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Biomedical subjects

Gabriel Landini

Publications and source records attributed to Gabriel Landini.

16 recordsLinked to original sources
PubMed2006

The effects of load and toothpaste on powered toothbrush vibrations.

OBJECTIVES: The primary cleaning action of powered toothbrushes is the motion of the bristles in contact with the tooth surfaces. The aim of this study was to use scanning laser vibrometry to determine the effects of load and toothpaste on the bristle vibration characteristics of four powered toothbrushes (Oral-B Sonic Complete; Oral-B Professional Care 8000 Series; Sonicare Elite and Ultrasonex). METHODS: Toothbrushes were initially scanned, with the laser vibrometer, under unloaded conditions to provide baseline readings. Toothbrushes were then assessed under loaded conditions (1.00 N and 2.00 N), with and without toothpaste, to observe the effect on bristle motion. RESULTS: Application of 1.00 N load significantly reduced the displacement amplitudes of all powered toothbrushes (p<0.003) except for the Sonicare (p>0.497). With toothpaste, 1.00 N load caused a significant decrease in vibration displacement amplitude for all brushes (p<0.0001). The application of 2.00 N, with and without toothpaste, significantly reduced all toothbrushes vibration displacement amplitude (p<0.0001). Under all investigation conditions, the Oral-B 8000 had the largest vibration displacement amplitude of the toothbrushes tested. CONCLUSIONS: Load and toothpaste significantly affected the performance of powered toothbrushes. Understanding why these factors affect certain toothbrush designs more than others may lead to toothbrushes being designed with greater clinical efficacy.

Analysis of Variance↗
PubMed2006

Quantitative analysis of the epithelial lining architecture in radicular cysts and odontogenic keratocysts.

BACKGROUND: This paper describes a quantitative analysis of the cyst lining architecture in radicular cysts (of inflammatory aetiology) and odontogenic keratocysts (thought to be developmental or neoplastic) including its 2 counterparts: solitary and associated with the Basal Cell Naevus Syndrome (BCNS). METHODS: Epithelial linings from 150 images (from 9 radicular cysts, 13 solitary keratocysts and 8 BCNS keratocysts) were segmented into theoretical cells using a semi-automated partition based on the intensity of the haematoxylin stain which defined exclusive areas relative to each detected nucleus. Various morphometrical parameters were extracted from these "cells" and epithelial layer membership was computed using a systematic clustering routine. RESULTS: Statistically significant differences were observed across the 3 cyst types both at the morphological and architectural levels of the lining. Case-wise discrimination between radicular cysts and keratocyst was highly accurate (with an error of just 3.3%). However, the odontogenic keratocyst subtypes could not be reliably separated into the original classes, achieving discrimination rates slightly above random allocations (60%). CONCLUSION: The methodology presented is able to provide new measures of epithelial architecture and may help to characterise and compare tissue spatial organisation as well as provide useful procedures for automating certain aspects of histopathological diagnosis.

Journal Article↗
PubMed2006

The effect of wear on ultrasonic scaler tip displacement amplitude.

AIM: During clinical usage, scaler tips may become worn and reduced in length. It is unknown what effect wear has on the magnitude of scaler tip vibrations when they are utilized under typical clinical loads. The aim of this investigation was to assess the effect of simulated wear on ultrasonic scaler tip displacement amplitude, using a scanning laser vibrometer. MATERIALS AND METHODS: A Cavitron SPS (Dentsply) ultrasonic generator and three scaler insert designs (FSI-100, FSI-1000 and FSI-SLI-10S) were selected for the investigation. Tip vibration displacement amplitude was assessed unloaded and then contacting against tooth surfaces with loads of 0.5 and 1.0 N. Tips were then ground down by 1 mm and then 2 mm and scans were repeated. RESULTS: For all tips, load and length were found to be significant variables (p<0.0001). The scaler tips showed a fall in displacement amplitude with a reduction in tip length. However, all scaler tips showed variability in the amount oscillation that occurred. This was most pronounced with FSI-SLI-10S. CONCLUSIONS: This investigation demonstrated that tip wear could affect the performance of dental ultrasonic scaler inserts by reducing their vibration displacement amplitude. Clinicians should be aware of this variability, which may be significant enough to affect clinical procedures.

