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Summary of Efficacy of botulinum toxin in the treatment of bruxism: Systematic review





PMC6667018 (Ref ID)

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Title: Summary of Research Paper on “Efficacy of botulinum toxin in the treatment of bruxism: Systematic review”


I. IntroductionThis research paper aims to investigate the effectiveness of botulinum toxin in the treatment of bruxism, a condition characterized by teeth grinding and clenching. Bruxism can lead to various dental issues and temporomandibular disorders. The paper highlights the growing trend of using botulinum toxin as a therapeutic option for bruxism and conducts a systematic review of randomized clinical trials to evaluate its efficacy.


II. MethodologyThe study employs a systematic review methodology, following the guidelines established by the PRISMA declaration. Randomized controlled clinical trials involving individuals over 18 years with bruxism are included in the review. The interventions tested include injections of botulinum toxin type A (BTX-A) in the masseter and/or temporal muscles. The control interventions consist of placebo injections or traditional methods such as occlusal splints, medications, or cognitive-behavioral therapy. The research design allows for a comprehensive analysis of the effect of botulinum toxin on bruxism.


III. ResultsOut of the initial 68 studies identified, four randomized clinical trials met the inclusion criteria. The selected studies demonstrate that BTX-A injections can reduce the frequency of bruxism episodes, decrease pain levels, and lower the maximum occlusal force generated by bruxism. Comparatively, the treatment with BTX-A was found to be more effective than placebo or traditional methods for the treatment of bruxism. These findings suggest that infiltrations with BTX-A are a safe and effective treatment for patients with bruxism.


IV. DiscussionThe results of the study are analyzed and interpreted in relation to the research question and objectives. The discussions highlight the implications and significance of the study's findings, emphasizing that BTX-A treatment can provide substantial benefits to patients with severe bruxism. However, it is important to acknowledge the limitations of the study, such as the small number of selected trials and the potential biases in the included studies. Further research is needed to address these limitations and explore other aspects of BTX-A treatment for bruxism.


V. ConclusionIn conclusion, the systematic review confirms the efficacy of botulinum toxin type A (BTX-A) in the treatment of bruxism. The findings support the use of BTX-A infiltrations as a safe and effective treatment option for patients with bruxism, particularly those with severe symptoms. The study contributes to the field by providing valuable insights into the effectiveness of BTX-A and highlights the need for further research to address the study's limitations and expand our understanding of this treatment approach.


Flow chart of the study screening process using PRISMA guidelines

Flow chart of the article. Selection process for the systematic review, according to PRISMA guidelines (13).

The main characteristics of the studies included in the present systematic review are shown in Table 1.

Table 1

General information of the included studies. BTX-A: botulinum toxin A; IU: international units; M: masseter; T: temporalis; SS: saline solution; VAS: visual analog scale.

Author, sample size, age, area, Botox dose, control group dose, evaluations, methods , monitoring and efficacy

Lee et al. (18) performed a nocturnal electromyographic recording of the masseter and temporal muscles in 12 patients with bruxism, six of them received infiltrations of 80 IU of BTX-A (Dysport®, Ipsen Pharma, Wrexham, United Kingdom) distributed in three points of both masseter muscles, and the other six an equivalent amount of saline. The patients who received BTX-A reported a clinical improvement of the pathology; it was observed that the number of bruxism events decreased significantly after the injection of botulinum toxin in the masseter muscle but not in the temporalis muscle, without differing in the three post-injection times. Regarding the bruxism symptoms questionnaire data, the score decreased after the intervention in both the BTX-A and in the saline injection groups ( Table 2).

Table 2

Results of the clinical parameters evaluated by each study. BTX-A: botulinum toxin A; SS: saline solution; B: baseline; w: weeks; mm: millimeters; VAS: visual analog scale; TMTB: traditional methods of treating bruxism; sec: seconds; C: control group without intervention.

Results table of the clinical parameters evaluated by each study (eg, BTX-A, saline solution, visuals, questions and groups)

In the study by Guarda-Nardini et al. (19) injected 30 IU of BTX-A (Botox®, Allergan Inc., Irvine, E.E.U.U) in masseter muscles and 20 IU in temporal muscles to 10 patients with myofascial pain associated with bruxism. The descriptive analysis of the study showed a slight increase in the values of the maximum unassisted and assisted movements of buccal, protrusive and laterotrusive opening (mm) in the BTX-A group (the differences between the baseline and follow-up values had a tendency to increase) and remained unchanged in the placebo group. Regarding the symptoms (pain at rest and in mastication), evaluated by means of a visual analogue scale (VAS), they decreased in the BTX-A group while in the placebo group it remained constant, although the effectiveness of the mastication did not improve in neither of the two groups ( Table 2).

