Key points
- A crown is a cap that covers a damaged tooth or sits on an implant.
- Metal-ceramic crowns have a metal core under porcelain and the longest track record. All-ceramic crowns, including zirconia, have no metal.
- A review of 67 studies covering over 14,000 crowns found 94.7% of metal-ceramic crowns surviving five years. Most all-ceramic types were similar.
- Zirconia-based crowns in that review survived 92.1% at five years, with a wide margin of uncertainty, and lost more crowns to chipping of the porcelain layer.
What a crown is
A crown covers a tooth that is badly damaged, heavily filled or root-treated, or sits on top of an implant. It restores the tooth's shape and lets it chew again. Crowns are made in a dental laboratory to fit the individual tooth.
The main materials
Metal-ceramic crowns have a metal framework covered with porcelain. They have been used for decades and are the reference against which others are measured. All-ceramic crowns have no metal at all. They include glass-based ceramics such as lithium disilicate, and high-strength ceramics such as zirconia. Without metal there is no dark line at the gum and the colour can be closer to a natural tooth.
What the research shows
Sailer and colleagues (2015) reviewed 67 studies covering 4,663 metal-ceramic and 9,434 all-ceramic single crowns. After five years, 94.7% of metal-ceramic crowns were still in use. Lithium disilicate and similar glass-ceramics reached 96.6%, densely sintered alumina 96%, and zirconia-based crowns 92.1% — the last with a wide confidence interval (82.8–95.6%), meaning the estimate is less certain.
The reviewers found that zirconia-based crowns were lost more often than metal-ceramic ones because the porcelain layered on top fractured. They concluded that most all-ceramic crowns perform similarly to metal-ceramic crowns, front and back, and that the weaker feldspathic (silica-based) ceramics should be kept to front teeth.
How the choice is made
The dentist weighs the position of the tooth, the forces it carries, grinding habits, appearance and the condition of the tooth itself. There is no single best material for every tooth.
Worth knowing
- The studies in that review date from before 2014, when most zirconia crowns were a zirconia core covered with porcelain. The chipping problem came from that porcelain layer.
- Weaker feldspathic (silica-based) ceramics did less well and were advised only for front teeth.
- Which material suits you depends on where the tooth is, how strong your bite is, and how it should look — and is decided with the dentist.
Sources
This summary is general information and no substitute for an examination and personal medical advice. The figures are averages from studies, not a promise of a result.