To compare the intensity and trajectory of postoperative pain (0-72 hours) between (A) a conventional final irrigation protocol without activation and (B) a PDT-augmented final disinfection in mandibular molars and premolars.

This retrospective controlled clinical cohort study investigated the effects of photodynamic therapy (PDT) on post-endodontic pain in mandibular molars and premolars treated by undergraduate students. Eligible patients were selected from the Istanbul Atlas University Faculty of Dentistry clinics. Inclusion criteria encompassed adult patients requiring endodontic treatment in posterior teeth, without systemic contraindications or signs of acute apical abscess.

Participants were assigned to one of two groups:

(A) conventional final irrigation without activation (control), and (B) PDT-augmented final disinfection (experimental).

All treatments were performed by undergraduate dental students under faculty supervision. Root canals were shaped using a standardized rotary instrumentation protocol. In both groups, final irrigation included 2.5% sodium hypochlorite (NaOCl), followed by 17% EDTA for smear layer removal.

In the experimental group, after completion of the same irrigation regimen, a methylene blue photosensitizer was introduced into the canal and allowed to remain for 60 seconds. The dye was subsequently activated using an intra-canal diode laser fiber for 60 seconds per canal, following manufacturer instructions for photodynamic therapy. All canals were obturated at the second visit using the single-cone technique.

Postoperative pain was measured using a visual analog scale (VAS) at 6, 24, 48, and 72 hours after treatment. Additional variables such as analgesic consumption, incidence of flare-ups, unscheduled visits, and the time required to achieve a pain-free state were also recorded. This study aimed to determine whether adjunctive PDT could reduce early post-endodontic pain in treatments performed by undergraduate practitioners.

Inclusion Criteria:

Adults aged 18-60 years Patients requiring primary endodontic treatment of posterior teeth (premolars or molars) Patients without systemic diseases Patients treated at the Istanbul Atlas University Faculty of Dentistry student clinic Teeth with no intraoperative complications (no perforation, no instrument separation, no ledge formation) Treatments completed with either photodynamic therapy (PDT) activation or no activation (control group)

Exclusion Criteria:

Teeth with previous root canal treatment Teeth with open apices Presence of severe periodontal disease Incomplete clinical or radiographic records Patients with systemic conditions that may influence postoperative pain perception Any intraoperative complications during treatment (perforation, ledge, instrument separation, etc.) Presence of acute apical abscess

Patients aged 18-60 years who received primary endodontic treatment of mandibular premolars or molars at the Istanbul Atlas University Faculty of Dentistry student clinic. All treatments were performed by undergraduate dental students under supervision. Eligible patients had no systemic diseases and presented with teeth requiring primary root canal therapy without intraoperative complications.