Subjects in the Repair group will be given a local anesthetic only if required (i.e. for restorations extending gingivally or on exposed dentin surface) as per usual clinical protocol. The existing restoration will not be removed. The surface of the existing restoration will be roughened with a Brasseler 8856 bur without extending to the surrounding enamel (except is the defect being repaired is adjacent to enamel). No accessory groves/pits for retention will be prepared. To repair the restoration, the surface will be etched using 35% phosphoric acid, and then 3M ESPE Scotchbond Universal Adhesive System followed by 3M ESPE Filtek Supreme Ultra Universal Restorative composite will be used as per the manufacturer's instructions.

Subjects in the Replace group will be given local anesthetic (an injection of 2% lidocaine with 1:100 000 epinephrine). The type of injection and dosage of anesthetics will be dependent on the tooth being treated, and will follow the usual protocol used in the Dalhousie Dentistry undergraduate clinics. The existing composite restoration will then be removed and the peripheral enamel beveled if not already beveled. To restore the tooth, the surface will be etched using 35% phosphoric acid, and then 3M ESPE Scotchbond Universal Adhesive System followed by 3M ESPE Filtek Supreme Ultra Universal Restorative composite will be used as per the manufacturer's instructions.

The primary outcome will be the success of the restoration. This will be assessed using the modified U.S. Public Health Service (USPHS) criteria as first described by Cvar and Ryge (1971) and adapted by Wilson et al (2002).