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Biomedical subjects

M Ferrari

Publications and source records attributed to M Ferrari.

At least 199 records · Page 11Linked to original sources
PubMed1999

Standardized microscopic evaluation of the bonding mechanism of NRC/Prime & Bond NT.

PURPOSE: To investigate the in vitro formation of hybrid layer, resin tags and adhesive lateral branches, when using Prime & Bond NT (PBNT) "one-bottle" enamel-dentin bonding system on conditioned and unconditioned human dental substrates. MATERIALS AND METHODS: The enamel dentin adhesive was tested on 18 dentin and 18 enamel flat preparations made on facial and occlusal surfaces, respectively, of extracted posterior teeth. Each experimental tooth substrates were randomly divided in six groups of six samples each: Group 1: PBNT on conditioned dentin (CD) with 36% phosphoric acid (PA), Group 2: PBNT on etched enamel (EE) with 36% PA, Group 3: PBNT on CD with NRC non-rinse conditioning (NRC); Group 4: PBNT on EE with NRC, Group 5: PBNT on dentin without any conditioning (UD), Group 6: PBNT on enamel without any conditioning (UE). In the experimental groups, PBNT was applied following the manufacturer's instructions. Over the PBNT, a layer of Dyract AP was placed and light-cured for 20 seconds. All samples were split-fractured along their long axis. One half of each sample was deproteinized and decalcified at the interface in order to visualize the hybrid layer and the other was completely dissolved in order to observe the morphology of resin tags with a scanning electron microscope. RESULTS: Groups 1, 2: The tested samples showed a micromechanical bonding mechanism to CD and EE with phosphoric acid. PBNT formed hybrid layer, resin tags and adhesive lateral branches on dentin. In the dentin samples of the first group, characteristic reverse cone-shaped tags with their corresponding adhesive lateral branches were evident. At the enamel site, traditional pattern of etch enamel was always observed with resin tags formation. Groups 3, 4: When the bonding system was applied on dentin conditioned with NRC, a thin hybrid layer was formed, resin tags were also noted but their shape was narrower than that observed in Group 1. At the enamel site, the conditioned surface showed presence of an etched pattern and of resin tags. Groups 5, 6: When PBNT was applied without any previous conditioning, the hybrid layer and resin tags formation were not evident on dentin, and no bonding mechanism was developed with unetched enamel.

Acid Etching, Dental↗
PubMed1999

Clinical evaluation of a one-bottle bonding system for desensitizing exposed roots.

PURPOSE: To evaluate the effectiveness of a one-bottle adhesive system as a desensitizing treatment, with or without a prior phosphoric acid-etch step. MATERIALS AND METHODS: Two different clinical procedures using a one-bottle adhesive bonding system were tested for its efficacy on desensitizing exposed roots. Thirty subjects with a history of dentin hypersensitivity were selected and 60 exposed sensitive teeth were divided into two groups (n = 30). In Group 1 samples, Scotchbond 1 bonding system (Single Bond in USA) was applied without a prior acid-etching, while in those of Group 2, the exposed sensitive roots were acid-etched with 35% phosphoric acid for 15 seconds, prior to application of bonding agents. The sensitivity was evaluated at 0, 1, 2, 4 weeks and 3 months using cold air blast stimuli, and recorded using a visual-analogue scale. The scores were analyzed as non-parametric data by means of the Mann-Whitney and Sign tests. Five samples from each group were randomly selected in order to make scanning electron microscope observations of the sensitive dentin surfaces at baseline and at each recall using the replica technique. RESULTS: At baseline, after both desensitizing procedures all the patients reported distinct reductions in dentin sensitivity. At 1- and 2-week recalls, 20 teeth of Group 1 and 17 teeth in Group 2 exhibited a return of sensitivity, and in five teeth in each group, the sensitivity score was between 5-8. During the first recall (1-2 weeks), the sensitive teeth were retreated and showed an immediate reduction of sensitivity. At the 1-month recall, eight teeth in Group 1 and four teeth in Group 2 showed a return of some sensitivity, and in six teeth in Group 1 and in three teeth in Group 2, old amalgam restorations were replaced and this procedure almost completely resolved the sensitivity. At the 3-month recall, only five teeth from each group showed residual mild sensitivity (score 1-2). For both Groups 1 and 2 there was a statistically significant (P < 0.0005) reduction in sensitivity levels between the baseline pain scores and immediately after treatment, and between the first recall pre-treatment pain scores and the last recall pain scores. Overall, the two methods of treatment demonstrated a general decrease in sensitivity in both groups over the 3-month study period, adequately solving the clinical and patients' perception of the discomfort of sensitivity. The SEM observations of the replicas showed a progressive loss of the adhesive resin from the treated surfaces. This fact was more evident in the non-etched samples (Group 2) than in those in Group 1. The results of this study showed that exposed root dentin sealed with Scotchbond 1, with or without prior acid-etching, did not show spontaneous sensitivity after 3 months.

