Effects Of Two Bleaching Agents On The Microleakage Of Tooth-colored Restorative Materials

Objective:The purpose of this study was to evaluate effects of a bleaching gel (10% carbamide peroxide) and a whitening strip(14% hydrogen peroxide) on the microleakage of three different tooth-colored restorative materials and to choose proper bleaching methods and matching restorative materials for the clinic.Method:Forty-five freshly extracted human premolar teeth were used. Standardized kidney-shaped Class V cavity preparations were placed in the buccal and lingual surfaces at the cementoenamel junction(3×3×2mm). Teeth were randomly assigned to A, B and C groups of 15 teeth each and restored as follows:a glass-ionomer cement (KetacTM Molar Easymix), a compomer (F2000), a compomer (Dyract AP). Teeth were restored in distilled water at 37℃for 7 days. The specimens were then thermocycled (500×,5-55℃). Each group was randomly divided into 3 subgroups of 5 teeth each. The 3 subgroups were treated for 21 days with one of the following:whitening strip (14% hydrogen peroxide), bleaching gel (10% carbamide peroxide), or distilled water (control). After bleaching, teeth were coated with light-cured resin in apical foramens and nail varnish except for 1 mm around the restoration margin, and placed in a solution of 0.5% basic fuchsin dye for 24 hours, then teeth were sectioned longitudinally with a diamond cutter to evaluate the dye penetration. The depth of staining along the tooth restoration interface was recorded with a stereomicroscope at×16 magnification. Data were analyzed with ANOVA, LSD-t and SNK-q (α=.05)Results:1. There were no significant differences between the 3 restorative materials in control group for the occlusal margins (P>0.05), except that the microleakage of KetacTM Molar Easymix for the gingival margins was higher than F2000 (P<0.05). There were no significant differences between occlusal margins and gingival margins for all materials in all groups (P>0.05), except that the microleakage of gingival margins was higher than occlusal margins for KetacTM Molar Easymix in experimental groups (P<0.05).2. The microleakage of KetacTM Molar Easymix in the experimental groups was higher than the control group (P<0.05), but there were no significant differences between experimental groups for KetacTM Molar Easymix(P>0.05).3. The two bleaching agents did not significantly affect the microleakage of F2000 or Dyract AP (P>0.05).Conclusion:1. There were no significant differences between enamel and dentin for all materials in all groups, except that the microleakage of dentin was higher than enamel for KetacTM Molar Easymix after bleaching.2. There were no signicant differences in microleakage of restorations between bleaching gel (10% carbamide peroxide) and whitening strips (14% hydrogen peroxide). Whitening strips (14% hydrogen peroxide) showed good prospects for application.3. The bleaching products used in this study did not adversely affect the microleakage of compomer, but adversely affect glass ionomer, so compomer was recommended to restore wedge-shaped defects, and if the defects had been restored with glass ionomer cements, the cements should be replaced with compomer before bleaching.