The Use of Low-Dose Botulinum Toxin Injection Into the Masseter Muscle to Treat Sleep Bruxism

Evaluation of the Efficacy of Low-Dose Botulinum Toxin Injection Into the Masseter Muscle for the Treatment of Nocturnal Bruxism: A Randomized Controlled Clinical Trial

Botulinum toxin (BOTOX®) injections into the masseter muscle are an effective treatment for nocturnal bruxism, with several trials using various dosages of botulinum toxin for this purpose. The aim was to evaluate the effectiveness of injecting 10MU of botulinum toxin A (BTXA) into the masseter muscle to reduce nocturnal bruxism, the sample will randomly divided into 2 groups. In the injection group, Patients will inject with 10 MU of botulinum toxin type A (BOTOX® - Allergan Inc. - Dublin - Ireland) per side at two sites into the masseter muscle bilaterally. In this Placebo group, patients will prick twice at the inferior prominent part of the masseter muscle observed using the stinger pen used in the blood glucose meter. The evaluation will make by Electromyography (EMG) analysis, Visual Analogue Scale (VAS) values.

Nocturnal bruxism (NB) is a disorder of maxillomandibular activity characterized by nonfunctional grinding and clenching of teeth while sleeping. NB can cause teeth attrition, dental prostheses/implant failure, tooth sensitivity, pain in the teeth, jaw, masticatory muscle, and temporomandibular joint (TMJ), neck pains and headache, periodontal disease, oral or facial pain, and perhaps tooth loss. The diagnosis of nocturnal bruxism is based on complaints of tooth grinding or clenching, as well as one or more of the following signs: nonfunctional teeth attrition, sounds consistent with bruxism, and jaw muscle discomfort. Teeth wear and TMJ dysfunction can both be caused by bruxism. In some circumstances, delaying therapy might lead to luxation and degenerative arthritis of the temporomandibular joint. For the treatment of bruxism, many treatment approaches such as occlusal splints and pharmacologic medications such as psychobehavioral therapy or L-dopa, and psychobehavioral therapy have been examined but is not enough evidence to define a standard of reference approach for SB treatment. Botulinum toxin (Botox®) is an exotoxin generated by the bacteria Clostridium botulinum that causes muscle inactivity by blocking acetylcholine release from cholinergic nerve terminals into the neuromuscular junction. In the last two decades, several studies have been conducted to investigate the efficacy of botulinum toxin type A (BTXA) in reducing nocturnal bruxism, and the results have been promising. These studies have used different doses of botulinum toxin ranging from 20 mouse units (MU) and 25 MU to 30 MU in the masseter. Most of these studies did not take into account the relationship between the amount of botulinum toxin dose and alteration of the masseter muscle's size and the shape of the lower third of the face, where injection of more than 20 MU into the masseter muscle affects its size and is an effective treatment for masseter muscle hypertrophy for at least 9 months. To avoid the unwanted side effects of doses greater than 20 MU, the trial aimed to evaluate the effectiveness of injecting 10 MU of the Botulinum toxin into the masseter muscle in reducing the nocturnal bruxism. The idea of the research will explain to all patients, and the information sheets will distribute to them, then their consent will obtain.

In this group, patients will be injected with 10 MU of botulinum toxin type A in the masseter muscle.

100 MU of botulinum toxin type A (BOTOX® - Allergan Inc. - Dublin - Ireland) were diluted in 2ml of saline. Patients were injected with 10 MU of BTXA per side at two sites into the masseter muscle bilaterally. The first site was the inferior prominent part of the masseter muscle observed when the subject was asked to clench, and the other site was 5 mm below the first point

patients were pricked twice at the inferior prominent part of the masseter muscle observed using the stinger pen used in the blood glucose meter; it is less painful and provides psychological benefits, instead of injecting the physiological saline into the muscle to avoid the severe pain without a benefit to the patient which would not conform to the ethical standards.

EMG signals will record with Matrix EP Light EMG (Micromed, Via Giotto, Mogliano Veneto, Italy) with four channels. The recorded signals will amplify sampled at 1024 Hz, and the acquired data will analyze with System Plus Evaluation software (Micromed, Via Giotto, Mogliano Veneto, Italy). The acquisitions will perform twice with the rest position of the mandible (RPM) for 10 seconds, in maximal intercuspal position (MIP) for five seconds and maximal teeth clenching (MTC) with 10-mm thick cotton rolls between the posterior teeth for five seconds, bilaterally, and the values obtained will be averaged.

Assessment will be done before the injection (T0) and then at 2 weeks (T1), 3 months (T2), and 6 months after the injection (T3)

A visual analog scale (VAS) will be used for this assessment. A line of 100 mm in length will be used, and the patient will ask to put a mark on the line that reflects her/his perceived pain; the scores of the scale will be determined by measuring the distance in mm from the beginning to the point indicated by the patient (point (0): no pain and point (100): the highest levels of pain).

Assessment will be done before the injection (T0) and then at 2 weeks (T1), 3 months (T2), and 6 months after the injection (T3)

Inclusion Criteria: Moderate to severe pain in the masseter muscles during clinical examination. Age range between 18 and 40 years. Tooth-grinding sounds corroborated by family members or caregivers. Attrition in occlusal surface of posterior teeth. Exclusion Criteria: Loss two posterior teeth or more (except for third molars). Fixed or movable prosthodontics for more than four dental units. Advanced malocclusion (Class II occlusion Model II - deep bite - open bite). Temporomandibular disorders. Pain in the orofacial region. Insomnia. Known botulinum toxin allergy. Pregnancy. Neuromuscular disease. Bleeding disorders. Antibiotic therapy, pulmonary disease that produced coughing during sleep. Infectious skin lesion at the site of the injection.

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