Microstructure, topography, surface roughness, fractal dimension, internal and marginal adaptation of pressed and milled lithium-disilicate monolithic restorations

Abstract

PurposeTo characterize the effect of two processing techniques (pressing and CAD/CAM — Computer Aided Design/Computer Aided Machining) of lithium-disilicate (LD) based crowns on the microstructure, topography, roughness, fractal dimension, internal and marginal adaptation. MethodsOne-hundred identical preparations for monolithic crowns were made with dentin analogue material (G10 epoxy resin). One of the preparations was scanned and a monolithic crown in lithium-disilicate was planned in the CAD system. Fifty crowns were milled in a wax pattern and subjected to pressing (IPS e.max Press), while 50 crowns were machined at CAD/CAM (IPS e.max CAD) and posteriorly crystallized. Internal and marginal adaptation were assessed via replica technique at four manufacturing moments (Milled wax pattern; LDPRESS; Milled LDCAD; Crystallized LDCAD) and considering 5 regions (margin, cervico-axial angle, axial wall, axial-occlusal angle and occlusal wall). Complementary analysis considering microstructure and topography, roughness and fractal dimension were performed in Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). ResultsThe processing technique resulted in different ceramic microstructure, topography, roughness and fractal dimension, whereas CAD/CAM lead to smoother, more homogeneous but more complex topography features (higher fractal dimension) in comparison to the pressing technique (P<0.05). Regarding marginal and internal fit, LDPRESS crowns showed to be more adapted at the margin, while LDCAD were more adapted at the occluso-axial angle; other regions were not statistically different (α=0.05). ConclusionsCAD/CAM and the pressing techniques for manufacturing LD crowns lead to completely different ceramic surface characteristics and affect crown adaptation at the margin and at occluso-axial angle.