Biomineralization of Dental Tissues Treated with Silver Diamine Fluoride

Silver diamine fluoride (SDF) is a dental biomaterial used to arrest dental caries. To better understand SDF’s mechanism of action, we examined the localization of silver within the tissues of SDF-treated teeth. Carious primary teeth fixed within 2 min of SDF application (SDF-minutes, n = 3), at 3 wk after SDF application in vivo (SDF-weeks, n = 4), and at 2 y after multiple SDF applications in vivo (SDF-multiple, n = 1) were investigated in this study. Carious primary teeth without SDF application (no-SDF, n = 3) served as controls. Mineral density and structural analyses were performed via micro–X-ray computed tomography and scanning electron microscopy. Elemental analyses were performed through X-ray fluorescence microprobe and energy-dispersive X-ray spectroscopic techniques. SDF-treated teeth revealed higher X-ray–attenuated surface and subsurface regions within carious lesions, and similar regions were not present in no-SDF teeth. Regions of higher mineral density correlated with regions of silver abundance in SDF-treated teeth. The SDF penetration depth was approximated to 0.5 ± 0.02 mm and 0.6 ± 0.05 mm (mean ± SD) for SDF-minutes and SDF-weeks specimens, respectively. A higher percentage of dentin tubular occlusion by silver or calcium phosphate particles was observed in primary teeth treated with SDF-weeks as compared with SDF-minutes. Elemental analysis also revealed zinc abundance in carious lesions and around the pulp chamber. SDF-weeks teeth had significantly increased tertiary dentin than SDF-minutes and no-SDF teeth. These results suggest that SDF treatment on primary teeth affected by caries promotes pathologic biomineralization by altering their physicochemical properties, occluding dentin tubules, and increasing tertiary dentin volume. These seemingly serendipitous effects collectively contribute to the cariostatic activity of SDF.

Morphological Characterization of Calcium Phosphate Particles Obtained by Pulsed-Injection Metal Organic Chemical Vapor Deposition

ABSTRACTAmorphous calcium phosphate particles were synthesized for the first time by the Pulsed Injection Chemical Vapor Deposition technique onto silicon wafers, using Trimethyl Phosphate and Calcium Lactate mixed in a methanol solution as the precursor. The particles were deposited at a substrate temperature of 500, 550, and 600 °C obtaining the best results at 500 °C in terms of nucleation, density, morphology, and Ca/P ratio. The functional groups and vibrational modes, elemental composition, and surface morphology, were studied using Fourier Transform Infrared Spectroscopy, Raman Spectroscopy, and X-ray Energy Dispersion Spectrometry, and Scanning Electron Microscopy, respectively. The presence of the phosphate group characteristic of calcium phosphate was also observed. Uniform growth of the microstructures as the growth time and the temperature of the substrate increases were also observed, together with agglomerates of calcium phosphate in microstructures of 10, 50, and 100 nm in diameter. In these calcium phosphate agglomerates, calcium and phosphorus presence were observed, which is an important feature due to the Ca/P ratio gives information regarding biocompatibility.

Burst, Short, and Sustained Vitamin D3 Applications Differentially Affect Osteogenic Differentiation of Human Adipose Stem Cells

Incorporation of 1,25(OH)2 vitamin D3 (vitD3) into tissue-engineered scaffolds could aid the healing of critical-sized bone defects. We hypothesize that shorter applications of vitD3 lead to more osteogenic differentiation of mesenchymal stem cells (MSCs) than a sustained application. To test this, release from a scaffold was mimicked by exposing MSCs to exactly controlled vitD3 regimens. Human adipose stem cells (hASCs) were seeded onto calcium phosphate particles, cultured for 20 days, and treated with 124 ng vitD3, either provided during 30 min before seeding ([200 nM]), during the first two days ([100 nM]), or during 20 days ([10 nM]). Alternatively, hASCs were treated for two days with 6.2 ng vitD3 ([10 nM]). hASCs attached to the calcium phosphate particles and were viable (~75%). Cell number was not affected by the various vitD3 applications. VitD3 (124 ng) applied over 20 days increased cellular alkaline phosphatase activity at Days 7 and 20, reduced expression of the early osteogenic marker RUNX2 at Day 20, and strongly upregulated expression of the vitD3 inactivating enzyme CYP24. VitD3 (124 ng) also reduced RUNX2 and increased CYP24 applied at [100 nM] for two days, but not at [200 nM] for 30 min. These results show that 20-day application of vitD3 has more effect on hASCs than the same total amount applied in a shorter time span.

The study of the microstructure of cheese before and after vacuum drying

Scanning electron microscope allowed us to get screens of different cheese microstructure that form a base for further investigation of a cheese structure state before and after the process of drying and for their comparison. Any cheese structure presents a matrix of proteins penetrated with moisture capillaries; fat globules are located both inside the protein matrix and on a cheese surface. Shape of capillaries is either round or oval. Capillaries vary in size and number that has an impact on the cheese pattern which is described by hole and void shapes and order. Electron microscopy was also used for detecting deposition of calcium phosphate. Particles of calcium phosphate changed in size, before drying they were 10–12 µm, and after drying they reached 20–30 µ. These particles concentrate in the dried cheese and agglomerate into larger particles. The most concentrated calcium phosphate proportion was found in pores and micro-voids of the dry cheese. As for mature cheese samples, calcium lactate was established as well.

Poly(propylene fumarate)/magnesium calcium phosphate injectable bone composite: Effect of filler size and its weight fraction on mechanical properties

This study aimed to produce a composite of poly(propylene fumarate)/magnesium calcium phosphate as a substitutional implant in the treatment of trabecular bone defects. So, the effect of magnesium calcium phosphate particle size, magnesium calcium phosphate:poly(propylene fumarate) weight ratio on compressive strength, Young’s modulus, and toughness was assessed by considering effective fracture mechanisms. Micro-sized (∼30 µm) and nano-sized (∼50 nm) magnesium calcium phosphate particles were synthesized via emulsion precipitation and planetary milling methods, respectively, and added to poly(propylene fumarate) up to 20 wt.%. Compressive strength, Young’s modulus, and toughness of the composites were measured by compressive test, and effective fracture mechanisms were evaluated by imaging fracture surface. In both micro- and nano-composites, the highest compressive strength was obtained by adding 10 wt.% magnesium calcium phosphate particles, and the enhancement in nano-composite was superior to micro-one. The micrographs of fracture surface revealed different mechanisms such as crack pinning, void plastic growth, and particle cleavage. According to the results, the produced composite can be considered as a candidate for substituting hard tissue.