These are all ways to fix tooth that has been damaged by fracture or decay. Caps and crowns are the same thing. The correct term is crown, but many people refer to them as caps because they sit on a tooth like a cap sits on your head. Crowns, inlays, and onlays are all made in a laboratory. This means that they are made from impressions taken of the tooth. To place these restorations, two visits are needed. At the first visit, the tooth is prepared, the impression is taken, and a temporary restoration is made and placed. At the second visit, the temporary is removed and the permanent restoration is placed.
Which one of these restorations is used depends on how much of the tooth has been damaged and needs to be replaced. If the cavity is small, a filling works fine. For cavities that are a little larger, fillings are harder to place well and don’t hold up as well. For that reason, an inlay, this is made outside the mouth and cemented in place, will work better and last longer.
If part of the remaining tooth structure is weak, then the restoration can be made to wrap around that part. This supports the weak section and prevents it from breaking. If only part of the tooth needs to be protected, then it is called an onlay. If the entire tooth needs to be covered, it is a crown.
Crowns, inlays and onlays can be made from white material or gold. The white materials look beautiful. In fact, they are often invisible in the mouth; they look just like natural teeth. Gold does have one advantage: longevity.
In some cases, the choice is obvious. Sometimes, there are reasonable options depending on your priorities (cost, longevity, appearance). In every case, the situation will be discussed with you in advance so you can participate in the decision making process.