Al-Wayli et al. (16) compared the efficacy of treatment with BTX-A versus conventional treatments for bruxism. For this, they recruited 50 subjects diagnosed with nocturnal bruxism, 25 were infiltrated with 20 IU of BTX-A (Botox®, Allergan Inc., Irvine, USA) in three points of both masseters, and the other 25 were treated with behavioral therapy, occlusal splint and pharmacological measures (diclofenac 50 mg). In the assessment of pain, there were no significant differences in the mean preoperative pain score between the two groups, however, there was a relevant difference in the average value of postoperative pain at 3 weeks in both the BTX-A group and in the control group that used traditional methods for the treatment of bruxism. From the second postoperative month, the mean pain score decreased significantly in both groups, reaching its lowest value at the sixth month and being much lower in the BTX-A group than in the control group ( Table 2).

Zhang et al. (17) recruited 30 patients with bruxism to assess the therapeutic efficacy of BTX-A injection in terms of occlusal force, biting time and symmetric distribution of occlusal force using a T-Scan. 10 patients were infiltrated with 25 IU/ml of BTX-A in three points of both masseter muscles, another 10 were infiltrated with saline in the same way and the remaining 10 were a control group without any intervention. The bite time in the BTX-A group was significantly longer after three months, and decreased after six months, but there were no significant changes in the placebo and control groups. With respect to the maximum occlusal force, significantly lower values were achieved in the BTX-A group compared to the other two groups where there were no relevant differences, reaching its lowest value after three months of treatment. There were no significant differences between the groups in the symmetric distribution of the occlusal force, however, there was a tendency towards its improvement during the treatment ( Table 2).

-Risk of bias assessment

The evaluation of the risk of bias through the Cochrane criteria showed positive results in the generation of random sequence, and in the absence of incomplete data and selective results for the four included studies, but in none of them, despite being RCTs , the method used to generate the allocation sequence and the measures to blind the participants and the study staff, in particular the studies of Zhang et al. (17) and Al-Wayli et al. (16) they do not specify that they be blinded, and in this last one the sample was formed entirely by women, this makes that these last two studies have a high risk of bias, and those of Lee et al. (18) and Guarda-Nardini et al. (19) a low risk of bias (Fig. ​(Fig.22).

Risk of bias assessment table for the studies

Risk of bias assessment. According to the Cochrane Hand book for Systematic Reviews of Interventions, version 5.1.0 (15). +: low risk of bias; - : high risk of bias; ?: unclear risk of bias.

-Data extraction: qualitative synthesis

The results of these studies showed that BTX-A injections can reduce the frequency of bruxism episodes, decrease pain levels and the maximum occlusal force generated by this pathology, offering superior effectiveness in the treatment of bruxism compared to the control groups that were treated with placebo or with traditional methods for the treatment of bruxism. Of the four included studies, Guarda-Nardini et al. (19) and Al-Wayli et al. (16), did not specify if the botulinum toxin injections had adverse effects, however Lee et al. (18) and Zhang et al. (17) reported the absence of such adverse effects, both locally and systemically.

-Data extraction: quantitative synthesis

Due to the heterogeneity presented to the results of the different studies, since each one measures the variables in different ways, it is not possible to do a meta-analysis with the available data.



Botulinum toxins, purified exotoxins of Clostridium botulinum, have been used for a long period of time for numerous neuromuscular disorders (20,21). These toxins can inhibit neuromuscular transmission, which justifies its clinical application in the treatment of bruxism, since recent scientific evidence has indicated that bruxism has a multifactorial etiology mediated by the central nervous and autonomic systems, which regulate the motor activity of the chewing muscles (22,23).

