The purpose of this study was to investigate the physical properties of experimental
composite resins made with the spherical and crushed fillers. The 14 experimental
composite resins containing 0, 5, 10, 15, 20 and 25%(w/w) in spherical filler group and
0. 10, 20, 30, 40, 50, 60 and 70%(w/w) in crushed filler group, incorporated in a
Bis-GMA matrix (Aldrich Co., USA), were made with 1% γ-methoxy silane treated
fillers. The polymer matrix was made by dissolving 0.7%(w/w) of benzoyl
peroxide(Janssen Chemical Co. Japan) in methacrylate monomer, whereupon 0.7%(v/v)
N,N-dimethyl-p-toluidine(Tokyo Kasei Co. Japan) was added to the monomer. The
weight percentage of each specific particle size distribution could be determined from a
knowledge of the specific gravity, the weight(w/w), and corresponding volume %(v/v) of
the filler sample in resin monomer. In crushed silica group and spherical silica group,
the diametral tensile strengths and compressive strengths were measured with Instron
Testing Machine(No.4467), and analyzed in 14 experimental composite resins made by
filler fractions.
The shear bond strength of 14 experimental composite resins to bovine enamel was
measured with universal testing machine(Instron No.4467).
The fracture surfaces were sputter-coated with a gold film and investigated by SEM.
The results were as follows ; 1. The diametral tensile strength was tendency to
increase in crushed silica group, but not in spherical silica group. The highest diametral
tensile strength was found in 20% filler fractions of two groups.
2. The compressive strength was higher in 15%(w/w) and 20%(w/w) in spherical silica
group than in crushed silica group, but not in spherical silica group.
3. The significant correlation was noticed in increase in shear bond strength in crushed
silica group, but not in spherical silica group.
4. The significantly highest shear bond strength was noticed in 50% filler concentration
in crushed silica group, and in 15% filler concentration in spherical silica group, it was
not significant in relation.
5. In crushed silica group, cut surface of resin matrix and the interface between resin
and filler is obvious. In spherical silica group, fractures that occurred through the filler
particles were round in shape.
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