Dental High-Speed Technique↗
PubMed2005

An in-vitro investigation of the accuracy of fit of Procera and Empress crowns.

The current study aimed to investigate the accuracy of fit and the reproducibility of inner crown profile for two types of high strength ceramics, IPS Empress and Procera. Procera and Empress crowns with four different morphologies were cemented to dies using zinc phosphate dental cement. Vertical and horizontal sections were made through each of the crown/die preparations and images of the vertical sections were compared for curvature reproduction by alignment using image processing. Measurements were made on horizontal sections to determine cement layer thickness. Alignment of the crowns using image analysis identified quantifiable variations in the inner surface profile compared with the outer surface of the die. The largest differences occurred from the cusp tips to the occlusal adaptation area and differences in surface profile were less pronounced for Procera than Empress crowns. Marginal gap varied independently of ceramic or internal crown shape from 7-529 microm for Procera and 26-548 microm for Empress. IPS Empress has a superior ability to reproduce the inner surface profile of the crown morphologies investigated compared with Procera. The reduced reproduction of surface profile was associated with an increased cement thickness at the occlusal contact area that may inadvertently lead to failure of the crowns functional characteristics.

Crowns↗
PubMed2005

Morphometry of pseudoepitheliomatous hyperplasia: objective comparison to normal and dysplastic oral mucosae.

OBJECTIVE: To compare the architectural and morphometric features of pseudoepitheliomatous hyperplasia (PEH) associated with oral granular cell tumors (GCT), normal oral mucosa and oral epithelial dysplasia. STUDY DESIGN: Quantitative comparisons between the diagnostic entities were carried out at the tissue level by estimating the fractal complexity of the epithelial connective tissue interface and at the cellular level by analyzing the morphometric features of algorithmically segmented epithelial cell areas. RESULTS: Casewise multivariate analysis showed that the fractal properties produced a correct discrimination rate of 96.4% between PEH and normal mucosa. Cellular parameters gave a 100% correct discrimination rate between PEH and mild dysplasia. Combining the fractal and cellular properties also showed 100% discrimination between PEH and normal mucosa and between PEH and mild dysplasia. CONCLUSION: The results show that PEH associated with GCT displays quantifiable morphometric features that make it differentiable from normal oral mucosa and oral epithelial dysplasia.

Adult↗
PubMed2004

Architectural analysis of oral cancer, dysplastic, and normal epithelia.

BACKGROUND: We present a novel, automated, and quantitative approach to evaluate local epithelial tissue architecture based on mathematical graph theory. METHODS: Four hundred forty-one images of three diagnostic classes of oral epithelium (normal, dysplastic, and neoplastic) were analysed. The epithelial compartment was partitioned into exclusive areas associated with each nucleus to approach the theoretical cell extents. The spatial arrangement of cells in neighbourhoods of two sizes was characterised by constructing graph networks based on the cell centroids and recording 29 statistical properties. We analysed 104,627 and 67,590 neighbourhoods of diameters 37.5 and 75 microm, respectively. RESULTS: The discrimination power of the architectural descriptors was evaluated by using discriminant analysis. The best neighbourhood discrimination rate was 75% for normal versus carcinoma. For the pooled data, discrimination into three classes based on largest number of neighbourhoods associated with each class was 100% correct. Case-wise, discrimination rates were 67%, 100%, and 80% correct for normal, premalignant, and malignant. When considering two classes, discrimination rates was 89% (normal) and 100% (malignant) correct, with 71% of premalignant cases assigned to the malignant class. CONCLUSIONS: The results indicate that unbiased and reproducible quantification of tissue architectural features is possible and may provide valuable morphological information for diagnostic purposes.

