Effects of staining and bleaching procedures on the optical and surface properties of CAD-CAM materials

To examine the effects of coffee staining and bleaching applications on the optical properties of CAD-CAM blocks, and to provide a three-dimensional visualization of surface changes with atomic force microscope (AFM).

80 samples were prepared from four different CAD-CAM blocks: [Cerec (CR), Shofu (SH), Cerasmart (CRS), Lava Ultimate (LU)], and a microhybrid composite resin [Filtek Z250 (Z250)]. After staining, the samples were divided into two subgroups according to bleaching methods: 16% carbamide peroxide (HB), and 40% hydrogen peroxide (OB). Color measurements were performed at baseline (t₀), after staining (t₁), and after bleaching (t₂) to obtain translucency parameters (TP₀₀), color change (ΔE₀₀), and whiteness index (WID) values. Surface roughness analysis (Ra) was performed with AFM after coffee staining and bleaching procedures (at t₁ and t₂). Data were analyzed with Generalized Linear Model, and Bonferroni correction (P< 0.05).

TP₀₀ values increased only in the CRS group after the bleaching application, and the effect of method was again observed only in CRS. While bleaching increased WID values of all groups except CRS, no difference was found between bleaching methods. Regardless of evaluation time, the roughest group is Z250, and the only difference between bleaching methods was observed in the CR group. In conclusion, the effects of staining and bleaching applications on the optical and surface properties of CAD-CAM blocks are material-dependent.

Effective bleaching of discolored CAD-CAM materials was achieved regardless of the bleaching method used, and without any significant adverse effect on the surface properties of the materials.