scholarly journals Adhesion of a self-etching adhesive to caries-affected dentin treated with different methods for caries removal: a preliminary study

2016 ◽  
Vol 19 (4) ◽  
pp. 32
Author(s):  
Adriana Bona Matos ◽  
Cynthia Soares De Azevedo ◽  
Livia Tosi Trevelin ◽  
Ana Cecília Correa Aranha
Keyword(s):  
Energy Density ◽  
Bond Strength ◽  
Nd:Yag Laser ◽  
Er:Yag Laser ◽  
Laser Energy ◽  
Laser Energy Density ◽  
Bonding Performance ◽  
Significant Difference ◽  
Caries Removal ◽  
Etching System

<p><strong>Objective</strong>: The aim of this study was to evaluate the adhesion of a self-etching system to caries-affected dentin (CAD) and sound dentin (SD) after different caries removal techniques by using microtensile bond strength test (μTBS). <strong>Materials</strong> <strong>and</strong> <strong>Methods</strong>: Twenty-four extracted human molars with coronal carious lesions were used. The samples were randomly divided into 5 groups, according to caries removal method: G1 - negative control (no removal); G2 abrasive disc; G3 – slow speed steel bur; G4 - Nd:YAG laser (energy density 21.2J/cm<sup>2</sup>); G5 - Er:YAG laser (energy density 80.24J/cm<sup>2</sup>). SD and  CAD/ infected dentin substrates were tested.  Self-etch system (Clearfil SE Bond) was applied and resin crowns were built up. <strong>Results</strong>: One-way ANOVA showed statistically significant difference between experimental groups (p&lt;0.001), with significantly lower results for infected dentin (G1), when compared to all other experimental groups. A statistically significant higher bond strength value was observed for SD irradiated with Er:YAG laser when compared to CAD. For bur and Nd:YAG laser specimens, SD and CAD showed the same bonding performance. <strong>Conclusion</strong>: infected dentin is not an adequate substrate for bonding; Nd:YAG laser and steel burs showed the same bonding performance for both SD and CAD; while both dentins, when irradiated by Er:YAG laser, did not adequately interact with self-etching system resulting in poor adhesion.</p><p><strong>Keywords</strong>: Er:YAG laser; Nd:YAG laser; Infected dentin; Dentin.</p>

Fundamentals of radiation heat transfer in AlSi10Mg powder bed during selective laser melting

2019 ◽  
Vol 25 (9) ◽  
pp. 1506-1515 ◽  
Author(s):  
Pei Wei ◽  
Zhengying Wei ◽  
Zhne Chen ◽  
Jun Du ◽  
Yuyang He ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Energy Density ◽  
Negative Impact ◽  
Laser Energy ◽  
Melting Process ◽  
Laser Energy Density ◽  
Granular System ◽  
Laser Melting ◽  
Content Type ◽  
Powder Bed

Purpose This paper aims to study numerically the influence of the applied laser energy density and the porosity of the powder bed on the thermal behavior of the melt and the resultant instability of the liquid track. Design/methodology/approach A three-dimensional model was proposed to predict local powder melting process. The model accounts for heat transfer, melting, solidification and evaporation in granular system at particle scale. The proposed model has been proved to be a good approach for the simulation of the laser melting process. Findings The results shows that the applied laser energy density has a significantly influence on the shape of the molten pool and the local thermal properties. The relative low or high input laser energy density has the main negative impact on the stability of the scan track. Decreasing the porosity of the powder bed lowers the heat dissipation in the downward direction, resulting in a shallower melt pool, whereas pushing results in improvement in liquid track quality. Originality/value The randomly packed powder bed is calculated using discrete element method. The powder particle information including particle size distribution and packing density is taken into account in placement of individual particles. The effect of volumetric shrinkage and evaporation is considered in numerical model.

Laser-Triggered Surface Flashover Characteristics of Al2O3 in Pulsed Voltage

2011 ◽  
Vol 354-355 ◽  
pp. 1224-1227
Author(s):  
Ru Zheng Pan ◽  
You Hua Wang ◽  
Min Tang Li ◽  
Ling Ling Pang ◽  
Jue Wang ◽  
...  
Keyword(s):  
Energy Density ◽  
Nd:Yag Laser ◽  
Delay Time ◽  
Laser Energy ◽  
Test System ◽  
Vacuum Condition ◽  
Surface Flashover ◽  
532 Nm ◽  
Time Decrease ◽  
Pulsed Voltage

