Surface characteristics of dental resin nanoceramic in in vitro finishing with dental handpiece and rotary burs

Abstract

Surface roughness and texture are critical characteristics of dental restorative materials in determining the clinical performance of dental prostheses. This study aimed to quantitatively assess the effects of dental rotary finishing process, necessarily involved in clinical practice, on surface roughness and texture of dental resin nanoceramic (RNC). In vitro dental finishing was conducted on a computer-assisted apparatus with a dental handpiece and diamond burs. Four clinically applied finishing parameters (diamond grit size, depth of cut, feed rate and rotational speed) were selected. The finished surface topographies were measured based on optimized sampling conditions. The 3D amplitude parameters of Sq and Sz, functional parameters of Sbi and Sci, and spatial texture parameters of Sal and Str were obtained using a 3D no-contact chromatic confocal profilometer, and then were calculated and statistically analyzed using ANOVA for surface characterization. The results show that diamond grit size had significant effects on the all surface parameters of Sq, Sz, Sbi (P < 0.01), and Sal, Str, Sci (P < 0.05), while bur rotational speed was irrelevant to the parameters (P > 0.05). The functional parameters of Sbi and Sci relied mainly on diamond grit size and feed rate (P < 0.05). Standard bur and medium bur easily caused deep valleys on the RNC surface, while finer burs or slower feed rates could improve bearing property but diminish core liquid remained property. Small girt size, slower feed rate and decreased rotational speed could generate more regular and finer surface texture. Implications concerning the relationship between surface roughness and finishing process parameters were provided to facilitate the process selection and quality control of RNC prostheses.