Scanning Electron Microscopy and Electron Probe Microanalyses of the Crystalline Components of Human and Animal Dental Calculi

A review of the use of scanning electron microscopy (SEM) and electron probe microanalyses in the study of dental calculus showed that such studies provided confirmatory and supplementary data on the morphological features of human dental calculi but gave only limited information on the identity of the crystalline or inorganic components. This study aimed to explore the potential of combined SEM and microanalyses in the identification of the crystalline components of the human and animal dental calculi. Human and animal calculi were analyzed. Identification of the crystalline components were made based on the combined information of the morphology (SEM) and Ca/P molar ratios of the crystals with the morphology and Ca/P molar ratio of synthetic calcium phosphates (brushite or DCPD; octacalcium phosphate, OCP; Mg-substituted whitlockite, -TCMP; CO3-substituted apatite, (CHA); and calcite. SEM showed similarities in morphological features of human and animal dental calculi but differences in the forms of crystals present. Microanalyses and crystal morphology data suggested the presence of CaCO3 (calcite) and CHA in the animal (cat, dog, tiger) and of OCP, -TCMP and CHA in human dental calculi. X-ray diffraction and infrared (IR) absorption analyses confirmed these results. This exploratory study demonstrated that by taking into consideration what is known about the crystalline components of human and animal dental calculi, combined SEM and microanalyses can provide qualitative identification

Scanning and Transmission Electron Microscopy, and Electron Probe Analysis of the Interface Between Implants and Host Bone

Bioinert materials (e.g., alumina implants) and bioactive ceramics (e.g., calcium phosphate ceramics, glass -ceramics) are now extensively used in dentistry. However, the physico-chemical interactions at the interfaces between the implant and the host bone are poorly understood. The purpose of this study was to define the interactions at these interfaces using a combination of analytical techniques: light microscopy, scanning and transmission electron microscopy, electron probe microanalysis, X-ray microradiography, X-ray diffraction, and infrared specstroscopy. Bioinert (pure titanium) and bioactive materials (hydroxyapatite, beta-tricalcium phosphate and biphasic calcium phosphate) were implanted in dogs, and the implants, recovered after various periods of implantation, were analyzed. The results demonstrated the following: the bioactive materials interact with the biological fluid and the living tissues in a specific manner. This process includes biodissolution/biodegradation, apatite crystal precipitation, and bone formation on the implant surface at the expense of the material. The results are discussed according to the limitations of the analytical techniques used. The medical and chemical word COALESCENCE is suggested to describe the specific interactions of bioactive materials and INTERACTION for the phenomenon of physical contact of the bioinert materials with the host bone

Enhanced stability and local structure in biologically relevant amorphous materials containing pyrophosphate

There is increasing evidence that amorphous inorganic materials play a key role in biomineralisation in many organisms, however the inherent instability of synthetic analogues in the absence of the complex in vivo matrix limits their study and clinical exploitation. To address this, we report here an approach that enhances long-term stability to >1 year of biologically relevant amorphous metal phosphates, in the absence of any complex stabilisers, by utilising pyrophosphates (P2O7 4-); species themselves ubiquitous in vivo. Ambient temperature precipitation reactions were employed to synthesise amorphous Ca2P2O7.nH2O and Sr2P2O7.nH2O (3.8 < n < 4.2) and their stability and structure were investigated. Pair distribution functions (PDF) derived from synchrotron X-ray data indicated a lack of structural order beyond ~8 A° in both phases, with this local order found to resemble crystalline analogues. Further studies, including 1H and 31P solid state NMR, suggest the unusually high stability of these purely inorganic amorphous phases is partly due to disorder in the P–O–P bond angles within the P2O7 units, which impede crystallization, and to water molecules, which are involved in H-bonds of various strengths within the structures and hamper the formation of an ordered network. In situ high temperature powder X-ray diffraction data indicated that the amorphous nature of both phases surprisingly persisted to ~450° C. Further NMR and TGA studies found that above ambient temperature some water molecules reacted with P2O7 anions, leading to the hydrolysis of some P–O–P linkages and the formation of HPO4 2- anions within the amorphous matrix. The latter anions then recombined into P2O7 ions at higher temperatures prior to crystallization. Together, these findings provide important new materials with unexplored potential for enzyme-assisted resorption and establish factors crucial to isolate further stable amorphous inorganic materials

Solution-Mediated Transformation of Octacalcium Phosphate (OCP) to Apatite

OCP crystals were hydrolyzed in solutions containing Ca2+, Mg2+, HPO42-, CO32-, F-, citrate or P2O7 ions. Products of hydrolysis were analyzed using scanning (SEM) and transmission (TEM) electron microscopy, infrared spectroscopy and x-ray diffraction. Results demonstrated that the OCP to Apatite (AP) transformation is influenced by: (1) types of ions in solution: inhibited by Mg2+, citrate or P2O74-; facilitated by F-, CO32-, HPO42- or Ca2+ ions; (2) ionic concentrations; (3) solution pH; (4) OCP crystal size. SEM showed needle-like micro-crystals on the surfaces and ends of OCP macrocrystals. TEM showed side-to-side and end-to-end arrangements and presence of central defects in the apatite crystals. IR spectra showed the incorporation of CO3, or HPO4, the HPO4 incorporation being least from F-containing solutions. These results suggest that OCP to AP transformation occurred by the process of dissolution of OCP and subsequent precipitation of Ca-deficient apatites, incorporating CO32-, HPO42- or F- present in solution. These results indicate that the observed stabilty of OCP in pathological calcifications may be due to the presence of Mg2+, citrate and/or P2O74- and/or low levels of CO32-, F-, Ca2+, HPO42- ions in the biological fluids

