Effects of different polishing protocols on the surface roughness of Y-TZP surfaces used for custom-made implant abutments: A controlled morphologic SEM and profilometric pilot study

Abstract

Statement of problemLimited information is available on how to treat the surface of computer-aided design/computer-aided manufacturing (CAD/CAM)-derived implant abutments made of yttria tetragonal zirconia polycrystal (Y-TZP). PurposeThe purpose of this study was to assess and compare 4 different standardized polishing protocols of dental zirconia with a standard handpiece and abrasives and to identify a standardized protocol to obtain a surface roughness of Ra=0.2 μm on dental Y-TZP. Material and methodsForty specimens of Y-TZP were produced and finished with 4 different polishing protocols with standard dental abrasives. Protocol Co used a coarse rubber abrasive, protocol Me used the rubber abrasive of protocol Co plus a medium rubber abrasive, protocol Fi used the polishing sequences of protocol Me plus a fine rubber abrasive, and protocol UF used protocol Me plus ultrafine high-gloss polishing. Ten machined titanium disks served as control (C). Roughness measurement and scanning electron microscopy was performed for each specimen and tested for differences with ANOVA with Bonferroni correction and the Student t test (α=.05). ResultsIn the zirconia groups, Co (Ra 0.29 ±0.38 μm) showed significantly higher Ra values than Me (Ra 0.22 ±0.38 μm; P=.003), Fi (Ra 0.17 ±0.37 μm; P<.001), and UF (Ra 0.07 ±0.06 μm; P<.001). UF showed the significantly lowest Ra values of all zirconia groups (Co and Me: P<.001, Fi: P=.002). Differences between Me and Fi were not significant (P=.116). Comparison of the 4 zirconia surfaces to the control group (C; Ra=0.17 ±0.03) revealed significant differences for Co (P<.001) and UF (P=.006) but not Me (P=1.000) and Fi (P=.055). In comparison with the literature-based optimal roughness of Ra=0.2 μm, significant differences were found for Co, Fi, and UF (P<.05), but not for Me (P=.117). However, the machined titanium surface (C) also showed significantly smoother Ra values than 0.2 μm (P<.05, Student t test). ConclusionsA roughness of Ra=0.2 μm on zirconia can be achieved by following protocol Me, whereas a roughness comparable to machined titanium is present after protocol Fi.