Micro-fine finishing of a feldspar porcelain for dental prostheses

Intraoral adjustment of ceramic prostheses involving micro-finishing using diamond burs is a critical procedure in restorative dentistry because the durability of a restoration depends on the finishing process and quality. Force, energy and surface integrity in micro-fine finishing of a feldspar porcelain versus operational parameters were investigated using a 2-DOF (two-degrees-of-freedom) high-speed dental handpiece and a fine diamond bur of 20-30 microm grits. The tangential and normal forces were measured as being significantly small in the ranges 0.18-0.35 N and 0.22-0.59 N, respectively. High specific finishing energy of 110-2523J/mm(3) was observed in material removal, particularly when decreasing either the depth of cut or the feed rate. Scanning electron microscopy observations indicated that the surfaces generated were mainly due to ductile flow; however, microfractures also occurred in porcelain. Surface roughness was measured as 0.43-0.74 microm in terms of arithmetic mean value (R(a)), decreasing with the depth of cut, but insignificantly changing with the feed rate (ANOVA, P>0.05). Recommendations for clinical practice are made on the basis of our testing results.