Strength of a dense alumina ceramic after aging in vitro.

Rods of dense alumina ceramic were aged in Ringer's solution for time periods up to 12 weeks, with half of the rods being aged while mechanically stressed. Pyrex-type glass rods were similarly tested for comparison purposes. No reduction in flexural strength was observed in dense alumina rods after aging, providing no permeation of the solution into the ceramic occurred. However, a marked reduction in flexural strength was experienced by alumina rods, nominally dense and nonporous, into which some permeation of the saline solution was observed after aging; the largest reduction in strength occurred in such rods aged while mechanically stressed. The results indicate the importance and advantage of using densely sintered alumina ceramics as implants for optimum structural performance over an extended time period.