Resin Cast Research Articles

Characterization of hollow glass sphere reinforced epoxy composites: Dynamical mechanical analysis and morphology

Abstract Hollow glass spheres (HGS) have many application areas in the field of composite production due to their lightweight property together with having a sufficient strength. This study has the focus on adding the HGS to epoxy resin in different concentrations. The surface of the glass spheres were modified with silane prior to resin casting. The material characterization of the HGS filled epoxies was based on the silane presence and the HGS addition. Dynamic mechanical analysis was applied to observe the mechanical properties depending on the temperature of the composites. Morphological investigations were made to determine the interfacial adhesion between epoxy and the HGS. As a result of these, it was obtained that the HGS addition enhanced the stiffness of the material without a sharp reduction in the ductility. Silane was observed to be successful in improving the storage modulus below the glass transition temperature (Tg). However, the reduction in Tg was observed in high amount of modified HGS loading due to their interfering effect on the crosslink system of the epoxy.

Direct communication between osteocytes and acid-etched titanium implants with a sub-micron topography.

The osteocyte network, through the numerous dendritic processes of osteocytes, is responsible for sensing mechanical loading and orchestrates adaptive bone remodelling by communicating with both the osteoclasts and the osteoblasts. The osteocyte network in the vicinity of implant surfaces provides insight into the bone healing process around metallic implants. Here, we investigate whether osteocytes are able to make an intimate contact with topologically modified, but micrometre smooth (S a < 0.5 µm) implant surfaces, and if sub-micron topography alters the composition of the interfacial tissue. Screw shaped, commercially pure (cp-Ti) titanium implants with (i) machined (S a = ~0.2 µm), and (ii) two-step acid-etched (HF/HNO3 and H2SO4/HCl; S a = ~0.5 µm) surfaces were inserted in Sprague Dawley rat tibia and followed for 28 days. Both surfaces showed similar bone area, while the bone-implant contact was 73 % higher for the acid-etched surface. By resin cast etching, osteocytes were observed to maintain a direct intimate contact with the acid-etched surface. Although well mineralised, the interfacial tissue showed lower Ca/P and apatite-to-collagen ratios at the acid-etched surface, while mineral crystallinity and the carbonate-to-phosphate ratios were comparable for both implant surfaces. The interfacial tissue composition may therefore vary with changes in implant surface topography, independently of the amount of bone formed. Implant surfaces that influence bone to have higher amounts of organic matrix without affecting the crystallinity or the carbonate content of the mineral phase presumably result in a more resilient interfacial tissue, better able to resist crack development during functional loading than densely mineralised bone.

The Effect of Edentulous Maxillary Impression Tray Designs When Flabby Tissue Is Present: An In Vitro Study.

A model with simulated flabby tissue was fabricated by modifying the standard maxillary edentulous acrylic resin cast to evaluate the effect of maxillary impression tray design on the displacement of flabby tissue. Seven groups of trays were fabricated using different combinations of relief spaces and escape holes. After impression taking, test and control casts were scanned and three-dimensional digital models were superimposed. Negative deviations were recorded at the point of the alveolar crest, the posterior part of the flabby tissue, and the middle of the palate, while positive deviations were recorded at the point of the anterior part of flabby tissue. The amount and characteristics of tissue displacement differed with tray design and the relief method used.

Dummy Load Prototype Design for ITER Coil Power Supply System

This paper mainly introduces the design of the dummy load prototype, whose functions are to verify the capability of the International Thermonuclear Experimental Reactor magnetic power supply systems to operate at their rated power levels without energizing the superconducting coils. The rated inductance is 6.73 mH and the extreme pulse operation mode is 68 kA/15 s ON and 900 s OFF. Therefore, in order to meet the special requirements of the large inductance and the large pulse test current, a structure of dry-type air-core water-cooling prototype with epoxy resin casting technique is presented. The finite-element simulation analysis is introduced in detail, focusing on the thermal performance and dynamic stability, especially under the extreme pulse operation condition. In addition, the electromagnetic environment around the dummy load is also analyzed to provide the input for the instrumentations selection and the delimitation of personal safe area. Finally, seismic analysis is introduced to verify the antiseismic property of the dummy load.

