Indentation-derived mechanical properties and structure-property relationships in dental crowns: an updated review

Oral diseases, most notably tooth decay, represent a significant challenge to public health. They can result in the deterioration of tooth structures and properties that require dental restoration. The objective of conservative dentistry is to remove and replace only the damaged parts. The faithful replication of a natural tooth may prevent additional damage to surrounding tissues and ensure successful restoration. The objective of this review was to establish a connection between the structural organization of teeth at various scales and the resulting properties, with a particular emphasis on insights derived from indentation-based measurements. Recent research findings, especially those concerning the dentin-enamel junction, are also incorporated to provide an updated perspective. The tooth is primarily composed of enamel and dentin, which are two anisotropic tissues exhibiting a decrease in Young's modulus and hardness from the exterior to the center. The mechanical properties of enamel are four to five times higher than those of dentin. Enamel, which is stiffer and more brittle, is more susceptible to cracking. Its structure and composition limit the propagation of cracks to the dentin. Dentin is a viscoelastic material that absorbs stress. Its capacity to dissipate energy decreases with age, whereas its ability to store energy increases. The dentin-enamel junction bridges these two distinct tissues, leveraging both a scalloped architecture and functionally graded properties to optimize interfacial cohesion and mitigate crack propagation.