No description available.

The aim of this study was to investigate the microstructure, microhardness and biocompatibility properties of nano hydroxyapatite (HA) doped with a constant yttrium (Y3+) and varying fluoride (F-) compositions. HA was synthesized via precipitation method and sintered at 1100&amp / #61616 / C for 1 hour. Increased densities were achieved upon Y3+ doping while F- doping led to a decrease in densities. For structural analysis, XRD, SEM and FTIR spectroscopy examinations were performed. No secondary phases were observed in XRD studies upon doping. Lattice parameters decreased due to substitutions of ions. In SEM analysis, addition of doping ions was observed to result in smaller grains. In FTIR analysis, in addition to the characteristic bands of HA, novel bands indicating the substitution of F- ions were observed in F- ion doped samples. The highest microhardness value was obtained for the sample doped with 2.5%Y3+, 1%F-. Increased F- ion contents resulted in decreased microhardness values. For biocompatibility evaluation, in vitro tests were applied to the materials. MTT assay was performed for Saos-2 cell proliferation analysis. Y3+ and F- ion incorporation was found to improve cell proliferation on HA discs. Cells were found to attach and proliferate on disc surfaces in SEM analysis. ALP assay showed differentiation of cells on the discs can be improved by doping HA with an optimum amount of F- ion. Dissolution tests in DMEM revealed that structural stability of HA was improved with F- ion incorporation. The material exhibiting optimum structural, mechanical and biocompatibility properties was HA doped with 2.5%Y3+, 1%F-.

Caries is one of the most common diseases in dentistry. The key to preventing caries is the balance between demineralization and remineralization. Dental delivery methods such as toothpaste, gels, and varnishes are commonly applied as preventative methods against caries. With the advancement of nano-technology, dentistry can supplement traditional diagnostic and treatment methods with more advanced, efficient, and personalized dental care. Hydroxyapatite (HA) is a biomimetic agent that aims to remineralize and protect the enamel from erosion. It is formed by nanoparticles similar to apatite crystals of tooth enamel. Furthermore, it is one of the most biocompatible and bioactive materials. Because HA is present in our enamel, it will be proven as an effective biomimetic agent for the prevention and remineralization of caries. The Caries Management by Risk Assessment (CAMBRA) tool helps dental care professionals identify high-risk patients more susceptible to caries. With the addition of biomimetic agents such as hydroxyapatite, dentists can effectively provide treatment to detect early-stage lesions and correctly intervene with remineralization techniques in all patient types. Studies have shown that HA toothpastes have anti-bacterial properties against S. mutans caries causing bacteria, and inhibit demineralization, similar to fluoride. In orthodontic patients, no significant difference was found between fluoride and HA dentifrice on caries progression nor between HA and fluoride gel in remineralizing initial caries. Similar reports found non-inferiority of hydroxyapatite toothpaste compared to fluoride toothpaste. Fluoride's mechanism of action differs from HA in that hydroxyapatite protects enamel by creating a new layer of enamel, and fluoride hardens the existing enamel layer. A comparison of three biomimetic agents, Casein Phosphopeptides Amorphous Calcium Phosphate (CPP-ACP), Tricalcium Phosphate (TCP), and hydroxyapatite found hydroxyapatite to have the highest amount of remineralization with nHA being more effective in managing early caries and decreasing lesion depth. Hydroxyapatite toothpaste was also shown to be a favorable alternative to oxidizing bleaching agents and zinc-carbonate hydroxyapatite being more effective than a fluoride/potassium nitrate dentifrice in reducing dentin hypersensitivity. With the high consumption of acidic food and beverages, a Zinc-nHA toothpaste was to be more effective than fluoride toothpaste in remineralization and protection after the acid attack and demineralization from Coca-Cola. In conclusion, with the reported results of the studies in this paper, it is known that nano- hydroxyapatite is an effective and safe alternative to fluoride. Many studies have proven nano-hydroxyapatite effective in helping to remineralize early carious lesions. In some studies, it is just as promising as fluoride is. It is especially beneficial for high-risk patients to implement nHA into their oral care routine. Nano-hydroxyapatite (nHA) has been proven to promote remineralization, inhibit demineralization, whiten teeth, protect against dental erosion, and reduce dentin hypersensitivity.

