Botulinum Toxin Type A for Myogenous Temporomandibular Disorders, Focusing on the Duration of Clinical Effects and Dosage Parameters: A Systematic Review

Abstract

Background

Botulinum toxin type A (BoNT-A) has been increasingly investigated as a therapeutic option for myogenous temporomandibular disorders (TMD), yet uncertainties remain regarding the duration of its clinical effects and the relevance of dosing parameters. Objective: To systematically evaluate the clinical effects, duration of action, and dosage parameters of BoNT-A in the management of myogenous temporomandibular disorders. Methods: This systematic review followed PRISMA 2020 guidelines and was registered in PROSPERO. Electronic searches were conducted in PubMed/MEDLINE, Embase, Scopus, Web of Science, and LILACS. Randomized clinical trials evaluating BoNT-A for myogenous TMD were included. Study selection, data extraction, and risk of bias assessment using the Cochrane Risk of Bias 2 (RoB-2) tool were performed independently. Due to methodological heterogeneity, a qualitative synthesis was conducted. Results: Ten randomized clinical trials were included. Pain was assessed using validated instruments, including the Visual Analog Scale, Characteristic Pain Intensity, and Numeric Rating Scale. Pain reduction over time was reported in both BoNT-A and control groups, including placebo and conservative therapies. In placebo-controlled trials, BoNT-A did not consistently demonstrate superiority over saline injections. Greater pain reductions were reported in studies involving refractory myofascial pain. Improvements in mandibular function were observed in both intervention and control groups. Clinical effects were generally reported to persist for 8 to 24 weeks. Current evidence is insufficient to determine whether a clinically relevant dose–response relationship exists across the evaluated regimens. Adverse events were mostly mild to moderate and transient. Conclusions: Current evidence does not support the routine use of BoNT-A as a first-line treatment for myogenous temporomandibular disorders. Its use may be considered in selected refractory cases after failure of conservative therapies.

Supplementary Information

The online version contains supplementary material available at https://doi.org/10.1186/s13005-026-00637-7.

Introduction

Myogenous temporomandibular disorders (TMD) constitute one of the most prevalent subtypes of temporomandibular disorders and represent a major cause of chronic orofacial pain and functional limitation [1, 2]. These conditions are primarily characterized by pain originating from the masticatory muscles, frequently associated with muscle hyperactivity, spasm, altered neuromuscular coordination, and reduced mandibular mobility. Epidemiological data indicate a significant impact of myogenous TMD on quality of life, work productivity, and psychosocial well-being, particularly in adult populations [3, 4].

Conventional therapeutic approaches for myogenous TMD include occlusal splints, physiotherapy, behavioral interventions, and pharmacological management with analgesics, non-steroidal anti-inflammatory drugs, and muscle relaxants [3, 5–7]. Although these modalities are effective for many patients, a substantial proportion exhibit persistent symptoms or limited response, especially in cases associated with chronic muscle hyperactivity or central sensitization. This therapeutic gap has stimulated interest in minimally invasive interventions capable of modulating muscular activity more directly [8, 9].

Botulinum toxin type A (BoNT-A) has emerged as a potential therapeutic alternative for myogenous TMD due to its ability to induce reversible chemodenervation through inhibition of acetylcholine release at the neuromuscular junction. Beyond its muscle-relaxant effect, BoNT-A has been suggested to exert analgesic properties by modulating peripheral nociceptive signaling and reducing the release of pro-inflammatory neuropeptides. These mechanisms support its clinical application in conditions characterized by sustained muscle contraction and myofascial pain [10, 11].

Despite increasing clinical use, the scientific literature addressing BoNT-A in myogenous TMD remains heterogeneous and, in some aspects, controversial. Randomized clinical trials report variable outcomes, which may be partially explained by substantial differences in study design, diagnostic criteria, dosage regimens, targeted muscles, number of injection sites, and follow-up periods [12]. In particular, there is no consensus regarding optimal dose per muscle, cumulative dose, or expected duration of clinical benefit, limiting the reproducibility and clinical translation of available evidence [13].

