General dentistry · Function
Bruxism: teeth grinding and clenching, and what they actually do
Grinding and clenching are rarely noticed by the person doing them. A partner usually notices first, and then the dentist does, through wear, cracks and fillings that keep breaking.
The short answer
Bruxism is repetitive jaw-muscle activity involving grinding or clenching of the teeth, occurring during sleep or while awake. It is not a disease in itself but a risk factor for wear, cracks and failure of restorations: in a retrospective study of 318 ceramic veneers, failure risk was 7.7 times higher in patients with bruxism.
Key points
- Bruxism is repetitive masticatory muscle activity, either grinding or clenching, and is distinguished into sleep bruxism and awake bruxism.
- In a retrospective study of 318 ceramic veneers followed for a mean of 118 months, failure risk was 7.7 times higher in patients with bruxism and significantly higher on non-vital teeth.
- A systematic review of 34 studies with at least 5 years of follow-up found that 90% of studies reported annual failure rates of 1 to 3% for Class I and Class II posterior composite restorations, with secondary caries and fracture the main causes.
- A night guard protects the teeth and restorations from the load but does not stop the muscle activity itself.
- The presence of bruxism changes the plan for aesthetic treatment but does not by itself rule it out.
What bruxism is and what it is not
Bruxism is repetitive activity of the masticatory muscles expressed as grinding of the teeth or clenching them. Current understanding is that in most otherwise healthy people it is a muscle behaviour rather than a disease in itself. Its significance comes from the consequences when it is frequent and sustained.
This article is explanatory. It does not establish whether you have bruxism, which is assessed at examination through the pattern of wear, questioning about symptoms, examination of the muscles and joint, and further investigation where needed.
The causes are multifactorial and are not fully understood. Sleep characteristics, stress and anxiety, certain medicines and substances, and general health conditions are all discussed. Simplified explanations, including those reducing everything to nerves or to crooked teeth, do not match current understanding.
Sleep bruxism and awake bruxism are different
Sleep bruxism occurs during sleep and typically involves rhythmic movement with an audible grinding sound. The person is usually unaware of it, and the information comes from outside, either from a partner or from the findings at an examination.
Awake bruxism is more often silent clenching, associated with concentration, tension or long stretches of work. It is easier to become aware of if a person starts noticing it deliberately during the day, and it sometimes responds to simple self-monitoring habits.
The distinction matters because the approach differs. A night guard addresses the night-time activity, while daytime clenching needs a different kind of attention. Both can be present at once.
What is visible in the mouth
The commonest findings are smoothed flat surfaces on incisal edges and cusps, sometimes with facets on upper and lower teeth that match each other exactly. Fine cracks in the enamel, chipped edges and increased sensitivity are also possible.
Associated complaints can include tension or fatigue in the chewing muscles, particularly in the morning, tooth sensitivity on waking, headache around the temples, and noises or restriction on opening the mouth. In some people the masseter, the muscle at the angle of the lower jaw, becomes visibly enlarged.
An important caveat belongs here. The same findings can have other causes. Acid erosion, wear from an aggressive brushing technique, joint problems and conditions affecting the musculature all produce a similar picture. A description is therefore not a diagnosis, and each of these findings is a reason for examination rather than a conclusion.
What bruxism does to restorations
Here the data are specific and worth attention, because they bear directly on planning. A systematic review and meta-analysis of 29 clinical studies reported ceramic veneer survival of 96.8% at a mean of 10.4 years for lithium disilicate, 96.1% for feldspathic and 93.7% for leucite-reinforced ceramic, with no statistically significant difference between materials.
In a retrospective study of 318 veneers followed for a mean of 118 months, survival was 94.4% at 5 years, 93.5% at 10 years and 82.9% at 20 years. In that same study, failure risk was 7.7 times higher in patients with bruxism and significantly higher on non-vital teeth. That is why we ask about grinding before discussing veneers.
For composite restorations the logic is similar. A systematic review of 34 studies with at least 5 years of follow-up found that 90% of studies reported annual failure rates of 1 to 3% for Class I and Class II posterior restorations, with secondary caries and fracture as the main causes. Increased loading plainly works against the second of those.
Night guards: what they do and what they do not
A night guard is an individually made hard or soft appliance worn during sleep. It distributes the load and places a protective layer between the upper and lower teeth, so that the wear affects the guard rather than the enamel and the restorations.
