Low-Level Laser Effects on Simulated Orthodontic Tension Side Periodontal Ligament Cells

Abstract

The purpose of this study was to analyze proliferation, inflammation, and osteogenic effects on periodontal ligament (PDL) cells after low-level laser therapy (LLLT) under simulated orthodontic tension conditions. Low-level lasers affect fibroblast proliferation and collagen synthesis and reduce inflammation. Few studies have focused on the LLLT changes in the PDL caused by moving teeth. A human PDL cell line was cultured in a -100 kPa tension incubator. The PDL cells were treated with a 670 nm low-level diode laser, output power of 500 mW (continuous wave modus) for 2.5 or 5 sec, spot area 0.25 cm(2), corresponding to 1.25 and 2.5 J at an energy density of 5 or 10 J/cm(2), respectively. PDL cell viability was assayed by detecting the ability of the cells to cleave tetrazolium salt to formazan dye. Inflammation and osteogenic markers were analyzed by Western blot analysis. PDL cell viablity increased in the experimental group, based on the ability of the cells to cleave tetrazolium salt at day 7 (p<0.05). The experimental group showed no difference in PDL cellular morphology compared with the control group. The inflammation markers inducible NO synthase (iNOS), cyclooxygenase (COX)-2 and interleukin (IL)-1 showed stronger expression in 5 and 10 J/cm(2) therapy at days 1 and 5, but decreased in expression at day 7. The osteogenic marker osteocalcin (OC) expression level was significantly higher at day 7 (p<0.05) than in the control cells. LLLT significantly increased PDL cell proliferation, decreased PDL cell inflammation, and increased PDL OC activity under the tension conditions used in this study.