Previous systematic reviews have primarily focused on the overall effectiveness of BoNT-A compared with placebo or conservative therapies, often without detailed analysis of dosage parameters or durability of therapeutic effects. Consequently, clinicians lack evidence-based guidance to inform individualized treatment planning and risk–benefit assessment [14, 15].

In this context, a systematic review specifically designed to evaluate the duration of clinical effects and dosage parameters of botulinum toxin type A in the management of myogenous TMD is warranted. By synthesizing evidence exclusively from randomized clinical trials and employing rigorous methodological assessment, this review aims to clarify the therapeutic profile of BoNT-A and contribute to the standardization of clinical protocols in the management of myogenous temporomandibular disorders.

Materials and methods

Study design and registration

This systematic review was designed and conducted in accordance with the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA-P) guidelines. The protocol was prospectively registered in the International Prospective Register of Systematic Reviews (PROSPERO) under the registration number CRD420251178977 toxin type A. Any deviations from the registered protocol will be explicitly reported and justified in the final manuscript.

Eligibility criteria

The eligibility criteria were defined based on the PICOS framework (Population, Intervention, Comparator, Outcomes, and Study design), as shown in Table 1.

Table 1.

PICOS (Population, Intervention, Comparator, Outcomes, and Study design)

Component	Description
P (Population)	Patients diagnosed with myogenous temporomandibular disorders, established using validated diagnostic criteria such as the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) or the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD), regardless of age, sex, or ethnicity.
I (Intervention)	Therapeutic treatment with botulinum toxin type A (BoNT-A) administered through intramuscular injections into masticatory muscles, including the masseter, temporalis, lateral pterygoid, or other involved muscles.
C (Comparator)	Placebo injections, conventional conservative therapies (e.g., occlusal splints, physiotherapy, analgesics, muscle relaxants), or no treatment.
O (Outcomes)	Primary outcomes: pain reduction assessed by validated scales (VAS, NRS) and duration of clinical effect (time to symptom relapse).Secondary outcomes: improvement in mandibular function (e.g., maximal mouth opening), reduction in muscle tenderness or spasm, and occurrence of adverse events.
S (Study design)	Randomized clinical trials conducted in clinical or hospital settings.

Source: Authors

Information sources and search strategy

A comprehensive electronic search was performed in the following databases: MEDLINE/PubMed, Embase, Scopus, Web of science and LILACS. No restrictions regarding language or publication date were applied. To identify additional relevant studies, reference lists of included articles were manually screened (backward citation searching). The complete search strategies for all databases are described in detail in the registered protocol and in the supplementary material. The final electronic literature search was conducted on 22 December 2025.

Study selection

All retrieved records were imported into Rayyan software to manage references and remove duplicates. Titles and abstracts were independently reviewed by two reviewers to assess eligibility. Full articles of potentially relevant studies were subsequently evaluated for final inclusion. Disagreements at any stage were resolved through discussion and consensus or, when necessary, by consultation with a third reviewer.

Data extraction

Data extraction was performed independently by two reviewers using a standardized form. The extracted data included study characteristics (Author (Year), country, study design, sample size (n), population characteristics (age/sex), TMD diagnostic criteria, TMD type, injected muscles, BoNT-A formulation, BoNT-A dose per muscle (U), total BoNT-A dose (U), application protocol, comparator, follow-up time, primary outcomes assessed, main results, duration of clinical effect, reported adverse events, authors’ conclusions), sample size, diagnostic criteria, intervention details (botulinum toxin type A dosage, injection sites, number of injection points). Table 2 shows the extracted data.

Table 2.

