• Restorative Dentistry and Endodontics
• /
• v.46 no.4
• /
• pp.54.1-54.10
• /
• 2021

Objectives: The purpose of this study was to quantify phase transformation after hydrofluoric acid (HF) etching at various concentrations on the surface of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP), and to evaluate changes in bonding strength before and after thermal cycling. Materials and Methods: A group whose Y-TZP surface was treated with tribochemical silica abrasion (TS) was used as the control. Y-TZP specimens from each experimental group were etched with 5%, 10%, 20%, and 40% HF solutions at room temperature for 10 minutes. First, to quantify the phase transformation, Y-TZP specimens (n = 5) treated with TS, 5%, 10%, 20% and 40% HF solutions were subjected to X-ray diffraction. Second, to evaluate the change in bond strength before and after thermal cycling, zirconia primer and MDP-containing resin cement were sequentially applied to the Y-TZP specimen. After 5,000 thermal cycles for half of the Y-TZP specimens, shear bond strength was measured for all experimental groups (n = 10). Results: The monoclinic phase content in the 40% HF-treated group was higher than that of the 5%, 10%, and 20% HF-treated groups, but lower than that of TS-treated group (p < 0.05). The 40% HF-treated group showed significantly higher bonding strength than the TS, 5%, and 10% HF-treated groups, even after thermal cycling (p < 0.05). Conclusions: Through this experiment, the group treated with SiO₂ containing air-borne abrasion on the Y-TZP surface showed higher phase transformation and higher reduction in bonding strength after thermal cycling compared to the group treated with high concentration HF.

• The Journal of Korean Academy of Prosthodontics
• /
• v.42 no.5
• /
• pp.501-513
• /
• 2004

Purpose : The purpose of this study was to evaluate the effects of etching time on shear bond strength of four resin cements to IPS Empress 2 ceramic. Material and Methods: Forty rectangular shape ceramic specimens ($10{\times}15{\times}3.5mm$ size) were used for this study. The ceramic specimens divided into four groups and were etched with 10% hydrofluoric acid for 0, 10, 30, 60, 180, 300, 420, 600, and 900 seconds respectively. Etched surfaces of ceramic specimens were coated with ceramic adhesive system and bonded with four resin cement (Variolink II, Panavia F, Panavia 21, Super-Bond C&B) using acrylic glass tube. All cemented specimens were tested under shear loading untill fracture on universal testing machine at a crosshead speed 1mm/min: the maximum load at fracture (kg) was recored. Shear bond strengh data were analyzed with oneway analysis of variance and Tukey HSD tests (p<.05). Etched ceramic surfaces (0-, 60-, 300-, and 600-seconds etching period) and fracture surfaces after shear testing were examined mophologically using scanning electron microscopy. Results : Ceramic surface treatment with 10% hydrofluoric acid improved the bond strength of three resin cement except for Super-Bond C&B cement. Variolink II (41.0$\pm$2.4 MPa) resin cement at 300-seconds etching time showed statistically higher shear bond strength than the other resin cements (Panavia F: 28.3$\pm$2.3 MPa, Panavia 21: 21.5$\pm$2.2 MPa, Super-Bond C&B: 16.7$\pm$1.6 MPa). Ceramic surface etched with 10% hydrofluoric acid for 300 seconds showed more retentive surface texture. Conclusion: Within the limitation of this study, Variolink II resin cement are suitable for cementation of Empress 2 all-ceramic restorations and etching with 10% hydrofluoric acid for 180 to 300 seconds is required to enhance the bond strength.

• Restorative Dentistry and Endodontics
• /
• v.22 no.1
• /
• pp.144-155
• /
• 1997

