424 research outputs found
Measurements of minimum bias events, underlying event and particle production properties in ATLAS
The measurements of the minimum bias events provide valuable information on
the basic properties of the interactions. The results at the new highest
energy of collisions, = 13 TeV, obtained using the ATLAS
detector, are shown. They include distributions of charged particle
pseudorapidity density, transverse momentum and multiplicity. The properties of
the underlying event, determined with respect to a leading high-
particle, are also presented. In both cases the new results are compared with
those from earlier studies of the collisions at = 7 TeV.Comment: Proceedings of the 23rd Low-x Meeting, Sandomierz, Poland, September
1-5, 2015, 11 pages, 11 figure
Automatic method of analysis of OCT images in the assessment of the tooth enamel surface after orthodontic treatment with fixed braces
Introduction: Fixed orthodontic appliances, despite years of research and
development, still raise a lot of controversy because of its potentially destructive
influence on enamel. Therefore, it is necessary to quantitatively assess the condition
and therein the thickness of tooth enamel in order to select the appropriate
orthodontic bonding and debonding methodology as well as to assess the quality
of enamel after treatment and clean-up procedure in order to choose the most
advantageous course of treatment. One of the assessment methods is computed
tomography where the measurement of enamel thickness and the 3D reconstruction
of image sequences can be performed fully automatically.
Material and method: OCT images of 180 teeth were obtained from the Topcon
3D OCT-2000 camera. The images were obtained in vitro by performing sequentially
7 stages of treatment on all the teeth: before any interference into enamel, polishing
with orthodontic paste, etching and application of a bonding system, orthodontic
bracket bonding, orthodontic bracket removal, cleaning off adhesive residue. A dedicated
method for the analysis and processing of images involving median filtering,
mathematical morphology, binarization, polynomial approximation and the active
contour method has been proposed.
Results: The obtained results enable automatic measurement of tooth enamel
thickness in 5 seconds using the Core i5 CPU M460 @ 2.5GHz 4GB RAM. For one
patient, the proposed method of analysis confirms enamel thickness loss of 80 μm
(from 730 ± 165 μm to 650 ± 129 μm) after polishing with paste, enamel thickness loss
of 435 μm (from 730 ± 165 μm to 295±55 μm) after etching and bonding resin
application, growth of a layer having a thickness of 265 μm (from 295 ± 55 μm to
560 ± 98 μm after etching) which is the adhesive system. After removing an
orthodontic bracket, the adhesive residue was 105 μm and after cleaning it off, the
enamel thickness was 605 μm. The enamel thickness before and after the whole
treatment decreased by about 125 μm.
Conclusions: This paper presents an automatic quantitative method for the
assessment of tooth enamel thickness. This method has proven to be an effective
diagnostic tool that allows evaluation of the surface and cross section of tooth enamel
after orthodontic treatment with fixed thin-arched braces and proper selection of the
methodology and course of treatment
Enamel Thickness before and after Orthodontic Treatment Analysed in Optical Coherence Tomography
Despite the continuous development of materials and techniques of adhesive bonding, the basic procedure remains relatively constant. The technique is based on three components: etching substance, adhesive system, and composite material. The use of etchants during bonding orthodontic brackets carries the risk of damage to the enamel. Therefore, the article examines the effect of the manner of enamel etching on its thickness before and after orthodontic treatment. The study was carried out in vitro on a group of 80 teeth. It was divided into two subgroups of 40 teeth each. The procedure of enamel etching was performed under laboratory conditions. In the first subgroup, the classic method of enamel etching and the fifth-generation bonding system were used. In the second subgroup, the seventh-generation (self-etching) bonding system was used. In both groups, metal orthodontic brackets were fixed and the enamel was cleaned with a cutter fixed on the micromotor after their removal. Before and after the treatment, two-dimensional optical coherence tomography scans were performed. The enamel thickness was assessed on the two-dimensional scans. The average enamel thickness in both subgroups was not statistically significant
- …