M. Groten et al., MARGINAL FIT CONSISTENCY OF COPY-MILLED ALL-CERAMIC CROWNS DURING FABRICATION BY LIGHT AND SCANNING ELECTRON-MICROSCOPIC ANALYSIS IN-VITRO, Journal of oral rehabilitation, 24(12), 1997, pp. 871-881
The aim of this study was to evaluate the marginal fit of copy-milled
Celay In-Ceram(R) crowns after different fabrication steps and to comp
are light-microscopic with scanning-electron-microscopic data. A maste
r steel die of an upper middle incisor with a shoulder preparation and
a rounded inner line angle was used. Impressions were taken to produc
e 10 working stone dies. One crown per working die was manufactured. T
he evaluation of the external marginal gap was performed on the master
steel die by using a light microscope and a computerized video image
analysis system after copy milling (A), glass infiltration (B), and ve
neering (C). Approximately 3900 readings were taken. In a final series
the veneered crowns were measured by using a scanning electron micros
cope (Cs), yielding approximately 1000 readings. The results obtained
were: A mean, 25.1 mu m; s.d., 5.1 mu m; range, 2.5-76.8 mu m: B mean,
20.6 mu m; s.d., 2.3 mu m; range, 2.5-76.1 mu m: C mean, 18.3 mu m; s
.d., 4.1 mu m; range, 2.5-87.2 mu m: Cs mean, 23.0 mu m; s.d., 7.6 mu
m; range, 0.0-94.5 mu m. The results were statistically evaluated usin
g the t-test. The differences found between the series did not show pr
actical relevance. Therefore, it is concluded that the manufacturing s
teps after copy milling have no obvious influence on the external marg
inal gap width. Scanning electron microscopic data seem to confirm the
light-microscopic results. Hence, we expect that the Celay In-Ceram m
ethod yields a clinically acceptable marginal fit.