• The Journal of Korean Academy of Prosthodontics
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• v.31 no.2
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• pp.219-235
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• 1993

To determine the compatibilities of soft liming materials with denture cleansers by measuring the flexibility and elasticity and investigating the surface changes, 4 self-curing acrylic resin soft lining materials and 1 heat-curing silicone soft lining material were evaluated. 3mm thick x 20mm diameter discs of soft lining materials were individually bonded to a hard acrylic resin base as per manufacturers’instructions. Using an Instron universal testing machine, a static stress of $2kg/cm^2$ was applied for 30secs., the strain in compression was measured, giving an indication of the material’s flexibility. Elastic recovery was measured at 10secs. After removal of stress. Surface changes were investigated with Stereomicroscope. Then the specimens were immersed in 4alkaline peroxide denture cleansers and water as control group, tests were carried out at 1 day, 2 days, 7 days, 14 days and 30 days. The results were as follows : 1. Alkaline peroxide denture cleansers caused considerable porosity on the surface of selfcuring acrylic resin soft lining materials, and the most affected by the cleansers were Viscogel, Coe-Soft, Coe-Comfort, Lynal, in that order. 2. There was significant difference in flexibility between each soft lining material except for Coe-Comfort and Visco-gel, and every soft lining material was significant difference in elasticity. Especially Molloplast-B and Lynal were less flexible and more elastic than other soft lining materials(p<0.05). 3. The denture cleansers increased the flexibility and elasticity of the soft lining materials compared with control group(p<0.05), and Denalan, Polident, Kleenite, Efferdent affected the soft lining materials in that order. 4. There was significant difference in flexibility between each denture cleanser except for Denalan and Polident(p<0.05). Though Denalan and Polident, Denalan and Kleenite did not show significant difference in elasticity, other denture cleansers showed significant difference among each other(p<0.05). 5. Clinically Coe-Comfort, Coe-Soft and Visco-gel were incompatible with alkaline peroxide denture cleansers, and Lynal would be used within only 2 weeks. But Molloplast-B was compatible with alkaline peroxide denture cleansers.

• The Journal of Advanced Prosthodontics
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• v.7 no.1
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• pp.47-50
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• 2015

PURPOSE. This study aimed to discover a way to increase the bond strength between bis-acryl resins, using a comparison of the shear bond strengths attained from bis-acryl resins treated with light curing, pressure, oxygen inhibition, and heat. MATERIALS AND METHODS. Self-cured bis-acryl resin was used as both a base material and as a repair material. Seventy specimens were distributed into seven groups according to treatment methods: pressure - stored in a pressure cooker at 0.2 Mpa; oxygen inhibition- applied an oxygen inhibitor around the repaired material,; heat treatment - performed heat treatment in a dry oven at $60^{\circ}C$, $100^{\circ}C$, or $140^{\circ}C$. The shear bond strength was measured with a universal testing machine, and the shear bond strength (MPa) was calculated from the peak load of failure. A comparison of the bond strength between the repaired specimens was conducted using one-way ANOVA and Tukey multiple comparison tests (${\alpha}$=.05). RESULTS. There were no statistically significant differences in the shear bond strength between the control group and the light curing, pressure, and oxygen inhibition groups. However, the heat treatment groups showed statistically higher bond strengths than the groups treated without heat, and the groups treated at a higher temperature resulted in higher bond strengths. Statistically significant differences were seen between groups after different degrees of heat treatment, except in groups heated at $100^{\circ}C$ and $140^{\circ}C$. CONCLUSION. Strong bonding can be achieved between a bis-acryl base and bis-acryl repair material after heat treatment.

• The korean journal of orthodontics
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• v.48 no.2
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• pp.107-112
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• 2018

Objective: The aim of this study was to examine the properties of fiber-reinforced composite and stainless steel twisted retainers for orthodontic retention. Methods: Three different span lengths (5.0, 8.0, and 14.0 mm) of fiber-reinforced composite were investigated. The three fiber-reinforced composite retainer groups were subdivided according to the storage condition (dry and wet), resulting in a total of six groups. Each stainless steel and fiber-reinforced composite group was comprised of six specimens. The three-point bending flexural test was conducted using a universal testing machine. ANOVA was used to assess differences in the maximum load and maximum stress according to the span length, material, and storage condition. Post-hoc comparisons were performed if necessary. Results: The maximum stress and maximum load were significantly (p < 0.001) associated with the span length, material, and storage condition. The significant interaction between the material and span length (p < 0.001) indicated the differential effects of the material for each span length on the maximum stress and maximum load, with the difference between materials being the highest for the maximum span length. Conclusions: Our findings suggest that fiber-reinforced composite retainers may be an effective alternative for orthodontic retention in patients with esthetic concerns or allergy to conventional stainless steel wires.

