Fabrication of crown restoration retrofitting to existing clasps using CAD/CAM: Fitness accuracy and retentive force
Available online 7 February 2015
Abstract
Purpose
A
crown restoration engaged by a clasp as an abutment tooth for a
removable partial denture (RPD) occasionally might be removed and
eliminated due to secondary caries or apical lesions. However, if the
RPD is clinically acceptable without any problems and refabricating the
RPD is not recommended, the new crown must be made to retrofit to the
existing clasp of the RPD.
This in vitro
study evaluated the conventional and CAD/CAM procedures for retrofitting
crown restorations to the existing clasps by measuring the fitness
accuracy and the retentive forces.
Methods
The
crown restoration on #44 was fabricated with CP titanium and zirconium
on the plaster model with #45 and #46 teeth missing to retrofit to the
existing clasp using conventional thin coping and CAD/CAM procedures.
The gap distance between the clasp (tip, shoulder, and rest regions) and
the fabricated crown was measured using silicone impression material.
The retentive force of the clasp was also measured, using an autograph
at a crosshead speed of 50 mm/min. The obtained data were analyzed by
one-way ANOVA/Tukey's multiple comparison test (α = 0.05).
Results
The
CAD/CAM procedure caused significantly smaller gap distances in all of
the clasp regions, as compared to the conventional procedure (p < 0.05). The retentive force of the CAD/CAM crown was significantly higher than for the conventional one (p < 0.05).
Conclusion
When
a crown restoration must be remade to retrofit an existing clasp,
CAD/CAM fabrication can be recommended so that both appropriate fitness
and retentive force are obtained.
Comments