When one tooth looks longer than the others, the tooth itself has almost never grown; either the gum has moved down on that tooth, or the gum never finished moving up on the teeth beside it.
Those two situations look similar in the mirror and are entirely different underneath. One is a developmental pattern that is usually stable. The other can signal ongoing disease, trauma or a drifting tooth. Telling them apart is the step most online advice skips.
There is a third possibility worth holding from the start: the tooth that looks wrong may be the normal one.
Key takeaways
- Apparent tooth length is set by two separate things: the height of the gum margin, and the amount of tooth structure present.
- Altered passive eruption leaves the gum sitting on enamel, making those teeth look short and square, so a normally erupted neighbour looks long by comparison.
- Localised gum recession exposes root surface and can progress. Reported prevalence varies from roughly 40 to 100 per cent depending on how studies define and measure it.
- A tooth with nothing to bite against tends to over-erupt. Reported figures put supraeruption in unopposed teeth at roughly 70 to 85 per cent, with a commonly cited figure of 83 per cent.
- Swollen gums shorten the look of a tooth and healthy gums lengthen it, so appearance can change once inflammation settles, before anything cosmetic is considered.
- Not every exposed root can be covered. Where interdental bone or soft tissue has been lost, coverage potential is limited, and that is worth knowing before treatment is planned.
Start with the reference frame
People almost always point at the long tooth. In my experience it is worth looking at the short ones first. If two or three teeth in a row have gum sitting low on the enamel and look stubby, the tooth that erupted normally reads as too long even though nothing has happened to it.
That reversal changes the plan completely. If the odd tooth is the normal one, treating it would make the smile worse.
The gum never moved up: altered passive eruption
As teeth erupt, the gum margin normally migrates towards the cemento-enamel junction, the natural line where enamel meets root. Altered passive eruption is a failure to complete that migration, so the free gingival margin stays on enamel in the apical third of the crown. The clinical picture is short, square-looking clinical crowns and gingival zeniths at uneven heights.
Why it is usually stable
This is a developmental pattern rather than a disease process, so it does not generally get worse. It is diagnosed by probing to find where the enamel actually ends and by assessing the level of the underlying bone crest. That bone assessment matters, because it determines whether the gum can simply be recontoured or whether the bone has to be reshaped as well.
One thing to avoid: calling this a gummy smile and stopping there. Gummy smile is a description, not a diagnosis. Altered passive eruption, a highly mobile upper lip, vertical growth of the upper jaw and drug-induced gum overgrowth all look broadly similar and all need different treatment.
The gum moved down: localised recession
Recession is apical migration of the gum margin that exposes root surface. It is extremely common and it is more often localised than generalised. One cross-sectional study reported 63.9 per cent of cases as localised against 36.1 per cent generalised, which fits what walks through the door: one or two teeth affected, not the whole mouth.
Prevalence figures for recession are close to meaningless without a definition. Studies report anywhere from about 40 per cent to 100 per cent, largely because they differ on whether any recession counts or only one millimetre or more, and on how many tooth surfaces they examine.
What actually causes it
The literature groups causes as anatomical, iatrogenic, pathological and traumatic. That covers a thin gum phenotype, a tooth positioned outside the arch, a gap in the bone over the root, a high frenal attachment, little attached gum tissue, plaque-driven periodontal inflammation, forceful brushing, and poorly designed partial dentures or orthodontic appliances.
Whether hard brushing causes recession or simply speeds it up in a mouth that was already susceptible is genuinely contested. Thin tissue and a bony gap over the root are probably needed for it to happen at all. So this is not a matter of blaming yourself for brushing wrong. Our article on receding gums, their causes and treatment goes through the aetiology in more detail.
Why a single receding tooth deserves attention
Localised recession on one tooth can be the first visible sign of localised periodontitis, occlusal trauma or a tooth that is failing. Treating it as purely cosmetic risks missing that. If the recession has appeared over months rather than years, or the tooth is tender or mobile, it needs an examination rather than a cosmetic consultation. Our guide to the stages of gum disease explains what is being assessed.
