Dentistry can be a tricky subject for the layman to properly wrap their head around. There are many tools and techniques involved, and all of them seem to be complicated. For example, many people have never heard of an onlay. However, onlays are a very important tool in the modern dentist's arsenal, with a wide range of applications.
What are porcelain onlays?
Like with crowns and fillings, porcelain onlays are used to restore damaged teeth. Porcelain onlays are the middle ground between a filling and a crown. A crown wraps around the entire visible surface of a tooth, terminating at the gumline. Whereas an onlay is a replacement for a partially destroyed tooth that needs at least one or two cusps replaced. They only see use when a tooth is too damaged for a filling, but a crown would be excessive.
Crowns and onlays are similar enough that they're made from the same range of materials.
What are the benefits of porcelain onlays?
There are a couple of good reasons that your dentist may decide to use a porcelain overlay. One such reason is that it preserves as much of the original tooth as possible. Most dentists feel that it is best to preserve healthy tissues and leave them alone whenever possible. In most cases, an onlay will restore one or a couple of cusps and never goes down to the gumline. Since an onlay never reaches the gum line, there's no need to worry about complications in that area, such as hotspots for tooth decay.
Are there any drawbacks to onlays?
The biggest drawback of onlays is the complicated nature of the process. They require a high degree of skill to make and install them. If done improperly, the onlay could suffer other durability issues in the long term. That said, a properly-executed onlay will have a long life indeed.
If you choose to go with a metallic onlay in a high-visibility area, there may be aesthetic concerns due to their artificial appearance. However these are the strongest possible material when it comes to onlays and crowns.
If you choose to go with a porcelain onlay instead, you will be able to enjoy a seamless, natural look. These are highly desirable for higher visibility areas and are an excellent choice all-around. Older porcelains and ceramics used to be weaker than all-metal or hybrid varieties. However those days are long gone. Nowadays, you will enjoy much of the same strengths of a metal onlay, but with a far more natural appearance. The same is true for crowns and porcelain inlays as well.