Abstract
The remineralization mechanism in dental caries lesions is not completely understood. This study reports on ultrastructural and chemical changes observed within arrested caries lesions. Carious human teeth were observed using scanning electron microscopy (SEM) and focused-ion-beam (FIB)-SEM. The crystals detected in the caries lesions were characterized by transmission electron microscopy (TEM), along with chemical element mapping using energy-dispersive spectroscopy (EDS)-STEM. FIB-SEM 3D reconstructions revealed a severely damaged dentin surface abundantly covered by bacteria. Although the dentin tubules were clogged up to a depth of 100 μm, bacterial invasion into dentin tubules was not observed. TEM crystal analysis and EDS-STEM revealed the presence of Ca and P, as well as of Mg within the HAp crystals deposited inside the dentin tubules. It was concluded that extensive remineralization with deposition of Mg-HAp crystals had occurred in dentin tubules of caries-arrested dentin. Understanding the natural remineralization process is thought to be helpful for developing clinical biomimetic remineralization protocols.
Highlights
The remineralization mechanism in dental caries lesions is not completely understood
Open dentin tubules were observed in dentin far away from the carious tissue, while filled tubules were observed near the caries lesion (Fig. 1Aa)
This study investigated the process of caries arrest due to remineralization within caries lesions by correlative ultra-structural characterization using scanning electron microscopy (SEM), Focused-ion-beam Scanning Electron Microscopy (FIB-SEM) and (S)transmission electron microscopy (TEM), combined with chemical analysis using energy-dispersive spectroscopy (EDS)-STEM and Selected Area Electron Diffraction (SAED)
Summary
The remineralization mechanism in dental caries lesions is not completely understood. Frank and Voegel[8] observed partially and completely calcified dentin tubules in the area between the translucent zone of carious dentin and inner dentin They did not report the presence of remineralized dentin in the immediate surrounding of the carious lesion. Many of these researches involved nano-scale observations of remineralization, the 3D structural organization of naturally remineralized dentin was not completely disclosed. Investigating remineralization, most studies have employed SEM and TEM to study in vitro remineralization in 2D, while the actual 3D process of natural in vivo remineralization has not been completely described far. An in-depth in/ex vivo study of caries and the involved de- and remineralization processes in human teeth may be very helpful to develop clinical strategies to achieve efficient tooth remineralization
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