Acid Etching, Dental↗
PubMed1999

Influence of tissue characteristics at margins on leakage of Class II indirect porcelain restorations.

PURPOSE: To evaluate the sealing ability of Class II porcelain inlays with margins placed in cementum-dentin and enamel, luted by two new different cementing materials. MATERIALS AND METHODS: Thirty extracted molars, free from caries and restorations, were selected. The sample cavities were prepared in a standardized manner and then were divided in three groups (n = 10) at random. Group 1: The cervical margin was located 1 mm below the CEJ and the inlays were luted with EBS Multi (Espe) bonding system in combination with Compolute 1.0 Aplicap (CLA 1.0, Espe) experimental resin cement. Group 2: The cervical margin was placed 1 mm below the CEJ and Syntac bonding system (Vivadent) and Variolink II resin cement (Vivadent) were used. Group 3: The cervical margin was placed 0.5 mm above the CEJ and the same materials selected for Group 1 were used. IPS-Empress (Ivoclar) inlays were made following manufacturer's instructions. After luting procedures and 2500 thermal cycles (5 degrees and 55 degrees C), the samples were processed and evaluated for marginal leakage at cervical and occlusal site. Samples of Group 3 were first sectioned in the center of the restorations as in Group 1 and 2 and scored (Group 3A) and then two other cuts were made along the buccal and lingual areas (Group 3B) and also scored. After scoring dye penetration of Group 1 and 2 samples, half of the sections were randomly selected to evaluate: (1) resin cement thickness, (2) Hybrid layer formation at the interface between adhesive material and dental substrate and (3) to observe the morphology of the Class II cavity margins. The leakage data were statistically evaluated with the Mann-Whitney U test (P < 0.5). RESULTS: Statistically significant differences were found between Groups 3A and 3B at the occlusal site, and not at the cervical site. Samples of Group 1 showed a cement thickness of 92 microns, and 68 microns in Group 2. Hybrid layer and resin tag formation was evident in Group 1. In Group 2 samples, the hybrid layer formation was less evident and thinner than in Group 1. At cervical margins, an outer layer, not identifiable as sound dentin, of 200-300 microns thick, was noted. This layer was present in all three groups between outer margin and sound dentin. The margins located both cervically and axially in enamel mainly showed prisms cut along their long axis and a low level of structured etch pattern.

Aged↗
PubMed1999

In vitro leakage of resin-bonded all-porcelain crowns.

