Role of phosphate-buffered saline on push-out bond strength of MTA Flow™ and Biodentine™ after acid challenge: An in vitro study.

Context: The physical and chemical properties of root repair materials are adversely affected when placed in areas of inflammation with acidic pH. Aim: To evaluate the role of phosphate-buffered saline (PBS- pH 7.4) on push-out bond strength (POBS) of MTA flow and Biodentine (BD) after acid challenge with butyric acid buffered solution (BABS- pH 5.4). Subjects and Methods: Eighty mid-root dentin slices (2 mm thick; 1.3 mm lumen diameter) were prepared and were divided into two groups (n = 40) based on the type of material used for filling lumen: Group 1-MTA Flow and Group 2-BD. Each group was again divided into four subgroups (n = 10) based on the duration of exposure to storage media: (a) 3 days in PBS, (b) 3 days in BABS, (c) 3 days in BABS followed by 30 days in PBS, and (d) 33 days in PBS. POBS was then measured using the universal strength testing machine. Statistical Analysis Used: Statistical analysis was performed with one-way analysis of variance and post hoc test using SPSS software version 23.0. Results: Group 1b and 2b showed significantly lower bond strength values. No significant difference was observed between Group 1b and Group 1c (P > 0.05), whereas highly significant POBS values were observed between Group 2b and Group 2c (P = 0.000). Among all the tested groups, Group 2d showed the highest POBS values. Conclusion: On storage in PBS after acid challenge, BD attained the highest POBS values while no significant difference was observed in MTA Flow.

To evaluate and compare the compressive strength of root dentin exposed to calcium hydroxide, mixed with various vehicles for a period of 30 days - An in vitro study.

Background: Long-term use of intracanal medicaments such as calcium hydroxide (CH) reduces the fracture resistance of dentin. Aim: This study aimed to evaluate and compare the compressive strength of root dentin exposed to CH, mixed with various vehicles after 30 days of placement. Settings and Design: Sixty single-rooted extracted human permanent premolars were collected, and complete instrumentation was done. Samples were divided into six groups. Materials and Methods: In Group I, no medicament was placed. In Group II, Group III, and Group IV, the root canals were filled with CH powder mixed with normal saline, distilled water, and local anesthetic solution. In Group V and Group VI, the root canals were filled with Metapaste and RC-Cal. Access cavities were sealed using IRM and were stored for 30 days. Teeth sectioned to obtain a 5 mm thick dentin cylinder subjected to compressive loading to evaluate the fracture resistance using a universal testing machine. Statistical Analysis: Results were analyzed using one-way ANOVA and multiple comparisons using Bonferroni test. Results: Highest mean compressive strength was recorded in Group I followed by Group II, Group IV, Group VI, Group III, and Group V. Conclusions: CH when used as a root canal dressing material will reduce the compressive strength of the teeth irrespective of the form of CH and vehicle.