Bruxism (teeth grinding)
Pathophysiology and mechanisms
Bruxism results from a complex interaction between the central nervous system, masticatory muscles, and external trigger factors. its understanding has considerably evolved over the past two decades:
- Sleep bruxism is classified as a sleep-related movement disorder. It primarily occurs during light sleep stages (N1 and N2) and during transitions between sleep cycles, in the form of bursts of rhythmic masticatory muscle activity (RMMA).
- Dopaminergic and serotonergic neurotransmitters play a central role in regulating masticatory muscle activity during sleep, explaining the link with certain medications that act on these systems.
- Awake bruxism is more associated with emotional regulation and stress management mechanisms, with a behavioral habit component often unconsciously reinforced.
- The forces exerted during bruxism can reach 250 to 400 kg/cm², far exceeding normal chewing forces (20 to 40 kg/cm²), explaining rapid tooth wear and muscle pain.
- Genetic susceptibility is established: twin studies show significant heritability of sleep bruxism, independent of environmental factors.
Causes and risk factors
Bruxism is multifactorial. No single cause explains it on its own, but several factors increase the risk or worsen its severity:
| Category | Associated factors | Assumed mechanism |
|---|---|---|
| Psychosocial | Chronic stress, anxiety, perfectionist personality, emotional hyperactivity, stress-related sleep disorders | Activation of the sympathetic autonomic nervous system increasing muscle tone; unconscious emotional regulation behavior |
| Medicinal | Selective serotonin reuptake inhibitors (SSRIs: fluoxetine, sertraline, paroxetine), serotonin-norepinephrine reuptake inhibitors (SNRIs), antipsychotics, methylphenidate (Ritalin) | Disruption of dopaminergic and serotonergic pathways modulating oral motor activity during sleep |
| Psychoactive substances | Excess caffeine, alcohol, tobacco, cocaine, ecstasy (MDMA), amphetamines | Central nervous system stimulation and disruption of sleep architecture; direct effects on neurotransmitters |
| Sleep disorders associated | Obstructive sleep apnea (OSA), restless legs syndrome, sleepwalking, parasomnias | Repeated micro-arousals disrupting sleep architecture and promoting chewing muscle activity bursts |
| Neurological and psychiatric | Parkinson's disease, autism spectrum disorders, attention deficit hyperactivity disorder (ADHD), Rett syndrome | Dysfunction of dopaminergic circuits and basal ganglia involved in motor control |
| Genetics | Family history of bruxism in a first-degree relative | Estimated heritability between 50 and 60 % for sleep bruxism in twin studies |
| Dental occlusion | Malocclusions, ill-fitting dental restorations, posterior tooth loss | Historically overestimated role; current data does not support a direct causal link, but occlusal anomalies may aggravate pre-existing bruxism |
Clinical forms
Bruxism is distinguished by the time of onset and the type of muscular activity involved, each having its own characteristics and clinical implications:
| Shape | Time of occurrence | Type of activity | Key Features |
|---|---|---|---|
| Sleep bruxism | During sleep, mainly in N1-N2 phases and during cycle transitions | Rhythmic or tonic grinding of the teeth, often audible to the partner | Unconscious; patient often unaware until a loved one reports it or dental signs appear; bursts of 3 to 15 rhythmic contractions per episode |
| Wakeful bruxism | During waking hours, often during concentration, driving, or screen work | Teeth clenching without grinding in most cases (tonic bruxism) | Partially conscious; more readily accessible to behavioral interventions; direct link to stress and emotions |
| Mixed form | Simultaneous presence of both forms | Combination of nighttime grinding and daytime clenching | Dental and muscular involvement often more severe; combined management necessary |
Symptoms and clinical signs
Bruxism can remain silent for a long time or be revealed during a routine dental examination. Its manifestations affect several anatomical structures:
| Structural damage | Signs and symptoms | Features |
|---|---|---|
| Dents | Wear of occlusal and incisal surfaces, flattening of cuspid tips, tooth fractures, enamel fissures, dentinal hypersensitivity to cold and hot | Wear is symmetrical and affects multiple teeth simultaneously, unlike acid erosion which follows different patterns. |
