High-speed scanning ablation of dental hard tissues with a λ=9.3-μm CO 2 laser: heat accumulation and peripheral thermal damage

2010 ◽  
Author(s):  
Daniel Nguyen ◽  
Michal Staninec ◽  
Chulsung Lee ◽  
Daniel Fried
Keyword(s):  
High Speed ◽  
Thermal Damage ◽  
Heat Accumulation ◽  
Laser Heat ◽  
Dental Hard Tissues ◽  
Hard Tissues

scholarly journals High-speed scanning ablation of dental hard tissues with a λ = 9.3 μm CO2 laser: adhesion, mechanical strength, heat accumulation, and peripheral thermal damage

2011 ◽  
Vol 16 (7) ◽  
pp. 071410 ◽  
Author(s):  
Daniel Nguyen ◽  
Kwang Chang ◽  
Saba Hedayatollahnajafi ◽  
Michal Staninec ◽  
Kenneth Chan ◽  
...  
Keyword(s):  
Mechanical Strength ◽  
Co2 Laser ◽  
High Speed ◽  
Thermal Damage ◽  
Heat Accumulation ◽  
Dental Hard Tissues ◽  
Hard Tissues

The Effect of CO2Laser on the Microhardness of Human Dental Hard Tissues Compared with That of the High-Speed Drill

2008 ◽  
Vol 26 (1) ◽  
pp. 65-68 ◽  
Author(s):  
Iris Slutzky-Goldberg ◽  
Oren Peleg ◽  
Reuven Liberman ◽  
Adam Stabholtz ◽  
Joshua Moshonov
Keyword(s):  
High Speed ◽  
Dental Hard Tissues ◽  
Hard Tissues

Variation in the Changes Induced by Different Forms of Tobacco in Dental Hard Tissues-A SEM-EDAX Study

2011 ◽  
Vol 53 (4) ◽  
pp. 348-355
Author(s):  
Thakare Eesha ◽  
Chaudhary Minal ◽  
Gawande Madhuri ◽  
Wadhwan Vijay ◽  
Gadbail Amol
Keyword(s):  
Dental Hard Tissues ◽  
Hard Tissues

Accelerating laser processes with a smart two-dimensional polygon mirror scanner for ultra-fast beam deflection

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Florian Roessler ◽  
André Streek
Keyword(s):  
Energy Distribution ◽  
Real Time ◽  
Laser Processing ◽  
High Speed ◽  
Beam Deflection ◽  
Two Dimensional ◽  
Heat Accumulation ◽  
Field Programmable ◽  
Drill Holes ◽  
Average Laser

Abstract In laser processing, the possible throughput is directly scaling with the available average laser power. To avoid unwanted thermal damage due to high pulse energy or heat accumulation during MHz-repetition rates, energy distribution over the workpiece is required. Polygon mirror scanners enable high deflection speeds and thus, a proper energy distribution within a short processing time. The requirements of laser micro processing with up to 10 kW average laser powers and high scan speeds up to 1000 m/s result in a 30 mm aperture two-dimensional polygon mirror scanner with a patented low-distortion mirror configuration. In combination with a field programmable gate array-based real-time logic, position-true high-accuracy laser switching is enabled for 2D, 2.5D, or 3D laser processing capable to drill holes in multi-pass ablation or engraving. A special developed real-time shifter module within the high-speed logic allows, in combination with external axis, the material processing on the fly and hence, processing of workpieces much larger than the scan field.

Primary Teeth and Hair as Indicators of Environmental Pollution

2016 ◽  
Vol 40 (2) ◽  
pp. 152-155 ◽  
Author(s):  
TE Shishniashvili ◽  
NN Suladze ◽  
VV Margvelashvili
Keyword(s):  
Environmental Pollution ◽  
Toxic Elements ◽  
Chemical Elements ◽  
Epidemiological Survey ◽  
Essential Elements ◽  
World Health ◽  
Dental Tissues ◽  
Dental Hard Tissues ◽  
Hard Tissues ◽  
Health Organization

