Characterization of enamel with variable caries risk

Nanostructure of carious tooth enamel lesion

Carious lesions exhibit a complex structural organization composed of zones of higher and lower mineralization, formed by successive periods of cyclic de- and re-mineralization. A thorough understanding of the lesion morphology is necessary for the development of suitable treatments aiming to repair rather than replace the damaged tissue. This detailed understanding includes the entire lesion down to individual crystallites and nanopores within the natural organization of the crown. A moderate lesion, with surface loss and reaching dentin, and a very early lesion were studied. Scanning small-angle X-ray scattering (SAXS) with a pixel size of 20 × 20 μm(2) was used to characterize these lesions, allowing for the identification of distinct zones with varied absorption and scattering behavior, indicative of varied porosity and pore morphology. Despite these differences, the overall orientation and anisotropy of the SAXS signal was unaltered throughout both lesions, indicating that an anisotropic scaffold is still present in the lesion. The finding that crystallite orientation is preserved throughout the lesions facilitates the identification of preventive re-mineralizing strategies with the potential to recreate the original nanostructure.

Demineralization of enamel in primary second molars related to properties of the enamel

Enamel structure is of importance in demineralization. Differences in porosity in enamel effect the rate of demineralization, seen between permanent and deciduous teeth. Individual differences have been shown in the mean mineral concentration values in enamel, the role of this in demineralization is not thoroughly investigated. The aim of this study was to study variations of depths of artificial lesions of demineralization and to analyze the depth in relation to variations in the chemical and mineral composition of the enamel. A demineralized lesion was created in second primary molars from 18 individuals. Depths of lesions were then related to individual chemical content of the enamel. Enamel responded to demineralization with different lesion depths and this was correlated to the chemical composition. The carbon content in sound enamel was shown to be higher where lesions developed deeper. The lesion was deeper when the degree of porosity of the enamel was higher.

Chemical and crystallographic study of remineralized surface on initial carious enamel treated with Galla chinensis

To investigate the morphologic, chemical and crystallographic characters of remineralized surface on initial carious enamel treated with Galla chinensis, scanning electron microscopy equipped with energy dispersive analysis spectroscopy were used, and X-ray microdiffraction (microzone XRD) was used for the first time to analyze in situ the microzone crystallite of remineralized surface on carious enamel. Bovine sound enamel slabs were demineralized to produce initial carious lesion in vitro. Then, the lesions were exposed to a pH-cycling regime for 12 days of remineralization. Each daily cycle included 4x1 min applications with one of the three treatments: distilled and deionized water (DDW); 1 g/L NaF; 4 g/L G. chinensis extract (GCE). After the treatments, some rod-like deposits and many irregular prominences were found on GCE-treated enamel surface, and the intensities of Ca and P signals showed a tendency to increase; Ca:P ratio was significantly higher than that of DDW-treated enamel. X-ray microdiffraction showed hydroxyapatite was still the main component of GCE-treated enamel, and the crystallinity was increased, the crystal lattice changed gently with decreased lattice parameter a. These results indicated the potential of GCE in promoting the remineralization of initial enamel carious lesions, and supported the previous hypothesis about GCE mechanism. Combined with the anti-bacteria and demineralization inhibition properties of GCE, the natural G. chinensis may become one more promising agent for caries prevention.