The impact of silver nanoparticles integration on biofilm formation and mechanical properties of glass ionomer cement.

OBJECTIVES: To study the effect of silver nanoparticles incorporation to glass ionomer cement (GIC) on the Staphylococcus aureus biofilm in terms of bacterial growth and evaluate the incorporating effect on hardness and compressive strength. METHODS: Silver nanopowder was added in concentration 0, 1, 3, and 5 wt% to the conventional powder of GIC Fuji IX GP and then the powder is added to the liquid and mixed together with the recommended Powder/liquid ratio of 3.6:1 g. One hundred and twenty disc and cylindrical-shaped specimens were prepared using teflon molds. The specimens were put in tissue culture plate wells contained S. aureus in brain-heart infusion broth. The plate was incubated at 37°C for 24 h. Specimens were then washed, fixed, dehydrated, and air dried. The spatial distribution of biofilm was examined via scanning electron microscope. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were also evaluated. After setting, the specimens were stored in distilled water for 24 h before testing for microhardness and compressive strength. RESULTS: Scanning electron photomicrographs of biofilm formed on the control GIC, showed a consistent biofilm with a thick sheet of cells, whereas those formed were less dense at 3 wt% and below the detection limit at 5 wt% silver nanoparticles. MIC and MBC of S. aureus were 25 and 50 µg/mL, respectively. The microhardness and compressive strength values of tested groups showed a nonsignificant decrease from the control group, P = .58 and .82, respectively. CONCLUSION: Incorporation of silver nanoparticles with GIC can limit S. aureus biofilm formation with an insignificant effect on mechanical properties and noticeable influence on its coloration, which restrict its usage in areas where esthetic is not of major concern. CLINICAL SIGNIFICANCE: As the modification of GIC with silver nanoparticles improved the antibiofilm properties without altering its mechanical properties, it could be used as a restoration of root carious lesion mainly in nonesthetic areas, a base under composite restorations in deep posterior cavities and as a core material in caries susceptible patients.

Apoptotic effect of different self-etch dental adhesives on odontoblasts in cell cultures.

OBJECTIVES: We aimed to evaluate the potential cytotoxicity (apoptosis-induction) of three types of self-etch dental adhesives: two-component one-step (Xeno III), two-component two-steps (Clearfil Protect Bond) and one-component one-step (Xeno V) on cultured odontoblasts. METHODS: Each adhesive was prepared to simulate its clinical manipulation. Cured sterile individual masses were immersed in DMEM and left at 37 °C for 24 h. Then a volume of 100 µL of the extract medium was added to the cultured odontoblasts and incubated for additional 24 h, 48 h and 72 h, respectively. Acridine orange-propidium iodide (AO-PI) labelling was employed to assess the proportion of dead to total number of cells. In addition, an in situ apoptosis detection kit was used to evaluate the DNA cleavage and chromatin condensation employing the immunohistochemical (IHC) technique. Statistical analysis of the data was performed using one-way ANOVA. RESULTS: Both apoptosis evaluation methods revealed comparable results with the exception that IHC showed 5-7% less number of dead cells when compared to similar groups evaluated by AO-PI. The percentages of dead to total cells after treatment with Clearfil Protect Bond, Xeno III and Xeno V, were significantly different from the percentage of dead cells after treatment with DMEM alone (-ve control), P value <0.05 and Xeno V dental adhesive had the weakest cytotoxic effect on odontoblasts followed by Xeno III especially after 24 h of incubation. Clearfil Protect Bond had the strongest cytotoxic effect on odontoblasts that was almost closer to that of Staurosporine in DMEM (+ve control). CONCLUSION: All tested dental adhesives had remarkable adverse effect on the odontoblasts in vitro; this might be of concern when applied clinically in deep cavities where such cytotoxic chemicals become in close contact to dental pulp. Therefore, further in vivo studies on animal models are recommended to support or refute these in vitro findings.

Bonding of single-component adhesives to dentin following chemomechanical caries removal.

PURPOSE: To determine the effect of chemomechanical caries removal on the bonding quality of contemporary single-component adhesives to dentin. MATERIALS AND METHODS: N-monochloro-DL-2-aminobutyrate solution (NMAB) and Carisolv gel were used to chemomechanically remove dentin caries in 60 extracted human molars. Caries removal with rotating instruments served as the control. Two single-component adhesive systems, Syntac Single Component and Excite, were applied to bond the hybrid composite Tetric Ceram to the treated dentin surfaces. The prepared samples were sectioned for microtensile bond strength testing and SEM examination of the bonding interfaces. The debonding patterns of the fractured samples were also assessed. RESULTS: No statistically significant differences were found between the bond strengths of either adhesive to the conventionally and the NMAB-treated dentin (p > 0.05). However, the Carisolv-treated dentin yielded significantly higher (p > 0.05) bond strength values with both adhesives compared to those on dentin prepared with rotating instruments. No statistical difference could be discerned between the 2 adhesive systems (p > 0.05), nor was the interaction between the 2 variables under investigation (method of caries removal and the type of adhesive) statistically significant (p = 0.7712). SEM images indicated unspecific effects of the tested variables on both the thickness of the hybrid layer and the length of the resin tags. CONCLUSION: Under the conditions of this study, using the Carisolv chemomechanical caries removal system to prepare dentin surfaces enhanced the dentin/adhesive bond strength. In addition, the chemical nature of the adhesive systems seems to have no effect on the values of bond strength.