Objective: Teeth bleaching causes an immediate decrease in resin composite bonding ability. This study aimed to investigate the influence of various antioxidants on resin composite bond strength to bleached enamel. Materials and methods: One hundred and ten human maxillary incisors were used. A negative control (group A) (n = 10) was assigned (no bleaching-no antioxidant). The remaining teeth were divided into two groups (n = 50) according to the bleaching agent used: group B (40% hydrogen peroxide) and group C (35% carbamide peroxide). Both groups were subdivided into five subgroups (n = 10). A positive control subgroup (no antioxidant) and other four subgroups according to the antioxidant solution used (10% sodium ascorbate, 10% grape seed extract, 10% green tea extract, and 5% alpha-lipoic acid). After resin composite building, the micro-shear bond strength test was performed. Fracture analysis was examined using a stereomicroscope. Statistical analysis was performed using a two-way analysis of variance and Tukey's HSD post hoc test. Results: Bond strength significantly decreased after bleaching and there was no significant difference between bleaching agents (P < .0848). Except for alpha-lipoic acid subgroups, the other antioxidants subgroups revealed significantly higher bond strengths than bleached control subgroups (P < .0001). Conclusion: All antioxidants used except alpha-lipoic acid were effective in the reversal of compromised bonding after bleaching. Clinical significance: Immediate bonding procedures after bleaching are requisite when bleaching fails to treat teeth discoloration and the direct composite veneer is considered, also when shades of old composite restorations become mismatched after bleaching and should be replaced. Immediate reestablishment of resin bond strengths after bleaching can be achieved by using several antioxidants without the need for delay.

This study was designed to evaluate the effect of water absorption of three resin based composite materials on their color stability Methods: using scanning spectrophotometer. A total of 45 disc samples were constructed from microhybrid resin composite, polyacid modified resin composite and giomer. It should be mentioned that the selected shade is A2. Then inserted in water for water absorption test. Using five different drink [mouth rinse (37•C) (Chlorohexidine containing mouthwash), tea, coffee, red wine and de-ionized water (37•C)] with no exposure to a light source (neutral sample). Three specimens from each restorative material were made for each type of drink. All the color testing were carried out according to the CIE-L * a * b * -color system whereby L * indicates the brightness of a color, a * describes the red-green content and b * the yellow-blue content.

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Objective: To evaluate the influence of fluoride varnish and casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) on bleached enamel microhardness. Materials and Methods: Thirty human permanent incisors were selected to preparer thirty enamel specimens. All specimens were bleached using 40% hydrogen peroxide bleaching agent (power whiting YF). The bleached enamel samples were divided into three equal groups (n = 10) according to the used remineralizing agent. Group A was treated by CPP-ACP past (GC Tooth mousse), group B was treated by Fl varnish (Biflourid 10) and group C was stored in artificial saliva. The microhardness was assessed using Vicker test (before bleaching, after bleaching and after application of different remineralizing agents). The data was collected and statistically analyze using two-way ANOVA and post hock LSD test at (P< 0.05). Results: Enamel microhardness has diminished significantly in all groups after bleaching. After application of remineralizing agents, there was a significant increase in microhardness. There was no significant difference between groups A and B, while there was significant difference between these groups and group C. Conclusions: Using fluoride, CPP-ACP or artificial saliva improves bleached enamel microhardness.

Objectives To compare flowable fiber‐reinforced and flowable bulk‐fill resin composites regarding their degree of conversion (DC) and microtensile bond strength (μTBS) to dentin in high C‐factor class I cavities. Materials and Methods One flowable fiber‐reinforced (EverX Flow, GC) and two flowable bulk‐fill composites (SDR, Dentsply, and Tetric N‐flow Bulk fill, Ivoclar Vivadent) were tested. Regarding DC, 10 cylindrical‐shaped specimens were prepared from each material (N = 30), measured using Fourier‐Transform Infrared Spectroscopy (FTIR). Regarding µTBS, class I cavities (4.5 × 4.5 × 3) were prepared on flat dentin surfaces of 30 molars, divided into three equal groups, restored with the three restorative materials, thermocycled, sectioned to create 1 mm × 1 mm cross‐sectional beams, then tested using a universal testing machine. Failure mode was assessed using a stereomicroscope. Two‐way ANOVA and Tukey's HSD post‐hoc tests were used in DC, while One‐way ANOVA was used for µTBS. Results The used materials showed statistically significant differences in DC with the fiber‐reinforced composite having the highest value. No statistically significant differences were found between the materials regarding their µTBS. Conclusions Flowable fiber‐reinforced composite provided the most DC performance compared to the flowable bulk‐fill composites. The three used restorative materials provided comparable bonding ability to dentin in high C‐factor cavities. Clinical Significance Flowable fiber‐reinforced resin composite is preferred as a dentin‐replacement material in high‐stress bearing areas. However, both flowable fiber‐reinforced and bulk‐fill resin composites are equally effective in bonding to dentin in high C‐factor cavities.