Can Clear Aligners Fix a Gummy Smile? The Second Question Decides the Answer

Clear aligners can reduce a gummy smile in one situation: when the extra gum on show comes from upper front teeth sitting too low, usually alongside a deep bite. There, aligners intrude incisors by roughly 0.4 to 1.5 mm and express about 35% to 65% of the intrusion drawn in the digital plan, according to a 2025 systematic review of eight clinical studies in the Journal of Clinical Medicine. Aligners cannot shorten an upper lip, quiet a hyperactive lip muscle, uncover a crown the gum never released, or lower a tall upper jaw. So the question that settles your case is the second one: what is making your gum show?

I cover school absences for a living, and most of that job is refusing to let one word stand for four things. "Out sick" collapses exposure, symptom onset, a test result and a return date into one attendance code, and those four carry different dates and different rules. "Gummy smile" does the same work in a dental chair. It describes a photograph. Underneath it sit five conditions that appear alone or stacked, and the appliance that corrects one does nothing for another.

How much gum showing counts as a gummy smile?

No single cut-off is agreed, and the most-quoted sources disagree by about 2 mm.

The StatPearls chapter on excessive gingival display, last updated in March 2023, treats 1 to 2 mm of gum on show as normal and records definitions of "excessive" ranging from more than 2 mm to more than 3 or 4 mm. The perception study behind most of those numbers is Kokich, Kiyak and Shapiro in the Journal of Esthetic Dentistry in 1999, which altered smiling photographs in fixed increments and asked three groups to rate them. Orthodontists rated a gingiva-to-lip distance of 2 mm as noticeably less attractive. General dentists and lay people did not react until 4 mm.

A 2023 Scientific Reports study of 320 Saudi raters, 138 dental professionals and 182 lay people, put the same 4 mm image last, ranked least attractive by 81.1% to 90.6% of them.

How common is a high smile line? Tjan, Miller and The photographed 454 dental and dental hygiene students aged 20 to 30 for the Journal of Prosthetic Dentistry in 1984 and sorted every open smile into three types. A high smile, defined there as the full cervicoincisal length of the upper front teeth plus a contiguous band of gum, appeared in 48 people, or 10.57%. Split by sex, that was 13.79% of the 247 women and 6.76% of the 207 men, a statistically significant gap. If you have seen "14% of women and 7% of men" quoted with no citation attached, this 1984 table is where the pair started.

The reading is taken on a posed smile, in millimetres, from the gingival zenith of an upper central incisor to the lower border of the upper lip.

What is actually making your gum show?

Five causes, and they do not answer to the same treatment.

| Cause | What it is | How it is measured | Does aligner intrusion address it? | |---|---|---|---| | Dentoalveolar extrusion with deep bite | Upper front teeth erupted too far, overlapping the lower incisors heavily | Overbite in mm; a 2024 Angle Orthodontist trial used more than 4 mm as its entry criterion | Yes. The one target aligners can move | | Altered passive eruption | The gum never finished migrating apically, so part of the crown stays covered | Crown width-to-length ratio, 0.85 or above in a 2024 Saudi Dental Journal survey | No. The tooth is not low; the gum is high | | Hypermobile upper lip | The lip travels further than usual between rest and full smile | Lip length at rest minus at full smile; above 8 mm in the same survey | No | | Short upper lip | Less lip to cover the same teeth | Subnasale to the lower border of the upper lip; StatPearls gives 20 to 24 mm as the young-adult norm | No | | Vertical maxillary excess | The upper jaw itself is tall | Cephalometric height; a 2024 Journal of Periodontal and Implant Science study found 32.50 mm of anterior maxillary height in vertical-excess cases against 24.42 mm in altered-passive-eruption cases | No |

Prevalence figures for these causes swing wildly, and the reason is who got counted. Among 56 patients screened because they wanted their gummy smile treated, reported by Andijani and Tatakis in the Journal of Periodontology in 2019, hypermobile lip alone accounted for 45.3%, altered passive eruption alone for 20.8%, and both together for 34%. In a 2024 Saudi Dental Journal survey of 123 adults who answered an advertisement aimed at people with a gummy smile, altered passive eruption reached 73.2%, hypermobile lip 51.2% and vertical maxillary excess 45.5%; short upper lip appeared in nobody, and 55.3% carried more than one cause.

