A noncontact measurement technique for the density and thermal expansion coefficient of solid and liquid materials

A noncontact measurement technique for the density and the thermal expansion coefficient of refractory materials in their molten as well as solid phases is presented. This technique is based on the video image processing of a levitated sample. Experiments were performed using the high-temperature electrostatic levitator (HTESL) at the Jet Propulsion Laboratory in which 2–3 mm diam samples can be levitated, melted, and radiatively cooled in vacuum. Due to the axisymmetric nature of the molten samples when levitated in the HTESL, a rather simple digital image analysis can be employed to accurately measure the volumetric change as a function of temperature. Density and the thermal expansion coefficient measurements were made on a pure nickel sample to test the accuracy of the technique in the temperature range of 1045–1565 °C. The result for the liquid phase density can be expressed by rho=8.848+(6.730×10^−4)×T (°C) g/cm^3 within 0.8% accuracy, and the corresponding thermal expansion coefficient can be expressed by beta=(9.419×10^−5) −(7.165×10^−9)×T (°C) K^−1 within 0.2% accuracy

An electrostatic levitator for high-temperature containerless materials processing in 1-g

This article discusses recent developments in high-temperature electrostatic levitation technology for containerless processing of metals and alloys. Presented is the first demonstration of an electrostatic levitation technology which can levitate metals and alloys (2–4 mm diam spheres) in vacuum and of superheating-undercooling-recalescence cycles which can be repeated while maintaining good positioning stability. The electrostatic levitator (ESL) has several important advantages over the electromagnetic levitator. Most important is the wide range of sample temperature which can be achieved without affecting levitation. This article also describes the general architecture of the levitator, electrode design, position control hardware and software, sample heating, charging, and preparation methods, and operational procedures. Particular emphasis is given to sample charging by photoelectric and thermionic emission. While this ESL is more oriented toward ground-based operation, an extension to microgravity applications is also addressed briefly. The system performance was demonstrated by showing multiple superheating-undercooling-recalescence cycles in a zirconium sample (Tm=2128 K). This levitator, when fully matured, will be a valuable tool both in Earth-based and space-based laboratories for the study of thermophysical properties of undercooled liquids, nucleation kinetics, the creation of metastable phases, and access to a wide range of materials with novel properties

Monodisperse, polymeric microspheres produced by irradiation of slowly thawing frozen drops

Monodisperse, polymeric microspheres are formed by injecting uniformly shaped droplets of radiation polymerizable monomers, preferably a biocompatible monomer, having covalent binding sites such as hydroxyethylmethacrylate, into a zone, impressing a like charge on the droplet so that they mutually repel each other, spheroidizing the droplets within the zone and collecting the droplets in a pool of cryogenic liquid. As the droplets enter the liquid, they freeze into solid, glassy microspheres, which vaporizes a portion of the cryogenic liquid to form a layer. The like-charged microspheres, suspended within the layer, move to the edge of the vessel holding the pool, are discharged, fall and are collected. The collected microspheres are irradiated while frozen in the cryogenic liquid to form latent free radicals. The frozen microspheres are then slowly thawed to activate the free radicals which polymerize the monomer to form evenly-sized, evenly-shaped, monodisperse polymeric microspheres

Unusual extraction treatment in Class II division 1 using C-orthodontic mini-implants.

AbstractThis paper describes the treatment of a female patient, aged 23 years and 5 months, with a Class II division 1 malocclusion, who showed severe anterior protrusion and lower anterior crowding. Specially-designed orthodontic mini-implants were placed bilaterally in the interdental space between both the upper and the lower posterior teeth. Both lower first molars showed severe apical lesions. Therefore, the treatment plan consisted of extraction of both upper first premolars and lower first molars, en masse retraction of the upper six anterior teeth, lower anterior alignment, and protraction of all the lower molars. C-implants® were used as substitutes for maxillary posterior anchorage teeth during anterior retraction and as hooks for mandibular molar protraction. The correct overbite and overjet were obtained by intruding and retracting the upper six anterior teeth into their proper positions. The dentition was detailed using conventional orthodontic appliances. The upper C-implants contributed to an improvement in facial balance, and the lower C-implants made it possible to protract the lower second and third molars with less effect on the axis of the lower anterior teeth. The active treatment period was 29 months and the patient's teeth continued to be stable 11 months after debonding

Computer-Aided Designing and Manufacturing of Lingual Fixed Orthodontic Appliance Using 2D/3D Registration Software and Rapid Prototyping

The availability of 3D dental model scanning technology, combined with the ability to register CBCT data with digital models, has enabled the fabrication of orthognathic surgical CAD/CAM designed splints, customized brackets, and indirect bonding systems. In this study, custom lingual orthodontic appliances were virtually designed by merging 3D model images with lateral and posterior-anterior cephalograms. By exporting design information to 3D CAD software, we have produced a stereolithographic prototype and converted it into a cobalt-chrome alloy appliance as a way of combining traditional prosthetic investment and cast techniques. While the bonding procedure of the appliance could be reinforced, CAD technology simplified the fabrication process by eliminating the soldering phase. This report describes CAD/CAM fabrication of the complex anteroposterior lingual bonded retraction appliance for intrusive retraction of the maxillary anterior dentition. Furthermore, the CAD/CAM method eliminates the extra step of determining the lever arm on the lateral cephalograms and subsequent design modifications on the study model

