Determination of Crystallite Size in Synthetic and Natural Hydroxyapatite: A Comparison between XRD and TEM Results

Comparison of the effectiveness of sodium-tri-metaphosphate-treated varnish containing eggshell and membrane powder and bioactıve glass varnish with fluoride varnish in preventing erosion: in vitro

The aim of this in vitro study was to compare the efficacy of sodium-tri-metaphosphate-treated varnish containing eggshell and membrane powder and bioactive glass varnish with fluoride varnish in preventing erosion. Two windows were created on the buccal surface of 72 molars for the erosion cycle. One of the windows was treated with fluoride varnish [(FV, Metroberry, Imicryl), varnish containing STMP-treated eggshell and membrane powder (EPV, BioViera, Imicryl) and bioactive glass varnish (BAG, Polimo, Imicryl)] while the other window was used as control. Acidic syrup (Atarax) was applied 3 times a day and acidic drink (Coca Cola) 4 times a day for 5 days. The samples were analyzed by SEM (n = 1), ATR-FTIR (n = 6) and Vicker's hardness (n = 5). Data were analyzed by one-way ANOVA and post hoc Tukey test. The protective effects of the varnishes were observed in the SEM images obtained. There was a difference between the FV and EPV groups in the 875 cm-1 v2 CO3-2 peak spectrum and microhardness values (p < 0.05). There was a difference between FV and FV-C in the carbonate v2 band in the acidic beverage demineralised varnish groups (p < 0.05). Other band areas and CO3-2 /PO4-3 ratios of the varnish areas against the erosion and control areas showed similar results (p > 0.05). Microhardness analyses showed that the BAG group demineralized with acidic syrup and the FV group demineralized with acidic drink were similar to the control group (p > 0.05). The varnishes tested in our study showed a similar protective effect against erosion as fluoride varnishes.

Characterization of Sm3+-activated carbonated calcium chlorapatite phosphors for theranostic applications: a comparative study of co-precipitation and hydrothermal methods

Continuous efforts are ongoing to discover new luminescent materials with appropriate properties for applications in medicine, serving as theranostic agents for healing and bioimaging. In this paper, novel single-phase carbonated calcium chlorapatite (Ca10(PO4)5(CO3)Cl2, abbreviated as CaClAp-CO3) phosphors activated with varying concentrations of Sm3+ ions were successfully fabricated using both co-precipitation and hydrothermal methods to investigate the influence of the synthesis techniques on the physicochemical properties of these materials. The effects of doping concentration of Sm3+ ions and synthesis techniques on the structure, photoluminescence (PL), energy transfer, substitute sites, fluorescence lifetime and luminescence colour of phosphors were investigated. The synthesized phosphors were characterized by X-ray diffraction (XRD) to confirm their crystal phase structure and purity. Vibrational features and the incorporation of carbonate ions were verified using Fourier-transform infrared (FTIR) spectroscopy. The obtained materials emit reddish-orange light, primarily from the most intense 4G5/2 → 6H7/2 transition. The electric dipole to magnetic dipole transition ratio (ED/MD), CIE colour coordinates and colour purity were determined to provide additional insights into the spectroscopic attributes of the obtained phosphors. In addition, the concentration quenching was also observed, and its mechanism was proposed based on theoretical calculations showing the multipolar interactions.

Nano-Hydroxyapatite Gel and Its Effects on Remineralization of Artificial Carious Lesions

Introduction

Nano-hydroxyapatite gel (NHG) has never been investigated for enamel remineralization. This study evaluated the effects of two concentrations of NHG on remineralization of an artificial carious lesion in comparison with nano-HA toothpaste (NHT) and fluoride varnish (FV).

Materials and Methods

Carious lesions were prepared on 100 enamel samples and divided into 5 groups: FV, NHT, 20% NHG, and 30% NHG. One untreated (NT) group was left as control. The hardness of the surface was evaluated before, during, and after remineralization. Microhardness at various phases and the percent recovery of hardness (%HR) were determined and analyzed with ANOVA. Polarized-light micrographs (PLM) were evaluated for depth of the carious lesion.

