Influence of the number of insertions and removals of telescopic zirconia/alumina crowns on retentive force and settling.

Abstract

Telescopic crowns made from zirconia/alumina can be manufactured using computer-aided design/computer-aided manufacturing systems. For their successful clinical use, a suitable retentive force must be maintained over an extended period. However, it is unclear how retentive force and secondary crown settling change after repeated crown insertion and removal. The aim of the present study was to investigate the changes in retentive force and secondary crown settling of telescopic crowns made from zirconia/alumina. Primary crowns with tapers of 2° and 4° were used. Repeated insertion and removal tests were performed for 10,000 cycles at a cyclic load of 50 N. The loads applied when measuring retentive force and settling were 50 and 100 N. The number of insertions and removals had a significant effect on retentive force and settling at both loads (p<0.01). Taper also had a significant effect on retentive force and settling at both loads (p<0.01).