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Comparison of mechanical properties of various post and core materials
Seung-Geun Ahn, and John A. Sorensen

Statement of problem :Many kinds of post and core systems are in the market, but there are no clear
selection criteria for them.
Purpose : The purpose of this study was to compare the flexural strength and modulus of elastic-
ity of core materials, and measure the bending strength of post systems made of a variety of
materials.
Material and Methods : The flexural strength and elastic modulus of thirteen kinds core buildup
materials were measured on beams of specimens of 2.0×2.0×24±0.1mm. Ten specimens per group
were fabricated and loaded on an Instron testing machine at a crosshead speed of 0.25mm/min. A
test span of 20 mm was used. The failure loads were recorded and flexural strength calculated with
the measured dimensions. The elastic modulus was calculated from the slopes of the linear portions
of the stress-strain graphs. Also nine kinds commercially available prefabricated posts made of var-
ious materials with similar nominal diameters, approximately 1.25mm, were loaded in a three-point
bend test until plastic deformation or failure occurred. Ten posts per group were tested and the obtained
data were anaylzed with analysis of variance and compared with the Tukey multiple comparison
tests.
Results :Clearfil Photo Core and Luxacore had flexural strengths approaching amalgam, but its mod-
ulus of  elasticity was only about 15% of that of amalgam. The strengths of the glass ionomer and
resin modified glass ionomer were very low. The heat pressed glass ceramic core had a high elas-
tic modulus but a relatively low flexural strength approximating that of the lower strength composite
resin core materials. The stainless steel, zirconia and carbon fiber post exhibited high bending strengths.
The glass fiber posts displayed  strengths that were approximately half of the higher strength posts.
Conclusion :When moderate amounts of coronal tooth structure are to be replaced by a post and
core on an anterior tooth, a prefabricated post and high strength, high elastic modulus core may be
suitable.
CLINICAL IMPLICATIONS
In this study several newly introduced post and core systems demonstrated satisfactory
physical properties. However when the higher stress situation exists with only a minimal fer-
rule extension remaining a cast post and core or zirconia post and pressed core are desirable.

* Keywords: Post and core material, Flexural strength, Bending strength

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