Crowns are full coverage restorations of teeth. They are needed when a significant amount of tooth structure is lost due to caries, trauma or malformation and to give extra strength and support to the tooth that has undergone root canal treatment. They cover the top of the tooth and go down the side of the tooth, holding it together to prevent further damage to the tooth.
Crowns are fabricated from a variety of materials –
- Porcelain fused to metal (PFM), also called metal ceramic.
- Metal-free ceramic.
- Metal crowns: Because of its “metallic” appearance, this type of crown is now used almost exclusively on back teeth. They are stronger, cheaper and require less tooth reduction than porcelain crowns. Due to their non-natural appearance and extremely improved strength and esthetics of contemporary porcelain crown materials, metal crowns are becoming less preferred options in modern dental practice. However, they are excellent cost-effective options for patients for whom esthetics is not a major concern.
- Porcelain fused to metal crowns (PFM): Also called, metal-ceramic crowns, these consist of a tiny shell of metal overlaid by tooth-colored porcelain. The presence of metal adds strength while the covering porcelain provides satisfactory esthetics. These are extremely durable crowns which can be used for both front and back teeth. Due to the presence of metal, their esthetics is not as good as metal free ceramic crowns.
- Metal-free ceramic crowns: These are excellent options for front teeth because of their extremely natural or “lifelike” appearance. In the past, they were not considered strong enough for back teeth, but all ceramic crowns today are much stronger than they used to be and are being increasingly used for back teeth of patients with high esthetic requirements.
- Zirconia crowns: These are the newest type of crowns which consist of a shell made of zirconium oxide (zirconia) covered by porcelain. The zirconia ensures that excellent esthetics are maintained while providing strength close to that of metal crowns. Though slightly more expensive than other crown options, these crown give excellent service in almost all clinical situations
- Fixed Partial Dentures/ Bridges: When one or more teeth are missing, fixed dentures can be given by taking the support of natural teeth adjacent to the missing teeth. This involves slightly reducing or grinding the natural teeth. The various material options used for making fixed partial dentures are same as that used for making crowns. These are preferred to removable dentures by most patients as they generally feel more secure and natural, allow better chewing experience, and are generally more esthetic. However, the remaining natural teeth should be relatively healthy and strong to provide support for the artificial teeth. In the last decade, use of these teeth supported fixed partial dentures has declined as they involve grinding natural teeth and are hence less preferred to implants. However, they are generally more cost effective than implants and serve as excellent alternatives in patients in whom implants are not indicated.
- The fixed partial denture is placed when there are one or more teeth missing. The objective is to stabilize the bite, prevent the adjacent teeth from tilting and opposing teeth from dropping down into the space that has been lost. The choice of material is similar to the one used for crowns.