Crowns are full coverage reinforcement restorations that bring teeth back to their proper look and function. They're longer lasting, but require more aggressive prep work than a veneer (teeth must be reduced by 1.5 mm reduction as opposed to the .5 reduction required for veneers). Although it's always preferable to preserve the structure of a natural tooth, it isn't always feasible. For example, if an old filling has broken down, once the decay is removed, the tooth's biting surface is undermined, so it needs to be supported by either an onlay, which goes over just the tooth's cusps, or a full-coverage crown.
Crowns can be made up of different materials - porcelain or a combination of porcelain with metal. The type that's chosen not only depends on where the tooth is situated, but what the condition of the tooth is (how discolored it is and how decayed it is), as well as the condition of the gums. There are three types to choose from:
Ceramo-metal: This is the strongest type of crown. It's usually the most economical, but its disadvantage is that the metal part of it may cast a dark shadow if your gum line recedes. The metal may also affect the color of the porcelain part of the crown.
Ceramo-metal crown with porcelain butt joint: This one can be more costly, but its design better hides the metal, so there's less chance of the metal peeking out eventually.
All-porcelain: An all-porcelain crown looks most like a natural tooth, and there's no metal to be concerned about. That said, it's not as strong as the other two types, so it's slightly more susceptible to chipping. It also costs the most. But, really, at the end of the day, who wants to risk that metal appearing if they don't have to?
First, your tooth or teeth are reduced 1.5 millimeters. An impression is then made of the tooth, from which a life-size model is built from hard stone. A technician then constructs the real crown from the stone model. As with veneers, you're sent home with your provisional set to test. Once the provisional is accepted by both patient and dentist, its important elements are copied into the final crowns.
Each side of the remaining tooth is tapered slightly to hold the crown in place. Next, the crown is tried on to fit comfortably under your gum tissue so any margin between the tooth and crown is hidden. The dentist spends time checking this fit, x-raying to verify it, and adjusting the bite very carefully. It's then finally attached with dental cement or a resin bonding cement.
Crowns are right for you if:
Your tooth (or teeth) needs more of a 360-degree type of replacement than one just on its face.
Advantages of crowns:
Teeth can be whitened or lightened to any desired shade. Very difficult stains can be covered.
Tooth size or tooth position can be transformed for a better look.
Disadvantages of crowns:
Any time a tooth gets prepared for a crown, there is always the possibility of unnerving it, which means causing severe damage to its nerve, which usually requires a root canal.
- Crowns have the longest lifespan of all restorations. They can last up to 15 years or more.