RESUMO
Effects of sound generated by a dental turbine and a small stream (murmur) and the effects of no sound (null, control) on heart rate, systolic and diastolic blood pressure, and hemodynamic changes (oxygenated, deoxygenated, and total hemoglobin concentrations) in the frontal cortex were measured in 18 young volunteers. Questionnaires completed by the volunteers were also evaluated. Near-infrared spectroscopy and the Finapres technique were employed to measure hemodynamic and vascular responses, respectively. The subjects assessed the murmur, null, and turbine sounds as "pleasant," "natural," and "unpleasant," respectively. Blood pressures changed in response to the murmur, null, and turbine sound stimuli as expected: lower than the control level, unchanged, and higher than the control level, respectively. Mean blood pressure values tended to increase gradually over the recording time even during the null sound stimulation, possibly because of the recording environment. Oxygenated hemoglobin concentrations decreased drastically in response to the dental turbine sound, while deoxygenated hemoglobin concentrations remained unchanged and thus total hemoglobin concentrations decreased (due to the decreased oxygenated hemoglobin concentrations). Hemodynamic responses to the murmuring sound and the null sound were slight or unchanged, respectively. Surprisingly, heart rate measurements remained fairly stable in response to the stimulatory noises. In conclusion, we demonstrate here that sound generated by a dental turbine may affect cerebral blood flow and metabolism as well as autonomic responses.
