Development of Ultrasonic Vibration-Assisted Magnetic Compound Fluid (MCF) Polishing Technology

This study investigates the development of an ultrasonic vibration-assisted magnetic compound fluid (MCF) polishing technology for final polishing. The fabrication of an experimental apparatus entails an ultrasonic polishing unit, and the experimental investigation of its performance in surface polishing is described. In addition, ultrasonic vibration-assisted MCF polishing under different applied methods of ultrasonic vibration is studied. The experimental results indicate that applying ultrasonic vibration to the workpiece improves the surface roughness and material removal rate when the ultrasonic vibrations are changed. In addition, across the range of polishing conditions employed in this study, the precision surface roughness and high material removal rate can be easily obtained on the acrylic plate by applying an elliptical vibration to the ultrasonic vibration.

Analysis of Changes in the Tensile Bond Strenght of Soft Relining Material with Acrylic Denture Material

Abrasions and pressure ulcers on the oral mucosa are most often caused by excessive pressure or incorrect fitting of the denture. The use of soft relining materials can eliminate pain sensations and improve patient comfort. The main functional feature of soft elastomeric materials is the ability to discharge loads from the tissues of the mucosa. (1) Background: The aim of the work was a comparative laboratory study of ten materials used for the soft lining of acrylic dentures. (2) Methods: There were materials based on acrylates (Vertex Soft, Villacryl Soft, Flexacryl Soft) and silicones (Sofreliner Tough Medium, Sofreliner Tough Medium, Ufi Gel SC, GC Reline Soft, Elite Soft Relining, Molloplast). Laboratory tests include the analysis of the tensile bond strength between the relining material and the acrylic plate of the prosthesis. The tests were conducted taking into account 90-day term aging in the distilled water environment based on the methodology presented in the European Standard ISO 10139-2. (3) Results: After three months of observation, the highest strength of the joint was characterized by Flexacryl Soft acrylic, for which the average value was 2.5 MPa. The lowest average value of 0.89 MPa was recorded for the GC Reline Soft silicone material. Over time, an increase in the value of the strength of the combination of acrylic materials and a decrease in these values in the case of silicone materials was observed. (4) Conclusion: Each of the tested silicone materials showed all three types of damage, from adhesive to mixed to cohesive. All acrylic-based materials showed an adhesive type of failure. Time did not affect the type of destruction.

Mapping of a multilayer panoramic radiography device

Objective: To map the shape, location, and thickness of the focal trough of a panoramic radiography device with a multilayer imaging program. Methods: An acrylic plate (148 × 148 × 3 mm) containing 1156 holes distributed in a matrix of 34 × 34 rows was placed in the OP300 Maxio at the levels of the maxilla and mandible. 20 metal spheres (3.5 mm in diameter) were placed on the holes of the plate under 15 different arrangements and panoramic images were acquired for each arrangement at 66 kV, 8 mA, and an exposure time of 16 s. The resulting panoramic radiographs from the five image layers were exported, the horizontal and vertical dimensions of the metal spheres were measured in all images using the Image J software, and the magnification and distortion rates of the spheres were calculated. All metal spheres presenting a magnification rate lower than 30% in both vertical and horizontal dimensions and a distortion rate lower than 10% were considered to map the focal troughs of each of the five image layers. Results: All panoramic image layers had a curved shape ranging from 39° to 51° for both dental arches and varied in position and thickness. The anterior region of maxilla was anteriorly displaced when compared to the anterior region of the mandible for all layers. Image layers are thicker at the level of the mandible than those at the level of the maxilla; also, inner layers were thinner and outer layers were thicker. Conclusion All image layers in the studied panoramic radiography device had a curved shape and varied in position and thickness. The anterior region of maxilla was anteriorly displaced when compared to that of the mandible for all layers.

Case series: “Double arch” changes caused by capsule contraction syndrome after cataract surgery in highly myopic eyes

Background Capsule contraction syndrome (CCS) after cataract surgery causes intraocular lens (IOL) haptic flexion and IOL optic displacement in most former reports. However, there are few reports on CCS-induced deformation of the IOL optic. We report two cases of CCS after cataract surgery in highly myopic eyes and describe a previously unreported “double arch” complication. Case presentation Two patients with history of high myopia had cataract surgery with hydrophilic acrylic plate haptic IOLs implanted in their eyes. CCS with arch shape deformation of the pupil as well as the optic of the IOL were noticed in both cases after three months, which induced refractive changes and corrected distance visual acuity (CDVA) deterioration. Visual acuity of the patients was restored by replacing the IOL from the capsular bag to the ciliary sulcus and the following neodymium: YAG (Nd:YAG) laser capsulotomy. We propose that such “double arch” change brought by CCS is related to the plate-haptic design of the IOL and the incomplete overlap between the capsular opening and the IOL optic. Conclusions We recommend careful IOL selection and proper capsulorhexis in patients with high myopia or with other risk factors of CCS. Early diagnosis and timely treatment of CCS are critical to prevent visual symptoms and further ocular complications.

