Evaluation of Light Curing Distance and Mylar Strips Color on Surface Hardness of Two Different Dental Composite Resins

Abstract

Introduction: Hardness is one of the basic properties of dental materials, specially composite resins which is relevant to their polymerization. The aim of this study was to evaluate the effect of light curing distance and the color of clear Mylar strips on surface hardness of Silorane-based (SCR) and Methacrylate-based composite resins (MCR).Materials and methods: 40 samples of MCRs (Filtek Z250) and SCRs (Filtek P90) were prepared in size of 5 mm×2 mm (80 samples in total). The samples divided into 8 groups (10 samples in each one) based on the color of clear Mylar strips (white or blue) and distance from light curing source (0 mm or 2 mm). All the samples cured for 40 second and stored in incubator for 24 hours in 37°C temperature. Surface hardness test was done by Vickers test machine and the collected data were analyzed by one-way ANOVA and paired T-test by using SPSS software version 13 at significant level of 0.05.Results: MCRs cured with blue Mylar strips from 0 mm distance had the highest (114.5 kg/mm2) and SCRs cured with white Mylar strips from 2 mm distance had the lowest (42.2 kg/mm2) mean of surface hardness. Also, the results of comparison among SCRs and MCRs showed significant differences among all groups (all P values <0.01).Conclusion: The hardness decreased as the distance increased and the blue Mylar strips provided higher hardness than clear ones. Also, Filtek Z250 showed higher hardness compared to Filtek P90.

Resin based restorative dental materials: characteristics and future perspectives

“…Greater Microhardness at the bottom surface. Filtek Ultimate (3 m) showed highest microhardness values.Palin et al [49]201450/50mass% of Bis-GMA and TEGDMAcuring protocol was varied (400mWcm −2 for 45 s, 1500mWcm −2 for 12 s and 3000mWcm −2 for 6 sDC, Polymerization rate, Flexural strength, Polymerization stress, Cuspal deflection, microleakagePhosphine oxide initiator provided superior mechanical and physical properties for high irradiance curing protocols compared with materials based on camphoroquinoneSeyed Mostafa Mousavinasab et al [50]2014Filtek Z250, Filtek P90distance from light curing source (0 mm or 2 mm)HardnessHardness decreased as the distance increased and Filtek Z250 showed higher hardness compared to Filtek P90.…”

Influence of different power densities during polymerization on the color of composite resins

“…The International Commission of L'Eclairage developed the system to measure colors based on human perception (CIE L*, a*, b*). The variable L* corresponds to the black-white luminosity coordinate, a* indicates the color coordinate along the red-green axis, and b* indicates the color coordinate along the yellowblue axis [19,20]. A positive ΔL value means that the object tends to white (brighter) and negative Δb and Δa values mean that the tooth tends to be less yellow and less red, respectively [21].…”

“…The color stability of composite resins depends on the degree of conversion of monomers into polymers throughout a sufficient polymerization [8,16,17] and it is affected by the system and the technical condition of polymerization [18]. The delivered radiant exposure and the power density of the photopolymerizer should agree with the energy requirement of the resin so there is a complete conversion of monomers into polymers [19,20]. The higher the power density, the higher the number of photons and the greater is the depth and effectiveness of polymerization [21].…”

Restauração Classe II com resina composta: avaliação da técnica de Pollack.

“…Considerando-se que junto à face cervical da caixa proximal de restaurações classe II a intensidade de luz que atinge os incrementos da resina deva ser consideravelmente menor do que a intensidade próxima à superfície, o grau de conversão dos monômeros em polímeros também sofre um decréscimo 13 .…”