The role of new zinc incorporated monetite cements on osteogenic differentiation of human mesenchymal stem cells.

ß-Tricalcium phosphate particles were sintered in the presence of different amounts (0-0.72mol) of zinc oxide (ZnO) to prepare zinc doped ß-TCP (Znß-TCP) particles for further use in novel monetite (DCPA: CaHPO4) zinc incorporated bone cements with osteogenic differentiation potential towards human mesenchymal stem cells (hMSCs). XRD analysis of zinc incorporated cements prepared with ß-TCP reagent particles doped with different amount of ZnO (i.e. 0.03, 0.09 and 0.18mol ZnO) revealed the presence of unreacted Znß-TCP and monetite. Furthermore, it was shown that zinc ions preferentially occupied the ß-TCP crystal lattice rather than the monetite one. Release experiments indicated a burst release of ions from the different fabricated cements during the first 24h of immersion with zinc concentrations ranging between 85 and 100% of the total concentration released over a period of 21days. Cell proliferation significantly increased (P<0.05) on zinc incorporated monetite respect to control samples (Zinc-free cement) at 7 and 14days post seeding. The expression of Runx-2 was significantly up regulated (P<0.05) in the case of cells seeded on monetite prepared with ß-TCP doped with 0.03 moles of ZnO. On the other hand, the cell mineralization as well as the expression of osteogenic marker genes ALP and OSC decreased significantly (P<0.05) at 14days post cell seeding. In conclusion, these results suggest that the zinc ions released from the cements during the first 24h of culture played a critical role in regulating the osteogenic differentiation of hMSCs.

Effects of Composites Containing Bioactive Glasses on Demineralized Dentin.

The aim of this study was to evaluate the degradation of completely demineralized dentin specimens in contact with a filler-free or 2 ion-releasing resins containing micrometer-sized particles of Bioglass 45S5 (BAG) or fluoride-containing phosphate-rich bioactive glass (BAG-F). Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were also used to evaluate the remineralization induced by the experimental ion-releasing resin-based materials. Dentin beams were totally demineralized in H3PO4 (10%) and placed in direct contact with a filler-free (RESIN) or 2 experimental ion-releasing resins (BAG or BAG-F) and immersed in artificial saliva (AS) up to 30 d. Further specimens were also processed and submitted to FTIR and SEM analysis to evaluate the remineralization induced by such ion-releasing resins before and after AS immersion. BAG and BAG-F alkalinized the incubation media. A significant decrease of the dry mass was observed between the specimens of all groups stored for 3 and 30 d in AS. However, the fluoride-containing phosphate-rich bioactive glass incorporated into a resin-based material (BAG-F) showed greater ability in reducing the solubilization of C-terminal cross-linked telopeptide (ICTP) and C-terminal telopeptide (CTX) after prolonged AS storage. Moreover, after 30 d of AS storage, BAG-F showed the greatest remineralizing effect on the stiffness of the completely demineralized dentin matrices. In conclusion, fluoride-containing phosphate-rich bioactive glass incorporated as micrometer-sized filler in dental composites may offer greater beneficial effects than Bioglass 45S5 in reducing the enzyme-mediated degradation and remineralization of demineralized dentin.

Structural changes and biological responsiveness of an injectable and mouldable monetite bone graft generated by a facile synthetic method.

Brushite (dicalcium phosphate dihydrate) and monetite (dicalcium phosphate anhydrous) are of considerable interest in bone augmentation owing to their metastable nature in physiological fluids. The anhydrous form of brushite, namely monetite, has a finer microstructure with higher surface area, strength and bioresorbability, which does not transform to the poorly resorbable hydroxyapatite, thus making it a viable alternative for use as a scaffold for engineering of bone tissue. We recently reported the formation of monetite cements by a simple processing route without the need of hydrothermal treatment by using a high concentration of sodium chloride in the reaction mix of ß-tricalcium phosphate and monocalcium phosphate monohydrate. In this paper, we report the biological responsiveness of monetite formed by this method. The in vitro behaviour of monetite after interaction and ageing both in an acellular and cellular environment showed that the crystalline phase of monetite was retained over three weeks as evidenced from X-ray diffraction measurements. The crystal size and morphology also remained unaltered after ageing in different media. Human osteoblast cells seeded on monetite showed the ability of the cells to proliferate and express genes associated with osteoblast maturation and mineralization. Furthermore, the results showed that monetite could stimulate osteoblasts to undergo osteogenesis and accelerate osteoblast maturation earlier than cells cultured on hydroxyapatite scaffolds of similar porosity. Osteoblasts cultured on monetite cement also showed higher expression of osteocalcin, which is an indicator of the maturation stages of osteoblastogenesis and is associated with matrix mineralization and bone forming activity of osteoblasts. Thus, this new method of fabricating porous monetite can be safely used for generating three-dimensional bone graft constructs.

