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

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

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

Calcified Algae for Tissue Engineering.

This book presents the latest advances in marine structures and related biomaterials for applications in both soft- and hard-tissue engineering, as well as controlled drug delivery

Interaction between a bisphosphonate, tiludronate, and biomimetic nanocrystalline apatites.

Bisphosphonates (BPs) are well established as successful antiresorptive agents for the prevention and treatment of bone diseases such as osteoporosis and Paget's disease. The aim of this work was to clarify the reaction mechanisms between a BP molecule, tiludronate, and the nanocrystalline apatite surface. The adsorption of tiludronate on well characterized synthetic biomimetic nanocrystalline apatites with homogeneous but different compositions and surface characteristics was investigated to determine the effect of the nanocrystalline apatite substrate on the adsorption behavior. The results show that the adsorption of tiludronate on nanocrystalline biomimetic apatite surfaces varies over a large range. The most immature apatitic samples exhibited the highest affinity and the greatest amount adsorbed at saturation. Maturation of the nanocrystals induces a decrease of these values. The amount of phosphate ion released per adsorbed BP molecule varied, depending on the nanocrystalline substrate considered. The adsorption mechanism, although associated with a release of phosphate ions, cannot be considered as a simple ion exchange process involving one or two phosphate ions on the surface. A two-step process is proposed consisting of a surface binding of BP groups to calcium ions associated with a proton release inducing the protonation of surface orthophosphate ions and their eventual solubilization