Botox for Bruxism: Pain Relief and Jawline Refinement
Bruxism—involuntary clenching or grinding of the teeth—affects approximately 22% of the global population, according to a meta-analysis published in the Journal of Clinical Medicine in 2024. It causes jaw pain, tension headaches, tooth wear, and over time, visible thickening of the masseter muscles that widens the lower third of the face.
Botulinum toxin type A injected into the masseters (and, when necessary, into the temporals) offers a dual benefit that no other non-surgical treatment can match: it reduces the muscle contraction force that causes damage and simultaneously progressively refines the jawline by decreasing the volume of the hypertrophied muscle. If you want to first understand what botulinum toxin is and how it works at the molecular level, consult our guide on botox.
In summary
- Dual benefit in a single treatment: relief from bruxism (pain, clenching, headaches) + aesthetic jawline refinement.
- Usual dosage: 25-50 units of Botox (Allergan) per side in masseters; 15-20 additional units per side if temporals are included.
- Timeline: pain relief in 1-2 weeks; visible jawline refinement in 4-8 weeks.
- Duration: 3-6 months per session. After 2-3 cycles, the muscle "retrains" and intervals typically lengthen.
- Complement, not competition: botox reduces muscle force; a dental guard protects enamel. Using both together maximizes results.
What is bruxism?
Bruxism is a repetitive parafunctional activity of the masticatory muscles manifested as clenching or grinding of the teeth. It is classified into two types with distinct mechanisms:
- Sleep bruxism (nocturnal): involuntary rhythmic movements during micro-arousal phases of sleep. Global prevalence is estimated at 21%.
- Awake bruxism (diurnal): sustained, unconscious clenching during the day, frequently associated with stress, anxiety, or concentration. Prevalence is estimated at 23%.
Many patients experience both types simultaneously.
Consequences of untreated bruxism
Normal bite force ranges between 70 and 100 kg. In bruxist patients, repetitive and sustained contractions generate:
- Progressive tooth wear: enamel fracture, cracks, loss of clinical crown height.
- Myofascial pain: trigger points in masseters and temporals that radiate toward temples, ears, and neck.
- Chronic tension headache: referred pain from the masticatory muscles is one of the most frequent causes of morning headaches.
- Temporomandibular disorder (TMD/TMJ): joint pain, clicking, limited mouth opening.
- Masseter hypertrophy: increased muscle volume from overuse visibly widens the mandibular angle, giving the face a more square shape.
- Damage to restorations: fractures of crowns, veneers, and fillings; loosening of implants.
- Gingival recession: excessive pressure can contribute to gum retraction.
Who is a candidate for botulinum toxin treatment?
The best candidates include patients with:
- Jaw pain or headache associated with bruxism that does not respond adequately to occlusal guard.
- Masseter hypertrophy with aesthetic widening of the jawline.
- History of repeated tooth fractures or restoration damage from clenching.
- TMD symptoms (pain, clicking, limited opening).
- Awake bruxism, where a nighttime guard does not cover hours of daytime activity.
- Desire for surgical-free refinement of the lower third of the face.
How does botox work for bruxism?
Botulinum toxin type A blocks the release of acetylcholine at the neuromuscular junction, producing a partial and controlled relaxation of the injected muscle. In the context of bruxism, this translates into a reduction in contraction force—not total paralysis—that allows normal chewing but prevents excessive involuntary contractions.
A randomized clinical trial published in Cureus (2022) demonstrated that even low doses of botulinum toxin in the masseter significantly reduce muscle electromyographic activity and pain scores two weeks after injection, with sustained effect for three months.
The mechanism goes beyond simple muscle relaxation. Botulinum toxin also:
- Reduces nociceptive substances such as substance P and serotonin released by muscle fibers under sustained contraction, contributing to pain relief.
- Interrupts the feedback circuit of the trigeminal motor nucleus that perpetuates the bruxism pattern.
- Produces controlled muscle atrophy: by reducing activity, the muscle gradually loses volume (up to 30% according to ultrasound studies), which explains the jawline refinement effect.
If you are interested in learning about the differences between the different brands of botulinum toxin available (Botox by Allergan, Dysport by Galderma, among others), you can consult our comparison of botox brands.
The muscles involved: masseter and temporal
Masseter muscle
The masseter is the primary muscle of mastication and the protagonist of bruxism. It is a rectangular, powerful muscle located at the angle of the jaw, easily palpable when clenching teeth. Its hypertrophy from overuse is the primary cause of lower jaw widening in bruxist patients.
