Fracture resistance of Class II approximal slot restorations

Statement of problem. Determination of the Fracture resistance of various r estorative materials in Class II approximal slot restorations has not been studied. Purpose. This study evaluated the effects of retention grooves and differen t restorative materials in Class II approximal slot restorations. To explor e the possibilities for further research, the probable effects of preparati on size and loading angle were investigated in a limited manner. Material and methods. Ninety sound, caries-free human maxillary premolars w ere divided into 9 groups. The cavities were prepared either by hand or in a computer-controlled CNC machine with or without retention grooves. Four w ere restored with adhesive amalgam, another 4 with composite, and a single group with Compomer resin. The gingival floor depth was 1.5 mm. The specime ns were loaded at an angle of 13.5 degrees to their longitudinal axes by us ing a computer-controlled material testing machine until failure occurred. For one specific preparation of adhesive amalgam, loading was applied at 0 and 30 degrees to determine the probable effects of the loading angle. For a specific composite, resin application, the effects of the change in gingi val floor depth were analyzed by assigning the depth to 2.0 mm. Results. Composite and Compomer resin and composite exhibited better perfor mance than amalgam. The existence of the retention grooves proved to be eff ective for adhesive amalgam restorations but did nor. have any advantageous effect in composite and Compomer restoration. Conclusion. For improved fracture resistance in small approximal restoratio ns, the use of composite was the appropriate choice. Compomer also gave sat isfactory results. Use of amalgam restoration should be accompanied with re tention grooves and an adhesive system to improve its performance.