When a tooth needs a crown instead of a filling
A crown is right when what remains cannot hold a filling, or when the tooth needs protection from splitting.
- After root canal therapy on a back tooth. The tooth has lost structure to decay and to the access opening, and covering the cusps stops it fracturing.
- A cracked tooth. Sharp pain as you release a bite, rather than as you press, is the sign of a crack flexing. A crown holds the segments together like a band around a barrel. A crack running below the bone ends the tooth.
- A broken cusp or a failed large filling. Once a filling is wider than half the biting surface the walls are thin, and a larger filling buys a year or two before one breaks.
- Heavy wear, or a tooth rebuilt with a post and core, where little tooth is left above the gum.
Not everything needs a crown. Where only part of the biting surface is damaged, an onlay covers the weak cusps and leaves the rest alone. For a tooth that shows, see porcelain crowns.
Crown materials and where each one fits
The choice depends on how much space there is, how hard you bite, and whether the tooth shows.
- Zirconia
- A very strong ceramic that takes heavy chewing and needs less thickness than layered porcelain, so less tooth is removed. The usual choice for molars and for grinders. Older zirconia looked flat at the front; newer translucent versions are better.
- Lithium disilicate, often sold as e.max
- A glass ceramic that handles light as enamel does and can be bonded rather than cemented. A strong choice for front teeth and premolars, avoided where forces are extreme.
- Porcelain fused to metal, gold and cast alloys
- Porcelain fused to metal has decades of track record and is still sensible on bridges, though it can chip and a dark line can show if the gum recedes. Gold does not chip and seals well at thin margins, but it is not tooth colored, so it is kept for back molars.
The two appointments
Two visits, two to three weeks apart, with a temporary crown in between.
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Numbing and preparing the tooth
Decay and any failing filling are removed, and a build-up placed if there is not enough tooth to hold a crown. The tooth is then shaped, usually removing one to two millimeters, with the margin where it can still be cleaned.
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Records, shade and a temporary crown
An impression or scan captures the preparation, the neighbors and your bite, with the gum retracted so the margin is accurate. Shade is matched before the tooth dries out and looks lighter than it is. A temporary goes on with a soft cement designed to release cleanly.
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The fitting visit
The crown is checked for seating, contacts that hold floss, a smooth margin and shade. The bite is adjusted with articulating paper until it is even, then it is cemented and excess cement cleared from under the gum.
What decides how long a crown lasts
The crown itself rarely fails. What fails is the tooth underneath, at the margin where the two meet. A margin that is smooth, finishes on sound tooth and sits where a brush and floss can reach it stays clean. Plaque left at that edge causes decay under the crown, and that decay often gives no warning, particularly on a tooth that has had root canal treatment and cannot signal pain. Gum inflammation makes it worse, which is why periodontal care protects the crowns you have.
Grinding is the other major factor, because a crown hammered every night carries loads it was not designed for. A night guard protects the investment, and jaw pain is worth assessing under TMJ and jaw pain. Crowns commonly last many years and plenty serve for decades. Nobody can give you a number for your tooth, but the cleaning and the recall visits are within your control.
Crown questions
Does getting a crown hurt, and why is the tooth sensitive afterwards?
The tooth is numbed for the preparation and most people compare it to a large filling. The gum can be tender for a day or two, and mild sensitivity to cold and pressure is common and settles. Sensitivity that worsens, pain on biting past a week, or throbbing means something needs adjusting.
How long does a crown take, and can it be done in one visit?
The preparation appointment runs an hour to ninety minutes and the fitting is shorter, two or three weeks later. Some offices mill crowns chairside in one visit; we work with a dental laboratory, so a technician builds and characterizes it.
My crown came off. What should I do?
Keep it, and do not use a household adhesive, which contaminates the fitting surface and can make a reusable crown impossible to recement. Temporary dental cement from a pharmacy holds it for a day or two. Call us, because the stub is sensitive and the neighboring teeth move within days. See dental emergencies.