Risk Factors Associated with Black Tooth Stain

The aim of the study was to show whether there is any influence of food, drink or drug intake on the formation of tooth discoloration. A total of 500 patients aged 15-25 years were examined to take part in the study. Of these, 60 patients were selected and divided into two groups of 30 patients each. Group 1 included patients with black pigmentation on vestibular/oral tooth surfaces. Group 2 included patients without discoloration (control). Data were recorded in a questionnaire. Atomic absorption spectrometry was used to determine elements in discoloration samples. The Caries Risk Test (CRT) buffer was used to assess buffer capacity of saliva, while CRT bacteria were used to determine the presence of Streptococcus mutans and Lactobacillus spp. Statistically significant between-group differences were found for the intake of collard greens and beets (p<0.05), but not for other vegetables. As for drink consumption, patients with pigmentation reported less wine intake (p<0.05) than those without pigmentation. There was no difference according to drug intake between patients with and without pigmentation. Patients with pigmentation were older, smoked and had lower saliva pH with lower presence of Streptococcus mutans than those without pigmentation (p<0.05). In tooth discoloration samples, there were traces of calcium, magnesium, iron, copper and zinc. The appearance of tooth discoloration is influenced by many factors, among which diet and saliva seem to be very important. Our study showed that patients with black pigmentation used to take more beets, while patients without pigmentation were taking more collard greens and red wine.

Role of subcolloidal (nanosized) precursor species in the early stage of the crystallization of zeolites in heterogeneous systems.

A critical analysis was carried out for the purpose of understanding the role of subcolloidal (nanosized) (alumino)silicate precursor species in the early stage of crystallization of zeolites in heterogeneous systems (hydrogels). The formation and evolution of these subcolloidal species in both the solid and the liquid phases were investigated by various experimental methods such a scanning electron microscopy (SEM, FE-SEM), transmission electron microscopy, atomic force microscopy, particle size analysis, pH measurement, atomic absorption spectroscopy, and dynamic light scattering, after careful separation of intermediates from reaction mixture by two-step centrifugation treatment. The results revealed that a chain of processes (i) the formation of low-molecular-weight (LMW) silicate species, by dissolution of Al-enriched amorphous silica, and their aggregation into about 3 nm sized primary precursor species (PPSs), (ii) the formation of larger (∼3 to ∼15 nm sized) silicate precursor species (LSPSs) by a rapid aggregation/coalescence of PPSs, (iii) the formation of "gel" (primary amorphous precursor) by a random aggregation of LSPSs at room temperature, and (iv) the formation of the worm-like particles (secondary amorphous precursor) occurred in the solid phase during heating of the reaction mixture (hydrogel) from room temperature to 170 °C. It is interesting that almost the same processes occur in the liquid phase but with decreased rate according to the relative low concentration of LMW silicate species. With the above described findings, it is highly expected that the manipulation of crystallization pathway through controlling the formation/evolution of precursor species in the initial stage of the process can be achieved.

Design and degradation of permanently porous vitamin C and zinc-based metal-organic framework.

Bioapplication is an emerging field of metal-organic frameworks (MOF) utilization, but biocompatible MOFs with permanent porosity are still a rarity in the field. In addition, biocompatibility of MOF constituents is often overlooked when designing bioMOF systems, intended for drug delivery. Herein, we present the a Zn(II) bioMOF based on vitamin C as an independent ligand (bioNICS-1) forming a three-dimensional chiral framework with permanent microporosity. Comprehensive study of structure stability in biorelavant media in static and dynamic conditions demonstrates relatively high structure resistivity, retaining a high degree of its parent specific surface area. Robustness of the 3D framework enables a slow degradation process, resulting in controllable release of bioactive components, as confirmed by kinetic studies. BioNICS-1 can thus be considered as a suitable candidate for the design of a small drug molecule delivery system, which was demonstrated by successful loading and release of urea-a model drug for topical application-within and from the MOF pores.