Compare a sample not selected for wanting treatment. Tatakis and colleagues examined 131 community adults for the same journal in 2024 and found hypermobile lip in 10.7% and altered passive eruption in 6.9%. Average upper lip length was 22.5 mm, average lip mobility 5.9 mm, and lip movement came out as the most consistent determinant of how much gum shows. Across all three samples a lip does much of the work, and most people arrive with more than one cause.

Where do clear aligners genuinely help?

On the dentoalveolar cause, and even there with a measurable shortfall.

The largest recent review is Husain and colleagues in Clinical Oral Investigations in 2025, which screened 829 studies and included 18. Bite opening ranged from 0.4 mm to 3.8 mm, and accuracy of deep-bite correction fell between 33% and 48.88%. The authors graded the evidence low quality and stated plainly that aligners are less effective than full fixed appliances for skeletal cases.

A 2026 scoping review in Frontiers in Dental Medicine puts anterior intrusion accuracy at 33.4% to 53.3% and separates the ages: adolescents achieved 63.5% of planned intrusion, worth 1.7 mm, while adults achieved 45.3%, worth 0.9 mm. Adults are the ones reading this page.

None of that is new. Kravitz and colleagues measured 401 anterior teeth in 37 patients for the American Journal of Orthodontics and Dentofacial Orthopedics in 2009 and found mean accuracy of 41%, with vertical movement worst: extrusion scored 29.6% overall and 18.3% for upper central incisors. A plastic shell grips a smooth crown and pulls along the tooth's long axis, the direction it has least purchase on.

Under-expression is why plans overcorrect: if the setup asks for 2 mm and half arrives, it has to ask for more than you need.

What does anterior intrusion cost in root length and in months?

Two currencies, and people underestimate the calendar.

On root length, a 2025 CBCT meta-analysis in BMC Oral Health pooled five studies and 334 participants. Upper central incisors lost 0.71 mm of root with aligners and 0.91 mm with fixed appliances, a gap that missed significance at p = 0.2422. Lateral incisors lost 0.63 mm and 0.84 mm, also not significant. Both sat under the 1 mm mark the authors used for clinical relevance, and they advised choosing an appliance on biomechanics rather than fear of resorption.

Anchored intrusion has sharper numbers because it has been trialled directly. In a 2024 randomized trial in the Angle Orthodontist, 43 adults with more than 3 mm of gingival display and more than 4 mm of overbite were intruded against one miniscrew or two. Over three months central incisors moved 1.55 mm with one screw and 2.09 mm with two, rates of 0.52 and 0.71 mm per month, at a root cost of 0.73 mm and 0.55 mm.

On the calendar, the honest reference is Kravitz and colleagues in the American Journal of Orthodontics and Dentofacial Orthopedics in 2023, who reviewed 500 patients averaging 33.6 years old. Aligner treatment lasted 22.8 months on average, 5.1 months longer than estimated at the consultation. Patients averaged 2.5 refinement scans and 64.1 aligners, and only 6.0% finished without a single refinement. One in six, 17.2%, switched to braces; that group averaged 80.6 aligners plus another 6.9 months in fixed appliances.

Two years, two extra scan appointments, and a one-in-six chance of braces anyway. Ask for those figures in writing.

Can braces correct a gummy smile better than aligners?

For the same dentoalveolar cause, braces have the better mechanical claim; for every other cause, the appliance question is beside the point.

| | Clear aligners | Fixed braces | Braces with miniscrews | |---|---|---|---| | Force delivery | A removable shell gripping crown and attachments | A rigid archwire in bonded brackets | A rigid wire pulled against a bone screw, not other teeth | | Anterior intrusion evidence | 33.4%-53.3% of plan; 0.9 mm in adults, 2026 scoping review | No head-to-head trial isolates gummy-smile intrusion | 1.55-2.09 mm over three months, 2024 Angle Orthodontist trial | | Main weakness | Vertical movement is its least accurate direction | Visible; tips teeth when anchorage is only other teeth | Surgical screw placement; root loss of 0.55-0.73 mm | | What it cannot change | Lip length, lip mobility, gum position, jaw height | The same four | The same four |

The bottom row is the one that matters. No appliance moves an upper lip up, slows the muscle that lifts it, migrates a gum margin apically, or shortens a maxilla. Choosing between brackets and trays after the wrong diagnosis only changes how long the disappointment takes.