This study evaluated shear bond strength between porcelain and resin cement according to various surface treatments of porcelain, and surface condition of debonded porcelain. 50 porcelain specimens(Celay block A2M7) and composite resin specimens(Clearfil Photo-Bright) were prepared, and divided into 5 experimental groups according to the treatment method of porcelain surface. 5 experimental groups by surface treatments were as follows; CONTROL Group : No surface treatment was done on the surface of porcelains. SAND Group : The surface of porcelains were sandblasted with $50{\mu}m$ aluminum oxide for 5 seconds. HF Group: The surface of porcelains were etched with 8% Hydrofluoric acid for 4 minutes. SIL Group: The surface of porcelains were coated with silane coupling agent and heated at $100^{\circ}C$ for 5 minutes. SAND+HF+SIL Group : The surface of porcelains were sandblasted with $50{\mu}m$ aluminum oxide for 5 seconds and etched with 8% Hydrofluoric acid for 4 minutes, and coated with silane coupling agent and heated at $100^{\circ}C$ for 5 minutes. After surface treatments on the prepared porcelain surface two pastes of Panavia 21$^{(R)}$ were mixed, they were applied between composite resin block and porcelain surface, and then excessive resin cements were removed, and its margin was surrounded with Oxyguard II. All specimens were stored for 24 hours in water at $37^{\circ}C$ and tested with Instron testing machine between porcelains and resin cements, and debonded porcelain surfaces were observed under Scanning Electon Microscope(Hitachi S-2300) at 20kvp. The values from each group were compared statistically by Student's t-test. The obtained results were as follows; 1. The shear bond strength without surface treatment of porcelain was the lowest among all experimental groups(p<0.05). 2. The detached porcelain surface with sandblasting alone had more remarkable cracks than with only Hydrofluoric Acid or Silane coupling 2gent, but showed the lowest value of shear bond strength among surface treated groups(p<0.05), 3. When porcelain surface was treated by hydrofluoric acid, it affected shear bond strength more than silane coupling agent, but there were no significant statistical differences(p>0.05). 4. When three methods were combined to increase shear bond strength between porcelains and resin cements, its value was the highest than the others(p<0.05). 5. In Scannig Electron Micrograph of detached porcelain surface with no treatment, the sample revealed adhesive failure between the porcelain and resin cement whereas detached porcelain surface with combination of three method cohesive failure on the porcelain.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.22 no.2
• /
• pp.149-159
• /
• 2006

Statement of problem. Porcelain repair mainly involves replacement with composite resin, but the bond strength between composite resin and all-ceramic coping materials has not been studies extensively. Purpose. The objective of this study was to investigate the influence of composite resin and ceramic etching pattern on shear bond strength of Empress2 ceramic and observe the change of microstructure of ceramic according to etching methods. Material and methods. Eighty-five cylinder shape ceramic specimens (diameter 5mm, IPS Empress 2 core materials) embeded by acrylic resin were used for this study. The ceramic were specimens divided into sixteen experimental groups with 5 specimens in each group and were etched with phosphoric acid(37%, 65%) & hydrofluoric acid (4%, 9%) according to different etching times(30s, 60s, 120s 180s). All etched ceramic surfaces were examined morphologically using SEM(scanning electron microscopy). Etched surfaces of ceramic specimens were coated with silane (Monobond-S) & adhesive(Heliobond) and built up composite resin using Teflon mold. Accomplished specimens were tested under shear loading until fracture on universal testing machine at a crosshead speed 1mm/min; the maximum load at fracture(kg) was recorded. Shear bond strength data were analyzed with one way ANOVA and Duncan tests.(P<.05) Results. Maximum shear bond strength was $30.07{\pm}2.41(kg)$ when the ceramic was etched with 4% hydrofluoric acid at 120s. No significant difference was found between phosphoric etchant group and control group with respect to shear bond strength. Conclusion. Empress 2 ceramic surface was not etched by phosphoric acid, but etched by hydrofluoric acid.

• Restorative Dentistry and Endodontics
• /
• v.27 no.6
• /
• pp.569-576
• /
• 2002

This study was peformed to evaluate the interfacial shear bond strength of base (direct and indirect) and repair composites with aging and surface treatment methods. Direct composite resin specimens ($Charisma^{\circledR}$, Heraeus Kulzer, Germany) were aged for 5 min, 1 hour, 24 hours, and 1 week in $37^{\circ}C$ distilled water before surface treatment, and then divided into five groups Group 1, grinding; Group 2, grinding and application of bonding agent, Group 3, grinding, etching with 37% phosphoric acid for 30sec, and application of bonding agent, Group 4, grinding, etching with 37% phosphoric acid for 30sec, silane treatment, and application of bonding agent ; Group 5, grinding, etching with 4% hydrofluoric acid for 30sec. silane treatment, and application of bonding agent. Indirect composite resin specimens ($Artglass^{\circledR}$, Heraeus Kulzer, Germany) were aged for 1 week in $37^{\circ}C$ distilled water and divided into seven groups Group 1 - Group 5, equal to Charisma specimens; Group 6, grinding, etching with 37% phosphoric acid for 60sec, silane treatment, and application of bonding agent; Group7, grinding, etching with 4% hydrofluoric acid for 60 sec, silane treatment, and application of bond-ing agent. The repair material($Charisma^{\circledR}$) was then added on the center of the surface (5 mm in diameter. 5 mm in height). The shear bond strength was tested and the data was analyzed using one-way ANOVA and the Student- Newman-Keuls test. The following conclusions were drawn. 1 The shear bond strength of $Charisma^{\circledR}$ specimens aged for 1 hour was significantly higher in Group 2 and Group 5 than in Group 1 (p<0.05), and that of $Charisma^{\circledR}$ specimens aged for 1 week was signifi-cantly higher in Group 3 and Group 5 than in Group 1 (p<0.05). No significant difference was found in the bond strength of specimens aged for 5 min and 24 hours. 2. In Group 2 of the $Charisma^{\circledR}$ specimens, there was significant difference between the bond strength of 24 hours and that of 1 week (p<0.05). 3. In Group 4 of the $Charisma^{\circledR}$ specimens, the shear bond strength of specimens aged for 24 hours was significantly higher than the others(p<0.05) 4. There was no significant difference between the shear bond strength of the $Artglass^{\circledR}$ specimens, 5. Most of the $Charisma^{\circledR}$ specimens showed cohesive fractures. Artglass^{\circledR}$ specimens that were etched with acid (phosphoric or hydrofluoric) for 30 sec showed more cohesive fractures.

