CO2 low-level laser therapy has an early but not delayed pain effect during experimental tooth movement.

<bold>Objectives: </bold>To test the hypothesis that the use of low-level laser therapy (LLLT) reduces elevated pain by controlling the release of neurochemicals during orthodontic tooth movement.<bold>Setting and Sample Population: </bold>Department of Orthodontics and Dentofacial Orthopedics, Okayama University. Sixty-five Sprague Dawley rats were subjected to tooth movement and LLLT.<bold>Materials and Methods: </bold>Adult Sprague Dawley rats were used in this study. Groups included day 0 controls, irradiation only controls and with or without irradiation sacrificed at 1, 3, 5, 7 and 14 days after tooth movement (n=5 each, total n=65). Tooth movement was achieved by insertion of an elastic module between molar teeth. Immunohistochemistry for CD-11b, GFAP and c-fos in the brain stem was performed. Stains were quantified by constructing a three-dimensional image using IMARIS, and counted using NEURON TRACER and WinROOF software. Two-way ANOVA followed by a Tukey's post hoc test (P<.05) was used for statistical comparison between groups.<bold>Results: </bold>C-fos expression was significantly increased at one and three days after tooth movement. LLLT significantly diminished this increase in c-fos expression only at one day after tooth movement CD-b11 and GFAP expression also significantly increased after tooth movement. No significant change was observed for CD-11b and GFAP expression in the central nervous system upon LLLT.<bold>Conclusion: </bold>Low-level laser therapy may reduce early neurochemical markers but have no effect on delayed pain neurochemical markers after tooth movement. [ABSTRACT FROM AUTHOR]