Influence of a blue DPSS laser on specimen thickness of composite resins.

OBJECTIVE: The purpose of the present study was to investigate the effect of 473 nm diode-pumped solid state (DPSS) laser on the curing depth of composite resins. BACKGROUND DATA: Within the turbid media, light attenuates significantly because of the absorption and scattering. MATERIALS AND METHODS: For the study, three different composite resins and light-curing units (LCUs) (a quartz-tungsten-halogen [QTH], light-emitting-diode [LED], and DPSS laser) were used. The number of photons transmitted through the specimens, degree of conversion (DC), microhardness, and refractive index of the specimens on different thicknesses were evaluated. RESULTS: The incident light exponentially decreased within the specimens. Among the LCUs, QTH showed the least photon loss. The DC obtained using the DPSS laser and QTH was significantly greater (p<0.001) than that obtained using LED. The specimens light cured using the DPSS laser showed slightly lower microhardness than that cured by the other LCUs. On each depth, the mean refractive index was not significantly different for the LCUs used. DC, microhardness, and refractive index had inverse linear correlation with specimen thickness despite exponential decrease of photons number. On the other hand, DC, microhardness, and refractive index were linearly correlated to each other regardless of LCUs. CONCLUSIONS: The DPSS laser of 473 nm achieved a similar level of polymerization within the specimens as those of the other LCUs even with much lower light intensity. This laser can be applied as a light source for light curing of composite resins.

Influence of DPSS laser on polymerization shrinkage and mass change of resin composites.

OBJECTIVES: This study evaluated the effectiveness of the diode-pumped solid state (DPSS) laser as a light source for light-curing dental resin composites. BACKGROUND DATA: A DPSS laser of 473 nm may be useful because of its match with the absorption peak of camphorquinone (CQ), the photoinitiator. MATERIALS AND METHODS: A DPSS laser (LAS) of 473 nm and a quartz-tungsten-halogen (QTH) light-curing unit (OP) were used as the light sources for light curing six different resin composites (four nanocomposites and two hybrid composites). Polymerization shrinkage and mass change (water sorption and solubility) were measured during and after light curing to determine the degree of polymerization. Mass change was evaluated by following the ISO 4049 standard. RESULTS: According to the evaluation, the specimens light cured using LAS showed similar maximum polymerization shrinkage (12.3∼18.1 µm for LAS; 13.2∼16.2 µm for OP) and water sorption (11.4∼24.1 µg/mm(3) for LAS; 11.3∼22.8 µg/ mm(3) for OP) to the cases light cured using OP. The specimens light cured using LAS showed a significantly higher solubility than the cases light cured using OP (2.4∼6.6 µg/ mm(3) for LAS; 0.8∼1.6 µg/ mm(3) for OP). However, the maximum water sorption and solubility obtained from the specimens were lower than the values permitted by the ISO 4049 standard. CONCLUSIONS: The results may suggest that the DPSS laser with an emission wavelength of 473 nm can be used as a light source for light-curing dental resin composites.

Influence of blue laser on water sorption and solubility of flowable resins.

OBJECTIVE: The aim of this study was to investigate the water sorption and solubility of flowable resins light cured using a blue diode-pumped solid-state (DPSS) laser. BACKGROUND DATA: DPSS lasers have many advantages over conventional lasers due to their compactness, efficiency, and price. MATERIALS AND METHODS: The water sorption and solubility of seven different flowable resins were measured by following ISO 4049 procedures. The specimens were light cured using two different light sources: 473-nm DPSS laser (LAS) and quartz tungsten halogen (QTH) light (OP). The light-cured specimens were immersed in distilled water for 7 days. The output light intensity of LAS and OP were 500 and 800 mW/cm(2) respectively. ANOVA was performed for the statistical analysis of the obtained data (p < 0.05). RESULTS: The specimens light cured using LAS and OP showed no statistical difference between them regarding water sorption and solubility (almost the same values with the same product). The maximum water sorption from the specimens was not more than 40 µg/mm(3). Also, the maximum solubility was close to 7.5 µg/mm(3). These two values were the maximum limits allowed by ISO 4049. The relationship between both water sorption and solubility and filler content was negligibly low regardless of the difference of the light-curing sources. CONCLUSION: Within the limits of this study, the water sorption and solubility of flowable resins, which were light cured using a DPSS laser and QTH light, were within acceptable ISO levels. The 473-nm DPSS laser showed potential as a light source for light curing flowable resins.

Effect of hydrogen peroxide on microhardness and color change of resin nanocomposites.

PURPOSE: To examine the effect of hydrogen peroxide on the microhardness and color change of resin composites containing nanofillers. METHODS: Three resin nanocomposites with three different shades and two different tooth whitening agents were used. The specimens were given a 3-week treatment with one of three protocols: (1) 7 hours/day treatment of carbamide peroxide (CP) + 17 hours/day immersion in distilled water (DW); (2) 1 hour/week treatment of hydrogen peroxide (HP) + immersion in DW for the rest of the week; and (3) immersion in DW for 24 hours/day. The microhardness and color changes were measured after treatment. RESULTS: After treatment with the whitening agents, there was an 8.1-10.7% decrease in the original microhardness. These values were similar to those obtained from the samples treated with distilled water. In the same resin product, the decrease was similar regardless of the test agents used. In most cases, the color change was only slight (deltaE*=0.5-1.4). Hydrogen peroxide enhanced the color change but the absolute color change values were similar in the same product and shade, regardless of the test agent used.