Cement–cement interface strength: Influence of time to apposition

Abstract

Cement–cement interfaces were created under simulated operating‐room conditions. In order to analyze the effect of time to apposition on interface strength, two cement surfaces were brought together 1, 2, 4, and 6 min after 1 min of mixing and 45 s of waiting. Cement–cement interface strength was evaluated with the use of a three‐point bending to failure test. Scanning electron microscopy (SEM) images of the failed interface were obtained. The mean interface strength decreased when the cement–cement interface was time delayed. Compared to bulk cement, interface strength in time‐delayed groups decreased 8% after 1‐min delay (p=.037), 18% after 2‐min delay (p=.0004), 20% after 4‐min delay (p=.0005), and 42% after 6‐min delay (p<.0001). No statistically significant differences in interface strength were found between the 2‐ and 4‐min delayed groups (p=.73). SEM images revealed that after 6‐min delay, up to 50% of the cement surface can remain unbonded, explaining the decrease in strength of the cement–cement interface as a function of time to apposition. This laboratory study indicates that time to apposition plays a critical role in cement–cement interface strength. If any cementing technique involves the joining of two cement surfaces, it is recommended that the two cement surfaces be mated together within 5 min and 45 s after the start of mixing (1 min mixing; 45 s waiting; 4 min delay), in order to obtain a strong cement–cement interface bond. Delay beyond this can result in substantial reduction in the strength of the cement–cement interface bond. © 2001 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 58: 741–746, 2001