When a tooth needs a crown instead of a filling

The argument is mechanical. A filling depends on the tooth around it to carry the load, and once the walls are thin, or a cusp has gone, chewing forces flex them instead. Repeated flexing is what splits teeth, often below the gum. A crown wraps the tooth so load is resisted rather than levered.

Where that line sits is a judgment, not a formula. What pushes a tooth over: the width of the existing filling against the distance between the cusps, cracks visible once it comes out, pain on releasing a bite, and whether the person grinds. A crown removes a great deal of tooth, so where a bonded composite filling still does the job, that is the better move.

The situations that usually call for a crown

  • A fractured cusp. Once a corner has broken, the remaining walls carry more than they were built for and the next fracture runs deeper.
  • A large old restoration that keeps failing. Each replacement leaves a bigger cavity and thinner walls, until there is more filling than tooth.
  • After root canal therapy on a back tooth. The tooth has lost the structure removed to reach the nerve on top of whatever decay took. Front teeth with small access cavities sometimes do not need it.
  • Cracked tooth syndrome. Sharp pain on biting, particularly on release. A crown holds the segments together. If the crack has run into the root it will not save the tooth, and that cannot always be known in advance.
  • Severe wear, or a front tooth that is dark, chipped and heavily filled at once. Where too little sound enamel remains for a veneer to bond to.

Crown materials, and where each one suits

The choice trades strength against appearance against how much tooth is removed.

Zirconia
A very strong ceramic for back teeth and heavy grinders. Full-contour zirconia is more opaque than enamel, and more translucent versions give up some strength. It needs less thickness, so less tooth is removed.
Lithium disilicate
A glass ceramic, often called by the brand name e.max. It balances strength and translucency and bonds strongly, a common choice for front teeth and premolars.
Layered porcelain
A ceramic core with porcelain built up by hand, giving a technician the most control over color, translucency and texture. The layered surface chips more readily, so it suits high appearance demands and moderate load.
Porcelain fused to metal
Porcelain baked over metal. Long track record and strong. The metal is opaque, so more tooth comes off to make room for porcelain, and if the gum recedes a dark line can show at the margin.

Two appointments, and the temporary in between

  1. Shade, then preparation

    Shade is recorded first, while the teeth are still hydrated, and photographs go to the laboratory with it. Then the old filling and any decay come out and the tooth is shaped for even material thickness all round.

  2. Impression or scan, and the temporary

    An accurate record of the prepared tooth, the margin at the gum, the bite and the opposing teeth. The temporary holds the gum in shape, so avoid sticky food and pull floss out sideways.

  3. Fitting the crown

    Fit at the margin checked, contact with the neighbors checked with floss, bite adjusted. Then you get a mirror and daylight before anything is cemented, so this is the appointment to speak up.

  4. Cementing and review

    Every trace of excess cement is removed, particularly below the gum where it causes inflammation months later. Tenderness for a few days is normal. A bite that feels high is not, and adjusting it takes two minutes.

Margins, gums and how the crown looks in five years

The margin is the joint where crown meets tooth, and it decides almost everything long term. A crown that fits precisely gives plaque nowhere to sit. One with a gap or a ledge collects plaque, inflames the gum, and lets decay start underneath where nobody can see it.

Gum health decides how a crown looks years later. Inflamed tissue bleeds, swells, then recedes, and recession exposes the margin and the darker root below. That is why gum treatment through periodontal care comes first, and why your part is cleaning that margin daily. The crown cannot decay. The tooth underneath can.

Porcelain crown questions we get asked

How long does a porcelain crown last?

Ten to fifteen years is a fair planning figure and a great many go longer, while some fail early. What separates them is gum health, daily cleaning at the margin, and how much sound tooth was left underneath. Night-time clenching breaks more crowns than chewing does, so if you grind, expect a night guard to be part of the plan.

How much does a crown cost?

It depends on the material, the laboratory work, and whether the tooth needs a build-up or root canal therapy first. A crown needed to hold a broken tooth together is generally assessed differently by a plan than the same crown done to change appearance. See insurance and financing.

Will the crown match my other teeth?

Matching one front tooth is the hardest thing in dentistry, because the tooth beside it is the reference. Careful shade mapping gets most cases very close. A very good match is realistic. An identical one is not always achievable.

Should I whiten before having a crown made?

If you are planning to whiten at all, do it first. Porcelain does not lighten, so a crown matched to your current shade will stand out if the teeth around it change later. See whitening.