Evidence Based Bonding in Clinical Orthodontics Dr. Emile Rossouw Summary by: Dr. Bob Staley Dr. Rossouw presented an excellent historical review of enamel bonding in dentistry and orthodontics. It all began in the 1950s when Bowen invented an epoxy resin-methacrylate resin hybrid molecule known at BIS-GMA and Buonocore introduced acid etching of enamel to increase the adhesion of resins to the enamel surface. Newman was an early advocate for the bonding of orthodontic brackets to the teeth. Retief and others investigated the basic concepts of bonding. Adhesion is best when the distance between the bracket base and enamel is short and the contact angle between the bonded surfaces is small. Wetting of the bracket base and enamel surface by the resin increases adherence. The mesh pad was developed. Current techniques use 37% phosphoric acid gel for 15 seconds to etch the enamel surface, followed by a water rinse. The etched surface is saturated with a resin sealant or primer. The bracket with composite resin on its pad is placed lightly on the enamel. The height of the bracket is adjusted, the fit observed, and the mesial-distal position is checked before the bracket is pushed firmly on the tooth. Excess adhesive is removed and final adjustments are made. The resin is usually polymerized with a light source. Dr. Rossouw discussed the issues and challenges concerning white spot formation and the use of fluoride containing products to prevent and control this undesirable outcome in orthodontic patients. Dr. Rossouw reviewed the in vitro methods used to study bond strengths. Two basic de-bonding techniques have been used: tensile and shear-peel. Testing has shown that tensile de-bonding is more likely to result in fracture of the enamel than shear-peel. The in vitro testing of bond strengths has answered many questions asked by clinicians. A few of the test results mentioned by Dr. Rossouw follow. These studies have determined optimal durations for acid etching and the best combinations of adhesive materials for optimal bond strengths. Topical fluoride applications to teeth have no effect on bond strengths if done 7 days before bonding. Air abrasion of enamel resulted in significantly lower bond strengths compared to acid etching. Self-etching sealants and standard sealants are associated with similar bond strengths. Sand blasting of de-bonded bracket pads results in effective bond strengths. When recently bleached teeth are bonded, bond strengths are significantly lower. These and numerous other studies of bonding materials have given orthodontists practical information based on scientific method that raised the standard of patient care.