Cytodiagnosis↗
PubMed2004

Automated quantification of dental plaque accumulation using digital imaging.

OBJECTIVES: Most dental plaque indices have a subjective component due to investigator interpretation. To assess the accumulation of plaque on teeth, a fully automated method was developed based on digital imaging of methylene blue (1% (w)/(v)) disclosed plaque. METHODS: Intra-oral colour images of disclosed plaque from 25 individuals were coded into hue, saturation and intensity colour space. Unequivocal areas of clean teeth, plaque and clean gingiva were sampled to determine the typical values of hue, saturation and intensity of light. RESULTS: Discriminant analysis showed that the success rate for classification of the pixels as plaque and non-plaque was 87.3% based on saturation and intensity, and 98.7% for a classifier based on hue and intensity. Fisher's function coefficients were used to create classification boundaries in the colour space which would allow to automatically classify new images. CONCLUSIONS: This method has potential for automated and quantitative measurement screening of dental plaque that may be used to assess the efficacy of oral hygiene products and procedures.

Adult↗
PubMed2004

Thermal imaging of ultrasonic scaler tips during tooth instrumentation.

OBJECTIVES: During ultrasonic scaling procedures, contact of the scaler tip with the tooth surface will produce frictional heating. The aim of this study was to assess this heat generation using an Agema 900 thermal imaging system. MATERIALS AND METHODS: Both the Cavitron sustained performance system (SPS) with TFI-3 tip and the Mini Piezon with P-tip were tested. Handpieces were fixed with their sides facing the thermal camera and thermal image sequences or "movies" created. Measurements were performed with tips under loads of 25, 50 and 100 g, at water flow rates of 10, 20 and 40 ml/min and low, medium and high generator power settings. A measurement point was superimposed on the resulting thermal images at the tip/tooth contact site and the temperature variation with time recorded. RESULTS: All combinations of instrumentation produced an increase in temperature. An increase in temperature was generally observed with increasing load (for given power/water), power setting (for given load/water) and a decrease in water flow rate (for given load/power). CONCLUSION: Heat generation is minimised by using low/medium power settings and light contact. Care must be taken to ensure adequate water is present at the site of instrumentation to prevent patient discomfort due to excessive heating.

Body Temperature↗
PubMed2004

S100 and cytokine expression in caries.

The molecular immune response of the pulpal tissue during chronic carious infection is poorly characterized. Our objective was to examine the expression of potential molecular mediators of pulpal inflammation, correlate their levels with disease severity, and determine the cellular localization of key molecules. Results indicated that there was significantly increased transcriptional activity in carious compared to healthy pulp, and the increase correlated positively with disease severity. Semiquantitative reverse transcriptase PCR analysis in 10 carious and 10 healthy pulpal tissue samples of the S100 family members S100A8, S100A9, S100A10, S100A12, and S100A13; the cytokines tumor necrosis factor alpha (TNF-alpha), interleukin-1beta (IL-1beta), IL-8, IL-6, and epithelial cell-derived neutrophil attractant 78 (ENA-78); and the structural protein collagen-1alpha indicated that all genes tested, with the exception of S100A10, were more abundantly expressed in carious teeth. In addition, we found that the closer the carious lesion front was to the pulpal chamber the higher the expression was for all genes except S100A10. Multiple-regression analysis identified a significant positive correlation between the expression levels of S100A8 and IL-1beta, ENA-78, and IL-6 and between collagen-1alpha and S100A8, TNF-alpha, IL-1beta, IL-8, IL-6, and ENA-78. Immunohistochemical studies in carious pulpal tissue indicated that S100A8 and the S100A8/S100A9 complex were predominantly expressed by infiltrating neutrophils. Gene expression analyses in immune system cells supported these findings and indicated that bacterial activation of neutrophils caused upregulation of S100A8, S100A9, and S100A13. This study highlights the complex nature of the molecular immune response that occurs during carious infection.

