Why do teeth shift?

Because teeth are not rigidly fixed to bone. They are suspended in it, by a ligament designed to allow movement.

Given how securely teeth feel attached, it seems impossible that they can move without braces. In fact several factors cause inadvertent movement, and that shift can create problems in the bite that lead to further issues — what is malocclusion of the teeth? and treatment of malocclusion describe where that ends up.

How teeth are attached

Teeth are attached to the jaw by the outer layer of the root, called cementum, and by ligaments called the periodontal ligaments. Those ligaments are made of collagen fibres — strong, but flexible, which is precisely why teeth are subject to movement.

That flexibility is a feature, not a flaw. It lets teeth absorb chewing forces without fracturing, and it is the mechanism orthodontics exploits: sustained gentle pressure causes bone to remodel around the tooth, and the tooth moves. The same mechanism operates without an appliance, driven by whatever forces are actually present. How long does it take to have orthodontic treatment? is, in effect, a question about how fast that remodelling can safely be pushed.

Ageing and normal drift

Throughout life, the natural ageing process causes some degree of tooth movement. Certain triggers and stresses increase it — clenching and grinding most notably. See night time tooth grinding and clenching, what is bruxism and how is it managed? and TMD and teeth grinding.

With age comes an increasing likelihood of mesial drift: teeth slowly moving toward the front of the jaws, so they appear tipped forwards. This is the usual explanation for the lower front tooth crowding that appears in the thirties and forties, including in people who had braces as teenagers. Teeth and aging: how can I keep my smile looking younger? and I am in my late 60s — how can I keep my teeth in top condition now that I am older? cover the wider set of changes it arrives with.

Mesial drift is more pronounced where teeth are missing, because the gaps allow movement without neighbouring teeth to stop it. That can become a serious problem: it creates imbalances in the bite, and it makes cleaning difficult, raising the risk of decay and gum disease.

This is a large part of the argument for replacing a missing back tooth even when the gap does not show. The teeth either side tilt into the space, the opposing tooth over-erupts, and the bite gradually reorganises around the absence. What are the replacement options for missing teeth? sets out the options and the cost of waiting; bridges, implants, or dentures for replacing missing teeth?, dental bridges and dental implants go into each. The bone under a gap resorbs while you wait, which is why bone grafting becomes necessary in cases that were once straightforward.

Wear and erosion

Tooth wear and erosion also cause shifting. The mechanism: losing tooth structure alters the shape of the teeth, and so alters how they meet. The periodontal ligaments and jaws compensate for the lost structure through movement, closing the space that the wear created. See what is dental erosion and how is it addressed?, I’ve heard a lot about acid wear — what is this and how can I avoid it? and how does acidic food affect your teeth?.

By the same phenomenon, teeth shift in response to:

• A filling that does not fit the bite properly — which is why a new filling that feels high should be adjusted rather than tolerated. See tooth fillings, why do I bite my cheek after a filling? and how long do dental fillings last?.
• Bruxism

Crooked and crowded teeth

Crooked, misaligned and crowded teeth are themselves a factor, through a self-reinforcing loop:

1. Crowding traps plaque and bacteria in places that are difficult to clean — is flossing really that important? and what is the ideal daily routine for oral hygiene?
2. That raises the risk of gum disease and decay — periodontal (gum) disease, bleeding gums and how do I prevent dental decay?
3. An uneven bite raises the risk of tooth fracture — why does a cracked tooth hurt so much? and chipped and cracked teeth
4. Gum disease weakens the support, and lost or damaged teeth create space — when do you need deeper cleaning?
5. More shifting follows

Breaking that loop at any point slows the rest.

Gum disease: the shifting that is not ordinary drift

The movement caused by periodontal disease is a different process from ageing drift, and it is the one worth catching early.

Periodontal diseases divide into gingivitis, in which the inflammation is confined to the gum and is reversible with good oral hygiene, and periodontitis, in which the inflammation extends and produces tissue destruction and resorption of the bone around the tooth. In periodontitis, that destruction results in breakdown of the collagen fibres of the periodontal ligament — the same fibres described at the top of this page — forming a pocket between the gum and the tooth. (Source: Preshaw and colleagues, Periodontitis and diabetes: a two-way relationship, published in Diabetologia.)

