Performance of Reinforced 3D-Printed Versus Direct Bulk-Filled Resin Composites for Restoring Extensive Class II Cavities in Vital Molars

Tooth preparation for indirect inlay restorations follows conservative restorative principles, with the primary objective of eliminating carious tissue and unsupported enamel while preserving as much healthy tooth structure as possible. The preparation design emphasizes mechanical stability, stress distribution, and optimal seating of the final restoration. Cavity walls are shaped with a slight occlusal divergence of approximately 6-10°, facilitating proper insertion and seating of the inlay without compromising retention. The pulpal floor is prepared flat to enhance resistance form, and all internal line angles are rounded to minimize stress concentration within both the tooth and the restorative material. Cavosurface margins are ideally prepared as supragingival butt-joint margins whenever clinically feasible, promoting periodontal health, improved isolation, and easier finishing procedures. Cuspal coverage is generally avoided in inlay preparations to maintain maximum tooth integrit

For restoration of Class II cavity preparations, a sectional metal matrix system (TOR VM, Russia) will be used to properly reestablish proximal anatomy and contact. The system includes a round separation ring and a pre-contoured metal band designed to reproduce natural proximal contours. A properly sized wedge is inserted to ensure optimal gingival adaptation of the matrix band and to prevent overhangs. The cavity is thoroughly rinsed with water before proceeding with adhesive procedures. Selective enamel etching is performed using 37% phosphoric acid gel applied to enamel margins for 15 seconds, followed by thorough rinsing and gentle air-drying. A universal adhesive system, Tetric N-Bond Universal (Ivoclar Vivadent AG), is then applied in two consecutive layers. Each layer is actively rubbed for 10 seconds, gently air-dried for 5 seconds, and light-cured for 20 seconds to ensure adequate polymerization and bond strength. Restoration is completed using Tetric N-Ceram Bulk Fill resin c