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Objectives:The purpose of the present study was to evaluate the antimicrobial effect of various sizes and concentrations of zinc oxide (ZnO) nanoparticles on Streptococcus mutans (S. mutans), Enterococcus faecalis (E. faecalis), Lactobacillus fermentum (L. fermentum), and Candida albicans (C. albicans).Materials and Methods:Solutions at the concentration of 10 μg/ml were prepared using 20-nm, 40-nm, and 140-nm nano ZnO (nZnO) powder. The antimicrobial effect of nZnO was determined using the disk diffusion method. The inhibition zone (mm) was measured using a ruler. Data were analyzed by analysis of variance (ANOVA) and the Bonferroni correction. The minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of nZnO were determined using the broth microdilution method in Mueller-Hinton Agar (MHA) for S. mutans and E. faecalis, De Man, Rogosa, and Sharpe (MRS) agar, and Sabouraud Dextrose Agar (SDA).Results:The greatest inhibition zones were observed against S. mutans with 20-nm and 40-nm nZnO, while 140-nm nZnO formed the greatest inhibition zones against S. mutans and E. faecalis. The smallest inhibition zones were observed against C. albicans with the three nZnO particle sizes. The MICs for C. albicans with 40-nm and 140-nm particles and for L. fermentum with 140-nm particles were higher than 10 μg/ml. A significant correlation was found between the particle size and the antibacterial activity against S. mutans (P=0.00), L. fermentum, and E. faecalis (P<0.02).Conclusion:The antimicrobial activity of nZnO increases with decreasing the particle size. The greatest antimicrobial effect was observed against S. mutans and E. faecalis. S. mutans is more sensitive to the changes in the particle size compared to other bacteria.

The main purpose of this study was to assess the prevalence and distribution of decayed, missing, and filled teeth (DMFT) and enamel hypoplasia in 12-year old students in junior high school in Iran. Materials and Methods: This descriptive study was carried out in 2001 on 1,223 12-year old students, which were randomly selected in Yazd and Hadi-Shahr, Iran. A questionnaire was designed to record the status of the teeth along with the occupational and educational levels of parents. Data was analyzed using SPSS software, the Chi-square test, and analysis of variance (ANOVA). Results: The mean DMFT score was 1.8 ± 1.75 and 28.6% of the students were caries-free. There was no significant relationship between DMFT and the rate of dental caries with parents' education and occupation. The percentage of enamel hypoplasia was 32.7%. No statistically significant relationships were found between hypoplasia and DMFT with regard to gender. The relationship between enamel hypoplasia with DMFT score and dental caries was statistically significant. Conclusion: In the present study findings for DMFT scores in 12-year old junior high school children are higher than global standards according to the World Health Organization (WHO) references for the year 2000. There was a strong association between enamel hypoplasia and dental caries, and this subject suggests early diagnosis of enamel defects, health education programs, and suitable treatments should be emphasized in junior high school-aged children.

© Seer PublishingAbout the Author were significantly stronger than enamel bonded composite resin and a sandwich of glass ionomer cement, dentin bonding agent, and composite resin restorations.

Objectives: The objective of this study was to evaluate the antimicrobial activity of the essential oil obtained from oleo-gum-resin and seeds of Ferula assa-foetida. Materials and Methods: Ferula assa-foetida plants were collected from Tabas, Yazd Province, Iran, during summer 2017. Then, essential oils were obtained from its seeds and oleo-gum-resin using hydrodistillation. Gas chromatography-mass spectrometry (GC-MS) test was performed to determine the contents of the essential oils. Four different concentrations of each oil were prepared (2.5, 5, 10, and 20 μg/ml), and the antimicrobial activity of each dose against four oral bacteria (Streptococcus mutans, Streptococcus sobrinus, Streptococcus sanguis, Streptococcus salivarius, and Lactobacillus rhamnosus) was evaluated using the disk diffusion method. The data were analyzed using analysis of variance (ANOVA) and Kruskal-Wallis test in SPSS 17 software. Results: The GC-MS findings exhibited that the main compounds found in essential oils yielded from the seeds and oleo gum resin were (Z) -1-propenyl sec-butyl disulfide and (E) -1-propenyl sec-butyl disulfide. Ferula assa-foetida plant showed a significant antimicrobial effect (P<0.05). The essential oil from Ferula assa-foetida oleo-gum-resin had significantly stronger antibacterial properties compared to the essential oil from Ferula assa-foetida seeds (P<0.001). Both essential oils showed antibacterial properties similar to that of Chlorhexidine. The growth inhibition zone was significantly dependent on the essential oil concentration for all bacteria (P<0.05). Conclusion: Our study revealed that essential oils from seeds and oleo-gum-resin of Ferula assa-foetida have antimicrobial properties. More laboratory studies are required to reach a definitive conclusion.