Adult↗
PubMed2004

A mathematical model of the dynamics of odontogenic cyst growth.

OBJECTIVE: To formulate a mathematical model of odontogenic cyst growth and establish the dynamics of cyst enlargement and role of osmotic pressure forces throughout its growth. STUDY DESIGN: The model assumed a spherical cyst with a semipermeable lining of living cells and a core consisting of degraded cellular material, including generic osmotic material, fed by the continuous death of epithelial cells in the lining. The lining cells were assumed to have both elastic and viscous properties, reflecting the action of physical stresses by the surrounding cyst capsule, composed of fibroblasts and collagen fibers. The model couples the cyst radius and osmotic pressure differences resulting in a system of 2 nonlinear ordinary differential equations. RESULTS: The model predicts that in all parameter regimens the long-time behavior of the cyst is the same and that linear radial expansion results. CONCLUSION: In the early and intermediate stages of cystic growth, osmotic pressure differences play an important role; however, in very large cysts, this role becomes negligible, and cell birth in the lining dominates growth.

Algorithms↗
PubMed2004

A novel method for the evaluation of powered toothbrush oscillation characteristics.

PURPOSE: To assess the vibration characteristics of oscillating objects with the scanning laser vibrometer (SLV). A laser is scanned over the surface of a vibrating target and the reflected, Doppler frequency shifted beam is used to determine the displacement amplitude and frequency of the vibration. This communication reports on a preliminary investigation to assess unloaded powered toothbrush oscillations, using Scanning Laser Vibrometry. METHODS: Four powered toothbrushes were selected for this study including the Sonicare, Philips/Jordan Sensiflex HX2520, Braun 3D and Braun D8. Each toothbrush was clamped in position and 10 area scans of their heads were taken from the side orientation to determine the displacement amplitude and frequency of oscillation. RESULTS: The fundamental frequency of oscillation of each brush was determined: Sonicare: 262.5Hz; Philips: 62.5Hz; 3D: 75Hz and D8: 62.5Hz. The maximum displacement amplitude (half the peak-to-peak excursion) for each brush (at the tips of the longest bristles) was Sonicare; 2.51 +/- 0.32mm, Philips; 2.60 +/- 0.15mm, Braun 3D; 2.14 +/- 0.18mm and Braun D8; 2.14 +/- 0.21.

Dental Devices, Home Care↗
PubMed2003

Quantification of the global and local complexity of the epithelial-connective tissue interface of normal, dysplastic, and neoplastic oral mucosae using digital imaging.

This study aimed at quantifying the complexity of the epithelial-connective tissue interface (ECTI) in human normal mucosa, premalignant, and malignant lesions using fractal geometry. Two approaches were used to describe the complexity of 377 oral mucosa ECTI profiles. The box counting method was used to estimate their global fractal dimension, while local fractal dimensions were estimated using the mass radius relation at various local scales. The ECTI complexity significantly increased from normal through premalignant to malignant profiles in both global and local (over 283 microm) scales. Normal mucosa samples from different sites of the oral cavity also had different degrees of global complexity. Fractal geometry is a useful morphological marker of tissue complexity changes taking place during epithelial malignancy and premalignancy, and we propose it as a quantitative marker of epithelial complexity.

Biopsy↗
PubMed2003

Effect of loading on the vibration characteristics of thin magnetostrictive ultrasonic scaler inserts.