Objectives: To study the influence of environmental pollution on the mineralization of dental hard tissues by using biosubstrates: teeth and hair. :Study design: At the first stage epidemiological survey was conducted in polluted and less polluted areas of Tbilisi (Georgia). We studied 525 children aged 3 and 4 years. Caries prevalence and intensity was defined by the methodology of World Health Organization. At the second stage the chemical elements content was studied in hair and teeth hard tissues of 24 children by X - ray fluorescent spectroscopy method. Results: The prevalence of dental caries in the polluted region was 46%, caries intensity − 1.92 (± 2.842). In the less polluted region prevalence was 37%, caries intensity − 1.47 (± 2.571). These data are statistically reliable (p < 0.05). The study of hair and tooth tissues showed that the toxic elements (Pb, Hg, Sn, Ti) content in these tissues was higher in environmentally unfavorable than in favorable conditions. Conclusion: Hair and dental tissues can be used as indicators of environmental pollution. Our survey showed that toxic elements content in dental hard tissues was higher and the level of essential elements was less in polluted than in less polluted areas of Tbilisi.

Thermal failure mechanism of fiber ropes when bent over sheaves

2018 ◽  
Vol 89 (7) ◽  
pp. 1215-1223
Author(s):  
Fanggang Ning ◽  
Xiaoru Li ◽  
Nick O Hear ◽  
Rong Zhou ◽  
Chuan Shi ◽  
...  
Keyword(s):  
Failure Mechanism ◽  
Thermal Damage ◽  
Synthetic Fiber ◽  
Heat Accumulation ◽  
Thermal Failure ◽  
Synthetic Fibers ◽  
Test Conditions ◽  
Bending Process ◽  
Higher Temperature ◽  
Bending Failure

Thermal damage is an important failure mechanism that affects the bending failure of fiber ropes. This is relevant because synthetic fibers often have a relatively low melting point and low thermal conductivity. In cyclic bending over sheave (CBOS), the heat generated by friction and deformation is not conducted rapidly to the external environment, and the temperature of the rope core increases quickly. This higher temperature greatly reduces the mechanical properties of the fiber, thus accelerating the final rope failure. In this paper, evidence of thermal damage in the bending process of a braided synthetic fiber rope is given. The test conditions inducing thermal damage are discussed, including stress level, bending frequency and diameter ratio. The reasons for the heat generation and the dynamic process of heat accumulation inside the rope during CBOS are also discussed. This study aims to provide theoretical and experimental guidance for the design and use of fiber rope.

scholarly journals In Vitro Assessment of Erosive Effects of Some Common Soft Drinks on Dental Hard Tissues

2019 ◽  
Vol 23 (3) ◽  
pp. 132-140
Author(s):  
Enea Bitri ◽  
Lucian Petcu ◽  
Gabriela Mocanu ◽  
Doina Paula Balaban
Keyword(s):  
Weight Loss ◽  
Titratable Acidity ◽  
Soft Drinks ◽  
Hard Tissue ◽  
Time Exposure ◽  
Prolonged Time ◽  
Dental Hard Tissue ◽  
Dental Hard Tissues ◽  
Hard Tissues ◽  
Erosive Effect

Summary Background/Aim: The chemical nature of soft drinks is acidic, so they possess the capacity to cause hard tissue erosion. The aim of this study is to assess the potentially erosive effect linked to pH and titratable acidity of some common soft drinks on dental hard tissues in prolonged time exposure. Material and Methods: Seven types of soft drinks in Romanian market were selected for this study. The pH and Titratable acidity were determined. Twenty one human dental hard tissue specimens were immersed in 5 ml solution each for 336h. Every 48h weight loss was determined for each specimen and after 336h volume changes were calculated. Enamel microhardness was determined using a Microhardness Tester model HV-1000 and compared to normal enamel microhardness. Results: The pH values of beverages ranged from 2.37 to 3.1, showing no significant differences. All specimens presented color and surface texture modifications, weight loss and volume reduction. There were found significant differences between the mean values of weight loss and enamel microhardness of each type of specimens and type of beverages tested. The most representative findings were achieved by indentations done in specific zones on Sprite® immersed specimen. This result suggest that microhardness near the eroded surface was significant lower than in other zones. Conclusions: Data obtained have shown that all the soft drinks tested had an erosive effect, causing dental hard tissue dissolution. For prolonged time exposure titratable acidity may be a major predictor for erosive potential. Dental erosion may affect different levels of enamel causing decreased enamel microhardness.

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