Gummy Smile? What Aesthetic Crown Lengthening Actually Involves

By Dr. Boris Zusin · Published August 26, 2026

Excessive gingival display — more commonly called a “gummy smile” — means an unusually large amount of gum tissue shows above the upper front teeth when you smile. It's a cosmetic concern, not a health problem on its own, and one of the most common underlying causes is altered passive eruption (APE): a developmental pattern where the gum tissue never fully migrated down to its expected adult position on the tooth, leaving teeth that look short and a smile that looks “gummy” even though the teeth themselves are a completely normal length underneath.

What Actually Causes a Gummy Smile?

A gummy smile can come from more than one source, and telling them apart matters because the right fix depends on the cause. Altered passive eruption is a purely dental/periodontal cause — excess gum tissue, sometimes with excess bone, covering more of the crown than it should. But a gummy smile can also come from a hypermobile upper lip that simply rises higher than average when you smile, from a vertically overgrown upper jaw (a skeletal issue), or from teeth that have naturally worn short over time. Because the treatment for each is different — periodontal surgery for APE, lip-repositioning surgery or Botox for lip hypermobility, orthognathic surgery for a skeletal cause — a careful exam to identify which factor (or combination of factors) is actually driving the appearance comes before any treatment is planned.

When the Cause Is a Hypermobile Lip: Botulinum Toxin (Botox)

When a hypermobile or overactive upper lip is the driver — the lip simply rises more than average during a smile, while the jaw and teeth are otherwise positioned normally — botulinum toxin type A (BoNT-A, commonly known by the brand name Botox) is the treatment of choice rather than surgery. The best candidates are patients whose lip moves more than about 8mm from rest to a full smile, with no significant altered passive eruption, gum overgrowth, or jaw-position component mixed in.

BoNT-A works by chemically weakening the small muscles that elevate the upper lip — primarily the levator labii superioris alaeque nasi, levator labii superioris, and zygomaticus minor — so the lip simply doesn't rise as far when you smile, showing less gum. A single injection site over where those three muscles converge (sometimes called the “Yonsei point”) has performed as well in trials as targeting the muscles individually, and dosing is tailored to how much gum shows, typically in the range of about 1.25–7.5 units per side. Head-to-head trials have found that an individualized, higher, multi-point dosing approach outperforms a simplified fixed low single-point dose, both in how much the gum show is reduced and in how long the result lasts.

Results show up within days and peak at 2 to 4 weeks — pooled data across trials shows gum display dropping by roughly 3.4mm on average at the 2-week mark, with most patients down to 3mm of visible gum or less, and the effect works best for gummy smiles of about 4mm or under to begin with. Because it's a muscle treatment rather than a structural one, it's temporary: the effect starts fading around 3 months and gum display is generally back close to where it started by about 6 months, so touch-up injections are needed to keep the result. That reversibility is also a genuine advantage — it lets a patient effectively preview what a more permanent option like lip-repositioning surgery would look like before committing to it, and it can be repeated indefinitely as a maintenance option on its own.

BoNT-A is safe with mostly minor, temporary side effects, but it's a technique-sensitive procedure — injecting in the wrong spot can create an asymmetric or unnatural-looking smile, and overtreatment can affect speech or make a smile look artificially stiff. It also only addresses a lip-driven gummy smile: if altered passive eruption, gum overgrowth, or a vertically overgrown jaw is contributing, Botox alone won't fully resolve those pieces — crown lengthening, orthodontics, or jaw surgery still need to address them, sometimes alongside Botox rather than instead of it. As with the surgical side of treating a gummy smile, we refer this out: Dr. Boris Zusin identifies whether a hypermobile lip is part of your picture during the exam, and coordinates the referral to a trusted oral surgeon who administers the injections, with Dr. Boris Zusin following up on the result as part of your overall smile plan.

