Harvesting electrical energy using plasmon-enhanced light pressure in a platinum cut cone.

We have designed a method of harvesting electrical energy using plasmon-enhanced light pressure. A device was fabricated as a cut cone structure that optimizes light collection so that the weak incident light pressure can be sufficiently enhanced inside the cut cone to generate electrical energy. An increase in the device's current output is a strong indication that the pressure of incident light has been enhanced by the surface plasmons on a platinum layer inside the cut cone. The electrical energy harvested in a few minutes by irradiating pulsed laser light on a single micro device was possible to illuminate a blue LED.

A biomechanical study of artificial cervical discs using computer simulation.

STUDY DESIGN: A virtual simulation model of the subaxial cervical spine was used to study the biomechanical effects of various disc prosthesis designs. OBJECTIVE: To study the biomechanics of different design features of cervical disc arthroplasty devices. SUMMARY OF BACKGROUND DATA: Disc arthroplasty is an alternative approach to cervical fusion surgery for restoring and maintaining motion at a diseased spinal segment. Different types of cervical disc arthroplasty devices exist and vary based on their placement and degrees of motion offered. METHODS: A virtual dynamic model of the subaxial cervical spine was used to study 3 different prosthetic disc designs (PDD): (1) PDD-I: The center of rotation of a spherical joint located at the mid C5-C6 disc, (2) PDD-II: The center of rotation of a spherical joint located 6.5 mm below the mid C5-C6 disc, and (3) PDD-III: The center of rotation of a spherical joint in a plane located at the C5-C6 disc level. RESULTS: A constrained spherical joint placed at the disc level (PDD-I) significantly increased facet loads during extension. Lowering the rotational axis of the spherical joint towards the subjacent body (PDD-II) caused a marginal increase in facet loading during flexion, extension, and lateral bending. Lastly, unconstraining the spherical joint to move freely in a plane (PDD-III) minimized facet load build up during all loading modes. CONCLUSION: The simulation model showed the impact simple design changes may have on cervical disc dynamics. The predicted facet loads calculated from computer model have to be validated in the experimental study.

Surface-data-based haptic rendering for simulation of surgery of closed reduction and internal fixation.

This paper presents a surface-data-based haptic rendering method for simulation of surgery of closed reduction and internal fixation (CRIF). Volumetric data is often employed in the simulation of bone surgery because the volume rendering can easily handle information such as density and rigidity of each voxel. However, it is difficult to implement real-time graphics and haptic rendering because of the large computational workload. Therefore, we propose a surface-data-based haptic rendering method for real-time rendering. Mechanical properties and graphics of the inner part of the bone should be modeled in addition to the surface data to simulate drilling into the bone. An algorithm is developed to construct the surface of the drilled hole. This method allows the user of the simulation to feel the varying forces according to the drilled depth.

Enamel surface evaluation after removal of orthodontic composite remnants by intraoral sandblasting: a 3-dimensional surface profilometry study.

INTRODUCTION: The purpose of this study was to determine the utility of sandblasting to remove composite remnants after orthodontic bracket debonding. METHODS: The sample consisted of 20 human premolars extracted for orthodontic purposes. The buccal surface of each premolar was divided into 3 parts: the upper half (control surface group, CS), the lower half left (LS group), and the lower half right (SS group). A composite resin paste (volume, 5 x 3 x 1 mm3) was bonded onto the LS and SS surfaces. Then it was removed by using 1 of 2 methods: low-speed handpiece with tungsten carbide bur in the LS group and sandblasting in the SS group. Temperature change and removal time were recorded, and surface profiles were examined with 3-dimensional profilometry. RESULTS: An independent t test showed a statistically significant difference in temperature change between the LS and SS groups (P <.01). ANOVA showed no significant difference in surface profile between the LS and SS groups (P >.5). CONCLUSIONS: The results suggest that intraoral sandblasting might be an alternative to rotatory instruments for resin remnant removal after orthodontic bracket debonding.

Biomechanical testing simulation of a cadaver spine specimen: development and evaluation study.

