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Dr. Khalid AletaibiConservative Dentistry · Dubai

Making a broken tooth restorable

Crown lengthening: when there is not enough tooth to hold onto

A tooth that has broken level with the gum presents a specific problem, and it is not the missing piece. It is that a crown needs to grip a collar of solid tooth below its own margin in order to survive being chewed on, and when the fracture is at or below the gum line, that collar does not exist. Crown lengthening moves the gum and, usually, a small amount of bone, so that it does.

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Quick answer

Crown lengthening is a periodontal procedure that repositions the gum, and usually a small amount of the bone beneath it, to expose more of the tooth above the tissue. Done for restorative reasons, its purpose is to create a ferrule: a continuous collar of sound dentine that the crown can encircle. A 2026 systematic review and meta-analysis of 33 studies found that a ferrule height of at least 2 mm significantly improved fracture resistance, with a mean difference of 165 N, and that the presence of a ferrule increased clinical survival with a risk ratio of 1.34. It concluded that no restorative strategy matched the reinforcement a natural dentine ferrule provides.[^1] Dr. Khalid Aletaibi plans the case with the periodontist to the finished tooth proportions and does the restoration.

What it creates

A ferrule, a collar of sound dentine

Target height

1.5 to 2.0 mm, dentine at least 1 mm thick

Effect on survival

Risk ratio 1.34 with a ferrule present

Not the same as

Aesthetic lengthening for a gummy smile

How Dr. Khalid helps

The measurement comes before the surgery, and it is a restorative measurement. How much sound tooth remains above the bone, how much has to be exposed for a ferrule of adequate height and thickness, and what the finished tooth will look like once it is that long. Dr. Khalid Aletaibi works that out and plans it with the periodontist from the same records, so the surgery is cut to the restoration. The periodontist carries out the procedure. He waits for the tissue to settle before starting the definitive work, and does that work himself.

The collar is doing the work

When a crown is loaded, the force does not stay where it lands. It travels down and outwards, and what resists it splitting the tooth is a band of intact dentine that the crown wraps around below its margin. That band is the ferrule. Without it, the crown is essentially a cap sitting on a core, and the core has nothing to brace against.

A 2026 systematic review and meta-analysis brought together 33 studies, six of them clinical, to quantify this. A ferrule at least 2 mm high improved fracture resistance by a mean difference of 165 N, with a confidence interval of 110 to 215. The presence of a ferrule raised clinical survival with a risk ratio of 1.34, interval 1.12 to 1.59. A complete circumferential ferrule with dentine at least 1 mm thick gave the most favourable reinforcement, and partial ferrules with two or more opposing walls still helped.[1]

Why the gum has to move for the tooth to be exposed

There is a band of attachment between the top of the bone and the base of the gum crevice, and a restoration margin placed inside it does not heal quietly. It produces persistent inflammation, bleeding and eventually bone loss at that site. So exposing more tooth is not simply a matter of trimming gum: the bone underneath usually has to be repositioned as well, so that the attachment can re-form below the new margin rather than around it.

That is the reason crown lengthening is a surgical procedure rather than a trim, and it is also why the tissue is given time to settle before the definitive restoration is made. A margin fitted to tissue that is still rebounding is a margin in the wrong place a few months later.

When lengthening is not the answer

There are limits, and naming them is more useful than operating. If reaching a ferrule would take the bone level past the point where the neighbouring teeth can carry their own tissue, the aesthetic and periodontal consequence falls on teeth that were healthy. If the fracture runs vertically down the root, no amount of exposure creates a restorable tooth. And if lengthening would leave a root too slender to bear load, the tooth has been made restorable on paper and weaker in fact.

What to expect

In practice

  • The ferrule measured before surgery is discussed, because that is what decides the height needed
  • The finished tooth proportion agreed in advance, so it is not longer than its neighbours by accident
  • The neighbouring teeth considered, since bone removed on one tooth affects the tissue on the next
  • A settling period before the definitive restoration, not a crown fitted onto moving tissue
  • An honest answer where the tooth cannot be saved even with lengthening

You always get an honest opinion and a written plan before any treatment begins, with no pressure.

Common questions

Frequently asked questions

Why can't a crown just be made longer instead?
Because the problem is not the length of the crown, it is what the crown has to hold. A ferrule works by encircling solid tooth below the restoration and resisting the forces that would otherwise split it. Extending the crown downwards over gum rather than tooth adds material without adding grip. The meta-analysis is blunt about this: no restorative strategy matched the biomechanical reinforcement provided by a natural dentine ferrule.[^1] The tooth has to be exposed, not the crown extended.
How much tooth needs to be exposed?
The review found a ferrule height of 1.5 to 2.0 mm and a dentine thickness of at least 1 mm associated with better biomechanical and clinical outcomes, with a complete 360 degree ferrule providing the most favourable reinforcement, though partial ferrules with at least two opposing walls remained beneficial.[^1] Those are the targets. The surgery has to expose enough to reach them while leaving the tissue attachment intact, which is why the number is worked out before rather than judged during.
Will the tooth end up looking longer than the others?
It can, and that is precisely why the finished proportion is agreed before the surgery rather than discovered after it. On a back tooth a small difference in gum height is invisible. On a front tooth it is the first thing anyone sees, and the calculation has to include the teeth either side, because the tissue between them responds to the bone level under all three. Where the aesthetic result would suffer too much, that is said, and other options are set out.
Is this the same as the surgery for a gummy smile?
The technique overlaps, the reason does not, and mixing them up is how the wrong operation gets done. Aesthetic crown lengthening treats a gum margin sitting too low on teeth that are already full length, which is a proportions problem. Functional crown lengthening exposes tooth so a restoration has something to grip, which is a structural problem. The measurements taken and the amount removed differ. If your concern is how much gum shows rather than a broken tooth, the gummy smile page is the one that answers it.

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