An investigation of the effects of endodontic treatment and moisture content on some mechanical properties of human dentin
Huang, Tzyy-Jou G
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There is a general belief that treated pulpless teeth become brittle in time and subject more to fracture than vital teeth. Many authors support the theory that the loss of strategic tooth structure and dehydration are the main causes of this phenomenon. However, no substantial report in the literature confirms this. This study was designed to determine the effects of endodontic treatment and moisture content on the mechanical properties of human dentin. Since dentin is the main supporting component in the structure of teeth, the ability of teeth to function is ultimately determined by the strength of their dentin. In this study, 54 freshly extracted normal vital human teeth and 24 treated human pulpless teeth were made into 317 dentin specimens. These specimens were subjected to different conditions (kept wet, air-dried, desiccated, and rehydrated, etc.). Compression tests, diametral-compression (indirect tensile) tests, and impact tests were conducted to measure the mechanical properties of those specimens. The results showed that the dehydration of dentin increases the Young′s modulus (modulus of elasticity in compression), proportional limit (in compression), and especially the ultimate strength (in both compression and tension). The compressive strength of air-dried dentin is higher, ranging from 33% (crown) to 49% (root), than that of normal wet dentin. While the compressive strength of desiccated dentin is still higher, ranging from 63% (crown) to 75% (root), than that of wet dentin. Similarly, the indirect tensile strength of air-dried dentin is 42% (root) higher, and desiccated dentin can be up to 95% (root) higher. Substantial dehydration changes the fracture characteristics of dentin specimens under static compressive and indirect tensile loadings. The measurements of impact-breaking energies of desiccated dentin were not found to be decreased. The compressive and tensile strengths of dentin from treated pulpless teeth obtained in this study do not appear to be less than those of normal dentin, while the average values of Young′s modulus and proportional limit in compression tests appear to be lower than those of normal dentin. Fifty percent of the dentin specimens of treated pulpless teeth exhibit greater plastic deformation than normal dentin in compression. The percentage of deformation can be up to 25%. This phenomenon does not seem to be related to the age, tooth type, nor to the time periods subsequent to endodontic treatment. The results of this study do not appear to support the theory that dehydration after endodontic treatment per se weakens dentin structure in terms of compressive and tensile strengths. Other mechanical properties of treated pulpless teeth, however, may not be the same as those of normal vital teeth. Additional investigation using more sophisticated mechanical tests and specimens may be proposed to determine other mechanical properties that may apply to clinical problems attributed to treated pulpless teeth.
PLEASE NOTE: This work is protected by copyright. Downloading is restricted to the BU community: please click Download and log in with a valid BU account to access. If you are the author of this work and would like to make it publicly available, please contact firstname.lastname@example.org.Includes colored photographs.Thesis (M.Sc.D.)--Boston University, Henry M. Goldman School of Graduate Dentistry, 1989 (Endodontics)Bibliography : leaves 161-180a.
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