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Biomedical subjects

G Landini

Publications and source records attributed to G Landini.

At least 19 recordsLinked to original sources
PubMed2003

Displacement amplitude of ultrasonic scaler inserts.

OBJECTIVES: Scanning laser vibrometry is a noninvasive method of measuring the velocity, displacement amplitude and oscillation frequency of vibrating objects. The purpose of this study was to assess, using a scanning laser vibrometer (SLV), the performance of different designs of commercially available ultrasonic scaler generators by measuring the oscillatory characteristics of various scaler tips. METHODS: Four ultrasonic generators were tested (Cavitron SPS and Cavitron Select (Dentsply, York, PA, USA) and Piezon Master 400 and Mini Piezon (Electro-Medical Systems, Switzerland)) with various designs of scaler tip. The tips were positioned with their anterior surface perpendicular to the direction of the laser. A graduated scale, placed over the manufacturer's power dial, enabled incremental power setting selection. For each power setting, the laser beam from the SLV was scanned over the surface of the oscillating tip. RESULTS: The ranges of longitudinal displacement amplitudes (in micrometres) were as follows: Mini Piezon (P-tip): 12.90+/-1.44 to 44.03+/-7.80; Piezon Master 400 (P-tip): 16.02+/-2.66 to 35.85+/-5.29; Cavitron SPS (TFI-10 tip): 7.81+/-0.51 to 29.70+/-1.12; Cavitron Select (TFI-10 tip): 13.13+/-1.44 to 33.77+/-4.27; Cavitron SPS (TFI-3 tip): 5.50+/-0.46 to 31.35+/-3.62. CONCLUSIONS: This study shows that there are differences between commercially available generators and that tip movement varies between tips of the same style as well as between the generator and tip design. Users of ultrasonic scalers should be made aware of this inherent variability that may influence clinical procedures.

Dental High-Speed Technique↗
PubMed2003

Estimation of tissue layer level by sequential morphological reconstruction.

An automated method for labelling layers of clustered elements in two dimensional images based on morphological operations is presented here. Unlike the various distance transforms for regular lattices, the procedure deals successfully with clusters composed of different shaped and sized elements and provides a distance measure, in number of layers, from each element in the cluster to any other reference element (or elements). The method was applied to histological sections of two different types of polystratified epithelia. Local clusters in the different cell profile layers can subsequently be used to define the orientation of the tissue layers relative to each element in it.

Epithelium↗
PubMed2002

Investigation of primary cell-biomaterial interactions using silver nitrate staining of nucleolar organising regions.

The quantification of silver nitrate staining of nucleolar organising regions (AgNORs) within the nucleus of the cell has been shown to give a relative measure of the metabolic activity of the cell. In the present study, silver nitrate staining was utilised to identify metabolic variations in cells cultured on different surfaces and compared with proliferative activity assessed using bromodeoxyuridine (BrdU) uptake. Primary osteoblast and periosteal cells, isolated from the calvaria of neonate rats, were cultured on tissue culture-grade (TCPS) and bacteriological-grade (BACPS) polystyrene petri dishes for 3, 5, 7 and 9 days (silver nitrate) or 14 days (BrdU). The phenotype of the cells was examined using RT-PCR of the mRNA for osteocalcin, collagen 1a, alkaline phosphatase and osteopontin. The number and area of AgNORs and the proportion of BrdU positive cells were statistically different in cells cultured on TCPS compared with BACPS at each culture period tested. The results suggest that the metabolic activity and proliferation of cells were affected by the substrate which they colonise.

Animals↗
PubMed2002

Vibration characteristics of ultrasonic scalers assessed with scanning laser vibrometry.

OBJECTIVES: Scanning laser vibrometry is a non-invasive method of accurately measuring the vibratory characteristics of oscillating objects. The aim of this study was to observe, using a scanning laser vibrometer (SLV), the vibration patterns of dental ultrasonic scaler tips and to assess the effects of water flow rate and power setting on these patterns whilst operating the tips in an unloaded environment. METHODS: A 30kHz ultrasonic scaler (TFI-10, Dentsply) was fixed in position and a laser beam from the SLV was focused onto the tip. The laser, guided by a virtual measurement grid, was scanned over the oscillating tip surface. Scans were taken with the laser beam perpendicular to the long axis of the front face of the tip. RESULTS: Oscillation frequencies and the displacement amplitude at the unconstrained end of the tip were measured for various power/water settings. Vibration nodal positions were recorded for the various settings and were found to occur approximately 4mm from the free end of the tip. At low and medium power settings, tip displacement amplitude was reduced by increased water flow. At high power settings, combined with a high flow rate, the water leaves the body of the instrument as a jet. This left the tip relatively unconstrained, allowing it to oscillate at increased displacement amplitudes. CONCLUSIONS: This study shows that the SLV is able to accurately characterise the movement of oscillating ultrasonic scaler tips. The tips are affected by power setting and water flow rates.

