Quality Resource Guide l Dental Adhesives 6th Edition 2 www.metdental.com Advantages of Dental Adhesion • Wide range of clinical applications • Reliable micromechanical retention to etched enamel without macro-retention features • Increased resistance to recurrent caries lesions when dental tissues are fully infiltrated with the adhesive • Recent adhesives used in self-etch mode are very reliable for treating root sensitivity • More conservative procedures (lesion-specific preparations) • Reinforcement of residual tooth structure • Reduced microleakage • Some dental adhesives result in stable chemical adhesion to hydroxyapatite when dentin is not etched with phosphoric acid • Some adhesives have antibacterial properties, which may prevent recurrent caries lesions - Clearfil SE Protect (Kuraray Noritake.) contains MDPB (12-methacryloyloxydode- cylpyridinium bromide) - Peak Universal Bond (Ultradent Products, Inc.) contains chlorhexidine Disadvantages of Dental Adhesion • Dentists may mistakenly rely solely on adhesion as the source of primary retention, even in clinical situations in which there is not enough residual tooth structure. Other forms of mechanical retention, such as slots, coves, and retention locks, may be needed when more than half of the coronal tooth structure has been compromised • Small uncured monomers, such as HEMA, may seep into the pulp space and cause pulp inflammation • Potential for marginal bacterial leakage when the cavo-surface margin is located in dentin/ cementum • Moisture contamination of the operatory field may be more detrimental for adhesive than for non-adhesive restorations. Introduction Enamel is composed of 96%/weight hydro- xyapatite (mineral). Dentin, on the other hand, contains a significant amount of water and organic material, mainly type I collagen. While bonding to enamel through the micromechanical interlocking of resin tags within the array of microporosities in acid-etched enamel can be reliably achieved, and can effectively seal the restoration margins against leakage, bonding to dentin remains the greatest challenge in adhesive dentistry. Indications for Dental Adhesives • Direct anterior composite restorations • Direct posterior composite restorations • Indirect composite restorations • All-porcelain restorations, including zirconia • Orthodontic brackets • Pit and fissure sealants • Fiber-reinforced posts • Splints for periodontally-involved teeth and luxated teeth • Root desensitization • Reattachment of fractured tooth fragments • Endodontic sealer • Internal reinforcement of fragile endodontically treated teeth Contraindications for Dental Adhesives • Patients with known allergies to resin-based materials and other components • Direct application in deep preparations of vital teeth (<0.5mm from the pulp) • Contamination of the operating field - use of a rubber dam may optimize the outcome Consequences of Inadequate Adhesion • Bacterial leakage • Pulpal inflammation • Recurrent caries • Marginal gaps • Fractured restorations • Dental sensitivity • Compromised esthetics • Compromised function Etching enamel with phosphoric acid 1 has been considered the gold standard 2 for bonding resin- based materials to tooth structure since Dr. Michael Buonocore used 85% phosphoric acid in 1955 to make the enamel surfaces more suitable for mechanical adhesion. 1 Buonocore later expanded the acid-etch technique to seal pits and fissures, as reported in 1967. 3 The micro- mechanical nature of the interaction of adhesives with enamel is a result of the infiltration of resin monomers into the numerous microporosities left by the acid dissolution of enamel (Figure 1). 2 Figure 1 SEM image of enamel etched with 35% phosphoric acid for 15 seconds. Note the multitude of microporosities created by the dissolution of hydroxyapatite by the etch mak- ing the substrate extremely retentive. Original magnification = X2,500.