Crowns and onlay restorations both cover the biting surface of the tooth, and reduce the likelihood of the remaining tooth structure from fracturing.
A crown encompasses the entire tooth with the margins of restoration being placed at or just beneath the gum. An onlay restoration may requires a more superficial preparation as the margins of this type of restoration extend only half way down the tooth. The onlay preparation therefore conserves more tooth tissue and is more ‘tooth friendly’ compared to a crown preparation, although this may result in a more noticeable junction between the onlay margin and the adjacent tooth structure.
We recommend onlay restorations for molar teeth where aesthetics are not of prime concern to the patient