Removal of double antibiotic paste and calcium hydroxide from simulated models of regenerative endodontic procedures using several protocols of irrigation: in-vitro comparison study

Introduction
Although medicinal dressings are essential in regenerative endodontic procedures, they may adversely affect stem cells viability of periapical papilla. Objectives: This study was conducted to compare the efficacy of different irrigation protocols on dressings removal from root canal undergoing regenerative endodontic procedures (REPs).

Material and methods
A total of 69 single canal teeth were shaped and standardized in length. Irrigation was performed according to the 2018 recommendations of the American Association of Endodontic and then, the apical part was enclosed by resin-modified glass ionomer (RMGI). Double antimicrobial paste (DAP) was applied at a concentration of 1 mg/ml in group 1 (n = 30), followed by coronal sealing by RMGI, whereas calcium hydroxide Ca(OH)2 was used in group 2. Group 3 (n = 6) was fully filled by both of dressings as a posi­tive group, while group 4 (n = 3) was empty as a negative group. The samples were preserved in humidity for 3 weeks; group 1 and group 2 were divided into 3 sub-groups (n = 10) (EDTA and ultrasonic, EDTA and sonic, and EDTA and hybrid activation; ultrasonic followed by sonic activation), and the irrigation was performed. Teeth were split longitudinally, and the residues were evaluated under 40x microscopic magnification. Data were collected, and the results were recorded and statistically analyzed using Kruskal-Wallis test at a confidence level of 95%.

Results
Hybrid activation was the most effective protocol for removal of both dressings in the apical third, followed by sonic irrigation with no statistical differences, and by passive ultrasonic irrigation with statistical differences in DAP group.

Conclusions
Hybrid activation showed predictable removal of residues, but there was no protocol that could completely remove the dressing from the canal.