Analysis of Variance↗
PubMed2002

Assessment of the ultrasonic dental scaler insert.

The ultrasonic dental scaler is an invaluable tool in the fight against dental calculus and periodontal disease. The purpose of this study was to assess the natural frequency of the straight internal ultrasonic scaler insert 30K FSI-SLI-10S (Dentsply International, York, USA) and to measure the displacement observed at the tip when operated under different generator settings. Two approaches were used: finite element analysis and scanning laser vibrometry. The Finite Element Analysis method was employed to calculate the expected modes of vibration of the insert. Scanning laser vibrometry was used to measure displacements of the tip during operation. It was found the insert had two modes of vibration around the operating frequency of 30 kHz; these modes were first order bending in two orthogonal planes.

Dental Scaling↗
PubMed2001

The influence of mixing ratio on the toughening mechanisms of a hand-mixed zinc phosphate dental cement.

OBJECTIVE: A range of mixing ratios occur for zinc phosphate cements in clinical usage and trials. The compressive strength of these cements is dependent on mixing ratio and at a critical ratio, a sudden rise in compressive strength is known to occur. This study investigated the mechanisms behind the cement curve behavior in an attempt to explain the strength increase with mixing ratio. METHODS: Crack propagation from indentations produced in cements were examined to identify if any variation in toughening mechanism existed over the range of mixing ratios investigated (1.7-3.2g/ml). Pore distribution within the cylindrical specimens was determined using an image analysis technique. RESULTS: Increasing the powder content from 2.3 to 2.4g/ml increased the number of powder agglomerates formed in the cement mix over individual particles. The likelihood of introducing pores in excess of 42 microm diameter was enhanced when the ratio exceeded 2.6g/ml. SIGNIFICANCE: It is proposed that crack deflection by agglomerates in the cement reduces the energy of the crack fronts emanating from indentations more than would occur with individual powder particles. This decreases the cracks ability to progress and is likely to result in the marked strength increase from 2.3 to 2.4g/ml identified previously. It is suggested that cement pores in excess of 42 microm diameter were probably generated on filling the sample molds with more viscous cements. These results emphasise that the properties of cements manipulated under optimum conditions provide little information on the cement characteristics present in clinical practice.

Compressive Strength↗
PubMed2001

Plaque removal characteristics of electric toothbrushes using an in vitro plaque model.

BACKGROUND/AIM: The purpose of the study was to investigate and quantify the efficacy of plaque removal by commercially available electric toothbrushes using an in vitro system based on artificial plaque grown on glass slides. MATERIAL AND METHODS: Artificial plaque based on Streptococcus sanguis and Streptococcus mutans was cultured in a series of phosphate buffer solution, sucrose solution and brain heart infusion on sterile glass slides, for a period of 5 weeks. 7 different electric toothbrushes of current designs were operated in contact with the glass slides under loads of 1 or 2N for 10 s after which image analysis of the brushed slides was undertaken to calculate the absolute and relative areas of removal. RESULTS: The electric toothbrushes showed a larger area of plaque removal as loading force increased from 1 to 2N. The area of biofilm removed also depended on the head design and ranged from 258 mm(2) (1N, Interplak) and 314 mm(2) (2N, Interplak), to 30 mm(2) (1N, Braun 3D), and 148 mm(2) (2N, Blend-a-Dent). The area of biofilm removal was significantly different among all electric toothbrushes at p<0.01 (ANOVA). All electric toothbrushes removed more biofilm than the actual contacting tufted area of the head. CONCLUSION: The artificial plaque model system under different loading conditions showed differences in the absolute area of removal per electric toothbrush and also differences in the relative removal per unit contact bristle area. These differences on operating variables should be considered when evaluating new electric toothbrushes.

