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Sekar Abinaya,Mariappan Saravanakumar,Krishnan Chitra Shankar,Sampathkumar Jayakrishnakumar,Ramakrishnan Hariharan,Mahadevan Vallabh,Sivaprakasam Azhagarasan Nagarasampatti 대한치과이식(임프란트)학회 2022 The Korean Academy of Implant Dentistry Vol.41 No.4
Purpose: This study compared the accuracy of different elastomeric impression materials with open tray implant level impression technique in a single-tooth replacement. Materials and Methods: A reference model representing a single implant with an adjacent simulated natural tooth was fabricated. Open tray implant level impressions were made with vinylpolysiloxane (light body ExpressXT, PentaputtyPentamix2, 3MESPE, Seinfield, Germany) (Group I, n=10) and polyether (medium body Impregnum Penta, Pentamix 2, 3MESPE, Seinfield, Germany), (Group II, n=10) and implant crowns were fabricated on each master cast from their respective impressions by CNC milling and connected to the reference model with 35 Ncm torque. The accuracy of the fit was evaluated by measuring the interface gap between the implant crown and the implant replica at the mesial and distal points and by measuring the proximal gap between the implant crown and the simulated natural tooth at the buccal and the palatal points by scanning electron microscopy for each test sample. The mean values were obtained and statistically analyzed using a Mann-Whitney test. Results: The interface gap observed at the mesial point was significantly higher than the distal point. The proximal gap observed at the palatal point was significantly higher than the buccal point for both Group I and Group II. A comparison of the groups showed that the interface gap at the mesial point and the proximal gap at the buccal and palatal points obtained from polyether impression material were lower than those observed with vinylpolysiloxane group, but the difference was not significant. However, the interface gap observed at the distal point was higher with the polyether group than with the vinylpolysiloxane group, but the difference was not significant. Conclusions: Polyether and vinylpolysiloxane can be used to produce open tray implant impressions for a single missing tooth.
An Integrated Approach to the Improvement of Stability Lobes
Sekar Mohan,Srinivas Jonnalagadda,Namcheol Kang,Seung-Han Yang 한국정밀공학회 2008 International Journal of Precision Engineering and Vol.9 No.4
Redundant spurious loops and overlapping segments in stability lobe diagrams cannot be removed easily by regular methods. A programmatic approach is presented to detect multiple spurious loops occurring within the lobes. They are identified by reorganizing the numerical lobe data into speed-depth corners for subsequent removal. The same principle is then extended to remove overlapping segments of adjacent lobes to obtain a final continuous stability map. Unlike existing methods, the proposed methodology requires no interface with additional editing software, and can also yield stability lobe diagrams more quickly. The methodology is presented with lobe diagrams constructed using milling and turning models.
Sekar Vadhana,Jothi Latha,Natanasabapathy Velmurugan 대한치과보존학회 2015 Restorative Dentistry & Endodontics Vol.40 No.2
Objectives: This study evaluated the penetration depth of 2% chlorhexidine digluconate (CHX) into root dentinal tubules and the influence of passive ultrasonic irrigation (PUI) using a confocal laser scanning microscope (CLSM). Materials and Methods: Twenty freshly extracted anterior teeth were decoronated and instrumented using Mtwo rotary files up to size 40, 4% taper. The samples were randomly divided into two groups (n = 10), that is, conventional syringe irrigation (CSI) and PUI. CHX was mixed with Rhodamine B dye and was used as the final irrigant. The teeth were sectioned at coronal, middle and apical levels and viewed under CLSM to record the penetration depth of CHX. The data were statistically analyzed using Kruskal-Wallis and Mann-Whitney U tests. Results: The mean penetration depths of 2% CHX in coronal, middle and apical thirds were 138 μm, 80 μm and 44 μm in CSI group, respectively, whereas the mean penetration depths were 209 μm, 138 μm and 72 μm respectively in PUI group. Statistically significant difference was present between CSI group and PUI group at all three levels (p < 0.01 for coronal third and p < 0.001 for middle and apical thirds). On intragroup analysis, both groups showed statistically significant difference among three levels (p < 0.001). Conclusions: Penetration depth of 2% CHX into root dentinal tubules is deeper in coronal third when compared to middle and apical third. PUI aided in deeper penetration of 2% CHX into dentinal tubules when compared to conventional syringe irrigation at all three levels.
