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69
brittle than vital dentin when tested by the unconstrained punch shear test
developed by Roydhouse (1970). Using the punch shear test, Carter et al. (1983)
investigated all kinds of differences in shear strength and shear toughness of the
dentin in extracted vital and endodontically treated molar teeth and with a simple
modification of the test the effects of anatomical tooth types. When dentin slices
were constrained during punching so that bending was prevented, the precision of
of the results improved and higher values were recorded.
Photoelastic methods were used to examine stress distribution patterns for
posts of various length, surface configurations, and diameters (Caputo & Hokama,
1984; Cooney, Caputo & Trabert, 1986; Burns et al. 1990). In addition, computer
simulation methods were used to predict the stress distribution in a post restored
tooth. Holmes, Diaz-Arnold & Leary (1996) selected a computer simulation to
predict the distribution of stresses in the dentin of an endodontically treated tooth
restored with cast post and cores of various post dimensions. The distribution of
tensile and compressive stresses were found to be unaffected by variation in the
dimensions of the posts
The finite element method (FEM) was used to compare stress along the
inner canal wall in four two-dimensional models of an average maxillary central
incisor (Cailleteau, Rieger & Akin, 1992). The findings indicated that the stress
patterns within the root were altered as a result of post insertion. Thorn & Joyce
(1999) investigated various endodontic causes and various phases of crown
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