Data Extraction on the Use of Botulinum Toxin and Other Therapies in Temporomandibular Disorders (TMD) Management

Author (Year)	Country	Study Design	Sample Size (n)	Population Characteristics (Age/Sex)	TMD Diagnostic Criteria	Type of TMD	Injected Muscles	BoNT-A Formulation	BoNT-A Dose per Muscle (U)	Total BoNT-A Dose (U)	Application Protocol	Comparator	Follow-up Time	Primary Outcomes Evaluated	Main Results	Clinical Effect Duration	Reported Adverse Events	Authors’ Conclusions
Foscaldo (2025) [16]	Brazil	RCT, single-blind	40	Mean age ~ 30; 72.5% Female	DC/TMD	Associated with awake bruxism	Masseter, Temporal	Xeomin	Masseter: 15U; Temporal: 5U	40U	Bilateral; Masseter (3 points), Temporal (1 point)	Biofeedback (EMG)	6 months	Bruxism frequency (EMA), pain (CPI), psychosocial	Significant reduction in bruxism behaviors only in Biofeedback group; no difference in pain between groups	Not reported	None	Biofeedback reduced bruxism behaviors; low-dose BoNT-A did not outperform the comparator
Yurttutan (2019) [17]	Turkey	RCT, single-blind	73	Mean age ~ 30; 61.6% Female	RDC/TMD	Myogenic associated with bruxism	Masseter, Temporal	Botox	Masseter: 30U; Temporal: 15U	90U	Bilateral; Masseter (5 points), Temporal (3 points)	Occlusal splint	6 months	Pain (VAS), jaw function (JFLS), oral behaviors (OBC)	Significant pain reduction in all groups; BoNT-A groups superior to splint alone	Maintained for 6 months	Asymmetric smile (1 patient)	Occlusal splints may be unnecessary in patients treated with BoNT-A injections
De la Torre Canales (2024) [18]	Brazil, Sweden, Portugal	RCT, double-blind	28	Mean age 43.1; 85.7% Female	DC/TMD	Refractory Myofascial Pain	Masseter, Temporal	Botox	Masseter: 30U; Temporal: 10U	80U	Bilateral; 5 injections per muscle	Placebo (Saline)	6 months	Pain (VAS), PPT, CPM, psychosocial	Robust pain reduction (50%) and increased PPT in BoNT-A group vs. placebo	Maintained for 6 months	Muscle weakness (10 patients), asymmetry (2), dysphagia (1)	BoNT-A is effective for treating refractory masticatory myofascial pain
De la Torre Canales (2021) [19]	Brazil	RCT, single-blind	54	Mean age ~ 31; 100% Female	RDC/TMD	Refractory Myofascial Pain	Masseter, Temporal	Botox	Masseter: 30U; Temporal: 10U	80U	Bilateral; 5 points per muscle	Acupuncture; Saline	1 month	Pain (VAS), PPT, EMG	Pain reduced in all groups; BoNT-A was the only treatment to significantly increase PPT	1 month	Edema, pain on injection; severe EMG reduction	All therapies reduced perceived pain, but BoNT-A had a superior effect on pain threshold
Minston (2024) [20]	Sweden	RCT, multicenter	45	Mean age ~ 35; 87% Female	DC/TMD	Myalgia	Masseter, Temporal	Botox	Masseter: 30U; Temporal: 20U	100U	Bilateral; 14 total points	Placebo (Saline)	2 months	Days with functional pain, pain (NRS), JFLS-8	Numerical reduction in pain days, but no statistically significant difference vs. placebo	2 months	Fatigue, headache, nausea	A single BoNT-A session was not effective for treating jaw myalgia in this sample
Sitnikova (2024) [21]	Finland	RCT (Crossover)	57	Mean age 38.2; 82.5% Female	DC/TMD	Myogenic	Masseter, Temporal	Xeomin	Masseter: 16.7U; Temporal: 8.3U	50U	Bilateral; Masseter (3 points), Temporal (2 points)	Placebo (Saline)	32 weeks	Pain (CPI), GCPS, EMG, bite force	Significant pain improvement in both groups; no BoNT-A superiority over placebo	Up to 16 weeks	Smile asymmetry, headache	50U BoNT-A injections might improve TMD, but the specific drug effect is not obvious
Montes-Carmona (2021) [22]	Spain	RCT	60	Mean age ~ 43; 81.6% Female	DC/TMD	Myofascial (Local or Referred)	Masseter, Temporal, Pterygoids	Botox	Temp (24U), Mass (24-30U), Pteryg (8U)	100–150U	Bilateral; Temp (3p), Mass (3p), Pteryg (1p)	Lidocaine; Saline	6 months	Pain (VAS), MIO, laterality, protrusion	Significant pain reduction and functional improvement superior to lidocaine and saline groups	Maintained for 180 days	Local pain, hematoma	BoNT-A is effective in myofascial TMD, especially for localized and focused pain
Reeve (2024) [23]	USA	RCT, multicenter	75	Mean age ~ 36; 81% Female	DC/TMD	Myalgia (Myofascial)	Masseter, Temporal	OnabotulinumtoxinA	Masseter: 37.5U; Temporal: 12.5U	100U	Bilateral; Masseter (3p), Temporal (2p)	Placebo (Saline)	3 months	Pain (VAS), MIO, JFLS-8, SF-36	Both groups (BoNT-A and saline) significantly reduced pain and improved function	3 months	Increased pain (4 patients), headache (1), weakness (1)	BoNT-A and placebo injections decrease pain similarly; needling effect suggested
De la Torre Canales (2022) [24]	Brazil, Portugal, Sweden	RCT	80	Age 18–45; 100% Female	RDC/TMD	Persistent Myofascial	Masseter, Temporal	Botox	Various (Low, Med, High)	40, 70, or 100U	Bilateral; 5 points per muscle	Placebo (Saline)	180 days	MMO (pain-free, unassisted, assisted), laterality	BoNT-A significantly improved all movement parameters vs. placebo after 180 days	6 months	Not reported	BoNT-A improves mandibular range of motion regardless of the dose used
Kim (2023) [25]	South Korea	Pilot RCT	21	Mean age ~ 34; 90.5% Female	DC/TMD	Myogenic and headache	Masseter, Temporal, SCM, Trapezius	Botulax	10U per point	Max 150U	Tender point areas (up to 16 total points)	Placebo (Saline)	12 weeks	Orofacial pain (OVAS), headache (HVAS), tender points	Significant reduction in pain intensity, tender points, and headache frequency vs. placebo	12 weeks	None	BoNT-A was relatively effective for masticatory muscle pain and headache vs. placebo