Can the hydrophilicity of functional monomers affect chemical interaction?

The number of carbon atoms and/or ester/polyether groups in spacer chains may influence the interaction of functional monomers with calcium and dentin. The present study assessed the chemical interaction and bond strength of 5 standard-synthesized phosphoric-acid ester functional monomers with different spacer chain characteristics, by atomic absorption spectroscopy (AAS), ATR-FTIR, thin-film x-ray diffraction (TF-XRD), scanning electron microscopy (SEM), and microtensile bond strength (µTBS). The tested functional monomers were 2-MEP (two-carbon spacer chain), 10-MDP (10-carbon), 12-MDDP (12-carbon), MTEP (more hydrophilic polyether spacer chain), and CAP-P (intermediate hydrophilicity ester spacer). The intensity of monomer-calcium salt formation measured by AAS differed in the order of 12-MDDP=10-MDP>CAP-P>MTEP>2-MEP. FTIR and SEM analyses of monomer-treated dentin surfaces showed resistance to rinsing for all monomer-dentin bonds, except with 2-MEP. TF-XRD confirmed the weaker interaction of 2-MEP. Highest µTBS was observed for 12-MDDP and 10-MDP. A shorter spacer chain (2-MEP) of phosphate functional monomers induced formation of unstable monomer-calcium salts, and lower chemical interaction and dentin bond strength. The presence of ester or ether groups within longer spacer carbon chains (CAP-P and MTEP) may affect the hydrophilicity, µTBS, and also the formation of monomer-calcium salts.

Accuracy of CBCT for volumetric measurement of simulated periapical lesions.

AIM: To compare the accuracy of cone beam computed tomography (CBCT) and micro-computed tomography (µCT) when measuring the volume of bone cavities. METHODOLOGY: Ten irregular-shaped cavities of varying dimensions were created in bovine bone specimens using a rotary diamond bur. The samples were then scanned using the Accuitomo 3D CBCT scanner. The scanned information was converted to the Digital Imaging and Communication in Medicine (DICOM) format ready for analysis. Once formatted, 10 trained and calibrated examiners segmented the scans and measured the volumes of the lesions. Intra/interexaminer agreement was assessed by each examiner re-segmenting each scan after a 2-week interval. Micro-CT scans were analysed by a single examiner. To achieve a physical reading of the artificially created cavities, replicas were created using dimensionally stable silicone impression material. After measuring the mass of each impression sample, the volume was calculated by dividing the mass of each sample by the density of the set impression material. Further corroboration of these measurements was obtained by employing Archimedes' principle to measure the volume of each impression sample. Intraclass correlation was used to assess agreement. RESULTS: Both CBCT (mean volume: 175.9 mm3) and µCT (mean volume: 163.1 mm3) showed a high degree of agreement (intraclass correlation coefficient >0.9) when compared to both weighed and 'Archimedes' principle' measurements (mean volume: 177.7 and 182.6 mm3, respectively). CONCLUSION: Cone beam computed tomography is an accurate means of measuring volume of artificially created bone cavities in an ex vivo model. This may provide a valuable tool for monitoring the healing rate of apical periodontitis; further investigations are warranted.

A novel method of forming micro- and macroporous monetite cements.

Second to autologous bone grafts are the calcium phosphate cements (CPCs) used as synthetic bone substitutes due to their chemical similarity to the mineral component of bone. Their ability to conform to complex bone defects and excellent osteoconductivity also render them excellent scaffolds for bone tissue engineering, although they do have their own limitations. Calcium phosphates can be divided into two main categories, namely apatite and brushite. Apatites exhibit low solubility, whereas, calcium phosphates that set to form brushite, are metastable, which degrade rapidly, but do subsequently form hydroxyapatite that retards the rate. In contrast dicalcium phosphate anhydrous (monetite) has a higher solubility than octacalcium phosphate and does not transform to an apatite; thus, it is able to continue to degrade with time. Herein, a new method was used via the addition of sodium chloride to ß-tricalcium phosphate and monocalcium phosphate monohydrate to form micro- and macroporous monetite (DCPA). The X-ray diffraction and FTIR spectra confirmed the formation of monetite in the presence of both, 6.2 M NaCl solution or 60% of solid sodium chloride. The maximum compressive strength (σc = 12.3 ± 1.8 MPa) and the Young's modulus (E = 1.0 ± 0.1 GPa) of the monetite cements obtained were comparable to the upper limits of the values reported for cancellous bone and also higher than that reported by other routes used to form monetite. The porous cements analysed by microCT revealed an interconnected porosity with the preliminary in vitro biological evaluation indicating favourable osteoblast cell attachment and growth.