What can aligners never change, and what can?

Three adjuncts do the work orthodontics cannot, each with its own arithmetic.

For a hypermobile lip, botulinum toxin is the tested option. A 2023 meta-analysis in the Journal of Clinical Medicine pooled 15 studies and reported a reduction of 3.22 mm at two weeks across 213 patients and 2.70 mm at three months across 182, using 1.25 to 7.5 units per side into the lip elevator muscles. It fades. Longer follow-ups in that review drifted back toward baseline around eight to nine months.

For altered passive eruption, the fix is periodontal. StatPearls sets the condition for gingivectomy alone at more than 3 mm of tissue between bone and gingival crest; where the crest sits too close to the cementoenamel junction, bone has to be recontoured too. That junction can lie up to 10 mm apical to the free gingival margin, against a normal crest 1 to 2 mm apical to it.

For genuine vertical maxillary excess, the correction is a Le Fort I impaction, which repositions the whole upper jaw. That is surgery, and it belongs to a maxillofacial team.

Aligners can run alongside any of the three. They cannot substitute for one.

What should you settle before signing a treatment plan?

1. Ask for your gingival display in millimetres, taken on a posed smile from gingival zenith to the lower border of the upper lip.
2. Ask for lip mobility: upper lip length at rest minus length at full smile, against the 8 mm threshold.
3. Ask which of the five causes is named in your record, and what share of the display each contributes.
4. Ask how many millimetres the appliance alone is expected to remove, and how many need an adjunct.
5. Ask for the planned months, the assumed refinement count, and what happens if intrusion under-expresses.
6. Ask what the plan is if you land in the 17.2% who finish in braces.

A clinician who answers all six in millimetres and months is diagnosing. One who answers with before-and-after photographs is selling; camera angle, head tilt and how hard someone smiles all change gingival display without changing anything about the patient.

Frequently asked questions

Can Invisalign fix a gummy smile?

Only when over-erupted upper front teeth are the cause. Invisalign and other aligner systems intrude incisors, achieving roughly 33% to 53% of planned intrusion in published reviews, around 0.9 mm in adults. Gum showing because of a short or hypermobile lip, an unfinished gum line, or a tall upper jaw needs a different treatment.

What disqualifies someone from clear aligners?

Skeletal causes are the main disqualifier for gummy smile cases: a tall maxilla needs surgery, not trays. Untreated gum disease must be resolved first. Reviews also flag severe rotations, large extraction-space closure and impacted teeth as movements aligners handle poorly. Poor wear time disqualifies anyone, since removable appliances only work while worn.

Can braces correct a gummy smile?

Braces correct the same single cause aligners do, over-erupted front teeth, and generally deliver vertical movement more reliably through a rigid archwire. Adding miniscrews produced 1.55 to 2.09 mm of incisor intrusion over three months in a 2024 randomized trial. Braces still cannot alter lip length, lip movement, gum position or jaw height.

How much gum showing is normal when I smile?

One to two millimetres is treated as normal in the StatPearls reference. Orthodontists start calling it unattractive at 2 mm, while general dentists and lay people in the 1999 Kokich study did not react until 4 mm. About 10.57% of young adults photographed in 1984 showed a continuous band of gum.

How do I fix a gummy smile after braces?

Have the cause re-measured rather than repeating orthodontics. If teeth are in position and gum still covers the crowns, that points to altered passive eruption, treated by gingivectomy or crown lengthening. If the lip lifts more than 8 mm, botulinum toxin or lip repositioning applies. Residual over-eruption may need anchored intrusion.

Will a gummy smile come back after Botox?

Yes. A 2023 meta-analysis measured 3.22 mm of reduction at two weeks and 2.70 mm at three months, then a drift back toward baseline by roughly eight to nine months in the studies that followed patients that long. Repeat injections maintain the effect; they do not change the underlying lip or jaw anatomy.