A Porcelain Onlay is similar to a dental crown – but much more conservative - in that it is designed to
restore a tooth that is broken down so much that it is beyond what a filling can do to fix it with
predictably and longevity. If too much of the tooth is missing, the tooth could fracture. A porcelain onlay covers most or all of the chewing surface of the tooth and strengthens it so that it won't fracture.
How Porcelain Onlays Differ From Crowns
A crown covers the entire chewing surface of the tooth and wraps around the entire tooth, all the way to the gum line. The porcelain onlay is more conservative. It covers only those parts of the tooth that are weak and it will not go down to the gumline. The healthy parts of the tooth are preserved and protected.
Advantages Of Porcelain Onlays
One advantage of porcelain onlays are that they preserve more of the natural tooth
structure. We believe if tooth structure is healthy, it is best to leave it alone if possible.
A second advantage is that, since they don't go down to the gumline, there is no chance
of them irritating the gum. Crowns can cause gum irritation and in some cases can even
contribute to gum disease. Also, since they don't go down to the gumline, it is easier to
keep the margin (that line where the porcelain onlay or crown ends and the tooth
begins) clean. The margin is out in the open where you can easily brush it. Thus,
porcelain onlays are less likely to get new tooth decay.
Third, porcelain onlays, being made entirely of porcelain, are very esthetic. They look
extremely natural.
Other Considerations
Porcelain onlays require a great deal of time and expertise to place correctly. They
require extensive training in cosmetic dentistry and in occlusion. Many dentists like to do
crowns because it is easier and faster. But easier and faster is not always better.
Second, porcelain onlays made entirely of newer, extremely strong and durable dental
porcelain and are nearly as strong as gold crowns or older style porcelain-fused-tometal
crowns.