Involuntary masseter muscle activity—unnecessary motion of the muscles normally used for chewing—may be linked to periodontitis, according to new research from Japan published in Archives of Oral Biology.
Scientists have long investigated the relationship between periodontitis and the activity of the masseter muscles—the main muscles involved in the process of chewing, but it has remained unclear whether involuntary teeth grinding and jaw clenching, a condition known as bruxism, is related to periodontitis and its development.
Now, researchers from Okayama University 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.
Since bruxism not only occurs when a person is awake, but also when sleeping, the researchers made sure to design their study so that it provided information on masseter muscle activity during both the day and night.
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.
Participants of the study had to maintain a diary noting their activities including eating meals, which helped the researchers analyse the data and filter out muscular activity not coming from involuntary teeth grinding. Teeth movement due to speech was also filtered out by monitoring voice activity by a microphone attached to the electrodes.
The research team found that there were differences in masseter muscle activity between both groups, specifically the accumulated duration of non-functional (i.e. not related to eating or talking) high-intensity muscle motion was significantly longer for the participants in the MSP group. The finding applied to both awake and asleep regimes.
The scientists concluded that “masseter muscle activity might be related to the severity of periodontitis”, but they stressed that causation—bruxism leading to periodontitis—could not be concluded from the study.