| Masticatory muscles | Jaw pain and stiffness upon waking, visible masseter hypertrophy (jaw swelling), fatigue when chewing, partial trismus | Pain is typically at its worst in the morning with sleep bruxism; more at the end of the day with awake bruxism. |
| Temporomandibular joint | TMJ clicking or popping when opening and closing the mouth, limited mouth opening, preauricular pain on palpation | Bruxism is one of the main risk factors for temporomandibular dysfunction (TMD). |
| Headaches | Morning headaches, often presented as headbands or temporal pain, frequently mistaken for tension headaches | Result from the prolonged contraction of the temporalis and masseter muscles during the night |
| Dental support structures | Accelerated alveolar bone resorption, increased tooth mobility, gingival recession | Chronic occlusal overload transmitted to periodontal structures |
| Dental restorations | Frequent fractures of crowns, bridges, veneers, or dental implants; premature wear of fillings | Indirect sign often revealing during dental follow-up |
Diagnosis
The diagnosis of bruxism is primarily based on patient history and clinical examination. It is most often made by a dentist during a routine examination, and sometimes by a physician when a patient presents with morning headaches or chronic facial pain:
- Medical History: inquiry about symptoms, their timing (morning or evening), stress level, sleep quality, current medications, caffeine, alcohol, or tobacco consumption
- Sleep partner report: nighttime creaking noises, often the first sign reported
- Clinical dental examination: assessment of tooth wear using standardized indices (Basic Erosive Wear Examination, BEWE), screening for cracks, fractures, and hypersensitivity
- Palpation of the masticatory muscles: masseter, temporal, pterygoid; search for painful points, hypertrophy, or contractures
- Temporomandibular joint evaluation: mouth opening range (normal > 40 mm), joint sounds, pain on movement
- Validated questionnaires: Oral Behaviors Checklist for awake bruxism; sleep diary to identify associated factors
- Polysomnography with masseter electromyography: Gold standard for sleep bruxism, reserved for complex cases or research studies; rarely necessary in routine practice
- Ambulatory devices of the Bruxoff or BiteStrip type: less expensive alternatives to polysomnography for recording nocturnal electromyographic activity at home
- Sleep apnea screening if suggestive symptoms: snoring, daytime sleepiness, nocturnal breathing pauses reported by partner
Treatments
There is no single curative treatment for bruxism. Management aims to protect the teeth, reduce pain, identify and treat triggering factors, and modify associated behaviors:
| Treatment | Terms and conditions | Objectives and remarks |
|---|---|---|
| Occlusal splint (stabilizing splint) | Removable device made of hard acrylic resin, custom-made by the dentist, worn at night on the upper or lower jaw | Protects teeth from wear, reduces forces transmitted to the TMJ and muscles; does not eliminate bruxism but limits its damage; most common first-line treatment |
| Stress management techniques | Mindfulness meditation, progressive muscle relaxation, heart coherence, yoga, electromyographic biofeedback | Particularly effective in awake bruxism and forms associated with chronic stress; documented reduction in masticatory muscle activity |
| Cognitive Behavioral Therapy (CBT) | Identification and modification of thought and behavior patterns that promote teeth clenching; body awareness techniques | First-line treatment for awake bruxism; demonstrated efficacy in reducing the frequency of clenching episodes and associated pain |
| Botulinum toxin injections | Intramuscular injections of botulinum toxin type A into the masseters and sometimes temporalis muscles, repeated every 4 to 6 months | Reduces muscle contraction force and masseter hypertrophy; well-documented efficacy for tooth wear and pain; reserved for cases resistant to other treatments or with marked masseter hypertrophy. |
| Drug treatment | Low-dose clonazepam at bedtime (short-term efficacy), buspirone, clonidine, gabapentin; review or substitution of bruxism-inducing medications (SSRIs) | No medication has a formal indication for bruxism; pharmacological treatments are last-resort, short-term options due to side effects and risk of dependence. |
| Sleep apnea treatment | Continuous positive airway pressure (CPAP), mandibular advancement device | When bruxism is associated with sleep apnea, treating the apnea often significantly reduces nocturnal bruxism by normalizing sleep architecture. |
