Michael A. Stranick

Adsorption and dissolution behavior of human plasma fibronectin on thermally and chemically modified titanium dioxide particles.

Titanium is known for its biocompatibility and is widely used in dental and orthopedic reconstructive surgery. There are reports that osteointegration of these implants is not optimal. The objective of this study was to modify titanium dioxide particles and examine the resultant effects on protein adsorption to these altered surfaces using a model cell binding protein, human plasma fibronectin (HPF). HPF is an important matrix glycoprotein that plays a major role in cell and protein attachment, Titanium dioxide surfaces were modified by heating the titanium dioxide powder at 800 degrees C for 1 h or treating with an oxidizing agent: peroxide in ammonium hydroxide followed by peroxide in hydrochloric acid. Oxidized and control samples were further treated with 9:1 butanol:water for 30 min. Brunauer-Emmett-Teller showed no change in particle surface area as a result of thermal or chemical treatment. Hydrophobicity increased with butanol treatment of titanium dioxide. Diffuse reflectance Fourier transform infrared spectroscopy showed the presence of -CH2 and -CH3 vibrations in the region of 2850-3000 cm(-1) for both the heated, butanol and peroxide/butanol-treated samples. The absence of increased C-O and O-C=O features as determined by electron spectroscopy for chemical analysis indicates that butanol adsorption is not occurring via an esterification mechanism. The interaction between butanol and pre-heated or peroxide-treated titanium dioxide may be one of association (weak electrostatic and/or Van der Waals forces) rather than direct ionic bonding. Maximum HPF adsorption on modified or unmodified titanium dioxide occurred within 30 min, with greater protein adsorption occurring on butanol-treated samples. Desorption was minimal with all modifications. Zeta potential measurements showed that HPF adsorption caused an increase in the negative zeta potential with the greatest change noted for the butanol-treated samples. These findings suggest that wettability and surface charge both play an important role in protein adsorption to titanium dioxide. Thus, by modifying the physico-chemical properties of titanium dioxide surfaces, it may be possible to alter protein adsorption and hence optimize cell attachment.

Physicochemical study of plasma-sprayed hydroxyapatite-coated implants in humans

This study represents the first report of the physical and chemical changes occurring in coatings of failed hydroxyapatite (HA)-coated titanium implants obtained from a comprehensive, multicenter human dental implant study. A total of 53 retrieved samples were obtained and compared with unimplanted controls with the same manufacturer and similar manufacture dates. Forty-five retrieved implants were examined for surface characteristics and bulk composition. Implants were staged based on implantation history: stage 1 (implants retrieved between surgical placement and surgical uncovering), stage 2 (implants retrieved at surgical uncovering and evaluation), stage 3 (implants retrieved between surgical uncovering evaluation and occlusal loading), and stage 4 (implants retrieved after occlusal loading). Scanning electron microscopy showed progressive coating thinning with implantation time. At later stages, bare Ti metal was detected by energy-dispersive X-ray analysis and electron spectroscopy for chemical analysis. Increases in Ti and Al (2-7.5 atm % each) were detected at the apical ends of all stage 4 samples. In unimplanted coatings, X-ray diffraction analysis demonstrated the presence of amorphous calcium phosphate, beta-tricalcium phosphate, tetracalcium phosphate, and calcium oxide in addition to large hydroxyapatite crystals (c axis size, D002 = 429 +/- 13 A; a axis size, D300 = 402 +/- 11 A, a/c aspect ratio 0.92). The nonapatitic phases disappeared with increased implantation time, although there was a persistence of amorphous calcium phosphate. Bulk coating chemical analysis showed that Ca/P ratios for implant controls (1.81 +/- 0.01) were greater than stoichiometric HA (1.67) and decreased for implant stages 3 and 4 (1.69 +/- 0.09 and 1.67 +/- 0.09, respectively), explained by the dissolution of the non apatitic phases. Crystal sizes also changed with implantation times, being smaller than the control at all but stage 4. Fourier transform infrared analyses agreed with these results, and also indicated the accumulation of bone (protein and carbonate-apatite) in the retrieved coatings. The accumulation of bone was not stage dependent. These findings indicate that there was some biointegration with the surrounding bone, but the greatest changes occurred with the HA coating materials, their loss, and chemical change.

