Bruxism, or tooth grinding, may occur for a variety of reasons, some of which include poor temporal mandibular joint formation or alignment, ear infection, gum infection, tooth disease, tooth eruption, sinus infection, pain any where in the body, muscle weakness or abnormally increased muscle tone. The focus of this article is bruxism due to muscle weakness or abnormally increased muscle tone.
Consider the muscle sling which supports the alignment and movement of the lower jaw. It is made up of muscles in the posterior cheeks, the muscles of the tongue, the soft palate, and muscles on the side of the head. (if needed, an illustration of these muscle areas could be included) In a twenty-four hour period, the teeth actually touch an average of less than ten minutes, the time the teeth come into contact during chewing, excluding recreational chewing on gum. The majority of the day and night, the lower jaw is held in a position approximating closed, usually less than 1/4 inch apart from the teeth of the upper jaw. To maintain this position, the muscles supporting the jaw must be strong enough to withstand the constant force of gravity, pulling the jaw down. If the muscles are weak, as is the case with both low tone and high tone muscles, there are fewer options for jaw alignment and movement. There are two options: opened, or closed. As soon as the upper teeth come into direct contact with the lower teeth, a reflexive response of subtle shifting across the dental surfaces occurs, resulting in bruxism.
To determine the muscle areas involved, a baseline of the components of muscle movement must be determined. These components include: response to pressure and movement, range of movement, variety of movement, strength of movement, and control of movement. The areas assessed include the lips, cheeks, jaw and tongue. Observation of the face at rest, and during activities such as eating, drinking, talking, and during change in facial expression are important. The structures of the face and mouth should be inspected visually for alignment and symmetry.
In addition to observation, the lips, cheeks, tongue and jaw can be manipulated manually, using the Beckman Oral Motor protocol, to add data regarding the components of movement listed above. This is especially important if the individual is nonverbal, on nonoral intake, or cannot follow commands. Findings from this baseline will yield data critical to the design of an effective intervention program. Interventions dependent on the individual maintaining conscious control of the bruxism usually result in limited success. The small reflexive muscular adjustments necessary to maintain the jaw in alignment and approximating closed are not mediated cognitively. That means that if each of us had to constantly be aware of and adjust the alignment of the lower jaw, we would have our conscious brain circuitry so tied up, it would be difficult for us to accomplish any other task during waking hours, and it would be impossible to do when asleep. Internal jaw stability is the key to functional movement and alignment of the lower jaw.
Also note that although squeezing the outer face may result in brief cessation of the bruxism, often due to the sensation of pain, that cessation can not be internalized until the muscles responsible for the task have adequate strength to do the job. Interventions which provide opportunity for active muscle contraction against resistance have resulted in increased strength for the muscles of the jaw, cheek, intrinsic tongue muscles and soft palate with a significant decrease in bruxism for many individuals with low muscle tone. For some individuals, the bruxism may still occur, especially during times of physical stress, illness, or change in motor skills - either gross motor or fine motor. The overall incidence is reduced to a level that allows for a variety of jaw movements through out the day, with better jaw alignment at night.
Additional interventions may be necessary, such as night splints for the mouth. The focus of the oral motor interventions is to maximize jaw function in balance with the other structures and muscles of the face.