Apatite forming ability and cytocompatibility of pure and Zn-doped bioactive glasses.

The use of bone grafts permits the filling of a bone defect without risk of virus transmission. In this work, pure bioactive glass (46S6) and zinc-doped bioactive glass (46S6Zn10) with 0.1 wt% zinc are used to elaborate highly bioactive materials by melting and rapid quenching. Cylinders of both types of glasses were soaked in a simulated body fluid (SBF) solution with the aim of determining the effect of zinc addition as a trace element on the chemical reactivity and bioactivity of glass. Several physico-chemical characterization methods such as x-ray diffraction, Fourier transform infrared spectroscopy and nuclear magnetic resonance methods, with particular focus on the latter, were chosen to investigate the fine structural behaviour of pure and Zn-doped bioactive glasses as a function of the soaking time of immersion in SBF. Inductively coupled plasma-optical emission spectroscopy (ICP-OES) was used to measure the concentrations of Ca and P ions in the SBF solution after different durations of immersion. The effect of the investigated samples on the proliferation rate of human osteoblast cells was assessed by the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay, and tested on two different sizes of pure and zinc-doped glasses in powder form, with particle sizes that ranged between 40 to 63 µm and 500 to 600 µm. The obtained results showed the delay release of ions by Zn-doped glass (46S6Zn10) and the slower CaP deposition. Cytotoxicity and cell viability were affected by the particle size of the glass. The release rate of ions was found to influence the cell viability.

Aluminosilicates and biphasic HA-TCP composites: studies of properties for bony filling.

Aluminosilicate materials synthesized at room temperature present good mechanical properties. Hydroxyapatite, tricalcium phosphate or both offer a high biocompatibility in the biomedical field. In this work, we focused on the composites resulting from associations of these materials. The best compromise between porosity and biomechanical properties versus different parameters was determined. The in vitro behaviour of compounds in contact with the simulated body fluid (SBF) was studied and in vivo experiments in a rabbit's thighbones were carried out. The inductively coupled plasma-optical emission spectroscopy (ICP-OES) method permitted us to study the eventual release of Al from composites to SBF and to evaluate the chemical stability of composites characterized by the succession of SiO(4) and AlO(4) tetrahedra. The kinetic biomineralization, the bioconsolidation and biological studies were made. The results obtained show the chemical stability of composites. In the bone-implant interface, the intimate links reveal the high quality of the biointegration and the bioconsolidation between composites and bony matrix. Histological studies confirm good bony bonding and highlight the total absence of inflammation or fibrous tissues.

Comparison of the bony remodelling of two synthetic biomaterials: aragonite 55% and aragonite 55% with active substance.

In this work, the in vivo behaviour of pure aragonite and vectabone, which is an association of aragonite and an active substance such as gentamicin, was studied to highlight the kinetic resorption of these two biomaterials with 55% of porosity destined for the filling or replacement of bony defects. The synthesis conditions and parameters we used permit us to obtain a biomaterial without a sintering stage. These conditions allow introducing of active substances at the first stage of the elaboration. In this work, the gentamycin antibiotic was associated with calcium carbonate (aragonite 55% with gentamycin) to deliver this active substance on the surgical site for local treatment. The tricalcium phosphate biomaterial was used as the control because of its high biocompatibility. The bony remodelling of these three biomaterials was studied by in vivo experiments. This study was ensured with neutron activation analysis (NAA). The resorption kinetic was elaborated and comparisons of the remodelling biomaterials CaCO(3) 55% and CaCO(3) 55% with gentamicin (vectabone) and tricalcium phosphate were carried out. The obtained results show that, 6 months after implantation, the mineral composition of vectabone and tricalcium phosphate becomes close to that of young bone. Twelve months after implantation, it becomes similar to that of mature bone.

Antibiotic cements in articular prostheses: current orthopaedic concepts.

