Symptoms and Physiological Responses to Prolonged, Repeated, Low‐Level Tooth Clenching in Humans

Background The traditional view contends bruxism, such as tooth grinding/clenching, is part of the etiology of temporomandibular disorders ( TMD ) including some subtypes of headaches. The purpose of this study is to investigate if a low‐level but long‐lasting tooth‐clenching task initiates TMD symptoms/signs. Methods Eighteen healthy participants (mean age ±  SD , 24.0 ± 4.3 years) performed and repeated an experimental 2‐hour tooth‐clenching task at 10% maximal voluntary occlusal bite force at incisors (11.1 ± 4.6  N ) for three consecutive days ( D ays 1‐3). Pain and cardiovascular parameters were estimated during the experiment. Results The task evoked pain in the masseter/temporalis muscles and temporomandibular joint after 40.0 ± 18.0 minutes with a peak intensity of 1.6 ± 0.4 on 0‐10 numerical rating scale ( NRS ) after 105.0 ± 5.0 minutes ( D ay 1). On D ay 2 and D ay 3, pain had disappeared but the tasks, again, evoked pain with similar intensities. The onset and peak levels of pain were not different between the experimental days ( P  = .977). However, the area under the curve of pain NRS in the masseter on D ay 2 and D ay 3 were smaller than that on D ay 1 ( P  = .006). Cardiovascular parameters changed during the task but not during the days. Conclusions Prolonged, low‐level tooth clenching evoked short‐lived pain like TMD . This intervention study proposes that tooth clenching alone is insufficient to initiate longer lasting and self‐perpetuating symptoms of TMD , which may require other risk factors.