• Journal of Periodontal and Implant Science
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• 제31권2호
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• pp.333-344
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• 2001

The present study was performed to evaluate the effect of tetracycline - HCl on the change of implant surface microstructure according to application time. Implants with pure titanium machined surface and titanium plasma-sprayed surface were utilized. Implant surface was rubbed with 50mg/ml tetracycline - HCl solution for 1 min., $1\frac{1}{2}\;min$., 2 min., $2\frac{1}{2}\;min$. and 3min. respectively in the test group and with saline for 1 min. in the control group. Then, the specimens were processed for scanning electron microscopic observation. The following results were obtained. 1. Pure titanium machined surfaces conditioned with saline for 1 min., showed a few shallow grooves and ridges and were less irregular. 2. Pure titanium machined surfaces conditioned with 50mg/ml tetracycline - HCl solution showed more irregular and corrosive surfaces compared to the control group irrespective of the application time of tetracycline - HCl solution. 3. Titanium plasma-sprayed surfaces conditioned with saline for 1 min., were deposited with round amorphous particles and showed round or irregular pores that can be connected to each other. 4. The irregularity of titanium plasma-sprayed surfaces conditioned with 50mg/ml tetracycline - HCl solution was lessened and the flattened areas were wider relative to the application time of tetracycline - HCl solution. 5. Titanium plasma-sprayed surfaces conditioned with tetracycline - HCl solution for 1 min. and $1\frac{1}{2}\;min$. were very similar to that of the control group, but the surfaces conditioned for 2 min., $2\frac{1}{2}\; min$. and 3 min. were changed. In conclusion, pure titanium machined surfaces were changed irrespective of the application time of tetracycline - HCl solution. And titanium plasma-sprayed surfaces conditioned with tetracycline - HCl solution began to be changed from $1\frac{1}{2}\;min$. This results will be applicable to the regenerative procedures for peri-implantitis treatment.

• Tribology and Lubricants
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• 제16권4호
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• pp.253-258
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• 2000

Frictional behavior of wire electric discharge machined surfaces of spheroidized annealed STDll steel was investigated. The surfaces were produced with a various series of finish cuts where pulse energy was reduced with increase in the number of finish cuts. Roughness and micro-hardness of the surfaces were also measured. It is observed that the increase in the number of finish cuts produces the surface exhibiting lower frictional resistance followed by higher resistance after considerable wear. Effects of finish cuts on the friction characteristics are discussed with the aid of roughness and micro-hardness of the surfaces.

• 한국기계가공학회지
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• 제11권3호
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• pp.13-18
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• 2012

We investigated the cell activity of controlled titanium surface using various grinding methods including ELID (Electrolytic In-Process Dressing) grinding method. The influence of titanium surface condition by each grinding process on the cell activity was evaluated by ALP activity of MSC(Mesenchymal Stem Cells). The ALP activity of controlled surface by ELID grinding process using # 2000 wheel was higher than that of other titanium surface. The morphological, chemical properties of machined surface by grinding method was observed using various analytical method.

• 한국정밀공학회지
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• 제6권4호
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• pp.94-102
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• 1989

The effect of plastic strain on the surface integrity of mild steel (SS 41) was studied. This paper shows that the recrystallization technique is adequate to evaluate the plastic strain in a machined surface experimentally. The relations between the plastic strain and the machining conditions are quantitatively evaluated by using the recrystallization technique. The obtained results are summarized as follows. 1. The surface integrity of steel is considerably influenced by the amount of surface region deformation produced by changes in cutting conditions. 2. The plastic strain in machined surface produced by changes of the cutting conditions is evaluated by the recyrstallization technique. 3. The plastic strain increases with the increase of depth of cut and the decrease of rake angle. 4. When the cutting force is high and the rake angle is small, the value of maximum true strain reaches to high. 5. The maximum true strain is related to the cutting energy, and the values increase with the increase of the unit shear and total engergy in constant depth with the increase of the energy values.

• 대한치과보철학회지
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• 제45권1호
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• pp.71-84
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• 2007

Statement of problem: Implant surface characteristics plays an important role in clinical success and many studies have been made for improvement of success by changing surface roughness. Purpose: Appropriate increase of surface roughness increases the activity of osteoblast and enhance contact and retention between bone and implant. Material and method- Machined, SLA and RBM surface implants, which are the most commonly used implants were implanted into the tibia of rabbits and after 1 week, 4 weeks, 8 weeks and 12 weeks there were histologic and histomorphometric analysis and study for bone gradient and change of Ca/P ratio using EDS(Energy Dispersive X-ray Spectroscope). Results: Comparison of bone-implant contact showed no significant difference among each implant. In comparison of bone area rates, SLA showed higher value with significant difference at 1 week and 4 weeks, and SLA and RBM at 8 weeks than Machined implant (p<0.05). In analysis of bone constituents with EDS, titanium was specifically detected in new bones and the rates were constant by surface treatment method or period. In case of Ca/P ratio, according to surface treatment method, each group showed significant difference. Lots of old bone fragments produced during implantation remained on the rough surface of RBM implant surface and each group showed histological finding with active synthesis of collagen fibers until 12 weeks. In transmission electronic microscopic examination of sample slice after elapse of twelve weeks, tens nm of borderline (lamina limitans like dense line)was seen to contact the bone, on the interface between bone and implant. Conclusion: SLA and RBM implant with rough surface shows better histomorphometrical result and the trend of prolonged bone formation and maturation in comparison with Machined implant. In addition, implant with rough surface seems to be helpful in early stage bone formation due to remaining of old bone fragments produced in implantation. From the results above, it is considered to be better to use implant with rough surface in implantation.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 추계학술대회 논문집
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• pp.106-110
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• 2001