The Two Types of Altered Passive Eruption

When APE is the cause, the surgical plan hinges on one key piece of information: where the bone crest sits relative to the cementoenamel junction (CEJ) — the natural boundary between the crown and the root. This is checked by gently probing down to bone under local anesthesia (bone sounding), sometimes alongside imaging.

Original illustrative diagram — not a substitute for an in-person periodontal exam.

In Type I APE, the bone crest sits at a normal distance below the CEJ, but the gum tissue itself sits too high on the crown. Because the underlying bone is already in the right place, removing the excess gum tissue alone — a gingivectomy, or an apically positioned flap without touching bone — is enough to reveal the normal-length crown underneath. In Type II APE, the bone crest is also elevated, sitting close to or at the CEJ. Removing gum tissue alone in this scenario doesn't hold: the gum simply relapses back toward its original position because there isn't enough distance between the bone and the new gum margin to support healthy biologic width (the natural buffer of attached tissue every tooth needs). Type II cases require a full-thickness flap and osseous recontouring (reshaping the bone) in addition to removing gum tissue, so the final gum position has room to stay where it's put.

Planning the New Gumline Digitally

Because the whole point of the surgery is a specific cosmetic outcome, the surgical outline is increasingly planned before ever picking up a scalpel. Digital smile design software lets the clinician map exactly how much tissue needs to come down on each tooth relative to facial and smile references, and guided surgical techniques — including 3D-printed surgical guides — translate that digital plan directly onto the tissue, improving the predictability and symmetry of the result and, in select cases, allowing the surgical and restorative steps to be completed closer together.

How the Procedure Is Coordinated

Aesthetic crown lengthening is periodontal surgery — it's performed by a periodontist, the same way we refer out other surgical procedures like implant placement and root canals. Dr. Boris Zusin handles the exam, the diagnosis of which type of APE (or other cause) is involved, and the overall cosmetic treatment plan, coordinates the referral to a trusted periodontist for the surgical flap and any bone recontouring, and then completes any restorative work — whitening, bonding, or veneers on the newly proportioned teeth — once the tissue has healed and stabilized.

Recovery and When You'll See the Final Result

Soft tissue heals visibly within a few weeks, but the gum position isn't considered stable enough for permanent restorative work until longer than that — particularly in Type II cases involving bone recontouring, where the tissue needs time to remodel and mature before a crown or veneer margin is placed against it. Placing a restoration too early, before the gum has fully settled, risks a mismatch between the final gum line and the restoration margin. Mild swelling, tenderness, and temporary sensitivity are normal in the first week or two, similar to other periodontal surgical procedures.

Risks and Limitations

The main technical risk is relapse: if a Type II case is treated as though it were Type I (gum removal without addressing the bone), the tissue tends to grow back toward its original position because biologic width wasn't respected. There's also a limit to what crown lengthening alone can fix — it addresses gum and bone position, not a lip that rises too high or a jaw that's vertically overgrown, which is why an accurate diagnosis up front matters more than the surgery technique itself.

Getting This Done on the Upper West Side

Patients from Lincoln Square, Lincoln Center, and along West End Avenue and Riverside Drive typically start this process the same way: an exam and photos at our West End Avenue office to confirm whether a gummy smile is coming from altered passive eruption, a lip that moves more than average, or something else entirely. If periodontal surgery is the right fit, Dr. Boris Zusin coordinates the referral to a periodontist locally, so the surgical visit doesn't mean crosstown travel, and handles the follow-up restorative work — matching whitening, bonding, or veneers to your newly proportioned smile — back at our Upper West Side office once healing is complete.

Is Crown Lengthening Right for You?

If you feel your teeth look short, or you're self-conscious about how much gum shows when you smile, the only way to know which of these causes applies to you — and whether gum tissue alone or gum plus bone is involved — is an in-person exam. That's also the point where we can tell you honestly whether crown lengthening alone will get you the result you're picturing, or whether it needs to be paired with something else.