Three consequences follow from that, and each is awkward in its own way.

The tissue destruction is largely irreversible. The same source describes periodontitis as slowly progressing but states that the tissue destruction which occurs is largely irreversible. Treatment arrests the process; it does not rewind it, which is why the timing of the diagnosis decides most of the outcome.

It is quiet until it is advanced. In the early stages the condition is typically asymptomatic — not usually painful — and many people are unaware of it until it has progressed enough to cause tooth mobility. Advanced periodontitis is characterised by gum redness and swelling, gum bleeding, gum recession, tooth mobility, drifting of teeth, suppuration from the pockets, and tooth loss. Teeth that have begun to drift, splay or space out in an adult mouth are on that list as a recognised feature of advanced disease.

It cannot be found by looking. The same source states that pocketing is not evident on simple visual inspection, and that assessment using a periodontal probe is essential. That is the millimetre-by-millimetre measuring done around each tooth at a check-up, and it is how the loss is detected before the movement starts. When do you need deeper cleaning? describes what follows if the probe finds pockets, periodontal (gum) disease the condition itself, and a specialist periodontist is involved where the bone loss is advanced.

What can be done

Some minor shifting is expected, even with routine examinations and professional cleans. Teeth move throughout life. The aim is to keep it within a range that does not cause problems, rather than to stop it entirely. How often should I go to the dentist?, dental cleans and hygienists and understanding your treatment cover the monitoring that tells drift from a developing problem.

Where alignment has become a problem, orthodontic treatment corrects the position of the teeth, and a specialist orthodontist can assess whether that is appropriate. See how do I know which orthodontic treatment is best for me?, braces, Invisalign and orthodontic treatment: general dentist vs specialist orthodontist?. Costs are covered in what is the cost of braces?, Invisalign cost in Melbourne: a complete breakdown by treatment type and the price guide.

Worth knowing what the treatment is for. The Australian Dental Association puts it this way: orthodontic treatment is not just about straight teeth — it can correct a bad biting pattern, help with sleep apnoea, and prevent uneven wear of the teeth (teeth.org.au, Teeth straightening and braces). Two of those three are the same mechanisms this page has been describing in reverse. See TMD and teeth grinding and, on the sleep side, snoring and sleep apnoea and exploring the link between sleep quality and oral health.

One important qualification the original version of this article overstated: orthodontics corrects alignment; it does not cure the tendency to shift. Teeth move for life, before and after treatment. What prevents relapse is retention — wearing a retainer indefinitely, or having a fixed retainer bonded behind the front teeth. Without that, teeth return toward where they were. Will my teeth need retainers after I’ve had braces? is the article devoted to that point, and how to protect your aligners and your smile covers looking after the appliance itself.

One approach to avoid. The Australian Dental Association does not recommend that Australians have DIY orthodontic treatment — the direct-to-consumer services that straighten teeth without an in-person visit to a dentist or orthodontist. Its stated concern is that these can lead to permanent damage to the teeth, gums and jaw joints, and its recommendation is in-person treatment, including a thorough assessment before starting and ongoing supervision (teeth.org.au, Teeth straightening and braces). That has particular force for teeth that have shifted for a reason nobody has yet established, because the assessment is the part that finds out why.

If it is a child’s teeth

The mechanisms above are adult ones. In a child the position of the teeth is still being established, and the Australian Dental Association lists past habits such as thumb sucking among the things orthodontics treats, on the basis that they affect both the position of the tooth and the development of the jaw bones. The Australian Society of Orthodontists recommends children have an orthodontic assessment between the ages of 7 and 10, and all the adult teeth do not have to be present for an assessment to be done — assessing at that age is what allows early intervention where it turns out to be needed (teeth.org.au). See children’s dentistry, when should I take my child to see an orthodontist? and how long does my child need to wear braces?

