• The Journal of Korean Academy of Prosthodontics
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• v.33 no.3
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• pp.539-549
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• 1995

The purpose of this study was to determine the accuracy of 3 implant impression methods by using strain gauge. The models used for this study were partially edentulous mandibular acrylic resin casts Model A, with two abutment analogs in #46,47 extraction site, represented two implant parallel to to the adjacent natural tooth. Model B represent an anterior implant parallel to the adjacene natural tooth and a posterior implant exhibiting a 15-degree lingual inclination. Master framework were fabricated on the master model, and 3 strain gauges were attached to a master framwork to determine the passivity of fit of the framework to sample casts made by the three impression techniques. The master framework was attached to each sample cast with gold screws, which were tightened with the torque driver to ensure a consistent toque application of 10 Ncm. Universal Digital Measuring System UCAM-5BT was used for strain measuring. Impression techniques studid were : 1. unsplinted tapered impression coping, polyvinyl siloxane, stock tray 2. unsplinted squared impression coping, polyether, custom tray 3. squared impression coping splinted with Duralay resin, polyether, custom tray Through analysis on data from this study, the following conclusions were obtained. 1. There were no statistically significant differences between the mean strain recorded from the sample casts made with the tree impression. But only strain values of model A(parallel group) Y-axis was signifcantly differed between Technique 1 and 3(P<0.05). 2. There was no statistically significant difference between model A(parallel group) and model B(15-degree divergent group).

• The Journal of Korean Academy of Prosthodontics
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• v.35 no.4
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• pp.767-780
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• 1997

One of the most common problems of implant prosthesis is the screw loosening of abutment screws. This brings on discomfort in mastication, inflammation in the peri-implant tissue due to poor oral hygiene and fracture of prosthesis or loss of osseointegration. To prevent screw loosening, appropriate implantation to direct the occlusal force to the long axis of the implant, accurate design of the superstructure, decrease of the occlusal table, and adequate torque on the abutment screw are necessary. In this study the screw loosening torque was evaluated in implants with dimples or flutes in the internal surface of abutment screw holes. The abutments were fastened with slot type and hexagonal type abutment screws and were sealed with vinyl poly siloxane impression and bite registration material respectively. The screw loosening torque was evaluated after 1,800 and 12,600 times loading under a loading machine. The results were as follows. 1. The flute form group showed significantly higher loosening torque compared to the dimple form group and the group with no inner surface treatment (p<0.05). 2. There was no statistical difference in loosening torque according to the sealing materials. 3. The loosening torque according to the types of abutment screw showed no significant difference. 4. The loosening torque was significantly higher after 1800 times loading compared to 12600 times loading(p<0.05). From the above results. it is thought that formation of a flute in the internal surface of the screw hole decreases the chance of screw loosening, but the sealing materials and types of abutment screw did not show significant difference in prevention of screw loosening.

• Restorative Dentistry and Endodontics
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• v.18 no.2
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• pp.483-496
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• 1993

Dentin hypersensitivity medicaments such as Gluma, Scotchbond 2, All-Bond 2, which are resin adhesives, were used to compare the sealing effects of dentinal tubule under mechanical stress. Topical application of above medicaments on the dentin surfaces of extracted teeth followed by artificial tooth brushing for 6 weeks was performed for the comparison. The following conclusions on the degree of dentinal tubule exposure versus time by were reached by using polyvinyl siloxane impression material for taking the impression, epoxy resin for the duplication and SEM for observing the surface. 1. SEM was used to compare the accuracy of the duplicated surface, but no differences were found when teeth samples and the duplicated surfaces were observed. 2. After comparing the degree of dentinal tubules exposure with varnish applied contrast group, resin adhesive materials showed much less exposure as time went by. 3. The results indicated that AU-Bond 2 adhesive, under mechanical stress, showed lesser exposure of dentinal tubules comparing with Gluma and Scotchbond 2 adhesives After the results were put together, it was demonstrated that resin replica method is an useful way to evaluate the treatment effects of the dentinal tubule hypersensitivity medicaments. Also, it was noticed that under mechanical stress, All-Bond 2, classified as fourth generation, illustrated the best dentinal tubules sealing effects.

