transillumination and scanning electron microscopy. Effects of aging were statistically analysed using one-way ANOVA with Tukey's HSD post hoc test (α = 0.05) and Weibull statistics. Correlations regarding filler amount were analysed using linear regression analysis. RESULTS: The strongest influence on the flexural modulus and strength was exerted based on the parameter material (p < 0.001, ɳP2 = 0.957; ɳP2 = 0.770), but the influence of in vitro aging was also significant (p < 0.001, ɳP2 = 0.623; ɳP2 = 0.407). Storage in artificial saliva decreased the flexural modulus and flexural strength of all materials, apart from CS, significantly (p < 0.05). The Weibull moduli varied from 5.8 to 22.4. Filler amount correlated significantly with flexural modulus (p < 0.001; R2 = 0.739). Fractography revealed four different fracture patterns with fracture origins from the corner, edge or sub-surface and a smooth fracture surface with non-identifiable fracture origin. Specimens with smooth fracture surface showed the significantly lowest flexural strength (p < 0.001). Pores, agglomerates and inclusions were identified as fracture origins. CONCLUSIONS: Storage in artificial saliva mainly reduced the mechanical properties significantly while additional thermal aging mostly maintained the results. Aging in ethanol mostly maintained the results for flexural modulus but led to an increase in flexural strength values to the level of the unaged specimens. Fractographic analysis revealed a significant accumulation of sub-surface fracture origins after storage in ethanol arising from inherent flaws.
OBJECTIVE: The aim of this study was to investigate the influence of artificial aging on the mechanical properties and fracture patterns of novel CAD/CAM resin-based composite blocks (RCB). METHODS: Flexural strength and modulus of RCBs from seven manufacturers (Voco, Grandio Blocs, GB; Ivoclar Vivadent, Tetric®CAD, TC; DMG, Luxacam Composite, LC; Shofu Block HC, SF; 3M, Lava™ Ultimate, LU; GC, Cerasmart®, CS; Coltene, BRILLIANT Crios, CB) were assessed in a three-point-bending test after an aging process consisting of three sequential steps (14 days storage in artificial saliva, 10,000 thermo-cycles in distilled water between 5/55 °C, 48 h storage in ethanol 75%). Fracture origins were determined in a fractographic examination using reflected light stereomicroscopy combined with transillumination and scanning electron microscopy. Effects of aging were statistically analysed using one-way ANOVA with Tukey's HSD post hoc test (α = 0.05) and Weibull statistics. Correlations regarding filler amount were analysed using linear regression analysis. RESULTS: The strongest influence on the flexural modulus and strength was exerted based on the parameter material (p < 0.001, ɳP2 = 0.957; ɳP2 = 0.770), but the influence of in vitro aging was also significant (p < 0.001, ɳP2 = 0.623; ɳP2 = 0.407). Storage in artificial saliva decreased the flexural modulus and flexural strength of all materials, apart from CS, significantly (p < 0.05). The Weibull moduli varied from 5.8 to 22.4. Filler amount correlated significantly with flexural modulus (p < 0.001; R2 = 0.739). Fractography revealed four different fracture patterns with fracture origins from the corner, edge or sub-surface and a smooth fracture surface with non-identifiable fracture origin. Specimens with smooth fracture surface showed the significantly lowest flexural strength (p < 0.001). Pores, agglomerates and inclusions were identified as fracture origins. CONCLUSIONS: Storage in artificial saliva mainly reduced the mechanical properties significantly while additional thermal aging mostly maintained the results. Aging in ethanol mostly maintained the results for flexural modulus but led to an increase in flexural strength values to the level of the unaged specimens. Fractographic analysis revealed a significant accumulation of sub-surface fracture origins after storage in ethanol arising from inherent flaws.
Authors: Damian S Nakonieczny; Magdalena Antonowicz; Thomas Heim; Andrzej S Swinarew; Paweł Nuckowski; Krzysztof Matus; Marcin Lemanowicz Journal: Polymers (Basel) Date: 2022-06-09 Impact factor: 4.967