PURPOSE: The purpose of this study was to evaluate the sealing ability of single-unit all-porcelain crowns with margins placed in cementum-dentin and luted with two different cementing materials. MATERIALS AND METHODS: Twenty extracted molars, free of caries and restorations, were selected. The sample abutments were prepared in a standardized manner and then divided in two groups (n = 10) at random. Group 1: The cervical margin was located 1 mm below the CEJ and the crowns were luted with EBS Multi (Espe) bonding system in combination with Compolute 1.0 Aplicap (CLA 1.0, Espe) experimental resin cement. Group 2: The cervical margin was placed 1 mm below the CEJ, and Syntac bonding system (Vivadent) and Variolink II resin cement (Vivadent) were used. IPS-Empress (Ivoclar) crowns were made following manufacturer's instructions. After luting procedures and 2,500 thermal cycles (5 degrees and 55 degrees C), the samples were processed and evaluated for marginal leakage at the cervical site. After scoring dye penetration in group 1 and 2 samples, half of the sections were randomly selected in order to evaluate 1) resin cement thickness and 2) hybrid layer formation at the interface between adhesive material and dental substrate. The leakage data were statistically evaluated with the Kruskal-Wallis non-parametric analysis of variance (ANOVA) by ranks with Bonferroni alpha adjustment (p < 0.05). RESULTS: Sixty percent of the group 1 samples and 80% of group 2 showed leakage. In group 1, the dye penetration was often limited to the cervical margin site, while in group 2, it mainly extended to the axial walls. Statistically significant differences between samples of the two groups were not found. Samples of group 1 showed a cement thickness of 82 microns, while 75 microns was found in group 2. A hybrid layer and resin tag formation were evident in group 1. In group 2 samples, the hybrid layer formation was less evident and thinner than in group 1. CONCLUSIONS: The two adhesive systems performed similarly. The cervical margins of single-unit all-porcelain crowns must be considered as one of the weakest areas of this type of esthetic restoration.

Adult↗
PubMed1999

Intermittent loading of teeth restored using quartz fiber, carbon-quartz fiber, and zirconium dioxide ceramic root canal posts.

PURPOSE: The purpose of the investigation was to compare the performances of teeth restored with quartz fiber, carbon-quartz fiber, and zirconium-dioxide posts covered with all-ceramic crowns when subjected to a cyclic loading test performed in a wet environment. MATERIALS AND METHODS: Forty single-rooted human lower premolars having similar dimensions were endodontically treated and mounted in acrylic resin blocks with a simulated periodontal ligament. The teeth were divided into three experimental groups and one control group. Post holes 8 mm long were prepared in the roots of the experimental groups in which quartz fiber, carbon-quartz fiber, and zirconium dioxide posts were cemented. In the control group, no posts were used. The crown buildup was made with composite resin. The teeth were covered with all-ceramic crowns and intermittently loaded at an angle of 45 degrees to the long axis of the tooth at a frequency of two loads per second. RESULTS: Only one failure (root fracture + post fracture) was observed in each of the fiber post groups, while in the zirconium dioxide post group, six failures were observed (one crown fracture and 5 root fractures + post fractures). The Kaplan-Meier analysis of the three experimental groups showed that the survival rate of zirconium dioxide posts was significantly lower than that of both types of fiber post. All the experimental groups showed a survival rate higher than that of the control group. CONCLUSION: Fiber posts reduced to a minimum the risk of root fractures of teeth restored with composite cores and Empress crowns under the present experimental conditions (intermittent loading in a wet environment).

Aluminum Silicates↗
PubMed1999

Study on mutations and antiretroviral therapy (SMART): preliminary results.

Resistance to antiretroviral drugs is believed to be an important cause of treatment failure in human immunodeficiency virus (HIV)-infected patients, however, the role of susceptibility assays in the management of these individuals needs to be defined. SMART (study on mutations and antiretroviral therapy) is an ongoing study on mutations and antiretroviral therapy focused particularly on HIV-infected patients treated with two nucleoside analogue reverse transcriptase inhibitors (NRTIs). Plasma HIV-1 RNA was assessed by NASBA (nucleic acid sequence-based amplifications) (Organon Teknika, Boxtel, The Netherlands) with a detection limit of 80 copies/ml, whereas resistance was assessed by direct sequencing of the RT pol gene in patients with detectable viraemia, and by Antivirogram (Virco) in non-responder patients. The preliminary results of this study show that both genotypic and phenotypic assays identify mutated viral strains in the majority of patients failing a dual regimen. Furthermore, the data indicate a high rate of genotypic resistance to lamivudine in both responders and non-responders, a high rate of phenotypic resistance to lamivudine in non-responders, no genotypic resistance to didanosine and stavudine in responders, and a very low rate of both genotypic and phenotypic resistance to didanosine and stavudine in non-responders.

Anti-HIV Agents↗
PubMed1999

Validation of double gradient denaturing gradient gel electrophoresis through multigenic retrospective analysis.

