[The mechanic retention of the casting post with keeper in magnetic retentor overdenture].

Purpose: To reduce the cost of the fabrication of the magnetic retentor,and meet the clinical requirements, nonprecious alloy such as Co-Cr alloy was used to fabricate the magnetic retentor in overdenture , instead of the precious alloy.

Methods: A mandibular canine was chosen for root canal preparation in vitro. Thirty two resin posts were made in the same root canal with self-curing resin. The 32 resin posts were randomly divided into 4 groups. Among them,2 groups were fabricated with soft Co-Cr alloy, gold alloy(55.6%Au) respectively in vitro. Another 2 groups were fabricated with Co-Cr alloy, and the surface of the root casting post with keeper were treated with gold deposit and gold coating technique. After that, test of dislodgment force was done and one-way ANOVA was performed with SAS 6.2 software package.

Results: The dislodgment force of the root casting posts with keeper which were fabricated with the Co-Cr, Ni-Cr, and gold alloy had significant difference(P<0.01). While after surface treatment by gold deposit and gold coating technique on root casting posts with keeper that were fabricated with Co-Cr and Ni-Cr alloy, there was no significant difference in dislodgment force, compared with that of gold alloy.

Conclusions: After surface treatment of the root casting posts with keeper which were fabricated with the Co-Cr and Ni-Cr alloy, the same clinical retentive effect can be obtained as the one that was fabricated with gold alloy.