Giulliana Panfiglio Soares

Effect of preheating resin composite and light-curing units on the microleakage of Class II restorations submitted to thermocycling.

This in vitro study evaluated microleakage in Class II cavities restored with dental composite and varying light-curing units and the temperature of the composite when subjected to a thermocycling test. Ninety cavities were prepared on the proximal surfaces of bovine teeth and randomly divided according to the light-curing mode (QTH-420 mW/cm2, LED 2nd generation-1100 mW/cm2, or LED 3rd generation-700 mW/cm2) and temperature of the resin composite (23°C, 54°C and 60°C). Following the restorative procedures and thermocycling, the samples were immersed in methylene blue for 12 hours. The samples were ground and the powder prepared for analysis in an absorbance spectrophotometer. All the results were statistically analyzed using the nonparametric tests of Kruskal-Wallis and Dunn (p ≤ 0.05). The results showed that there was no statistical difference between the light-curing modes at a temperature of 23°C. For 54°C, QTH showed a microleakage mean that was significantly lower than those of the LED groups, and for 60°C, QTH had a microleakage mean significantly lower than that of the LED 2nd generation group. There was no statistical difference between the temperatures of the resin composite when LEDs were used. For QTH, 54°C showed statistically lower microleakage than 23°C. The group preheated to 60°C showed no difference when compared to the group heated to 23°C. Preheating the resin composite (54°C and 60°C) did not improve the microleakage means when high-irradiance LED was used; however, it decreased the microleakage means when a QTH with low irradiance was used.

Effect of surface sealants on microleakage of Class II restorations after thermocycling and long-term water storage.

PURPOSE To evaluate interface degradation leading to marginal microleakeage in Class II restorations that had received an application of surface sealant at the tooth/restoration interface or not. MATERIALS AND METHODS Eighty bovine incisors were used, and the teeth were split obliquely, 10 mm from the amelodentinal proximal junction, and finished with water abrasive papers to obtain a smooth, flat incisal surface. Cavities were made to simulate Class II preparations (8 mm high, 4 mm wide and 1.5 mm deep), and the restorations were performed with a composite resin. Teeth were then randomly allocated into 8 groups according to the surface sealant (none, Fortify, Single Bond 2, or Scothbond MP Plus) and aging process (none or thermocycling and storage for 6 months). Microleakage was then evaluated using a dye penetration method immediately after the restoration or after aging. The samples were triturated and assessed by spectrophotometer. RESULTS Microleakage was statistically similar in all groups when assessed immediately after the restorative procedure. After aging, teeth sealed with Fortify presented better results than the other groups. CONCLUSION Aging causes interface degradation and increased microleakage. Surface sealant can reduce these effects and decrease microleakage in Class II restorations.

Effect of light curing protocol on degree of conversion of composites

Abstract Objective. To evaluate the degree of conversion (DC) of two light-cured composites with different protocols of light curing. Materials and methods. One hundred and ninety two specimens (n = 8) were prepared (5 mm × 2 mm) according to experimental groups: two composite resins (Filtek Supreme and four seasons); three light curing protocols [20 s with the tip of the light curing unit (LCU) device touching composite surface (C); 20 s with the tip of the LCU at 8 mm distant from composite surface (D); and tip of the LCU at 8 mm distant from composite surface and polymerization time required to obtain a radiant exposure of 16 J/cm2 (DS)]. Four LCUs (Bluephase 16i, Ultralume LED 5, XL 3000 and Optilux 501C) were used. DC of the bottom and top surface of specimens were measured using a FTIR spectrometer. Data were statistically analyzed by 3-way split splot ANOVA and Tukey’s test (alpha = 0.05). Results. The results showed that DC of the top surface was higher than the bottom at all experimental conditions (p < 0.0001). Overall, the curing at 8 mm of distance did not affect conversion rate on the top surface (p > 0.05), but bottom surfaces showed DC reduction (p < 0.05). The highest monomer conversion values were observed for C and DS situations. Conclusion. The distance between the LCU and material surface and radiant exposure can affect the DC. Polymerization at distance should be performed with curing units with higher light power and/or extended exposure time.

