Surface characteristics of plasma electrolytic oxidized Ti-mesh for dental use / 대한치과재료학회지

In this study, surface characteristics of plasma electrolytic oxidized Ti-mesh for dental use were studied using various experimental instruments. The titanium mesh was used as a substrate for PEO. Using a pulsed DC power supply, PEO treatment was carried out at 280 V for 3 min in the electrolytic solution containing Ca, Mg, and P ions. And the electrolyte used for PEO was prepared by mixing with Ca(CH 3COO)2·H 2O, C 3H 7CaO 6P, and (CH 3COO) 2Mg·4H 2O. The PEO-treated surface was observed by using X-ray diffraction, field-emission scanning electron microscope, energy dispersive X-ray spectroscopy, atomic force microscopy (AFM), and nanoindentation tester.PEO-treated Ti-mesh in solution containing Ca, Mg, and P ions (CaMgP) sample showed the active spark discharge reaction compared to in solution containing Ca and P ions (CaP) sample. In CaP and CaMgP samples, the PEO surface of Ti-mesh showed mainly circular, irregular, and oval shapes of pores. In the case of CaMgP, the defects and precipitates such as MgO were formed on the surface. On the sample surface, the distribution of the desired element was detected homogeneously.The PEO-treated CaP and CaMgP specimens were mainly composed of anatase, Mg, and hydroxyapatite. From the AFM result, the average roughness was 0.247 µm for CaP and 0.226 µm for CaMgP, respectively. The hardness of CaMgP containing Mg ions was increased compared to CaP containing without Mg ions, also, the elastic modulus of CaMgP sample was higher than that of CaP sample.

Surface characteristics of nanotube-formed Ti-Ta-Ag-Pt alloys for dental implants / 대한치과재료학회지

In this study, the surface characteristics of nanotube-formed Ti-Ta-Ag-Pt alloys for dental implants were studied using various experimental instruments. The Ti-xTa-2Ag-2Pt quaternary alloys were manufactured using a vacuum arc-melting furnace with varying Ta contents (10, 30, and 50 wt%) and then homogenized by heat treatment at 1050 ℃ for 1 h. The nanotube formation of Ti-xTa-2Ag-2Pt (x = 10–50 wt%) alloy was performed using a DC power source of 30 V in 1.0 M H3PO4 + 0.8 wt% NaF electrolyte solution. The surface characterization was performed using optical microscopy (OM), field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and wettability and nano-indentation tests. The microstructure of the Ti-xTa alloy was composed of an α''-phase (Widmanstätten structure) and a β-phase equiaxed structure. The XRD peak of the α phase became weaker and that of the β phase became stronger with increasing Ta content. The elastic modulus of Ti-30Ta-2Ag-2Pt alloy was lower than those of the other alloys. The highly ordered nanotubes were formed in the Ti-10Ta-2Ag-2Pt and Ti-30Ta-2Ag-2Pt alloys; nanoparticles were found in the Ti-50Ta-2Ag-2Pt alloy. The diameters of the large and small nanotubes increased and decreased, respectively, with increasing Ta content. Nanotubes did not grow in a needle-like structure (Widmanstätten), and nanotubes are not formed at the grain boundaries and edges. The anatase phase of TiO2 was detected in Ti-30Ta-2Ag-2Pt alloy and disappeared in Ti-50Ta-2Ag-2Pt alloy. The contact angle of the nanotube-formed Ti-30Ta-2Ag-2Pt alloy was lower than those of the other alloys.

Plasma electrolytic oxidized surface of (Mg/Si)-hydroxyapatite coated Ti-29Nb-xHf alloys for dental implant / 대한치과재료학회지

In this study, in order to form a micropore oxide film containing (Mg/Si)-hydroxyapatite on the surface of a Ti-29Nb-xHf alloy, pores were formed on the surface of the alloy by plasma electrolytic oxidation (PEO) and the morphology of the surface was studied. For this, Ti-29Nb, Ti-29Nb-3Hf, Ti-29Nb-7Hf, and Ti-29Nb-15Hf alloys were prepared by arc melting. Micropores were formed on the surface in an electrolyte solution containing Mg and Si ions using PEO. Surface characteristics and mechanical properties of all specimens were investigated using OM, FE-SEM, XRD, EDS, Vickers hardness and nanoindenter. Bone formation was performed in SBF solution, and the following results were obtained. Ti-29Nb, Ti-29Nb-3Hf, and Ti-29Nb-7Hf showed mainly needle-like martensitic structures, and Ti-29Nb-15Hf alloys showed mainly equiaxed structures. From the result of the mechanical property analysis, the elastic modulus and hardness of the Ti-29Nb alloy decreased, as the Hf content increased.Under the condition of same applied voltage, as the content of Mg ions increased, the diameter of the micropores became smaller and uniform pores were formed. The Ca/P and (Ca+Mg)/(Si+P) ratios decreased, as the Mg content increased, and at 5% Mg, the ratio was similar to that of natural bone. Bone growth was nucleated around the pore.

