Approximal margin adaptation on class II – posterior interproximal cavity restored with open and closed sandwich technique

The sandwich technique is used for restoring class II caries where glass-ionomer cement is used as a liner under some composite restorations. There are two variations of the sandwich technique, the open sandwich and the closed sandwich technique. The open sandwich technique involves the placement of glass ionomer cement into the base of a proximal cavity and filling the preparation with glass ionomer up to the level of the dento-enamel junction. The final portion of the restoration is placed with composite resin to provide wear resistance and aesthetics on the occlusal surface. The closed sandwich technique involves placing the glass ionomer at the base of the proximal box so as it falls just short of the external cavo surface. After setting, the glass ionomer is etched and a dentine bonding agent is applied before placing a composite resin into the proximal box and occlusal surface, leaving the glass ionomer cement encased within the preparation. In this study we will test the approximal margin adaptation on teeth restored using both open and closed sandwich techniques. On 30 extracted teeth we prepared class II cavities where 15 of them were restored using the closed and 15 using the open sandwich technique. The teeth around the margins of the restoration (the crown and root) were then isolated using varnish which is not permeable for methylene blue, then they were placed in a solution of methylene blue to check the micropermeability of the margins. In that solution the teeth were kept seven days and after that they were cut in longitudinal sections. Under microscope we checked the marginal adaptation of the teeth restored using closed and open sandwich technique i.e. if the margins on the longitudinal section were colored in blue. All the teeth in our study had a very good marginal adaptation, no significant differences were found in the teeth restored using the open sandwich technique and closed sandwich technique. Because of the properties of the glass ionomer cement, as listed in various 52 literature: (1) the glass-ionomer material bonds both to the tooth structure and the composite, thereby increasing retention form; (2) fluoride contained in the glass-ionomer material reduces the potential for recurrent caries; and (3) the glass-ionomer material, because of its bond to tooth structure, provides a better seal when used at non-enamel margins; the marginal adaptation was very good on our test subjects, which implies that in clinical use these techniques may provide a good alternative for restorations to minimize the chances of seconder caries formation. Keywords: class II restoration, closed sandwich technique, marginal adaptation, open sandwich technique