The possibilities and limits of antibiotic cements (ACs) have been assessed by many researchers. ACs are now approved by many drug agencies, including the US Food and Drug Administration (approval in 2003), with widespread use in prophylaxis and curative treatments. Laboratory experiments have achieved satisfactory antibiotic delivery without impairing the mechanical properties of ACs. Implantation in large animals (e.g. sheep) showed an antibiotic concentration in the bone cortex four times the minimal inhibitory concentration (MIC) 6 months after implantation. Human pharmacokinetics during total hip replacement (THR) show antibiotic concentrations 20 times the MIC in drainage fluids. No toxic concentrations have been detected in blood or urine, and no allergies, toxic effects, mechanical failures or selection of resistant microorganisms have been observed. Antibioprophylaxis has been assessed in prospective studies in over 1600 cases. In data from the Scandinavian arthroplasty registers, with an exhaustive follow-up of more than 240000 THRs, infection rate was reduced by ca. 50% (0.9% compared with 1.9%). In prostheses with severe infection, use of AC increases the infection control rate from 86% to 93% when using two-stage prosthetic exchanges. In moderate infection, a similar infection control rate (86%) was achieved either by two-stage exchange without local antibiotic or by one-stage exchange with AC; however, one-stage exchange achieved better functional results at lower cost and with reduced pain and hospital stay. Therefore, AC prophylaxis is widely used in countries with prostheses registers (Northern Europe), and use of ACs as treatment for infected prostheses is often considered as the gold standard in the EU and North America. However, AC is only an adjuvant treatment, and excision of infected and devascularized tissues as well as systemic antibiotic treatment managed by a multidisciplinary team remain the main factors of infection control.

Comparative study of two canal obturation techniques by image analysis and EDS microanalysis.

AIM: The aim of this in vitro study was to compare the marginal adaptation achieved by two obturation techniques (lateral condensation and Thermafil) using human teeth prepared by continuous rotation with the HERO 642(R) system. METHOD: The percentages of gaps and sealer on the root canal surface were determined by analysing the images of 12 sections per tooth. Tubule sealer penetration was assessed by backscattered scanning electron microscopy and energy dispersive spectrometry microanalysis. RESULTS: The Thermafil obturation technique resulted in virtually no gaps and very low amounts of sealer on the root surface, unlike the lateral condensation technique. Tubule sealer penetration occurred with both techniques, but was deeper, especially in the mid and apical zones, with the lateral condensation technique.

Characterisation and quantification of angiogenesis in beta-tricalcium phosphate implants by immunohistochemistry and transmission electron microscopy.

The aim of this study is the histological characterisation of angiogenesis in a macroporous biomaterial with quantification techniques used in oncology. Porous tricalcium phosphate implants were seated in the tibias of 12 rabbits. This work allows (1) morphological study with photonic microscopy, transmission electron microscopic and immunohistochemistry labelling for (2) quantification of vascularisation using anti-CD31 monoclonal antibody (3) quantification of proliferation using anti-PCNA polyclonal antibody (4) study of two angiogenic growth factors: VEGF and FGF-2. Quantification of angiogenesis revealed an outbreak kinetic with early vascular growth in first several days and a second growth phase after 4 weeks. This study reveals in macropores many isolated cells without adjacent vascular lumen, with endothelial phenotype. Expression of angiogenic growth factors reveals that all endothelial cells were VEGF-negative throughout the test period. FGF-2 expression by endothelial cells began 2 weeks post-implantation. Osteoblasts strongly expressed two markers throughout the test period. Furthermore, the procedure described here can be used to compare angiogenesis in different biomaterials or in the same biomaterial with the influence of macroporosities.

Impact of torsional and bending inertia on root canal instruments.

The laws of applied mechanics can be used to analyze and predict the behavior of mechanical parts subjected to strain and distortion, such as endodontic instruments. Simple mathematical formulas can be used to represent the impact of torsional and bending inertias on stresses in endodontic instruments being used in root canals. The boundary integral method was applied to two theoretical models with the same diameters but different cross-sections to evaluate quantitatively and qualitatively the stresses produced in orthogonal cross-sections. The results confirmed the mathematical deduction concerning the impact of torsional and bending stresses. The results indicate that clinical protocols based on the torsional and bending properties of endodontic instruments must be strictly followed, and endodontic instrument manufacturers must adopt standardized criteria for describing these properties.

The pharmacokinetics and pharmacodynamics of bupivacaine-loaded microspheres on a brachial plexus block model in sheep.

