Recently,
zirconia removal diamond rotary instruments have become commercially
available for efficient cutting of zirconia. However, research of
cutting efficiency and the cutting characteristics of zirconia removal
diamond rotary instruments is limited.
Purpose
The
purpose of this in vitro study was to assess and compare the cutting
efficiency, durability, and diamond rotary instrument wear pattern of
zirconia diamond removal rotary instruments with those of conventional
diamond rotary instruments. In addition, the surface characteristics of
the cut zirconia were assessed.
Material and methods
Block
specimens of 3 mol% yttrium cation-doped tetragonal zirconia
polycrystal were machined 10 times for 1 minute each using a high-speed
handpiece with 6 types of diamond rotary instrument from 2 manufacturers
at a constant force of 2 N (n=5). An electronic scale was used to
measure the lost weight after each cut in order to evaluate the cutting
efficiency. Field emission scanning electron microscopy was used to
evaluate diamond rotary instrument wear patterns and machined zirconia
block surface characteristics. Data were statistically analyzed using
the Kruskal-Wallis test, followed by the Mann-Whitney U test (α=.05).
Results
Zirconia
removal fine grit diamond rotary instruments showed cutting efficiency
that was reduced compared with conventional fine grit diamond rotary
instruments. Diamond grit fracture was the most dominant diamond rotary
instrument wear pattern in all groups. All machined zirconia surfaces
were primarily subjected to plastic deformation, which is evidence of
ductile cutting. Zirconia blocks machined with zirconia removal fine
grit diamond rotary instruments showed the least incidence of surface
flaws.
Conclusions
Although zirconia
removal diamond rotary instruments did not show improved cutting
efficiency compared with conventional diamond rotary instruments, the
machined zirconia surface showed smoother furrows of plastic deformation
and fewer surface flaws.
Comments