BackgroundSecondary caries is responsible for 60 percent of all replacement restorations in the typical dental practice. The diversity of the bacterial sources and the different types of filling materials could play a role in secondary caries. The aim of this study was to determine and compare the microbial spectrum of secondary caries biofilms around amalgam and composite resin restorations.MethodsClinical samples were collected from freshly extracted teeth diagnosed with clinical secondary caries. Samples were categorized into four groups according to the types of restoration materials and the classification of the cavity. Biofilms were harvested from the tooth-restoration interface using a dental explorer and after dilution were incubated on special agars. The bacteria were identified using the biochemical appraisal system. Statistical calculations were carried out using SPSS11.5 software to analyze the prevalence of the bacteria involved in secondary caries.ResultsSamples from a total of four groups were collected: two groups were collected from amalgam restorations, each had 21 samples from both Class I and Class II caries; and the other two groups were from composite resin restorations, each had 13 samples from both class I and class II caries. Our results showed: (1) Anaerobic species were dominant in both restoration materials. (2) In terms of the types of individual bacteria, no significant differences were found among the four groups according to the geometric mean of the detected bacteria (P > 0.05). However, there were significant differences among the detected bacteria within each group (P < 0.05). The composition of each bacterium had no statistical difference among the four groups (P > 0.05), but showed significant differences among the detected bacteria in each group (P < 0.05). (3) Among the four groups, there were no significant differences for the detection rate of each bacterium (P > 0.05), however, the detection rate of each bacterium within each group was statistically different among the detected bacteria (P < 0.05).ConclusionsThe proportion of obligatory anaerobic species was much greater than the facultative anaerobic species in the biofilm of secondary caries. Statistically, the materials of restoration and the location of secondary caries did not show any significant effects on the composition of the microflora.
Objective:To compare the effects of three antioxidants (sodium ascorbate, sodium ascorbate combined with a surfactant, and catalase) on the microleakage of composite resin restorations after external tooth bleaching with 10% carbamide peroxide.Materials and Methods:Buccal cavities were prepared on the surface of 60 intact premolars, which were randomly divided into six groups. All cavities were filled with composite resin. In group 1, teeth were not bleached; in group 2, cavities were filled immediately after bleaching; in group 3, cavities were delay-filled for 3 weeks; in group 4, cavities were treated with sodium ascorbate after bleaching and then filled; in group 5, cavities were treated with sodium ascorbate combined with surfactant after bleaching and then filled; and in group 6, cavities were treated with catalase after bleaching and then filled. Microleakage of the restorations was measured from sections using a stereomicroscope.Results:Group 1 displayed the least amount of microleakage, while group 2 showed the greatest amount of microleakage (P < 0.05). Groups 3 and 4 were similar to group 2 (P > 0.05). However, groups 5 and 6 showed a significantly lower amount of microleakage compared to group 2 (P < 0.05).Conclusion:Microleakage increased significantly after external bleaching with 10% carbamide peroxide, and decreased when the bleached teeth were treated with sodium ascorbate combined with Tween® 80, or with catalase. Catalase was more effective in decreasing microleakage, while delayed filling or treatment with sodium ascorbate alone did not effectively decrease the microleakage.
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