ISSN:
1045-4861
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Medicine
,
Technology
Notes:
Fatigue crack propagation in a notched specimen under cyclic loading was investigated for a series of experimental composite resins and six commercial composites. The fatigue resistance was measured as a function of filler content, water absorption, and post-curing temperature. Constants A and m of the Paris law have been obtained by linear regression analysis. The plot of fatigue resistance against volumetric filler content, V shows a sigmoidal relationship wiht a rapid increase in the range of V = 40-50% then tapering off at higher V. A substantial increase in the constant m of the Paris law was found for water-saturated commercial composite resins. Although increasing the post-curing temperature from 37°C to 70°C results in a 10% increase in fracture resistance, a high post-curing temperature is not favorable for highly filled composites (V 〉 60%) where more strained areas can be induced unless polymerization shrinkage is minimal. The ranking of fracture resistance for the commercial materials is: Occlusin 〉 P30 ≃ Adaptic II ≃ Ful-Fil 〉 Isomolar 〉 LC33. Based on the assumption that microcrack growth in the subsurface damage layer is the precursor of wear, fatigue resistance combined with fracture toughness satisfactorily predicted the clinical wear of commercial composites. Surface microfracture which amplifies the subsurface flaw size and creates undesirable stress concentrators can be subdued by high fracture toughness. In addition, high fatigue resistance retards the formation of wear particles, thereby reducing loss of material from the composite surface.
Additional Material:
12 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jab.770010105
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