STUDY DESIGN: This article describes a computer model of the cadaver cervical spine specimen and virtual biomechanical testing. OBJECTIVES: To develop a graphics-oriented, multibody model of a cadaver cervical spine and to build a virtual laboratory simulator for the biomechanical testing using physics-based dynamic simulation techniques. SUMMARY OF BACKGROUND DATA: Physics-based computer simulations apply the laws of physics to solid bodies with defined material properties. This technique can be used to create a virtual simulator for the biomechanical testing of a human cadaver spine. An accurate virtual model and simulation would complement tissue-based in vitro studies by providing a consistent test bed with minimal variability and by reducing cost. METHOD: The geometry of cervical vertebrae was created from computed tomography images. Joints linking adjacent vertebrae were modeled as a triple-joint complex, comprised of intervertebral disc joints in the anterior region, 2 facet joints in the posterior region, and the surrounding ligament structure. A virtual laboratory simulation of an in vitro testing protocol was performed to evaluate the model responses during flexion, extension, and lateral bending. RESULTS: For kinematic evaluation, the rotation of motion segment unit, coupling behaviors, and 3-dimensional helical axes of motion were analyzed. The simulation results were in correlation with the findings of in vitro tests and published data. For kinetic evaluation, the forces of the intervertebral discs and facet joints of each segment were determined and visually animated. CONCLUSIONS: This methodology produced a realistic visualization of in vitro experiment, and allowed for the analyses of the kinematics and kinetics of the cadaver cervical spine. With graphical illustrations and animation features, this modeling technique has provided vivid and intuitive information.

Biomechanical advantage of lengthening of the femur with an external fixator over an intramedullary nail.

The present experimental study investigated biomechanical differences in methods of femoral lengthening using a monolateral external fixator only and using an external fixator over an intramedullary nail. Three materials, namely polyvinyl chloride rods, composite synthetic bone, and cadaver-bone, were tested using the MTS machine. We evaluated the differences of axial stiffness according to the presence of a nail or the numbers of half-pins (two or three half-pins) that were fixed at each side of osteotomy. The addition of a nail may increase the axial stiffness of the frame of monolateral external fixator for limb lengthening. Additionally, it is enough to distract the femur with fixing two half-pins at each side, when using the technique of lengthening over a nail.

Effect of pH and temperature on orthodontic NiTi wires immersed in acidic fluoride solution.

Orthodontic arch wires can confront diverse pH and temperature conditions in the oral cavity after replacement. The current study evaluated the effect of pH and temperature on orthodontic NiTi arch wires after immersion in an acidic fluoride solution. The acetic acid added for the adjustment of pH forms hydrofluoric acid (HF). More HF was formed in a solution of lower pH with higher temperature than that of the higher pH with lower temperature. Within the same pH value, the temperature of the solution affected the concentration of HF. Each as-received wire exhibited quite different microhardness values. The reduction of microhardness, 1.2-5.7%, occurred after immersion. Within the same product, however, the pH and temperature had minor influence on the reduction. The volumetric weight change, concentration of the released elements, and surface morphology were influenced by pH and temperature. At pH 3.5 of 60 degrees C solution, the greatest weight loss, release of elements, and corrosion of surface occurred from the wires. At pH 6, on the other hand, no such loss or release occurred regardless of temperature. At 5 degrees C solution, the surface exhibited minor corrosion regardless of pH value.

Management of ipsilateral femoral and tibial fractures.

This is a retrospective study of 18 patients who had ipsilateral femoral and tibial fractures. They were treated by the retrograde femoral and antegrade tibial intramedullary nail from a single incision in the knee. The average time for union of femoral shaft fractures was 27.6 (18--40) weeks. One patient required antegrade nailing with a bone graft due to metal failure after using the short nail. Two tibial fractures required bone grafting due to bone loss, with an initial open fracture. The average time for union of tibial fractures was 24.5 (18--30) weeks. Functional results using the Karlstrom-Olerud criteria were excellent in 14, good in three, and acceptable in one. The only acceptable result was in a supra- and inter-condylar femoral fracture, with protrusion of the nail tip into the knee joint, which created moderate limitation of knee motion. Simultaneous retrograde femoral and antegrade tibial nailing with a single incision in the knee can achieve satisfactory results in the management of these types of fracture.