Preparation and properties of macroporous brushite bone cements.

In the present work a macroporous brushite bone cement for use either as an injected or mouldable paste, or in the shape of preformed grafts, has been investigated. Macropores have been introduced by adding to the powder single crystals of mannitol which worked as a porogen. The size of the crystals was in the range of 250-500microm in diameter, suitable for cell infiltration, with a shape ratio between 3 and 6. From compression tests on cylindrical samples an elastic modulus in the range 2.5-4.2GPa and a compressive strength in the range 17.5-32.6MPa were obtained for a volume fraction of macropores varying between 15 and 0%. Thus the compressive strength exceeded in all tests the maximum value currently attributed to cancellous bone.

Heart rate, alveolar gases and blood lactate during synchronized swimming.

Heart rate, alveolar gas partial pressures and blood lactate (BLa) concentration were measured during synchronized swimming in six subjects. During upside-down breath-holding lasting 50 s, heart rate fell progressively from 98 +/- 14 to 70 +/- 7 beats min-1 (mean +/- S.D.). While breath-holding during the compulsory figures, the subjects' heart rate increased to 142 +/- 5 beats min-1 and then fell to 72 +/- 10 beats min-1. At the end of breath-holding, alveolar oxygen pressure had fallen significantly (60 mmHg), whereas alveolar carbon dioxide pressure showed only minor changes (48 mmHg). The increase in BLa concentration due to the execution of compulsory figures was approximately 1 mM; in the free routines, BLa concentration increased by 3.4 +/- 0.5 mM. The net energy cost of completing a compulsory figures lasting 45 s was 34.6 kJ.

Force and power of preferred and non-preferred leg in young soccer players.

The purpose of this study was to assess the effects of soccer training on strength and power of leg extensor muscles in preadolescent boys and their possible influence in developing a muscular lateral dominance. Twenty male children (mean age 9.6 yr), ten soccer players and ten untrained subjects, participated in this study. Force and power were measured at five constant cranking velocities on an isokinetic bicycle dinamometer. Each isokinetic load was given after each trial. Force and power outputs were calculated for each limb. Soccer players always showed higher and statistically significant differences (p < 0.05) for force and power values for all considered pedal frequencies. No significant differences were observed for force and power values between preferred and non preferred limb. The results demonstrate the effect of soccer training on the increase of force and power of both legs regardless of lateral dominance.

Assessment of static balance in children.

The ability in maintaining body balance of 6-, 8-, and 10-year-old children performing three balance tests on a force platform was studied. Thirty adult subjects served as a reference group. The mean radius (MR) of the posturogram and the mean speed (MS) of the center of foot pressure (COP) were used as the measuring parameters. Data were analyzed using two-way ANOVA, the Sheffe test and the Student "t" test with a .05 level of significance. A decrease with age in both mean radius and mean speed, indicating an increase in balance ability, was noted. A significant age main effect was found on all tests while significant gender main effect occurred only on the Tandem test. No significant age/sex interaction was found. Significant differences between the 10-year-old and adult groups occurred only in the more difficult balance tests.

Radioactivity in breast milk and placentas during the year after Chernobyl.

After the April 1986 nuclear reactor accident at Chernobyl in the Union of Soviet Socialist Republics, samples of human placenta and breast milk were tested for 1 year to determine the levels of radioactivity. The radionuclide iodine 131 was never beyond the detection limit of our gamma detector for both matrices. As to cesium isotopes 134 and 137, the highest levels detected in breast milk (6 Bq.L-1) and placenta (15.8 Bq.kg-1) were recorded in March 1987. Study data for breast milk and placenta are in agreement with the values calculated by means of double-compartment food-milk and food-placenta models. With regard to placental content, the cesium contribution to the average dose during the year after the Chernobyl accident was calculated to be 40 to 60 microSv.