Antibacterial Activity of Three Tooth-Colored Restorative Materials against Streptococcus mutans : An in Vitro Study

Background: Antibacterial activity of restorative materials had an important role in preventing caries recurrence. Aim of the study: to evaluate the antibacterial effect of three tooth-colored restorative materials. Materials and Methods: Three commercially available tooth-colored restorative materials, GC Fuji (Group I), Riva self-cure (Group II) and Versa Comp (Group III) were evaluated. The test samples of restorative materials were manipulated in accordance with manufacturer’s instructions. Eppendorf tubes were filled with constant measured amount of the three tested restorative materials; a conical cavity was created in the center of each material after curing. Bacterial suspension was prepared from fresh overnight growth of Streptococcus mutans on blood agar. 50 μL of bacterial suspension was placed in the conical cavity and around the restorative material inside each eppendorf tube and then were incubated. At the end of incubation period, eppendorf tubes were removed from candle jar and viable bacterial count was estimated. Results: It has been found that at day1, day 2 as well as day 3, there was decrease in bacterial count but, there was no statistically significant difference between the three groups. On studying each group separately, group I there was a statistically significant decrease in bacterial count at day 2 and group II and III showed statistically significant decrease from day 2 to day 3. Conclusions: Fuji LC was more effective against Streptococcus mutans, than Riva self-cure and Versa comp, but with no significant difference. (3008) Norhan A. El Dokky, et al. E.D. J. Vol. 64, No. 4 the number of their visits to dental office. [2, 3] Both restorative materials and oral bacteria are believed to be responsible for restoration failure. [3] In an attempt to obtain restorative materials that could prevent marginal gaps colonization, materials capable of releasing fluoride and providing antimicrobial activity have been developed, such as; Glass Ionomer cements (GIC),”compomers” and fluoridated composite resins. [4, 5] Tooth-colored restorative materials are increasingly demanded by patients and applied by clinicians. In spite of routine use of posterior tooth-colored restorative materials, poor marginal adaptation of composite resins, mostly due to the polymerization shrinkage, is still considered a major reason for the failure of these restorations. [6-8] Microleakage and recurrent caries are major clinical problem associated with direct posterior composite restorations. Bacterial penetration into the prepared cavity can lead to secondary caries, which is the main reason for failures in dental restorations. [9] Due to this potentiality of leakage, any restorative /base/liner material used in the mouth should have antibacterial properties in defense against bacterial migration. [10] Effective and long lasting antibacterial property of composite resin-restorative material may eliminate bacterial biofilm formation at the interface and thus increase restoration longevity. [11] Several species of bacteria has been isolated from dental plaque, such as Lactobacilli, Streptococcus mutans, Streptococcus sorbinus etc, [12] which may induce the formation of caries. Streptococcus mutans is one of the most frequent bacteria involved in dental caries. [13] The aim of the present study was to evaluate the antibacterial effect of three tooth colored restorative materials. MATERIALS AND METHODS TABLE (1): Materials used in this study: Materials Manufacturer GC Fuji LC capsule VLC GC corporation, Tokyo, Japan Riva self-cure Glass Ionomer capsule SDI Limitation, Australia Versa Comp universal hybrid composite Sultan Three commercially available tooth-colored restorative materials were used in this study; the details of these materials were shown in table (1). GC Fuji (Group I), Riva self-cure (Group II) and Versa Comp (Group III). The micro-organisms used in this study were four strains of Streptococcus mutans. Bacterial plaque was collected from different parts of the patient’s mouth immediately cultured on Mitis Salivarius agar kept in an incubator at 37oC for 24 hours; afterwards isolated and identified. Identification was accomplished by colony morphology, gram stained films, catalase test, subculture on blood agar and bile esculin agar. Pure isolates were preserved till time of experiment. The test samples of restorative materials were manipulated in accordance with manufacturer’s instructions. The samples were prepared in strip crown form (Uniteck 3M Dental products division) for standardization as prefabricated mould. [10] Clean Eppendorf tubes were filled with constant measured amount of the three tested restorative materials; a conical cavity was created in the center of each material after curing by fissure stone bur number 5. The specimens were autoclaved afterwards at 121oC for 30 minutes. Bacterial suspension equivalent to 0.5 McFarland was prepared from fresh overnight growth of Streptococcus mutans on blood agar. [14] 50 μL of bacterial suspension was placed in the conical cavity and around the restorative material inside each eppendorf tube. They were then incubated in candle jar for 24, 48 and 72 hours. At the end of incubaANTIBACTERIAL ACTIVITY OF THREE TOOTH-COLORED RESTORATIVE MATERIALS (3009) tion period, eppendorf tubes were removed from candle jar and viable bacterial count was estimated. Ten folds serial dilutions were done for each eppendorf tube (up to 1/10000) and counting was done on Mitis Slivarius agar. The number of colony forming unit (CFU) was calculated by this formula: 50 x No. of colonies x Inverse of dilution. Statistical analysis: All data were collected and statistically analyzed. A logarithmic transformation (Log10 transformation) of each CFU count was performed because of the high range of bacterial counts. Data were explored for normality after Log10 transformation using Kolmogorov-Smirnov and Shapiro-Wilk tests. Data showed non-parametric (non-normal) distribution. So, data were presented as median and range values. Kruskal-Wallis test was used to compare between the three groups. Friedman’s test was used to study the changes by time in each group. Wilcoxon signed-rank test was used for pair-wise comparisons when Friedman’s test is significant. The significance level was set at P ≤ 0.05. Statistical analysis was performed with IBM® SPSS® Statistics Version 20 for Windows. RESULTS: It has been found that at day1, day 2 as well as day 3, as regards median and range there was decrease in bacterial count but, there was no statistically significant difference between the three groups as shown in table (2) & figure (1). TABLE (2): Median, range values and results of comparison between Log10 CFU in the three groups Group I Group II Group III P-value Day 1 5.2 (5.0 – 6.1) 5.4 (0.0 – 7.6) 6.5 (5.9 – 6.9) 0.388 Day 2 0.0 (0.0 – 4.7) 2.0 (0.0 – 6.0) 4.7 (0.0 – 6.9) 0.396 Day 3 0.0 (0.0 – 0.0) 0.0 (0.0 – 0.0) 0.0 (0.0 – 3.2) 0.368 *: Significant at P ≤ 0.05 On studying each group separately, in group I there was a statistically significant decrease in bacterial count at day 2 and day 2 and 3 didn’t show any bacterial growth, while in group II and III, there was no statistically significant decrease in bacterial count at day 2, but from day 2 to day 3 there was a statistically significant decrease in bacterial count as shown in table (3). TABLE (3): Median, range values and results of comparison between Log10 CFU in each group at different time periods Group I Group II Group III Day 1 5.2 (5.0 – 6.1) a 5.4 (0.0 – 7.6) a 6.5 (5.9 – 6.9) a Day 2 0.0 (0.0 – 4.7) b 2.0 (0.0 – 6.0) a 4.7 (0.0 – 6.9) a Day 3 0.0 (0.0 – 0.0) b 0.0 (0.0 – 0.0) b 0.0 (0.0 – 3.2) b P-value 0.023* 0.045* 0.037* *: Significant at P ≤ 0.05, Different superscripts in the same column are statistically significantly different As regards the % reduction in bacterial count in the three groups results showed no statistically significant difference as shown in table (4). Fig. (1): Line chart representing median Log10 CFU in the three groups. (3010) Norhan A. El Dokky, et al. E.D. J. Vol. 64, No. 4