To evaluate the impact of different sodium hypochlorite irrigation protocols on organic tissue dissolution in the periapical region of simulated immature permanent teeth.
Eight single-rooted premolars and 48 samples of porcine palatal mucosa were used. Acrylic resin prototypes were constructed, placing the tissue in close contact with the dental apices. Specimens were then divided into six groups (n=8): two control groups, of saline irrigation with (NS/WA) or without (NS/NA) ultrasonic activation, and four experimental groups, of 1.5% and 2.5% sodium hypochlorite irrigation, with (NaOCl 1.5%/WA and NaOCl 2.5%/WA) or without (NaOCl 1.5%/NA and NaOCl 2.5%/NA) activation. Root canals were irrigated with 20 mL of the solution for 5 minutes, distributed over four irrigation cycles. In each cycle, after irrigation, the solution was either kept stagnant or activated for 30 seconds and then replaced. Specimens were weighed on a precision balance before and after the irrigation protocols. Tissue dissolution was measured by the difference between the initial and final weights. One-way ANOVA was applied, followed by Tukey’s HSD test (α=0.05).
The NS/NA and NS/WA groups had mean weight reductions similar to the 1.5% NaOCl/NA group (p>0.05) and lower than the others (p<0.05). The 2.5% NaOCl/NA and 2.5% NaOCl/WA groups had the highest mean weight loss (p<0.05), while the 1.5% NaOCl/WA group had intermediate values (p<0.05).
Periapical tissue dissolution occurred in all groups, with greater impact observed with 2.5% NaOCl, with or without ultrasonic activation.

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