Method: The study consisted of 30 patients from the Lar Escola São Francisco/Federal University of Sao Paulo, Brazil with CP, aged 10 to 12 years-old. Their masseter and temporal muscles were irradiated on the both sides for three consecutive weeks (three times in week one, twice in week two and once in week three), with an 808nm low intensity diode laser at 120 mW, 3J/cm2 (Twin Flex Evolution Laser MMO 808, São Paulo, Brazil), for 20 seconds per site. Mouth opening amplitude was measured by a caliper whose stems touched the upper and lower incisors and bite strength by a dynamometer (model DMD Kratos Equipments, São Paulo, Brazil). The measurements were recorded before and immediately after each laser irradiation during the three weeks of laser therapy and once a week for the following three weeks of clinical follow-up.
Result: Analysis of Variance and the Tukey test showed a significant improvement in mouth opening amplitude and a decrease in bite strength (p<0.001) following laser therapy, particularly in week one, though mean values remained the same for the three weeks of clinical follow-up. By week six, the measurements of bite strength (13.9±4.4) and mouth opening (25.7±6.5) returned to values similar to those obtained before the first laser irradiation (13.7±4.4) and (25.9±6.2), respectively.
Conclusion: The 808nm diode low intensity laser was shown to be effective as a therapeutic tool when used to increase mouth opening and decrease the muscle tonus of CP patients, although the mean values remained effective for a limited period.