Cracked teeth have been traditionally treated by a process we call “containment”. The tooth is prepared so that restorative material will be around the tooth circumferentially and contain the cracked pieces, holding them together and preventing progression of the crack. The placement of a crown or onlay removes a significant amount of tooth structure and increases the risk of post operative pulpal death. Adhesive dentistry and composite materials can be used as an alternative because of their ability to reinforce the remaining tooth structure. Studies show that teeth with MOD preparations and restorations exhibit much lower cuspal flexure when the restoration was bonded into place using an acid-etch adhesive technique. This ability to hold the remaining cusps together and limit flexure can prevent the progression of a crack while still preserving tooth structure.
One of the concerns with using composite and adhesive techniques to reinforce cusps is of course Bond Degradation and the ability of the tooth to continue fracturing over time as the bond strength drops. Unfortunately we do not have good research or information about how long the bond is strong enough to reduce cuspal flexure. In clinical practice the decision between “containment” placing an onlay or crown and the use of “cusp reinforcement” with a bonded composite will depend on your professional preferences and the condition of the tooth. For teeth that have been endodontically treated, the recommendation is still containment with an indirect restoration.