The importance of microstructural variations on the fracture toughness of human dentin

Abstract

The crack growth resistance of human dentin was characterized as a function of relative distance from the DEJ and the corresponding microstructure. Compact tension specimens were prepared from the coronal dentin of caries-free 3rd molars. The specimens were sectioned from either the outer, middle or inner dentin. Stable crack extension was achieved under Mode I quasi-static loading, with the crack oriented in-plane with the tubules, and the crack growth resistance was characterized in terms of the initiation (Ko), growth (Kg) and plateau (Kp) toughness. A hybrid approach was also used to quantify the contribution of dominant mechanisms to the overall toughness. Results showed that human dentin exhibits increasing crack growth resistance with crack extension in all regions, and that the fracture toughness of inner dentin (2.2±0.5 MPa•m0.5) was significantly lower than that of middle (2.7±0.2 MPa•m0.5) and outer regions (3.4±0.3 MPa•m0.5). Extrinsic toughening, composed mostly of crack bridging, was estimated to cause an average increase in the fracture energy of 26% in all three regions. Based on these findings, dental restorations extended into deep dentin are much more likely to cause tooth fracture due to the greater potential for introduction of flaws and decrease in fracture toughness with depth.

On the Mechanics of Fatigue and Fracture in Teeth

“…For cracks in-plane with the tubules, the average initiation 2.2 MPaÁm 0.5 , growth 1.2 MPaÁm 0.5 /mm) and plateau toughness 2.7 MPaÁm 0.5 are greater than those values for the transverse direction (Fig. 8(c)) [66]. The mechanisms contributing to the toughening behavior in this orientation are similar, except perhaps for a larger contribution of the mineralized collagen caused by its orientation.…”

“…Nevertheless, constraints in tissue volume have limited this configuration to studies of dentin from the tooth crown e.g., Refs. [64][65][66]. A schematic description of the more common specimen configurations that have been adopted is presented in Fig.…”

Use of Morphometric Analyses to Assess the Efficacy of the Technique of Resin Composite Bonded to Cervical Dentin with Additional Mechanical Retentions

“…In both cases the resulting differences may be due to the presence of retentions in the EG, which on the one hand implies an increase in the contact surface between the interface components, and on the other the inclusion of resin inside them generates a change of material that brings about a redistribution of forces when the bond is loaded. This way, when the fault in the resin composite-dentin bond is induced with the application of the shear test, the additional contact surface provided by the retentions involves more dentin, causing a cohesive fracture of this substrate, a phenomenon facilitated by the depth of the preparations in the dentin (Ivancik & Arola, 2013). At the same time, these retentions tend to prevent the resin from being dislodged, which causes a cohesive fracture.…”

“…Certainly both types of analysis provide relevant objective information as to the mechanical behavior of the adhesive and the substrates (Scherrer et al) involved in the resin-dentin bond of the surface fractured after application of the mechanical test. Nevertheless, their correlation with the clinical behavior of restorations must be established individually for such parameters as microfiltration, bond strength and marginal fit (Heintze), and by association to those studies that evaluate the behavior of the resin-dentin bond interface in terms of resistance to shear forces and traction (Braga et al, 2010;Ivancik & Arola).…”

Restaurations coronoradiculaires des dents dépulpées par endocouronnes

“…Sa rigidité, inférieure à celle de l'émail, est de 19 GPa. Les deux substrats de modules différents sont en contact grâce à des fibres de collagène, permettant un transfert de contraintes à cette interface, constituant ainsi un mécanisme efficace contre la propagation des fissures et l'absorption des contraintes (12) : c'est la jonction amélo-dentinaire (JAD). Cette interface structurelle et fonctionnelle entre un tissu extrêmement rigide et un tissu flexible donne à l'organe dentaire cette aptitude à supporter les contraintes masticatoires et thermiques tout au long de la vie (13), créant ainsi un excellent compromis entre rigidité, solidité et résilience.…”