Search results for "Magnification"
showing 10 items of 88 documents
Mathematical analysis of projection errors in “paralleling technique” with respect to implant geometry
2001
Abstract: “Standardized” radiographs acquired in paralleling technique serve for monitoring of marginal bone levels around endosseous implants. Under clinical conditions, parallel adjustment of the film to the implant is beset with great difficulties. A mathematical model matching clinical conditions was developed to evaluate projection geometry within an interval of clinically relevant angulations (± 10° from parallel position). Radiographs of two implants (Frialit 2, Friadent AG, Mannheim, Germany; Implant No. 1: ∅ 3.8 mm, length 10 mm; Implant No. 2: ∅ 6.5 mm, length 13 mm) were separately produced per angulation (2° increments) at one focus-object distance (FO=322.9 mm). Implant images …
New, fast, and accurate procedure to calibrate a 2-dimensional digital measurement method.
2005
Traditionally, dental casts have been measured by hand, with conventional calipers. Today, several digital methods are available for automatically measuring tooth size, but their accuracy depends on proper calibration. The purpose of this article is to introduce a fast and accurate procedure to calibrate a previously introduced 2-dimensional computerized system of measuring mesiodistal tooth size and calculating overall and anterior Bolton ratios. In this calibration method, the cast is digitized while sitting on a sheet of graph paper. The magnification of the paper in 2 axes can be easily calculated and hence the magnification of the dental cast digital image.
Contamination by trace metals and their trophic transfer to the biota in a Mediterranean coastal system affected by gull guano
2013
Transitional environments are vulnerable interface systems, ecologically connected with adjacent systems by several biotic or abiotic flows. The coastal system of the Marinello ponds (Tyrrhenian Sea, Italy) is affected by a colony of yellow-legged gulls Larus michahellis (Naumann, 1840), resident on the cliff beside the ponds. To investigate the role of the gull colony as a potential source of allochthonous non-essential trace metals (As, Cd, Pb and total mercury, THg) and the consequent metal trophic transfer to the biota in the ponds, we collected guano, surface sediment and biota from 3 ponds with different levels of avian input. The highest concentrations were observed in guano and surf…
Evaluation of the time required to perform three retreatment techniques with dental microscope and ultrasonic activation for removing filling materia…
2018
Background When endodontic treatment fails, retreatment consists of the complete removal of the root canal filling material for thorough cleaning and reobturation. Various techniques are available for the filling removal procedure, which present varying degrees of efficacy, and take a varying length of time to perform. The aim of this study was to compare the time required to carry out reciprocating, rotary, and manual techniques with dental microscope and ultrasonic activation for removing filling material from root canals. Material and Methods Ninety-nine extracted single-rooted teeth with straight and oval-shaped canals were selected. The samples were instrumented with ProTaper Gold Syst…
Optical magnification has no benefits on the detection of occlusal caries lesions in permanent molars using different visual scoring systems: An in v…
2020
Background Some studies have addressed the influence of optical magnification on the detection of caries lesions using a visual scoring system. However, there is a lack of research related to the use of the CAST and ADA-CCS visual scoring systems. In addition, the reliability and accuracy of ADA-CCS index in permanent teeth were not studied yet. So, the aim of this study was to evaluate, in vitro, the influence of different levels of optical magnification on the detection of occlusal caries lesions in permanent molars using three visual scoring systems. Material and Methods One occlusal site per tooth was analyzed in 120 extracted permanent molars. Two trained examiners inspected the teeth …
Assessment of non-carious root surface defects in areas of gingival recession: A descriptive study.
2015
BACKGROUND The purpose of this descriptive study was to observe the distribution of four different classes of non-carious cervical root surface discrepancies in teeth with gingival recession. Additionally to explore the different treatment modalities in the literature for each of these defects. MATERIAL AND METHODS A total of 150 subjects with at least one labial gingival recession were included in the study. 1400 teeth were evaluated using 2.5 X magnification loupes and UNC -15 probe for the presence of the cemento-enamel junction and step like defects according to Pini-Prato's classification: A-, identifiable CEJ without defect; A+, identifiable CEJ with defect; B-, unidentifiable CEJ wit…
Perception of Biological Motion in Central and Peripheral Visual Fields
2017
Abstract Studies analysing biological motion perception based on reduced number of dots have demonstrated that biological motion can be perceived even when only the lower part of the body is visible or when the number of dots representing the object is reduced. What is the minimal amount of information that enables biological motion to be distinguished from its scrambled version? The results of the current experiment demonstrate that biological motion can be distinguished from its scrambled version when the object is formed of approximately 5 (4.7 ± 0.1) dots. Additionally, we also investigated whether the threshold value for biological motion perception differs in central and peripheral vi…
Vulnerability of different nerves to intrafascicular injection by different needle types and at different approach angles: a mathematical model
2019
Background and objectivesWe assume that intrafascicular spread of a solution can only occur if a large enough portion of the distal needle orifice is placed inside the fascicle. Our aim is to present and evaluate a mathematical model that can calculate the theoretical vulnerability of fascicles, analyzing the degree of occupancy of the needle orifice in fascicular tissue by performing simulations of multiple positions that a needle orifice can take inside a cross-sectional nerve area.MethodsWe superimposed microscopic images of two routinely used nerve block needles (22-gauge, 15° needle and 22-gauge, 30° needle) over the microscopic images of cross-sections of four nerve types photographed…
Landmark identification on direct digital versus film-based cephalometric radiographs: A human skull study
2002
The purpose of this study was to investigate differences in landmark identification on vertically scanned, direct digital and conventional (18 x 24 cm) cephalometric radiographs. Eight observers, all orthodontists or postgraduate orthodontic students, recorded 6 landmarks twice on 3 digital and 3 conventional cephalograms obtained from 3 human skulls in a standardized fashion. Digital images were displayed on a 15.1-in TFT monitor in 3:1 mode (20 x 26 cm). Recordings were transferred into standardized coordinate systems and evaluated separately for each coordinate. After correcting for magnification, precision was assessed with Maloney-Rastogi tests, and intraobserver and interobserver repr…
Lateral magnification matrix from the dioptric power matrix formalism in the paraxial case.
2012
Background Previous studies have highlighted that power matrices fully characterize the concept of dioptric power of any astigmatic surface. Thus, the basic equations in physiological optics can be generalized using the matrix formalism of the dioptric power. Among others, lateral magnification has also been interpreted as a matrix but mainly concerning magnification modification induced by spectacle correction of refractive error. Purpose To provide a fresh look into a novel paraxial formulation for the assessment of the lateral magnification using power matrices and in presence of astigmatism for thin and thick imaging systems in general. Methods Linear optics provides the frame to genera…