UNLABELLED: We evaluated bupivacaine-loaded microspheres (B-Ms) using a brachial plexus block model in sheep. In the first step, pharmacokinetic characterization of 75 mg bupivacaine hydrochloride (B-HCl) (IV infusion and brachial plexus block) was performed (n = 12). In the second step, a brachial plexus block dose response study of B-HCl was performed with 37.5 mg, 75 mg, 150 mg, 300 mg, and 750 mg. As a comparison, evaluations were performed using a 750-mg bupivacaine base (B). In the third step, evaluations of brachial plexus block were performed with B-Ms (750 mg of B as B-Ms) using two formulations, 60/40 and 50/50 (w/w %); drug-free microspheres were also evaluated. Toxicity evaluations were also performed after IV administration of B-HCl (750 mg and 300 mg), B-Ms (750 mg), and drug-free microspheres (30 mL over 1 min). As the B-HCl dose increased, the time of onset of block decreased and the duration of complete motor blockade increased at the expense of an increase in bupivacaine plasma concentrations. The time of maximum concentration appeared to be independent of the B-HCl dose. In brachial plexus block, a 37.5-mg dose of B-HCl did not induce motor blockade whereas a dose of 750 mg of B-HCl was clinically toxic. In the case of IV administration, doses of 300 mg of B-HCl were as toxic as 750 mg of B-HCl. Compared with the 75 mg of B-HCl administration for brachial plexus block, administration of 750 mg of B as B-Ms increased the duration of complete motor blockade without significant difference in maximum concentration. No significant clinical difference between the two formulations of B-Ms was demonstrated. The IV administration of B-Ms was safe. We conclude that the controlled release of bupivacaine from microspheres prolonged the brachial plexus block without obvious toxicity. IMPLICATIONS: Administration of 750 mg of bupivacaine as loaded-microspheres resulted in prolongation of brachial plexus block in sheep. The peak plasma concentration was not significantly larger than that obtained with 75 mg of plain bupivacaine. The motor blockade was increased more than six times compared with 75 mg plain bupivacaine.

Multicenter randomized evaluation of a nutritional education software in obese patients.

OBJECTIVE: To study the efficacy of the nutritional education software, Nutri-Expert, in the management of obese adult patients. MATERIAL AND METHODS: Two groups of obese patients were followed up over one year in a randomized study: the first group received close traditional management (seven nutritional visits over the year, with physicians and dietitians conjointly) and the second one also used at home by Minitel the Nutri-Expert system. 557 patients were enrolled in the study by 16 French centers of diabetology and nutrition. Body mass index (BMI), tests of dietetic knowledge, dietary records and centralized biological measurements were assessed at inclusion, 6 and 12 months. 341 patients were evaluable at the end of the year. RESULTS: The group using Nutri-Expert scored significantly better in the tests of dietetic knowledge than the control group. For all patients, nutritional education led to a significant improvement in BMI, dietary records and biological measurements, without significant difference between the two groups. Five years after the end of the study, the weight of 148 patients was recorded; mean BMI was significantly lower than the initial value but there was no significant difference between the two groups. CONCLUSION: In the management of obese patients, Nutri-Expert system has a role to play in reinforcing nutritional knowledge; if regular follow-up is not possible, or if a large series of obese patients is to be treated, Nutri-Expert could partly replace traditional management, for example between visits.

Integral method for numerical simulation of MRI artifacts induced by metallic implants.

Numerical simulation is a valuable tool for the study of magnetic susceptibility artifacts from metallic implants. A major difficulty in the simulation lies in the computation of the magnetic field induced by the metallic implant. A new method has been designed and implemented to compute the magnetic field induced by metallic objects of arbitrary shape. The magnetic field is expressed pointwise in terms of a surface integral. Efficient quadrature schemes are proposed to evaluate this integral. Finally, the method is linked to an artifact reconstruction model to simulate the images. Magn Reson Med 45:724-727, 2001.

Safety aspects and quality assessment in MRI and MRS: a challenge for health care systems in Europe.

