Method: Minimal inlay and crown preparations were proposed. Phantom teeth were used. Gauged burs (Intensiv SA; Meissinger Germany) were used to standardise preparations. CEREC Scan/CEREC 3D was used for scanning and designing. Different milling modes were tested (1.6 cylinder, 1.2 cylinder, Endo). The materials tested were ProCAD (Vivadent-Ivoclar) VITA Mark II (VITA) and Paradigm MZ100 (3M ESPE). The morphology, marginal integrity and materials' integrity were examined.
Results: SEM and optical microscopy showed that Paradigm MZ100 produced acceptable crowns with intact margins for the most conservative design (0.4 mm chamfer, 0.6 mm occlusal reduction). VITA Mark II produced acceptable crowns for 0.6mm chamfer margins and 1.2 mm occlusal reduction, whereas ProCAD needed a wider preparation design (0.8mm chamfer margins, and 1.2 mm occlusal reduction). The Endo setting proved most effective for the crown restorations. Transillumination and dye penetration showed no signs of cracks for all materials for these preparation depths. For the inlay preparation it was found that all materials were able to produce the initially proposed minimal design (1.0mm occlusal reduction, 1.0mm proximal box width, U-shaped box, parallel walls).
Conclusions: Within the limits of this study the following conclusions were drawn:
-With regard to the crown preparation only with composite material a more conservative tooth reduction can be achieved
-With ceramic materials minimal preparations can still be applied but less conservative when compared to the composite material
-For the inlay preparation all materials produced the proposed minimal preparation design.