Metal-ceramic interface characteristics of Co-Cr alloy fabricated by selective laser melting / 中国组织工程研究

BACKGROUND: Co-Cr ceramic alloys made by selective laser melting technology are widely used in the field of dental restoration, but the influence of selective laser melting technology on the bonding properties of Co-Cr ceramic alloys is still controversial. OBJECTIVE: To explore the metal-ceramic interface characteristics of dental Co-Cr alloy fabricated by selective laser melting. METHODS: Metal-ceramic specimens were prepared by selective laser melting and precision casting, respectively. Metal-ceramic bond strengths, interface characteristics, fracture analysis, microstructures and composition distribution of specimens were obtained with the aid of universal testing machine, metallographic microscope, scanning electron microscope coupled with energy disperse spectrometer. RESULTS AND CONCLUSION: (1) The metal-ceramic bond strengths of precision casting Co-Cr alloy was higher than that of selective laser melting Co-Cr alloy (P < 0.05). (2) Metallographic microscope showed that selective laser melting Co-Cr alloy had fine grains and a more uniform matrix. Precision casting Co-Cr alloy showed typical casting dendritic structure with coarse grains and a large number of island second phase structures. (3) Scanning electron microscopy showed that precision casting Co-Cr alloy had a thicker diffusion layer than the selective laser melting Co-Cr alloy at the metal-ceramic interface. (4) Scanning electron microscopy showed that the metal-ceramic specimens of precision casting Co-Cr alloy tended to cohesive fracture, and the metal-ceramic specimens of selective laser melting Co-Cr alloy tended to adhesive fracture. (5) The results showed that although the bonding strength of selective laser melting Co-Cr alloy was lower than that of precision casting Co-Cr alloy, the bonding strength of selective laser melting Co-Cr alloy could still meet the requirements of standard YY0621.1-2016.

Evaluation of the Effect of Different Surface Treatments on Bond Strength of Heat Cured Acrylic Resin at Co-Cr Alloy and PEEK Polymer Interface

Problem statement: A significant clinical concern in Co-Cr alloy removable prosthodontics is a failure of bonding with acrylic resins and PEEK is introduced on various materials to overcome this problem. The reason for this study was to examine the denture base acrylic resin bond strength to Co-Cr alloy and PEEK polymer using different surface treatment. Materials and method: Total 60 number of disc-shaped specimens were prepared and divided into 2 main groups according to the type of framework material, 30 specimens for Co-Cr alloy and 30 specimens for PEEK polymer, which were then subdivided into 3 groups each one consist of 10 specimens, according to the type of surface treatments. Each group either had a no surface treatment (control group) or air abrasive group (110 μm of alumina oxide) or acid etch (98% sulfuric acid) group. The specimens were thermocycled (3000 cycles) after applications of heat cured acrylic resin. Results: The results for Co-Cr alloy showed that the air abrasive surface treatments had the highest bond strength mean value followed by the control group (no surface treatment), while the acid surface treatment had the least mean value of bond strength. For PEEK polymer, the results revealed that the acid surface treatment had the highest value of bond strength followed by the air abrasive surface treatment while the control group (no surface treatment) had the least bond strength mean value. Conclusion: Air abrasive surface treatment significantly improved bond strength for both Co-Cr and PEEK, while sulfuric acid treatment show counterproductive result with Co-Cr alloy whereas with PEEK play an important role in bonding mechanism. The use of PEEK framework in combination with heat cured acrylic resin can be recommended as a promising non-metallic alternatives framework material for removable of partial dentures.

Clinical effects of full crown prosthesis on anterior teeth / 中华医学美学美容杂志

Objective To evaluate the clinical effects of anterior teeth repair of three different restorations made of Co-Cr alloy,Ag-Pd alloy and all-ceramic crowns.Methods 90 cases who needed the both maxillary and mandibular anterior teeth restarations were selected and treated respectively with Co-Cr alloy porcelain fused to metal crowns (PFM)(60 teeth),Ag-Pd alloy PFM (46 teeth)and IPS e.max Press Porcelain full crown (38 teeth).Gingival index was observed before restoration and in 6 and 12 months after restoration.Meanwhile,clinical indicators of two restorations were evaluated as cervical margin's coloration,margin fitness degree,color of restorations,fracture of restorations and contour of restorations,etc.Results The healthy condition of gingiva in groups of Ag-Pd alloy PFM and IPS e.max Press Porcelain full crown were superior to the group of Co-Cr alloy PFM (P＜0.05).There was no cervical margin's coloration in groug of all-ceramic PFM.The color and contour of this group was superior to the group of Co-Cr alloy PFM (P ＜0.05).The significant difference between group of Co Cr alloy and group of Ag-Pd alloy was cervical margin's coloration and marginal density of the restoration (P＜0.05).Conclusions The clinical effects of both groups of Ag-Pd alloy PFM and IPS e.max Press Porcelain full crown is superior to the group of Co-Cr alloy PFM.The IPS e.max Press Porcelain full crown group works best.

