Quick answer
Crown lengthening is needed when a crown margin would sit too close to the bone, when a fracture or cavity extends below the gum, when a tooth is too short to retain a restoration, or when excess gum and bone make the teeth look short. It is not needed when the tooth is not restorable.
At a glance
- Restorative reasons
- Fracture, deep decay, short crown, failing margin
- Aesthetic reasons
- Short teeth, uneven gum line, gummy smile
- Space needed
- About 3 mm from bone to crown margin
- Not indicated
- Tooth not restorable or support too compromised
Crown lengthening is recommended in a narrow set of situations. The procedure is not a routine part of crown work, and it is not a cosmetic add-on to every smile makeover. When it is indicated, it is usually because the tooth cannot be restored well without it.
Here are the situations that justify it — and the ones that do not.
1. A fracture below the gum line
A tooth cracks, and the healthy tooth structure ends below the gum. If the fracture is shallow enough to expose, crown lengthening moves the gum and bone down so the crown margin can sit on sound tooth.
If the fracture extends below the bone, or into the root in a way that cannot be sealed, the tooth may not be restorable. The extraction comparison explains the line.
2. Decay that extends under the gum
Caries can spread below the gum line, especially under an old crown or filling. The dentist removes the decay and finds that the cavity margin is subgingival. Crown lengthening exposes the sound tooth so the restoration can seal.
The same logic applies to a tooth that needs a new crown but has an old margin that is already too deep.
3. A short clinical crown
Some teeth look short because the gum and bone cover more of the crown than they should. This can be developmental (altered passive eruption) or the result of wear, previous restorations or periodontal treatment. If the tooth needs a crown and there is not enough visible tooth to retain it, lengthening creates the space.
If the tooth is short only because of wear and the gum line is correct, the answer is usually a restoration, not surgery.
4. A crown margin that would violate the biologic width
This is the 3 mm rule in practice. The crown margin needs about 1 mm of sound tooth, 1 mm of attached gum and 1 mm of connective-tissue attachment above the bone. If the planned margin leaves less, the gum will stay inflamed and the crown is at risk.
The procedure moves the bone and gum away from the margin so the attachment can re-form at a healthy distance.
5. A gummy smile caused by excess gum and bone
Aesthetic crown lengthening is indicated when the teeth look short because the gum and bone cover the crown. It is not indicated when the smile is dominated by a hypermobile lip or a long upper jaw. The gummy smile guide explains the difference.
6. Uneven gum heights
A gum line that is higher on one tooth than its neighbour can be corrected with a gingivectomy or crown lengthening, depending on the bone level. The goal is a harmonious gum line, not a perfectly straight one.
7. Preparing a tooth for a restoration after periodontal surgery
Sometimes the tooth has been treated for periodontal disease and the gum has receded or the bone has been reshaped. A crown may need a more apical margin. Crown lengthening can establish the margin on sound tooth.
The “360 around the tooth” question
Patients often ask whether crown lengthening is done “360 around the tooth”. The phrase means the surgeon recontours the gum and bone around the full circumference, not only the side where the problem is visible.
Why full-circle treatment is common:
- The biologic width is a ring around the tooth, not a patch on one side. If the bone is reduced on one side only, the attachment on the other sides may still be too close to the margin.
- A one-sided reduction can leave the tooth looking tilted or the gum line uneven.
- The restoration margin usually runs around the tooth, so the space has to be available around the tooth.
- Healing is more predictable when the contour is smooth and continuous.
It is not universal. A localized defect on a molar may be treated with a localized flap, and some aesthetic cases treat only the teeth that show. The surgeon plans the whole tooth but may not cut the whole circumference. Ask which approach is planned for your tooth and why.
When crown lengthening is not indicated
It is not the right procedure when:
- The tooth is not restorable: the fracture is too deep, the root is too short, or the support is too compromised.
- The tooth is mobile from untreated periodontal disease. Treat the disease first.
- The problem is tooth wear, not the gum or bone level.
- The gummy smile is caused by the lip or jaw.
- The patient cannot tolerate surgery or the healing period and a simpler option exists.
- The only goal is to avoid a crown replacement that is needed anyway.
A periodontist should be willing to say “this is not the right procedure for you.” That is a diagnosis, not a sales failure.
What the consultation should measure
- The bone level around the tooth, by probing and radiograph.
- The width of attached gum.
- The tooth’s root length and crown-to-root ratio.
- The position of the planned margin.
- The neighbouring teeth and the gum line.
- The restorability of the tooth.
If those measurements are not taken, the recommendation is a guess.
The cost context
When the procedure is indicated, the 2026 planning range is $700 to $1,800 for one tooth with gum and bone recontouring, and $350 to $900 for a gum-only reshape. The final crown is separate. The cost hub explains what the fee includes, and the insurance guide explains how to find out whether a plan will pay.
Crown lengthening vs no treatment
| Aspect | Do the procedure | Skip it |
|---|---|---|
| Crown seal | Margin lands on sound tooth with room to clean | Margin sits in the attachment; chronic inflammation |
| Restoration life | Better chance of a stable long-term result | Higher risk of leak, decay and early failure |
| Gum health | Attachment can re-form at the new level | Persistent gingivitis around the margin |
| Cost | $700–$1,800 for one tooth, plus the crown | Lower now, higher if the crown fails |
Frequently asked questions
How do I know if I need crown lengthening?
You cannot tell from the outside. A dentist or periodontist measures the bone level, probes the gum and reviews radiographs. The procedure is indicated when the crown margin would sit within about 2 mm of the bone, or when a fracture or cavity extends below the gum.
What does '360 around the tooth' mean in crown lengthening?
It means the surgeon recontours the gum and bone around the full circumference of the tooth, not just the side with the defect. A full-circle approach is common because the biologic width has to be re-established all the way around, and because a one-sided result looks and heals unevenly.
Is crown lengthening always done around the whole tooth?
Not always. A localized defect may be treated with a localized flap, especially on a molar where preserving support matters. But the surgeon still plans the attachment around the whole tooth. The choice is based on the bone level, the defect and the restoration.
Can a tooth be too broken for crown lengthening?
Yes. If the fracture extends below the bone and cannot be exposed without removing too much support, or if the root is short or the tooth is mobile from periodontal disease, extraction may be the better option. The procedure cannot make an unrestorable tooth restorable.
Is crown lengthening needed before every crown?
No. Most crowns are placed without it. It is needed only when the available tooth is insufficient — a deep fracture, decay under the gum, a short clinical crown or an old margin that sits too close to the bone.
Can I wait and see?
Sometimes. A small defect with no symptoms may be monitored. But a crown margin placed in the attachment does not improve with time, and a fracture below the gum can progress. Ask what the risk of waiting is for your tooth specifically.