Reproducibility of estimation of blood flow in the human masseter muscle from measurements of 133Xe clearance

Deep and superficial masseter muscle blood flow in women

PURPOSE

Although changes in blood perfusion have been described as being associated with temporomandibular disorder (TMD) myofascial pain, very little is known about blood flow levels in the deep and superficial masseter muscle. This study investigated blood flow in deep and superficial sites of six healthy female participants at baseline and during intermittent and continuous biting exercises and recovery.

MATERIALS AND METHODS

Blood flow was monitored unilaterally using a single-fiber probe laser Doppler flowmeter. The blood flow was continuously monitored at baseline and during two biting exercises: (a) intermittent at 25%, 50%, and 100% maximum voluntary bite force for 30 seconds each followed by 90 seconds rest between each biting level and (b) continuous biting at similar maximum voluntary bite force levels followed by 90 seconds rest.

RESULTS

There was significantly higher blood flow in the deep sites compared to the superficial sites (p < 0.001) and a significant increase in blood flow during biting compared to baseline (p < 0.001). There were no significant changes in blood flow among the three levels of biting, between the intermittent and continuous exercises, or from baseline blood flow compared to recovery.

CONCLUSIONS

This study showed regional differences in masseter muscle blood flow, perhaps related to differences in muscle fiber type and pattern of muscle fiber recruitment.

Report of the Committee on Scientific Investigation of the American Academy of Restorative Dentistry

The growth in the dental literature continues to escalate, as evidenced by the publication of at least 326 new books in 1988 and 1989 and more than 20 new journals in 1989. There still appears to be undue emphasis on quantity instead of quality of research. This proliferation in the literature poses ever increasing difficulties to this Committee in filtering out the articles that are of particular interest to the members of the Academy and identifying those that are most likely to have a major impact on dental practice and service. The subjects covered include periodontics, caries and preventive dentistry, craniomandibular disorders, occlusion, pulp biology, ceramics, and restorative dental materials.

Comparison of 133Xe clearance and laser Doppler flowmetry in assessment of blood flow changes in human masseter muscle induced by isometric contraction

Changes induced by 30 s of isometric contraction at 10% and 50% of the maximum voluntary contraction were assessed in 10 healthy subjects; there was a median increase of 1.8 and 0.3 times in 133Xe clearance and 5.3 and 2.7 times in laser Doppler flowmetry. In the first minute after 10% maximum voluntary contraction, 133Xe clearance increased 12.1 times in relation to the initial resting level, and flowmetry values decreased to become 3.5 times higher than the basal flow; corresponding values after 50% maximum voluntary contraction were 24.3 times and 3.7 times. From the second minute after contraction, there was a rapid decrease in 133Xe clearance and a slow decrease in flowmetry values. Five minutes after biting at 10% maximum voluntary contraction, both methods showed a total net increase of about 15 times; after biting at 50% maximum voluntary contraction the corresponding values were 38 and 23 times. Thus laser Doppler flowmetry can be used to assess changes in blood flow in the masseter; it registers a greater increase in flow during isometric contraction than does 133Xe clearance. The significant difference between methods immediately after either chosen level of contraction disappears when the total net post-contraction hyperaemia is assessed over a period of 2 and 5 min, respectively.