The influence of alloy copper content on the polymerisation of anaerobic adhesives

Abstract

Objectives: Anaerobic adhesives are capable of bonding copper-containing metal attachments to etched human enamel, where the latter surface has been rendered reactive by the use of a copper-containing surface activator. The aims of the present study were to determine whether copper attachments could also be successfully bonded to etched human enamel, using anaerobic adhesives, where no such surface activator was used. In addition, the effect of alteration in the copper content of the attachment alloy was also investigated. Methods: Metal attachments suitable for use with anaerobic adhesives were made from one of three copper-containing alloys. Their copper contents were 8%, 19% and 99.9%. They were bonded to human enamel, which had been ground flat and etched with 37% o-phosphoric acid, using one of three anaerobic adhesives. After bench curing for one of four time periods, 10 min, 1 h, 24 h and 2 weeks, shear testing to failure was performed. The load at debond was recorded in each case. Results: The results were analysed using mean force to debond (N) and 95% confidence intervals. Kaplan–Meier survival probabilities and log-rank tests were performed for the 10 min and 1 h test times. Conclusions: Each of the three anaerobic adhesives under test demonstrated a concentration effect for the copper in the metal attachments. The higher the copper content of the attachment the greater the measured force to debond and the more rapid its attainment. As determined by measured force to debond, only one adhesive, Loctite 326, underwent any significant degree of activation and, therefore, polymerisation by the lowest copper content alloy under test.