Results

Significantly different remineralization capability was indicated for tested agents (p < 0.05). NHT was significantly capable of remineralization greater than NHG, FV, and NT (p < 0.05). No noticeable difference in %HR between 20% NHG and 30% NHG (p > 0.05) was found. Decreasing in the depth of caries lesion was notified by PLM as applying either NHT or NHG as greater than FV, with no reduction in the depth for NT.

Conclusions

Nano-HA both in toothpaste and gel form was capable of remineralization better than fluoride varnish. Comparable remineralization of 20% versus 30% NHG was evidenced. NHG for both concentrations was recommended as a capable remineralizing agent for caries remineralization. Clinical Significance: This study indicated that an application of nano-HA gel is an attractive route to deliver the material and can be more effective and less toxic than conventional formulations and provide its effectiveness directly at the site of action, especially for a noncooperative young child and medicinally intimidated patients who may face with inconvenience in using toothbrush and toothpaste for hygiene control.

Biomimetic 3D-printed PCL scaffold containing a high concentration carbonated-nanohydroxyapatite with immobilized-collagen for bone tissue engineering: enhanced bioactivity and physicomechanical characteristics

A challenging approach of three-dimensional (3D)-biomimetic scaffold design for bone tissue engineering is to improve scaffold bioactivity and mechanical properties. We aimed to design and fabricate 3D-polycaprolactone (PCL)-based nanocomposite scaffold containing a high concentration homogeneously distributed carbonated-nanohydroxyapatite (C-nHA)-particles in combination with immobilized-collagen to mimic real bone properties. PCL-scaffolds without/with C-nHA at 30%, 45%, and 60% (wt/wt) were 3D-printed. PCL/C-nHA60%-scaffolds were surface-modified by NaOH-treatment and collagen-immobilization. Physicomechanical and biological properties were investigated experimentally and by finite-element (FE) modeling. Scaffold surface-roughness enhanced by increasing C-nHA (1.7 - 6.1-fold), but decreased by surface-modification (0.6-fold). The contact angle decreased by increasing C-nHA (0.9 - 0.7-fold), and by surface-modification (0.5-fold). The zeta potential decreased by increasing C-nHA (3.2-9.9-fold). Average elastic modulus, compressive strength, and reaction force enhanced by increasing C-nHA and by surface-modification. FE modeling revealed that von Mises stress distribution became less homogeneous by increasing C-nHA, and by surface-modification. Maximal von Mises stress for 2% compression strain in all scaffolds did not exceed yield stress for bulk-material. 3D-printed PCL/C-nHA60% with surface-modification enhanced pre-osteoblast spreading, proliferation, collagen deposition, alkaline phosphatase activity, and mineralization. In conclusion, a novel biomimetic 3D-printed PCL-scaffold containing a high concentration C-nHA with surface-modification was successfully fabricated. It exhibited superior physicomechanical and biological properties, making it a promising biomaterial for bone tissue engineering.

Hydroxyapatite-biopolymers-ZnO composite with sustained Ceftriaxone release as a drainage system for treatment of purulent cavities

Composite based on nano-sized hydroxyapatite (HA), zinc oxide (ZnO), chitosan (CS), alginate (Alg) with the function of sustained Ceftriaxone (CF) release was created as molecular sorption-aspiration drainage system (SADS), designed for the treatment of purulent cavities of various genesis, including peritonitis. ZnO stabilizes the composite structurally, reducing the swelling by 1.5 and porosity by 1.4 times. The absorption of tryptophan (Trp) by SADS for 72 h from aqueous solution is 80%, while from PBS - 50%. The content of ZnO (15,20%) slows the CF release by 1.6 times on the first day of SADS installation and reduces the likelihood of "burst" drug release. CF release exponent of ZnO-containing composites indicates the non-Fickian diffusion kinetics. 20%ZnO-containing composite is closest to zero-order kinetics. The reduction of the concentration of E. coli microbial cells for 43% in the presence of HA-nZnO-Alg/CS -based CADS and positive therapeutic pathomorphosis were observed in vivo.

Remineralization Potential of Nanohydroxyapatite Toothpaste Compared with Tricalcium Phosphate and Fluoride Toothpaste on Artificial Carious Lesions

Introduction

Nanohydroxyapatite (nano-HA) has been utilized as an alternative agent for dental enamel remineralization. This study compared remineralization potential of nano-HA toothpaste (NHT), functionalized tricalcium phosphate toothpaste (TCPT), and fluoride toothpaste (FT) on carious lesions.

