BIOLOGICAL PROPERTIES OF IRM(R) WITH THE ADDITION OF HYDROXYAPATITE AS A RETROGRADE ROOT FILLING MATERIAL

The effect of adding 10% & 20% hydroxyapatite (HAP) on the antibacteri al activity and cytotoxicity of IRM (Intermediate Restorative Material ) when used as a retrograde root filling was compared with amalgam, a commonly used material. The antibacterial activity was assessed using the agar diffusion inhibitory test. Forty standardized pellets of each material were produced. Fresh materials, and materials aged for 1 wee k in sterile distilled water, were placed on blood agar plates inocula ted with Streptococcus anginosus (milleri) or Enterococcus faecalis. T he presence and diameter of zones of inhibition were recorded at inter vals of 3, 7 and 10 days. There was no statistically significant overa ll difference in the response of the two bacteria tested. However, the re were statistically significant overall differences in diameters of the zones of inhibition related to different materials, period of expo sure and ageing of materials (P < 0.001). The diameter of the zones of inhibition increased with time for all materials, fresh and aged. IRM and both the HAP-modified forms produced large zones of inhibition wh ether aged or fresh, regardless of period of exposure and was differen t from the other materials (P < 0.001). The cytotoxicity was assessed using the Millipore filter method. Ten standardized pellets of each ma terial were produced and aged by storage in sterile distilled water fo r 72 h. Ten filters were included as controls. Amalgam produced a cons istent cytotoxic score of 1, and the difference between amalgam and th e other materials was statistically significant (P < 0.001). Therefore , the antibacterial activity and cytotoxicity of the materials could b e ranked in the following order: (IRM = IRM + 10% HAP = IRM + 20% HAP) > amalgam.