Worn edges can lengthen or shorten a tooth
The other way to change apparent length is to change the tooth itself. Chipping, grinding and acid erosion shorten teeth, so an unworn neighbour looks longer. Less obviously, wear on one tooth can leave a flat, square edge that reads as a different length even when the measurement is similar.
Wear is progressive if the cause continues, which is why the cause matters more than the repair. Grinding, reflux and an acidic diet each behave differently, and we separate them in our article on attrition, erosion and abrasion. Building composite onto a worn edge without addressing the force that wore it is a short-lived plan.
Over-eruption when there is nothing to bite against
This one is very common and almost never mentioned in consumer content. A tooth with no opposing tooth tends to keep erupting. Reported prevalence of supraeruption in unopposed teeth runs from about 70 to 85 per cent, with 83 per cent commonly cited. Measured rates average around 0.14 millimetres per month, and roughly 24 per cent of unopposed teeth in one study had over-erupted by more than two millimetres. Unopposed upper teeth move more than unopposed lower ones.
Why the gap matters more than the drifting tooth
Those numbers make the practical argument better than any warning could. A missing tooth that is not replaced is not a static situation. The tooth opposite it slowly leaves its position, which then complicates replacing the missing tooth later, changes how the bite loads and can open food traps. If a tooth in your mouth is visibly longer and the tooth opposite it is missing, that is the likely explanation and it is worth acting on.
Rotation, tipping and orthodontic relapse
A tooth that has rotated or tipped presents its edge at a different angle, and a different angle reads as a different length. Long-term follow-up data indicate that only around 10 per cent of orthodontically treated cases still show clinically acceptable lower arch alignment ten to twenty years after retention stops, according to work published in the Australian Dental Journal.
That figure sounds like a failure of treatment. It is not. Lower incisor crowding also develops in people who never had braces, as a normal age change. So a tooth that has drifted is not automatically evidence that your orthodontics did not work, and the fair conclusion is about retention rather than blame.
Swollen gums change apparent tooth length
Gingival inflammation causes the papillae between the teeth to swell. A tooth flanked by two puffy papillae looks shorter and narrower where it emerges. When inflammation settles, those papillae shrink back and the tooth looks longer, sometimes noticeably so.
The important distinction is that inflammatory swelling is reversible and attachment loss is not. Which is why a professional clean and a few weeks of good home care is often the first step, not a cosmetic procedure. The appearance you are unhappy with may change once the tissue is healthy, and any cosmetic decision made before that is being made on the wrong picture.
Same appearance, different cause, different fix
| What is actually happening | Typical clue you can see | Usually gets worse over time | Type of treatment usually considered | Needs the cause managed first |
|---|---|---|---|---|
| Gum never finished migrating (altered passive eruption) | Neighbouring teeth look short and square, gum sits on enamel | No, usually stable | Gum contouring or crown lengthening, sometimes involving bone | Not usually, but the bone level must be assessed |
| Localised gum recession | Root surface visible, often sensitive, notch at the gum line | Can progress | Soft tissue grafting where coverage is feasible | Yes, brushing technique, plaque control, occlusion |
| Worn or chipped incisal edge | The edge looks flat or notched, other teeth worn too | Yes if grinding or erosion continues | Composite bonding or other restorative addition | Yes, grinding, reflux, acidic diet |
| Tooth over-erupted into a gap | The tooth opposite it is missing | Yes, slowly and steadily | Orthodontic intrusion, occlusal adjustment, or restoring the gap | Yes, the missing opposing tooth |
| Rotation or orthodontic relapse | Tooth turned or tipped, edge presents at a different angle | Often slowly | Orthodontics, then retention | Yes, a retention plan |
| Swollen gum around the neighbouring teeth | Red, puffy papillae, bleeding when brushing | Reversible if treated | Professional cleaning and home care first | Yes, and reassess appearance afterwards |
What can and cannot be covered
Recession is classified before treatment is planned, because classification predicts what coverage is realistic. The widely used Miller system runs from Class I to Class IV based on whether the defect extends past the mucogingival junction and whether interdental bone or soft tissue has been lost. Classes III and IV involve loss of interproximal attachment, and that limits how much root can be covered no matter how well the surgery is done.