Severe bimaxillary protrusion with adult periodontitis treated by corticotomy and compression osteogenesis

This paper describes the case of a 50-year-old female with a Class 11 malocclusion who presented with severe bimaxillary protrusion and generalized alveolar bone loss due to adult periodontitis. The treatment plan consisted of extracting both upper and lower first premolars and periodontal treatment. Anterior segmental osteotomy (ASO) of the mandible and upper anterior segment retraction using compression osteogenesis after peri-segmental corticotomy (Speedy orthodontics) was performed. Correct overbite and overjet, facial balance, and improvement of lip protrusion were obtained. However, a slight root resorption tendency was observed on the lower anterior dentition. The active treatment period was 9 months and the results were stable for 27 months after debonding. This new type of treatment mechanics can be an effective alternative to orthognathic surgery. (Korean J Orthod 2009;39(1):54-65)This study was partly supported by the Korean Society of Speedy Orthodontics, Alumni fund of the Department of Dentistry and Graduate School of Clinical Dental Science, The Catholic University of Korea.1

The effects of different pilot-drilling methods on the mechanical stability of a mini-implant system at placement and removal: a preliminary study

Objective: To investigate the effects of different pilot-drilling methods on the biomechanical stability of self-tapping mini-implant systems at the time of placement in and removal from artificial bone blocks. Methods: Two types of artificial bone blocks (2-mm and 4-mm, 102-pounds per cubic foot [102-PCF] polyurethane foam layered over 100-mm, 40-PCF polyurethane foam) were custom-fabricated. Eight mini-implants were placed using the conventional motor-driven pilot-drilling method and another 8 mini-implants were placed using a novel manual pilot-drilling method (using a manual drill) within each of the 2-mm and 4-mm layered blocks. The maximum torque values at insertion and removal of the mini-implants were measured, and the total energy was calculated. The data were statistically analyzed using linear regression analysis. Results: The maximum insertion torque was similar regardless of block thickness or pilot-drilling method. Regardless of the pilot-drilling method, the maximum removal torque for the 4-mm block was statistically higher than that for the 2-mm block. For a given block, the total energy at both insertion and removal of the mini-implant for the manual pilot-drilling method were statistically higher than those for the motor-driven pilot-drilling method. Further, the total energies at removal for the 2-mm block was higher than that for the 4-mm block, but the energies at insertion were not influenced by the type of bone blocks. Conclusions: During the insertion and removal of mini-implants in artificial bone blocks, the effect of the manual pilot-drilling method on energy usage was similar to that of the conventional, motor-driven pilot-drilling method. (Korean J Orthod 2011;41(5):354-360)Supported by a grant from Kyung Hee University in 2010 (KHU-20100696).

Décompensation orthodontique assistée par corticotomie pour accroître le volume de l’os alvéolaire de la région symphysaire

Introduction : Le but de cet article est de montrer l’intérêt de l’utilisation de la technique de déplacements dentaires accélérés par corticotomie dans le cas de patients présentant une occlusion de classe III, avec une crête alvéolaire fine, allant bénéficier d’une chirurgie orthognathique. Méthode : Nous avons sélectionné deux patients adultes pour lesquels la malocclusion de classe III devait être décompensée avant chirurgie de recul mandibulaire. La première patiente a été traitée par déplacement dentaire accéléré par corticotomie et technique de décompensation orthodontique classique, la seconde patiente par déplacement dentaire accéléré par corticotomie et décompensation orthodontique à l’aide d’ancrage squelettique temporaire en association avec une membrane de régénération tissulaire guidée. Une décortication alvéolaire sélective est effectuée à l’aide d’une fraise ronde à vitesse lente et une piézochirurgie au niveau du groupe incisivo-canin mandibulaire. Après hémostase, un greffon osseux est placé sur la zone de décortication. Au niveau de la crête alvéolaire extrêmement fine, un système rigide est mis en place pour immobiliser le greffon. Les forces orthodontiques sont appliquées dès la cicatrisation du lambeau, pour initier le déplacement dentaire accéléré. Résultats : Dans les deux cas, le déplacement dentaire accéléré a été initié et a permis de déplacer les dents du secteur incisivo-canin mandibulaire dans la position requise pour la chirurgie orthognathique. Avec l’imagerie préopératoire en 3D, on peut noter des déhiscences alvéolaires au niveau de la face antérieure des dents symphysaires. L’imagerie postopératoire montre une couverture radio-opaque des racines dénudées. Conclusion : La technique de déplacements dentaires accélérés par corticotomie est une méthode sûre et efficace pour permettre la décompensation alvéolaire pré-chirurgicale au niveau des dents symphysaires de ces patients. La combinaison de cette technique avec l’utilisation d’ancrage squelettique temporaire et de greffe osseuse facilite le déplacement dentaire dans des cas de dentures sévèrement altérées