At home

• Limit acidic foods and drinks, to reduce erosion and the compensatory movement it causes — is soda water bad for your teeth? and what are sports drinks really doing to your teeth?
• Brush twice daily with fluoride toothpaste, along the gumline with gentle pressure — how much pressure should I apply when brushing my teeth?, over brushing: what can it do to my teeth? and the benefits of fluoride
• Clean between the teeth once daily — once is sufficient, and it is where crowding causes the most trouble
• Wear a night guard if you grind, which protects against both the wear and the loading that drives movement — what kind of mouth guard should I use? and how can a night guard be used to treat TMD?
• Wear your retainer, if you have had orthodontic treatment

Get it assessed if you notice

• Teeth that suddenly feel like they meet differently
• A new gap, or new crowding
• A tooth that feels loose
• Food catching where it never used to

Sudden mobility or rapid change is not ordinary drift — it can indicate gum disease, a cracked tooth, or a bite problem, and it is worth having looked at rather than watched. If it is painful as well, see what are the causes of toothache and what are their symptoms? and emergency dentistry.

Common questions

Are my wisdom teeth pushing my front teeth crooked?

This is the most common explanation people arrive with, and it is the one the evidence supports least. Everything described above — mesial drift, wear, missing teeth, ligament remodelling — happens in people who have no wisdom teeth at all, and the lower-front crowding that appears in the thirties is the same in both groups.

The trial evidence on removing them to prevent crowding is one small study. Cochrane's 2020 review (CD003879.pub5) of removing versus keeping asymptomatic, disease-free impacted wisdom teeth found only two studies in total. The single randomised trial — adolescents who had already had orthodontic treatment and had crowded wisdom teeth — analysed 77 participants at 66 months and was rated at high risk of bias. Its result on crookedness was not statistically significant: Little's index of irregularity 0.30 mm lower in the removal group, with a confidence interval running from 1.30 mm lower to 0.70 mm higher, at low certainty. The review's headline conclusion is that ‘insufficient evidence is available to determine whether asymptomatic disease-free impacted wisdom teeth should be removed or retained', and that ‘high-quality research is urgently needed'.

The formal guidance goes further. The UK's National Institute for Health and Care Excellence, in guidance issued in 2000, recommended that ‘the practice of prophylactic removal of pathology-free impacted third molars should be discontinued in the NHS', and that surgical removal ‘should be limited to patients with evidence of pathology' — decay that cannot be restored, untreatable pulp or periapical disease, cellulitis, abscess, osteomyelitis, resorption, fracture, cyst or tumour, or teeth in the field of jaw surgery.

So the practical position: if a wisdom tooth is diseased, that is its own reason to deal with it and it does not need the crowding argument. If it is healthy and symptom-free and removal is proposed only to stop your front teeth moving, ask what benefit is expected — and know that the answer sits on thin evidence. See wisdom teeth.

I grind my teeth. Will a night guard stop the movement?

It protects the surfaces. It does not stop the grinding, and the way grinding is understood has changed enough to be worth knowing about.

The 2025 international consensus convened under INfORM is explicit that bruxism is a behaviour, not a disease. Its wording: ‘bruxism is a motor behaviour rather than a disorder', and ‘bruxism is a motor behaviour that can be a risk factor, protective factor or neutral factor. Since it is a behaviour, it cannot be a comorbidity.' The older system of grading bruxism has been retired. That reframing matters here because it means there is nothing to cure — the question is only whether, in your mouth, the behaviour is doing harm.

On force, one measurement gives a sense of scale. A 2001 study of sleep bruxism by Nishigawa and colleagues recorded a mean amplitude of detected bruxism events of 22.5 kgf (standard deviation 13.0 kgf). That is the loading the wear-and-compensation mechanism described above is responding to.

What a removable night guard does is sit between the surfaces, so that what wears is the appliance rather than your enamel. That is a real benefit and it is why it appears in the home-care list above.

What is specifically advised against is the irreversible version. A 2023 BMJ clinical practice guideline on chronic temporomandibular disorders makes a strong recommendation against irreversible oral splints, alongside other invasive and irreversible procedures. And on the related question of whether your bite is the cause of jaw pain, the US National Academies concluded in 2020 that ‘occlusion should not be considered a contributing cause for the common TMDs', with the RACGP adding that malocclusion ‘does not contribute to the manifestation of TMD and orthodontic referral is not recommended for this finding alone'.

So: a removable guard to protect the teeth, yes. Permanently reshaping teeth or an irreversible splint to fix grinding is a different proposition, and one to question closely.

Does wearing an appliance for snoring move teeth?

