Comparison of Orthodontic Adhesives for Bonding to CAD/CAM Provisional Crowns

Purpose: This study was designed to compare the shear bond strength (SBS) of four commonly-used orthodontic adhesive systems used for bonding metallic brackets to Computer-Aided Design/Computer-Aided Milling (CAD/CAM) Poly Methyl Methacrylate (PMMA) provisional restorations. An Adhesive Remnant Index (ARI) survey was used to reveal patterns in the types and locations of bond failure between the experimental groups. Methods: A standardized process was used to prepare the surface of PMMA blocks (Ivoclar Vivadent Inc., Amherst, NY) prior to bonding 80 stainless steel orthodontic brackets (3M Unitek Victory Series MBT Versatile+ with 0.022-inch slot, Monrovia, CA). The samples were divided equally amongst four groups, each utilizing a different adhesive bonding system. The first group (Ivoclar) involved adapting a technique recommended by the manufacturer for repairing PMMA provisional restorations and applying it to the bonding process of orthodontic brackets. The remaining three groups utilized orthodontic-specific adhesive bonding systems that are commonly used in orthodontic practices (3M Unitek, Ormco, and Dentsply GAC) to bond brackets to the PMMA substrate. To measure SBS, a single-bladed Instron unit (Model #5943, Norwood, MA) was utilized. All debonded brackets were subsequently examined using a stereo microscope set to 20x magnification to classify the type of bond failure within the Adhesive Remnant Index.