Among established techniques for the identification of either known or new mutations, denaturing gradient gel electrophoresis (DGGE) is one of the most effective. However, conventional DGGE is affected by major drawbacks that limit its routine application: the different denaturant gradient ranges and migration times required for different DNA fragments. We developed a modified version of DGGE for high-throughput mutational analysis, double gradient DGGE (DG-DGGE), by superimposing a porous gradient over the denaturant gradient, which maintains the zone-sharpening effect even during lengthy analyses. Because of this innovation, DG-DGGE achieves the double goals of retaining full effectiveness in the detection of mutations while allowing identical run time conditions for all fragments analyzed. Here we use retrospective analysis of a large number of well-characterized mutations and polymorphisms, spanning all predicted melting domains and the whole genomic sequence of three different genes--the cystic fibrosis transmembrane conductance regulator (CFTR), the beta-globin, and the p53 genes--to demonstrate that DG-DGGE may be applied to the rapid scanning of any sequence variation.

Cystic Fibrosis Transmembrane Conductance Regulato↗
PubMed1998

Dimerization of native myosin LC2(RLC)-free subfragment 1 from adult rabbit skeletal muscle.

We reinvestigated whether the native myosin LC2-free-subfragment 1 (S1) dimer exists by using viscometry, capillary electrophoresis, and laser light scattering. We found that the intrinsic viscosity of the monomer is [eta]m = 6.7 cm3/g and its translation diffusion coefficient is (c = 0) = 4.43 x 10(-)7 cm2/s. For the dimer, [eta]d = 19.8 cm3/g and (c = 0) = 2.54 x 10(-)7 cm2/s. Using the Svedberg equation and introducing the values of the sedimentation coefficients (5.05 S for the monomer and 6.05 S for the dimer), we find the following molecular weights: Mr,m = 108 000 Da and Mr,d = 213 000 Da, which agree well with previous determinations. Capillary electrophoresis successfully separated S1(A1) and S1(A2), in a monomer buffer, and S1(A1) and S1(A2) and a heterodimer S1(A1)-S1(A2), in a dimer buffer. An interesting feature of the monomer-dimer equilibrium is the presence of temperature transitions, whose positions and widths depend upon the buffer conditions. At low temperatures, a pure dimer was observed, whereas at high temperatures only the monomer was present. The dimerization site on both myosin and S1 is extremely labile.

Adenylyl Imidodiphosphate↗
PubMed1998

Detection of functional groups and antibodies on microfabricated surfaces by confocal microscopy.

Fluorescence confocal microscopy was used to characterize micron-sized microfabricated silicon particles and planar oxide surfaces after silanization and immobilization of IgG antibody. Surfaces treated with amino- and mercaptosilanes were tested for the presence of amine and sulfhydryl groups by labeling with specific fluorescein probes. In addition, human antibody (IgG) was immobilized to the thiol-coated microparticles using the heterobifunctional crosslinker succinimidyl 4-(N-maleimidolmethyl)-cyclohexane-1-carboxylate. Estimates of the surface density of IgG were consistent with 8.3% of a monolayer of covalently-bound antibody. Confocal images confirmed uniform layers of both silanes and antibodies on the microparticles. The sensitivity limit for the confocal measurements was determined to be as low as 1.5 x 10(-5) fluors per nm2.

Analysis of Variance↗
PubMed1998

Oxidation and reduction of cytochrome oxidase in the neonatal brain observed by in vivo near-infrared spectroscopy.

Near-infrared spectroscopy was used to determine the relationship between the redox state of mitochondrial cytochrome oxidase CuA and haemoglobin oxygenation in the isoflurane-anaesthetized neonatal pig brain. Adding 7% CO2 to the inspired gases increased the total haemoglobin concentration by 8 microM and oxidized CuA by 0.2 microM. Decreasing the inspired oxygen fraction to zero for 90 s dropped the oxyhaemoglobin concentration by 27 microM and reduced CuA by 1.8 microM. However, no change in the CuA redox state was observed until oxyhaemoglobin had decreased by more than 10 microM. The response of the CuA redox state to these stimuli was very similar following 80% replacement of the haemoglobin by a perfluorocarbon blood substitute; this demonstrates that the results in the normal haematocrit were not a spectral artefact due to the high haemoglobin/cytochrome oxidase ratio. We conclude that the large reductions in the CuA redox state during anoxia are caused by a decrease in the rate of oxygen delivery to the cytochrome oxidase oxygen binding site; the small oxidations, however, are likely to reflect the effects of metabolic changes on the redox state of CuA, rather than increases in the rate of oxygen delivery.