Yes, it can — and that is a recognised, monitored risk rather than a rare surprise. The Australian Dental Association's policy on sleep-disordered breathing states at clause 2.4: ‘where there is long-term use of oral appliances, monitoring of the patient's temporomandibular joint function and orthodontic movement of teeth is essential.' The mechanism is exactly the one at the top of this page — a device that holds the lower jaw forward night after night is sustained gentle pressure, which is what moves teeth.

That is not an argument against the appliances. The same policy records that oral appliances ‘can be a first-line therapeutic option for adults with snoring and mild to moderate forms of Obstructive Sleep Apnoea', and may also be indicated for people with severe OSA who cannot tolerate CPAP.

It is an argument for who supervises it, and for expecting reviews. The ADA's position is that ‘initial diagnosis of Sleep Apnoea must be made by an appropriate medical practitioner', that medical and dental expertise are both required, and that ‘a team approach is essential'. It also notes that dental sleep medicine is not a recognised dental specialty.

If you wear one, ask specifically how your bite will be recorded and how often it will be checked. Movement caught early is manageable; movement noticed after three years is a bite that has quietly reorganised. See snoring and sleep apnoea.

My bottom front teeth have crowded up in my thirties and I had braces as a teenager. Did the braces fail?

No — and this is the single most common version of the question this page exists to answer. As set out above, teeth move throughout life, in people who have had orthodontic treatment and in people who never have. Mesial drift is the usual explanation for lower-front crowding appearing in the thirties and forties. Braces put teeth in a position; nothing about that position is self-maintaining.

What prevents relapse is retention, continued indefinitely — a removable retainer worn to a schedule, or a fixed wire bonded behind the front teeth. If you stopped wearing yours at nineteen, that is the likeliest explanation, and it is a very ordinary one.

Before assuming it is simple relapse, ask for the cause to be identified. Four things on this page produce the same appearance and need different responses: ordinary drift, a tooth lost or extracted elsewhere in the arch, wear that has changed how the teeth meet, and periodontal bone loss. The last of those is the one that must not be treated as cosmetic.

And if you are considering treating it, the sequence matters. Gum health is assessed before teeth are moved, not after — moving teeth through reduced bone accelerates the loss.

Teeth that have moved — how would I know whether it is gum disease?

You would not, by looking, and that is the whole difficulty. As the section above sets out, pocketing is not evident on simple visual inspection and assessment with a periodontal probe is essential. The disease is typically asymptomatic in its early stages, and many people are unaware of it until it has progressed enough to cause tooth mobility — by which point the bone loss has already happened.

It is common enough that ruling it out is not a formality. A review in Diabetologia reports that severe periodontitis affects 10–15% of adults in most populations studied, with moderate periodontitis affecting 40–60% of adults.

The features that should move this up your list, from the same source's description of advanced periodontitis: gum redness and swelling, bleeding, recession, tooth mobility, drifting of teeth, discharge from the gum, and tooth loss. Drifting teeth appear on that list as a recognised feature, not as an incidental one.

What is at stake in the timing is that the tissue destruction is largely irreversible. Gingivitis — inflammation confined to the gum — is reversible with good oral hygiene. Past that point, treatment arrests the process rather than reversing it. Ask for your pocket depths to be measured and recorded, and ask what they were last time; a number that is moving is the finding, not a number on its own.

Related reading

• What is the cost of braces?
• What causes TMJ pain and how is it treated?
• 10 ways to avoid ruining your teeth
• Second opinions and corrective dentistry

Practical details

Smile Solutions has general dentists and registered specialists, including orthodontists, who can assess and treat shifting teeth — see the full team and contact us.

Specialist registration can be verified on the AHPRA register, or by calling 1300 419 495.

Smile Solutions, Level 1, 220 Collins Street, Manchester Unity Building, Melbourne VIC 3000 — getting here. Phone 13 13 96, or theteam@smilesolutions.com.au. Monday–Friday 8.00am–6.00pm, Saturday 8.30am–1.30pm, Sunday by appointment.

Published 14 October 2020, by Dr Avi Aggarwal. General information only; it does not replace advice from your treating practitioner. Outcomes vary between individuals, and all treatment carries risks. Statements attributed to the Australian Dental Association, NICE, Cochrane, the National Academies, the RACGP and the journals named are those publishers' own.

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