When a tooth needs a crown instead of a filling
A crown is the appropriate treatment when the remaining tooth 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 opening made for treatment, so less remains to resist chewing forces, and covering the cusps helps prevent fracture.
- A cracked tooth. Sharp pain on releasing a bite, rather than on pressing down, can be a sign of a crack flexing. A crown covers the tooth and holds the parts together so that the crack cannot open under load. A crack that extends well below the bone usually means the tooth cannot be kept.
- A broken cusp, or a large filling that has failed. Once a filling covers much of the biting surface, the walls around it are thin, and replacing it with a still larger filling often does not protect them.
- Heavy wear, or a tooth rebuilt with a post and core, where little natural tooth remains above the gum.
Not every damaged tooth needs a crown. Where only part of the biting surface is affected, an onlay can cover the weakened cusps and leave the rest of the tooth untouched. For a tooth that shows when you smile, see porcelain crowns.
Crown materials and where each one fits
The choice depends on the space available, on the force of your bite, and on whether the tooth shows.
- Zirconia
- A very strong ceramic that withstands heavy chewing and needs less thickness than layered porcelain, so less tooth structure has to be removed. It is a common choice for molars and for people who grind. Older zirconia could look flat on front teeth, and newer translucent versions handle light better.
- Lithium disilicate, often sold as e.max
- A glass ceramic that handles light much as enamel does and can be bonded rather than cemented. It is a strong choice for front teeth and premolars, and it is usually avoided where the biting forces are extreme.
- Porcelain fused to metal, gold and cast alloys
- Porcelain fused to metal has decades of documented use and still makes sense on bridges, though the porcelain can chip and a dark line can show if the gum recedes. Gold does not chip and seals well at thin margins, and because it is not tooth colored it is usually reserved for back molars.
What the appointments involve
Crowns are usually made over two visits, with a temporary crown in place while the final one is made.
-
Numbing and preparing the tooth
Decay and any failing filling are removed, and a build-up is placed if not enough tooth remains to hold a crown. The tooth is then shaped to make room for the crown, with the margin placed where you can still clean it.
-
Records, shade and a temporary crown
An impression or a scan records the prepared tooth, the neighboring teeth and your bite. The shade is matched before the tooth dries out, because a tooth that has dried during the appointment appears lighter than it is. A temporary crown is placed with a cement chosen to release cleanly later.
-
The fitting visit
The crown is checked for how it seats, for contacts that hold floss, for a smooth margin and for shade. The bite is adjusted with articulating paper until it is even, then the crown is cemented and any excess cement is removed from around the gum.
What decides how long a crown lasts
Problems usually begin at the margin, the line where the crown meets the tooth. A margin that is smooth, that finishes on sound tooth, and that sits where a brush and floss can reach it stays clean. Plaque left at that edge can cause decay under the crown, and that decay often gives no warning, particularly on a tooth that has had root canal treatment and can no longer signal pain. Gum inflammation makes it worse, which is one reason periodontal care protects the crowns you already have.
Grinding is the other major factor, since a crown that takes heavy loads every night is carrying more than it was designed for. A night guard helps protect the work, and persistent jaw pain can be assessed under TMJ and jaw pain. Crowns commonly last many years and many serve for decades. How long any one crown lasts varies, and the daily cleaning and the regular checkups are the parts 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 people often compare the experience to having a large filling placed. The gum can be tender for a day or two, and mild sensitivity to cold and pressure is common and usually settles. Sensitivity that worsens, pain on biting that lasts beyond a week, or throbbing needs attention, so call the office.
How long does a crown take, and can it be done in one visit?
Some crowns are made in a single visit with in-office milling, and others are made at a dental laboratory, which means two appointments with a temporary crown in between. Ask when you call which applies to the crown you need and how long the laboratory stage usually takes.
My crown came off. What should I do?
Keep it in a safe place and call the office. Do not glue it back on yourself, because household adhesives contaminate the fitting surface and can make an otherwise reusable crown impossible to recement. The exposed tooth can be sensitive and the neighboring teeth begin to move within days, so arrange to be seen soon. See dental emergencies.