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Background: 35% Hydrogen peroxide (H2O2) as an active material for internal bleaching can produce free radicals that can affect resin tag penetration into the dentinal tubules. Application of 10% and 35% green tea (GT) extract as an antioxidant after 2 minutes are expected to remove free radical residues and increase dentin shear bond strength and resin tags penetration depth after non-vital bleaching. Methods: 30 extracted healthy human premolars were cut horizontally 2 mm from the Cemento Enamel Junction margin to the crown part, then cut in a mesio-distal direction into two parts. The specimens were divided into five groups: normal dentin, post bleaching dentin, delayed 2 weeks, 10% GT, and 35% GT group. Non-vital walking bleach with 35% H2O2 gel was done to all groups except control group. Soon after, 10% and 35% GT extract gel were applied on dentin for 2 minutes, then the specimens were rinsed-off with aquabidest for 2 minutes and dried. All specimens were etched and bonded with an etch-and-rinse adhesive system and filled with resin composite. The shear bond strength assessment was carried out using a Universal Testing Machine (UTM) with a cross-head speed of 0.5 mm/minute. Confocal laser scanning microscopy (CLSM) with a wavelength of 560 nm and a lens magnification of 40x was used to analyze the resin tag penetration. Data were analyzed by one way ANOVA and t-test. Results: There was a significant difference in resin tag penetration depth and shear bond strength between applying 10% and 35% GT extract (p < 0.05). The 35% GT extract group resulted in a significantly longer resin tag penetration than the 10% GT extract group. Conclusions: The application of 35% GT extract is more effective than 10% GT extract as an antioxidant for increasing the shear bond strength of composite resin after internal bleaching.

Background Nowadays, the universal adhesive become more popular among clinicians due to its simple procedure. The application of universal adhesive on root canal dentin prior the self-adhesive resin cement may increase bond-strength between fiber post and dentin. The objective of this study was to evaluate the effect of different etching modes (etch-and-rinse and self-etch) to universal adhesives on push-out bond strength of fiber post. Material and Methods Thirty extracted sound human lower premolars were randomly divided into three groups based on adhesives systems prior to fiber post cementation; two-step etch-and-rinse (group A, Adper Scotchbond), etch-and-rinse universal (group B, Prime & Bond Universal), and self-etch universal (group C, Prime & Bond Universal). After adhesive application, self-adhesive resin cement was filled to the prepared root canal (Smart CEM2, Dentsply) for fiber post cementation. The adhesion between the fiber post and root canal walls was investigated using push-out test after 24 h water storage at 37◦C and the modes of failure were determined under SEM. Data were analyzed using two-way ANOVA test and the Bonferroni test was used to compare values among the three adhesives groups, followed by Tukey HSD for multiple comparisons. Furthermore, Weibull parameters were calculated for tested groups. Results Universal adhesive with self-etch mode significantly improved bond-strength compared to the two-step etch-and-rinse group ( p <0.05). The coronal part has higher bond strength than the apical section ( p <0.05). However, the bond-strength in two-step etch-and-rinse and etch-and-rinse universal was not significantly different. Self-etch mode showed higher bond strength compared to etch-and-rinse universal adhesive in the apical root section ( p <0.05). SEM revealed that all tested groups predominantly had an adhesive failure ( p >0.05). Conclusions Self-etch mode in universal adhesive system were effectively improved the push-out bond strength of fiber post to root canal dentin, especially in apical root section. Key words: Push-out bond-strength, self-adhesive resin cement, self-etch adhesive, total-etch.

Deciding on what treatment (repair or replacement) to provide for a failed indirect restoration can be challenging. Notably, the strength of the residual tooth structure could be improved after replacing the failed indirect restoration using a minimally invasive strategy. Objective: To describe the use of a minimally invasive strategy for the successful clinical replacement of two failed indirect metal restorations with direct composite restorations and the attainment of bonded restoration. Case Report: Case 1. A 52-year-old male patient came to the dental hospital complaining of discomfort when drinking cold beverages and food impaction on the proximal area of the upper left first molar. Case 2. A 45-year-old female patient complained about her debonded metal onlay and secondary caries in the upper right second molar. Both of these indirect restoration failures were treated with direct resin composite restoration. Both patients were highly satisfied with the results. Conclusion: This report presents the benefits of adopting a minimally invasive strategy approach for replacing failed indirect restorations (inlays and onlays) with direct-bonded composite restorations. Minimally invasive direct restorations are designed to maximize the preservation of tooth structure, thereby ensuring a long-term bonded restoration and leaving future options open when a failure occurs.

Complexities in obturation and difficulties in disinfection are the major problems that make endodontic treatment very time-consuming. A new perspective is needed to reduce the working time as well as to answer these two problems. Until now, none of the established obturation techniques for root canal filling can guarantee a perfect seal. Solid substances cannot be manipulated easily to fill the tiny branches of the root canal system hermetically. At the same time, anaerobes and facultative anaerobes, especially Enterococcus faecalis, are very dominant in endodontic infections discussion. As shown in many studies, it is extremely difficult to perfectly disinfect Enterococcus faecalis even by using some irrigating solutions with strong antibacterial properties. Under anaerobic conditions, the invasion efficiency of facultative anaerobes is increased. In case irrigation and disinfection cannot totally eliminate anaerobes and facultative anaerobes, a new strategy is also needed to deal with the bacteria that still survive in the root canal. Oxygen can fill the root canal system with ease, eliminate anaerobes, and prevent facultative anaerobes from being pathogenic. Therefore, using oxygen as obturation biomaterial after proper cleaning and shaping procedures is expected to solve the two major endodontic problems. The aim of this article was to discuss a new possible concept of dental restoration system that uses an oxygen-permeable membrane to decrease the time required in endodontic treatment. The membrane is placed at the orifice of a duct created to connect the entire root canal system with free air outside the restoration. The function of the membrane is more or less similar to the mask used during the COVID-19 pandemic, as it enables the oxygen to circulate while preventing any fluid, debris, and microorganisms from passing. We hypothesize that the oxygen circulating in the root canal system will also act as an antimicrobial agent that is constantly renewed.