Minimum Radiant Exposure and Irradiance for Triggering Adequate Polymerization of a Photo-Polymerized Resin Cement

Abstract

This study aimed to establish the minimum radiant exposure and irradiance to trigger an adequate polymerization of a photo-polymerized resin cement. In total, 220 disc-shaped specimens (diameter of 10 mm and thickness of 0.1 mm) were fabricated using a photo-polymerized resin cement (Variolink N-transparent, Ivoclar Vivadent). To investigate the minimum radiant exposure, the specimens were polymerized with radiant exposures of 1, 2, 3, 4, 5, 6, and 18 J/cm2 (n = 20). During polymerization, the irradiance was maintained at 200 mW/cm2. To investigate the minimum irradiance, the specimens were polymerized with irradiances of 50, 100, 150, and 200 mW/cm2 (n = 20). During polymerization, the radiant exposure was maintained at the previously determined minimum radiant exposure. The Vickers microhardness (HV) and degree of conversion (DC) of the carbon double bond of the specimens were measured to determine the degree of polymerization of the specimens. The results were analyzed using one-way analysis of variance (ANOVA) and Tukey’s test (p < 0.05). In the investigation of the minimum radiant exposure, the HV and DC of the specimens polymerized with a radiant exposure from 1 to 5 J/cm2 were significantly lower than those with 18 J/cm2 (all p < 0.05). However, no significant difference in HV and DC was found between the specimens polymerized with 6 J/cm2 and 18 J/cm2 (p > 0.05). In the investigation of the minimum irradiance, the specimens polymerized with an irradiance of 50 mW/cm2 had significantly lower HV and DC than the specimens polymerized with an irradiance of 200 mW/cm2 (p < 0.05). However, no significant difference in the HV and DC was found among the specimens cured with irradiances of 100, 150, and 200 mW/cm2 (p > 0.05). In conclusion, the minimum radiant exposure and irradiance to trigger an adequate polymerization of the light-cured resin cement were 6 J/cm2 and 100 mW/cm2, respectively.

Effect of Optical Properties of Lithium Disilicate Glass Ceramics and Light-Curing Protocols on the Curing Performance of Resin Cement

“…For this experiment, we designed four light-curing protocols, ranked according to the total energy (total energy = irradiance × exposure time): LCP1 > LCP2 > LCP3 > LCP4. The DC and microhardness of resin cement under these four light-curing protocols also conformed to this law; the curing performance was positively correlated with irradiance and exposure time, which is similar to previous research [24,39]. Although the curing performance generally showed this pattern, in some groups, the comparison between groups showed that the difference was not significant.…”

“…Studies show that the material types, thickness, transparency and shade of the ceramic materials can have an effect on the curing light reaching the resin cement [20][21][22]. Higher light intensities or longer exposure times improve the curing performance of resin cements [23,24]. However, most of these experiments are studies on the degree of polymerization of resin cement on a single factor.…”

Light Transmission of Various Aesthetic Posts at Different Depths and Its Effect on Push-Out Bond Strength, Microhardness of Luting Cement

“…The intensity of the light-curing unit according to the ISO standards is 300 mW/cm 2 with wavelengths of 400-515 nm [21]. However, researchers have reported that the minimum radiant exposure and irradiance to trigger an adequate polymerization of the light-cured resin cement were 6 J/cm 2 and 100 mW/cm 2 , respectively [22]. The light intensity at 200 mW/cm 2 resulted in adequate curing and degree of conversion of luting cement.…”