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The Efficiency of Endodontic Retreatment through Direct Crown Access Mugur-George Popescu1,a, Diana Marian1,b*, Teodora Ştefănescu2,c, Aurora Antoniac3,d,Teodora Eva Lucaciu Lupulescu1,e, Radu Elisei1,f, Elisabeta Vasca1,g 1Faculty of Dental Medicine, Vasile Goldiş Western University, Bd Revolutiei no. 94, Arad, Romania 2Department of Dentistry, University of Oradea, Piata 1 Decembrie no.10, Oradea, Romania 3Faculty of Materials Science and Engineering, University Politehnica of Bucharest, Splaiul Independentei no. 313, district 6, Bucuresti, Romania agugupopescu@yahoo.com, bdr.diana.marian@gmail.com (corresponding author), cprestigedent@yahoo.com, dantoniac.aurora@gmail.com, eteodora_lupulescu@yahoo.com, felisei_gabriela@yahoo.com, gelisabeta.vasca@yahoo.com Keywords: endodontic retreatment, periapical index, crown access Abstract.
Materials and Methods From 2012 to 2016, 148 patients, with ages ranging from 18 to 65, were retreated endodontically. 74 treatments were performed through mechanical rotary treatment, and the other 74 through reciprocal mechanical treatment.
They are being used in crown-down technique, only for soluble material removal.
Multivisit Treatment, Journal of Endodontics, 25(5) (1999) 345-350
[4] Thomas M.B.M., Hayes S.J., Gilmour A.S.M., Radiographic evidence of postoperative healing 12 years following root canal treatment – a case report, British Dental Journal 203(8) (2007) 635 – 639

Experimental procedure Experiments were performed with surface grinder M7120 and workpiece material 45 steel.
Residual compressive stresses are considered beneficial for the mechanical properties of materials, increasing their fatigue strength and the service life of components.
Acknowledgements This research were financially supported by the National Natural Science Foundation of China (Grant No. 50475052) and the Specialized Research Fund for the Doctoral Program of Higher Education (Grant No. 20040145001) Fig.6 The cross-section microcosmic structure of 45 steel for conventional grinding and MQL grinding (a) Conventional grinding (b) MQL grinding Fig.7 Measured result for residual stress -400 -200 0 Residual stress σ/MPa Conventional grinding MQL grinding Fig.8 Machined surface hardness change with depth References [1] Sun-Kyu Lee, Yuji Miyamoto, Tsunemoto Kuriyagawa: International Journal of Machine Tools & Manufacture Vol. 44 (2004), p. 1031 [2] S.
Tridimas: International Journal of Machine Tools & Manufacture Vol. 40 (2000), p. 209 [3] Leonardo Roberto da Silva: International Journal of Machine Tools & Manufacture Vol. 47 (2007), p. 412 [4] Li Changhe, Cai Guangqi, Xiu Shichao: Acta Armamentarii Vol. 28 (2007), p. 202 [5] U.
Walter: Machines and Metals Magazine Vol. 386 (1998), p. 22 [6] Li Changhe,Meng Guangyao,Cai Guangqi: Journal of Qingdao technological university, Vol.28(2) (2007), p. 6 [7] Li Changhe, Xiu Shichao, Cai Guangqi: Advanced Materials Research, Vols. 24-25 (2007), p. 337

Altintas, and E.J.A: Journal of Manufacturing Science and Engineering(1996), No. 118, p.216-224
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For example, Paper [3] is recommended by many papers published at the SCI journals.
The natural circular frequency and mode shape of the beam satisfy the following equation: , (1) where is the flexural stiffness, in which is the Young’s modulus and is the moment of inertia of the cross section; is the material density and is the area of the cross-section; is the eigenvalue.
Acknowledgment This work is supported by National Natural Science Foundation of China (No: 10772001).
Candan, Apparently first closed-form solution for vibrating: inhomogeneous beams, International Journal of Solids and Structures, 38(2001), p. 3411 [2] I.
Candan，Apparently first closed-form solution for frequencies of deter ministically and/or stochastically inhomogeneous simply supported beams, Journal of Applied Mechanics, 68(3) (2001), p. 176 [3] Lei Wu, Qi-shen Wang, I.