• Journal of Technologic Dentistry
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• v.36 no.4
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• pp.239-246
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• 2014

Purpose: The purpose of this study was to compare the tensile strength and mechanical properties of orthodontic wire joints made by gas soldering and laser welding, with and without filling material, to identify the effectiveness and potential clinical application of laser welded orthodontic wires. Methods: Three joint configurations of orthodontic wire were used: diameter 0.9 to 0.9 mm wire, diameter 0.9 to 0.5 wire and diameter 0.9 mm wire to band. The joints were made using three different methods: gas soldering, laser welding with and without filling material. For each kind of joint configuration or connecting method 7 specimens were carefully produced. The tensile strengths were measured with a universal testing machine (Zwick/Roell, Instron, USA). The hardness measurements were carried out with a hardness tester(Future-Tech Co. Tokyo, Japan). Data were analyzed by AVOVA(p= .05) and Turkey HD test(p= .05). Results: In all cases, gas soldering joints were ruptured on a low level on tensile bonding strength. Significant differences between laser welding and gas soldering(p< .05) were found in each joint configuration. The highest tensile strength means were observed for laser welding, with filling material, of 0.9 to 0.9 mm wire joint. Conclusion: In conclusion, the elastic modulus and tensile strength means of laser soldering with filling material were the highest, and the tensile strength means of laser soldering were higher than those of gas soldering.

• Journal of the Korean Society of Safety
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• v.20 no.4 s.72
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• pp.14-19
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• 2005

One area in which composites have been used rather extensively is for fabricating pressure vessel. These structures can be readily manufactured by filament winding, which is, as far as composite fabrication techniques are concerned, a relatively inexpensive method for producing composite structures. Unfortunately, the higher strength material and fabrication costs are not the only disadvantages of fiber-reinforced polymer composites when they are compared to metals. Additionally, these materials tend to exhibit brittle behavior. This is of particular concern when they are subjected to a low-velocity impact during routine handling a significant amount of structural damage can be introduced into the composites. The goals of this paper are to understand the impact damage behavior and identify the effect of surface coating materials on impact resistance in filament wound composite pressure vessels. For these, a series of low velocity impact tests was performed on specimens cutting from the full scale pressure vessel by the instrumented impact testing machine. The specimens are classified into two types with and without surface protective material. The visualization for impact damage is made by metallurgical microscope. Based on the impact force history and damage, the resistance parameters were employed and its validity in identifying the damage resistance of pressure vessel was reviewed. As the results, the impact resistance of the filament wound composites and its dependency on the protective material were evaluated quantitatively.

• The Journal of Advanced Prosthodontics
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• v.14 no.4
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• pp.262-272
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• 2022

PURPOSE. This study aimed to analyze the shear bond strength between the 3D-printed denture base and the chairside relining material, according to the surface treatment. MATERIALS AND METHODS. Cylindrical specimens were prepared using DENTCA Denture Base II. The experimental groups were divided into 6 (n = 10): no surface treatment (C), Tokuyama Rebase II Normal adhesive (A), sandblasting (P), sandblasting and adhesive (PA), sandblasting and silane (PS), and the Rocatec system (PPS). After bonding the chairside relining material to the center of the specimens in a cylindrical shape, they were stored in distilled water for 24 hours. Shear bond strength was measured using a universal testing machine, and failure mode was analyzed with a scanning electron microscope. Shear bond strength values were analyzed using one-way analysis of variance, and Tukey's honest significant difference test was used for post-hoc analysis (P < .05). RESULTS. Group PPS exhibited significantly higher shear bond strength than all other groups. Groups P and PA displayed significantly higher bond strengths than the control group. There were no significant differences between groups PS and A compared to the control group. Regarding the failure mode, adhesive failure occurred primarily in groups C and A, and mixed failure mainly in groups P, PA, PS, and PPS. CONCLUSION. The shear bond strength between the 3D-printed denture base and the chairside relining material exhibited significant differences according to the surface treatment methods. It is believed that excellent adhesive strength will be obtained when the Rocatec system is applied to 3D-printed dentures in clinical practice.

• The Journal of Korean Academy of Prosthodontics
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• v.41 no.4
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• pp.493-502
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• 2003

Statement of problem : Removable partial denture and complete denture often require denture base relines to improve the fittness against tissue-bearing mucosa because of the gradual change in edentulous ridge contour and resorption of underlyng bony structure. Self-curing hard reline resins offers the immediate and relatively inexpensive means to be recondition the surface of denture base directly However weak bond between denture base resin and reline material can harbor bacteria, promote staining, or result in complete separation of the two materials. Purpose : The purpose of this study was to evaluate the effect of denture cleansers on bond strength and surface hardness of reline resin to denture base resin Denture base resin beams($60.0{\times}15.0{\times}3.0mm$) were made with Lucitone 199. Material and methods : 10mm section was removed from the center of each specimen. The samples were replaced in the molds and the space of l0mm sections were packed with Tokuso Rebase reline material. The specimens were immersed in denture cleansers (Polident, Cleadent) and were evaluated after 1 week, 2 weeks, and 4 weeks. The bond strength and surface hardness of self-curing hard reline materials to heat-curing denture base resin were measured using an UTM (universal testing machine). Results and conclusion : 1) There was no significant difference of usage, kind, and denture cleaner by application time on the bonding strength of self-curing hard reline resin to denture base resin. 2) There was no significant difference of usage, kind, and denture cleaner by application time on the surface hardness, but the surface hardness showed decreasing tendency, as the time of immersion was extended. 3) The failure modes of the specimens was initially adhesive failure and finally cohesive failure of self-curing hard reline resin.

