Synthesis and characterization of hydroxyapatite nanoparticles and their effects on remineralization of demineralized enamel in the presence of Er,Cr: YSGG laser irradiation.

BACKGROUND: This study aims to synthesize and characterize hydroxyapatite nanoparticles (nano-HA) and evaluate their effects on the remineralization of demineralized enamel in the presence to Er,CR: YSGG laser irradiation. MATERIALS AND METHODS: Enamel specimens from 44 human molars were divided into four groups: control, demineralized enamel, demineralized enamel treated with nano-HA, and demineralized enamel treated with nano-HA followed by Er,Cr:YSGG laser irradiation (0.5, 20 Hz, 60 µs, 20 s). Vickers microhardness test was used to evaluate the enamel surface hardness. The morphology and chemistry of enamel surfaces were assessed using scanning electron microscopy (SEM) and Raman spectroscopy, respectively. RESULT: The result of this study showed that the application of Er,CR: YSGG laser irradiation to demineralized enamel treated with nano-HA had the highest impact on its microhardness. CONCLUSION: ER,CR: YSGG laser irradiation promotes enamel remineralization after treatment with nano HA.

Relationship between dental plaque formation and salivary cortisol level in pregnant women.

PURPOSE: Understanding how increased level of salivary cortisol contributes to the development of dental biofilm during pregnancy can help inthe prevention of dental caries and periodontal diseases. This study aims to evaluate the relationship between salivary cortisol level and dental biofilm formation in pregnant women. PATIENTS AND METHODS: This descriptive-analytic study was conducted in Hamadan, Iran in 2011. Forty consecutive pregnant women with no history of abortion, stillbirth, or any known physical or psychological disorders at weeks 25 and 33 of gestation were included. Salivary samples were collected for measurement of cortisol levels by Enzyme Linked Immunoabsorbent Assay (ELISA) method. The amount and extension of dental biofilms were determined by using a disclosing agent. Data were analyzed using descriptive and analytical statistics in SPSS version 16. RESULTS: The mean levels of salivary cortisol at weeks 25 and 33 of gestation were respectively, 2.45 ± 1.56 µg/dl and 5.24 ± 4.07 µg/dl which demonstrates a significant difference (P<0.001). Evaluation of dental biofilm at two time intervals revealed a significant increase in amount of dental biofilm at week 33 of gestational period (34.65 ± 10.9% vs. 42.45 ± 12.35%, P<0.001). Elevated levels of dental biofilm were significantly correlated with salivary cortisol levels at week 33 (r=0.494, P=0.001),however, it was not significant at week 25 of gestation (r=0.148, P=0.361). CONCLUSION: The findings suggested that increased levels of salivary cortisol can predict dental biofilm formation and accumulation in pregnant women in the last weeks of gestation.

Effect of Accelerated Artificial Aging on Translucency of Methacrylate and Silorane-Based Composite Resins.

OBJECTIVES: Composite restorations must have tooth-like optical properties namely color and translucency and maintain them for a long time. This study aimed to compare the effect of accelerated artificial aging (AAA) on the translucency of three methacrylate-based composites (Filtek Z250, Filtek Z250XT and Filtek Z350XT) and one silorane-based composite resin (Filtek P90). MATERIALS AND METHODS: For this in vitro study, 56 composite discs were fabricated (n=14 for each group). Using scanning spectrophotometer, CIE L*a*b* parameters and translucency of each specimen were measured at 24 hours and after AAA for 384 hours. Data were analyzed using one-way ANOVA, Tukey's test and paired t-test at P=0.05 level of significance. RESULTS: The mean (±standard deviation) translucency parameter for Filtek Z250, Filtek Z250XT, Filtek Z350XT and Filtek P90 was 5.67±0.64, 4.59±0.77, 7.87±0.82 and 4.21±0.71 before AAA and 4.25±0.615, 3.53±0.73, 5.94±0.57 and 4.12±0.54 after AAA, respectively. After aging, the translucency of methacrylate-based composites decreased significantly (P<0.05). However, the translucency of Filtek P90 did not change significantly (P>0.05). CONCLUSIONS: The AAA significantly decreased the translucency of methacrylate-based composites (Filtek Z250, Filtek Z250XT and Filtek Z350XT) but no change occurred in the translucency of Filtek P90 silorane-based composite.

The antibacterial properties of composite resin containing nanosilver against Streptococcus mutans and Lactobacillus.

AIM: The aim was to evaluate the antibacterial properties of composite resin containing nanosilver against Streptococcus mutans (SM) and Lactobacillus (L). MATERIALS AND METHODS: Nanosilver was added to Z250 composite at 0.5 and 1% by weight. In order to confirm the homogenous distribution of the nanoparticles in the composite resin, SEM-EDX analysis was performed on one sample in each group. Z250 composite without nanosilver was used as control. Direct contact test was used to test the antibacterial properties of nanoparticle-loaded composites: 0.001 ml of 0.5 Mc Farland suspension of MS and L was placed on composite disks, and incubated for 1 hour in 5 to 10% CO2 incubator at 37°C. Samples were placed in 0.5 ml of sterile BHI broth and incubated for 2 hours in CO2 incubator. Afterwards, 0.001 ml liquid from each medium was distributed on blood agar plates and incubated for 48 hours in CO2 incubator. The numbers of bacterial colonies were counted visually. Data were analyzed using Two-way ANOVA and Tukey HSD test. Significance level was set at 0.05. RESULTS: Addition of nanosilver to composite resin had a significant effect on reduction of the number of SM and L colonies (p = 0.000). The antibacterial properties of composite resins are different depending on the concentration of nanosilver (p = 0.014). Tukey test indicated that increase in the concentration of nanosilver caused the increase in antibacterial properties of composite resin. CONCLUSION: Addition of silver nanoparticles to Z250 composite could significantly inhibit the growth of Streptococcus mutans and Lactobacillus on the surface of this composite. CLINICAL SIGNIFICANCE: The addition of nanosilver to Z250 composite could inhibit the growth of SM and L on the surface of the restoration and therefore prevent the occurrence of secondary caries.