Effect of temperature, curing time, and filler composition on surface microhardness of composite resins

Abstract

Aim:The aim of this study was to evaluate the microhardness of two composite resins when subjected to three different temperatures and three different light-curing times.Materials and Methods:Two composites were used; Filtek Z250 and Grandio. Three different temperatures (23, 37, and 55oC) were used, utilizing a composite warmer. The heated samples were immediately injected into cylindrical molds (6 mm × 2 mm) and the top surface of the specimens was polymerized for 10, 20, and 40 sec, using a Quartz-Tungsten-Halogen light-curing unit (QTH LCU). Vickers microhardness measurements were performed from both the top and bottom surface of the specimens, following dry storage for 24 hours in the dark. Statistical analysis were performed using one-way analysis of variance (ANOVA) and Tukey post-hoc test at a level of significance of a = 0.05.Results:The results indicated that there was an increase in microhardness as the temperature of the composite was increased for either the top or the bottom surface (P < 0.05). Furthermore, there was a general increase in microhardness for both composites as curing time increased (P < 0.05). The type of composites did not influence the surface microhardness (P > 0.05).Conclusions:Temperature of composites affects their surface microhardness. Also, light-curing time influence microhardness values of the composites tested.

Effect of preheating and shade on surface microhardness of silorane‐based composites

“…According to the results of the present study, the first null hypothesis, which states that there are no differences in surface microhardness between the preheated composite resin specimens and those which are light‐cured at room temperature, has to be rejected. This is in agreement with previous reports, which investigated the effect of composite preheating on the degree of conversion . The increase of temperature reduces viscosity, raises liquidity, enhances free radical mobility, and increases collision frequency between the active group and free radicals.…”

“…This is in agreement with previous reports, which investigated the effect of composite preheating on the degree of conversion. [14][15][16][17] The increase of temperature reduces viscosity, raises liquidity, enhances free radical mobility, and increases collision frequency between the active group and free radicals. As a result, the degree of conversion improves, and this evidence is expressed by the increased microhardness of the composite material.…”

The Effect of Composition, Temperature and Post-Irradiation Curing of Bulk Fill Resin Composites on Polymerization Efficiency

“…The results obtained from this study demand partially rejection of the Ho2, which states that there were no differences in microhardness of the RBC materials when polymerized either at 23 o C or 54 o C. The results coincide with those of previous investigators, who found that preheating of resin composites increases their degree of conversion 13,23,24 . Despite the fact that the results of this investigation showed a slight increase in micohardness after preheating for all the materials but in different extent ranged from 1.12% to 18.58%, in some cases this slight increase was not statistically significant.…”

“…Many parameters may affect the degree of polymerization of bulk fill RBCs such as their composition (photoinitiators, fillers and organic matrix) 6 , the technical characteristics of the light-curing unit (light intensity, thermal emission, wave length range, diameter of the tip) and the conditions of photo-polymerization (curing mode and exposure time) 22 , the post-irradiation period 21 , the temperature 23,24 and the incremental thickness of the material 25 . As statistical analysis revealed the existence of significant differences among the tested bulk fill RBCs with regard to microhardness, the formulated Ho1, which states that there were no differences in microhardness among the RBC materials of the same measurement depth, had to be rejected.…”

Efficiency of polymerization of bulk-fill composite resins: a systematic review

“…Quality assessment scores concerning study design: methodological soundness (maximum score = 8 points). 40 the technical characteristics of the lightcuring unit (light intensity, thermal emission, wave length range, diameter of the tip) and the conditions of photo-polymerization (curing mode and exposure time), 41 the post-irradiation period, 42 the temperature, 43,44 and the incremental thickness of the material. 45 Therefore, the articles were scored in order to analyze the study design and the methodological reliability, based on the mechanical test performed and on the degree of technical information available.…”