Influence of Filling Material Remnants on the Diffusion of Hydroxyl Ions in Endodontically Retreated Teeth: An Study.

Aim: To assess the influence of remnants of filling material on hydroxyl ion diffusion from calcium hydroxide (CH) paste, measured by the pH value, in retreated teeth.

Materials And Methods: A total of 120 single-rooted extracted teeth were prepared up to a size 35 hand file and filled. For retreatment, the specimens were divided into four groups ( = 20): ProTaper Universal Retreatment (PUR), PUR with additional instrumentation (PURA), Mtwo Retreatment (MTWR), and MTWR with additional instrumentation (MTWRA). Negative (NEG) and positive (POS) control groups were composed by 20 specimens each one. The specimens, except NEG, were filled with CH paste. The retreated groups were scanned using cone-beam computed tomography (CBCT) for analysis of filling remnants. The pH assessment was performed at the baseline, after seven, 21, 45, and 60 days of immersion in saline. Data were analyzed using Shapiro-Wilk and Levene's test, followed by a two-way analysis of variance (ANOVA) and Tukey's test.

Results: Additional instrumentation (PURA and MTWRA) were superior regarding removal of the filling material ( <0.05); however, without significant difference ( >0.05). The mean pH value in all groups increased ( <0.05). After 60 days, no statistical difference was observed among POS and PURA; and MTWR and MTWRA. There was less diffusion of hydroxyl ions when the amount of remnants was greater than 59%.

Conclusion: Additional instrumentation improved the ability to remove filling material in both systems. All groups presented increasing pH; however, the higher the amount of remnants, the lower the diffusion of hydroxyl ions.

Clinical Significance: The amount of remnants allows less diffusion of calcium hydroxyl ions. Thus, additional instrumentation improves the ability to remove these materials.