Animals↗
PubMed1998

NMR and luminescence studies on the formation of ternary adducts between HSA and Ln(III)-malonate complexes.

At physiological pH and in the presence of an excess of malonate ligand (MAL), the lanthanide ions (Ln=Eu(III), Gd(III) and Tb(III)) are under the form of [Ln(MAL)2(H2O)4]-. Upon addition of human serum albumin (HSA), formation of two different ternary adducts of stoichiometry HSA-Ln(MAL)x(H2O)q (x=2, q=2; x=2, q=4) is detected. On the basis of the reasonable assumption that the binding strength for the two sites on the protein are inversely proportional to the hydration state of the metal ion, stability constants of 4.0.103 M-1 and 3.5.102 M-1 have been evaluated for the system with q=2 and q=4, respectively. Whereas for the stronger binding site it is suggested that the protein provides two or three donor atoms to the coordination cage of the Ln(III) ion, in the case of the weaker binding site it is likely that it corresponds to a simple electrostatic interaction between the negatively charged [Ln(MAL)2(H2O)4]- and positively charged groups on the surface of the protein.

Europium↗
PubMed1998

Physical map of the D6S149-D6S193 region on chromosome 6Q27 and its involvement in benign surface epithelial ovarian tumours.

A detailed long range restriction map of the region defined by markers D6S149 and D6S193 on chromosome 6q27 has been constructed. This was achieved by YAC cloning and contig assembling of the same region. Seven YAC clones were found to span the almost 1000 Kb region flanked by the two markers which on the genetic map resulted to be 1.9 cM apart. With some of the characterized YAC clones we undertook a molecular cytogenetic analysis of 20 benign ovarian tumors. The rationale for this was the recent mapping to a region of chromosome 6q27, flanked by markers D6281 and D6S133, of a locus for the SV40-mediated immortalization of human cells (SEN6 gene). Noteworthy we found that the the D6S149-D6S193 region (comprised in the larger D6S281-D6S133 physical interval) was altered in all samples analysed adding support to the occurrence of a immortalization step in this type of tumors.

Chromosome Deletion↗
PubMed1998

Comparison of clinical-radiological and molecular findings in hypochondroplasia.

Hypochondroplasia is an autosomal dominant skeletal dysplasia characterized by disproportionate short stature. A mutation (N540K) in the fibroblast growth factor receptor 3 (FGFR3) gene was described in some patients with this condition. The aims of the study were to identify the frequency of the FGFR3 gene mutation, to define the salient clinical and radiological abnormalities of the affected subjects, and to verify the contribution of molecular findings to the clinical and radiological definition of hypochondroplasia. Based on the most common radiological criteria, we selected 18 patients with a phenotype compatible with hypochondroplasia. Height, sitting height, and cranial circumference were measured in all patients. Radiographs of the lumbar spine, left leg, pelvis, and left hand were also obtained. The presence of the N540K mutation was verified by restriction enzyme digestions. Half of our patients carried the N540K mutation. Although similar in phenotype to the patients without the mutation, they showed in addition relative macrocephaly. The association of the unchanged/narrow interpedicular distance with the fibula longer than the tibia was more common in patients with gene mutation. Although we did not find a firm correlation between genotype and phenotype, in our study the N540K mutation was most often associated with disproportionate short stature, macrocephaly, and with radiological findings of unchanged/narrow interpedicular distance and fibula longer than tibia.

Adolescent↗
PubMed1998

Microfabricated immunoisolating biocapsules.

