Photobiomodulation therapy （PBMT） has a therapeutic effect by increasing tissue cell activity while avoiding thermal damage to the tissue. Recently, the efficacy of PBMT for osteoarthritis （OA） has been reported. However, detailed molecular biological effects of PBMT on cartilage tissues and chondrocytes remain unclear. This paper introduces the in vivo and in vitro studies reported recently and discusses future prospects.

View full abstract

Introduction: It has been reported that low reactive level laser therapy （LLLT） by diode laser irradiation promotes wound healing, anti-inflammatory effect, analgesic effect and improvement of blood flow. However, details of the effects of LLLT on the proliferation and differentiation of periodontal ligament cells remain unclear. The aim of this study was to investigate the effects of diode laser LLLT irradiation on periodontal ligament tissue and to verify its applicability to periodontal tissue regeneration therapy.
Methods: Human teeth extracted for orthodontic treatments and periodontal ligament tissue fragments were scraped from the root surface of the tooth. The human periodontal ligament （PDL） cells were outgrowths from the tissue fragments, and were subcultivated for use in this study. Every 24 hours during the first 3 days from the start of culture, the PDL cells were exposed to defocus diode laser LLLT irradiation （40W, 50s, 200J） at a distance of 6.0cm from the cultured PDL cells, and the cells were sampled on days 4 and 6 from the start of culture. Expression of type 1 collagen, cementum protein 1 （CEMP1） and Ki67 expression were analyzed by real-tine quantitative polymerase chain reaction （PCR） on days 4 and 6 in this culture.
Results: In cultured PDL cells, LLLT irradiation by diode laser reduced the expression of type 1 collagen, CEMP1 and Ki67 mRNA compared with the control on day 4. However, LLLT irradiation by diode laser promoted the expression of CEMP1 and Ki67 on day 6, the expression of each being approximately 1.8 times and 3 times compared with the control.
Conclusion: These results suggest that LLLT by diode laser irradiation promotes the proliferation and differentiation of PDL cells.

View full abstract