Effect of ionizing radiation on the properties of restorative materials.

AIM: The aim of this study is to evaluate the effect of different doses of the ionizing radiation (0 Gy, 10 Gy, 30 Gy, and 60 Gy) on the physical properties of dental materials. METHODOLOGY: Disc-shaped samples from each material (Ketac Molar Easymix, Vitro Molar, Vitremer, Vitro Fil Lc, Filtek Z 250 and Filtek Z 350) were made for water solubility, sorption analysis (n = 20), microhardness (n = 20), and surface roughness analysis (n = 24). Specimens were divided into four groups, according to radiation dose: control group (0 Gy), 10 Gy, 30 Gy, and 60 Gy. For water solubility and sorption analysis, the specimens were irradiated and were stored for 21 days to calculate the water solubility and sorption values. Microhardness analysis was carried out before and after irradiation doses. For surface roughness analysis, the specimens were submitted to brushing test, and after 24 h, initial surface roughness analysis was made in a rugosimeter. Subsequently, the samples were irradiated and final surface roughness analysis was made. The original water solubility and sorption, surface roughness, and microhardness values were subjected to ANOVA two-way statistical analysis and Paired t-test and Tukey post hoc test (α = 0.05), respectively. RESULTS: Water solubility and sorption values, and surface roughness values presented statistical difference between groups (0, 10, 30 e 60 Gy) for all materials. CONCLUSIONS: High doses of ionizing radiation (30 Gy and 60 Gy) increased the surface roughness, sorption, and solubility for the most materials.

Microbial contamination in intraoral phosphor storage plates: the dilemma.

OBJECTIVES: The aims of this study were to evaluate microbial contamination in phosphor storage plates in dental radiology services and discuss the possible origin of this contamination. MATERIALS AND METHODS: The sample comprised 50 phosphor plates: 14 plates from service A, 30 from service B, and 6 in the control group, consisting of plates never used. Damp sterile swabs were rubbed on the phosphor plates, and then transferred to tests tubes containing sterile saline solution. Serial dilutions were made, and then inoculated in triplicate on Mueller Hinton agar plates and incubated at 37 °C/48 h, before counting the colony-forming units (CFU). The samples were also seeded in brain-heart infusion medium to confirm contamination by turbidity of the culture medium. All solutions, turbid and clean, were seeded in selective and non-selective media. RESULTS: At service A and B, 50 and 73.3 % of the phosphor plates were contaminated, respectively. This contamination was mainly due to bacteria of the genus Staphylococcus. CFU counts ranged from 26.4 to 80.0 CFU/plate. CONCLUSIONS: Most of the phosphor plates evaluated shown to be contaminated, mainly by Staphylococcus ssp. Quantitatively, this contamination occurred at low levels, possibly arising from handling of the plates. The use of a second plastic barrier may have diminished contamination by microorganisms from the oral cavity. CLINICAL RELEVANCE: There is a risk of cross-contamination by phosphor storage plates used in dental radiology services.

Cell viability of Candida albicans against the antifungal activity of thymol.

Candida albicans is a commensal fungus, but circumstantially it may cause superficial infections of the mucous membranes, such as denture stomatitis, when a biofilm is formed on the surface of dental prostheses. This study evaluated the cell viability of C. albicans biofilms against the antifungal activity of thymol when compared with miconazole, by the fluorescence imaging using SYTO 9 and propidium iodide dyes, and counting of colony forming units. C. albicans standard strains (ATCC 11006) were used. The minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of drugs were determined by broth microdilution tests and the inoculum was standardized to match 0.5 on the McFarland scale (106 cfu/mL). Biofilms were grown on the surface of acrylic resin disks in parallel flow chambers from Sabouraud broth supplemented with 10% dextrose. For counting of colony forming units, the fungal solution was sequentially diluted and plated in Sabouraud dextrose agar. Data were analyzed using two-way ANOVA and Tukey's test (a=5%). Biofilms treated with thymol and miconazole presented low numbers of viable cells at the evaluated exposure times. There was statistically significant difference (p<0.05) when compared with control, and the mean value of the exposure times between miconazole and thymol did not differ significantly (p>0.05). In conclusion, both drugs have similar efficiency as antifungal agents against biofilms of C. albicans formed on acrylic surfaces.