Isomet 11 1180 low speed saw

For the upper restoration layer, CAD-CAM composite resin blocks (Brilliant Crios, Coltène/Whaledent AG, Alstätten, Switzerland) with the dimension of 14x14x18 mm were sectioned perpendicularly to their longitudinal axis using a low-speed saw (IsoMet 11-1180 Low Speed Saw, Buehler Ltd, Illinois, IL, USA) to produce 80 slabs with a thickness of 0.5±0.05 mm (n=20), 1±0.05 mm (n=20), 1.5±0.05 mm (n=20) and 2±0.05 mm (n=20). Squared slabs were then reduced to discs with a diameter of 9 mm with a water-cooled drilling trephine.

The crowns were separated using a diamond disc (Isomet 11-1180 low speed saw, Buehler Ltd., Lake Bluff, Ill., USA; 101.67 mm diameter, 0.3 mm thickness). Each tooth was then ground longitudinally up to 1 mm from the measurement site on a Knuth Rotor polishing machine (Struers, Ballerup, Denmark) with silicone carbide paper of 60 μm grain size under cooled tap water. The progression of the grinding process was constantly checked under a microscope (Leica) at a magnification of ×6.25. When the periphery of the site was reached, silicone carbide paper with a grain size of 30, 18, 8 and 5 μm was sequentially used. Photographs of the ground site were taken at ×6.25 using a microscope (Leica). The cut surfaces were cleaned and stained with rhodamine B (Inselspital-Apotheke, Bern, Switzerland). The surfaces were then photographed at ×10 (Leica) and scored by two experienced examiners using the Marthaler classification [1966] : D 0 = no caries; D 1 = caries extending to the outer half of enamel; D 2 = caries extending to the inner half of enamel; D 3 = caries extending to the outer half of dentine; D 4 = caries extending to the inner half of dentine.
Histology served as the gold standard for further statistical evaluation.