| Electromyographic biofeedback | Wearable devices that detect chewing muscle activity and emit an audible or vibratory signal to interrupt clenching episodes | Particularly suitable for awake bruxism; allows the patient to become aware of their behavior and actively modify it |
| Dental rehabilitation | Restoration of tissue loss with composite, crowns, or veneers after bruxism stabilization; occlusal equilibration if necessary | Does not treat bruxism but repairs its consequences; must be performed after implementing effective protection to prevent rapid recurrence of damage |
Bruxism in children
Bruxism frequently affects children, with an estimated prevalence between 15 and 40 % depending on age groups. Its pediatric particularities deserve to be known:
- Very common between 3 and 6 years old during the eruption of primary teeth, often benign and temporary
- Frequently associated with respiratory factors: mouth breathing, chronic allergic rhinitis, tonsillar or adenoid hypertrophy
- Link established with ADHD, autism spectrum disorder, and anxiety disorders in children
- The majority of children with bruxism during teething do not have it in adolescence: frequent spontaneous resolution without specific treatment.
- The occlusal splint is rarely indicated in children with deciduous or mixed dentition due to the continuous growth of the jaws.
- Trigger-oriented support: school stress management, treatment of ENT problems, sleep hygiene
Complications in the absence of treatment
Untreated bruxism can lead to progressive and sometimes irreversible consequences:
| Complication | Description | Onset time |
|---|---|---|
| Severe tooth wear | Irreversible loss of enamel and dentin that can expose the dental pulp, lead to intense pain, and require root canal treatments. | Months to years depending on the intensity of bruxism |
| Temporomandibular joint disorder (TMJD) | Chronic temporomandibular joint (TMJ) and masticatory muscle pain, limited mouth opening, persistent clicking; can become disabling. | Months to years; chronification possible |
| Fractures and tooth loss | Coronal or root fractures requiring extractions, compromising existing implants and prostheses | Variable; accelerated if malocclusion or weakened restorations |
| Chronic headaches | Daily or almost daily headaches due to persistent muscle tension in the temporalis and masseter muscles | Weeks to months for intense bruxism |
| Sleep quality impairment | Sleep fragmentation due to bruxism episodes, daytime sleepiness, chronic fatigue | Present from the first weeks in severe forms |
Certain situations related to bruxism warrant prompt medical or dental evaluation: intense acute jaw pain with inability to open or close the mouth (trismus), painful tooth fracture with pulp exposure, chronic and debilitating facial pain significantly disrupting sleep and daily activities, or suspected temporomandibular joint dislocation after an episode of intense yawning or chewing. These scenarios require urgent dental or medical care.
For any other bruxism symptoms such as morning jaw pain, recurrent headaches upon waking, or observed tooth wear, a consultation at Clinique Omicron allows for a comprehensive evaluation and referral to the appropriate professionals. In case of acute, uncontrollable distress, call 911 or go to the nearest emergency room.
Consult at Clinique Omicron
Clinique Omicron provides assessment for oro-facial pain, recurring morning headaches, and sleep disorders that may be associated with bruxism, at several service points in Quebec. A physician or a nurse practitioner (NP) can assess your clinical presentation, screen for associated sleep apnea, review medications that may induce or worsen bruxism, and refer you to a dentist specialized in temporomandibular joint dysfunctions, a psychologist for cognitive-behavioral therapy, or a sleep medicine specialist based on your profile. In-person and telemedicine consultations are available. To book an appointment at one of our service points in Montreal, on the South Shore, or elsewhere in Quebec, visit cliniqueomicron.ca.
The content of this page is provided for informational purposes only and is not intended to replace the advice of a qualified healthcare professional. Consult a physician for any symptoms, questions or decisions you may have regarding your health.
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