What is an Onlay and how is it different from Inlay?

When the natural tooth has been significantly compromised by caries or fracture it is necessary to reinforce the tooth to prevent further deterioration. However, if the damaged area is over one third of the total tooth surface but less than one half we are faced with a following restorative dilemma: A dental filling, while covering the missing parts, will not add strength to the tooth. On the other hand a crown will be strong enough to strengthen the tooth, but will require removal of the healthy tooth structure that is still intact.

The answer is an onlay. Basically it is a cross between a filling and a crown and has best characteristics from both of these procedures. They are conservative like filling so that you save as much of your valuable tooth structure as possible, and at the same time they are fabricated outside your mouth which allows us to make them strong so they will support the rest of the tooth when they are bonded onto the tooth.

An ON-lay is a restoration that covers one or more cusps of the tooth. In comparison, an IN-lay sits completely between cusps. In this regard a crown is essentially an onlay that covers all 4 cusps.

Advantages of a porcelain onlay

One advantage of a porcelain onlay is that it preserves more of the natural tooth structure. The more of your natural tooth remains, the more restorative options are available in the future.

Also, since it rarely goes down to the gumline, it is easier to keep the margin of the restoration clean when you brush your teeth. Thus the porcelain onlay is less likely to get new decay.

Third, porcelain onlays, being made entirely of porcelain, are very esthetic. They look extremely natural.