Abstract
Aims: The aims of this in vitro study were to evaluate the effect of different temperatures of the pre- cured composite resin materials on the degree of conversion and knoop microhardness of cured composite resin. Materials and Methods : A forty five disc-shaped specimens were prepared from ( Ceram X, shade D2, Dentsply/ Caulk, USA) after stored for 24h in different temperatures ( 5,25,and 37°C) were light cured for 40s. The FTIR test was used to measure the degree of conversion for each specimen. The knoop microhardness was measured by the use of (WOLPERT-WERKE-GMBH Baujahr Testor, GERMANY) (Vickers hardness test) for each specimen. Data obtained was analyzed using one-way analysis of variance (ANOVA) and Duncan's test at a 0.05 significance level.Results : The statistical analysis of the results (ANOVA) showed that there was statistically significant difference in the degree of conversion and in the microhardness of the prepared samples at the different temperature. As the temperature of the composite resin increase, there was an increase in the degree of conversion and increase in the micro hardness of the samples.Conclusions : The use of pre-warmed composite resin may help to improve the degree of conversion and the micro hardness of composite resin especially at the deeper areas of a restoration which could result in an increase in the expected life of a composite restoration.
Highlights
IntroductionLight-cured resin composites are widely used in dental restorations. These resins are polymerized by a light-curing unite (LCU) and the degree of conversion (DC) of dental resins can be determined using Fourier Transform-Infrared Spectroscopy (FTIR).(1,2) In addition, Knoop-P microhardness has been shown to be a reliable method to determine how well a resin is cured (3) and a good correlation has been reported between the knoopmicrohardness and both the DC (4,5) and theYoung's modulus.(6) The overall rate of polymerization of resins is determined by the rates of the initiation, propagation and www.rafidaindentj.netThe effect of pre-cured temperature of composite resin on the degree of conversion and micro hardness of composite resin termination phases of the reaction
Light-cured resin composites are widely used in dental restorations. These resins are polymerized by a light-curing unite (LCU) and the degree of conversion (DC) of dental resins can be determined using Fourier Transform-Infrared Spectroscopy (FTIR).(1,2) In addition, Knoopmicrohardness has been shown to be a reliable method to determine how well a resin is cured (3) and a good correlation has been reported between the knoopmicrohardness and both the DC (4,5) and the
The rate of polymerization of filled dental resins is further accelerated by the Trommsdrof effect, where in the marked increased in the viscosity of the filled resin material during gel- ation increases the mobility of large polymer radicals
Summary
Light-cured resin composites are widely used in dental restorations. These resins are polymerized by a light-curing unite (LCU) and the degree of conversion (DC) of dental resins can be determined using Fourier Transform-Infrared Spectroscopy (FTIR).(1,2) In addition, Knoop-P microhardness has been shown to be a reliable method to determine how well a resin is cured (3) and a good correlation has been reported between the knoopmicrohardness and both the DC (4,5) and theYoung's modulus.(6) The overall rate of polymerization of resins is determined by the rates of the initiation, propagation and www.rafidaindentj.netThe effect of pre-cured temperature of composite resin on the degree of conversion and micro hardness of composite resin termination phases of the reaction. The rate of polymerization of filled dental resins is further accelerated by the Trommsdrof effect, where in the marked increased in the viscosity of the filled resin material during gel- ation increases the mobility of large polymer radicals. This effectively reduces the termination rate constant at a given temperature and accelerates the reaction. (20) Trujillo et al, (21) found an elevated temperature of composite resin during photo polymerization resulted in substantially higher immediate and final conversion values of all composite resin materials tested in their study along with a concomitant improvement in fracture resistance and a 50% or more reduction in curing time. It is possible to use a highly filled pre-warmed packable hybrid composite at gingival margins in a deep restoration while eliminating poor marginal adaptation
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