Polishing vs. Glazing: contemporary trends and experimental color analysis on a phantom model

The continuous advancement of aesthetics and functionality in fixed prosthodontic restorations has led to growing interest in the influence of surface finishing techniques and their physico-optical properties. Polishing and glazing are two fundamental methods of surface treatment that significantly affect the visual appearance, biocompatibility, and longevity of prosthetic restorations.The primary aim of this study was to conduct a comparative analysis of the esthetic differences, expressed through color change (ΔE), between polished and glazed surfaces across various types of fixed prosthodontic materials. The samples were fabricated for an anatomical phantom model (KaVo™ DPS Epoxy Modell) owned by the University "Goce Delchev" –Štip. All crowns were designed for the upper left central incisor, which had been previously prepared and digitally scanned. The shade selection was based on the Vitapan Classical shade guide, specifically in shade A2.The study was conducted using a non-contact intraoral spectrophotometer (ShadePilot™; DeguDent, Germany) with a 45/0° optical geometry. This device is housed in the Dental Research Laboratory at the Faculty of Medical Sciences, University "Goce Delchev" –Štip. The analysis and data processing were performed using the dedicated software Windows Software Version 3.01.1007a.A total of 180 samples were included in the study, categorized into three main groups, each consisting of 60 samples, further divided into two subgroups of 30: metal-ceramic restorations, zirconia restorations with veneered ceramic, and monolithic full-contour zirconia restorations. In each group, one subgroup consisted of polished samples, while the other comprised glazed samples. Color change (ΔE) was measured for each specimen under standardized daylight conditions.The results showed that glazed surfaces exhibited lower ΔE values compared to polished ones across all materials. In the metal-ceramic group, the mean ΔE value was slightly lower for glazed samples but without statistical significance (Z = -2.877; p = 0.004). In contrast, for both full-contour zirconia and veneered zirconia restorations, the differences were statistically significant (Z = -2.877; p = 0.004 and Z = -3.832; p = 0.0001, respectively), with lower ΔE values in the glazed subgroups.These findings suggest that the choice of surface finishing technique has a tangible impact on the optical properties of restorations, particularly in zirconia-based materials. The study highlights the importance of selecting an appropriate surface finishing method according to the material used, in order to achieve optimal esthetic outcomes and clinical efficiency.
Keywords: fixed prosthodontics, polishing, glazing, zirconia, metal-ceramic, color