Effect of different monomer-based composites and acid etching pre-treatment of enamel on the microleakage using self-etch adhesives systems

Abstract Objective. To evaluate quantitatively the marginal microleakage of restorations carried out with self-etching adhesives with or without prior phosphoric enamel acid etching of silorane or methacrylate resin-based composite restorations subjected to thermal cycling. Materials and methods. Forty cavities were prepared at the proximal surface of bovine incisors and randomly divided according to the etching of the enamel and restorative system used. The groups were restored with methacrylate [Adper SE Plus adhesive (3M ESPE) + Filtek Z250 (3M ESPE)] or silorane [Filtek LS adhesive (3M ESPE) + Filtek LS composite (3M ESPE)] restorative systems, light-cured using a LED unit (Bluephase 16i, Vivadent). After restorative procedure and thermocycling (1000 cycles), the specimens were immersed in methylene blue for 2 h. The specimens were triturated and the powder was used for analysis in an absorbance spectrophotometer. Data were statistically analyzed by 2-way ANOVA (alpha = 0.05). Results. No statistical difference between the restorative materials tested with or without previous acid etching of enamel in Class II marginal microleakage was observed (p > 0.05). Conclusions. The use of acid etching prior to self-etching adhesives did not interfere on the microleakage of methacrylate- or silorane-based restorations.

Curing Quality of Composites as Influenced by the Filler Content, Light Source and Curing Time

The quality of composite polymerization has been of great concern for researchers. Curing of nanocomposites under long distance (8 mm) and extended light exposure through conventional (halogen and LED) and argon laser lamps is unclear in the literature. This study evaluated the influence of curing modes and filler particle size on hardness and degree of conversion of dental composites photo activated at an 8 mm distance. Light sources (LED 1100 mW/cm2-Bluephase; LED 700 mWcm2-Ultra-lume; halogen lamp 450 mW/cm2-XL3000; and argon-laser 500 mW/cm2-AccuCure), curing times (20 and 60 s), microhybrid (Filtek-Z250) and nanofilled (Filtek-Supreme) resins were investigated. Eighty samples (n=5) were made using Teflon molds. Hardness and degree of conversion were obtained for bottom/top surfaces of 2-mm increments. Data were submitted to ANOVA and Tukey tests (?=5%).Top surfaces showed similar hardness. A 60s exposure time increased bottom hardness and Filtek-Z250 showed higher hardness for curing units except Bluephase. Regarding degree of conversion, bottom/top surfaces showed similar means at 60s; at 20s, bottom/top surfaces revealed similar means only for Filtek-Z250 cured by Bluephase and Ultra-lume. High irradiance and extended exposure time can improve hardness and conversion on bottom surface. Microhybrid resin presented better conversion of monomers than the nanofilled composite under higher irradiance and extended exposure times.

Effect of polymerization mode and time of adhesive system on microleakage in composite resin restorations.

AIM To quantify the microleakage on restorations carried out with a two-step etch-and-rise adhesive system and nanofilled composite resin after thermal and mechanical loading cycling. METHODS Ninety cavities were prepared on proximal surfaces of incisive teeth, and were randomly divided according to the photoactivation time (10, 20, or 30 s) and light-curing mode (Quartz Tungsten Halogen (QTH) lamps, 450 mW/cm(2); Light Emitting Diode (LED) second generation, 1100 mW/cm(2); or LED third generation, 700 mW/cm(2)) of an adhesive system (n = 10). Following restorative procedures and thermal and mechanical loading cycling, the samples were immersed in Methylene Blue for 2 h. The samples were ground, and the powder was prepared for analysis in an absorbance spectrophotometer. All results were statistically analyzed by anova and Tukeys test at the 5% level of significance. RESULTS There were no significant statistical difference in microleakage between the light-curing mode (P = 0.1212) and light-curing time (P = 0.2043). CONCLUSION Different curing modes and increasing the curing time were not factors that influenced the process of microleakage.