In-vitro investigation of the effect of clinical factors on the color of ceramic glass/polymer based CAD/CAM materials

The aim of this in vitro study is to investigate the effect of clinical factors on the color of ceramic/glass polymer based CAD/CAM materials. In the study, square (12 × 12 mm2) prism shaped specimens of 3 different thicknesses (1 mm, 1,5 mm ve 2 mm) were cut from nano-hybrid and polymer infiltrated ceramic network CAD/CAM blocks (N=370). 36 subgroups were formed based on the material type, material thickness, abutment tooth shade and cement shade (n=10). The remaining 10 ceramic/glass polymer based specimens were used as the control group. One side of the specimens was polished with 1200 and 4000 grit SiC sandpaper, respectively. Representing the abutment tooth, 360 disc shaped (⌀=10 mm, h=3 mm) composite resin specimens were fabricated in B1 and C3 shades. Composite resin discs were cemented under 10 N force using 3 different shades (A2, White, Translucent) of dual-polymerized self-adhesive resin cement of 100 µm thickness on the 360 of ceramic/glass polymer based CAD/CAM specimens. The color change of the test materials in the control and test groups was measured on a black background using a spectrophotometer and calculated according to the CIEΔE 2000 color difference formula. Color change (∆E00) results of test specimens were evaluated by Kruskal-Wallis and Mann-Whitney U tests (p<0.05). A statistically significant difference was observed between ∆E00 values in terms of dental CAD/CAM restorative materials, cement shades and material thickness in both abutment shades (p<0.05). The restoration combination prepared with polymer infiltrated ceramic network material exhibited lower ∆E00 values than those prepared with nano-hybrid material in both abutment shades. In addition, the triple interaction was found amongst restorative material-material thickness-cement shade in both abutment shades caused a significant difference on ΔE00 values (p <0.05). Clinical factors such as material type, thickness and cement color affect the final color of CAD/CAM restorations when different shades of abutment teeth are present. Regardless of the underlying abutment tooth shade, the use of White cement and materials with a thickness of 1 mm causes a clinically significant color change and this combination adversely affects the desired final color of the restoration.