The Influence of Contamination and Different Cleaning Methods and the Effect of Plasma Treatment of CoCr Alloy on Tensile Bond Strength to Composite Resin.

Purpose: To investigate the influence of contamination and different cleaning methods on resin bonding to cobalt-chro- mium (CoCr) alloy disks.
Materials and Methods: A total of 160 CoCr disks were divided into 3 groups. The first group (N = 64) was air abraded with alumina particles and contaminated with a silicone disclosing agent and saliva; the second group (N = 64) was air abraded but not contaminated; the third group (N = 32) was neither air abraded nor contaminated. The first two groups were di- vided into 4 subgroups (N = 16) according to the cleaning method: ultrasonic bath in 99% isopropanol, use of a cleaning suspension of zirconium oxide particles, use of a cleaning suspension based on 10-MDP salt, and treatment with atmo- spheric plasma. The third group was divided into 2 subgroups (N = 16): treatment with atmospheric plasma and no treat- ment. All CoCr specimens were bonded to plexiglas tubes filled with a bonding resin that contained phosphate monomer. Tensile bond strength (TBS) was examined by tensile testing after 3 and 150 days of water storage plus 37,500 thermal cy- cles (N = 8).
Results: After contamination, TBS was significantly reduced after 150 days of water storage. Groups without air abrasion showed initially low TBS and debonded spontaneously after 150 days of water storage.
Conclusion: None of the cleaning methods was able to remove saliva and silicone disclosing agent on CoCr-alloy sur- faces. Surface activation by plasma treatment has no long-term effect on the bond strength.