STATEMENT OF PROBLEM: Implant screw loosening has been remained problem in restorative practices. Surface treatment of screw plays a role of preventing screw from loosening in implant screw mechanism. PURPOSE: The purpose of this study was to investigate surface characteristics of TiN and ZrN film ion plated screw with titanium and gold alloy screw and to evaluate wear resistance, surface roughness, and film adhesion on screw surface using various instruments. MATERIAL AND METHODS: GoldTite screws and titanium screws provided by 3i (Implant Innovation, USA) and TorqTite screws or titanium screws by Steri-Oss (Nobel Biocare, USA) and gold screws and titanium screws by AVANA (Osstem Implant, korea) were selected. Ion plating which is much superior to other surface modification techniques was carried out for gold screws and titanium screws using Ti and Zr coating materials with nitrogen gas. Ion nitrided surface of each abutment screw was observed with field emission scanning electron microscopy(FE-SEM), micro-diamond scratch tester, vickers hardness tester, and surface roughness tester. RESULTS: 1) The surface of gold screw and GoldTite is more smooth than ones of other kinds of non coated screw. 2) The ZrN and TiN coated surface is the more smooth than ones of other kinds of screw. 3) The hardness of TiN and ZrN coated surface showed higher than that of non coated surface. 4) The TiN coated titanium screw and ZrN coated gold screw have a good wear resistance and adhesion on the surface. 5) The surface of ZrN coated screw showed low surface roughness compared with the surface of TiN coated screw. CONCLUSION: It is considered that the TiN and ZrN coated screw which would prevent a screw from loosening can be appilcable to implant system and confirmed that TiN and ZrN film act as lubricant on surface of screw due to decrease of friction for recycled tightening and loosening.
Alloys ; Dental Implants* ; Friction ; Hardness ; Hardness Tests ; Nitrogen ; Tin ; Titanium

PURPOSE: The aim of this study is to evaluate the effect of TiN coating of abutment screw on the unscrewing torque. MATERIAL AND METHODS: Titanium and Gold-Tite abutment screws were classified into two groups, Group A and C respectively, as control groups. Titanium abutment screws with TiN coatings were also classified into two groups, Group B and D, as experimental ones. Group A and B were tightened to 20 Ncm input torque, and Group C and D were tightened to 32 Ncm torque. Detorque values were measured with digital torque gauge during repeated closing and opening experiment. RESULTS: Abutment screws with TiN coating (Group B and D) showed statistically significant higher mean detorque values than those of Group A and C. DISSCUSION: Physical properties of TiN coating, such as low friction coefficient, high hardness and wear resistance, might contribute to higher detorque values. CONCLUSION: It is suggested that TiN coating of abutment screw help to reduce the risk of screw loosening and improve the stability of screw joint.
Friction ; Hardness ; Joints ; Tin* ; Titanium ; Torque

