The effects of “Biostimulation” (low-level laser irradiation) on human osteoblast-like cell model

Low-level laser therapy (LLLT) is a well-established clinical tool used to treat pathological tissue conditions, inflammatory processes, and promote wound healing [1]. LLLT refers to the use of lasers emitting a wavelength ranging from 600 to 1100 nm with an output power within 1 to 500 mW. LLLT has been found to modulate various biological processes, such as collagen production [2], DNA synthesis, mitochondrial respiration, and ATP synthesis [3]. Various studies have demonstrated that LLLT promotes both repair and regeneration [4]. It has been shown that LLLT induces cell proliferation, promotes angiogenesis and allows the wound site to close more quickly [5]. With respect to bone, LLLT has been applied in several clinical situations, such as orthodontic treatment, alveolar repair after tooth extraction, bone fracture healing, and osteo-integration of dental implants as an adjuvant therapy [6]. In vitro laser irradiation improves proliferation and differentiation of human osteoblast cells and in vivo irradiation increases the functional attachment of biomaterial implants to bone [7]. Nevertheless, LLLT should be more thoroughly investigated before low level laser therapy can be considered as a potential tool for bone regeneration. Considering evidence that LLLT has a positive effect on bone healing, the aim of the present study was to investigate the in vitro effects of LLLI irradiation (LLLI) by an aluminum gallium indium phosphide (AlGaInP) semiconductor diode laser at a wavelength of 659 nm on the proliferation of a human osteoblast-like cells (Saos-2 cells). With this aim, it was decided to investigate the optimal stimulating parameters for Saos-2 proliferation, analyzing cell viability, cell phenotype by telomerase assay and cell morphology