TITLE:
Comparative Evaluation of the Efficacy of Laser Activation and Ultrasonic Activation of Sodium Hypochlorite Against Enterococcus faecalis in Primary Teeth – A Randomized Controlled Trial

INTRODUCTION:
The primary objectives of pulp therapy in children are to preserve the integrity of the dental arch, maintain oral function, promote periodontal health, and ensure aesthetics. The success of endodontic treatment depends on several factors, including an accurate diagnosis, effective biomechanical preparation, and an appropriate irrigation protocol. However, the anatomical complexity of primary teeth, characterized by accessory canals, furcal foramina, and irregular root canal morphology, presents significant challenges for disinfection. Enterococcus faecalis, a gram-positive facultative anaerobe, is frequently associated with endodontic failures due to its resistance to conventional disinfectants and its ability to form resilient biofilms protected by an extracellular polymeric matrix.

An ideal root canal irrigant should possess antimicrobial properties, dissolve necrotic tissue, eliminate the smear layer, and be biocompatible. Sodium hypochlorite (NaOCl), used in concentrations ranging from 0.5% to 5.25%, is widely accepted as the gold standard irrigating solution due to its excellent tissue-dissolving, antibacterial, and lubricating properties. Advancements in irrigation techniques, such as laser and ultrasonic activation, have been developed to enhance the antimicrobial efficacy of NaOCl. Laser activation improves disinfection by enabling deeper penetration of energy into the dentinal tubules through photothermal, photomechanical, and light-scattering effects. Photodynamic therapy, which utilizes a photosensitizer activated by laser light, generates reactive oxygen species that effectively damage bacterial membranes and DNA, enhancing microbial reduction.

Ultrasonic irrigation uses acoustic streaming and cavitation effects to improve irrigant penetration and disrupt biofilms, significantly enhancing canal cleanliness. Despite these advancements, limited research exists comparing laser- and ultrasonic-activated irrigation in primary teeth, particularly against E. faecalis. Therefore, this study aims to compare the antibacterial efficacy of these advanced irrigation techniques using sodium hypochlorite in primary teeth, providing valuable insights for optimizing pediatric endodontic disinfection protocols.

METHODOLOGY:
This double-blind, randomized controlled trial will be conducted in the Department of Paediatric and Preventive Dentistry and the Department of Microbiology, following institutional ethical clearance. The study population will include children aged 4 to 9 years requiring endodontic treatment in primary molars. A total of 45 teeth will be randomly assigned to three groups (15 samples each) using the lottery method. The calculated sample size is based on a previous study by Varghese et al., with a 95% confidence interval and 80% power. Blinding will be ensured for both participants and operators.

Inclusion criteria include primary molars with irreversible pulpitis, adequate coronal structure for rubber dam isolation, at least two-thirds root length, and no antibiotic usage within four weeks prior to sampling. Exclusion criteria include teeth with abnormal anatomy, calcified canals, extensive pathological resorption, excessive mobility, and patients with systemic disorders.

The materials used will include 2.5% sodium hypochlorite (Prime Dental), a diode laser (Novolase Duo Laser), an ultrasonic activator (Eighteen Ultra X), and normal saline. The armamentarium will consist of rubber dam setup, K-files, barbed broach, sterile paper points, syringes, nutrient broth, and selective agar media.

Participants will be divided into three groups: Group A (control) will receive conventional irrigation with normal saline followed by 2.5% NaOCl; Group B will receive NaOCl with ultrasonic activation; and Group C will receive NaOCl with laser activation. Pre- and post-irrigation microbial samples will be collected using sterile paper points inserted into the root canal for one minute, then transferred to nutrient broth for microbiological analysis.

The endodontic procedure will include an oral rinse with 5 ml povidone-iodine, administration of local anesthesia, and rubber dam isolation. Access opening will be performed using a sterile diamond bur, followed by pulp extirpation and biomechanical preparation. Irrigation will be performed according to group allocation. Ultrasonic activation will involve inserting the ultrasonic tip 1–2 mm short of the working length, activating for 15–20 seconds per cycle, with 2–3 cycles per canal. Laser activation will be performed using a diode laser with a fiber-optic tip inserted 1–2 mm short of the working length, followed by gentle up-and-down activation movements to enhance irrigant distribution.

Samples will be transported to the microbiology laboratory within two hours of collection. Culturing will be performed on selective agar media to identify and quantify E. faecalis under aerobic and anaerobic conditions at 37°C for 24 to 48 hours. This study will provide comparative data on the effectiveness of laser- and ultrasonic-activated sodium hypochlorite irrigation in reducing E. faecalis in primary teeth, contributing to the advancement of pediatric endodontic disinfection protocols.