A heat-pressed technique (IPS Empress(R), Ivoclar) has been described
to construct single unit crowns, inlay/onlays and veneers using precer
ammed and precoloured glass-ceramic ingots, The aim of the study was t
o evaluate the strength of materials obtained using this technique. St
rengths were determined by means of shell (disc rupture) tests. Seven
groups of 10 specimens each were prepared with different combinations
of core, incisal and glaze firing. Shell strength values of these seve
n groups varied between 167 +/- 18 and 81 +/- 9 MPa. After analysis, r
esults showed that there was no statistical difference between groups
when the core porcelain was in tension. However, there was a significa
nt difference between those groups in which the lower surface was eith
er core or incisal porcelain. The component thicknesses of the core an
d incisal materials did not change the strength of the complete specim
en.