Injection of the masseter is sufficient for most patients and is what produces the aesthetic benefit of jawline refinement.
Temporal muscle
The temporal is a fan-shaped muscle that occupies the temporal fossa (the temple area) and contributes significantly to jaw closure. In some patients, the temporal is a greater contributor to bruxism than the masseter itself, especially when pain is concentrated in the temples or upper jaw area.
When are both muscles injected?
Temporal injection is added when:
- Pain is localized predominantly in the temporal area (temples).
- Palpation of the temporal reproduces pain or reveals marked hypertonia.
- Treatment of the masseter alone has not provided sufficient relief in a previous cycle.
- Electromyography or clinical examination reveals hyperactivity of both muscles.
A clinical trial comparing injection of masseters alone versus masseters plus temporals found that both groups reduced the intensity of bruxism contractions, and that treating both muscles offers a cumulative effect from the synergy between them during jaw closure.
The procedure step by step
The botulinum toxin injection session for bruxism is a brief outpatient procedure performed by an aesthetic or maxillofacial physician.
Pre-evaluation
The physician assesses:
- Clinical history of bruxism (type, duration, previous treatments).
- Palpation of masseters and temporals at rest and during contraction.
- Degree of masseter hypertrophy (visual and palpatory).
- TMD symptoms (clicking, limited opening, joint pain).
- Patient goals: functional (pain), aesthetic (refinement), or both.
Injection
- Duration: approximately 10-15 minutes.
- Injection points in masseter: 3-5 points distributed in the middle and lower third of the muscle, spaced ~1 cm apart. The upper third is avoided to not affect structures such as the parotid duct and facial nerve branches.
- Injection points in temporal (if applicable): 2-3 points in the anterior portion of the muscle, above the zygomatic arch.
- Pain: minimal. The needle is very fine (30-32G). Some physicians apply topical anesthesia or local cold, although many patients do not require it.
- Post-activity: normal life can be resumed immediately. It is recommended not to massage the treated area for 24 hours.
Usual dosages (Botox / onabotulinumtoxinA units)
| Muscle | Dose per side | Total bilateral dose | Indication |
|---|---|---|---|
| Masseter (pain/mild bruxism only) | 25 U | 50 U | Bruxism without significant hypertrophy |
| Masseter (bruxism + hypertrophy) | 30-50 U | 60-100 U | Bruxism with hypertrophy and/or aesthetic goal |
| Temporal (complementary) | 15-20 U | 30-40 U | Predominant temple pain or insufficient response to masseter alone |
Note on brands: Botox (Allergan) units and Dysport (Galderma) units are not interchangeable. The approximate equivalence is 1 U of Botox ≈ 2.5-3 U of Dysport. An experienced physician adjusts the dose according to the brand used, the degree of hypertrophy, and individual response. More details in our guide on botox brands.
Results: timeline of the dual benefit
Botulinum toxin for bruxism produces two types of results with different timelines, and it is important to understand both to have realistic expectations.
Functional benefit: pain and tension relief
| Time | Expected effect |
|---|---|
| Days 3-7 | Jaw tension begins to decrease. Some patients notice they clench less. |
| Weeks 1-2 | Significant reduction in jaw pain, morning stiffness, and headaches. Functional effect reaches its peak. |
| Months 1-3 | Sustained relief. Less tooth wear and reduced muscle fatigue. |
| Months 3-6 | Effect gradually diminishes as the neuromuscular junction regenerates. |
Aesthetic benefit: jawline refinement
| Time | Expected effect |
|---|---|
| Weeks 2-4 | The muscle begins to lose volume. Change is subtle and barely visible. |
| Weeks 4-8 | Jawline refinement becomes visible. Jaw appears more defined and less square. |
| Weeks 8-12 | Peak aesthetic effect. Ultrasound studies show up to 30% reduction in masseter thickness. |
| Months 4-6+ | Muscle gradually regains volume if treatment is not repeated. |
Why the difference in timelines?
Pain relief is fast because it depends on muscle relaxation (acetylcholine blockade), which occurs in days. Refinement is slower because it requires atrophy from disuse: a muscle that does not contract forcefully gradually loses mass, a physiological process that takes weeks.
Duration and maintenance frequency
- Each session lasts between 3 and 6 months, depending on dosage, individual metabolism, and bruxism severity.
- First year: most patients need 2-3 sessions, spaced every 3-4 months.
