Efficacy of Minimal vs. Conventional Apical Preparation With Passive Ultrasonic Irrigation in Reducing Intracanal Bacteria: A Clinical Study

This randomized controlled clinical trial investigated the effect of different apical enlargement sizes and passive ultrasonic irrigation (PUI) on the bacterial load in the mesial roots of mandibular molars diagnosed with chronic apical periodontitis. The study was conducted at Istanbul Medipol University Faculty of Dentistry, Endodontics Clinic, and included 24 patients who required primary root canal treatment and exhibited clinical and radiographic signs of chronic apical periodontitis.

Participants were randomly assigned to two groups (n=12 each). In Group 1, root canal shaping was performed using a One Curve Mini #25/0.4 rotary file. In Group 2, shaping was performed using a One Curve Mini #35/0.4 rotary file. In both groups, passive ultrasonic irrigation was applied using the VDW Ultra device with an IRRI S 21/25 ultrasonic tip. The irrigation protocol consisted of three 20-second cycles using 1 ml of 3% sodium hypochlorite (NaOCl) per cycle. The ultrasonic tip was positioned 2 mm short of the working length without contacting the canal walls.

Bacterial samples were collected from the mesial root canals during the treatment. The bacterial load was quantified using Droplet Digital PCR (ddPCR), a highly sensitive and precise molecular technique that allows absolute quantification of bacterial DNA. This method was chosen because it enables accurate detection of bacterial reduction following the interventions.