An inlay is done when there is no damage to the cusps of the tooth and the inlay can be placed right on the tooth. An onlay is used when the damage is a little more extensive.
The laboratory creates a restoration made from porcelain, gold, or a composite resin.
The restoration takes about 2-3 weeks to make, so a temporary inlay or onlay will be placed on the tooth for that time. During your next visit the inlay or onlay will be placed into your mouth and fixed to your tooth.
Your tooth will look natural and, you (or anyone else) won’t be able to tell the difference.