• Journal of Hydrogen and New Energy
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• v.27 no.2
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• pp.135-143
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• 2016

Biogas is a renewable fuel from anaerobic digestion of organic matters such as sewage sludge, manure and food waste. Raw biogas consists mainly of methane, carbon dioxide, hydrogen sulfide, and water. Biogas may also contain other impurities such as siloxanes, halogenated hydrocarbons, aromatic hydrocarbons. Efficient power technologies such as fuel cell demand ultra-low concentration of containments in the biogas feed, imposing stringent requirements on fuel purification technology. Biogas is upgraded from pressure swing adsorption after biogas purification process which consists of water, $H_2S$ and siloxane removal. A polymer electrolyte membrane fuel cell power plant is designed to operate on reformate produced from upgraded biogas by steam reformer.

• Journal of the Korean Applied Science and Technology
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• v.25 no.2
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• pp.115-122
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• 2008

The hydrosilylation is an addition reaction of Si-H bond to unsaturated double bonds, which provides a convenient mechanism to synthesize poly(dimethylsiloxane-co-methylsiloxane)copolymer having siloxy units in polymer backbone. In this study, Poly(dimethylsiloxane-co-methylsiloxane) copolymer was synthesized through the polymerization reaction of cyclopentasiloxane with poly(methyl-hydrogen) siloxane. Silicone-hydrogen functional group of the poly(dimethylsiloxane-co-methylsiloxane) copolymer was substituted to the alkyl groups by hydrosilylation. And their structure was analyzed with FT-IR, H-NMR and GPC instruments, respectively. Surface tension of the synthetic compounds is increased from 22dyne/cm to 25dyne/cm according to increase additional EO moles. The cmc which was evaluated by surface tension was ranged $10^{-5}$ to $10^{-4}mol/L$ and it was decreased according to increase of dimethyl siloxyl content. HLB number of these surfactants was evaluated 9.5 to 11.5 range. These silicone surfactants is applied to self-emulsifier defoamer and personal care products as surface tension depressant, emulsifier, foam control agent.

• Polymer(Korea)
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• v.26 no.5
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• pp.607-614
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• 2002

Polyorganosiloxane(HBPS) modified polyurethane (UMPS) was synthesized to improve weatherability in the polyurethane (ITPU) sealant and its rheological propoerty was investigated. It was found that the viscosity increased with increasing HBPS content in polyurethane and maximum viscosity was observed in UMPS having 70/30 ITPU/HBPS ratio. This was understood that the segregation of HBPS segment in UMPS chain has been developed. Further increasing of the content of HBPS resulted in the lowering of viscosity because of the flexibility of HBPS block segment in UMPS chain. It was also found that UMPS has more sensitive environmental dependency of viscosity than ITPU such as shear rate, humidity and temperature. In additions, UMPS having Si(O$CH_3$)$_3$ end group (TUMPS) by adding coupling agent up to 0.3 wt% resulted in the increase of viscosity by the acceleration of curing. But introducing more than 0.5wt% curing agent to TUMPS caused the lowering of viscosity because of less NCO group in TUMPS for the curing.

• The Journal of Advanced Prosthodontics
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• v.13 no.5
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• pp.316-326
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• 2021

PURPOSE. Purpose of this in vitro study was to determine the accuracy of different intraoral scans versus laboratory scans of impressions and casts for the digitization of an edentulous maxilla. MATERIALS AND METHODS. A PEEK model of an edentulous maxilla, featuring four hemispheres on the alveolar ridges in region 13, 17, 23 and 27, was industrially digitized to obtain a reference dataset (REF). Intraoral scans using Cerec Primescan AC (PRI) and Cerec AC Omnicam (OMN), as well as conventional impressions (scannable polyvinyl siloxane) were carried out (n = 25). Conventional impressions (E5I) and referring plaster casts were scanned with the inEOS X5 (E5M). All datasets were exported in STL and analyzed (Geomagic Qualify). Linear and angular differences were evaluated by virtually constructed measurement points in the centers of the hemispheres (P13, P17, P23, P27) and lines between the points (P17-P13, P17-P23, P17-P27). Kolmogorov-Smirnov test and Shapiro-Wilk test were performed to test for normal distribution, Kruskal-Wallis-H test, and Mann-Whitney-U test to detect significant differences in trueness, followed by 2-sample Kolmogorov-Smirnov test to detect significant differences in precision (P < .008). RESULTS. Group PRI showed the highest trueness in linear and angular parameters (P < .001), while group E5I showed the highest precision (P < .001). CONCLUSION. Intraoral scan data obtained using Primescan showed the highest trueness while the indirect digitization of impressions showed the highest precision. To enhance the workflow, indirect digitization of the impression itself appears to be a reasonable technique, as it combines fast access to the digital workflow with the possibility of functional impression of mucosal areas.