What it does not do matters as much: it does not stop the muscle activity and it does not treat the cause. It is protection rather than therapy for the behaviour. In patients with heavy loading it is therefore combined with monitoring rather than treated as a final answer.
The guard is made from an impression or a digital scan and needs adjustment and periodic checking. It is not a generic product, and off-the-shelf versions without individual fitting can alter the bite. Night guards have no published price and are quoted in writing after examination.
Botulinum toxin in masseter enlargement
Botulinum toxin is used in medicine to reduce the activity of the masticatory muscle in masseter hypertrophy. The mechanism is the same as in other indications: it temporarily reduces transmission of the signal from nerve to muscle, and muscle activity decreases for a period.
This is stated as clinical information and not as an offer. Botulinum toxin is a prescription-only medicine, and advertising such medicines to the general public is restricted in Bulgaria and across the European Union. There are therefore no trade names, no product descriptions and no prices here.
Whether such treatment is indicated at all is assessed by a doctor after examination, weighing the findings, any coexisting conditions, the contraindications and the alternatives. It does not replace protection of the teeth and is not used as a precaution.
What bruxism changes in the treatment plan
Grinding or clenching does not rule out aesthetic treatment, but it changes how the treatment is planned. More conservative solutions are considered where they are possible, material choice takes the loading into account, and a protective guard is planned as part of the treatment rather than as an optional extra afterwards.
Expectations change too. The frequency of chipping and of the need for adjustment is higher, and that should be said before treatment rather than after the first fracture. The same applies to the terms of any warranty commitments, which usually include wearing the guard and attending review appointments.
For extensive restorations and for crowns, assessment of function precedes aesthetics. A good-looking result placed over an unassessed function is a postponed problem.
When an examination is sensible
Sensible reasons include: a partner or family member has told you that you grind at night; you wake with tension or fatigue in the jaw; you notice smoothed or shortened tooth edges; your fillings break repeatedly; or you have increased sensitivity with no obvious cause.
At an examination we assess wear, the muscles and joint, the state of existing restorations and the bite, and where useful we take photographs and models so that comparison is possible later. Examination with diagnostics is 25 EUR.
Separately from bruxism: for severe facial or jaw trauma, rapidly increasing swelling, difficulty breathing or swallowing, or loss of consciousness, seek urgent medical care or call 112 rather than waiting for a dental appointment. General information about examinations is on the general dentistry page.
The Club awaits you
At an examination we assess wear, the muscles, the bite and the state of your restorations, and take baseline photographs for comparison. Examination with diagnostics is 25 EUR. Tel. +359 896 121 314.
What the evidence shows
96.8%
survival of lithium disilicate veneers at a mean 10.4 years
Systematic review and meta-analysis of 29 clinical studies (2025): 96.8% for lithium disilicate, 96.1% for feldspathic ceramic, 93.7% for leucite-reinforced glass ceramic, with no statistically significant difference between materials. In a retrospective study of 318 veneers, failure risk was 7.7 times higher in patients with bruxism.
Frequently asked questions
Frequently asked questions
Direct observation is missing, but there are indirect signs: tension or fatigue in the jaw on waking, tooth sensitivity in the morning, headache around the temples, and wear that is visible at examination. None of these proves bruxism on its own, because each has other causes. Assessment is therefore made at examination rather than from a description.
No. A guard protects the teeth and restorations by absorbing and distributing the load, but it does not reduce the muscle activity itself. It solves part of the problem, which is damage to the teeth, and is not treatment of the cause. It is therefore combined with monitoring and with discussion of the other factors that may be involved.
Ready-made versions are not individually fitted and, worn over a long period, can change tooth position and the bite. An individual guard is made from an impression or a digital scan, adjusted and checked periodically. If you already use a ready-made guard and notice a change in your bite, that is a reason to be examined.
Bruxism does not rule veneers out, but it changes the assessment and the expectations. In a retrospective study of 318 veneers, failure risk was 7.7 times higher in patients with bruxism. The decision follows assessment of function, discussion of more conservative alternatives, planning of a protective guard and clearly stated conditions for follow-up.
Stress and anxiety are among the factors associated with bruxism, but the cause is regarded as multifactorial and is not fully understood. Sleep characteristics, certain medicines and substances, and general health conditions are also discussed. Reducing everything to a single factor does not match current understanding of the condition.
The activity can vary across different periods of life and does not necessarily remain constant. That is not a reason to wait if wear, cracks or repeated fractures are already present, because lost tooth tissue does not regenerate. Monitoring with photographs and models shows whether the process is currently active.
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