Table 4 Laser wavelength and activation protocols of included studies.

Alves-Silva (2022)

660 nm

The treatment involved activating 3 mL of 0.005% methylene blue with a 660 nm red gallium aluminum arsenide diode laser at 100 mW for 90 s after a 3-min pre-irradiation period. The application consisted of a 15-sec static exposure at the canal apex, then helical movements toward the crown, delivering a total of 9 J and an energy density of 320 J/cm².

Coelho (2019)

660 nm

The laser tip, covered in aluminum foil, employed a size 25, 0.04 taper optical fiber, which was positioned to the working length. The laser settings were 660 nm and 100 mW, delivering 18 J of energy and an energy density of 600 J/cm² over a 3 min duration, with the tip being moved gently in a vertical direction.

Erkan (2022)

2940 nm

For the PIPS group, an Er: YAG laser with a 600 μm, 9 mm long PIPS tip was set to a 2,940 nm wavelength, delivering 20 mJ per pulse at 15 Hz and 0.3 W, with a 50 µs pulse frequency. The tip was held stationary in the access cavity while activating a 3% NaOCl solution in three 20-sec intervals, followed by the same activation sequence for 2 ml of 17% EDTA solution.

The SWEEPS procedure utilized an Er: YAG laser source (2,940 nm) with the SWEEPS fiber tip in ultra-short dual pulse mode (25 µs, Auto SWEEPS mode). Set at 20 mJ per pulse, 15 Hz, and 0.3 W power with a 50 µs pulse frequency, the tip was held steady in the access cavity. Activation followed the same protocol and used identical irrigation solutions as in the PIPS group.

Kaplan (2021)

980 nm

The laser was programmed to pulsed mode, outputting 2.4 W with 12 J delivered per cycle at a 20 µs pulse duration. The treatment protocol was 10 s of irradiation followed by a 10-sec rest, comprising one cycle, and repeated four times per canal. The average power was 1.2 W, with a power density of 3822 W/cm² at 50 Hz frequency, using a 25 mm fiber optic tip positioned at the working length.

Koba (1999)

1064 nm

Using a 320 μm flexible optical fiber, the laser was set to a power of 1 W and a frequency of 15 pulses per second, with 66 mJ per pulse and a pulse duration of 150 picoseconds for a duration of 1 s. The fiber tip was placed in contact with the root canal’s apical seat during laser activation.

Liapis (2021)

2940 nm

Using a dental handpiece (H14, Fotona) paired with a 400 μm PIPS tip and both water and air off, the laser was set to 20 mJ pulse energy, 15 Hz frequency, and 50 µs pulse length. The tip was positioned above the canal entrance, and each canal received two 30-sec activation cycles with a 2 mL 3% NaOCl rinse in between. Throughout, the pulp chamber was kept filled with 3% NaOCl.

Lopes (2018)

808 nm

The laser was applied perpendicularly to the gum, at four points per tooth—two buccal, two lingual, aligned with the root apices of mandibular molars. It was set at 0.10 W, delivering 2.5 J per point over 25 Sect. (100 s total per tooth), with an energy density of 90 J/cm² per point, totaling 360 J/cm² per tooth.

Morsy (2018)

980 nm

A 200 μm optical fiber laser (Lite medics, Italy) set to 1.2 W in pulsed mode was employed. The protocol involved 5 s of irradiation followed by a 10 s pause, constituting one cycle, repeated four times per tooth. The fiber tip was positioned 1 mm from the apex, then activated and drawn coronally at approximately 2 mm/s in a helical pattern to irradiate the canal walls.

Nabi (2018)

905 nm

875 nm

The laser tip was applied perpendicularly in contact mode to the periapical regions buccally and lingually. The duration was 3 min, with powers set to 12–16 mW for 875 nm broadband infrared (IR) irradiation at 60 mW, and 640 nm for visible red irradiation at 7 mW.

Naseri (2020)

808 nm

The BI group was subjected to 80 s of laser irradiation on the buccal surface, while the BLI group received 80 s each on both buccal and lingual surfaces. A 100-mW laser with a 600 μm fiber diameter was utilized for the procedure.

Tunc (2021)

1064 nm

940 nm

The Nd: YAG laser used a 200 μm fiber at 1 W output, with an energy density of 100 mJ/s and a 15 Hz frequency. The fiber tip was inserted into the root canal to 1 mm shy of the working length and retracted in a spiral motion with the laser active for 5 s. This step was repeated four times with a 20 s rest between each.

The laser output was set to 1 W in CW mode with an energy density of 100 mJ/pulse at 15 Hz. A 200 μm Biolase optical fiber reached the working length, irradiating the root canal from the apex to the coronal end at 2 mm/s in a circular motion for complete canal wall contact. This was repeated four times with 20-sec intervals.

Vilas-boas (2021)

660 nm

In the PG group, the canals were treated with 150 µM Methylene Blue (MB), left in place for 2 min. A Laser Duo (MMOptics, São Carlos, Brazil) delivering 100 mW and 600 J/cm² was then applied for 3 min in each canal, imparting a total of 18 J of energy. The laser was administered via an optical fiber sized 25.04, positioned up to the working length (WL).

Yıldız (2018)

970 nm

A 200-µm optical fiber with a bleaching tip was positioned 10 mm from the periapical tissue, activated at 0.5 W and 10 Hz with a power density of ~ 286 W/cm². The periapical tissues of the mesial and distal root apices were irradiated for 30 s each.

Arslan (2017)

970 nm

The mesial and distal root apices were each irradiated for 30 s at 0.5 W and 10 Hz, yielding a power density of ~ 2.86 W/cm². A 200-µm optical fiber with a bleaching tip was utilized, positioned roughly 10 mm from the tissue for the application.

Asnaashari

(2017)

808 nm

Laser treatment was administered using a single dose at an 808 nm wavelength with a power setting of 100 mW, utilizing a 600 μm fiber, delivering a dose of 70 J/cm² over a duration of 80 s.

Fazlyab (2021)

980 nm

The laser was calibrated to an energy density of 6.89 W/cm² and power of 0.5 W, using a 10 mm diameter tip for 15 s. It was directed at the soft tissue overlying the mesial and distal tooth apices from the buccal aspect, with the laser handpiece tip maintained around 10 mm away from the mucosa.

Genc Sen (2019)

940 nm

Laser energy was delivered via a 200-µm fiber tip at 1 W in continuous mode. The tip was placed at the working length and the canals were irradiated at a speed of 2 mm/s, employing circling movements from apical to coronal parts. This process was repeated four times per canal with 20-sec intervals between applications.