Source: Authors

Abbreviations: BoNT-A Botulinum toxin type A, CPI Characteristic Pain Intensity, CPM Conditioned pain modulation, DC/TMD Diagnostic Criteria for Temporomandibular Disorders, EMA Ecological momentary assessment, EMG Electromyography; GCPS Graded Chronic Pain Scale, HVAS Headache Visual Analog Scale, JFLS Jaw Functional Limitation Scale, JFLS-8 8-item Jaw Functional Limitation Scale, MIO Maximum interincisal opening, MMO Maximum mouth opening, NRS Numeric Rating Scale, OBC Oral Behaviors Checklist, OVAS Orofacial Visual Analog Scale, PPT Pressure pain threshold, RCT Randomized clinical trial, RDC/TMD Research Diagnostic Criteria for Temporomandibular Disorders, SCM Sternocleidomastoid muscle, SF-36 36-Item Short Form Health Survey, TMD Temporomandibular disorders, VAS Visual Analog Scale

Risk of bias assessment

The methodological quality and risk of bias of included studies were assessed independently by two reviewers using the Cochrane Risk of Bias Tool version 2 (RoB-2), Fig. 2. The following domains were evaluated: randomization process, deviations from intended interventions, missing outcome data, measurement of outcomes, and selection of the reported result. Discrepancies were resolved by consensus.

Fig. 2.

