Abstract
Currently, there is no consensus in terms of defining the minimum radiant exposure values necessary for achieving adequate properties of composite resin. In addition, the long-term influence that radiant exposure has on the properties of composite resins is still questionable. Objective: The objective of this study was to evaluate the effect of radiant exposure and UV accelerated aging on the physico-chemical and mechanical properties of micro-hybrid and nanofilled composite resins. Material and Methods: A nanofilled (Filtek Supreme; 3M ESPE) and a micro-hybrid composite resin (Filtek Z250; 3M ESPE) were investigated under different radiant exposures (3.75, 9, and 24 J/cm2) and UV accelerated aging protocols (0, 500, 1000, and 1500 aging hours). The degree of conversion (DC), flexural strength (FS), modulus (M), water sorption (WS), and solubility (WL) were evaluated. The results obtained were analyzed using two-way ANOVA and Tukey's test. Comparisons were performed using a significance level of α=0.05. Results: The DC, FS, and M were found to be significantly influenced by both radiant exposure and accelerated aging time. The DC and EM increased with radiant exposure in the no-aging group (0-hour aging) for both micro-hybrid and nanofilled composites, whereas no correlation was found after accelerated aging protocols. WS and WL of micro-hybrid and nanofilled composite resins were scarcely affected by radiant exposure (p>0.05), whereas they were significantly reduced by accelerated aging (p<0.001). Conclusions: Although increasing radiant exposure affected the degree of conversion and mechanical properties of micro-hybrid and nanofilled composites, no influence on the hydrolytic degradation of the material was observed. In contrast, UV accelerated aging affected both the physico-chemical and mechanical properties of the composites.
Highlights
Dental resin-based composites comprise two major components: an organic matrix composed of monomers, an initiation system, accelerators, and inhibitors; and inorganic filler particles, as well as a silane derivative as coupling agents.1 Both organic and inorganic phases have an influence on the chemical, physical and mechanical properties of the composite
The degree of conversion from the composite resins was found to be significantly influenced by both radiant exposure (p
Regardless of the radiant exposure, the highest degree of conversion was achieved after aging for 1000 hours and the lowest was obtained with the 0-hour aging group for both micro-hybrid and nanofilled composites
Summary
Dental resin-based composites comprise two major components: an organic matrix composed of monomers, an initiation system, accelerators, and inhibitors; and inorganic filler particles, as well as a silane derivative as coupling agents. Both organic and inorganic phases have an influence on the chemical, physical and mechanical properties of the composite. Dental resin-based composites comprise two major components: an organic matrix composed of monomers, an initiation system, accelerators, and inhibitors; and inorganic filler particles, as well as a silane derivative as coupling agents.. Dental resin-based composites comprise two major components: an organic matrix composed of monomers, an initiation system, accelerators, and inhibitors; and inorganic filler particles, as well as a silane derivative as coupling agents.1 Both organic and inorganic phases have an influence on the chemical, physical and mechanical properties of the composite. Previous studies have established a direct relationship between the degree of conversion and the radiant exposure (J/cm2) emitted by the light source.4,5 On this basis, a common tendency among clinicians is to increase irradiance (mW/cm2) and/or exposure time (seconds) to use high radiant exposure levels during light curing.. The coupling agent used, and the characteristics of the filler (concentration, type, size, and distribution) can affect the overall properties of composites resins. the degree of conversion of the organic matrix is another determinant of several properties of restorative resins, being significantly correlated to many material characteristics, such as mechanical properties, polymerization shrinkage, wear resistance, and monomer elution. Considering this, any factor that affects the degree of conversion from composite resins can significantly influence their physico-chemical and mechanical properties.
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