Laser-Modified Surface Enhances Osseointegration and Biomechanical Anchorage of Commercially Pure Titanium Implants for Bone-Anchored Hearing Systems.

Osseointegrated implants inserted in the temporal bone are a vital component of bone-anchored hearing systems (BAHS). Despite low implant failure levels, early loading protocols and simplified procedures necessitate the application of implants which promote bone formation, bone bonding and biomechanical stability. Here, screw-shaped, commercially pure titanium implants were selectively laser ablated within the thread valley using an Nd:YAG laser to produce a microtopography with a superimposed nanotexture and a thickened surface oxide layer. State-of-the-art machined implants served as controls. After eight weeks’ implantation in rabbit tibiae, resonance frequency analysis (RFA) values increased from insertion to retrieval for both implant types, while removal torque (RTQ) measurements showed 153% higher biomechanical anchorage of the laser-modified implants. Comparably high bone area (BA) and bone-implant contact (BIC) were recorded for both implant types but with distinctly different failure patterns following biomechanical testing. Fracture lines appeared within the bone ~30–50 μm from the laser-modified surface, while separation occurred at the bone-implant interface for the machined surface. Strong correlations were found between RTQ and BIC and between RFA at retrieval and BA. In the endosteal threads, where all the bone had formed de novo, the extracellular matrix composition, the mineralised bone area and osteocyte densities were comparable for the two types of implant. Using resin cast etching, osteocyte canaliculi were observed directly approaching the laser-modified implant surface. Transmission electron microscopy showed canaliculi in close proximity to the laser-modified surface, in addition to a highly ordered arrangement of collagen fibrils aligned parallel to the implant surface contour. It is concluded that the physico-chemical surface properties of laser-modified surfaces (thicker oxide, micro- and nanoscale texture) promote bone bonding which may be of benefit in situations where large demands are imposed on biomechanically stable interfaces, such as in early loading and in compromised conditions.

Adjustment of cast metal post/cores modeled with different acrylic resins

Aim: Evaluate the performance of four commercially available chemically-activated acrylic resins (CAARs) by measuring the level of displacement of the cores following casting. Materials and Methods: Two devices were constructed to model the cores based on a natural tooth. Forty post/cores were modeled, 10 in each of the following CAARs: Duralay (Reliance Dental, Illinois, USA), Pattern Resin (GC, Tokyo, Japan), Dencrilay (Dencril, Sao Paulo, Brazil), and Jet (Clássico, Sao Paulo, Brazil). Two casting rings were included,each of which contained 5 post/cores for each of the four CAARs tested, a total of 20 per ring. Following casting, the specimens were only sandblasted and separated from the feeding channels. The post/cores wereplaced in device 1 and, with the aid of an optical microscope, were attached to a digital camera. Images were then taken of the adjustment between the core and the remaining tooth on the labial surface. The images wereprocessed using the Image Tool for Windows, version 3.0, measuring three fixed points in each specimen. Data were statistically analyzed using the ANOVA and Tukey test. Results: The 40 post/cores were dividedinto eight groups according to resin brand and casting, obtaining the following results for mean and standard deviation (in mm): Dencrilay 0.192 CI (± 0.08), CII 0.058 (± 0.03); Duralay CI 0.097 (± 0.03), CII 0.131 (±0.06); Pattern CI 0.07 (± 0.03), CII 0.10 (± 0.05); and Jet CI 0.06 (± 0.02), CII 0.382 (± 0.17). Statistically significant differences could be identified when comparing the Dencrilay CI and the Jet CII with the remaining groups, which all proved to be unfavorable. Conclusion: The quality of cast metal post/core adjustment is not associated with the use of a specific acrylic resin.Uniterms: Post and core techinique. Acrylic resins.

Microcirculation alterations in experimentally induced gingivitis in dogs.

