Dentists hate to disturb a healthy tooth—even a damaged tooth that still has plenty of life left in it. Preserving as much of an existing tooth as possible is always the goal. In order to do that, dentistry has come up with a number of ways to make up for the loss of tooth structure; the method used depends on the extent of a given problem.
For instance, there are times when a tooth can be damaged beyond the ability of a traditional filling to repair it, but not damaged to the point where the expense and effort of a crown or an extraction/implant procedure is called for. In cases like those, you may be advised to go with an inlay or an onlay.
Sometimes, inlays or onlays are requested by patients for cosmetic reasons. Unlike the material used in a standard filling, the material used to make inlays and onlays can be colored (like crowns, veneers, and dentures) for an amazing color-match that makes the repair very difficult to notice.
Made of either a dental grade porcelain/ceramic or composite resin both inlays and onlays are performed on the rear teeth (premolars/molars); while they do essentially the same thing, they have different names due to the way they are placed:
Inlay:When the damage to a tooth is all within the “cusp” of the tooth (the cusp being the portion of a tooth that juts upward like the points of a crown), an inlay made to the specifications of the damaged area is fitted into the space and bonded with dental adhesive.
Onlay: When the damage is such that it reaches up and onto the cusp of the tooth, an inlay that matches the contours of the lower damaged is made, but with an overlapping portion that sits on the cusp, to cover the extended damage. The same type of dental adhesive is used to secure an onlay.
