A review published in the “International Dental Journal” by Long et al., studied the “Efficacy of botulinum toxins on bruxism” 1. The aim of the study was to evaluate botulinum toxin effectiveness on bruxism using nonrandom and randomized controlled studies from electronic databases, websites, and SIGLE literature databases between January 1990 and April 2011 without any language restriction. This strategy delivered 94 studies from Embase, 28 from PubMed, two from continuing clinical trials, two from CENTRAL, and 60 from SCI, however only four of these studies were able to meet inclusion criteria which were then finally selected for this article. These studies revealed that the injection of botulinum toxin in a dose of <100U in otherwise healthy patients presented a better outcome in reducing the frequency and pain associated with bruxism as compared to an oral splint.
What is Bruxism?
Bruxism is defined by tooth clenching or grinding which can lead to orofacial lesions including periodontal lesions, wearing out of the tooth, defective temporomandibular joint, and muscular pain.
How to treat Bruxism
Although the strategy to combat this condition has been found in the form of an oral splint, behavioral modification approach, and medicines, nevertheless all of these approaches have not been proven to be reasonably effective to cure the condition.
Can Botulinum toxin help Manage Bruxism?
As studies have shown that a high motor activity that is centrally mediated in jaw muscle is responsible for bruxism, botulinum toxin can be an effective agent in managing it as it can inhibit contraction of muscle by blocking acetylcholine release however, its efficacy on bruxism is yet to be demonstrated. This article assesses the effectiveness of botulinum toxin in managing bruxism through a systematic review of random and nonrandom controlled studies.
Scientific Research on Botulinum Toxin Effectiveness in the Treatment of Bruxism
This review analyzed random and non-random controlled studies that stated the effectiveness of botulinum toxin in the treatment of bruxism. Studies that have evaluated bruxism induced by some discrete disorder such as Huntington’s disease or brain injury or as a side effect of medications or in which therapy for bruxism was not the focus were excluded. The age of patients that were the subject of these studies was over 18 years. Botulinum toxin was taken as the test intervention whereas for the control intervention a placebo or oral splint was used.
The database implored were PubMed, SCI, CENTRAL, Embase, and SIGLE literature databases. The keywords used for searching these databases included tooth clenching, Bruxism, tooth grinding, botulinum toxin, Botox, botulinum toxin, and data was collected from the articles between January 1990 and April 2011 without any language restriction.
Figure 1 Systematic search and selection criteria
The overall data that was dug out and collected consisted of information about participants, follow-up periods, study design, and outcomes. The primary outcome was considered a decreased frequency of bruxism whereas the secondary outcomes were a reduction in pain scores, improvement in sleep quality, and subjective assessment of effectiveness. The adverse effects both systematic and local which came into notice were also extracted for the study. The collected data was analyzed through Review Manager 5 software for Cochrane reviews.
Quality assessment was performed by evaluating the weaknesses and strengths of all the studies included in consultation with the handbook of Cochrane Reviewers. The points that were considered in this process were the following (i) Is there an adequate sequence generation (ii) was the study designed as a blind test (iii) was there an allocation concealment of P values to prevent selection bias (iv) is there any selective reporting of the outcome (v) Were biases removed from the study (vi) Was the outcome of the incomplete data sufficiently reported.
Table 2
Research-based evidence; Botulinum toxin can treat Bruxism
Only a random-controlled study by Lee et al studied the reduction in the frequency of bruxism after botulinum injection as compared to a placebo. EMG results showed considerably lower frequency in the botulinum group as compared to the placebo group.
Botulinum toxin reduces the pain induced by Bruxism
Three studies by. Sener et al., Guarda-Nardini et al., and Sener et al. Bolayir et al. reported the botulinum toxin efficacy in reducing pain. Guarda-Nardini et al. study was 20 participants comprising a random controlled trial whereas Bolayir et al. study focused on VAS of pain that compared the intensity of pain before and after the injection of botulinum toxin. Sener et al. study consisted of two phases in which 13 participants received an oral splint and botulinum toxin injection sequentially and the level of pain was recorded between the oral splint phase and botulinum toxin phase. Guarda-Nardini et al. studied resting pain level and chewing pain level and evaluated them with VAS in the range of 0–10. The result showed that chewing pain level was substantially reduced by botulinum toxin after a follow-up of 6 months. However, the reduction in pain with chewing was not shown when evaluated in the first week or the first month after injection similarly no reduction was reported after the first week, month, or 6 months in bruxism-induced pain at rest.
Comparing the level of pain evaluated by VAS before and after injection of botulinum toxin Bolayir et al. reported that pain levels were considerably decreased in masseter muscles at 1-month and 3 months intervals following botulinum injection. Sener et al. comparing the improvement of oral splint and botulinum toxin stated that both oral splint and botulinum toxins significantly reduced the pain making them equally effective against bruxism.
Comparing the subjective evaluations of four studies to check for the efficacy of botulinum toxins against bruxism, Guarda-Nardini et al and Lee et al. revealed the effectiveness of botulinum injection through subjective evaluation. However, the standards used by them to evaluate the efficacy were divergent as Guarda-Nardini et al. employed a subjective scale for efficacy whereas LEE et al., used a bruxism questionnaire that lead to a discrete analysis of the results.
