Optimization of a Photobiomodulation Protocol to Improve the Cell Viability, Proliferation and Protein Expression in Osteoblasts and Periodontal Ligament Fibroblasts for Accelerated Orthodontic Treatment

Abstract

Numerous pieces of evidence have supported the therapeutic potential of photobiomodulation (PBM) to modulate bone remodeling on mechanically stimulated teeth, proving PBM’s ability to be used as a coadjuvant treatment to accelerate orthodontic tooth movement (OTM). However, there are still uncertainty and discourse around the optimal PBM protocols, which hampers its optimal and consolidated clinical applicability. Given the differential expression and metabolic patterns exhibited in the tension and compression sides of orthodontically stressed teeth, it is plausible that different types of irradiation may be applied to each side of the teeth. In this sense, this study aimed to design and implement an optimization protocol to find the most appropriate PBM parameters to stimulate specific bone turnover processes. To this end, three levels of wavelength (655, 810 and 940 nm), two power densities (5 and 10 mW/cm2) and two regimens of single and multiple sessions within three consecutive days were tested. The biological response of osteoblasts and periodontal ligament (PDL) fibroblasts was addressed by monitoring the PBM’s impact on the cellular metabolic activity, as well as on key bone remodeling mediators, including alkaline phosphatase (ALP), osteoprotegerin (OPG) and receptor activator of nuclear factor κ-B ligand (RANK-L), each day. The results suggest that daily irradiation of 655 nm delivered at 10 mW/cm2, as well as 810 and 940 nm light at 5 mW/cm2, lead to an increase in ALP and OPG, potentiating bone formation. In addition, irradiation of 810 nm at 5 mW/cm2 delivered for two consecutive days and suspended by the third day promotes a downregulation of OPG expression and a slight non-significant increase in RANK-L expression, being suitable to stimulate bone resorption. Future studies in animal models may clarify the impact of PBM on bone formation and resorption mediators for longer periods and address the possibility of testing different stimulation periodicities. The present in vitro study offers valuable insights into the effectiveness of specific PBM protocols to promote osteogenic and osteoclastogenesis responses and therefore its potential to stimulate bone formation on the tension side and bone resorption on the compression side of orthodontically stressed teeth.

Photobiomodulation in Orthodontics: Mechanisms and Clinical Efficacy for Faster Tooth Movement

“…Gonçalves et al [24], alongside the study by Zhong et al [25], extensively explored the potential of PBM in enhancing orthodontic treatments. Gonçalves et al [24] focused on identifying the most effective PBM parameters, i.e., wavelengths (655, 810, and 940 nm), power densities (5 and 10 mW/cm 2 ), and treatment schedules, to modulate key bone remodeling mediators such as alkaline phosphatase, osteoprotegerin, and RANKL.…”

“…Gonçalves et al [24], alongside the study by Zhong et al [25], extensively explored the potential of PBM in enhancing orthodontic treatments. Gonçalves et al [24] focused on identifying the most effective PBM parameters, i.e., wavelengths (655, 810, and 940 nm), power densities (5 and 10 mW/cm 2 ), and treatment schedules, to modulate key bone remodeling mediators such as alkaline phosphatase, osteoprotegerin, and RANKL. Their findings highlighted that specific PBM settings could significantly influence bone formation or resorption, offering crucial insights for orthodontic treatment optimization through targeted bone turnover stimulation.…”

“…Unlike traditional orthodontic methods, PBM does not result in tissue damage, infection, blood loss, or discomfort, providing relief from these conditions instead [38][39][40][41]. Furthermore, its capacity to promote tissue healing, angiogenesis, bone remodeling, and accelerated tooth movement underscores its value as an adjunctive therapy in orthodontics [24,25].…”

“…Moreover, the effective utilization of PBM devices requires specific clinician training to prevent potential misuse or excessive use, which could lead to tissue damage. Another significant barrier to the widespread adoption of PBM is the cost of laser equipment, which, along with the need for intensive safety training, may limit accessibility for some practices and patients [24,25,[38][39][40][41][42][43][44][45][46].…”