Laser-Activated Versus Passive Ultrasonic Irrigation in Endodontic Retreatment

This study will compare three methods of activating the final irrigation solution in reducing living bacteria inside the root canals of teeth that require root canal retreatment because of apical periodontitis, an inflammatory condition of the tissues around the root tip. The three methods are photon-induced photoacoustic streaming (PIPS), shock wave-enhanced emission photoacoustic streaming (SWEEPS), and passive ultrasonic irrigation (PUI). Ninety adults requiring retreatment of a single-rooted, single-canal tooth will be randomly assigned to three groups; all treatment steps other than the activation method will be identical. Root canal samples will be collected at several stages of the single-visit treatment, and living bacteria will be counted using laboratory cultures. In addition, real-time PCR will be used to measure the relative amount of Enterococcus faecalis DNA compared with total bacterial DNA. Because PCR cannot distinguish living from dead bacteria, these molecular results will be interpreted as complementary to the culture findings.

Inclusion Criteria: * Adults aged 18-65 years who are systemically healthy (American Society of Anesthesiologists physical status classification I). * A previously root canal-treated, single-rooted tooth with a single root canal requiring nonsurgical root canal retreatment. * Persistent or secondary apical periodontitis with a Periapical Index (PAI) score of at least 3. * Root canal filling material considered completely removable by nonsurgical means. * Sufficient coronal tooth structure to allow rubber dam isolation. * Only one tooth per participant will be included. Exclusion Criteria: * Antibiotic use within the preceding 3 months. * Pregnancy or breastfeeding. * American Society of Anesthesiologists physical status classification II or higher. * Periodontal probing depth greater than 4 mm in the study tooth. * Root fracture, perforation, or root resorption in the study tooth. * A calcified or non-negotiable root canal. * Acute abscess or active drainage. * A non-removable post or a separated instrument in the root canal.