Bruxism, or repetitive jaw clenching, is a common cause of jaw pain, headaches and tooth wear. It is most common at night and affects approximately 10% of adults. There are four main muscles involved in chewing and clenching: the masseter, temporalis, and medial/lateral pterygoid. Bruxism is distinguished from chewing in that both jaw closing and opening muscles are active at the same time, rather than in sequence – so your mouth stays closed while your teeth and jaw take the brunt of the action.
In severe cases, bruxism can lead to dental fractures, bite changes, muscle pain, and headaches. In addition, repeated contraction of the muscles (particularly the masseter muscle) can lead to hypertrophy, or bulkiness, and widening/squaring in the appearance of the jaw. Based on weight, the masseter is already the strongest muscle in your body – and just like going to the gym, all of that extra exercise makes it even larger and stronger.
Many patients do report some improvement in tooth pain when they wear a night guard/dental splint to sleep, however available data indicates that these devices don’t actually reduce the frequency of clenching. Rather, they simply guard teeth from being ground down or cracked, while the masseter and temporalis still do their nightly reps.
This is where neuromodulators can be beneficial to patients who still wake up with jaw or dental discomfort in the morning, or have headaches due to bruxism. As neuromodulators reduce the ability of muscles to fire and contract, injecting the masseter muscle weakens it and decreases pain from bruxism at the source. As the strongest muscle in the body, volume-wise, there is still plenty of strength to talk and chew. As the muscle isn’t exercised as much, it loses some bulk, and therefore this treatment can be used to slenderize the lower face.
No medical procedure is risk-free, and while neuromodulator injections are low risk, it is important to see an experienced and educated practitioner for these treatments. The rizorius muscle attaches to the masseter muscle, and if injections are placed improperly or the medication diffuses into the rizorius, this treatment could lead to an asymmetric smile. While this would wear off at the 3-5 month mark, it is a known temporary and largely avoidable risk. This treatment usually requires 20- 30 units per side in women, or 30-45 units per side in men, every 3-5 months. As the masseter becomes more normal-sized with consecutive treatments, many patients find that they can space their injections out further than that after 1-1.5 years. If you have painful clenching and find that a night-guard isn’t cutting it, talk to your provider about neuromodulator treatment as a possible option.