The present study aimed to morphologically examine the gingival microvascular network using a microvascular resin cast (MRC) technique, and to investigate how inflammatory disease functionally affects gingival microcirculation using laser Doppler flowmetry (LDF). We used four beagle dogs with healthy periodontal tissue as experimental animals. To cause periodontal inflammation, dental floss was placed around the cervical neck portions of the right premolars. The unmanipulated left premolars served as controls, and received plaque control every 7days. After 90days, gingivitis was induced in the experimental side, while the control side maintained healthy gingiva. To perform morphological examinations, we used an MRC method involving the injection of low-viscosity synthetic resin into the blood vessels, leading to peripheral soft-tissue dissolution and permitting observation of the bone, teeth, and vascular cast. Gingival blood flow was estimated using an LDF meter. The control gingival vasculature showed hairpin-loop-like networks along the tooth surface. The blood vessels had diameters of 20-40μm and were regularly arranged around the cervical portion. On the other hand, the vasculature in the experimental group was twisted and gathered into spiral forms, with blood vessels that had uneven surfaces and smaller diameters of 8-10μm. LDF revealed reduced gingival blood flow in the group with experimentally induced gingivitis compared to controls. The actual measurements of gingival blood flow by LDF were in agreement with the alterations that would be expected based on the gingivitis-induced morphological alterations observed with the MRC technique.

Effect of remaining tooth structure on the fracture resistance of endodontically-treated maxillary premolars: An in vitro study

Statement of problemAssessing the quantity and distribution of residual coronal dentin is important in deciding the restorability of endodontically treated teeth. PurposeThe purpose of this in vitro study was to investigate the relationship between the cross-sectional area and location of remaining coronal tooth structure and the fracture resistance of restored teeth after endodontic treatment. Material and methodsFifty-five extracted maxillary premolars received endodontic treatment and crown preparations. The teeth were assigned to 11 groups of 5 teeth according to the number and the location of missing axial walls. Impressions of the prepared teeth were made to fabricate dies. Each die was sectioned 1 mm above the finish line, and the dentin surface area was measured. All teeth were restored with composite resin cores and cast metal crowns. The specimens were thermocycled between 5°C and 55°C for 500 cycles before loading until failure with a universal testing machine. The results were analyzed with 1-way ANOVA and post hoc comparisons. ResultsSpecimens with all axial walls intact around the access cavity had the highest mean fracture strength (1380.5 ±393.9 N). Groups with the palatal and 1 or 2 proximal walls missing showed the lowest mean failure loads (398.4 N ±149.5 N and 344.7 N ±91.2 N). The correlation between the surface area and the fracture resistance was 0.72 ConclusionsFor restored endodontically treated maxillary premolars, a positive linear relationship was found between the remaining coronal dentin surface area and fracture strength. Residual dentin location influences fracture resistance.

Renal Extracellular Matrix Scaffolds From Discarded Kidneys Maintain Glomerular Morphometry and Vascular Resilience and Retains Critical Growth Factors.

Extracellular matrix (ECM) scaffolds, obtained through detergent-based decellularization of native kidneys, represent the most promising platform for investigations aiming at manufacturing kidneys for transplant purposes. We previously showed that decellularization of the human kidney yields renal ECM scaffolds (hrECMs) that maintain their basic molecular components, are cytocompatible, stimulate angiogenesis, and show an intact innate vasculature. However, evidence that the decellularization preserves glomerular morphometric characteristics, physiological parameters (pressures and resistances of the vasculature bed), and biological properties of the renal ECM, including retention of important growth factors (GFs), is still missing. To address these issues, we studied the morphometry and resilience of hrECMs' native vasculature with resin casting at electronic microscopy and pulse-wave measurements, respectively. Moreover, we determined the fate of 40 critical GFs post decellularization with a glass chip-based multiplex enzyme-linked immunosorbent assay array and in vitro immunofluorescence. Our method preserves the 3-dimensional conformation of the native glomerulus. Resin casting and pulse-wave measurements, showed that hrECMs preserves the microvascular morphology and morphometry, and physiological function. Moreover, GFs including vascular endothelial growth factor and its receptors are retained within the matrices. Our results indicate that discarded human kidneys are a suitable source of renal scaffolds because they maintain a well-preserved structure and function of the vasculature, as well as GFs that are fundamental to achieve a satisfying recellularization of the scaffold in vivo due to their angiogenic properties.

