Effect of autoclave sterilisation and heat activated sodium hypochlorite irrigation on the performance of nickel-titanium rotary files against cyclic fatigue

The present study aims to assess the impact of heat-activated sodium hypochlorite (NaOCl) and/or autoclave sterilisation on the cyclic fatigue resistance (CFR) of heat-treated nickel-titanium rotary files used in root canal treatment. The CFR of One Curve (OC) files was evaluated under the following conditions: as received (Group 1; control), immersion in NaOCl at 23 ± 1ºC (Group 2), immersion in NaOCl at 60 ± 1ºC (Group 3), autoclave sterilisation at 135 1ºC (Group 4), combined treatment of autoclave sterilisation and immersion in NaOCl at 23 ± 1ºC (Group 5), and combined treatment of autoclave sterilisation and immersion in NaOCl at 60 ± 1ºC (Group 6). A simulated root canal in a zirconia block was utilised to test the performance of the files. All the types of treatments resulted in significant reductions in fracture resistance of the OC files. Immersion of the files in NaOCl at 23ºC revealed the smallest reduction, while combined treatment of autoclaving and immersion in NaOCl at 60ºC caused the greatest reduction. Autoclave sterilisation or exposure of OC files to 2.5% NaOCl adversely affect the cyclic fatigue life and increasing solution temperature or combined treatment caused additionally significant reduction in CFR

Influence of different surface treatments on push‑out bond strengths of fiber‑reinforced posts luted with dual‑cure resin cement

Objectives: The objective was to evaluate whether fiber postsurface conditioning with air abrasion or erbium:yttrium‑aluminum‑garnet (Er:YAG) laser would influence the bond strength of dual‑cure resin cement to the fiber‑reinforced (FRC) posts.Materials and Methods: Twenty‑one FRC posts were divided into three groups according to surface treatment methods as follows: An untreated control group air abrasion with Al2O3 group, and Er:YAG laser treated group with 150 mJ parameter. Fiber posts were then built up to dual‑cure resin cement. Eighteen specimens were set and sectioned perpendicularly along the long axis of the post using a saw. Two disks (thickness of 2 mm) were obtained from each specimen (n = 12). Remaining three posts were stored for scanning electron microscopic evaluation. Push out test was performed on the each specimen and the values were recorded as MPa. The data were analyzed using one‑way analysis of variance and Tukey post‑hoc tests (P < 0.05).Results: The bond strength values for the groups were as follows: Control (15, 28 MPa), air abrasion group (19, 73 MPa), and Er:YAG group (17, 84 MPa). Air abrasion affected the bond strength significantly (P < 0.05).Conclusion: Air abrasion attained higher bond strengths when FRC posts were luted to dual‑cure resin cement. Additional studies should be designed with different types and parameters of laser devices to understand the effect of these devices on bond strength.Key words: Air abrasion, erbium:yttrium‑aluminum‑garnet laser, fiber reinforced post, push‑ou