The antibacterial activity of potential retrograde root filling materi
als was assessed using the agar diffusion inhibitory test. A light-cur
ed glass ionomer cement (Vitrebond and three reinforced zinc oxide-eug
enol cements (Kalzinol, IRM & ethoxybenzoic acid [EBA] cement) were co
mpared with amalgam, a commonly used retrograde root filling material.
Forty standardized pellets of each material were produced. Fresh, and
materials aged for 1 week in sterile distilled water, were placed on
blood agar plates inoculated with Streptococcus anginosus (milleri) or
Enterococcus faecalis. At intervals of 3, 7 and 10 days, the presence
and diameter of zones of inhibition were recorded. The diameter of th
e zones of inhibition increased with time for all materials, both fres
h and aged. Vitrebond had the most pronounced antibacterial activity a
gainst both bacteria, producing the largest zone of inhibition, follow
ed by Kalzinol. Amalgam had no measurable inhibitory effect whether ag
ed or fresh, regardless of the period of exposure. There was no statis
tically significant difference in the response of the two bacteria. Ho
wever, there were statistically significant differences between materi
als, period of exposure, and between fresh and aged materials (P<0.001
). Kalzinol, IRM and EBA cement were more antibacterial when aged than
fresh, whilst Vitrebond was more active when fresh. Vitrebond was the
only material for which the diameter of the zones of inhibition was r
educed after ageing but it had the most pronounced antibacterial activ
ity compared with the other materials. The antibacterial activity of t
he materials was ranked in the following order: Vitrebond > Kalzinol >
(IRM = EBA cement) > amalgam.