Surface characteristics of nanotube-formed Ti-Ta-Ag-Pt alloys for dental implants / 대한치과재료학회지

In this study, the surface characteristics of nanotube-formed Ti-Ta-Ag-Pt alloys for dental implants were studied using various experimental instruments. The Ti-xTa-2Ag-2Pt quaternary alloys were manufactured using a vacuum arc-melting furnace with varying Ta contents (10, 30, and 50 wt%) and then homogenized by heat treatment at 1050 ℃ for 1 h. The nanotube formation of Ti-xTa-2Ag-2Pt (x = 10–50 wt%) alloy was performed using a DC power source of 30 V in 1.0 M H3PO4 + 0.8 wt% NaF electrolyte solution. The surface characterization was performed using optical microscopy (OM), field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and wettability and nano-indentation tests. The microstructure of the Ti-xTa alloy was composed of an α''-phase (Widmanstätten structure) and a β-phase equiaxed structure. The XRD peak of the α phase became weaker and that of the β phase became stronger with increasing Ta content. The elastic modulus of Ti-30Ta-2Ag-2Pt alloy was lower than those of the other alloys. The highly ordered nanotubes were formed in the Ti-10Ta-2Ag-2Pt and Ti-30Ta-2Ag-2Pt alloys; nanoparticles were found in the Ti-50Ta-2Ag-2Pt alloy. The diameters of the large and small nanotubes increased and decreased, respectively, with increasing Ta content. Nanotubes did not grow in a needle-like structure (Widmanstätten), and nanotubes are not formed at the grain boundaries and edges. The anatase phase of TiO2 was detected in Ti-30Ta-2Ag-2Pt alloy and disappeared in Ti-50Ta-2Ag-2Pt alloy. The contact angle of the nanotube-formed Ti-30Ta-2Ag-2Pt alloy was lower than those of the other alloys.

Corrosion Behaviors of Dental Implant Alloy after Micro-sized Surface Modification in Electrolytes Containing Mn Ion

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.

Electrochemical Characteristics of Nanotubular Ti-25Nb-xZr Ternary Alloys for Dental Implant Materials

PURPOSE: The purpose of this study was to investigate the electrochemical characteristics of nanotubular Ti-25Nb-xZr ternary alloys for dental implant materials. MATERIALS AND METHODS: Ti-25Nb-xZr alloys with different Zr contents (0, 3, 7, and 15 wt.%) were manufactured using commercially pure titanium (CP-Ti), niobium (Nb), and zirconium (Zr) (99.95 wt.% purity). The alloys were prepared by arc melting in argon (Ar) atmosphere. The Ti-25Nb-xZr alloys were homogenized in Ar atmosphere at 1,000℃ for 12 hours followed by quenching into ice water. The microstructure of the Ti-25Nb-xZr alloys was examined by a field emission scanning electron microscope. The phases in the alloys were identified by an X-ray diffractometer. The chemical composition of the nanotube-formed surfaces was determined by energy-dispersive X-ray spectroscopy. Selforganized TiO₂ was prepared by electrochemical oxidation of the samples in a 1.0 M H₃PO₄+0.8 wt.% NaF electrolyte. The anodization potential was 30 V and time was 1 hour by DC supplier. Surface wettability was evaluated for both the metallographically polished and nanotube-formed surfaces using a contact-angle goniometer. The corrosion properties of the specimens were investigated using a 0.9 wt.% aqueous solution of NaCl at 36℃±5℃ using a potentiodynamic polarization test. RESULT: Needle-like structure of Ti-25Nb-xZr alloys was transform to equiaxed structure as Zr content increased. Nanotube formed on Ti-25Nb-xZr alloys show two sizes of nanotube structure. The diameters of the large tubes decreased and small tubes increased as Zr content increased. The lower contact angles for nanotube formed Ti-25NbxZr alloys surfaces showed compare to non-nanotube formed surface. The corrosion resistance of alloy increased as Zr content increased, and nanotube formed surface showed longer the passive regions compared to non-treatment surface. CONCLUSION: It is confirmed that corrosion resistance of alloy increased as Zr content increased, and nanotube formed surface has longer passive region compared to without treatment surface.

