Effects of Experimental Tooth Clenching on Pain and Intramuscular Release of 5-HT and Glutamate in Patients with Myofascial TMD

It has been suggested that tooth clenching may be associated with local metabolic changes, and is a risk factor for myofascial temporomandibular disorders (M-TMD). This study investigated the effects of experimental tooth clenching on the levels of 5-HT, glutamate, pyruvate, and lactate, as well as on blood flow and pain intensity, in the masseter muscles of M-TMD patients. Fifteen patients with M-TMD and 15 healthy controls participated. Intramuscular microdialysis was done to collect 5-HT, glutamate, pyruvate, and lactate and to assess blood flow. Two hours after the insertion of a microdialysis catheter, participants performed a 20-min repetitive tooth clenching task (50% of maximal voluntary contraction). Pain intensity was measured throughout. A significant effect of group (P<0.01), but not of time, was observed on 5-HT levels, and blood flow. No significant effects of time or group occurred on glutamate, pyruvate, or lactate levels. Time and group had significant main effects on pain intensity (P<0.05, and P<0.001). No significant correlations were identified between: (i) 5-HT, glutamate, and pain intensity or between (ii) pyruvate, lactate, and blood flow. This experimental tooth clenching model increased jaw muscle pain levels in M-TMD patients and evoked low levels of jaw muscle pain in healthy controls. M-TMD patients had significantly higher levels of 5-HT than healthy controls and significantly lower blood flow. These two factors may facilitate the release of other algesic substances that may cause pain. Authors: Dawson A, Ghafouri B, Gerdle B, List T, Svensson P, Ernberg M. ;Full Source: The Clinical Journal of Pain. 2014 Sep 17. [fusion_builder_container hundred_percent="yes" overflow="visible"][fusion_builder_row][fusion_builder_column type="1_1" background_position="left top" background_color="" border_size="" border_color="" border_style="solid" spacing="yes" background_image="" background_repeat="no-repeat" padding="" margin_top="0px" margin_bottom="0px" class="" id="" animation_type="" animation_speed="0.3" animation_direction="left" hide_on_mobile="no" center_content="no" min_height="none"][Epub ahead of print] ;[/fusion_builder_column][/fusion_builder_row][/fusion_builder_container]