Effect of stepped exposure on quantitative in vitro marginal microleakage

Alex José Souza Santos, Milena Tais Lisso, Flávio Henrique Baggio Aguiar, Fabiana Mantovani Gomes França, José Roberto Lovadino
Journal of Esthetic and Restorative Dentistry 2005, 17 (4): 236-42; discussion 243

PURPOSE: The aim of this in vitro study was to evaluate the effect of a soft-start curing mode on microleakage

MATERIALS AND METHODS: Standardized Class V cavities were prepared within all the margins in the buccal enamel or dentin surface of sound, freshly extracted inferior bovine incisors. Forty preparations were filled with a restorative system (Single Bond and Filtek Z250, 3M ESPE, St. Paul, MN, USA). Ten restorations of each group were made on both types of substrates and polymerized with a conventional curing technique (600 mW/cm2/40 s) or with a soft-start technique (150 mW/cm2/10 s + 600 mW/cm2/30 s). All specimens were thermocycled 3000 times and then immersed in methylene blue 2% for 12 hours. The specimen microleakage was quantitatively determined in a spectrophotometer.

RESULTS: The soft-start technique resulted in statistically significant less microleakage for each substrate (p < .05). The conventional groups exhibited 6.1 (dentin) to 15.4% (enamel) more leakage compared with the soft-start groups. When compared with the enamel margins, the dentin margins demonstrated greater microleakage: from 15.5% greater with the conventional light-curing mode to 25.6% greater with the soft-start light-curing mode.

CONCLUSIONS: The polymerization technique using a very low initial intensity (150 mW/cm2/10 s) decreased the microleakage of composite resin restorations.

CLINICAL SIGNIFICANCE: A soft-start light-curing approach to resin composite polymerization resulted in less microleakage at enamel and dentin margins in Class V cavities compared with resin composite restorations polymerized using a conventional light-curing approach.

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