Algorithms↗
PubMed2001

Characteristics, outcome, and care of stroke associated with atrial fibrillation in Europe: data from a multicenter multinational hospital-based registry (The European Community Stroke Project).

BACKGROUND AND PURPOSE: The role of atrial fibrillation (AF) as a determinant of stroke outcome is not well established. Studies focusing on this topic relied on relatively small samples of patients, scarcely representative of the older age groups. We aimed at evaluating clinical characteristics, care, and outcome of stroke associated with AF in a large European sample. METHODS: In a European Concerted Action involving 7 countries, 4462 patients hospitalized for first-in-a-lifetime stroke were evaluated for demographics, risk factors, clinical presentation, resource use, and 3-month survival, disability (Barthel Index), and handicap (Rankin scale). RESULTS: AF was present in 803 patients (18.0%). AF patients, compared with those without AF, were older, were more frequently female, and more often had experienced a previous myocardial infarction; they were less often diabetics, alcohol consumers, and smokers (all P:<0.001). At 3 months, 32.8% of the AF patients were dead compared with 19.9% of the non-AF patients (P:<0.001). With control for baseline variables, AF increased by almost 50% the probability of remaining disabled (multivariate odds ratio 1.43, 95% CI 1.13 to 1.80) or handicapped (multivariate odds ratio 1.51, 95% CI 1.13 to 2.02). Before stroke, only 8.4% of AF patients were on anticoagulants. The chance of being anticoagulated was reduced by 4% per year of increasing age. AF patients underwent CT scan and other diagnostic procedures less frequently and received less physiotherapy or occupational therapy. CONCLUSIONS: Stroke associated with AF has a poor prognosis in terms of death and function. Prevention and care of stroke with AF is a major challenge for European health systems.

Adolescent↗
PubMed2000

Increased fractal complexity of the epithelial-connective tissue interface in the tongue of 4NQO-treated rats.

The effect of the carcinogen 4-nitroquinoline 1-oxide (0.001% in drinking water) on the irregularity of the epithelial connective tissue interface (ECTI) of the ventral surface of the tongue was quantified in Dark Agouti and Wistar Furth rats. Histological tongue sections stained with the Azan-Mallory method were digitised (111 images, resolution 1 pixel = 3.1 microns), and the limit between epithelium and stroma of the ventral surface was extracted and analysed using a fractal geometry technique (local connected dimension). The results showed that although none of the images included carcinomas on the ventral surface of the tongue (all cases had other oral carcinomas), the epithelial profiles of the treated cases showed a statistically significant increase in irregularity when compared to controls. Canonical discriminant analysis of the parameters describing the irregularity of the ECTI classified 81.1% of the images in the original groups (treated or control). Fractal analysis is capable of detecting subtle architectural changes in the oral epithelium of the rat occurring after exposure to the carcinogen, even when full malignant transformation has not yet taken place. Fractal analysis, which may prove useful for monitoring the progression of carcinogenesis in this animal model, is a morphometrical parameter in the diagnosis of oral epithelial dysplasia.

4-Nitroquinoline-1-oxide↗
PubMed2000

Modeling of mosaic patterns in chimeric liver and adrenal cortex: algorithmic organogenesis?

If organogenesis were a completely deterministic process, then the amount of information required to store the spatial position and fate of every cell in vertebrate organisms would be larger than the total information that could be contained in their genomes. This suggests that the instructions of developmental mechanisms involved in organogenesis, coded in DNA, must be at least in part procedural or algorithmically based. Chimeric mosaic patterns in rat livers have been shown to be isotropic and to have fractal profiles (D approximately 1.3) whereas adrenal gland mosaics show a less irregular radial pattern, with lower fractal dimension (D approximately 1.2) than in the liver. These findings suggested a possible model of parenchyma generation. We propose that during organogenesis in both liver and adrenal cortex, the same basic mechanism is directed to organ mass enlargement, whereas the differences observed in mosaic patterns between the organs could be due to the control of a single parameter, namely, a form of contact inhibition. Computer simulations in two dimensions returned comparable results in both the fractal dimension value of mosaic patches and appearance of the mosaic 'tissues', as observed histologically in chimeras. This suggests that position information and locomotion of cells would not be required to produce the mosaic pattern observed in chimeras.