Influence of strontium on monofluorophosphate uptake by hydroxyapatite XPS characterization of the hydroxyapatite surface

Abstract The influence of Sr2+ on fluoride uptake from monofluorophosphate (MFP) solutions by hydroxyapatite (HAp) has been investigated using adsorption measurements and X-ray photoelectron spectroscopy (XPS). XPS analysis of Sr2+/MFP treated HAp powders indicates that a stoichiometric Sr2+/Ca2+ cation exchange occurs on the HAp surface. Complete exchange of surface Ca2+ occurs at Sr2+ concentrations >0.02 mol dm−3 forming a Sr HAp layer. Fluoride adsorption measurements reveal an increase in fluoride uptake with increasing Sr2+ concentration in the treatment solution. XPS data also show that fluorapatite (FAp) formation increases with increasing Sr2+ concentration and that a linear correlation exists between FAp formation and surface Sr2+. The data further suggest the formation of MFP-like particles or precipitates on the HAp surface.

Mode of action studies of a new desensitizing mouthwash containing 0.8% arginine, PVM/MA copolymer, pyrophosphates, and 0.05% sodium fluoride

OBJECTIVE The mode of action of an arginine mouthwash using the Pro-Argin™ Mouthwash Technology, containing 0.8% arginine, PVM/MA copolymer, pyrophosphates and 0.05% sodium fluoride, has been proposed and confirmed as occlusion using a variety of in vitro techniques. METHODS Quantitative and qualitative laboratory techniques were employed to investigate the mode of action of the new arginine mouthwash. Confocal laser scanning microscopy (CSLM) and atomic force microscopy (AFM) investigated a hydrated layer on dentine surface. Electron spectroscopy for chemical analysis (ESCA), secondary ion mass spectroscopy (SIMS) and near-infrared spectroscopy (NIR) provided information about its chemical nature. RESULTS CLSM was used to observe the formation of a hydrated layer on exposed dentine tubules upon application of the arginine mouthwash. Fluorescence studies confirmed penetration of the hydrated layer in the inner walls of the dentinal tubules. The AFM investigation confirmed the affinity of the arginine mouthwash for the dentine surface, supporting its adhesive nature. NIR showed the deposition of arginine after several mouthwash applications, and ESCA/SIMS detected the presence of phosphate groups and organic acid groups, indicating the deposition of copolymer and pyrophosphates along with arginine. CONCLUSION The studies presented in this paper support occlusion of the dentine surface upon the deposition of an arginine-rich layer together with copolymer and phosphate ions from an alcohol-free mouthwash containing 0.8% arginine, PVM/MA copolymer, pyrophosphates and 0.05% sodium fluoride.

Facile Preparation of Ultrafine Aluminum Hydroxide Particles with or without Mesoporous MCM-41 in Ambient Environments

An aqueous suspension of nanogibbsite was synthesized via the titration of aluminum aqua acid [Al(H2O)6]3+ with L-arginine to pH 4.6. Since the hydrolysis of aqueous aluminum salts is known to produce a wide array of products with a wide range of size distributions, a variety of state-of-the-art instruments (i.e., 27Al/1H NMR, FTIR, ICP-OES, TEM-EDX, XPS, XRD, and BET) were used to characterize the synthesis products and identification of byproducts. The product, which was comprised of nanoparticles (10-30 nm), was isolated using gel permeation chromatography (GPC) column technique. Fourier transform infrared (FTIR) spectroscopy and powder X-ray diffraction (PXRD) identified the purified material as the gibbsite polymorph of aluminum hydroxide. The addition of inorganic salts (e.g., NaCl) induced electrostatic destabilization of the suspension, thereby agglomerating the nanoparticles to yield Al(OH)3 precipitate with large particle sizes. By utilizing the novel synthetic method described here, Al(OH)3 was partially loaded inside the highly ordered mesoporous framework of MCM-41, with average pore dimensions of 2.7 nm, producing an aluminosilicate material with both octahedral and tetrahedral Al (Oh/Td = 1.4). The total Al content, measured using energy-dispersive X-ray spectrometry (EDX), was 11% w/w with a Si/Al molar ratio of 2.9. A comparison of bulk EDX with surface X-ray photoelectron spectroscopy (XPS) elemental analysis provided insight into the distribution of Al within the aluminosilicate material. Furthermore, a higher ratio of Si/Al was observed on the external surface (3.6) as compared to the bulk (2.9). Approximations of O/Al ratios suggest a higher concentration of Al(O)3 and Al(O)4 groups near the core and external surface, respectively. The newly developed synthesis of Al-MCM-41 yields a relatively high Al content while maintaining the integrity of the ordered silica framework and can be used for applications where hydrated or anhydrous Al2O3 nanoparticles are advantageous.