Nanomechanical Properties of Hydrated Carious Human Dentin

Abstract

Most restorative materials are bonded to caries-affected dentin that has altered structure. We tested the hypothesis that hydrated dentin of the transparent zone did not have increased hardness or elastic modulus. Nanoindentation by modified AFM was used to determine site-specific elastic modulus and hardness for components of hydrated dentin from 8 carious and non-carious human teeth. Indentations in intertubular dentin were made at intervals from pulp through the affected layers (subtransparent, transparent, and discolored zones). The values of intertubular dentin increased slightly from near the pulp into the transparent zone, then remained constant or decreased slightly through transparent dentin (E, 18.3 GPa; H, 0.8 GPa; confirming the hypothesis), and decreased markedly through the discolored region. Peritubular dentin values were unaltered in transparent dentin, and intratubular mineral had values between those of normal peritubular and intertubular dentin. Superficial areas contained distorted tubules without peritubular dentin or intratubular mineral.

Hardness and Young's Modulus of Transparent Dentin Associated with Aging and Carious Disease

“…Recently, nanoindentation measurements have been made on enamel, the EDJ, dentin, and the resindentin interface8- 10,14,18) This computer-controlled, depth-sensing instrument detects the indentation depth during loading and unloading in situ.…”

“…The hardness of peritubular dentin is much higher than that of intertubular dentin13, 14,17). In a pilot study using a load of 200 mgf, indentations made on a line from the dentinoenamel junction to the pulpal site produced large variations in hardness value, even when measuring young normal dentin.…”

Ions-modified nanoparticles affect functional remineralization and energy dissipation through the resin-dentin interface

“…Even more, the nano-DMA analysis shows that the dampening (or viscous) behavior of the tissue is much more sensitive to the structural changes that occur with the oral function and than the quasi-static behavior (Ryou et al, 2015). Thereby, it requires the capacity to absorb mechanical shock waves and alleviate stresses at these locations in order to prevent crack propagation across the boundary between the two phases of dentin and thus, may serve as useful biomimetic models for joining mechanically dissimilar biomaterials to restore form and function (Marshall et al, 2001). …”

SEM evaluation of resin-carious dentin interfaces formed by two dentin adhesive systems

“…According to previous studies, the inner affected layer of carious dentin which is un-infected and remineralizable can be softer than normal dentin [1,2] or have similar properties to normal dentin. [3] These findings suggest that traditional tactile based characteristics of carious dentin often sacrifice more structure than necessary. Additionally, it is possible that clinicians are bonding to a substrate that is composed of sound, caries-affected and caries-infected dentin in the same cavity, which is likely to result from subjectivity inherent among dentists and the variation in the quality and quantity of dentin removed during treatment [4].…”

“…Using caries detector may be helpful to differentiate the layers of carious coronal dentin, by staining the outer layer pink [5]. Although it has been criticized as being insufficiently discriminating [6], it is clear, based on degree of staining, that the carious dentin lesion can be classified into pink, light pink, transparent, and apparently normal zones [3]. These four zones have distinct mechanical properties, which may guide clinical decisions to excavate or remineralize carious dentin.…”