• Journal of Technologic Dentistry
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• v.42 no.4
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• pp.355-361
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• 2020

Purpose: In this study, we added two kinds of photoinitiators (CQ and TPO) to prepare two kinds of denture base resins (Bis-GMA series and UDMA series) for three-dimensional (3D) printing to compare and analyze their mechanical and biological properties and to find the optimal composition. Methods: Control specimens were made using the mold made of polyvinyl siloxane of the same size. Light curing was performed twice for 20 seconds on both the upper and lower surfaces with LED (light emitting diode) light-curing unit (n=10). Experimental 3D printing dental resins were prepared, to which two photoinitiators were added. Digital light processing type 3D printer (EMBER, Autodesk, CA, USA) was used for 3D printing. The specimen size was 64 mm×10 mm×3.3 mm according to ISO 20795-1. The final specimens were tested for flexural strength and flexural modulus, and MTT test was performed. Furthermore, one-way analysis of variance was performed, and the post-test was analyzed by Duncan's test at α=0.05. Results: The flexural strength of both Bis-GMA+CQ (97.12±6.47 MPa) and UDMA+TPO (97.40±3.75 MPa) was significantly higher (p<0.05) in the experimental group. The flexural modulus in the experimental group of UDMA+TPO (2.56±0.06 GPa) was the highest (p<0.05). MTT test revealed that all the experimental groups showed more than 70% cell activity. Conclusion: The composition of UDMA+TPO showed excellent results in flexural strength, flexural modulus, and biocompatibility.

• The Journal of Advanced Prosthodontics
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• v.16 no.3
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• pp.163-173
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• 2024

PURPOSE. This study assessed the effect of storage time on chemical structure of a single-bottle and a two-bottle experimental ceramic primer and micro-shear bond strength (µSBS) of composite to ceramic. MATERIALS AND METHODS. This study was conducted on 60 sintered zirconia and 60 feldspathic porcelain blocks. Half of the specimens (n = 30) were subjected to surface treatment with the single-bottle Clearfil ceramic primer (n = 15) and two-bottle experimental primer (n = 15) after 24 hours. The remaining half received the same surface treatments after 6 months storage in distilled water. Composite cylinders were bonded to the ceramics, and they were then subjected to µSBS test. Also, the primers underwent Fourier-transform infrared spectroscopy (FTIR) after 24 hours and 6 months to assess their chemical structure. Data were analyzed with 3-way ANOVA and adjusted Bonferroni test (alpha = 0.05). RESULTS. The µSBS of both ceramics significantly decreased at 6 months in one-bottle ceramic primer group (P = .001), but it was not significantly different from the two-bottle experimental primer group (P = .635). FTIR showed hydrolysis of single-bottle primer, cleavage of silane and 10-MDP bonds, and formation of siloxane bonds after 6 months. CONCLUSION. Six months of storage caused significant degradation of single-bottle ceramic primer, and consequently had an adverse effect on µSBS.

• Elastomers and Composites
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• v.44 no.2
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• pp.150-155
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• 2009

This study examined the effects of the concentration variation of the silyl hydride (Si-H) functional group in polymethylhydrogen siloxane cross-linker and the vinyl-functional group in silicone prepolymer on the physical properties of the dental polyvinylsiloxane impression materials (PVS). When the SiH/Vinyl ratio was 1.6 (Group $\underline{C6}$ containing ${\underline{C}}ross$-linker $\underline{6}$ parts), the setting rate was too slow even though their tensile strength was the highest within the tested groups. When the SiH/Vinyl ratio was 3.2 (Group C12), the setting rate was too fast to allow appropriate working time even though their mechanical properties were good. The C14 group showed rather lower tensile strength compared to the groups having lower cross-linker contents. Notably, too much incorporation of cross-linker, like C16 group, induced delay of the setting, by which the mechanical and manipulation properties were detrimentally affected.