Despite advances in international cooperation, the application of the safety regulations of different countries remains an important challenge for manufacturers and health care workers in the European Union. Rapid technological development during the last 20 years, and the still controversial nature of certain potential effects of magnetic or electromagnetic fields, make the task particularly difficult for MRI and MRS. As the relevant literature is rather extensive, the present work will limit its goals to four questions: 1) How is MRI and MRS safety regulation managed within the European Union? 2) Concerning direct potential physiological effects, what is presently well known and controlled, and, conversely, what are the remaining open (and often controversial) questions? 3) As metallic implants are probably the main risk in routine MRI, what regulatory strategy is in progress in Europe? 4) As indirect risks related to artifacts must not be underestimated, what European programs have been developed for quality assessment in MRI and MRS? In all of these fields, evidence is provided demonstrating the need for a mutual recognition of common standards for the European Union and the United States.

Nutrient intakes as predictors of body weight in European people with type 1 diabetes.

BACKGROUND: Overweight and obesity are also found among persons with type 1 diabetes. OBJECTIVE: The present study examined which nutrients predict the body mass index (BMI), the waist-to-hip ratio (WHR) and the waist circumference (WC) of European persons with type 1 diabetes. DESIGN: Cross-sectional, clinic-based study (EURODIAB Complications Study). SUBJECTS AND METHODS: Nutrient intakes (assessed by a 3-day dietary record) predicting measures of body weight (BMI, WHR and WC) were determined by stepwise forward regression analysis in 1458 males and 1410 females with type 1 diabetes (P< or =0.05 for inclusion). RESULTS: In men, a higher carbohydrate intake was a significant independent predictor for lower levels of BMI, WHR and WC, an increased saturated fat intake and a lower intake of cereal fibre predicted a higher WHR, a higher monounsaturated fat intake and a lower glycaemic index of the diet determined lower levels of WHR and WC, and a moderate consumption of alcohol determined an increased WC. In women, a higher carbohydrate intake predicted a lower BMI and a thinner WC, no alcohol consumption determined a lower BMI, and an increased intake of saturated fat and a lower consumption of cereal fibre were significant independent predictors for a higher WHR. CONCLUSIONS: A modified fat intake, an increase of carbohydrate and cereal fibre intake and a preferred consumption of low glycaemic index foods are independently related to lower measures of body weight in European persons with type 1 diabetes.

[Influence of the bonding interface on bracket adhesion]. / Influence des interfaces de collage sur l'adhésion des brackets.

Adhesion strength may be explained by different theories that allow a better understanding and a better use of orthodontic adhesives. Transmission (TEM) and scanning (SEM) electron microscopy analysis of debonding areas allows to differentiate the location of bonding fractures and the consequences on enamel. Such a knowledge may be useful when choosing the most adapted protocol.

[Changes in the enamel after in vitro debonding of brackets bonded with a modified glass ionomer cement]. / Altérations de l'émail après décollement in vitro d'attaches collées au verre ionomère modifié.

The aim of this study was to assess the incidence on the enamel behavior of debonding two types of orthodontic brackets, bonded with two different adhesives. Ninety recently extracted human premolars were bonded with two types of brackets (30 Minitrim and 60 Discovery). Two bonding protocols were used. The first one consisted in bonding 30 Minitrim and 30 Discovery brackets on etched and dried enamel surfaces with No Mix orthodontic resin. The second one consisted in bonding 30 Discovery brackets on unetched and wet enamel surfaces with a modified glass ionomer cement, Fuji Ortho LC. Teeth were stored in hydrated ambiance at 37 degrees C for 7 days before debonding. A LLOYD (LR 30K) testing machine was used to evaluate the orthogonal tensile bond strength. The debonded base brackets were examined with a scanning electron microscope (JEOL JSM 6400) and qualitatively analyzed with an OXFORD-LINK-ISIS to assess the site of bond failure and the enamel detachments. An Enamel Detachment Index (EDI) was defined. The results showed that the types of orthodontics brackets and adhesives influenced the bond strength and the enamel detachment. The Discovery/No Mix couple presented higher bond strength (214.9 N) than observed with the Discovery/Fuji Ortho LC (98.5 N) or the Minitrim/No Mix (82.3 N) couples. The surfaces of enamel detachment were insignificant and not extended for all brackets. Nevertheless, the Discovery/No Mix couple presented 42% of an EDI score of 1, compared to the Discovery/Fuji Ortho LC and Minitrim/No Mix couples which presented, respectively, 8% an 20% of an EDI score of 1. The laser sculpted base (Discovery) bonded on unetched and wet enamel surfaces with the modified glass ionomer cement (Fuji Ortho LC) offers a good resistance to debonding forces and preserve enamel integrity.

