Purpose: It has been reported that low-level semiconductor diode lasers could enhance the wound healing process. The periodontal ligament is crucial for maintaining the tooth and surrounding tissues in periodontal wound healing. While low-level semiconductor diode lasers have been used in low-level laser therapy, there have been few reports on their effects on periodontal ligament fibroblasts (PDLFs). We performed this study to investigate the biological effects of semiconductor diode lasers on human PDLFs. Methods: Human PDLFs were cultured and irradiated with a gallium-aluminum-arsenate (GaAlAs) semiconductor diode laser of which the wavelength was 810 nm. The power output was fixed at 500 mW in the continuous wave mode with various energy fluencies, which were 1.97, 3.94, and 5.91 $J/cm^2$. A culture of PDLFs without laser irradiation was regarded as a control. Then, cells were additionally incubated in 72 hours for MTS assay and an alkaline phosphatase (ALPase) activity test. At 48 hours post-laser irradiation, western blot analysis was performed to determine extracellular signal-regulated kinase (ERK) activity. ANOVA was used to assess the significance level of the differences among groups (P<0.05). Results: At all energy fluencies of laser irradiation, PDLFs proliferation gradually increased for 72 hours without any significant differences compared with the control over the entire period taken together. However, an increment of cell proliferation significantly greater than in the control occurred between 24 and 48 hours at laser irradiation settings of 1.97 and 3.94 $J/cm^2$ (P<0.05). The highest ALPase activity was found at 48 and 72 hours post-laser irradiation with 3.94 $J/cm^2$ energy fluency (P<0.05). The phosphorylated ERK level was more prominent at 3.94 $J/cm^2$ energy fluency than in the control. Conclusions: The present study demonstrated that the GaAlAs semiconductor diode laser promoted proliferation and differentiation of human PDLFs.
Pinfildi CE, Liebano RE, Hochman BS, Ferreira LM. Helium-neon laser in viability of random skin flap in rats. Lasers Surg Med 2005;37:74-7.
Isaka J, Ohazama A, Kobayashi M, Nagashima C, Takiguchi T, Kawasaki H, et al. Participation of periodontal ligament cells with regeneration of alveolar bone. J Periodontol 2001;72:314-23.
Lekic P, McCulloch CA. Periodontal ligament cell population: the central role of fibroblasts in creating a unique tissue. Anat Rec 1996;245:327-41.
Kreisler M, Christoffers AB, Willershausen B, d'Hoedt B. Effect of low-level GaAlAs laser irradiation on the proliferation rate of human periodontal ligament fibroblasts: an in vitro study. J Clin Periodontol 2003;30:353-8.
Kreisler M, Meyer C, Stender E, Daublander M, Willershausen-Zonnchen B, d'Hoedt B. Effect of diode laser irradiation on the attachment rate of periodontal ligament cells: an in vitro study. J Periodontol 2001;72:1312-7.
do Nascimento PM, Pinheiro AL, Salgado MA, Ramalho LM. A preliminary report on the effect of laser therapy on the healing of cutaneous surgical wounds as a consequence of an inversely proportional relationship between wave-length and intensity: histological study in rats. Photomed Laser Surg 2004;22:513-8.
Kreisler M, Christoffers AB, Al-Haj H, Willershausen B, d'Hoedt B. Low level 809-nm diode laser-induced in vitro stimulation of the proliferation of human gingival fibro-blasts. Lasers Surg Med 2002;30:365-9.
Pereira AN, Eduardo Cde P, Matson E, Marques MM. Effect of low-power laser irradiation on cell growth and pro-collagen synthesis of cultured fibroblasts. Lasers Surg Med 2002;31:263-7.
Shimizu N, Yamaguchi M, Goseki T, Shibata Y, Takiguchi H, Iwasawa T, et al. Inhibition of prostaglandin E2 and interleukin 1-beta production by low-power laser irradiation in stretched human periodontal ligament cells. J Dent Res 1995;74:1382-8.
Giannopoulou C, Cimasoni G. Functional characteristics of gingival and periodontal ligament fibroblasts. J Dent Res 1996;75:895-902.
Gumbiner BM. Cell adhesion: the molecular basis of tissue architecture and morphogenesis. Cell 1996;84:345-57.
Kim TI, Jang JH, Lee YM, Rhyu IC, Chung CP, Han SB, et al. Biomimetic approach on human periodontal ligament cells using synthetic oligopeptides. J Periodontol 2004;75:925-32.
Ozawa Y, Shimizu N, Kariya G, Abiko Y. Low-energy laser irradiation stimulates bone nodule formation at early stages of cell culture in rat calvarial cells. Bone 1998;22:347-54.
Kreisler M, Al Haj H, d'Hoedt B. Clinical efficacy of semi-conductor laser application as an adjunct to conventional scaling and root planing. Lasers Surg Med 2005;37:350-5.
Herascu N, Velciu B, Calin M, Savastru D, Talianu C. Lowlevel laser therapy (LLLT) efficacy in post-operative wounds. Photomed Laser Surg 2005;23:70-3.