Resin modification on interlaminar shear property of carbon fiber/epoxy/nano-CaCO3 hybrid composites

Epoxy resin was modified by adding a silane coupling agent/nano-calcium carbonate master batch. Then, samples of binary carbon fiber/epoxy composites and ternary fiber/nano-CaCO3/epoxy were prepared by hot press process. The interlaminar shear strength (ILSS) of the carbon fiber/epoxy composites was investigated and the results indicate that introduction of the treated nano-CaCO3 enhances ILSS obviously. In particular, the addition of 4 wt% nano-CaCO3 leads to 36.6% increase in the ILSS for the composite. The fracture surfaces of the carbon fiber/epoxy composites and the mechanical properties of epoxy resin cast are examined and both of them are employed to explain the change of ILSS. The results show that the change of ILSS is primarily due to an increase of the epoxy matrix strength and an increase of the fiber/epoxy interface. The bifurcation of propagating cracks, stress transfer, and cavitation are deduced for the reasons of strengthening and toughening effect of nano-CaCO3 particles. POLYM. COMPOS., 2015. © 2015 Society of Plastics Engineers

R&D on high-power dc reactor prototype for ITER poloidal field converter

This paper mainly introduces the research and development (R&D) of the high-power dc reactor prototype, whose functions are to limit the circulating current and ripple current in the ITER poloidal field (PF) converter. It needs to operate at rated large direct current 27.5kA and withstand peak fault current up to 175kA. Therefore, in order to meet the special requirements of the dynamic and thermal stability, a new prototype design structure of dry-type air-core water-cooling reactor with epoxy resin casting technique is presented, which is based on the theoretical analysis, finite-element simulation calculation and small prototype test verification. Now the full prototype has been fabricated by China industry, and the dynamic and thermal stability tests of the prototype have also been accomplished successfully. The test results are in compliance with the design and it shows the availability and feasibility of the proposed design, which may be a reference for relevant applications.

Evaluation of Tensile Behaviour of GFRP/SiC Polymer Reinforced Composites

Silicon Carbide/GFRP reinforced matrix composite and SiC matrix composite has been developed by using hand layup and resin casting methods respectively. The GFRP reinforced polymer composite is made by sandwiching two layers of GFRP in between the SiC material. The resin used for the preparation the samples are epoxy and polyester, for both SiC/GFRP composite and SiC composite. An Arcan fixture with butterfly specimen is used to measure the fracture occurring in various modes of the polymer composite. The objective of the proposed testing method is to determine the variation in the stress value depending on the resin material as well as the influence of GFRP in the strength of SiC polymer composite. Results from the tests are analyzed to show that the epoxy resin is better for tensile strength, in both Sic/GFRP reinforced and SiC composite material.

Influence of full denture base manufactured with different material on masticatory efficiency of alveolar ridge

Objective To compare the masticatory efficiency of alveolar ridge restored by thermosetting resin full denture base and cast resin full denture base. Methods 30 patients with alveolar ridge were selected and divided into the two groups by random number table and 15 cases in each group.Full denture with thermosetting resin base was worn in the first month in one group,and masticatory efficiency was measured.Then no false tooth was worn for a week,then full denture with cast resin base for a month, then masticatory efficiency was measured.In the other group, full denture with cast resin base was worn in the first month, and then masticatory efficiency was measured. Then no false tooth was worn for a week, then full denture with thermosetting resin base was worn for a month, then masticatory efficiency was measured.OD value as masticatory efficiency was measured by absorption spectrophotometry. Results The masticatory efficiency(OD value)of full denture with thermosetting resin base was(0.608±0.124), and full denture with cast resin base was(0.885±0.071). The masticatory efficiency of full denture with cast resin base was higher than that with thermosetting resin base(t=14.845,P<0.05). There was 13 cases of increased masticatory efficiency with hot coagulation resin base denture repair, the improved rate was 43.33%,while 24 cases with injection molding denture base denture repair,and the improved rate was 80.00%.The rate with injection molding denture base denture repair was higher than that with hot coagulation resin base denture repair(χ2=31.582,P<0.05). There was no significant adverse reaction in duration of test among all the patients. Conclusion The definition of full denture with cast resin base manufacture was high, and the masticatory efficiency of full denture with cast resin base is higher than that with thermosetting resin base, and the repair effects is better. It is worth of clinical application. Key words: Dental Materials; Denture Repair; Alveolar Process; Mastication

High-Resolution Visualization of the Osteocyte Lacuno-Canalicular Network Juxtaposed to the Surface of Nanotextured Titanium Implants in Human.

