Purpose: The purpose of this study was to examine the effects of the occlusal convergence
angle of the abutment and the computer’s luting space setting on the marginal and internal
fit of Cerec 3 computer-aided design/manufacturing (CAD/CAM) all-ceramic crowns.
Materials and Methods: Mandibular second premolar all-ceramic crowns were fabricated
for nine different conditions using Cerec 3: all combinations of abutments with three
different total occlusal convergence angles (4, 8, and 12 degrees) with three different luting
space settings (10, 30, and 50 µm). The completed crowns were seated on the abutments,
and the marginal gaps were measured. The internal gaps between the crowns and
abutments were also measured, using test-fit silicone paste. Results: When the luting space
was set to 10 µm, the marginal gaps of the crowns were greater than when it was set to 30
or 50 µm. When the luting space was set to 30 or 50 µm, the marginal gaps ranged from 53
to 67 µm and were not affected by the occlusal convergence angle of the abutment. The
internal gaps were within a range of 116 to 162 µm and tended to decrease as the occlusal
convergence angle of the abutment decreased. Conclusion: When the luting space was set
to 30 µm, crowns with a good fit could be fabricated on the Cerec 3 system, regardless of
the occlusal convergence angle of the abutment. Int J Prosthodont 2003;16:244–248.