Effects of the Pulse Frequency of Low-Level Laser Therapy on the Tooth Movement Speed of Rat Molars

Abstract

Objective: The purpose of this study was to compare the speed of the orthodontic tooth movement of rat molars under continuous wave (CW) and pulsed wave (PW) low-level laser therapy (LLLT). Background data: It remains unclear whether LLLT can increase the speed of tooth movement, and no consensus has been established regarding the appropriate parameters and experimental design of LLLT. Materials and methods: Orthodontic movement was induced in 40 rats with 10g coil springs. Rats were randomly assigned to five groups. In Group I, the maxillary left first molars were irradiated with CW by a gallium aluminum arsenide (GaAlAs) diode laser source (830 nm, 180 mW, 3.6 J/cm², and 0.9 W/cm² for 4 sec at three locations for 3 consecutive days). In Groups II, III, and IV, animals were irradiated with PW at 2, 4, and 8 Hz, respectively (50% duty cycle, average power of 90 mW, 3.6 J/cm², and 0.45 W/cm² for 8 sec at three locations for 3 consecutive days). Group V served as the control (no irradiation). The movement distance was measured on days 3, 7, and 14. Results: Although there were no significant differences among the irradiation groups, significant differences were found between the control and irradiation groups starting from day 3. Conclusions: The CW and PW treatments both led to faster orthodontic tooth movement compared with the control group.