Abstract
Purpose: The effect of CO2 continuous laser irradiation on the surface properties of veneering porcelains has already been tested. The surface observed after laser irradiation is similar to that achieved by auto-glaze in terms of roughness and color parameters (Sgura R, et al. Dental Materials 2011;27(Suppl. 1):e72–73). The purpose of this study was to analyze the surface porosity of porcelain discs after CO2 laser treatment and compare it to auto-glaze treatment, in furnace. A morphological analysis of the porcelain surface was conducted using atomic forcemicroscopy (AFM) and conventional optical microscopy (OM). Methods and materials: 60 disks (diameter 3.5mm×2.0mm) of veneering porcelain for Y-TZP frameworks (VM9 – VITA Zahnfabrik) were sintered and had one of their faces mirror polished. The specimens were divided into groups (n=10) according to surface treatment: no treatment – control (C); auto-glaze in furnace following manufacturer’s instructions (G); and CO2 laser (45 or 50W/cm2) applied for 4 or 5min (L45/4, L45/5, L50/4, L50/5). OM (HMV – Shimadzu – 100×) was conducted and the images were analyzed with Image J software (public domain) for the determination of the porosity parameters: area fraction, average size and Feret’s diameter. Mean values were submitted to ANOVA and a Tukey post-hoc test (p<0.05) when the data were homecedastic. For non homocedastic data, the Kruskall–Wallis test was used. Contact AFM (50×50 m2 – Nanoscope IIIA, Veeco) was performed at the center of one sample of each group, except for group L45/5. 3D image processing was carried out with MS×M 5.0 software (Nanotech). Results: The area fraction of pores after laser irradiation was similar to that obtained for group G. For irradiated specimens, AFM showed the formation of valleys and elongated peaks with rounded edges. OM images revealed surface grooves in 50W/cm2 groups. Conclusion: Both irradiances (45 and 50W/cm2) produced a surface comparable to auto-glaze in terms of surface porosity. The irradiance of 50W/cm2 resulted in changes in surface morphology for VM9 porcelain, observed under optical microscopy.
Published Version
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