Ultrastructural characterisation of young and aged dental enamel by atomic force microscopy

Abstract

Recent advances in atomic force microscopy (AFM) have allowed the characterisation of dental-associated biomaterials and biological surfaces with high resolution. In this context, the topography of dental enamel -the hardest mineralised tissue in the body -has been explored with AFM-based approaches at the microscale. With age, teeth are known to suffer changes that can impact their structural stability and function; however, changes in enamel structure because of ageing have not yet been explored with nanoscale resolution. Therefore, the aim of this exploratory work was to optimise an approach to characterise the ultrastructure of dental enamel and determine potential differences in topography, hydroxyapatite (HA) crystal size, and surface roughness at the nanoscale associated to ageing. For this, a total of six teeth were collected from human donors from which enamel specimens were prepared. By employing intermittent contact (AC mode) imaging, HA crystals were characterised in both transversal and longitudinal orientation (respect to surface plane) with high resolution in environmental conditions. The external enamel surface displayed the presence of a pellicle-like coating on its surface that was not observable on cleaned specimens. Acid-etching exposed crystals that were imaged and morphologically characterised in high resolution at the nanoscale in both the external and internal regions of enamel in older and younger specimens. Our results demonstrated important individual variations in HA crystal width and roughness parameters across the analysed specimens; however, an increase in surface roughness and decrease in HA width was observed for the pooled older external enamel group compared to younger specimens. Overall, high-resolution AFM was an effective approach for the qualitative and quantitative characterisation of human dental enamel ultrastructure. Future work should focus on exploring the ageing of dental enamel with increased sample sizes to compensate for individual differences as well as other potential confounding factors such as behavioural habits and mechanical forces.

Synchrotron X-ray Studies of the Structural and Functional Hierarchies in Mineralised Human Dental Enamel: A State-of-the-Art Review

“…All of the aforementioned developments described in this review led to new advances in research on enamel and other mineralised tissues; however, there is a necessity to correlate the findings of synchrotron-based experiments with other techniques such as polarised transmitted light microscopy [ 145 ], FIB-SEM [ 39 ], (S)TEM [ 190 ], radiography/tomography [ 145 ], optical coherence tomography (OCT) [ 696 ], polarization sensitive OCT [ 697 ], APT [ 698 ], Raman spectroscopy [ 168 ], X-ray photoelectron spectroscopy [ 699 ], AFM [ 700 ], mechanical tests [ 701 ], proton induced X-ray emission (PIXE) [ 702 ], neutron [ 703 ], time-of-flight secondary ion mass spectroscopy (ToF-SIMS) [ 704 ], and indentation [ 142 ], to develop a suitable sample preparation workflow and to tackle the disease with a multi-scale multi-correlative characterisation technique strategy.…”

Dynamics of Dental Enamel Surface Remineralization under the Action of Toothpastes with Substituted Hydroxyapatite and Birch Extract

“…Prolonged and regular usage over the course of decades may induce a reduction in apatite crystal length, leading to HAP crystals fracturing into smaller entities [5,6].…”

A Lens on the Future: Next Generation Microscopy by Next Generation Microscopists

“…Shifting into the disciplines of Scanning Probe and Atomic Force Microscopies, Leiva-Sabadini et al 2 then provide fascinating insights to the effect of ageing on the ultrastructure of our teeth. The Authors provide a high-resolution overview of the human dental enamel surface using non-destructive methods and minimal specimen processing (2). They characterise the enamel surface roughness and mineralisation and then discuss the impact of ageing on dental health and tooth ultrastructure.…”