Effects of sounds generated by a dental turbine and a stream on regional cerebral blood flow and cardiovascular responses

Abstract

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.

Physiological Effects of Shinrin-yoku (Taking in the Atmosphere of the Forest) in an Old-Growth Broadleaf Forest in Yamagata Prefecture, Japan

“…However, in our previous studies, as mentioned before (Miyazaki et al, 1999;Mishima et al, 2004), changes in physiological parameters by the inhalation of wood odor or the sound of murmuring water were observed within 60 to 90 seconds. Though these were the results of laboratory experiments, it can be expected that the impacts of "Shinrin-yoku" on physiological response would be obtained in a shorter time.…”

“…The authors have tried to examine the pleasant feelings that natural objects induce in humans by conducting physiological investigations. From studies dealing with the five senses separately, we have clarified that the smell of Japanese cedar wood lowered blood pressure and regional cerebral blood flow in the prefrontal area (Miyazaki et al, 1999), and the sound of murmuring water lowered blood pressure (Mishima et al, 2004). As Frumkin (2001) showed that a deep-seated connection between the natural world and humans was unsurprising from an evolutionary perspective, we assume that human physiological functions have had to adapt to the natural environment; thus, it is somehow a stressor to live in modern "artificial" society.…”

Trends in research related to “Shinrin-yoku” (taking in the forest atmosphere or forest bathing) in Japan

“…Mishima et al [37] compared the changes in brain activity and systolic blood pressure caused while listening to the sound of a turbine (dental implement), representing an artificial sound, or to a stream, representing a natural sound. No sound was introduced in the control session, i.e., the subjects heard no sound.…”

Difference in physiological responses to sound stimulation in subjects with and without fear of dental treatments

“…4 Among the traumatic factors that may explain fears of dentistry are odors 5 and sounds. 6 In addition, Kleinknecht et al 7 showed that the sources of fear during dental treatment include the anesthetic needle and drill. Psychological trauma resulting from experiences may negatively infl uence patient perception during future treatments.…”

“…In a study by Mishima et al, 6 the effects of sound generated by a dental turbine 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 young volunteers. NIRS and the Finapres technique were used to measure hemodynamic and cardiovascular responses, respectively.…”