Journal of dentistry · 2025
Influence of test velocity and viscoelasticity on the outcome of the 3-point bending test in modern dental polymer-based composites.
СтатьяПоддержка исследования: вне правительства СШАНазвание и аннотация: Перевод в очереди
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Ilie Nicoleta
Аннотация
OBJECTIVES: Polymer-based dental composites are considered brittle materials due to their very high filler content. At the same time, the polymer matrix itself and the complex interface between the reinforcing fillers and the polymer matrix induce pronounced viscoelastic behavior. The aim of the study was to relate the variations in the outcome of a 3-point bending test at different crosshead speeds to the viscoelastic material behavior, reliability, and an inherent parameter determined by quantitative fractography.
METHODS: A series of three-point bending tests were conducted at crosshead speeds ranging from 0.05 mm/min to 10 mm/min. Variations in strength, elastic modulus, beam deflection and mechanical work were determined for 200 specimens (n = 20) and five crosshead speeds in two different composites. Quantitative and qualitative fractography were used to determine the fracture type and origin. The mirror constant was calculated using the Orr equation. Viscoelastic behaviour was determined using dynamic mechanical analysis (DMA) on frequencies covering human masticatory activity. One and multiple-way analysis of variance (ANOVA), Tukey honestly significant difference (HSD) post-hoc tests (α=0.05) were applied.
RESULTS: Crosshead speed influences the flexural strength significantly. Sensitivity and extent of variation depend on the viscoelastic behavior and are more distinct in materials with pronounced viscoelastic behavior. Elastic modulus, reliability, and mirror constant are speed-independent.
CONCLUSIONS: The results highlight the limitations of purely quasi-static tests and underscore the need for a more detailed investigation of the mechanical behaviour of composites to include DMA.
CLINICAL STATEMENT: Composites with improved damping behavior, i.e. better adapted to mechanical impacts, combined with high mechanical parameters, would be preferable for better adaptation to clinical situations.
METHODS: A series of three-point bending tests were conducted at crosshead speeds ranging from 0.05 mm/min to 10 mm/min. Variations in strength, elastic modulus, beam deflection and mechanical work were determined for 200 specimens (n = 20) and five crosshead speeds in two different composites. Quantitative and qualitative fractography were used to determine the fracture type and origin. The mirror constant was calculated using the Orr equation. Viscoelastic behaviour was determined using dynamic mechanical analysis (DMA) on frequencies covering human masticatory activity. One and multiple-way analysis of variance (ANOVA), Tukey honestly significant difference (HSD) post-hoc tests (α=0.05) were applied.
RESULTS: Crosshead speed influences the flexural strength significantly. Sensitivity and extent of variation depend on the viscoelastic behavior and are more distinct in materials with pronounced viscoelastic behavior. Elastic modulus, reliability, and mirror constant are speed-independent.
CONCLUSIONS: The results highlight the limitations of purely quasi-static tests and underscore the need for a more detailed investigation of the mechanical behaviour of composites to include DMA.
CLINICAL STATEMENT: Composites with improved damping behavior, i.e. better adapted to mechanical impacts, combined with high mechanical parameters, would be preferable for better adaptation to clinical situations.