The Dentist Magazine.

Possible link between excess chewing muscle activity and dental disease

Published: 9/12/2018 12:00:00 AM

Researchers at Okayama University have reported in Archives of Oral Biology that involuntary masseter muscle activity, unnecessary motion of the muscles normally used for chewing, may be linked to a common dental disease known as periodontitis.

Periodontitis is an infection of the gum, damaging jaw tissue and ultimately destroying the bone holding teeth in place, resulting in tooth loosening and loss. Medical researchers have been investigating the relationship between periodontitis and the activity of the masseter muscles, the main muscles involved in the process of chewing. Specifically, it has been unclear whether involuntary teeth grinding and jaw clenching, a condition known as bruxism, is related to periodontitis and its development. Now, Professor Shogo Minagi and Dr. Seiya Kato from Okayama University and colleagues have performed detailed measurements of masseter muscle activity in a group of people with various degrees of periodontal disease and found that non-functional teeth grinding might be related to the acuteness of periodontitis.

Bruxism not only occurs when a person is awake, but also when sleeping. Therefore, the researchers made sure to design the study so that it provides information on masseter muscle activity over a long-enough period (daytime followed by night-time). A group of 31 people was selected; 16 of them had no or mild periodontitis (the ‘NMP’ group), while 15 had moderate to severe periodontitis (the ‘MSP’ group).

Each individual was equipped with an ambulatory portable device measuring muscle activity via a technique known as surface electromyography. The technique involves placing electrodes on the skin lying over the muscle; muscular motion triggers an electrical signal which is recorded. Participants of the study had to maintain a diary noting their activities including eating meals, which helped the researchers with analysing the data and filtering out muscular activity not coming from involuntary teeth grinding. Teeth movement due to speech was filtered out by monitoring voice activity via a microphone attached to the electrodes.

Professor Minagi and colleagues found that there were differences in masseter muscle activity between the NMP and MSP groups. The accumulated duration of non-functional (not related to eating or talking) high-intensity muscle motion was significantly longer for the participants from the MSP group. The finding applies to both awake and asleep regimes. The scientists concluded that, “masseter muscle activity might be related to the severity of periodontitis”, but they stress that causation cannot be concluded from the study. They also point to limitations of their study, oral conditions like missing teeth or the use of removable partial dentures not being taken into account, and the limited capabilities of the ambulant surface electromyography setup.