Experimental Study on Friction and Wear Between Drill Collar and Casing Bensheng Huang1, 2, a* and Yao Zhu2, b 1State Key Lab of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China 2School of Materials Science and Engineering of Southwest Petroleum University, Chengdu 610500, China ahbslxp@163.com, b513262229@qq.com Keywords: Friction, Wear, Drill collar, Casing.
The results showed that the materials of drill collar and casing after different heat treatment had varying degrees of wear, both of the respective wear amounts were gradually increasing with the increase of hardness of them, the wear extent of casing material was greater than that of drill collar material.
Direct-reading spectrograph and metallographic microscope were used to analyze the chemical composition and internal organization of the materials of casing and drill collar, and then the Rockwell hardness tester was carried out to measure the surface hardness of materials of casing and drill collar.
The heat treatment process of materials of casing and drill collar is quenching and tempering.
Zhu, Models & tests of casing wear in drilling for oil & gas, Journal of natural gas science and engineering, 4(2012)44-47 [2] C.J.

It is suitable for processing hard and brittle materials, complex cavity.
Experiments have been done on Ceramic materials by rotary ultrasonic face milling(RUFM) process by Z.J.
Wei: Journal of Materials Processing Technology, Vol. 120 (2002) No. 1, pp. 101-106
Jiao: Journal of Materials Processing Technology , Vol. 129 (2002) No. 1, pp. 196-199
Kuo: Journal of Materials Processing Technology, Vol. 201 (2008) No. 1, pp. 48-52

By using NVP, it can be obtained many high performance polymer materials, such as polyvinylpyrrolidone (PVP), which has a good biocompatible feature [3].
Experimental content Materials Xanthan gum was purchased from Shandong Fufeng Fermentation Co., Ltd and Tea Polyphenol (TP) was brought from Fuzhou Corona Science & Technology Development CO, Ltd.
Journal of Chemical Industry and Engineering (China). 2005, 56(9):1783-1788
Journal of ShanXi University of Science and Technoloty. 2007(2):1-4
Materials Review. 2005(6): 73-75

Especially the residua after treatment are still pollutants or hazard materials, which need further subsequent treatment.
Temperature was controlled within ±2℃ from a desired temperature by temperature controller(XMT6000, Ninbo Yangming Electromechanically Co.Ltd）.The reacting temperature was measured and continuously recorded by using thermocouple (WRN, 0-1300℃).The pressure was controlled by a back pressure regulator and was measured by a digital gauge(YCD-02A,Anhui Jinda Instrument Co.Ltd ). 1-waste water container；2-high pressure pump；3- reactor； 4-nitrogen cylinder；5-oxygen cylinder；6-cooler； 7-gas and liquid separator；8-heater；9- water inlet valve 10- gas inlet valve；11—discharge water valve；12-pressure gauge；13-thermometer；14,15-relief valve Fig. 1 Process chart of SCWO Materials There were two types of wastewater in the research.One was TNT simulation wastewater prepared in laboratory.The other was the actual effluent from a TNT manufacturing plant .
References [1] D.L.Pugh,USATHAMA Report DRXTH-FR-8213US.Aberdeen，MD，1982 [2] R.F.Spaulding, J.W.Fulton, J.Contaminant Hydrol.2 (9) (1988)139-153 [3] Chitra Rajagopal, J.C.Kapoor.Journal of Hazardous Materials B87 (2001)73-98 [4] Kaplan, D.L.
P.Marinkas(Ed), Nova Science Publishers, NewYork, 1996, pp.373-416 [5] Nijs Jan Duijm, Frank Markert.Journal of Hazardous Materials A90 (2002)137-153 [6] Kubose D.A. and Hoffsommer J.C.
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Journal of Applied Engineering Science, Vol. 12 (2) (2014), pp 121-128 [9] D.
Applied Mechanics and Materials.
Applied Mechanics and Materials.
Applied Mechanics and Materials.
Applied Mechanics and Materials.

Introduction Nanostructured zinc oxide (ZnO) is one of the most promising semiconductor materials for applications in solar cells, and various sensors [1-5].
Then, Al-doped ZnO nanorod arrays were coated with intrinsic ZnO (4-inch ZnO target: purity 99.99 %; Process Materials Inc.) using radio-frequency (RF) magnetron sputtering (SNTEK) at an RF power of 50 W, before annealing in air at 500 °C for 1 h.
Rusop, Fabrication of thin, dense and small-diameter zinc oxide nanorod array-based ultraviolet photoconductive sensors with high sensitivity by catalyst-free radio frequency magnetron sputtering, Materials Letters 93 (2013) 215-218 [4] M.
Mahmood, Effects of Annealing Environments on the Solution-Grown, Aligned Aluminium-Doped Zinc Oxide Nanorod-Array-Based Ultraviolet Photoconductive Sensor, Journal of Nanomaterials 2012 (2012) 15 [7] M.
Rusop, Influence of doping concentrations on the aluminum doped zinc oxide thin films properties for ultraviolet photoconductive sensor applications, Optical Materials 32 (2010) 696-699 [11] J.