Laser-Assisted Disinfection With and Without Photobiomodulation in Regenerative Endodontic Procedures for Necrotic Mature Teeth (LASER)

Regenerative endodontic procedure (REP) with conventional chemomechanical preparation only (2.5% sodium hypochlorite, passive ultrasonic activation, 17% EDTA, and sterile saline), followed by a calcium hydroxide intracanal dressing for 2 weeks. At the second visit: EDTA irrigation, induced apical bleeding to form a blood clot, collagen matrix, bioceramic putty barrier, and coronal seal. No laser is used.

Two-visit regenerative endodontic procedure for necrotic mature teeth single root and single canal. Visit 1: access, working length determination, crown-down chemomechanical preparation with 2.5% sodium hypochlorite, passive ultrasonic activation, 17% EDTA, final saline rinse, and calcium hydroxide dressing for 2 weeks. Visit 2: 17% EDTA irrigation, induction of apical bleeding to form a blood clot, collagen matrix, bioceramic putty barrier, and coronal seal with glass ionomer. Performed identically in all three groups.

Same REP protocol as the control group, with the addition of 810 nm diode laser disinfection at the first visit after the final saline rinse and before the calcium hydroxide dressing. Continuous wave mode, 1.5 W, 4 cycles of 5 seconds with 20-second intervals, using a 200 micrometer fiber placed 1 mm short of the working length and moved in a slow helical motion from apical to coronal. The canal is irrigated with 5 mL saline after each cycle. The second visit is identical to the control group.

Two-visit regenerative endodontic procedure for necrotic mature teeth single root and single canal. Visit 1: access, working length determination, crown-down chemomechanical preparation with 2.5% sodium hypochlorite, passive ultrasonic activation, 17% EDTA, final saline rinse, and calcium hydroxide dressing for 2 weeks. Visit 2: 17% EDTA irrigation, induction of apical bleeding to form a blood clot, collagen matrix, bioceramic putty barrier, and coronal seal with glass ionomer. Performed identically in all three groups.

Adjunctive canal disinfection at the first visit using an 810 nm diode laser (Elexxion, Germany), continuous wave, 1.5 W, 4 cycles of 5 seconds with 20-second intervals. A 200 micrometer fiber is placed 1 mm short of the working length and moved in a slow helical motion from apical to coronal at about 2 mm per second without touching the canal walls. The canal is irrigated with 5 mL sterile saline after each cycle.

Same protocol as the laser-assisted disinfection group, plus a single session of transmucosal photobiomodulation (PBM) delivered at the second visit immediately after placement of the blood scaffold and coronal restoration. 810 nm diode laser, continuous wave, 200 mW, 8 mm tip in contact with the mucosa, applied at four sites per tooth (periapical and cervical regions on the buccal and lingual/palatal sides), 15 seconds and 3 J per site, for a total of 12 J per tooth.

Two-visit regenerative endodontic procedure for necrotic mature teeth single root and single canal. Visit 1: access, working length determination, crown-down chemomechanical preparation with 2.5% sodium hypochlorite, passive ultrasonic activation, 17% EDTA, final saline rinse, and calcium hydroxide dressing for 2 weeks. Visit 2: 17% EDTA irrigation, induction of apical bleeding to form a blood clot, collagen matrix, bioceramic putty barrier, and coronal seal with glass ionomer. Performed identically in all three groups.

Adjunctive canal disinfection at the first visit using an 810 nm diode laser (Elexxion, Germany), continuous wave, 1.5 W, 4 cycles of 5 seconds with 20-second intervals. A 200 micrometer fiber is placed 1 mm short of the working length and moved in a slow helical motion from apical to coronal at about 2 mm per second without touching the canal walls. The canal is irrigated with 5 mL sterile saline after each cycle.

Single session of transmucosal photobiomodulation at the second visit, immediately after placement of the blood scaffold and coronal restoration. 810 nm diode laser, continuous wave, 200 mW, 8 mm tip in contact with the mucosa. Four sites per tooth (periapical and cervical regions on the buccal and lingual/palatal sides), 15 seconds and 3 J per site, for a total of 12 J per tooth.

Periapical lesion volume in cubic millimeters measured on cone-beam computed tomography (CBCT) scans (field of view 50 x 50 mm, isometric voxel size 0.125 mm) by a blinded outcome assessor. Change from baseline to 12 months is compared among the three groups.

Patient-reported pain on the Numeric Rating Scale from 0 (no pain) to 10 (worst pain imaginable), collected by telephone by a blinded study coordinator.

Whether any analgesic was taken since the previous assessment, with the number of doses and dose per intake, recorded at each telephone contact.

Presence or absence of tenderness to percussion, tenderness to palpation, swelling, and sinus tract, and need for additional intervention, assessed by clinical examination by a blinded examiner.