Hydraulically Coupled Dielectric Elastomer Actuators for a Bioinspired Suction Cup

Suction cups of cephalopods show a preeminent performance when absorbing irregular or flat objects. In this paper, an octopi-inspired suction cup, driven by hydraulically coupled dielectric elastomer actuators (HCDEAs), is proposed, which is considered to be controlled easily and have compact structure. To investigate the performance of suction cups, experiments have been conducted to clarify the effect of the pre-stretch ratio and chamber angle on suction forces. It could be seen that both factors have a complicated influence on suction forces, and the best performance obtained was a reasonable combination of the pre-stretch ratio and chamber angle. Here, we achieved a maximum suction force of 175 mN with λp = 1.2, α = 23° under a DC voltage of 3500 V. To enhance the capacity and adaptation of the suction cup, flat objects of various types of materials were introduced as targets. Experimental results displayed that for tested materials, including a dry/wet acrylic plate, CD, ceramic wafer, and aluminum plate, the suction cup showed outstanding performance of absorbing and lifting the target without any damage or scratch to them. Our research may serve as a guide to the optimal design and provide insights into the performance of the HCDEAs-actuated suction cup.

Friction evaluation of an elastic chain positioned under or over the wire in self-ligating brackets

Objectives: This study aimed to evaluate the frictional resistance produced by active and passive self-ligating brackets on stainless steel archwires in the absence or presence of elastomeric chains under or over the wire. Materials and Methods: Four types of self-ligating brackets were used: Two active and two passive. For each commercial brand, five brackets were bonded to an acrylic plate and the frictional resistance was evaluated with 0.018” and 0.019” × 0.025” stainless steel wires in three situations: Without elastomeric chain, with elastomeric chain placed under and over the wire. Results: The bracket type, cross-section of the wire, and type of ligation had significant interactions with each other; the frictional resistance was significantly lower with the use of passive self-ligated brackets, while no difference was found when a 0.018” wire was tested. Moreover, the frictional resistance in the absence of an elastomeric chain, or when the chain was under the wire, was significantly lower in comparison with the values obtained when the chain was placed on the wire. Conclusion: Frictional resistance of passive and active self-ligated brackets is influenced by the ligation methods and the cross-sectioning of archwires.

Mechanical testing of paraosseous clamp-cerclage stabilization compared to interfragmentary wiring and combination technique in L-shape acrylic plate simulate to canine mandibular fracture

The purpose of this research was to comparison of the mechanical strength of the three different stabilization techniques in canine mandibular models. An L-shaped acrylic plate to replicate the mandible of a middle-sized dog was used as a canine mandibular fracture model. The research compared the strength of 3 fixation techniques: interfragmentary wiring, paraosseous clamp-cerclage stabilization, and a combination of both techniques. Each method was tested using 6 acrylic samples and measuring the maximum pressure load on the rostral mandible model using a Hounsfield H50KS testing machine. Statistical analysis was used to summarize the maximum load results from each method. The strengths of the interfragmentary wiring technique and the combination technique were not significantly different, while the paraosseous clamp-cerclage stabilization technique had significantly less strength than the other two techniques. The acrylic samples simulated the mandibular bone in a medium-sized breed dog because there are variable sizes and conformations of the mandible. This method was used to help neutralize other confounding factors associated with using real bone. In conclusion, the combination technique of interfragmentary wiring and paraosseous clamp-cerclage was the best method that can be used for increased stabilization of mandibular fixation. This technique was useful for facilitating stabilization of a mandible at a lower cost compared with the bone plate and screw method.

DESIGN AND EXPERIMENTAL STUDY OF EQUAL-AREA VARIABLE-PITCH SCREW STRUCTURE FOR WHEAT FLOUR

The parameters of a wheat flour equal-pitch screw feeder are mainly based on empirical design. A method comparing the effect of the number of blocked zones on the feeding sections is proposed to complete the screw parameter of four feeding sections. According to the designed screw structure, Solid Works was used to build the three-dimensional model, and EDEM software was imported for discrete element analysis. It is found that the optimal solution is the screw design with two blocked zones, in which the cutting stock of the feeding sections is very uniform with high feeding accuracy on the premise of satisfying the screw feeding. In order to verify the rationality of the design of the screw structure, the screw was processed based on the optimal parameters, and the screw feeding device of the transparent outer cylinder was built with acrylic plate, and then the feeding stability of wheat flour was observed. The flow fluctuation of the designed screw is relatively small, and the feeding is more uniform, so the accuracy of the screw feed is higher. The experiment verifies the rationality of the variable pitch design and provides a reference for the design and development of wheat flour screw feeding device.