Do Different Tooth Bleaching-Remineralizing Regimens Affect the Bleaching Effectiveness and Enamel Microhardness In Vitro?

Objective: Tooth bleaching may negatively affect the enamel surface properties, such as reduction in hardness values, and remineralizing agents can reverse these effects. This study evaluated the effect of remineralizing agents before, during, and after the bleaching process on enamel's whitening effectiveness and microhardness. Methods and Materials: The initial color of 104 bovine incisors after immersion in tea solution was recorded, and then, the teeth were randomly divided into eight groups (n = 13). Group 1 (NC) was considered the control with no treatment, and Group 2 (B) was bleached with 40% hydrogen peroxide gel. The 3% fluorohydroxyapatite (FHA) and 2% sodium fluoride (NaF) were applied before (FHA/B, NaF/B), during (FHA + B, NaF + B) and after (B/FHA, B/NaF) the bleaching process in other groups. The final color and microhardness in three depths of 20-30, 50-60, and 100-120 µm were measured. Data were analyzed using Shapiro-Wilk, one-way ANOVA, Tukey, Games Howell, repeated measurement, and LSD tests. Results: The FHA + B presented the lowest ΔE, significantly lower than other groups, except B/FHA. The ΔE in B/FHA was significantly lower than B/NaF. The bleaching significantly reduced the enamel hardness in three depths. The highest microhardness values were reported for B/NaF and NaF + B, which have no noticeable difference with NC, while FHA/B showed the lowest hardness in three depths, which was significantly lower than NC. Conclusion: The application of NaF before, during, and after the bleaching improved the microhardness of bleached enamel as the unbleached one with no adverse effect on whitening effectiveness.

Formulation and antibacterial properties of lollipops containing of chitosan- zinc oxide nano particles on planktonic and biofilm forms of Streptococcus mutans and Lactobacillus acidophilus.

This study aimed to formulate and characterize the experimental lollipops containing chitosan- zinc oxide nanoparticles (CH-ZnO NPs) and investigate their antimicrobial effects against some cariogenic bacteria. The CH-ZnO NPs were synthesized and characterized by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) analysis, and Transmission electron microscope (TEM). Then, four groups were made, including lollipops coated with 2 and 4 ml of CH-ZnO NPs, 0.7 ml CH-ZnO NPs incorporated lollipops, and those with no CH-ZnO NPs. Their antibacterial effectiveness against Streptococcus mutans and Lactobacillus acidophilus was evaluated by direct contact test and tissue culture plate method in planktonic and biofilm phases, respectively. Chlorhexidine mouthrinse (CHX) was used as a positive control group. In the planktonic phase, the antibacterial properties of both groups coated with CH-ZnO NPs were comparable and significantly higher than incorporated ones. There was no significant difference between CHX and the lollipops coated with 4 ml of NPs against S. mutans and CHX and two coated groups against L. acidophilus. None of the experimental lollipops in the biofilm phase could reduce both bacteria counts. The experimental lollipops coated with 2 and 4 ml of CH-ZnO NPs could reveal favorable antimicrobial properties against two cariogenic bacteria in the planktonic phase.

Effect of Extent of White Spot Lesions on the Esthetic Outcome after Treatment by the Resin Infiltration Technique: A Clinical Trial.

Objectives: This study aimed to assess the effect of extent of white spot lesions (WSLs) on the esthetic outcome (masking effect and durability) for 6 months after treatment by the resin infiltration technique. Materials and Methods: In this clinical trial, 79 teeth with WSLs in 18 patients were selected. The lesions were assigned to localized and generalized groups, and were all treated by resin infiltration. The color of WSLs was assessed at baseline, immediately after treatment, and 1, 3, and 6 months after treatment by using Easy Shade spectrophotometer and taking standard digital photographs. The surface area of WSLs was calculated on the photographs using MIP4Student software. Repeated Measures ANOVA was used to compare color change (∆E), and the Pearson's correlation test was applied to analyze the association between the extent of lesions and ∆E (alpha=0.05). Results: A significant difference was found between the two groups in ∆E at different time points (P<0.05). Also, in both localized and generalized lesions, the pretreatment ∆E was significantly different from the ∆E values at different time points after treatment (P<0.001). However, the post-treatment ∆E values were not significantly different (P>0.05). The Pearson test showed an inverse correlation between the extent of lesions and ∆E (P<0.05). Conclusion: The resin infiltration technique is successful in masking the WSLs, with a durability of at least 6 months. Color correction by this technique is more favorable in localized lesions.