Aim: This study was fulfilled to evaluate the flexural strength, micro-hardness, and release of two fluoride ions of bioactive restorative materials (Cention N and Activa Bioactive), a resin modified glass ionomer (Fuji II LC), and a resin composite (Filtek z250). Methods: Forty samples from four restorative materials (Activa Bioactive, Fuji II LC, Cention N, and Filtek Z250) were provided according to the current standards of ISO 4049/2000 guide lines. Subsequently, the samples were stored for 24 hours and 6 months in artificial saliva, and successively, flexural strength and micro-hardness of the samples were measured. For each studied groups the pH was decreased from 6.8 to 4 in storage solution. The rate of changes in fluoride ion release was measured after three different storage periods of 24 hours, 48 hours, and 6 months in distilled water, according to the previous studies’ method. Two-way ANOVA, One-way ANOVA, Tukey HSD Pair wise comparisons, and independent t-tests were used to analyze data (α= 0.05). Results: The highest flexural strength and surface micro-hardness after 24 hours and also after 6 month were observed for Cention N(p<0.001).Flexural strength of all samples stored for 6 months was significantly lower than the samples stored for 24 hours(p<0.001). The accumulative amount of the released fluoride ion in RMGI, after six-month storage period in distilled water was considerably higher (p<0.001) than 24 hours and 48 hours storage. The amount of fluoride ion release with increasing acidity of the environment (from pH 6.8 to 4) in Fuji II LC glass ionomer was higher than the bioactive materials (p<0.05). Conclusion: The flexural strength of RMGI was increased after storage against the Activa Bioactive,Cention N and Z250 composite. Storage of restorative materials in artificial saliva leads to a significant reduction in micro hardness. The behavior and amount of released fluoride ions in these restorative materials, which are stored in an acidic environment, were dependent on the type of restorative material.

Objectives This study investigated the microhardness, flexural strength, and color stability of bleach-shade resin composites cured with 3 different light-curing units. Materials and Methods In this in vitro experimental study, 270 samples were fabricated of bleach and A2 shades of 3 commercial resin composites (Point 4, G-aenial Anterior, and Estelite Sigma Quick). Samples ( n = 5 for each trial) were cured with Bluephase N, Woodpecker LED.D, and Optilux 501 units and underwent Vickers microhardness and flexural strength tests. The samples were tested after 24 hours of storage in distilled water. Color was assessed using a spectrophotometer immediately after preparation and 24 hours after curing. Data were analyzed using 3-way analysis of variance and the Tukey test ( p ≤ 0.001). Results Samples cured with Optilux exhibited the highest and those cured with LED.D exhibited the lowest microhardness ( p = 0.023). The bleach shade of Point 4 composite cured with Optilux displayed the highest flexural strength, while the same composite and shade cured with Sigma Quick exhibited the lowest ( p ≤ 0.001). The color change after 24 hours was greatest for the bleach shade of G-aenial cured with Bluephase N and least for the A2 shade of Sigma Quick cured with Optilux ( p ≤ 0.001). Conclusions Light curing with polywave light-emitting diode (LED) yielded results between or statistically similar to those of quartz-tungsten-halogen and monowave LED in the microhardness and flexural strength of both A2 and bleach shades of resin composites. However, the brands of light-curing devices showed significant differences in color stability.

Objectives: This study compared the effect of two whitening toothpastes on composite specimens discolored with 0.2% chlorhexidine (CHX). Materials and Methods: Twenty-four composite specimens were fabricated from Charisma Diamond composite resin. The initial color of specimens was measured according to the CIE L*a*b* color system using a spectrophotometer. The specimens were immersed in 0.2% CHX twice a day for 1 minute each time, for 2 weeks. The color of specimens was measured again, and the specimens were assigned to three groups (n=8). The control group specimens were immersed in distilled water. The two test group specimens were brushed twice daily for 21 days with Oral B toothbrush and Signal White Now and Crest 3D White whitening toothpastes each time for 30 seconds. The color of specimens was measured again. Data were analyzed by one-way ANOVA and t-test. Results: CHX increased the a, b, and L color parameters in all groups.  There were no significant differences in ΔL (P=0.10), Δa (P=0.24), and Δb (P=0.07) among the study groups. The a, b, and L parameters decreased after brushing the specimens discolored with 0.2% CHX with the whitening toothpastes. There were significant differences in ΔL (P=0.03), Δa (P=0.02), and Δb (P=0.01) among the three study groups after using the whitening toothpastes. The highest ΔL, Δa, Δb, and ΔE values were recorded in Crest 3D White group, followed by Signal White Now group. Conclusion: Crest 3D White whitening toothpaste had higher efficacy to resume the original color of composite specimens discolored with 0.2% CHX.

Due to an increase in prevalence of cervical lesions, it is important to use appropriate restorative materials to reduce the incidence of secondary lesions. Owing to having antibacterial properties, cervical composite restorations containing different ratios of Zinc Oxide nanoparticles (ZnO NPs) have been analyzed using the Finite Element method to determine the optimal incorporation ratio from mechanical and thermal perspectives. A numerical simulation is conducted for a mandibular first premolar with a cervical lesion (1.5 × 2 × 3 mm3) restored with composites containing 0 to 5% wt. ZnO NPs. Subsequently, the samples are exposed to different thermo-mechanical boundary conditions, and stress distributions at different margins are examined. The accumulated stress in the restoration part increases for the 1% wt. sample, whereas the higher percentage of ZnO NPs leads to the reduction of stress values. In terms of different loading conditions, the least and most stress values in the restoration part are observed in central loading and lingually oblique force, respectively. The change in the surface temperature is inversely correlated with the ratio of ZnO NPs. In conclusion, the composite containing 5% wt. ZnO NPs showed the most proper thermo-mechanical behavior among all samples.

Introduction: Discoloration of resin composite restorations can lead to patient dissatisfaction. 0.2% Chlorhexidine and Persica mouthwashes are among the agents that cause discoloration. The aim of this study was to investigate the degree of discoloration caused by the 0.2% Chlorhexidine and Persica mouthwashes on resin composite samples. Materials and Methods: This in-vitro experimental study was conducted in Kashan and Isfahan School of Dentistry in 2020-2021. Number of 30 disc-shaped samples were fabricated from Charisma Diamond resin composite. The initial color of samples was measured by CIE Lab system in spectrophotometer. Then samples were divided into 3 groups (A, B, and C) (n = 10).The control group (A) was placed in distilled water, group B was immersed in the 0.2% Chlorhexidine mouthwash and group C was immersed in the Persica mouthwash. The color of the samples was measured again afterwards. Data were analyzed with One-way ANOVA and t-Test (α = 0.05). Results: The amount of l, a, b and ΔE after using 0.2% Chlorhexidine and Persica mouthwashes increased. The mean of Δl, Δa, Δb and ΔE showed significant differences between groups (p value < 0.05). Conclusion: The discoloration of Persica mouthwash was more than 0.2% Chlorhexidine mouthwash and control group. Therefore, for patients with resin composite restorations, 0.2% Chlorhexidine mouthwash is better.