Osseointegration is controlled by a number of cellular mechanisms. Although factors governing bone formation are well-understood, the maintenance of bone at the bone-implant interface is less clear. Of some interest is the role of osteocytes, which via mechanotransduction are believed to be responsible for mechanical loading-based remodelling events in bone. Using a resin cast etching technique, we investigated the osteocyte lacuno-canalicular network adjacent to nanostructured titanium human dental implants after four years in clinical function. Correlative electron microscopy showed nanoscale osteocyte processes extending directly onto the implant surface. Calcium signal mapping via electron energy loss spectroscopy (EELS) showed apatite ingrowth into the nanotextured surface, while the apatite platelet c-axis was oriented approximately parallel to the collagen fibril direction. Furthermore, Z-contrast electron tomography demonstrated that natural bone-osteocyte and engineered bone-implant interfaces are similar in ultrastructural morphology. The present ultrastructural observation of multiple connections between osteocyte canaliculi and the nanotextured surface oxide suggests that osteocytes contribute toward the maintenance of osseointegration in long-term clinical function.

Factors Affecting Thickness of Prosthetic Socket in Thermoforming Fabrication

Nowadays, there are two socket fabrication methods in Thailand, which are resin casting and thermal vacuum method. The thermal vacuum forming method has more advantages than the resin casting method that ruins technicians' health from the volatile matter. Nevertheless, the thermal vacuum forming method can fabricate the socket with poor wall thickness distribution. The purpose of this paper is to study the effects of the feed rate of stump mould and the temperature distribution of the plastic sheet on the prosthetic socket wall thickness during the thermal vacuum forming process. The feed rates of stump mould were varied by using an industrial robot. The temperature distribution of the plastic sheet was controlled by circular and annular fiberglass insulators placed in its center. The results showed that the prosthetic socket wall thickness increases around the central area of the socket with a decreased feed rate of stump mould. The annular insulator increases the wall thickness slightly, while the circular insulator increases the thickness significantly. The wall thickness at the thinnest location increased from 1.6 mm up to 2.8 mm. In addition, wall thicknesses of areas beneath the circular insulator increased significantly between the marked positions-25 through +25.

Taxonomical reappraisal of Cathayornithidae (Aves: Enantiornithes)

A complete redescription of Cathayornis caudatus Hou, 1997 is provided based on new information from a resin cast of the holotype, leading to reinterpretation of many morphological features of this initially poorly diagnosed taxon. Detailed comparisons across various specimens referred to Cathayornithidae Zhou et al., 1992 indicate that Sinornis santensis, Cathayornis yandica, C. caudatus and Eocathayornis walkeri are valid taxa, but that C. chabuensis should be regarded as a nomen dubium. The holotype and referred specimens of C. chabuensis differ significantly in morphology, indicating that they do not belong to the same species. A comprehensive phylogenetic analysis targeted at Mesozoic birds reveals that neither Cathayornithidae Zhou et al., 1992 nor Cathayornis Zhou et al., 1992 are monophyletic, and that C. yandica can be regarded as the only species in a monospecific Cathayornithidae. The holotype of ‘C. caudatus’ is assigned to the genus Houornis gen. nov., and a taxonomic reassessment of other ‘cathayornithids’ is presented.http://zoobank.org/urn:lsid:zoobank.org:pub:0B1A404A-CC6A-4609-8CC5-C0DD62983C9A

A case report of a surgical guide fabricated via intraoral scanning-based implant planning and wax-based rapid prototyping

With the recent progress of digital technology, the computer guided surgery utilizing a guide template in the placement of implant has been actively performed, and the method employing the intraoral scanner at the implant prosthesis introduced. Fabrication method of the guide template can be largely classified into design-related rapid prototyping (RP) system and vector milling system, and each of the method has its own weakness in the clinical application despite of excellent accuracy. Thus, in this case study, a work- ing model was fabricated by the wax RP technology using images acquired by CBCT and an intraoral scanner, and the metal bushing was picked up with orthodontic resin cast upon the wax model. Using this method, a surgical guide template was fabricated and used in surgery. From this, we could obtain a satisfactory outcome clinically in the implant placement and the fabrication of the final prostheses and thus report this case herein. (J Korean Acad Prosthodont 2015;53:244-9)

Accuracy of optical dental digitizers: an in vitro study.