Effects of a single bout of exercise and exercise training on steroid levels in middle-aged type 2 diabetic men: relationship to abdominal adipose tissue distribution and metabolic status.

Lower androgen levels have been suggested to be associated with type 2 diabetes and central obesity and are probably involved into the development of atherosclerosis. The present study investigates the effect of acute and chronic exercise on Dehydroepiandrosterone (DHEA) levels in relation to abdominal fat distribution and metabolic status in type 2 diabetes. Twenty weight-stable, middle-aged males with type 2 diabetes were enrolled in the study and participated in a submaximal (VO(2) peak) and moderate (50% VO(2) peak) exercise bout. The subjects were randomly assigned either to a trained or a control group, respectively. Physical training consisted of an 8 week program of aerobic exercise (75% VO(2) peak, 45 min), twice a week and intermittent exercise, once a week, on a bicycle ergometer. Acute exercise significantly increased DHEA and Testosterone (T) levels. Physical training increased VO(2) peak (42%, p <0.001), insulin sensitivity index (K(ITT) ) (57.5%, p <0.02), and basal DHEA levels (36%, p <0.05), and decreased HbA1c (29%, p <0.001), visceral adipose tissue (VAT) (44%, p <0.01) and subcutaneous adipose tissue (SAT) levels (18%, p <0.01). Body weight, BMI and insulin, T levels were not modified. Changes in DHEA levels were not correlated with changes in insulin sensitivity and abdominal fat distribution. In conclusion, exercise training favourably affects DHEA levels independently of improvements of metabolic status and abdominal fat distribution in patients with type 2 diabetes.

Low prevalence of long-term complications in non-insulin-dependent diabetes mellitus in France: a multicenter study. CODIAB-INSERM-ZENECA Pharma Study Group.

The aim of this study was to assess the prevalence of long-term complications in a large sample of French NIDDM patients. Therefore, 427 NIDDM patients 35-74 years old were recruited in ten centers. Standardized clinical criteria and central reading for retinal and electrocardiographic changes were used to assess the presence of complications. The prevalence rates of complications were 29.7% and 3.3% for background and proliferative retinopathy; 21.8%, 6.1%, and 2.8% for microalbuminuria, proteinuria, and renal insufficiency; 19.9 and 11.7% for asymptomatic and symptomatic pheripheral neuropathy; 8.2% for orthostatic hypotension; 10.1% and 8.4% for angina pectoris and myocardial infarction; and 13.1% and 6.3% for mild and moderate to severe peripheral vascular disease, respectively. In conclusion, prevalence rates in this study were lower than in most studies from other countries.

Evaluation of abdominal fat distribution in noninsulin-dependent diabetes mellitus: relationship to insulin resistance.

Accumulation of visceral adipose tissue is associated with metabolic complications such as noninsulin-dependent diabetes mellitus. The aim of this study was to evaluate the effect of abdominal adipose tissue on insulin sensitivity in subjects with noninsulin-dependent diabetes mellitus (NIDDM). Areas of abdominal fat were calculated from axial magnetic resonance images obtained at the level of the umbilicus in 21 men with NIDDM [age, 45.6 +/- 8.3 (+/-SD) yr; body mass index, 29.3 +/- 4.5 kg/m(-2); total body fat (skinfold thickness), 26.8 +/- 5.4%; waist to hip ratio, 0.97 +/- 0.07; duration of diabetes, 59 +/- 47 months; hemoglobin A1c, 8.1 +/- 1.5%]. Insulin sensitivity was evaluated by an insulin tolerance test. The areas of deep abdominal fat and sc abdominal fat were, respectively, 135.3 +/- 55.1 and 211.8 +/- 99.1 cm2. The blood glucose disappearance rate was 2.11 +/- 0.87%/min and was negatively related to deep abdominal fat (r = 0.72; P = 0.0025). In contrast, areas of sc abdominal fat, total body fat, body mass index, and waist to hip ratio were not related to the blood glucose disappearance rate. Plasma triglyceride concentrations averaged 1.8 +/- 0.8 mmol/L and were positively related to deep abdominal fat (r = 0.69; P = 0.0018). We conclude that insulin sensitivity is strongly related to visceral adipose tissue accumulation in NIDDM.