Effects of polar solvents on the fracture resistance of dentin: role of water hydration

Abstract

Although healthy dentin is invariably hydrated in vivo, from a perspective of examining the mechanisms of fracture in dentin, it is interesting to consider the role of water hydration. Furthermore, it is feasible that exposure to certain polar solvents, e.g., those found in clinical adhesives, can induce dehydration. In the present study, in vitro deformation and fracture experiments, the latter involving a resistance-curve (R-curve) approach (i.e., toughness evolution with crack extension), were conducted in order to assess changes in the constitutive and fracture behavior induced by three common solvents-acetone, ethanol and methanol. In addition, nanoindentation-based experiments were performed to evaluate the deformation behavior at the level of individual collagen fibers and ultraviolet Raman spectroscopy to evaluate changes in bonding. The results indicate a reversible effect of chemical dehydration, with increased fracture resistance, strength, and stiffness associated with lower hydrogen bonding ability of the solvent. These results are analyzed both in terms of intrinsic and extrinsic toughening phenomena to further understand the micromechanisms of fracture in dentin and the specific role of water hydration.

Measurements of mobile and bound water by nuclear magnetic resonance correlate with mechanical properties of bone

“…This amide I chemical species is a product of the organic phase of bone, and its band is influenced by collagen crosslinking [43]. Interestingly, dehydration of dentin (elephant tusk) by polar solvents, which reduce hydrogen bonding between water and collagen, was also found to increase the amide I band [44].…”

Nanoindentation in teeth: influence of experimental conditions on local mechanical properties

“…It is well known that the fluid for storing dental tissues can alter their mechanical properties [5,10]. Alcohol, e.g.…”

“…Alcohol, e.g. produces shrinkage of the tissue because it increases the levels of interpeptide hydrogen bonding [10]. This leads to enhanced hardness and mechanical stiffness, compared with the case of storage in HBSS.…”

“…This leads to enhanced hardness and mechanical stiffness, compared with the case of storage in HBSS. HBSS, on the other hand, has a major percentage of water, with the necessary ions to prevent dentin demineralization [5,10] and water plasticizes collagen by breaking interpeptide bonds [5], which is translated into lowered hardness and stiffness of the hydrated samples. As the results show, the difference is remarkable: E and H decrease to about half and one third of their values, respectively, on going from dry (alcohol) to wet (HBSS) conditions.…”

“…Local mechanical properties of the intertubular dentin (between the tubules) investigated here depend on mineral content and level of interpeptide hydrogen bonding. Most storage solutions are known to alter both characteristics [5,10].…”