The ball-end milling process is widely used in the die/mold industries, and it is very suitable for the machining of free-form surfaces. However, this process is inherently inefficient process to compared with the end-milling or face milling process, since it relays upon the machining at the cutter/surface contact point. The machined part is the result of continuous point-to-point machining on the free-form surface. And cusps (or scallops) remain at the machined part along the cutter paths and they give the geometrical roughness of the workpiece. Thus, for the good geometrical roughness of the workpiece, it is required very tightly spaced cutter paths in this ball-endmilling process. However, with the tight cutter paths, the geometrical roughness of the workpiece is not regular on the workpiece since the cusp height is variable in the previously developed ISO-parametric or Cartesian machining methods. This paper suggests a method of tool path generation which makes the geometrical roughness of workpiece be constant through the machined surface. In this method, Ferguson Surface design Model is used and cusp height is derived from the instantaneous curvatures. And, to have constant cusp height, an increment of parameter u or v is estimated along the reference cutter path. In ball-end milling experiments, the cusp pattern was examined, and it was proved that the geometrical roughness could be regular by suggested tool path generation method.

• 한국정밀공학회지
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• 제27권10호
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• pp.45-51
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• 2010

Electrical discharge drilling (ED-drilling) is a widespread machining method used to bore small holes with a high aspect ratio. This paper presents additional methods by which ED-drilling can improve machining speed, tool wear, and machined surface quality. Firstly, for high machining speed, and low tool wear, a new-type electrode that was ground on one side or both sides of the cylindrical electrodes was suggested to expel debris. The debris which is generated during the machining process can cause sludge deposition and secondary discharge problems: major reasons to decrease machining speed. This new-type electrode also reduced tool wear that was due to the decrease of unstable discharge in a machining gap by helping to expel waste water and debris from the gap. Secondly, to improve the machined surface roughness, an electrolyzation process was included after drilling. This process made the machined surface smooth by means of an electrochemical reaction between an electrode and a workpiece. In this study, the machining speed, electrode wear, and surface roughness were improved by the newtype electrode and the electrolytic process.

• Journal of Periodontal and Implant Science
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• 제32권4호
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• pp.697-709
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• 2002

The present study was performed to evaluate the effect of citric acid on the change of implant surface microstructure according to application time. Implants with pure titanium machined surface, titanium plasma-sprayed surface, and sand-blasted, large grit, acid etched surface were utilized. Implant surface was rubbed with pH 1 citric acid for $\frac{1}{2}$ min., 1 min., 1 $\frac{1}{2}$ min., 2 min., and 3min, respeaively in the test group and implant surface was not treated in the control group. Then, the specimens were processed for scanning electron microscopic observation. The following results were obtained. 1. Both test and control group showed a few shallow grooves and ridges in pure titanium machined surface implants. There were not significant differences between two groups. 2. In titanium plasma-sprayed surfaces, round or amorphous particles were deposited irregularly. The irregularity of titanium plasma-sprayed surfaces conditioned with pH 1 citric acid was lessened and the cracks were increased relative to the application time of pH 1 citric acid. 3. Sand-blasted, large grit, acid etched surfaces showed the macro/micro double roughness. The application of pH 1 citric acid didn't change the characteristics of the sand-blasted, large grit, acid etched surfaces. In conclusion, the application of pH 1 citric acid to titanium plasma-sprayed surface is improper. And pure titanium machined surface implants and sand-blasted, large grit, acid etched surface implants can he treated with pH 1 citric acid for peri-implantitis treatment if the detoxification of these surfaces could be evaluated.

• 융복합기술연구소 논문집
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• 제2권2호
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• pp.25-29
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• 2012

Micro machining technologies have been required to satisfy various conditions in a high-technology industry. Micro electrochemical process is one of the most precision machining methods. Micro electrochemical process has been divided into electrochemical etching through protective layer and electrochemical machining using ultrashort voltage pulses. Micro shaft can be fabricated by electrochemical etching. The various protective layers such as photo-resist, oxide layer and oxidized recast layer have been used to protect metal surface during electrochemical etching. Micro patterning on metal surface can be machined by electrochemical etching through protective layer. Micro hole, groove and structures can be easily machined by electrochemical machining using ultrashort voltage pulses. Recently, the groove with subnanometer was machined using AFM.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1995년도 특별강연 및 추계학술발표 개요집
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• pp.214-217
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• 1995

In order to investigate characteristics of surface fatigue crack propagation from a pit shaped surface defect which frequently exists near weld joints, SS400 steel with thickness of 12mm, which generally used for structure members, was submerged-arc welded with butt type and machined for both surface. The weld joints were devided into 5 regions, weld metal, boundary between heat affected zone (HAZ), HAZ, boundary between HAZ and base metal, and base metal. Specimens from each region were machined for a pit shaped initial surface defect with aspect ratio of 2. characteristics of surface fatigue crack por pagation from the defect under the same loading condition were compared and discussed.