• Journal of the Korea Safety Management & Science
• /
• v.20 no.3
• /
• pp.27-36
• /
• 2018

The steel pipe manufacturing industry deals with facilities and materials. Especially thermal facilities are close to vapor cloud explosion (VCE) and may cause secondary damage to facilities because they deal with corrosive substances such as hydrofluoric acid, sulfuric acid and acid, fire, explosion, leakage etc. It is in danger. In this study, hazard identification method was conducted using HAZOP techniques and quantitative risk analysis was conducted using e-CA, a program that supports accident impact analysis. Equipment in the influence range of ERPG - 3 was determined to be a facility requiring replacement. It was decided that neutralization is necessary using slaked lime. Based on the cost of loss, We presented the proper replacement which is the timing of the dangerous facility. As a result, It was ideal to replace the facilities with 20 years of heat treatment facilities, one year of hydrofluoric acid storage tank, 20 years of sulfuric acid storage tank, and 5 years of hydrochloric acid storage tank.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.12 no.5
• /
• pp.731-736
• /
• 2017

In this paper, we report the fabrication of concave surface fiber tips for optical resonators. It was confirmed that the radius of curvature on fiber end can be controlled by introducing the hydrofluoric acid solution and the wavelength of $1.55{\mu}m$ laser which is absorbed well in the etchant to induce the photothermal effect. Using the microscope images, we observed the proposed concave fiber tip fabrication method is effective to make the controllable concave tips. We also observed changes in the size of the beam emitted from the tips with the various radius of curvature using the beam profiler. The authors believe that the proposed method will be applied to resonators for optical communications.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.28 no.1
• /
• pp.25-32
• /
• 2017

In this paper, a fabrication method of low-loss tapered optical fibers coupler using hydrofluoric acid with surface tension driven is proposed. The proposed fabrication method is very simple compared to flame-based method, and shows low excess insertion losses compared to polishing method. The adiabatic-tapered structure along the coupling region of the coupler shows wavelength independent characteristic over the C-band in optical communication system, and will enable promising applications.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.27 no.12
• /
• pp.2085-2091
• /
• 2003

An ultrasonic machining process has been known as efficient and economical means fer precision machining of glass or ceramic materials. However, because of its complexity, the mechanism of the machining process is still not well understood. Therefore, it is hard to optimize the process parameters effectively. The conventional ultrasonic machining which uses the abrasive slurry only, furthermore, is time-consuming and gives the relatively rough surface. In order to increase the material removal rate and improve the integrity of the machined surface, we have introduced the novel ultrasonic machining technique, Chemical-assisted UltraSonic Machining(CUSM). The desktop-style micro ultrasonic machine has been developed and the z-axis feed is controlled by the constant load control algorithm. To obtain the chemical effects, the low concentration HF(hydrofluoric acid) solution, which erodes glass, added to alumina slurry. Through various experiments and comparison with conventional results, the superiority of CUSM is verified. MRR increases over 200%, the surface roughness is improved and the machining load decreases dramatically.

• Journal of Soil and Groundwater Environment
• /
• v.20 no.3
• /
• pp.65-73
• /
• 2015

The hydrofluoric acid (HF) leakage accident occurred on September 2012 in Gumi, Korea affected the surrounding soils and plants. In this study, we investigated fluoride migration in Gumi area through geochemical properties of soil-liquid phase (pore water F and water-soluble F). The concentrations of porewater F and water-soluble F were obtained from N.D (Not detected) to 9.79 mg/L and from 0.001 to 21.4 mg/L, respectively. F in pore water seemed to be affected by artificial and natural origin, and PHREEQC results implied that fluorite is F control factor. F concentrations of soil and soil-liquid phase did not exceed concern level of regulatory criteria and showed similar trends compared by previous studies. Therefore, F contents remained in the soil and soil-liquid phase were considered to be not affected by HF leakage accident.