Effect of different grinding burs on the physical properties of zirconia

PURPOSE: Grinding with less stress on 3Y-TZP through proper selection of methods and instruments can lead to a long-term success of prosthesis. The purpose of this study was to compare the phase transformation and physical properties after zirconia surface grinding with 3 different grinding burs. MATERIALS AND METHODS: Forty disc-shaped zirconia specimens were fabricated. Each Ten specimens were ground with AllCeramic SuperMax (NTI, Kahla, Germany), Dura-Green DIA (Shofu Inc., Kyoto, Japan), and Dura-Green (Shofu Inc., Kyoto, Japan). Ten specimens were not ground and used as a control group. After the specimen grinding, XRD analysis, surface roughness test, FE-SEM imaging, and biaxial flexural strength test were performed. RESULTS: After surface grinding, small amount of monoclinic phase in all experimental groups was observed. The phase change was higher in specimens, which were ground with Dura-Green DIA and AllCeramic SuperMax burs. The roughness of surfaces increased in specimens, which were ground with Dura-Green DIA and AllCeramic SuperMax burs than control groups and ground with Dura-Green. All experimental groups showed lower flexural strength than control group, but there was no statistically significant difference between control group and ground with Dura-Green DIA and AllCeramic SuperMax burs. The specimens, which were ground with Dura- Green showed the lowest strength. CONCLUSION: The use of dedicated zirconia-specific grinding burs such as Dura-Green DIA and AllCeramic SuperMax burs decreases the grinding time and did not significantly affect the flexural strength of zirconia, and therefore, they may be recommended. However, a fine polishing process should be accompanied to reduce the surface roughness after grinding.

Effect of various intraoral repair systems on the shear bond strength of composite resin to zirconia

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.

Comparison of fatigue fracture strength by fixture diameter of mini implants / 대한치과보철학회지

PURPOSE: This study was conducted to obtain difference in fracture strength according to the diameter of one-body O-ring-type of mini implant fixture, to determine the resistance of mini implant to masticatory pressure, and to examine whether overdenture using O-ring type mini implant is clinically usable to maxillary and mandibular edentulous patients. MATERIALS AND METHODS: For this study, 13 mm long one body O-ring-type mini implants of different diameters (2.0 mm, 2.5 mm and 3.0 mm) (Dentis, Daegu, Korea) were prepared, 5 for each diameter. The sample was placed at 30degrees from the horizontal surface on the universal testing machine, and off-axis loading was applied until permanent deformation occurred and the load was taken as maximum compressive strength. The mean value of the 5 samples was calculated, and the compressive strength of implant fixture was compared according to diameter. In addition, we prepared 3 samples for each diameter, and applied loading equal to 80%, 60% and 40% of the compressive strength until fracture occurred. Then, we measured the cycle number on fracture and analyzed fatigue fracture for each diameter. Additionally, we measured the cycle number on fracture that occurred when a load of 43 N, which is the average masticatory force of complete denture, was applied. The difference on compressive strength between each group was tested statistically using one-way ANOVA test. RESULTS: Compressive strength according to the diameter of mini implant was 101.5 +/- 14.6 N, 149 +/- 6.1 N and 276.0 +/- 13.4 N, respectively, for diameters 2.0 mm, 2.5 mm and 3.0 mm. In the results of fatigue fracture test at 43 N, fracture did not occur until 2x106 cycles at diameter 2.0 mm, and until 5x106 cycles at 2.5 mm and 3.0 mm. CONCLUSION: Compressive strength increased significantly with increasing diameter of mini implant. In the results of fatigue fracture test conducted under the average masticatory force of complete denture, fracture did not occur at any of the three diameters. All of the three diameters are usable for supporting overdenture in maxillary and mandibular edentulous patients, but considering that the highest masticatory force of complete denture is 157 N, caution should be used in case diameter 2.0 mm or 2.5 mm is used.

Effect of TiN coating of abutment screw on detorque force / 대한치과보철학회지

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.

Improvement effects of electrochemical stability of magnetic materials for prosthetic dentistry / 대한치과보철학회지

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.

Effects of surface coating on the screw release of dental implant screw / 대한치과보철학회지

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.

Corrosion Phenomena Of Magnetic Attachment Used In Oral Environment / 대한치과보철학회지

The purpose of this study was to investigate further the mechanics of failure of magnets used for denture retention. Dyna magnets were retrived from denture that had failed after 34 months of clinical use. The magnets were observed and sectioned in order to analyse with high resolution scanning electron microscope. From this study, corrosion behaviors of used magnetic attachment were analysed. The results were as follows: 1. In Nd-Fe-B based magnetic materials, the erosion-corrosion was started at ununiformed part of stainless steel cover. 2. Corrosion was initiated at weared stainless steel surface and then magnetic materials were spalled by corrosive solution. 3. Spalling was occurred in Nd-Fe-B magnet materials due to corrosion products and then corrosion rate was increased drastically. 4. Corrosion started from ununiformed stainless steel surface as well as welded zone. In conclusion, the failure of magnets may occur by either breakdown of the welding or breakdown of the encapsulating material. So, it is considered that the corrosion problem of dental magnetic materials could be solved to some extent with surface treatment of dental magnetic materials.