Materials and Methods

Sixty extracted human premolars were prepared for artificial carious lesions with synthetic polymer gel. Samples were divided into four groups according to testing agents: NHT, TCPT, FT, and one group with no treatment (NT). Each group was subjected to pH-cycling with the application of toothpaste in slurry form twice a day (2-min each) for 10 days. Surface microhardness was measured before demineralization, after demineralization, and after pH-cycling. Hardness at different periods, percentage of hardness recovery (% HR), and percentage of remineralization potential (%RP) were determined and statistically analyzed with ANOVA and Tukey comparisons (α = 0.05). Polarized light microscopy (PLM) was utilized to assess lesion depth.

Results

Significant remineralization of carious lesions was observed among different toothpastes compared to NT (p < 0.05). No significant difference in remineralization potential was found among NHT, TCPT, and FT (p > 0.05). No significant difference in % HR and % RP was seen among NHT, TCPT, and FT (p > 0.05). PLM indicated a greater decrease in carious depth upon using NHT compared to TCPT and FT, with minimal increase in depth for NT.

Conclusions

NHT has comparable capability to TCPT and FT in hardness recovery. However, decrease in carious depth was evidenced with PLM for NHT more than TCPT and FT. Thus, NHT was suggested as a potential remineralization product for treating initial carious lesions. Clinical Significance. The study showed that NHT had the potential to remineralize artificial carious lesion. It was confirmed in potential in the lesion depth reduction and forming a new enamel layer. NHT showed its capability as an alternative for dental caries therapeutic.

Unexpectedly High Adsorption Capacity of Esterified Hydroxyapatite for Heavy Metal Removal

Nanohydroxyapatite (n-HAP) as an environmentally friendly adsorbent of heavy metal ions still requires the rational design of the pore structure and surface characteristic for enhancing their adsorption capacity toward heavy metal ions. A novel one-step strategy was developed to regulate the pore structure and surface characteristic of esterified HAP (n-EHAP) nanocrystals (NCs) for enhancing the adsorption capacity by incorporation of 2-bromo-2-methylpropionate (2-BrMP) groups on the surface of n-EHAP NCs. When using water as the sole solvent, the aggregation of n-EHAP NCs became unavoidable because of incorporation of hydrophobic 2-BrMP groups on n-HAP particle surfaces. The synthesis of uniform and individual n-EHAP NCs was achieved by rational adjustment of the aqueous dispersion medium to avoid agglomeration and precipitation, which was induced by the changing surface characteristic of n-EHAP NCs during the continuing incorporation of hydrophobic 2-BrMP groups in the water/acetone system. The successful incorporation of hydrophobic 2-BrMP groups on the surface of n-EHAP NCs was characterized by X-ray powder diffraction, field-emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and liquid nitrogen adsorption isotherms. To explore the potential application in water treatment, a series of systematically designed batch experiments were conducted to determine the influences of the adsorbent dosage, solution pH, and contact time on the adsorption behavior of n-EHAP NCs. Experimental results indicated that the addition of water-soluble acetone greatly promoted the formation of individual n-EHAP NCs without aggregation, and furthermore, the successful incorporation of hydrophobic 2-BrMP groups led to formation of porously structured n-EHAP NCs with a higher surface area and an increasing micro-/mesopore ratio. Compared with pristine n-HAP, n-EHAP NCs exhibited lower crystallinity with smaller crystallite size and demonstrated an ultrahigh adsorption capacity for Pb(II) in acidic solution with a record of close to 2400 mg/g. The improved performance of n-EHAP NCs originated from both the suitable porous structure with a higher micro-/mesoporosity ratio and the existing tethered 2-BrMP group-induced the ester bond, providing more adsorption active affinity sites for heavy metal ions. The highly efficient adsorption (99.99%) was further achieved using tap water spiked with traces of Pb(II) (63 ppb). The presented findings promise the application of n-EHAP NCs in water treatment as an alternative, low-cost, and ecofriendly adsorbent for environmental remediation.