Adrenal Cortex↗
PubMed1999

Calibration of the Periotron 8000 and 6000 by polynomial regression.

This paper reports the detailed calibration of the new Periotron 8000 with different fluids and uses the method of least squares to derive polynomial regression equations up to the 6th order, to investigate the most accurate descriptor of the resulting calibration lines. The use of a 4th order polynomial regression equation (recommended by the manufacturer) provided better coefficients of determination (R2: 0.999) and root mean square errors (RMSE = 1.6) than either linear regression (R2: 0.986, RMSE = 10.9) or quadratic models (R2: 0.998, RMSE = 3.2). Data derived using the manufacturer's MLCONVERT software program lacked accuracy and incurred large errors for volumes > 0.5 microliter. Calibrations performed on one day could be used with accuracy to derive volumes > 0.1 microliter collected on subsequent days, when using the same machine (s.d. for residuals plot = 2.49 Periotron units), but this was not the case for different machines (s.d. = 9.57 Periotron units). Varying serum protein concentration by up to 500% had a negligible effect on calculated volumes above 0.1 microliter. We conclude that the Periotron 8000 is at least as reliable a machine as the Periotron 6000, and that the calibration lines for both machines are best described using 4th order polynomial regression equations and "look-up" tables, rather than quadratic (Periotron 6000) or the manufacturer's software (Periotron 8000). Serum seems to be an acceptable GCF substitute for calibrations, which can be performed 1 day, and used on subsequent days for a given machine and for volumes above 0.1 microliter.

Calibration↗
PubMed1998

Asymptotic fractals in the context of grey-scale images.

The estimation of the fractal dimension in the case of concave log-log Richardson-Mandelbrot plots can be obtained by using asymptotic fractal equations. We demonstrate here, under asymptotic fractal conditions, that additional derivations making use of the Minkowski dilation in grey-scales lead to two asymptotes, one having a slope of 1 and the other a slope of DT-D + 1 (where DT is the topological dimension and D the fractal dimension). The resulting equation offers important advantages. It allows: (i) evaluation of scaling properties of a grey-scale image; (ii) estimation of D without any iteration and (iii) generation of texture and heterogeneity models. We concentrate here on the first two possibilities. Images from cultured cells in studies of cytoskeleton intermediate filaments and kinetic deformability of endothelial cells were used as examples.

Endothelium, Vascular↗
PubMed1998

Expression of cadherins and catenins in oral epithelial dysplasia and squamous cell carcinoma.

The immunocytochemical expression of cadherins and catenins was examined during the process of oral carcinogenesis by comparing their expression in normal and dysplastic epithelium with primary and metastatic carcinomas. While control epithelium showed normal distribution for P and E cadherin and the catenins, in severe dysplasia P-cadherin was upregulated. In other cases and in carcinoma-in-situ adjacent to infiltrating carcinomas, membranous expression of the cadherins and catenins was reduced or lost. The changes in expression of E-cadherin and the catenins suggest that disruption of the E-cadherin/catenin complex is a late event associated with invasion. In primary carcinomas reduced membranous and cytoplasmic staining were observed for both cadherins and catenins. Abnormal localisation of E-cadherin occurred in the more superficial parts of the better differentiated carcinomas, suggesting abnormality to the E-cadherin complex(es). In contrast, membranous expression of cadherins and catenins was reduced or lost in the deep invasive margin of primary carcinomas and in most poorly differentiated carcinomas. For E-cadherin at least, this reduction appears associated with differentiation, invasion and possibly prognosis. Possible mechanisms involved for changes in expression of the cadherins and associated catenins and areas for further study are discussed.

Cadherins↗
PubMed1998

Incidence and determinants of poststroke dementia as defined by an informant interview method in a hospital-based stroke registry.