Analysis of the risk of bias using the Rob-2 tool. Source: Authors

Certainty of the evidence

The certainty of the evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. Randomized clinical trials were initially considered to provide high-certainty evidence and could be downgraded according to five domains: risk of bias, inconsistency, indirectness, imprecision, and publication bias.

The assessment was performed separately for the following clinically relevant outcomes: pain intensity, mandibular function, duration of clinical effects, dose–response relationship, and adverse events. Certainty was classified as high, moderate, low, or very low. Because statistical pooling was not considered appropriate owing to substantial clinical and methodological heterogeneity, GRADE judgments were based on the direction and consistency of the findings, methodological limitations, sample sizes, confidence intervals when reported, and the clinical comparability of the included studies. Two reviewers independently assessed the certainty of the evidence, and disagreements were resolved through discussion and consensus. The complete GRADE assessment and the Summary of Findings table are provided in Supplementary Material 2.

Results

The electronic searches identified 179 records: 36 from Embase, 31 from MEDLINE/PubMed, 77 from Scopus, 29 from Web of Science, and 6 from LILACS. After the removal of 24 duplicate records, 155 unique records remained for title and abstract screening. Of these, 119 records were excluded because they did not meet the predefined eligibility criteria. The full texts of 36 potentially eligible reports were retrieved and assessed. No reports were unavailable for full-text evaluation. Following full-text assessment, 26 reports were excluded because of ineligible study design, absence of an eligible comparator, inclusion of populations without myogenous temporomandibular disorders, or failure to evaluate botulinum toxin type A as the primary intervention. Ultimately, 10 randomized clinical trials met the eligibility criteria and were included in the qualitative synthesis. The study-selection process is presented in Fig. 1.

Fig. 1.

Fluxograma PRISMA 2020. Source: Authors

Summary of results

Pain outcomes

All included randomized clinical trials assessed pain as a primary or secondary outcome, using validated instruments such as the Visual Analog Scale (VAS), the Characteristic Pain Intensity (CPI), and the Numeric Rating Scale (NRS) [17–23, 25].

Pain reduction over time was reported in both botulinum toxin type A (BoNT-A)–treated groups and control groups, including saline placebo, occlusal splints, acupuncture, and biofeedback [16, 17, 19, 23]. In placebo-controlled trials, comparisons between BoNT-A and saline injections did not demonstrate statistically significant differences across all included studies [20, 21, 23].

In studies that included populations with refractory myofascial pain, greater pain reductions were reported in the BoNT-A groups compared with placebo, with maintenance of the effect throughout the reported follow-up period [18, 24].

Comparisons between BoNT-A and conservative therapies, such as acupuncture, occlusal splints, and biofeedback, showed pain reduction in both groups, without consistent differences between the evaluated interventions [16, 17, 19].

Functional outcomes

Mandibular function was assessed using maximal mouth opening (MMO/MIO), excursive movements, and self-reported functional instruments, including the Jaw Functional Limitation Scale (JFLS) [17, 20, 23].

Improvement in mandibular function over time was reported in studies using botulinum toxin type A (BoNT-A) as well as in control groups during short- to medium-term follow-up periods [22–24]. In placebo-controlled trials, functional outcomes were similar between BoNT-A and saline groups throughout the reported follow-up period [20, 23].

In comparative studies with lidocaine or conservative therapies, differences between groups were reported at specific assessment time points, as described individually in each study [22, 24].

Duration of clinical effect

The duration of the clinical effect was reported variably across the included studies. In randomized clinical trials, the effects observed after BoNT-A administration were described over periods ranging from 8 to 24 weeks, depending on the protocol used and the length of follow-up [20, 21, 23].

Crossover studies reported that differences between interventions were mainly observed during the first 8 to 16 weeks after administration [21]. In trials with follow-up periods of up to six months, the evaluated outcomes were reported through the final assessment time point [18, 22].

Dose–response relationship

Clinical trials comparing different dosing regimens reported outcomes for total BoNT-A doses ranging from 40 to 100 units [16, 17, 24]. Pain and functional outcomes were presented according to each dose group, as described in the individual studies, without standardization across the evaluated protocols.

