Introduction: Bruxism (BRX) can be defined as clenching and/or grinding of the teeth in a particularly intense or involuntary way. It occurs interchangeably during sleep or while awake due to repeated contraction and/or hypertrophy of the masticatory muscles. Treatments are mainly intended to limit induced temporomandibular joint (TMJ) damage and are manifold: irreversible occlusion, bite splints, pharmacological and/or cognitive therapies. However, botulinum toxin type A (BoNT-A) is especially effective. The aim is to assess the attenuation or disappearance of BRX-related symptoms after injection of BoNT-A due to relaxation of the masticatory muscles (especially the masseter muscles). Materials and Method: this is a clinical, prospective and longitudinal study on 43 adult female patients aged between 24 and 67 (37.0 ± 9.6). It was carried out from September 2018 to October 2019. Assessment controls were performed before, two weeks and four months after the first treatment with BoNT-A, and two weeks and five months after the second treatment. Digital photographs were taken at each control visit, the Smith-Knight Tooth Wear Index was assessed and orthopantomography (OPG) was performed. Bigonial diameters were measured with a digital caliper. The masseter muscles were assessed bilaterally, at rest and during contraction, by ultrasound. Results: after BoNT-A treatment, 26% of patients were free of BRX, whereas considerable improvements were observed in the remaining 74%. Adverse effects were mild and of short duration.
Conclusion: BoNT-A treatment was able to prevent lesions on orofacial structures (teeth, jaw muscles, TMJ), and at the same time relieve pain and associated symptoms induced by repeated muscle contraction in BRX.

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