Parametric NURBS Curve Interpolators
Sekar Mohan,Sung-Hwan Kweon,Dong-Mok Lee,Seung-Han Yang 한국정밀공학회 2008 International Journal of Precision Engineering and Vol.9 No.2
Free-form shapes which were once considered as an aesthetic feature are now an important functional requirement. CNC industries are looking for a compact solution for reproducing free-form shapes as conventional interpolation models are inadequate. The parametric curve interpolator developed in the last decade has clearly emerged as favorite among its contemporaries in recent years. At present intense research has been done on parametric curve interpolators and interesting developments are reported. Out of the various parametric representations for curves and surfaces, NURBS has been standardized and widely used in free-form shape design. This paper presents a review of various methods of parametric interpolation for NURBS and discusses the salient features, problems and solutions. Recent approaches on variable feedrate interpolation, parameter compensation are also reviewed and research trends are addressed finally.
Growth and Characterization of GaN on Sapphire and Porous SWCNT Using Single Molecular Precursor
Sekar, P.V. Chandra,Lim, Hyun-Chul,Kim, Chang-Gyoun,Kim, Do-Jin Materials Research Society of Korea 2011 한국재료학회지 Vol.21 No.5
Due to their novel properties, GaN based semiconductors and their nanostructures are promising components in a wide range of nanoscale device applications. In this work, the gallium nitride is deposited on c-axis oriented sapphire and porous SWCNT substrates by molecular beam epitaxy using a novel single source precursor of $Me_2Ga(N_3)NH_2C(CH_3)_3$ with ammonia as an additional source of nitrogen. The advantage of using a single molecular precursor is possible deposition at low substrate temperature with good crystal quality. The deposition is carried out in a substrate temperature range of 600-750$^{\circ}C$. The microstructural, structural, and optical properties of the samples were analyzed by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and photoluminescence. The results show that substrate oriented columnar-like morphology is obtained on the sapphire substrate while sword-like GaN nanorods are obtained on porous SWCNT substrates with rough facets. The crystallinity and surface morphology of the deposited GaN were influenced significantly by deposition temperature and the nature of the substrate used. The growth mechanism of GaN on sapphire as well as porous SWCNT substrates is discussed briefly.
PANI-Based Wearable Electrochemical Sensor for real time Sweat pH Monitoring
Sekar Madhu(세카르 마두),Md. Sajjad Alam(Md. 사자드 알람),Jungil Choi(최정일) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
Sweat pH is an important health indicator related to metabolism and homeostasis level over hydrogen ion concentration in biological bio-fluid. Therefore, increasing research efforts have been motivated to develop wearable pH sensors towards continuous non-invasive monitoring of sweat pH values. A textile based skin-mounted microfluidic potentiometric device for electrochemical monitoring of pH in sweat is presented. The fabricated Polyaniline (PANI) incorporated carbon cloth (CC) pH sensor was tested in the range from 4 to 7, showing good behavior, with a sensitivity of 64.4 mV/pH, very close to a Nernstian response, better repeatability and good ion selectivity. Finally, a real sweat sample was collected, and the sweat pH was quantified with both the proposed sensor and a commercial pH meter, showing an excellent concordance. This soft skin-worn platform integrates potentiometric measurement, microfluidic technologies with flexible electronics for real-time wireless data transmission to mobile devices. The proposed device paves the way to build a novel practical fitness and health monitoring systems for improving practical fitness of human in real-time.