Adverse events

Adverse events were reported in BoNT-A–treated groups in several of the included studies. The reported events included transient muscle weakness, smile asymmetry, headache, fatigue, and reductions in electromyographic activity of the masticatory muscles [19, 21, 23]. Isolated cases of mild dysphagia and temporary paralysis of mimetic muscles were also reported [18]. No study reported serious or permanent adverse events during the follow-up period [16, 20, 25].

Risk of bias analysis using the rob-2 tool

The risk of bias of the included randomized clinical trials (Fig. 2) was assessed using the Cochrane Risk of Bias 2 (RoB-2) tool, considering the domains of the randomization process (D1), deviations from intended interventions (D2), missing outcome data (D3), measurement of outcomes (D4), and selection of the reported result (D5).

Most studies were judged to have a low risk of bias in the domain of missing outcome data (D3). In the domains of deviations from intended interventions (D2), measurement of outcomes (D4), and selection of the reported result (D5), a predominance of some concerns was observed, mainly due to limitations related to blinding, the use of self-reported outcomes, and the absence of previously registered protocols.

In the overall judgment, most randomized clinical trials were classified as having some concerns regarding risk of bias, while a smaller number of studies were judged to have a low overall risk of bias. No study was classified as having a high overall risk of bias according to the RoB-2 criteria.

Discussion

The present systematic review critically evaluated the clinical effectiveness, duration of effect, and dosage parameters of botulinum toxin type A (BoNT-A) in the management of myogenous temporomandibular disorders. Overall, the included randomized clinical trials indicated that BoNT-A may promote pain reduction and, in specific contexts, improvement in mandibular function; however, these benefits were not consistent nor systematically superior to those observed with placebo or conservative therapies, particularly in non-refractory populations [20, 21, 23].

Pain reduction was the most frequently assessed outcome and occurred similarly in both BoNT-A-treated groups and control groups. Multicenter placebo-controlled trials reported significant pain reduction in both arms, with no statistically significant differences between the toxin and saline injections [20, 21]. Comparable findings were observed in crossover studies, in which pain improvement occurred regardless of the active intervention, indicating that neuromuscular blockade alone does not fully account for the observed analgesic effects [21].

In contrast, studies conducted specifically in populations with refractory myofascial pain reported greater benefit of BoNT-A compared with placebo. Approximately 50% pain reduction was described, accompanied by a significant increase in pressure pain thresholds, with maintenance of the effect for up to six months [18]. Similar findings were reported in additional studies involving patients with persistent pain, in which a more pronounced clinical response to BoNT-A was observed compared with placebo [19, 24].

Regarding mandibular function, several studies reported improvements in maximal mouth opening and self-reported functional parameters following BoNT-A administration, particularly at medium-term follow-up [22, 24]. However, these functional gains were not universally superior to those achieved with placebo or conservative therapies, such as occlusal splints or acupuncture [19, 23]. Moreover, studies that included objective assessments, such as electromyography and bite force, demonstrated a significant reduction in muscle activity following BoNT-A use [19, 21]. Although this effect is expected from a pharmacological standpoint, it raises concerns regarding potential negative impacts on masticatory function, especially when higher doses are administered or when repeated applications are performed.

The duration of the clinical effect of BoNT-A varied considerably among the included studies. In randomized clinical trials, therapeutic benefits were generally maintained for 8 to 24 weeks, with peak effects occurring between 8 and 16 weeks, followed by a gradual decline [20, 21]. Studies with follow-up periods of up to six months reported maintenance of analgesic and functional outcomes in a subset of patients, particularly those with refractory pain [18, 22]. Reports of sustained effects over longer periods were limited to observational studies or case reports, which represent low-level evidence and do not allow for clinical extrapolation.

