Enamel sample preparation for AFM: Influence on roughness and morphology

Abstract

Human dental enamel is organized by prisms that are structured between 3 and 6 µm in diameter. Determining the relationships between different treatments on the surface of enamel using ultrastructural analysis is the purpose of many in vitro experiments. Different sample pretreatments have been reported in the literature. Grinding and polishing are common procedures for enamel preparation. They provide a flat and standardized surface, which is imperative for the use of some techniques such as ATR‐FTIR. However, for morphological analysis, SEM and AFM represent easier methods to measure and reduce the biological sample variation. Therefore, the objective of this study was to establish how different forms of enamel preparation can influence the advent of artifacts during ultrastructural observation, especially by AFM analysis. Four groups (n = 10) were tested: (a) without preparation; (b) polishing with a diamond paste; (c) grinding with decreasing granulations of silicon carbide papers; (d) grinding with polishing. Images were obtained using the Peak‐Force Tapping mode. After the first images were obtained, all fragments were acid etched with 37% phosphoric acid for 30 seconds, rinsed for 60 seconds, and dried intensively. Upon grinding and polishing, the exposure of the inner enamel surfaces provided a less mineralized layer that was marked by scratches and a higher susceptibility to treatments. Moreover, using native enamel provided more valuable information on the surface and the roughness changes for clinical applications. In addition, phosphoric acid is an option for observing the prismatic arrangement after grinding and/or polishing changes the morphology. Research Highlights The use of native enamel samples to investigate the effects of different treatments on surface should be preferred in research, when the technique allows it.

The Effects of Three Remineralizing Agents on the Microhardness and Chemical Composition of Demineralized Enamel

“…In order to create an artificial demineralized lesion, 37% phosphoric acid was used, as suggested by Sorozini [29]. Within the limitations of this study, this was considered sufficient, as it has been shown that absolute simulation of oral conditions is almost impossible due to other variables, including the speed of saliva flow and its buffering ability, dynamic pH cycles in the mouth, and behavioral changes [28,30,31].…”

Metallization and Ar‐O plasma effects on dental enamel roughness evaluated with SEM and MeX™ for 3D reconstruction

“…This study was first designed with the purpose of evaluating dental enamel specimens' roughness submitted to surface treatments without flattening (Sorozini et al, ), in different moments (repeated measures), without the necessity of metallization. Although the most appropriate methods have been discussed (Fischer et al, ; Talu et al, ), there was still a gap in this topic.…”

“…Dental enamel roughness analysis by AFM and contact profilometry are quantitative methods that demand flat specimen surfaces to avoid reading errors on the peaks and valleys (axis Z) or noises, depending on the topographic characteristics. However, a flattened specimen may lead to biased results as the subsurface enamel layer is less mineralized and more susceptible to the effects of treatments (Sorozini, Perez, & Rocha, ) while the whole dental surface properly simulates the clinical reality, increasing the validity and scientific value (Mullan, Mylonas, Parkinson, Bartlett, & Austin, ). Furthermore, the location of the area of interest for the repeated measures depends on the operator care due to the lack of precise tools for delimitation.…”

The role of spatial frequency analysis in correlating atomic force microscopy and optical profilometry with self‐etch adhesive enamel bond fatigue durability

“…A frequently overlooked factor in the interpretation of enamel morphology and bond strength is the enamel surface preparation method. Surfaces are normally standardized through silicon carbide grinding and polishing to minimize differences in collected enamel specimens, standardize smear layers, and accommodate the reality that many bond fatigue testing experimental setups require flat surfaces (Sorozini, dos Reis Perez, & Rocha, ; Tsujimoto, Barkmeier, et al, ). However, this process can fragment and then compact hydroxyapatite crystals on the surface of enamel and affect surface topography and its associated measures (Sai et al, ).…”