A microfabricated silicon-based biocapsule for the immunoisolation of cell transplants is presented. The biocapsule-forming process employs bulk micromachining to define cell-containing chambers within single crystalline silicon wafers. These chambers interface with the surrounding biological environment through polycrystalline silicon filter membranes. The membranes are surface micromachined to present a high density of uniform pores, thus affording sufficient permeability to oxygen, glucose, and insulin. The pore dimensions, as small as 20 nm, are designed to impede the passage of immune molecules and graft-borne viruses. The underlying filter-membrane nanotechnology has been successfully applied in controlled cell culture systems (Ferrari et al., 1995), and is under study for viral elimination in plasma fractionation protocols. Here we report the encouraging results of in vitro experiments investigating the biocompatibility of the microfabricated biocapsule, and demonstrate that encapsulated rat neonatal pancreatic islets significantly outlive and outperform controls in terms of insulin-secretion capability over periods of several weeks. These results appear to warrant further investigations on the potential of cell xenografts encapsulated within microfabricated, immunoisolating environments for the treatment of insulin-dependent diabetes.

Animals↗
PubMed1998

Multiple testing in fetal gender determination from maternal blood by polymerase chain reaction.

Fetal male DNA can be identified in maternal blood by polymerase chain reaction (PCR) amplification of Y-specific sequences. This technology has not reached a satisfactory accuracy and reproducibility in fetal gender determination because of the very low concentration of fetal cells. Our purpose was to evaluate the possibility of improving the reliability of this test by setting up a repeated amplification system. We amplified, by nested PCR of the Y-specific sequence DYS14, 137 DNA samples extracted from maternal peripheral blood (93 from male-bearing and 44 from female-bearing pregnancies ranging from the 6th to the 36th gestational week). Each maternal DNA sample was tested doubly, in two different PCR sessions, with a total of four amplifications. We obtained discordant results in the four amplifications in 82/137 (60%) samples. The best interpretation of these discordant results was obtained by applying a positivity cutoff of at least two positive amplifications for considering a DNA sample as belonging to a male-bearing pregnancy. We obtained a sensitivity of 83%, a specificity of 93%, a positive predictive value of 96% and a negative predictive value of 72% in fetal male gender diagnosis. By applying this quadruple testing system, we significantly improved PCR accuracy and predictive values compared with single and double testing of the same samples. We conclude that, for future investigations of fetal DNA retrieved from maternal blood, the application of a quadruple testing system is better than the single PCR test.

DNA↗
PubMed1998

Risk factors for acute and subacute stent thrombosis after high-pressure stent implantation: a study by intracoronary ultrasound.

BACKGROUND: In the era of coronary stenting with high-pressure expansion, stent thrombosis remains a major life-threatening risk. Because of its superior imaging mode, intracoronary ultrasound could provide insight into potential risk factors for stent thrombosis. PATIENTS AND METHODS: In 215 patients with stent implantations controlled by intracoronary ultrasound, four occurrences of subacute stent thrombosis, two complete acute thrombotic occlusions, and four occurrences of incomplete acute thrombosis were observed. All stents were expanded with inflation pressures of at least 14 atm ( 17+/-3 atm). The clinical data and the qualitative and quantitative ultrasound information were compared between stents with thrombosis and stents without thrombosis. The luminal area and the plaque border of the reference segments, and of the smallest and largest site of the stented segment after the initial and final expansion, were measured. RESULTS: Stents in the left anterior descending artery were more often involved in stent thrombosis than other vessels, but the vessel dimensions in this target vessel were smaller than in the right coronary artery. The plaque burden was considerably larger after stent implantation with subsequent thrombosis compared with no thrombosis (74.1+/-8.8% vs 63.6+/-8.0%; p < 0.001), and the stent area was smaller (4.80%+/-1.33 mm2 vs 6.86+/-2.08 mm2; p < 0.01 ). In stents with thrombosis the plaque burden of the stent site with the smallest and largest lumen differed by 15.2%, whereas the difference in plaque burden in stents without thrombosis was 2.7%. Intracoronary ultrasound showed that the best risk predictor of thrombosis was the residual plaque burden of the stented segment (odds ratio 15.7 [confidence interval 2.4 to 104.7]), and a small stent area after implantation (odds ratio 6.8 [confidence interval 1.9 to 24.3]). CONCLUSION: In a multivariate risk analysis plaque burden was the strongest independent risk factor for stent thrombosis. The amount of residual plaque mass around the stent might be a potential trigger for thrombus formation.

Acute Disease↗