BACKGROUND AND PURPOSE: Inconsistent information about incidence and determinants of poststroke dementia might be related to patient attrition, partly because of nonapplicability of formal neuropsychological testing to a large proportion of patients registered in a definite setting. METHODS: Using a proxy-informant interview based on ICD-10 criteria, we determined dementia at stroke onset and 1 year after stroke in the 339 patients who survived, were available for follow-up, and were not demented at stroke onset of 635 patients entered over a 1-year period in a stroke registry taken at 2 community hospitals in Florence, Italy. RESULTS: Of the 339 patients, 57 (16.8%) proved to have poststroke dementia. These patients were older, more frequently female, and more often (multivariate odds ratio, 2.35; 95% CI, 1.21 to 4.58) had atrial fibrillation than those without dementia. Aphasia and the clinical features expressing the severity of the stroke event in the acute phase predicted poststroke dementia. CONCLUSIONS: In a hospital-based nonselected series of stroke survivors, despite the use of a method with low sensitivity for defining dementia, our study confirms that dementia is a frequent sequela of stroke and is mainly predicted by stroke severity. Certain determinants could be controlled in the prestroke phase, thus reducing its risk.

Age Distribution↗
PubMed1998

A testing system for electric toothbrushes.

PURPOSE: To assess in vitro the contributions of mechanical and acoustic microstreaming forces around electric toothbrushes to remove cheese using an experimental model. MATERIALS AND METHODS: Four toothbrushes, Braun Oral-B Plaque Remover (D7), Braun Oral-B Ultra Plaque Remover (D9), Interplak (IP) & Sonicare (SC), were investigated. A model system consisting of a layer of 0.2 mm thick cheese was applied to a microscope slide. The toothbrushes were operated in contact with the slide under loads of 0.3 N dry or with the bristles immersed in 2 mm of water. Turbulence around the moving head was assessed with the bristles placed non-contacting, 1 mm above the slide. An experiment with contact for 2 seconds and then 10 seconds non-contact was also made. The slides were stained and image analyzed. The area of removal was measured together with the "average cleaning/brush contact unit area", (the area of removal was divided by bristle contact area. RESULTS: The removal pattern varied. D9 and SC were efficient when operated dry. When the brushes were operated in water, the D9, SC, and IP were efficient in removing the cheese. With no contact, SC produced disruption of the cheese layer while the other brushes did disturb the surface but did not remove completely the cheese. This disturbance without removal was not recorded by image analysis. When the vibrating brushes were allowed to touch the medium and then moved away, a large amount of removal occurred. Larger amounts of removal took place with the D7, D9 and the SC. The use of brushes with a larger head and bristle contact produced a larger area of removal. However, when the "average cleaning/brush contact unit area" was used, the smaller headed brushes produced a larger amount of removal relative to their size. These differences in the removal characteristics between the four electric toothbrushes in vitro suggest that such a model system may prove useful in testing such devices before they are assessed clinically.

Analysis of Variance↗
PubMed1997

Discrimination of complex histopathological tumour profiles by experienced and inexperienced observers.

One of the tasks that pathologists routinely perform in diagnosis is the assessment of complexity of shape or texture of microscopic images. Because some of these complex patterns can be approximated in terms of fractal structures, it is important to understand how fractal structures are perceived by pathologists, and whether pathologists use specific perceptual strategies to quantify such patterns. Knowledge about this could be advantageous for either producing specific training programmes to increase complexity discrimination or to utilise more unbiased and quantitative imaging methodologies in histopathology. We have previously demonstrated that non-expert observers with high abilities in simultaneous information processing were best at the task of discriminating the fractal dimension of self-similar computer-generated curves. Here we compare the performance of experienced and inexperienced observers in a similar task of discriminating epithelial profiles. The results suggest that there are no differences between experienced and inexperienced observers in this task of complex profile discrimination.

Carcinoma, Squamous Cell↗
PubMed1997

Is periodontal breakdown a fractal process? Simulations using the Weierstrass-Mandelbrot function.

This paper introduces a theoretical model of periodontal disease that is multifactorial, cumulative and produces periodontal breakdown in "bursts and remissions". The simulation is based on the generalization of the Weierstrass-Mandelbrot function as an integration of a series of sinusoid fluctuations that facilitate or prevent periodontal breakdown with different frequencies, amplitudes and phases. The breakdown is produced when the integration of the factors reaches a certain threshold and is stopped when it is below it. The zeroset of the function (the set of points of the function in intersection with the time axis) is a self-similar set that corresponds to the instances when the process switches between destructive and non-destructive phases, and its fractal nature indicates that in theory, bursts of destruction do not have a characteristic duration size. If the mechanism of periodontal disease has in principle similarities to the model presented, then accurate site-specific predictions about periodontal destruction may prove an unrealizable task.

Alveolar Bone Loss↗