Methods: An interventional, blind, longitudinal twelve month study was carried out; sample size consisted of forty patients with a diagnosis of myofascial pain associated with severe bruxism on whom botulinum toxin type A was applied; patients were evaluated prior to application at 3, 6, 9 and 12 months and variables including age, sex, spontaneous and provoked pain, mandibular opening, mandibular deviation and presence of joint noises were considered.
Results: 77.7% of the sample consisted of women with an average age of 33.56 ± 12.17 years old. 80.5% reported improvement for both spontaneous and provoked pain during treatment, out of which 51.7% presented increased pain 3 and 6 months, 13.7% increased pain between 6 and 9 months and 3.4% between 9 and 12 months.
Conclusions: Application of botulinum toxin type A is a safe and effective treatment for myofascial pain associated with severe bruxism and its therapeutic effect requires new applications every three to six months for its effectiveness to persist.