Biphasic Calcium Phosphate Bioceramics for Orthopaedic Reconstructions: Clinical Outcomes

BCP are considered the most promising biomaterials for bone reconstruction. This study aims at analyzing the outcomes of patients who received BCP as bone substitutes in orthopaedic surgeries. Sixty-six patients were categorized according to the etiology and morphology of the bone defects and received scores after clinical and radiographic evaluations. The final results corresponded to the combination of both parameters and varied from 5 (excellent result) to 2 or lower (poor result). Most of the patients who presented cavitary defects or bone losses due to prosthesis placement or revision, osteotomies, or arthrodesis showed good results, and some of them excellent results. However, patients with segmental defects equal or larger than 3 cm in length were classified as moderate results. This study established clinical parameters where the BCP alone can successfully support the osteogenic process and where the association with other tissue engineering strategies may be considered

Effect of calcium phosphate compound (MZF-CaP) with and without fluoride in preventing bone loss in ovariectomized rats

Zinc (Zn) has been shown to inhibit osteoclast differentiation, promote osteoblast activity, and enhance the bone formation. Zinc-containing calcium phosphate (Zn-TCP) implanted in rabbit femoral defect was demonstrated to stimulate bone formation. Other studies demonstrated that calcium phosphate compounds (MZF-CaP) incorporating magnesium (Mg2+), zinc and fluoride (F-) when administered either by injection or orally were effective in preventing bone loss (osteoporosis) induced by estrogen deficiency (ovariectomy) in a rat model. The objective of the present study was to investigate the preventive effect of similar compound, with F (MZF-CaP-L, MZF-CaP-H) and without F (MZ-CaP-L), when injected in ovariectomized (OVX) rats. MZF-CaP-L and MZ-CaP-L were prepared by precipitation at 90oC and MZF-CaP-H was prepared by sintering MZF-CaP-L at 900oC. The release of the ions from acidic buffer was determined. Suspensions of Zn-TCP, MZF-CaP-H, MZF-CaP-L and MZ-CaP-L (617 μg in 0.2 ml of 1% sodium alginate saline solution) were injected intramuscularly under anesthesia into 5-week-old OVX rats on Zn-deficient diet. One week after surgery, bone mineral density (BMD) and bone mineral content (BMC) of the rat femurs were measured using X-ray CT. The injections and X-ray CT and Zn ion plasma measurements were repeated every week for 12 weeks. The rats were sacrificed and the femurs removed after 12 weeks. Bone mechanical strength was evaluated using the three-point bending test. MZ-CaP-L (without F), compared to the other compounds, showed the highest increase in the Zn2+ ion plasma concentration, and the highest BMD, BMC and mechanical strength

Fluoride-containing bioactive glasses: Effect of glass design and structure on degradation, pH and apatite formation in simulated body fluid

NOTICE: this is the author’s version of a work that was accepted for publication in Acta Biomaterialia. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Acta Biomaterialia, [VOL 6, ISSUE 8, (2010)] DOI: 10.1016/j.actbio.2010.01.04

Neurotoxins during the Renaissance. Bioarcheology of Ferrante II of Aragon (1469–1496) and Isabella of Aragon (1470–1524)

Abstract We show that statistical modeling of analytical results is useful in providing insights into metabolism and disease in bioarcheology. Our results also imply that during the Renaissance in Europe widespread pollution of the biosphere with heavy metals such as mercury and lead affected the Italian nobility at that time. The activity of biologic clocks which control metabolism and autonomic nervous system (ANS) function can be gleaned from the analysis of hair. This provides a means of assessing the health of individuals who lived some six centuries before the present and allows the reconstruction of disease from archived tissues such as hair

Macrochanneled Tetragonal Zirconia Polycrystals Coated by a Calcium Phosphate Layer

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65848/1/j.1151-2916.2003.tb03603.x.pd

Calcium carbonate-calcium phosphate mixed cement compositions for bone reconstruction

The feasibility of making calcium carbonate-calcium phosphate (CaCO3-CaP) mixed cements, comprising at least 40 % (w/w) CaCO3 in the dry powder ingredients, has been demonstrated. Several original cement compositions were obtained by mixing metastable crystalline calcium carbonate phases with metastable amorphous or crystalline calcium phosphate powders in aqueous medium. The cements set within at most 1 hour at 37°C in atmosphere saturated with water. The hardened cement is microporous and exhibits weak compressive strength. The setting reaction appeared to be essentially related to the formation of a highly carbonated nanocrystalline apatite phase by reaction of the mestastable CaP phase with part or almost all of the metastable CaCO3 phase. The recrystallization of metastable CaP varieties led to a final cement consisting of a highly carbonated poorly crystalline apatite (PCA) analogous to bone mineral associated with various amounts of vaterite and/or aragonite. The presence of controlled amounts of CaCO3 with a higher solubility than the apatite formed in the well-developed calcium phosphate cements might be of interest to increase resorption rates in biomedical cement and favor its replacement by bone tissue. Cytotoxicity testing revealed excellent cytocompatibility of CaCO3-CaP mixed cement compositions