Tensile Strength of Mineralized/Demineralized Human Normal and Carious Dentin

Abstract

The bond strengths of resins to caries-affected dentin are low. This could be due to weakened organic matrix. The purpose of this work was to determine if the ultimate tensile strength (UTS) of excavated carious dentin is weaker than that of normal dentin. Soft caries was excavated from extracted human molars, and the tooth was vertically sectioned into slabs. Each slab was trimmed to an hourglass shape, parallel or perpendicular to the tubule direction. Half of the specimens were mineralized, while the other half were completely demineralized in EDTA. ANOVA on ranks showed that the three-factor interactions (mineralization, caries, tubule direction) were all significant (p < 0.0001), indicating that mineralization and tubule direction gave different UTS results in normal and caries-affected dentin. No significant differences were seen between the UTS of normal and and that of caries-affected demineralized dentin in the parallel or perpendicular group. The matrix of demineralized caries-affected dentin was as strong as that of normal demineralized dentin when tested in the same direction.

Scanning acoustic microscopy investigation of frequency-dependent reflectance of acid- etched human dentin using homotopic measurements

“…It is therefore not surprising to find un-infiltrated, exposed collagen below the hybrid layer in composite restorations. The exposed collagen becomes a weak link in the adhesive bonding of composite restorations [47]. …”

Bonding to caries-affected dentin

“…In addition, ultimate tensile strength (UTS) of caries-affected dentin is also lower than that of normal dentin, and there is a positive correlation in caries-affected dentin between the UTS and the Knoop hardness number [6]. On the other hand, Nishitani et al [32] reported that the matrix of demineralized cariesaffected dentin was as strong as that of normal demineralized dentin. These results would indicate that lower UTS and hardness of caries-affected dentin are due to loss of mineral in intertubular dentin.…”

Structural analysis of reactionary dentin formed in response to polymicrobial invasion

“…While all dentin matrices display a similar structural plan, there are distinct functional attributes for each type (Zaytsev et al, 2012). Considering the loss of tooth structure in extensive caries and the compromised APd resulting from the carious process (Nishitani et al, 2005), there is a requirement for Rd to provide an appropriate deformable and resilient foundation to resist tooth fracture under high stress. This modification manifests as a lower elastic modulus reported for Rd compared to APd (Senawongse et al, 2006).…”