The aim of this study was to evaluate the accuracy, in terms of trueness and precision, of optical dental scanners. An experimental acrylic resin cast was created and digitized using a microcomputed tomography (microCT) scanner, which served as the reference model. Five polyether impressions were made of the acrylic resin cast to create five stone casts. Each dental digitizer (Imetric, Lava ST, Smart Optics, KaVo Everest) made five scans of the acrylic resin cast and one scan of every stone cast. The scans were superimposed and compared using metrology software. Deviations were calculated between the datasets obtained from the dental digitizers and the microCT scanner (= trueness) and between datasets from the same dental digitizer (= precision). With exception of the Smart Optics scanner, there were no significant differences in trueness for the acrylic resin cast. For the stone casts, however, the Lava ST performed better than Imetric, which did better than the KaVo scanner. The Smart Optics scanner demonstrated the highest deviation. All digitizers demonstrated a significantly higher trueness for the acrylic resin cast compared to the plaster cast, except the Lava ST. The Lava ST was significantly more precise compared to the other scanners. Imetric and Smart Optics also demonstrated a higher level of precision compared to the KaVo scanner. All digitizers demonstrated some degree of error. Stone cast copies are less accurate because of difficulties with scanning the rougher surface or dimensional deformations caused during the production process. For complex, large-span reconstructions, a highly accurate scanner should be selected.

Investigation of Mechanical Behaviour of Glass Fibre Based SiC Polymer Composites

Silicon Carbide/GFRP reinforced matrix composite and SiC matrix composite has been developed by using hand layup and resin casting methods respectively. The GFRP reinforced polymer composite is made by sandwiching two layers of GFRP in between the SiC material. The resin used for the preparation the samples are epoxy and polyester, for both Sic/GFRP composite and SiC composite. An Arcan fixture with butterfly specimen is used to measure the fracture occurring in various modes of the polymer composite. The objective of the proposed testing method is to determine the variation in the stress value depending on the resin material as well as the influence of GFRP in the strength of SiC polymer composite. Results from the tests are analyzed to show that the polyester resin is better for shear strength, in both Sic/GFRP reinforced and SiC composite material.

Intrahepatic Bile Duct Regeneration in Mice Does Not Require Hnf6 or Notch Signaling through Rbpj

The potential for intrahepatic bile duct (IHBD) regeneration in patients with bile duct insufficiency diseases is poorly understood. Notch signaling and Hnf6 have each been shown to be important for the morphogenesis of IHBDs in mice. One congenital pediatric liver disease characterized by reduced numbers of IHBDs, Alagille syndrome, is associated with mutations in Notch signaling components. Therefore, we investigated whether liver cell plasticity could contribute to IHBD regeneration in mice with disruptions in Notch signaling and Hnf6. We studied a mouse model of bile duct insufficiency with liver epithelial cell-specific deficiencies in Hnf6 and Rbpj, a mediator of canonical Notch signaling. Albumin-Cre Hnf6(flox/flox)Rbpj(flox/flox) mice initially developed no peripheral bile ducts. The evolving postnatal liver phenotype was analyzed using IHBD resin casting, immunostaining, and serum chemistry. With age, Albumin-Cre Hnf6(flox/flox)Rbpj(flox/flox) mice mounted a ductular reaction extending through the hepatic tissue and then regenerated communicating peripheral IHBD branches. Rbpj and Hnf6 were determined to remain absent from biliary epithelial cells constituting the ductular reaction and the regenerated peripheral IHBDs. We report the expression of Sox9, a marker of biliary epithelial cells, in cells expressing hepatocyte markers. Tissue analysis indicates that reactive ductules did not arise directly from preexisting hilar IHBDs. We conclude that liver cell plasticity is competent for regeneration of IHBDs independent of Notch signaling via Rbpj and Hnf6.