PURPOSE: The purpose of this study was to investigate the corrosion behaviors of dental implant alloy after micro-sized surface modification in electrolytes containing Mn ion. MATERIALS AND METHODS: Mn-TiO₂ coatings were prepared on the Ti-6Al-4V alloy for dental implants using a plasma electrolytic oxidation (PEO) method carried out in electrolytes containing different concentrations of Mn, namely, 0%, 5%, and 20%. Potentiodynamic method was employed to examine the corrosion behaviors, and the alternating-current (AC) impedance behaviors were examined in 0.9% NaCl solution at 36.5℃±1.0℃ using a potentiostat and an electrochemical impedance spectroscope. The potentiodynamic test was performed with a scanning rate of 1.667 mV s⁻¹ from −1,500 to 2,000 mV. A frequency range of 10⁻¹ to 10⁵ Hz was used for the electrochemical impedance spectroscopy (EIS) measurements. The amplitude of the AC signal was 10 mV, and 5 points per decade were used. The morphology and structure of the samples were examined using field-emission scanning electron microscopy and thin-film X-ray diffraction. The elemental analysis was performed using energy-dispersive X-ray spectroscopy. RESULT: The PEO-treated surface exhibited an irregular pore shape, and the pore size and number of the pores increased with an increase in the Mn concentration. For the PEO-treated surface, a higher corrosion current density (I(corr)) and a lower corrosion potential (E(corr)) was obtained as compared to that of the bulk surface. However, the current density in the passive regions (I(pass)) was found to be more stable for the PEO-treated surface than that of the bulk surface. As the Mn concentration increased, the capacitance values of the outer porous layer and the barrier layer decreased, and the polarization resistance of the barrier layers increased. In the case of the Mn/Ca-P coatings, the corroded surface was found to be covered with corrosion products. CONCLUSION: It is confirmed that corrosion resistance and polarization resistance of PEO-treated alloy increased as Mn content increased, and PEO-treated surface showed lower current density in the passive region.
Alloys ; Corrosion ; Dental Implants ; Dielectric Spectroscopy ; Electric Impedance ; Electrolytes ; Manganese ; Methods ; Microscopy, Electron, Scanning ; Plasma ; Spectrum Analysis ; X-Ray Diffraction

PURPOSE: This study compared the effect of three intraoral repair systems on the bond strength between composite resin and zirconia core. MATERIALS AND METHODS: Thirty zirconia specimens were divided into three groups according to the repair method: Group I- CoJet(TM) Repair System (3M ESPE) [chairside silica coating with 30 microm SiO2 + silanization + adhesive]; Group II- Ceramic Repair System (Ivoclar Vivadent) [etching with 37% phosphoric acid + Zirconia primer + adhesive]; Group III- Signum Zirconia Bond (Heraus) [Signum Zirconia Bond I + Signum Zirconia Bond II]. Composite resin was polymerized on each conditioned specimen. The shear bond strength was tested using a universal testing machine, and fracture sites were examined with FE-SEM. Surface morphology and wettability after surface treatments were examined additionally. The data of bond strengths were statistically analyzed with one-way ANOVA and Tamhane post hoc test (alpha=.05). RESULTS: Increased surface roughness and the highest wettability value were observed in the CoJet sand treated specimens. The specimens treated with 37% phosphoric acid and Signum Zirconia Bond I did not show any improvement of surface irregularity, and the lowest wettability value were found in 37% phosphoric acid treated specimens. There was no significant difference in the bond strengths between Group I (7.80 +/- 0.76 MPa) and III (8.98 +/- 1.39 MPa). Group II (3.21 +/- 0.78 MPa) showed a significant difference from other groups (P<.05). CONCLUSION: The use of Intraoral silica coating system and the application of Signum Zirconia Bond are effective for increasing the bond strength of composite resin to zirconia.
Ceramics ; Collodion ; Phosphoric Acids ; Polymers ; Silicon Dioxide ; Wettability ; Zirconium

