Sorptivity of water in enamel for categorizing caries lesions

On elastoplastic behavior of porous enamel-An indentation and numerical study

The micro/nano pores in natural mineralized tissues can, to a certain extent, affect their responses to mechanical loading but are generally ignored in existing indentation analysis. In this study, we first examined the void volume fraction of sound and caries lesion enamels through micro-computed tomography (micro-CT). A Berkovich indentation study was then carried out to characterize the effect of porous microstructure on the mechanical behavior of the human enamels. The indentation tests were also modeled using the nonlinear finite element analysis technique to simulate indentation load-displacement curves, which showed reasonable agreement with the experimental measurements. From the simulation results, the extent of densification in the plastic zone was identified and the corresponding stress and contact pressure evolutions were quantified. Further, a conventional elastic-perfectly plastic material model without considering micropores was also developed to investigate the compaction effect of the porous structure. The simulation results reveal that conventional elastic perfect-plastic constitutive models become less reliable to model the mechanical behavior of carious lesion enamel with increasing loss of mineral content as it underestimates the yield stress and plastic energy dissipation. This study divulges the importance of compaction of porous enamel structure beneath the indented area. Note that understanding the effect of porous microstructures on plastic behavior is vital as the involved inelastic deformation mechanism associated with irreversible processes, such as wear and localized microcracking, has a significant bearing on wear and fatigue behavior of enamel. STATEMENT OF SIGNIFICANCE: Based on micro-CT and nano-indentation characterization, a numerical model was developed aiming to precisely describe the deformation behavior of naturally porous enamel. Inelastic properties and energy dissipation characteristics of porous enamel were investigated in detail. This work demonstrated that the existence of micro-pores in White Spot Lesions (WSLs) contributes to mechanical stability, which can mitigate the reduction in Young's modulus and fracture toughness resulting from loss of mineral components. The knowledge gained from this study can be used to explain the mechanisms related to irreversible processes, such as contact induced cracking and wear, and strengthen understanding of the mechanical behavior of porous mineralized tissues.

Retention rate of resin sealants in dental enamel with structural alterations: a systematic review

Resin sealants have been used preventively and therapeutically in tooth enamel. The latter can present different conditions in its structure. In this sense, adhesive retention in enamel has ample evidence of its effectiveness, but not in enamel with structural alterations. In this way, it is relevant to know the adhesive retention of these materials and how they behave over time in enamel with variations in its composition. To determine the retention rate of resin sealants in tooth enamel with structural alterations. The study is part of a systematic review following the PRISMA protocol. Articles published between 2010 and 2020 on the retentive behavior of resin sealants in dental with structural alterations were examined. The electronic search was carried out in Web of Science, Scopus, PubMed and Medline. Those articles that used resin sealants in dental enamel with structural alterations were incorporated in clinical trials. Results: Eight articles were found. These were stratified according to the application surface; (i) carious surface, (ii) surface with fluorosis and (iii) surface with hypomineralization of the molar incisor. It was evidenced that the retention rate of resin sealants on decayed enamel is 80% on average, in enamel with dental fluorosis 67.5% and enamel with hypomineralization of the molar incisor 72% 2 years after their application. The retentive behavior of resin sealants on enamel with structural alterations is adequate for the three application surfaces. However, further studies are required regarding dental fluorosis and molar incisor hypomineralization. The most significant evidence on the retention rate was found on various surfaces.