Currently, many authors (24-26) support the use of BTX-A for the treatment of various conditions of the oral-maxillofacial region based on the positive results obtained in various clinical trials collected in the literature. Rao et al. (24) made a review showing the results of several clinical trials and case reports that supported the use of BTX-A for the treatment of TMD, gingival smile correction, muscle hypertrophy and spasms, headache (migraine), trigeminal neuralgia and even after the placement of dental implants. They noted that although BTX-A could decrease muscle strength and mastication, it is temporary and normal function would return when the effect of the toxin disappeared. Gay-Escoda et al. (25) conducted a review of the literature that included clinical trials in which BTX-A was used in the salivary glands for the treatment of sialorrhea derived from different neurological disorders such as infantile cerebral palsy, the disease of Parkinson’s and amyotrophic lateral sclerosis. More than half of the authors injected the product into the parotid glands, 9.5% in the submaxillary glands and 38% in both. The total doses of toxin injected varied from 10 to 100 IU of Botox® or 30 to 450 IU of Dysport® according to the different authors. A reduction in saliva production was observed after these injections, and the duration of the therapeutic effect was 1.5-6 months. Six articles (30%) described the presence of adverse effects such as dysphagia, xerostomia and difficulties to chew. The authors concluded that the injection of BTX-A in the salivary glands may be a valid treatment option in patients with sialorrhea, since it is able to improve the quality of life, however, it is important to be aware that the duration of the therapeutic effect is limited in time and usually lasts a few months. In a retrospective study carried out by Alonso-Navarro et al. (26), the evolution of 19 patients with severe bruxism who were treated periodically with infiltrations of BTX-A in both temporal and masseter muscles, using initial doses of 25 IU per muscle, during follow-up periods of 0.5 to 11 was described; the doses were adjusted throughout the follow-up according to the degree of response observed. None of the patients presented side effects. The final dose ranges reached ranged from 25 to 40 IU per muscle and the duration of the effects ranged from 13 to 26 weeks. Based on these results, they concluded that infiltrations with BTX-A are a safe and effective treatment for patients with severe bruxism. The four studies that we have selected for the review showed that BTX-A injections can reduce the frequency of bruxism episodes, decrease pain levels and the maximum occlusal force generated by this pathology, offering more satisfactory clinical results in the treatment of bruxism compared to control groups that were treated with placebo or traditional methods, thus reiterating that the use of BTX-A is an effective alternative in the treatment of this pathology.

Psychological factors play a very important role both in the etiology and in the treatment of bruxism (27). This aspect is reflected in the results of the study by Zhang et al. (17), since the values of maximum masticatory force had been reduced, although to different degrees, both in the BTX-A experimental group, and in the placebo and control groups without intervention. This change in biting force in the placebo and control groups indicates that psychological intervention can play an important role in the treatment of bruxism.

The effect of the BTX-A is transient and is largely limited to the injection area. A review by Ihde and Konstantinovic (28) has indicated that the most common adverse effects of BTX-A are local, such as sensitivity and mild cutaneous reaction at the site of injection, systemic effects, such as headache and nervous atrophy. reversible, and specific effects, including dysphonia, dysphagia and dry mouth. However, of the four studies included in the review, only two (Lee et al. (18) and Zhang et al. (17)) reported the absence of adverse effects at the time of treatment, but none of them reported the possible adverse effects after the injection. Tan and cols. (29) and Monroy et al. (30) have explained in their studies that the use of BTX-A in the treatment of bruxism can cause dysphagia or mild pain at the site of injection and temporary drooling, however, patients who suffered these adverse effects received a large dosage (> 100 IU) or had a condition complicated by other medical conditions. In none of the four studies we have selected exceeds the total dose of 100 IU, therefore, injections of BTX-A at a dose lower than 100 IU in the masseter or temporal muscles in patients who are otherwise healthy are safe, its use being feasible in the usual clinical practice.

The results of the present review showed that injections of BTX-A in the masseter and/or temporal muscles can be a valid treatment option in patients with bruxism, since they can improve the quality of life. However, it is not exempt from limitations, since most of the samples are too small to allow obtaining statistically significant results. Furthermore, in none of the included studies, despite being randomized clinical trials, the method used to generate the allocation sequence is described, nor are the measures to blind the participants and the study staff, in fact, in two of the studies do not specify that they be blinded and in one of them the sample completely lacked homogeneity since it was completely made up of women. To all this, it must be added that in all the studies except one, the follow-up period for the patients was less than one year, which makes the need for long-term controlled studies that allow us to assess both the therapeutic effect indispensable. as the adverse effects of this treatment over the years.



In conclusion, the infiltrations of BTX-A can reduce the frequency of bruxism episodes, as well as the masticatory force, and decrease the levels of pain derived from it, which translates into an improvement in the quality of life of patients. In addition, in doses <100UI it is a safe treatment with a low probability of adverse effects occurring in healthy patients. Therefore, the use of BTX-A is a safe and effective treatment for patients with bruxism that shows better clinical results than traditional methods such as occlusal splints, drugs or cognitive-behavioral therapy, so its use would be justified in daily clinical practice, especially in patients diagnosed with severe bruxism.



The authors declare that they do not have any conflict of interest. This study has been performed by the research group ‘‘Odontological and Maxillofacial Pathology and Therapeutic’’ of Biomedical Investigation Institute of Bellvitge of Barcelona, Spain.



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