Lee et al. showed that when efficacy is studied with subjective evaluation, the difference between the two groups that is botulinum toxin and placebo group is not considerable after 4, 8, and 12 weeks followed by injection. Guarda-Nardini et al. stated that the subjective evaluation of effectiveness significantly differs between the placebo and botulinum toxin groups only after 6 months and not after the first week or month.
Are there any side effects of Botulinum toxin injection?
Accessing the safety of the injection of botulinum toxin Sener et al, and Guarda-Nardini et al. did not state any adverse effects associated with it whereas Bolayir et al and Lee et al. reported no systematic or local adverse effects after injection of botulinum toxin.
Does Botulinum toxin injection improve sleep quality in Bruxism patients?
Unfortunately, neither of these four studies addressed the issue of improvement in the quality of sleep after the injection of botulinum toxin.
How does botulinum toxin work to treat Bruxism?
Refined exotoxins of Clostridium botulinum which are also known as botulinum toxins were traditionally used for the treatment of neuromuscular disorders. Studies have revealed that a high motor activity of jaw muscles that are centrally mediated caused bruxism which can be treated by botulinum toxins through inhibiting neuromuscular transmission.
The literature search revealed four studies, two randomized controlled studies, and two non-random controlled trials that have evaluated the effectiveness of botulinum toxin in the treatment of bruxism.
Table 3
EMG reports confirm Botulinum toxin injection effect on bruxism
A study using EMG for evaluation revealed that botulinum toxins were found to decrease the frequency of bruxism when compared with a placebo. A randomized controlled study by Guarda-Nardini et al through a VAS score for 6 months revealed better long-term pain management through botulinum toxin as compared to a placebo. Similarly, Bolayir et al reported through Vas score before and after botulinum injection that pain is substantially reduced after injection of botulinum however an absence of control in this study hints at a bias.
Oral splint vs Botulinum Toxin; Which is a better option to treat Bruxism
The oral splint is another treatment option for bruxism and Sener et al reported justification of botulinum use in clinical practice as they found that botulinum toxins were as much effective as an oral splint. However, in this particular study, the same subject was used for checking the comparative effectiveness of oral splint and botulinum toxin on the reduction of pain level which show biases in the study and a need for further research.
Is the effect of Botulinum toxin on Bruxism subjective?
Guarda-Nardini et al. and Lee et al stated the subjective assessment for the efficacy of botulinum toxin which did not show any difference between the placebo and botulinum toxin group in Lee et al., whereas Guarda-Nardini et al. revealed a significantly higher score in botulinum group as compared to placebo. This divergence may be a consequence of the subjective evaluation with different standards and a follow-up period that lasted longer. Nevertheless, no study showed improved quality of sleep through the use of botulinum injection.
Are there any limitations of botulinum toxin injection
Botulinum toxin efficacy is reported to be short-term and confined to the area where the injection is given. Ihde and Konstantinovic have pointed out that the recurring adverse effects are localized in the case of botulinum toxin when given in high doses i.e > 100U such as skin irritation, tenderness at the injection site, or are systemic effects such as dry mouth, headache, dysphonia, denervation atrophy, and dysphagia, however, it was found that unwanted effects were mainly associated with usage of botulinum toxin for other disorders such as cervical dystonia.
The four studies used in the review did not comprise dosages that were higher than 100 U. However, the two studies that studied adverse effects associated with botulinum injections, did not reveal any local or systematic adverse reaction after injection. The other two studies have stated localized soreness, temporal drooling, and dysphagia in patients who were administered a large dosage (>100 U) or were suffering from other medical conditions. Thus, an inference that a dose below 100U of botulinum toxin injection in temporalis muscles or masseter is safe in patients without other medical conditions can be safely made.
Botulinum toxin; a promising treatment strategy for bruxism
This review article concludes that the frequency of bruxism, as well as pain associated with it, is substantially reduced by botulinum injection as shown through patient-based satisfactory assessment thus making them equally effective with oral splint in the treatment of bruxism when used in lower than 100U dose in patients without other medical issues. Nevertheless, it can’t be ignored that out of these studies, only two randomized controlled studies meet the quality standard and neither of them addressed the botulinum effect on improving the quality of sleep. It leads to the need for additional studies containing high-quality random controlled trials with a focus on comparing the injection of botulinum toxin with an oral splint and its effect on the quality of sleep, moreover, its usage in clinical setup must also be promoted.
Abbreviations
CENTRAL Cochrane Central Register of Controlled Trials and Clinical Trials
SIGLE System for Information on Grey Literature in Europe
SCI Science Citation Index
EMG Electromyography
VAS Visual analog scale
Reference
1. Long, H., Liao, Z., Wang, Y., Liao, L. and Lai, W., 2012. Efficacy of botulinum toxins on bruxism: an evidence‐based review. International dental journal, 62(1), pp.1-5.
Comments