Based on the platform of laser-triggered surface flashover in pulsed voltage, experiment of laser-triggered surface flashover is carried out in air and vacuum condition with pulsed voltage. A single/double harmonic, with wavelength of 1064/532 nm, Q-switched Nd:YAG laser is applied to trigger the surface flashover. The test system consists of flat electrodes and columned insulator. The material of electrode is copper and the material of insulator is Al2O3. Laser pulse’s wavelengths are 532nm and 1064nm, and laser is focused with rectangle. The results of experiment show that flashover delay time and jitter time decrease with increase of pulsed voltage or laser energy density, the delay time of 1064nm laser trigger is larger than that of 532nm laser trigger, and the delay time and jitter time in vacuum condition are less than the delay time and jitter time in air condition.

scholarly journals Impact of Intracoronal Dentin Treatment Prior to Bleaching on Bond Strength of Restorative Materials

2014 ◽  
Vol 25 (6) ◽  
pp. 519-523 ◽  
Author(s):  
Erica Moreno Zanconato-Carvalho ◽  
João Felipe Bruniera ◽  
Natália Spadini de Faria ◽  
Vivian Colucci ◽  
Danielle Cristine Messias
Keyword(s):  
Phosphoric Acid ◽  
Bond Strength ◽  
Surface Treatment ◽  
Shear Bond Strength ◽  
Composite Resin ◽  
Er:Yag Laser ◽  
Composite Resins ◽  
Bleaching Procedure ◽  
Significant Difference ◽  
Restorative Materials

Surface treatment of dentin before the bleaching procedure may affect its permeability and influence the bond strength of restorative materials. This study evaluated the influence of surface treatment before the bleaching on shear bond strength (SBT) of restorative materials to intracoronal dentin. Dentin slabs were subjected to surface treatment: no bleaching (control - CON), no surface treatment + bleaching (HP), 37% phosphoric acid + bleaching (PA) and Er:YAG laser + bleaching (L). After the bleaching procedure, specimens (n=10) were restored with: microhybrid composite resin (MH), flowable composite resin (F), and resin-modified glass-ionomer cement (RMGIC). The shear test was carried out. ANOVA and Tukey's test (α=0.05) showed significant difference for surface treatment and restorative materials (p<0.05). CON presented higher STB and was statistically different from HP (p<0.05). PA and L showed intermediate values and were statistically similar to CON and HP (p>0.05). STB for MH and F were higher than RMGIC (p<0.05), and did not differ from each other (p>0.05). The surface treatments with phosphoric acid and Er:YAG laser before the bleaching procedure provided shear bond strength at the same level of unbleached dentin and the composite resins presented superior bond strength to the intracoronal dentin.

Effects of laser energy density on in situ formation of nano-graphite

2019 ◽  
Vol 48 (5) ◽  
pp. 506004
Author(s):  
刘孝谦 Liu Xiaoqian ◽  
骆 芳 Luo Fang ◽  
杜琳琳 Du Linlin ◽  
陆潇晓 Lu Xiaoxiao
Keyword(s):  
Energy Density ◽  
Laser Energy ◽  
Laser Energy Density ◽  
In Situ Formation

Considerations for Large Area Fabrication of Integrated a-Si and Poly-Si TFTs

1994 ◽  
Vol 336 ◽  
Author(s):  
P. Mei ◽  
G. B. Anderson ◽  
J. B. Boyce ◽  
D. K. Fork ◽  
M. Hack ◽  
...  
Keyword(s):  
Grain Size ◽  
Energy Density ◽  
Laser Energy ◽  
Gate Insulator ◽  
Laser Energy Density ◽  
Laser Crystallization ◽  
Large Area ◽  
Low Leakage ◽  
Threshold Voltages ◽  
Excellent Method

ABSTRACTThe combination of a-Si low leakage pixel TFTs with poly-Si TFTs in peripheral circuits provides an excellent method for reducing the number of external connections to large-area imaging arrays and displays. To integrate the fabrication of the peripheral poly-Si TFTs with the a-Si pixel TFTs, we have developed a three-step laser process which enables selective crystallization of PECVD a-Si:H. X-ray diffraction and transmission electron microscopy show that the polycrystalline grains formed with this three-step process are similar to those crystallized by a conventional one step laser crystallization of unhydrogenated amorphous silicon. The grain size increases with increasing laser energy density up to a peak value of a few Microns. The grain size decreases with further increases in laser energy density. The transistor field effect mobility is correlated with the grain size, increasing gradually with laser energy density until reaching its maximum value. Thereafter, the transistors suffer from leakage through the gate insulators. A dual dielectric gate insulator has been developed for these bottom-gate thin film transistors to provide the correct threshold voltages for both a-Si and poly-Si TFTs.

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