The available evidence was insufficient to establish a clear dose–response relationship. Only a limited number of studies directly compared different dosing regimens, and substantial heterogeneity in toxin formulations, injected muscles, dose distribution, patient populations, and outcome assessment limited reliable comparisons. Trials using total doses ranging from 40 to 100 units reported similar improvements in pain and functional outcomes, without consistent superiority of higher doses [16, 24]. These findings indicate that increasing the dose does not necessarily translate into greater clinical benefit and may be associated with an increased risk of muscle-related adverse effects.

Adverse events were reported with moderate frequency in BoNT-A–treated groups and were predominantly mild to moderate in severity. The most commonly reported events included transient muscle weakness, facial asymmetry, headache, fatigue, and significant reductions in electromyographic activity of the masticatory muscles [19, 21, 23]. The occurrence of these events appeared to be related to the total dose administered, the number of muscles injected, and the repetition of applications. No serious or permanent adverse events were reported in the included randomized clinical trials [16, 20, 25].

In summary, the available evidence indicates that botulinum toxin type A should not be recommended as a first-line treatment for myogenous temporomandibular disorders. Its use may be considered in refractory cases after failure of well-established conservative therapies and within a multimodal treatment approach. Heterogeneity in application protocols, variability in outcome measures, and a predominance of trials classified as having some risk of bias limit the robustness of the conclusions. Future randomized clinical trials with more rigorous methodological designs, protocol preregistration, standardized dosing regimens, and long-term follow-up are necessary to more precisely define the role of BoNT-A in the management of myogenous temporomandibular disorders.

The findings should be interpreted considering the substantial clinical and methodological heterogeneity among the included studies. Differences in diagnostic criteria, patient populations, injected muscles, toxin formulations, doses, comparators, and follow-up periods may have influenced treatment effects. In particular, studies involving refractory myofascial pain may not be directly comparable with trials including broader or less severe myogenous temporomandibular disorder populations. In addition, botulinum toxin units are formulation-specific and should not be considered directly interchangeable. Variability in injection protocols and outcome assessment also limited direct comparisons, precluded meta-analysis, and reduced the certainty and generalizability of the evidence.

Conclusion

This systematic review indicates that botulinum toxin type A (BoNT-A) may reduce pain and improve mandibular function in patients with myogenous temporomandibular disorders, particularly in selected cases with refractory symptoms. However, across randomized clinical trials, the magnitude and consistency of these effects were variable, and BoNT-A did not demonstrate clear or consistent superiority over placebo or established conservative therapies in non-refractory populations.

The clinical effects of BoNT-A were generally reported to persist for short- to medium-term periods, most commonly between 8 and 24 weeks, with current evidence is insufficient to determine whether a clinically relevant dose–response relationship exists across the evaluated regimens.

Adverse effects associated with BoNT-A were relatively frequent but predominantly mild to moderate and transient, with no serious or permanent events reported in the included trials. Nevertheless, the consistent reporting of muscle-related side effects highlights the need for cautious patient selection and judicious use of this intervention.

Overall, the current evidence does not support the routine use of BoNT-A as a first-line treatment for myogenous temporomandibular disorders. Its application may be considered as an adjunctive or second-line option in carefully selected patients who do not respond adequately to conservative management, preferably within a multimodal treatment framework. Further high-quality randomized clinical trials with standardized protocols, preregistered methodologies, and longer follow-up periods are required to more precisely define the role of BoNT-A in the management of myogenous temporomandibular disorders.

Supplementary Information

Supplementary Material 1. ^{(16.8KB, docx)}

Authors’ contributions

All authors contributed substantially to the conception and design of the study. Study selection, data extraction, and risk of bias assessment were performed independently by the reviewers. All authors contributed to data interpretation, drafting, and critical revision of the manuscript, and approved the final version.

Funding

The authors received no specific funding for this study.

Data availability

All data generated or analyzed during this study are included in the published articles selected for this systematic review. Additional information is available from the corresponding author upon reasonable request.

Declarations

Ethics approval and consent to participate

Not applicable. This study is a systematic review based exclusively on previously published data and did not involve human participants or animals directly.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.