A Study on Topographical Properties and Surface Wettability of Monolithic Zirconia after Use of Diverse Polishing Instruments with Different Surface Coatings

Abstract

Purpose: To investigate the surface topography parameters and wettability of monolithic zirconia (MZ) using polishing instruments with different coatings. Materials and Methods: MZ specimens (N = 50, n = 10 per group) (12 × 12 × 1.8 mm3) were highly polished. Five polishing systems were studied: BG: silicon carbide polishers; CG: diamond-impregnated ceramic polisher kit; EV: synthetically bonded grinder interspersed with diamond; SL: urethane-coated paper with aluminum oxide grits; and DB: diamond bur (8 μm). Specimens were initially roughened with 220 μm grit diamond burs (10 seconds, 160,000 rpm). After baseline measurements, they were further polished for 10 seconds using a slow-speed handpiece under water coolant, except for SL using a custom-made device (7.5 N), with speed ranging between 5000 and 30,000 rpm. Topographical changes were evaluated considering (a) weight (digital scale), (b) volume loss (digital microscope), (c) vertical height loss (digital microscope), (d) surface roughness (Ra) (profilometer), and (e) surface wettability (goniometer, water). Results: Compared to baseline, material loss from the surface after polishing (ΔW) ranged between 0.00 ± 0.0001×10−1 and –0.03 ± 0.008×10−1 g (SLa < CGa < BGa < DBb < EVc) and the volume loss (ΔV) between 900 ± 3×10−5 and 2459 ± 7×10−5 μm3 (SLa < BGa < CGa,b < DBb < EVc). The vertical height loss (∆VH) was highest for SL (–18.911 ± 3.5) and lowest for EV 55.19 ± 6.3 μm (SLa < BGa < CGa,b < DBb < EVc). The surface roughness (μm) difference (∆Ra) was lowest for DB (–0.14 ± 0.02) and the highest for EV (0.86 ± 0.42) (DBa < BGa < SLa < CGa < EVb). BG showed the lowest contact angle difference (∆SW) –2.79 ± 0.8° and EV the highest (3.93 ± 3.1°) (BGa < DBa < SLa < CGa < EVa). Conclusions: All polishing instruments performed similarly when ∆Ra values were considered. SL, BG, and CG produced the least material loss. Synthetically bonded rubber bur interspersed with diamond (EV) could not be suggested for polishing MZ.