Evaluation of optical effect of different shade of resin cement and thermocycling on CAD/CAM blocks

One of the innovations in dentistry developed in recent years is using CAD/CAM technology with chairside restorations in a short time. With the popularity of CAD/CAM systems, new CAD/CAM block materials are developed This study, have been evaluated the optical properties of resin nano ceramic and hybrid ceramic CAD/CAM blocks, which have been used in recently and lithium disilicate which have been used for a long time. This study aims to evaluate the optical effect of different color resin cement and the aging process on CAD/CAM blocks in different thicknesses and translucency. Samples were prepared from 3 different brands of CAD/CAM blocks (LAVA Ultimate, LV, (3M ESPE, USA), GC Cerasmart, GC, (GC Corp, USA), IPS E.max CAD, EM, (Ivoclar Vivadent AG, Germany)). All the specimens were in A2 color, high translucency (HT) or low translucency (LT). CAD/CAM blocks were with the thickness of 0.5 mm, 1 mm or 2 mm (n=16). To simulate the color of the natural teeth 5×6 mm rectangular shape composite substructure (GC Genial, GC Corp, America), was placed at the bottom of the samples (n=1). Resin cement samples (GCem Link Force, GC Corp, America) were prepared in one of the 3 different colors: A2 (A2), transparent (TR), opaque (OP). Samples were prepared in dimensions of 6×5×0.2 mm in rectangular shape (n=1). The color of the composite sample that was mimicking the dentin was measured with the spectrophotometer (CM-2600d, Konica Minolta Sensing, INC. Japan). This ΔE value was accepted as the reference value. Resin cement was placed above the composite sample. Then CAD/CAM block sample was placed on top of the resin cement. Color change according to the reference value was measured with the spectrophotometer. CAD/CAM samples were thermocycled for 10.000 cycles of artificial aging. The color of the CAD/CAM samples were measured by spectrophotometer for the second time after the first measurement. In the first measurement, the samples were placed in the form of layers, and the second-time reference was made by spectrophotometer. Statistical analysis was performed with one-way analysis of variance analysis, Newman Keuls Multiple Comparison tests, paired t-test, Tukey Multiple Comparison tests, independent t-test (p <0.05). In our study, ΔE changes in material variations, the thickness of materials, translucency of materials and between the resin cement were statistically significantly different (p =0.0001). The ΔE values between three different materials before aging from the greatest to the least was LV (x̄= 9.74) EM (x̄=6.99) GC (x̄=5.25). After the aging process, the ΔE values between from the greatest to the least was LV (x̄ = 9.55) EM (x̄ = 6.93) GC (x̄=5.49). The ΔE values between the thicknesses of the materials from the greatest to the least was 2 mm (x̄= 9,04) 1 mm (x̄=7,28) 0,5 mm (x̄=5,76) before the aging process. After aging, ΔE values from the greatest to the least was 2 mm (x̄=8,93) 1 mm (x̄=7,21) 0,5 mm (x̄=5,76). The ΔE values between the translucency of the materials from the greatest to the least was HT (x̄=8.46) LT (x̄=6.20) groups before the aging process. After aging, the ΔE values from the greatest to the least was HT (x̄= 8.41) LT (x̄=6.04) groups. The ΔEvalues between the resin cements of different colors before the aging process from the greatest to the least was TR (x̄=7.65) A2 (x̄=7.49) OP (x̄=7.06). After aging, the ΔE values from the greatest to the least was TR (x̄ = 7.85) A2 (x̄ = 7.46) OP (x̄= 6.84). The order of groups ΔE values before and after the thermocycling did not change. The effect of aging on materials was different from each other. The ΔE changes between pre and post-aging process were clinically acceptable value (ΔE3.5). Key Words: Hybrid CAD/CAM Blocks, Color, Thickness, Resin Cement, Thermocycling