Purpose: The objective of this study was to verify growth suppression of methicillin-resistant Staphylococcus aureus (MRSA) involved in ventilator-associated pneumonia (VAP) aggravation by the probiotic candidate bacterium Lactobacillus gasseri (L. gasseri) in the oral cavity.
Materials and Methods: L. gasseri YIT 12321 (Lg YIT 12321) and MRSA JCM 8702 (MRSA-JCM) were used as test bacteria. Both Lg YIT 12321 and MRSA-JCM were cultured in lactobacilli MRS medium, and MRSA-JCM was also cultured in TS medium anaerobically at 37˚C for 18-24 hours. The antibacterial activity of Lg YIT 12321 against MRSA-JCM was examined by competition assay and radial diffusion assay (RDA). A fraction obtained from the Lg YIT 12321 culture supernatant by 50% (w/v) saturated ammonium sulfate (50% sat. ammonium) precipitation was examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE).
Results: In the competition assay, inhibition of MRSA-JCM proliferation by Lg YIT 12321 was observed. Moreover, it was confirmed that the growth of MRSA-JCM was inhibited by neutralized culture supernatant of Lg YIT 12321 in the RDA, suggesting that the growth of MRSA-JCM was suppressed by an antibacterial substance produced by Lg YIT 12321.
Conclusion: Lg YIT 12321 is a candidate probiotic that produces a class II bacteriocin that suppresses the growth of MRSA-JCM.
Purpose: This study evaluated the discoloration of current flowable and universal resin composites by immersing in black tea over 30 days.
Materials and Methods: Three flowable resin composites and three universal resin composites were evaluated. The composites were inserted into a disk-shaped stainless steel mold and properly cured. The surfaces of the composite disks were wet-ground and ultrasonically cleaned. Colors – L*, a*, and b* were measured at the center of disks on a gray background using a spectrophotometer. The disks were immersed in black tea at 37˚C for 30 days, and the colors were repeatedly measured at 1, 3, 5, and 30 days of immersion. Color differences ΔE*ab were calculated from the L*, a*, and b* values. Water sorption and solubility of the composites were also measured as per ISO 4049. The results were statistically analyzed, and regression analyses were done between ΔE*ab and ΔL*, Δa*, Δb* or sorption/solubility.
Results: All the composites showed observable increases of ΔE*ab within the first 5 days of immersion. Values of ΔE*ab ranged from 0.64 to 4.97, and three composites exhibited values above the clinically acceptable value, 3.3. ΔL* and Δb* revealed strong correlations with ΔE*ab. Both water sorption and solubility had positive correlations with ΔE*ab at 30 days.
Conclusion: Tea immersion induced discoloration of the current resin composites. This discoloration was affected most by the change in brightness and difference in its blue-yellow chromaticity, and the level of discoloration was material dependent.
Purpose: This study aimed to evaluate the effects of surface treatments on the shear bond strengths of composite resin blocks for CAD/CAM and luting agents.
Materials and Methods: All specimens were air-abraded with alumina particles before shear bond strength testing and categorized into the following pretreatment groups: C, no treatment; S, conventional silane treatment; GP, universal silane treatment; RS, universal silane treatment after silica coating; CM, resin coating after universal silane treatment; and RM, universal silane treatment after silica coating and resin coating. The surface roughness test was conducted to determine the fitting accuracy.
Results: The CM and RM groups demonstrated significantly higher bonding durability compared to the other groups. The film thickness of the resin coating was 12.66 µm, indicating its effectiveness in improving the bond strength without compromising the fitting accuracy.
Conclusion: Thus the clinical application of the resin-coating technique may prove useful for preventing the debonding of CAD/CAM fabricated crowns.