Abstract
On the basis of a clinical investigation completed in 1982, we pointed out the necessity for the improvement of some aspects of K-G posterior restorative composite resin. In the present study, in order to obtain a resin with better operability and physical properties, several posterior restorative composite resins of various consistencies were prepared on an experimental basis, and their physical properties were examined. The experiment included observation of inorganic fillers by means of scanning electron microscopy and determination of consistency, filler content, surface hardness, compressive strength, tensile strength, and bending strength.
The results were as follows:
1) The consistency softened in proportion to the decrease in the inorganic filler content.
2) With a decrease in the filler content, the knoop hardness decreased on a nonpolished surface, but remained unchanged on a polished one.
3) There was no difference in the compressive strength in relation to the filler content.
4) The tensile strength and the bending strength increased with a decrease in the filler content.
The above finding show that softening of the consistency by reducing the filler content causes no particular changes in the hardness of the polished surface or in the compressive strength, achieving favorable tensile strength and bending strength and resulting in improved operability. This seems to lead to a decrease in the incidence of body fracture in the restoration of the proximo-occulusal cavity of the deciduous posterior teeth.
