Clear Aligners and Photobiomodulation: Critical Review of Clinical Evidence

Background/Objectives: Photobiomodulation (PBM) is a biologically plausible adjunct for modulating orthodontic tissue response, but its role in conventional clear aligner therapy remains uncertain. This narrative review summarises the mechanistic rationale and clinical evidence on PBM used with clear aligners, focusing on treatment efficiency, predictability, patient-centred outcomes, and biological safety. Methods: Scopus was searched using PBM/low-level laser terms combined with orthodontics and clear aligners. Titles and abstracts were screened for human studies evaluating PBM as an adjunct to conventional staged clear aligner therapy and reporting treatment duration or alignment efficiency, tracking/predictability (for example, additional aligners, refinements, or fit-related outcomes), pain, or biological safety. Eight aligner-based clinical studies formed the core set. Results: The included studies comprised case reports, retrospective cohorts, pilot investigations, and one historical prospective nonrandomized comparison. Most evaluated short daily sessions of home-use near-infrared LED PBM, while some used external laser-based or combined adjunct protocols. Some studies reported shorter treatment duration, faster alignment, or fewer finishing aligners in PBM users, but these findings were difficult to attribute to PBM alone because altered tray-change intervals and close monitoring were common co-interventions. Aligner-specific pain outcomes were inconsistently reported. Limited safety data, based mainly on one retrospective pilot cohort assessing anterior teeth, found no statistically significant difference in root-volume change between PBM users and controls. Conclusions: PBM has been investigated as a potential adjunct in clear aligner orthodontics, but the available evidence remains preliminary, heterogeneous, and largely non-randomised. No high-quality randomized clinical evidence currently supports the clinical effectiveness or routine use of PBM in clear aligner orthodontics. At present, PBM should be regarded as an investigational adjunct rather than an established clinical recommendation, pending larger and better-designed trials with standardised device-specific protocols, objective adherence measures, movement-specific analyses, and longer follow-up for safety and patient benefit.