BACKGROUND: The incidence of invasive aspergillosis has been increasing as the number of severe immunocompromised hosts has increased. We reviewed representative cases of invasive aspergillosis to describe clinical manifestations and treatment outcome. METHODS: We identified 40 cases of invasive aspergillosis on the ground of pathologic and radiologic findings from January 1991 to December 2000 and reviewed medical records and laboratory data. RESULTS: Forty cases of invasive aspergillosis included 28 'definite' cases and 12 'probable' cases. Major involved organs of invasive aspergillosis were lung (n=23, 57.5%), sinus (n=11, 27.5%), brain (n=3, 7.5%), spine (n=1, 2.5%), skull (n=1, 2.5%), and small bowel (n=1, 2.5%). Underlying diseases and risk factors were hematologic malignancies (n=21, 52.5%), high-dose steroid treatment (n=8, 20%), post-transplantation of solid organ (n=2, 5%), and ectopic ACTH syndrome (n=1, 2.5%). Immunocompetent hosts including DM patients were 8 cases (20%) and their major involved sites were sinus (n=4) and brain (n=2). Crude mortality rate of total invasive aspergillosis after 3 months and 12 months were 30% and 47.5%, respectively. 3-month and 12-month mortality rate for pulmonary aspergillosis (n=23) were 39%, 61% and those for extrapulmonary aspergillosis (n=17) were 18 %, 29%. Patients with hematologic malignancy (n=21) were in 33%, 57%, other immunocompromised hosts (n=11) were in 45%, 45%, and immunocompetent hosts (n=8) were in 0%, 25%. Patients with aggravated underlying diseases and sustained risk factors (n=20) were in 60%, 70% and patients with improved underlying diseases and no risk factor (n=20) were in 0%, 20%. CONCLUSION: Invasive aspergillosis mainly developed in severe immunocompromised hosts, but invasive sinus aspergillosis and cerebral aspergillosis occasionally developed in apparently immunocompetent hosts. The degree of immunosuppression and severity of underlying diseases affected the treatment outcome of invasive aspergillosis.
ACTH Syndrome, Ectopic ; Aspergillosis* ; Brain ; Hematologic Neoplasms ; Humans ; Immunocompromised Host ; Immunosuppression ; Incidence ; Lung ; Medical Records ; Mortality ; Pulmonary Aspergillosis ; Risk Factors ; Skull ; Spine ; Treatment Outcome*

BACKGROUND: This study was conducted to evaluate risk factors for infection and treatment outcome of bloodstream infection due to extended spectrum beta-lactamases(ESBL)-producing K. pneumoniae. METHODS: ESBL production was evaluated by NCCLS guidelines and/or double-disk synergy test in K. pneumoniae blood isolates stored from January, 1998 to April, 2002. Sixty patients with bloodstream infection due to ESBL-producing K. pneumoniae (case patients) were compared with 159 matched control patients with bloodstream infection of non-ESBL-producing K. pneumoniae. Retrospective case-control study was performed. RESULTS: There were no significant differences in age, sex, APACHE II score, and the primary site of infection between the case and control groups. In multivariate analysis, significant independent risk factors associated with bloodstream infection due to ESBL-producing K. pneumoniae were urinary catheterization, invasive procedure within previous 72 hours, and the number of antibiotics administered within previous 30 days. In clinical response at 72 hours after initial antibiotic treatment, complete response rate was higher in the controls (13.3% vs. 40.3%, respectively, P<0.001), however, treatment failure rate was higher in the cases (33.3% vs. 11.9%, respectively, P<0.001). Overall 7- day mortality rates in the cases and the controls were was 20% (12/60) and 15.7% (25/159) (P= 0.451), respectively, and overall 30-day mortality rates were 30% (18/60) and 24.5% (39/159), respectively (P=0.410). When the patients with bloodstream infection of ESBL-producing organism were evaluated and the patients who received inadequate definitive antibiotic treatment were excluded, delayed effective antibiotic treatment was found to be not associated with higher mortality. CONCLUSION: In patients infected with ESBL-producing K. pneumoniae bacteremia, clinical response rate at 72 hours after antimicrobial therapy was lower, but the increase of mortality rate was not significant. Delayed effective antibiotic treatment was not associated with higher mortality, when definitive appropriate antibiotic treatment was prescribed.
Anti-Bacterial Agents ; APACHE ; Bacteremia ; beta-Lactamases* ; Case-Control Studies ; Humans ; Klebsiella pneumoniae* ; Klebsiella* ; Mortality ; Multivariate Analysis ; Pneumonia ; Retrospective Studies ; Risk Factors* ; Treatment Failure ; Treatment Outcome* ; Urinary Catheterization ; Urinary Catheters

