PENETRATION OF AMALGAM CORRODED PRODUCTS INTO DENTIN AND ITS EFFECT ON BONDING USING SELF ETCH ADHESIVE SYSTEM VERSUS RESIN MODIFIED GLASS IONOMER

Introduction: amalgam replacement by tooth-colored restorations has become a common procedure nowadays. Aim: this study was carried out to detect the effect of Penetration of amalgam corroded products into dentin on bonding of both self etch adhesives and resin modified glass ionomer (RMGI). Materials & method: 40 simple occlusal cavities were made in human extracted molars. Cavities were filled with amalgam, stored for one year then amalgam was removed and teeth were divided into two main groups (20 teeth each); group A; where amalgam was without any further increase in cavity depth. Group B; where amalgam was totally removed followed by further increase in cavity depth by 0.5 mm. each group was re divided according to the restorative material used to replace amalgam where group 1: resin composite with self etch adhesive, group 2: RMGI. Teeth were sliced and the interface was examined by scanning electron microscope coupled with EDAX. Results: amalgam remnants appeared at the interface of group A to interfere with bonding while it disappeared from the interface at group B. conclusion: increasing depth of the cavity by 0.5 mm after amalgam removal showed a more reliable interface for the subsequent tooth colored restoration. (3586) Ali Essam Abdelnabi and Nermeen Kamal Hamza E.D. J. Vol. 63, No. 4 can be adhesively bonded to enamel and dentin with the use of appropriate bonding systems. Accordingly, less invasive cavity designs are indicated for resin restoration. Moreover, other types of tooth colored restorative materials such as glass ionomer, resin modified glass ionomer and compomers have their own short comings such as inadequate wear characteristics and low fracture toughness. Thus they could not be substitute to resin composite restorations especially for restoration of posterior teeth, but still resin modified glass ionomer could be used as a base under resin composite restoration (Fusayma et al 1966, Ben-Amar et al 1995). Continuous development in the field of adhesive resins has yielded in different types of simplified adhesives to meet the demand for more user-friendly adhesive techniques. The combination of primer and adhesive resin to one product still requires the application of several layers of adhesive resin but the number of bottles is reduced. In two step-self etch system, the acid conditioning and priming steps are combined. In such adhesive systems, the acidic primer dissolves smear layer and demineralizes superficial dentin, meanwhile, penetrating into dentin. After evaporation of solvents, the adhesive resin is applied onto the primed dentin that diffuses into the liquid priming without a rinsing step. The ultimate and most recent self-etch system, also called all-in-one adhesive, combining the conditioning, priming and bonding phases only in one step. At present, adhesives resins based on acidic functional monomers, such as 10-methacryloxy decyl dihydrogen phosphate (10MDP), carboxylic groups and copolymers are capable of chemical interaction with the mineral component of dentin. Most adhesion studies on dentin have been performed on sound or caries affected dentin. In case of replacement of restorations the underlying dentin exhibits a variety of micro-structural changes and considered as heterogeneous tissue, due to the penetration of corroded products into dentinal walls that will affect the adhesion of resin composite (Jensen et al 1982, Hals et al 1988). Glass ionomer possess several beneficial properties, including physic-chemical adhesion to tooth structure and release of fluoride ions (Walls 1986). Glass ionomer have gained acceptance as liners, luting agents and core material, but their use as a restorative material has been less common (Reinhardt 1993). Compared with resin composite, the glass ionomer are relatively unesthetic and have poor physical properties, including low flexural strength and fracture toughness. Furthermore, they undergo a long and complex setting reaction and are easily damaged by excessive moisture and desiccation (Mount & Makinson 1991). In order to overcome these advantages, several manufacturers have recently developed resin modified glass ionomer restorative materials that are hybrid of conventional glass ionomer cements and visble light activated resin composite. They are more esthetic and less water sensitive than conventional glass ionomer, but they are still less esthetic and lower strength than resin composite. Several researches showed that resin modified glass ionomer have higher dentin bond strength than conventional glass ionomer (Burges & Burkett 1993). Therefore, the objective of this study was to evaluate the influence stained dentin penetrated by corroded products on the formation of hybrid layer using self etch adhesive system with rein composite restorative material versus chemical bonding of rein modified glass ionomer. MATERIALS AND METHOD