In this study, it was aimed to investigate the structural, mechanical and biological properties of nano hydroxyapatite (HA) doped with yttrium and fluoride with different compositions. HAs were synthesized by precipitation method. After sintering at 900oC, 1100oC or 1300oC for 1 hour, the structural properties of HAs were investigated by XRD, FTIR spectroscopy and SEM. High relative densities (above 88 % of relative density) were achieved after sintering. No second phases were observed in XRD measurements. Hexagonal lattice parameters and unit cell volumes of doped HAs decreased indicating the substitutions of ions. Characteristics absorbtion bands of HA and additional bands due to fluoride substitutions were observed in FTIR patterns. SEM images showed that grain sizes decreased with increasing doping amounts and decreasing sintering temperatures. Discs prepared by cold pressing were sintered at 900oC, 1100oC and 1300oC for 1 hour to determine mechanical properties. Mechanical properties of HAs were found to be directly related to the sintering temperatures and amount of dopings. Biocompatibility of pure and doped HA discs was assessed with in vitro cytotoxicity studies. Cell attachment, proliferation and differentiation state of cells were studied using MTT, ALP and calcium assays and SEM. Cell attachment and proliferation were enhanced with dopings and increasing sintering temperatures. The highest ALP production and calcium deposition were observed on HAs sintered at 1100oC. In vitro studies revealed that 1100oC was the sintering temperature for best cell responses. Specifically, 2.5YFHA seemed to be promising as an alternative for pure HA among all doped HAs.

Indiana University-Purdue University Indianapolis (IUPUI) / The effects of hydroxyapatite in a DAP-loaded MC carrier on dental pulp stem cells Introduction: Regenerative endodontic procedures (REP) require disinfection techniques to eliminate bacteria from the infected immature root canal system and promote new growth of the pulp-dentin complex. Double antibiotic paste (DAP), a mixture of ciprofloxacin and metronidazole, has shown efficacy in doing so while minimizing cytotoxicity on dental pulp stem cells (DPSC). Stem cells, scaffolding, and growth factors are necessary in the maturation, proliferation, and differentiation of mesenchymal stem cells into the root canal system. Nano-hydroxyapatite (n-HA) has a history of biocompatibility and, in addition, has shown promising effects as a tissue bioengineering material. Objective: The aim of this in vitro study was to investigate the proliferation and mineralization of DPSC in the presence of 1% DAP and methylcellulose (MC) with varying concentrations of nano-hydroxyapatite. Materials and Methods: DPSC were plated in 24-well plates containing culture media. The next day, semi-permeable 0.1 mm Transwell chambers were inserted into the wells to separate the reservoirs for medicaments. Treatment paste composed of methylcellulose containing 1% DAP with either 0.25%, 0.50%, or 1.0% nano-hydroxyapatite was added along with culture media. Methylcellulose alone and calcium hydroxide (Ultracal) were used as control groups. After 3 days, cells were evaluated for cytotoxic effects using an MTS proliferation assay (n = 10, in triplicate). DPSCs were also cultured with these medicaments for 7 days in osteogenic media and evaluated for alkaline phosphatase (ALP) activity and mineralization activity (n = 13, in triplicate). Comparisons between groups for differences in mineralization, BSA, and ALP activity were performed using analysis of variance (ANOVA), with different variances allowed for each group and a random effect included in the model to account for correlation within each of the three trials. A simulation-based model was used to adjust for multiple comparisons. Results: Addition of n-HA treatment groups increased mineralization significantly greater than calcium hydroxide, with MC alone and MC+DAP+0.5% HA providing the greatest effect. Regarding ALP, all HA concentrations performed significantly greater than MC and DAP concentrations. Proliferation demonstrated similar metabolic activity in all experimental groups with few comparisons significant. Conclusion: The challenge in REPs is to maintain survival, and preferably promote the proliferation and development of DPSCs into the pulp-dentin complex with a consistent treatment outcome. The combination of DAP with hydroxyapatite may allow for both disinfection and improved mineralization and cellular differentiation. This contribution has shown significant ability to increase stem cell differentiation into an osteogenic lineage as well as calcium deposition, indicating end goal results of regenerative procedures.