In ancient societies most tooth wear was linked to a coarser diet. Today most tooth wear is linked to bruxism. More than 42% of US population has reported some sort of bruxism in their adult life, 16% associated with sleep and 24% associated with day bruxism. The main contributors to bruxism are seen to be the over activation of the master muscle, temporalis muscle, and the medial pterygoid muscle, accounting for 43%, 36% and 21% of jaw closure force, respectively. Not only is bruxism inherently linked to facial pain and disruption of function, but also it accounts for significant implant and prosthodontics treatment failures.
The botulinum neurotoxin Type A (BTA) has been widely used in medicine for decades, treating spasticity of juvenile cerebral palsy, spasticity due to stroke, chronic migraines and hyperhidrosis in the axillary region. BTA is produced by the Clostridium botulinum bacteria. BTA’s main mode action is the inhibition of release of Acetylcholine in the neuromuscular junction, therefore inactivating motor nerve filaments. Although there are many different types of botulinum neurotoxins, the most commonly used is BTA due to is prolonged duration of action – reaching maximum effect in 6 weeks, after which its effects wear off at about 12 weeks.
Agren et al. completed a systematic review of the effects of 200 botulinum toxin applications, involving 680 patients, looking for any significant reduction in bruxism in terms of episodes and/or force.
Changes in Muscle activation
The majority of the studies analyzed treated both the masseter and the temporalis muscle bilaterally with BTA injections. Electromyography (EMG) values of the muscles at rest and at clenching were measured, showing reductions in EMG activity in both the masseter and the temporalis muscle at 14 days following injection, however showed no significant difference at 28 days following injection.
Changes in the Number of Episodes of bruxism
Measuring EMG levels during sleep showed reduction in the number of episodes of bruxism when treated with BTA in the masseter and temporalis muscle.
Changes in Muscular force produced
BTA treatment showed a significant decrease in bite force for up to 3 months following treatment.
From the studies analyzed, BTA shows promise in decreasing the force and number of episodes of bruxism, mainly in the short term. More studies have to be done measuring long-term effects, more than 3 months.