• The Journal of Advanced Prosthodontics
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• v.8 no.5
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• pp.339-344
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• 2016

PURPOSE. Pre-surface treatments of coping materials have been recommended to enhance the bonding to the veneering ceramic. Little is known on the effect on shear bond strength, particularly with new coping material. The aim of this study was to investigate the shear bond strength of veneering ceramic to three coping materials: i) metal alloy (MA), ii) zirconia oxide (ZO), and iii) lithium disilicate (LD) after various pre-surface treatments. MATERIALS AND METHODS. Thirty-two (n = 32) discs were prepared for each coping material. Four pre-surface treatments were prepared for each sub-group (n = 8); a) no treatment or control (C), b) sandblast (SB), c) acid etch (AE), and d) sandblast and acid etch (SBAE). Veneering ceramics were applied to all discs. Shear bond strength was measured with a universal testing machine. Data were analyzed with two-way ANOVA and Tukey's multiple comparisons tests. RESULTS. Mean shear bond strengths were obtained for MA ($19.00{\pm}6.39MPa$), ZO ($24.45{\pm}5.14MPa$) and LD ($13.62{\pm}5.12MPa$). There were statistically significant differences in types of coping material and various pre-surface treatments (P<.05). There was a significant correlation between coping materials and pre-surface treatment to the shear bond strength (P<.05). CONCLUSION. Shear bond strength of veneering ceramic to zirconia oxide was higher than metal alloy and lithium disilicate. The highest shear bond strengths were obtained in sandblast and acid etch treatment for zirconia oxide and lithium disilicate groups, and in acid etch treatment for metal alloy group.

• Journal of The Korean Society of Agricultural Engineers
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• v.57 no.6
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• pp.141-152
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• 2015

Most of agricultural structures are consisted of complex components and exposed to various boundary conditions. There have been no ways to express those structures exactly for model experiment. As an alternative, 3D printer can produce any type of solid model. However, there are limited informations related to structural experiments using 3D printer. The object of this study gives the basic informations to structural engineers who try to use 3D printer for model experiment. When PLA was used as a supplier for 3D printer, the outcomes showed less heat deformation to compare with ABS. To test the material properties, two kinds of experiments (three-point flexibility test and compression test) were executed using universal testing machine. In three-point flexibility test, plastic hinge and its deformation were developed as observed in material such as steel. The behavior was in a linear elastic state, and elastic bending modulus and yield force were evaluated. In the compression test using unbraced columns with hinge-hinge boundary condition, the constant yield forces were observed regardless of different lengths in all columns with same section size, whereas the compressive elastic modulus was increased as the length of column was increased. The suggested results can be used for model experiments of various agricultural structures consisted of single material.

• The Journal of Advanced Prosthodontics
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• v.11 no.2
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• pp.95-104
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• 2019

PURPOSE. To evaluate the effect of surface treatments and repair materials on the shear bond strength and to measure the fracture toughness of CAD/CAM provisional restoration materials. MATERIALS AND METHODS. Four CAD/CAM (3D printing: Nextdent C&B and ZMD-1000B Temporary, CAD/CAM resin block: Yamahachi PMMA disk and Huge PMMA block) and four conventional (monometacrylate: Jet and Alike, dimetacrylate: Luxatemp and Protemp 4) materials were selected to fabricate disk-shaped specimens and divided into six groups according to surface treatment (n=10). CAD/CAM materials were repaired with Jet or Luxatemp, while conventional materials were repaired with their own materials. The shear bond strength was measured by using universal testing machine. Ten rectangular column-shaped specimens for each material were fabricated to measure the fracture toughness by single edge v notched beam technique. Statistical analysis was performed by one-way ANOVA. RESULTS. The highest shear bond strength of CAD/CAM materials was achieved by SiC paper + sandblasting. It was also accomplished when repairing 3D printing materials with Luxatemp, and repairing CAD/CAM resin blocks with Jet. Yamahachi PMMA disk showed the highest fracture toughness. Nextdent C&B showed the lowest fracture toughness value but no statistically significant difference from Alike and Luxatemp (P>.05). CONCLUSION. In order to successfully repair the CAD/CAM provisional restoration, mechanical surface treatment and appropriate repair material according to the CAD/CAM material type should be selected. The CAD/CAM provisional materials have proper mechanical properties for clinical use as compared to conventional materials.