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Thursday, October 22, 2015
Using an Er,Cr:YSGG laser to remove lithium disilicate restorations: A pilot study
Journal of Prosthetic Dentistry
Article in press
Statement of problem
use of lasers is growing widely in dentistry. Despite its clinical
implications, most information and clinical data related to the removal
of ceramic restorations with the aid of a laser is either anecdotal or
in the form of clinical reports.
purpose of this in vitro study was to establish a parameter on the
removal of lithium disilicate crowns with a laser and conduct an
in vitro trial of crown removal based on the wattage and time of
Material and methods
extracted molars were prepared to accommodate a lithium disilicate disk
specimen, which was cemented with resin cement. An erbium,
chromium-doped yttrium, scandium, gallium, and garnet (Er,Cr:YSGG) laser
was applied at different wattages (3, 3.5, 4, and 5 W) to determine the
optimal wattage for the removal of the lithium disilicate specimens.
Once the optimal wattage was established, 25 extracted teeth were
mounted in stone, then prepared to receive milled lithium disilicate
computer-aided design/computer-aided manufacturing complete coverage
crowns. The crowns were cemented with a dual-polymerizing resin cement.
The groups comprised 3.5 and 4 W output with 30-, 60-, and 90-second
application time (n=5), and 5 crowns were removed using traditional
handpiece and electric handpiece with coarse grit diamond rotary
instruments. The results and time required to remove the crown were
recorded. The chi-square test was performed to assess any significant
differences in removing the crown with the laser according to wattage or
time of application (α=.05).
application at 3.5 and 4 W was best for removing crowns conservatively.
Eight crowns (40%) of 20 specimens were successfully removed at the
first attempt. The majority of the crowns came off during the second
attempt. The chi-square test revealed no significant difference between
the combination of wattage and time of application (P= .92).
The mean time to remove the lithium disilicate crown with a diamond
rotary instrument was 6 minutes, and removal required 1.8 instruments on
An Er,Cr:YSGG laser can safely remove lithium disilicate crowns with the settings used this study.