Microleakage evaluation between higher viscosity and flowable bulk composite resins

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As filler loading increased, viscosity increased and as Bis-GMA ratio increased, viscosity increased. However, as temperature increased, viscosity decreased. Keywords: Resin composite; Rheology; Handling behaviour http://dx.doi.org/10.1016/j.dental.2014.08.094 94 Polymerization shrinkage of recent low-shrinkage and bulk-fill resin composites T. Maseki ∗ , M. Maeno, S. Ogawa, Y. Nara Department of Adhesive Dentistry, School of Life Dentistry at Tokyo, The Nippon Dental University, Tokyo, Japan Purpose: The purpose of this study was to examine the polymerization shrinkage of low-shrinkage resin composites and bulk-fill resin composites under different light-curing methods. Methods and materials: Two low-shrinkage resin composites; Kalore (KAL, GC), Filtek LS (FLS, 3M ESPE) and two bulk-fill resin composites; SDR (SDR, Dentsply), Tetric NCeram Bulk Fill (TET, ivoclar vivadent) and a popular flowable composite; Filtek Supreme Ultra Flowable (FSU, 3M ESPE, as control) were used. Each material was filled into a translucent acrylic mold (f 4 mm × 8 mm) and then cured by three different light-curing methods, HL: curing with a halogen light source (Optilux 501, Kerr, 750 mW/cm2 × 20 s), HP: curing with high power mode (1800 mW/cm2 × 3 s) or SS: soft-start mode (1000 mW/cm2 × 2 s + 1800 mW/cm2 × 3 s) using a LED light source (G-Light Prima2, GC). Polymerization shrinkage was measured using a diode laser displacement sensor (HLC105B-BK, SUNX) during 0–180 s (n = 5). The data were analyzed using two-way ANOVA and Tukey’s q-test. Results: The mean values of polymerization shrinkage (S.D.) in % under HL/HP/SS conditions were KAL: 1.09(0.27)/ 1.18(0.27)/0.99(0.26), FLS: 0.58(0.15)/0.64(0.15)/0.58(0.18), SDR: 1.12(0.30)/1.32(0.27)/1.27(0.19), TET: 1.35(0.33)/1.77(0.34)/ 1.39(0.14) and FSU: 2.26(0.34)/2.71(0.33)/2.17(0.29). Both differences in resin composite and light-curing method influenced shrinkage rate significantly at p < 0.01 and there was no interaction effect between those two factors. The polymerization shrinkage of FLS was significantly smaller than those of the other composites at p < 0.01. The value of KAL was statistically smaller than those of FSU and TET at p < 0.01. The rate of HP light-curing was significantly greater than the values of HL and SS methods at p < 0.01. Conclusion: The polymerization shrinkage of lowshrinkage composites was similar to or smaller than the values of bulk-fill resin composites and a popular flowable composite in this study. Light-curing method with strong light intensity (1800 mW/cm2 ) and short irradiation time (3 s) increased the value of shrinkage significantly compared to the other method. Keywords: Polymerization shrinkage; Bulk-fill resin composites http://dx.doi.org/10.1016/j.dental.2014.08.095

95 Microleakage evaluation between higher viscosity and flowable bulk composite resins K. Tolidis ∗ , C. Boutsiouki, P. Gerasimou, E. Panagiotidou Operative Dentistry Department, Aristotle University of Thessaloniki, Greece Purpose: Bulk fill materials were introduced as a means of saving clinical time by placement of the composite in a single layer. Bulk fill composite resins are divided into two categories: higher viscosity and flowables composites. The aim of the present study was to evaluate bulk fill composite resins in terms of microleakage. Methods and materials: Class I cavities (3 mm × 3 mm × 3 mm) were prepared with diamond bur in 90 posterior permanent teeth. Teeth were randomly divided into 9 groups (n = 10) and were immediately restored using bulk fill composite resins. Conventional composite resin was used as a control (Group 1). Matching self-etch bonding system was used, with separate enamel etching. Group 1: Filtek Z250 + AdperTM Single Bond Plus Adhesive, Group 2: Venus Bulk Fill + iBOND Self Etch, Group 3: Tetric EvoCeram Bulk Fill + Adhese One, VivaPen, Group 4: Tetric EvoCeram Bulk Fill + Adhese One, VivaPen + Compothixo, Group 5: SonicFill OptiBondTM All-In-One, Group 6: Filtek Bulk + Scotchbond Universal Adhesive, Group 7: EverXPosterior + G-Bond, Unit Dose + thin layer of G-aenial Anterior, Group 8: Beautifil Bulk-Fill + BeautiBond, Group 9: Beautifil Bulk Fill Flowable + BeautiBond. Bulk fill composite resins were polymerized for 40 with a LED curing unit. Specimens were thermocycled (1500 cycles, 5–36–55–36◦ C), immersed in 5% methylene blue for 24 h and cut longitudinally in a microtome. Photographs were taken for each cut, under a microscope. Microleakage was classified according to the number of surfaces and the depth at which dye penetration was observed. Six measurements were made per specimen and mean scores were calculated. Results: Mean values and standard deviations were calculated. Groups in ascending microleakage were: 8 < 6 = 7 < 3 = 4 < 2 < 1 < 9 < 5. Group 2 exhibited statistical difference with the control and Groups 5, 8 and 9 (p < 0.001). Group 5 exhibited statistical difference with all the other groups (p < 0.001) except for the control and Group 9. Groups 3 and 4 exhibited identical behavior. Group 3, 4, 6, 7 and 8 resulted in statistical difference in comparisons with control and Groups 5 and 9 (p < 0.001). Additionally Group 8 exhibited little statistical difference in comparison with Group 2 (p = 0.01). Conclusion: Conventional resin did not exhibit better behavior in comparison to bulk materials tested. Lower microleakage scores were demonstrated by higher viscosity bulk composites. http://dx.doi.org/10.1016/j.dental.2014.08.096