- Following years: as the muscle "retrains" (loses chronic hypertrophy), many patients manage to space sessions to every 6-9 months, or even discontinue them if bruxism remits.
Botox vs. dental guard: comparison
The occlusal guard (also called dental guard, night guard, or nightguard) and botulinum toxin are the two most commonly used treatments for bruxism. They do not compete with each other; they work at different levels, and the combination of both is usually the most comprehensive strategy.
| Characteristic | Dental guard | Botulinum toxin (masseters) |
|---|---|---|
| Mechanism | Physical barrier between dental arches | Reduction of muscle contraction force |
| Protects enamel | Yes (directly) | Indirectly (by reducing bite force) |
| Reduces muscle force | No | Yes (reduces bite force by 20-30%) |
| Relieves jaw pain | Partially | Yes (significantly in 1-2 weeks) |
| Reduces tension headaches | Variable | Yes |
| Refines jawline | No | Yes (in 4-8 weeks) |
| Daytime bruxism | Impractical (requires wearing guard during day) | Acts 24 hours without visible device |
| Need for patient adherence | High (must be worn every night) | Low (effect is automatic after injection) |
| Duration of effect | While in use; guard wears out in 2-3 years | 3-6 months per session |
| Side effects | Initial discomfort, drooling, long-term occlusal changes (debated) | Possible temporary difficulty chewing hard foods, mild facial asymmetry |
| Regulation | Medical device | Off-label use with strong clinical support (FDA approves toxin, but specific bruxism indication is off-label) |
When to choose each one?
- Guard alone: mild bruxism, predominantly nocturnal, without significant pain or hypertrophy. Patient is consistent with use.
- Botulinum toxin alone: bruxism with significant pain, masseter hypertrophy, awake bruxism (where guard is not practical), or patient who desires the aesthetic benefit of refinement.
- Both (combined strategy): moderate to severe bruxism. Toxin reduces muscle force and pain; guard protects enamel and restorations during sleep. A comparative clinical study found that botulinum toxin provided better overall results than guard alone, and that combination was not statistically superior to toxin alone in pain reduction, although it offers the added advantage of mechanical dental protection.
Regulatory and safety considerations
Botulinum toxin type A has FDA, EMA, COFEPRIS, ANVISA, and INVIMA approval for various therapeutic and aesthetic indications. Use in bruxism is considered off-label, meaning the molecule is approved, but this specific indication does not appear in the product information sheet. This is common in medicine: many well-supported clinical uses are off-label.
Possible side effects
Masseter injection has a favorable safety profile. Adverse effects are rare and transitory:
- Pain or bruising at injection site: mild, resolves in 1-3 days.
- Difficulty chewing very hard foods: possible for the first 2-3 weeks, especially with high doses. Resolves spontaneously.
- Mild transitory asymmetry: if toxin diffusion is not perfectly symmetric. Correctable in the next cycle.
- Asymmetric smile (rare): occurs if toxin migrates toward the risorius or zygomaticus muscle. Transitory and preventable with proper technique (injection in lower third of masseter, away from zygomatic arch).
A literature review published in Questiones Scientificae (2024) concluded that botulinum toxin injection in the masseter is a safe procedure with low complication rates, and that adverse effects, when they occur, are temporary.
The importance of the treating physician
The safety and efficacy of the treatment depend directly on the professional's training. A physician with experience in facial anatomy knows how to:
- Precisely locate safe injection points (middle-lower third of masseter).
- Avoid critical structures: parotid duct, facial artery and vein, facial nerve branches (VII cranial nerve).
- Adjust dosage to individual anatomy, degree of hypertrophy, and therapeutic goals.
- Select the appropriate brand and dilution according to clinical case.
Frequently asked questions
Does botox for bruxism hurt?
Discomfort is minimal. A very fine needle (30-32G) is used and the complete session takes 10-15 minutes with 3-5 punctures per side. Most patients describe it as a brief pinch at each point. If desired, topical anesthesia or local cold can be applied before injection, although many patients do not consider it necessary. Pain at the injection site, if it appears, resolves in one or two days.
How many botox units are needed for bruxism?
The usual dosage is 25-50 units of Botox (Allergan) per side in the masseters, for a total of 50-100 units bilaterally. Lower doses (25 U/side) are used when the main goal is to relieve pain without significant muscle atrophy. Higher doses (40-50 U/side) are indicated when there is marked hypertrophy or when aesthetic jawline refinement is desired. If temporals are also injected, 15-20 units per side are added. The physician adjusts dosage according to clinical examination, degree of hypertrophy, and response to previous sessions.