BACKGROUND: Nation-wide outbreak of acute hemorrhagic conjunctivitis occurred in the summer, 2002 in South Korea. We identified the causative agent of this outbreak through virus culture and molecular biological techniques. METHODS: Polymerase chain reaction (PCR) was carried out with direct conjunctival swab samples and cell culture supernatants. Conjunctival swab was done at a community based-eye clinic in Seoul, September 2002. Initial screening for adenovirus and enterovirus was performed. Nested PCR for adenovirus was done with adenovirus common primers using direct swab sample, and reverse transcription PCR (RT-PCR) for enterovirus was done with enterovirus common primers. RT-PCR with primer 188/222 for VP1 region of enterovirus was done, if initial screening test was positive. PCR product was sequenced, and homology searching, compared to prototype strains, was done for serotyping. Protease 3C region of coxsackievirus A24v was amplified and sequenced with primer D1/U2. The sequence of this region was compared to those of viral isolates, which had been obtained from several Asian outbreaks since 1970. RESULTS: Conjunctival swabs were performed in 88 patients. Thirty nine (44%) samples out of the 88 were culture positive on HeLa or MRC-5 cells. Nine (100%) out of 9 culture supernatants, randomly selected from 39 culture positve samples, were positive for coxsackievirus A24v-specific RT-PCR. Phylogenetic analysis showed that sequences from 14 culture positive supernatants, randomly selected from 39 culture positive samples, clustered into a time-related, but distinct lineage, with Asian strains. CONCLUSIONS: We identified the causative agent of the epidemic hemorrhagic conjunctivits in year 2002 as coxsackievirus A24v.
Adenoviridae ; Asian Continental Ancestry Group ; Cell Culture Techniques ; Conjunctivitis, Acute Hemorrhagic* ; Disease Outbreaks ; Enterovirus ; Enterovirus C, Human* ; Humans ; Korea* ; Mass Screening ; Polymerase Chain Reaction ; Reverse Transcription ; Seoul ; Serotyping

BACKGROUND: This study was conducted to evaluate risk factors for infection and treatment outcome of bloodstream infection due to extended spectrum beta-lactamases(ESBL)-producing K. pneumoniae. METHODS: ESBL production was evaluated by NCCLS guidelines and/or double-disk synergy test in K. pneumoniae blood isolates stored from January, 1998 to April, 2002. Sixty patients with bloodstream infection due to ESBL-producing K. pneumoniae (case patients) were compared with 159 matched control patients with bloodstream infection of non-ESBL-producing K. pneumoniae. Retrospective case-control study was performed. RESULTS: There were no significant differences in age, sex, APACHE II score, and the primary site of infection between the case and control groups. In multivariate analysis, significant independent risk factors associated with bloodstream infection due to ESBL-producing K. pneumoniae were urinary catheterization, invasive procedure within previous 72 hours, and the number of antibiotics administered within previous 30 days. In clinical response at 72 hours after initial antibiotic treatment, complete response rate was higher in the controls (13.3% vs. 40.3%, respectively, P<0.001), however, treatment failure rate was higher in the cases (33.3% vs. 11.9%, respectively, P<0.001). Overall 7- day mortality rates in the cases and the controls were was 20% (12/60) and 15.7% (25/159) (P= 0.451), respectively, and overall 30-day mortality rates were 30% (18/60) and 24.5% (39/159), respectively (P=0.410). When the patients with bloodstream infection of ESBL-producing organism were evaluated and the patients who received inadequate definitive antibiotic treatment were excluded, delayed effective antibiotic treatment was found to be not associated with higher mortality. CONCLUSION: In patients infected with ESBL-producing K. pneumoniae bacteremia, clinical response rate at 72 hours after antimicrobial therapy was lower, but the increase of mortality rate was not significant. Delayed effective antibiotic treatment was not associated with higher mortality, when definitive appropriate antibiotic treatment was prescribed.
Anti-Bacterial Agents ; APACHE ; Bacteremia ; beta-Lactamases* ; Case-Control Studies ; Humans ; Klebsiella pneumoniae* ; Klebsiella* ; Mortality ; Multivariate Analysis ; Pneumonia ; Retrospective Studies ; Risk Factors* ; Treatment Failure ; Treatment Outcome* ; Urinary Catheterization ; Urinary Catheters