BACKGROUND: The ultrasonic scaler market has seen an increase in availability of thin inserts for periodontal pocket access. While such thin inserts may have advantages in negotiating the periodontal pocket, the relatively narrow structure may be prone to damping under load. The purpose of this study was to assess the vibration characteristics under load of thin, straight, ultrasonic scaler inserts. METHODS: Five types of thin inserts were each obtained from three manufacturers and were operated using an ultrasonic generator at medium power and low water. The displacement amplitude of the scaling tip was measured via a scanning laser vibrometer (SLV). Increasing forces up to 1.0 N were applied either to the base of the tip (up through its center) or while it was loaded from the side. Displacement measurements were obtained using the SLV under these loading conditions. RESULTS: Under loading, there was a drop in displacement amplitude of all tips. Furthermore, loading of the tips resulted in large variations of displacement amplitudes recorded. The mean tip displacements recorded ranged from 10 to 30 microm when unloaded and 7 to 25 microm when loaded. The fundamental frequency of the ultrasonic tips' oscillation was at 30 kHz. However, loading resulted in the production of additional subharmonic frequencies in the region of 6 to 10 kHz. CONCLUSIONS: Thin ultrasonic scaler tips are susceptible to loading. This results in a reduction in the displacement amplitude that shows variation not only between tips of different design but also between those of the same design made by the same manufacturer. Clinicians and researchers should be aware of this variability, which may influence both clinical procedures and future research with thin ultrasonic scaling tips.

Dental Enamel↗
PubMed2002

Cord-like mosaic patches in the adrenal cortex are fractal: implications for growth and development.

Organogenesis proceeds rapidly and faithfully during fetal development. The process includes generation of parenchyma, followed by organization into functional tissues. The method by which the growth of organ parenchyma is regulated is not known, but insight into this regulation has been obtained by studying mosaic tissues of experimental chimeras and transgenic mosaics. The patterns revealed by this procedure offer an indication of how the parenchyma was generated. In the liver, the pattern appears as islands of one cell type in a sea of the other cell type, while in the adrenal cortex the pattern is one of alternating cords of one cell type adjacent to the other cell type. We have established previously that mosaic patches in the liver are fractal. The fractal dimensions of patches in the liver are consistent with an iterative, recursive growth model with simple stereotypical division rules. Here we report that the patches in mosaic adrenal cortex of the mouse and rat are also fractal and that the fractal dimension of the surface of the patches is lower than that in the liver. Fetal development and fractal dimensions of adrenal cortical mosaic patches are consistent with an algorithmic cell division model in which parenchymal growth is constrained to edges of growth centers forcing cord structures to form. Fractal analysis of the geometry of mosaic patches in tissues of experimental chimeras is helpful in constructing hypotheses of organ growth.

Adrenal Cortex↗
PubMed2002

Properties of encapsulated and hand-mixed zinc phosphate dental cement.

PURPOSE: Dental cements can be supplied as loose powder and liquid or as encapsulated syringes. This study assessed the compressive strength of a recently marketed zinc phosphate encapsulated cement compared with a hand-mixed system according to the American Dental Association Specification. MATERIALS AND METHODS: The mean fracture strength, standard deviations and associated Weibull Moduli (m) of the encapsulated and hand-mixed cements were determined by compressive fracturing 30 cylindrical specimens (height 6.0 +/- 0.1 mm, diameter 4.0 +/- 0.1 mm). Scanning electron microscopy was employed to assess crack growth from indentations and cement morphology. Image analysis was used to investigate the influence of mixing regime on pore distribution within the cement samples. RESULTS: The compressive strength data showed variation in magnitude and reliability ranging from 42 +/- 8 MPa (m = 5.2 +/- 1.0) for the encapsulated cement filled directly from the capsule to 71 +/- 11 MPa (m = 6.3 +/- 1.3) for the hand-mixed cement. The encapsulated cement matrix was extensively porous, consisting of pores between 0.1-0.5 microm diameter, compared with the non-porous hand-mixed cement matrix. Larger pores (over 18 microm diameter) were related to air entrapment in the encapsulated cement on mixing while small pores (0.1-0.5 microm diameter) were indicative of vaporization porosity commonly seen with exothermic reactions.

Air↗