Id. Owadally et Trp. Ford, EFFECT OF ADDITION OF HYDROXYAPATITE ON THE PHYSICAL-PROPERTIES OF IRM, International endodontic journal, 27(5), 1994, pp. 227-232
The aim of this study was to evaluate the effect of adding 10% and 20%
hydroxyapatite (HAP) to Intermediate Restorative Material (IRM) on ph
ysical properties such as working time, setting time, compressive stre
ngth and disintegration rate. The working and setting times were deter
mined by an indentation method. The ISO recommended method was used to
determine compressive strength. The rate of disintegration in vitro w
as evaluated in buffered sodium citrate at pH 4.5, 5.8, buffered phosp
hate at pH 7.0 and in bovine serum (pH 6.8), and examined using a repl
ica method and scanning electron microscopy. Kalzinol and EBA were use
d as control materials for the disintegration experiment. IRM had long
er mean working (4 min 43.5 s) and mean setting (6 min 28.5 s) times t
han IRM + 10 or 20% HAP (P<0.001), the mean reductions being 16% and 9
% for IRM + 10% HAP, and 29% and 19% for IRM + 20% HAP, respectively.
IRM had a greater compressive strength (68.5 MPa, P<0.01) than IRM + 1
0% HAP (65.0 MPa) or IRM + 20% HAP (60.0 MPa, P<0.001). Kalzinol, IRM
+ 10% HAP and IRM + 20% HAP were found to disintegrate after 8 weeks i
n buffered phosphate and in bovine serum. In contrast, IRM and EBA sho
wed no noticeable signs of disintegration after 6 months in the same m
edia. The physical properties of IRM + 10% HAP and IRM + 20% HAP were
reduced compared with IRM but the reductions were not considered to be
of clinical significance.