Photobiomodulation therapy assisted orthodontic tooth movement: potential implications, challenges, and new perspectives

Abstract

Over the past decade, dramatic progress has been made in dental research areas involving laser therapy. The photobiomodulatory effect of laser light regulates the behavior of periodontal tissues and promotes damaged tissues to heal faster. Additionally, photobiomodulation therapy (PBMT), a non-invasive treatment, when applied in orthodontics, contributes to alleviating pain and reducing inflammation induced by orthodontic forces, along with improving tissue healing processes. Moreover, PBMT is attracting more attention as a possible approach to prevent the incidence of orthodontically induced inflammatory root resorption (OIIRR) during orthodontic treatment (OT) due to its capacity to modulate inflammatory, apoptotic, and anti-antioxidant responses. However, a systematic review revealed that PBMT has only a moderate grade of evidence-based effectiveness during orthodontic tooth movement (OTM) in relation to OIIRR, casting doubt on its beneficial effects. In PBMT-assisted orthodontics, delivering sufficient energy to the tooth root to achieve optimal stimulation is challenging due to the exponential attenuation of light penetration in periodontal tissues. The penetration of light to the root surface is another crucial unknown factor. Both the penetration depth and distribution of light in periodontal tissues are unknown. Thus, advanced approaches specific to orthodontic application of PBMT need to be established to overcome these limitations. This review explores possibilities for improving the application and effectiveness of PBMT during OTM. The aim was to investigate the current evidence related to the underlying mechanisms of action of PBMT on various periodontal tissues and cells, with a special focus on immunomodulatory effects during OTM.

Keywords: Immunorthodontics; Low-intensity laser therapy (LILT); Low-level laser therapy (LLLT); Orthodontic tooth movement; Orthodontics; Photobiomodulation therapy.

Fig. 1. Mechanisms underlying photobiomodulation (PBM) at the cellular and molecular levels. NIR: near infra-red; NO: nitric oxide; ROS: reactive oxygen species; CCO: cytochrome c oxidase; ATP: adenosine triphosphate; cAMP: adenosine 3',5'-cyclic-monophosphate; Akt: protein kinase B; GSK-3β: glycogen synthase kinase-3β; NF-κB: nuclear factor-κB; RANKL: receptor activator of NF-κB ligand; HIF-1α: hypoxia-inducible factor-1α; ERK: extracellular signal-regulated kinase; PPAR: peroxisome proliferator-activated receptor; mTOR: mammalian target of rapamycin; RUNX-2: Runt-related transcription factor 2.

Fig. 2. Therapeutic effects in photobiomodulation therapy (PBMT)-assisted orthodontics are multifactorial, with positive reactions in blood vessels, mineralized tissues, non-mineralized tissues, nervous system, and immune system. OTM: orthodontic tooth movement; TMD: temporomandibular disorder.

Fig. 3. Different regions of interest for light delivery to achieve photobiomodulation therapy (PBMT). The core concern is that the real energy density and penetration depth required for the light to reach the tooth root are currently unknown.