BACKGROUND: Nation-wide outbreak of acute hemorrhagic conjunctivitis occurred in the summer, 2002 in South Korea. We identified the causative agent of this outbreak through virus culture and molecular biological techniques. METHODS: Polymerase chain reaction (PCR) was carried out with direct conjunctival swab samples and cell culture supernatants. Conjunctival swab was done at a community based-eye clinic in Seoul, September 2002. Initial screening for adenovirus and enterovirus was performed. Nested PCR for adenovirus was done with adenovirus common primers using direct swab sample, and reverse transcription PCR (RT-PCR) for enterovirus was done with enterovirus common primers. RT-PCR with primer 188/222 for VP1 region of enterovirus was done, if initial screening test was positive. PCR product was sequenced, and homology searching, compared to prototype strains, was done for serotyping. Protease 3C region of coxsackievirus A24v was amplified and sequenced with primer D1/U2. The sequence of this region was compared to those of viral isolates, which had been obtained from several Asian outbreaks since 1970. RESULTS: Conjunctival swabs were performed in 88 patients. Thirty nine (44%) samples out of the 88 were culture positive on HeLa or MRC-5 cells. Nine (100%) out of 9 culture supernatants, randomly selected from 39 culture positve samples, were positive for coxsackievirus A24v-specific RT-PCR. Phylogenetic analysis showed that sequences from 14 culture positive supernatants, randomly selected from 39 culture positive samples, clustered into a time-related, but distinct lineage, with Asian strains. CONCLUSIONS: We identified the causative agent of the epidemic hemorrhagic conjunctivits in year 2002 as coxsackievirus A24v.
Adenoviridae ; Asian Continental Ancestry Group ; Cell Culture Techniques ; Conjunctivitis, Acute Hemorrhagic* ; Disease Outbreaks ; Enterovirus ; Enterovirus C, Human* ; Humans ; Korea* ; Mass Screening ; Polymerase Chain Reaction ; Reverse Transcription ; Seoul ; Serotyping

STATEMENT OF PROBLEM: Dental magnetic materials have been applied to removable prosthetic appliances, maxillofacial prostheses, obturator and dental implant but they still have some problems such as low corrosion resistance in oral environments. PURPOSE: To increase the corrosion resistance of dental magnetic materials, surfaces of Sm-Co and Nd-Fe-B based magnetic materials were plated with TiN and sealed with stainless steels. MATERIALS AND METHODS: Surfaces of Sm-Co and Nd-Fe-B based magnetic materials were plated with TiN and sealed with stainless steels, and then three kinds of electrochemical corrosion test were performed in 0.9% NaCl solution; potentiodynamic, potentiostatic, and electrochemical impedance test. From this study, corrosion behavior, amount of elements released, mean average surface roughness values, the changing of retention force, and magnetic force values were measured comparing with control group of non-coated magnetic materials. RESULTS: The values of surface roughness of TiN coated Sm-Co and TiN coated Nd-Fe-B based magnetic materials were lower than those of non coated Sm-Co and Nd-Fe-B alloy. From results of potentiodynamic test, the passive current density of TiN coated Sm-Co alloy were smaller than those of TiN coated Nd-Fe-B alloy and non coated alloys in 0.9% NaCl solution. From results of potentiostatic and electrochemical impedance test, the surface stability of the TiN coated Sm-Co alloy was more drastically increased than that of the TiN coated Nd-Fe-B alloy and non-coated alloy. The retention and magnetic force after and before corrosion test did not change in the case of TiN coated magnetic alloy sealed with stainless steel. CONCLUSION: It is considered that the corrosion problem and improvement for surface stability of dental magnetic materials could be solved by ion plating with TiN on the surface of dental magnetic materials and by sealing with stainless steels.
Alloys ; Corrosion ; Dental Implants ; Dentistry* ; Electric Impedance ; Maxillofacial Prosthesis ; Stainless Steel ; Tin