What the literature reports
For favourable Class I and II defects, a coronally advanced flap combined with a connective tissue graft is reported in the literature to achieve mean root coverage of about 84.7 per cent, with complete coverage in around 51.8 per cent of cases. Adding a connective tissue graft is also associated with more stable results at five years than flap procedures alone.
Those are trial-condition results in selected cases. They are not a prediction for any individual mouth, and roughly half of even favourable cases do not achieve complete coverage. Being told that honestly before surgery is more useful than being told afterwards. Our page on gum graft surgery covers what the procedure involves.
It is also worth saying that gums do not grow back. Inflammatory swelling settling down is not regeneration, and the two get conflated constantly online. Oil pulling, aloe vera, coconut oil and gum regrowth toothpastes do not regenerate lost attachment.
Sequencing: why gum levels are settled first
If gingival heights are asymmetric, the tissue contours are corrected before any restorative work. Otherwise a veneer or a composite build-up is designed to the wrong proportions, and the only way to fix it afterwards is to redo it.
A typical order of operations
Inflammation is treated first so the tissue is stable. The cause of any recession or wear is identified and managed. Gum levels are then corrected if they need to be, whether by contouring, crown lengthening or grafting, and given time to mature. Only then is the tooth shape addressed with bonding or another restoration, and orthodontics is slotted in wherever the position of the tooth is the real problem. Crown lengthening in particular is not simple gum trimming. It frequently involves recontouring bone, and describing it as a quick tidy-up misrepresents what is involved. Our crown lengthening guide sets out the detail.
Common questions
Why does one of my front teeth look longer than the other?
Usually because the gum sits at a different height on that tooth, either because it has receded there or because it never finished migrating on the neighbouring teeth. Less commonly the tooth has over-erupted, rotated, or the teeth beside it have worn down. An examination distinguishes these, and the distinction changes the treatment.
What causes an uneven gum line?
The two broad causes pull in opposite directions. Altered passive eruption leaves the gum too far towards the biting edge on some teeth and is generally stable. Recession moves the gum towards the root on others and can progress. Tooth position, thin tissue and inflammation all contribute as well.
Why is my gum receding on one tooth only?
Localised recession usually reflects something specific to that tooth: it may sit outside the arch, have thin tissue or a gap in the bone over the root, take an unusual share of the biting force, or have a frenum pulling on the margin. It can also be an early sign of localised periodontal breakdown, which is why one receding tooth is worth assessing rather than watching.
Can a tooth move if the one opposite it is missing?
Yes, and it commonly does. Reported figures put over-eruption in unopposed teeth at roughly 70 to 85 per cent, moving at an average of around 0.14 millimetres per month in one study. That is why leaving a gap indefinitely tends to make future treatment more complicated rather than simpler.
Can gum grafting cover an exposed root completely?
Sometimes. In favourable Miller Class I and II defects the literature reports mean coverage around 84.7 per cent and complete coverage in about half of cases. Where interdental bone or soft tissue has already been lost, complete coverage may not be achievable. Any honest plan sets that expectation before surgery rather than after.
Get it looked at before deciding what to do
A tooth that looks longer than its neighbours is worth understanding before it is treated, because the same appearance has causes with opposite prognoses. The team at Lumi Dental in Melrose Park can assess the gum levels, check whether anything is progressing, and explain which part is cosmetic and which is not. A general check-up and examination is the sensible start, and you can see what is currently available for new patients on our current offers page.
This article is general information only and is not a substitute for an examination. Gum and tooth conditions vary widely between people, so please speak with a dental practitioner about your own situation.
