The fracture surfaces of ceramic prostheses can be characterized using fractal geometry to provide a wealth of information about the material properties and the conditions that were present at the time of failure. This potentially useful too is not widely employed because the current methods of fractal analysis are labor intensive, technique sensitive, and statistically biased. Our team has developed a new failure analysis method. It is an automated, unbiased method of rapidly and precisely measuring the fractal dimensional increment (D*) of fracture surfaces. The proposed project aims to validate this tool as an enabling technology to allow (1) determination of the failure origin in multilayered structures and (2) determination of material fracture toughness, both of which are useful in improving material processing. Furthermore, prior work leads us to hypothesize that both (1) and (2) can be determined from analyzing the D* of any fragment of a broken prosthesis - even when the failure origin has been lost or damaged. In addition, when the critical flaw is visible on the fracture surface, we should be able to estimate the stress at failure, which will be useful in diagnosing parafunction and/or the presence of an atypical residual stress. We will test the accuracy of this technique by comparing our results on two benchmark materials (silica glass and NIST standardized Si3N4) to the values in the literature for the same materials. We will test the utility of this technique by verifying our ability to detect which of three commercially availale dental ceramics is the failure origin in bilayered specimens (glass-ceramic veneered with porcelain, zirconia veneered with porcelain, and zirconia veneered with glass-ceramic). There are three overall goals of the proposed project: (1) Validate our innovative technique for use on monolithic and bilayered flexure beam specimens having a standard geometry with known failure stress levels. (2) Validate our innovative technique for use on all-ceramic fixed partial dentures (both crowns and three-unit FPDs). (3) Determine the effects of test conditions that deviate from the clinical case (monotonic vs. cyclic loading and wet vs. dry environment). The resulting information will have a high potential impact on the field of prosthodontics and may also be applicable to ceramic components used in orthopedic surgery and the automotive, aerospace, and semiconductor industries.
Our team has developed a new test method. This tool will be used on ceramic dental crowns and bridges that break earlier than expected after being put in patients' mouths. The proposed project will determine if the tool can tell scientists why some crowns and bridges break too soon.