How long does botox in masseters take to work?
Functional relief (reduction in pain, less morning tension, fewer headaches) begins to be noticed between days 3 and 7, with full effect in 1-2 weeks. Aesthetic jawline refinement is more gradual: visible change appears between weeks 4 and 8, with peak aesthetic result at 8-12 weeks. This difference is because muscle relaxation is fast, but muscle atrophy (volume loss) requires weeks of decreased activity.
How long does the effect of botox for bruxism last?
Functional effect lasts between 3 and 6 months per session. During the first year, 2-3 sessions are usually needed every 3-4 months. Over time, many patients notice that intervals lengthen because the muscle loses its chronic hypertrophy and "unlearns" the pattern of excessive contraction. Some patients with mild bruxism manage to space sessions to 6-9 months after the first year.
Does botox in masseters affect chewing?
Botulinum toxin reduces excessive contraction force, it does not eliminate it. Normal chewing is maintained because a dose is injected that partially relaxes the muscle, not completely paralyzed it. During the first 2-3 weeks, some patients report that chewing very hard foods (fibrous meat, nuts, gum) requires a bit more effort. This effect is transitory and resolves spontaneously as the patient adapts.
Does botox for bruxism slim the face?
Yes, and this is the dual benefit of the treatment. By reducing the activity of the hypertrophied masseter, the muscle gradually loses volume (ultrasound studies report up to 30% reduction in thickness). This produces refinement of the mandibular angle and lower third of the face. The effect is more noticeable in patients with marked masseter hypertrophy (square jawline from muscle overuse). Refinement does not modify bone structure; it only reduces the volume of the overlying muscle.
Are dental guard and botox opposite treatments?
No, they are complementary. The guard creates a physical barrier that protects enamel and dental restorations during sleep. Botulinum toxin reduces the muscle force that causes damage. Together, the combination protects teeth (guard) while treating the muscle cause of bruxism (toxin). Many specialists recommend using both in moderate to severe bruxism, especially if there is significant investment in dental restorations.
Does botox cure bruxism or just control it?
Botulinum toxin controls symptoms; it does not eliminate the central cause of bruxism (which may be multifactorial: stress, sleep disturbances, neurological factors). However, the effect is more than palliative: by interrupting the cycle of muscle hyperactivity for months, the pattern of excessive contraction can be partially "unlearned." That's why many patients manage to progressively space sessions. Comprehensive bruxism management may also include stress control, sleep hygiene, and, when indicated, occlusal guard.
Can Dysport be used instead of Botox for bruxism?
Yes. Both Botox (onabotulinumtoxinA, Allergan) and Dysport (abobotulinumtoxinA, Galderma) are botulinum toxin type A with demonstrated efficacy. The main difference is unit equivalence: 1 unit of Botox is approximately equivalent to 2.5-3 units of Dysport. An experienced physician selects the brand based on availability, desired diffusion profile, and clinical experience, adjusting the equivalent dose. Both brands have FDA and COFEPRIS approval.
Is botox treatment in masseters safe?
The safety profile is favorable when the procedure is performed by a physician trained in facial anatomy and experienced in injectables. A literature review (2024) concluded that the complication rate is low and adverse effects are transitory: mild pain at injection site, possible temporary difficulty chewing hard foods, and rarely transitory facial asymmetry. No serious systemic effects have been reported with doses used in bruxism. The key is injection technique (safe points in the middle-lower third of the masseter) and use of genuine products with current regulatory registration (FDA, COFEPRIS, EMA, ANVISA).
Can bruxism return after botox?
Yes, because botulinum toxin has a temporary effect (3-6 months). As the neuromuscular junction regenerates, the muscle regains its contraction capacity and bruxism may reappear. This is why a maintenance plan is recommended, especially during the first year (2-3 sessions). The good news is that with regular sessions, masseter hypertrophy is reduced sustainably, and many patients experience a gradual decrease in bruxism severity, which allows spacing treatments over time.
From what age can botox be applied for bruxism?
Botulinum toxin for bruxism is applied in adult patients (generally from 18 years old). There is no upper age limit as long as the patient has no contraindications (neuromuscular diseases such as myasthenia gravis, pregnancy, breastfeeding, allergy to formula components). Most patients treated in clinical studies are in the 18-50 year age range, which is the group with the highest prevalence of symptomatic bruxism.