Comparison of the bond strength of ceramics to Co-Cr alloys made by casting and selective laser melting

PURPOSE: Considering the importance of metal-ceramic bond, the present study aimed to compare the bond strength of ceramics to cobalt-chrome (Co-Cr) alloys made by casting and selective laser melting (SLM). MATERIALS AND METHODS: In this in-vitro experimental study, two sample groups were prepared, with one group comprising of 10 Co-Cr metal frameworks fabricated by SLM method and the other of 10 Co-Cr metal frameworks fabricated by lost wax cast method with the dimensions of 0.5 × 3 × 25 mm (following ISO standard 9693). Porcelain with the thickness of 1.1 mm was applied on a 3 × 8-mm central rectangular area of each sample. Afterwards, bond strengths of the samples were assessed with a Universal Testing Machine. Statistical analysis was performed with Kolmogorov-Smirnov test and T-test. RESULTS: Bond strength in the conventionally cast group equaled 74.94 ± 16.06 MPa, while in SLM group, it equaled 69.02 ± 5.77 MPa. The difference was not statistically significant (P ≤ .05). CONCLUSION: The results indicated that the bond strengths between ceramic and Co-Cr alloys made by casting and SLM methods were not statistically different.

The effect of Zirconium Nitride coating on shear bond strength with denture base resin in Co-Cr alloy and titanium alloy

PURPOSE: The purpose of this study was to evaluate of Zirconium Nitride (ZrN) coating on shear bond strength with denture base resin in Co-Cr and Ti-6Al-4V alloy. MATERIALS AND METHODS: Co-Cr and Ti-6Al-4V alloy disks (10 mm in diameter, 2.5 mm in thickness; each other: n = 14) were prepared and divided with 2 groups each other by ZrN coating. After primer was applied to disks surface, denture base resin with diameter 6 mm, height 5 mm was bonded on metal disk surface. After surface roughness was measured by Profiler, shear bond strength was determined with Universal testing machine and analyzed with two-way ANOVA. The specimen surfaces and failure mode were examined using a scanning electron microscope. RESULTS: ZrN coated groups showed significantly higher rough surface than non-coated groups (P < 0.05). Irrespective of alloy materials, shear bond strength of ZrN coated groups were lower than non-coated groups (P < 0.001). The scanning electron microscope (SEM) of ZrN coated groups showed mixed and adhesive fractures. CONCLUSION: ZrN coating weakened bonding strength between denture base resin and Co-Cr, Ti-6Al-4V alloy.

In vitro study on the surface properties of cobalt chromium alloy fabricated by two different methods / 实用口腔医学杂志

Objective:To evaluate the surface free energy and Streptococcus mutans(S.mutans)adhesion on the surfaces of Co-Cr al-loy specimens fabricated by selective laser sintering(SLS)and casting method(SG and W280)respectively.Methods:The specimens of three groups were polished by SiC sandpaper.Surface morphology test,surface contact angle test and surface adhesion test of S.mu-tans were performed.Results:With the same surface roughness value,the surface contact angle of group SLS,W280 and SG was 66.200 ±3.112,74.212 ±3.206 and 67.238 ±2.047(P >0.05),the surface adhesion of S.mutans colone was 8.88 ±2.90,9.25 ± 2.05 and 8.50 ±1.85(P >0.05),respectively.Conclusion:The cobalt chromium alloy fabricated by SLS and casting method have similar surface performance.

The study of cytocompatibility of Co-Cr alloy and Ti alloy / 天津医药

Objective To investigate the cytocompatibility of the liching liquids of Co-Cr alloy and Ti alloy on human gingival fibroblasts (HGF). Methods The HGF were treated in vitro with leaching liquids of Co-Cr alloy and Ti alloy, respectively. The DMEM cell medium containing 10% fetal bovine serum was served as a negative control. The viability of HGF treated by two dental alloys were evaluated by means of MTT, and the contents of intracellular reduced glutathione (rGSH) were assayed by kits. The tumor necrosis factor-α(TNF-α) contents were determined in the culture supernatant by ELISA in two groups. The effects of these alloys on the expression of caspase-3 were examined by real time-PCR method. Results Compared with the control group, HGF treated with Co-Cr alloy leaching liquids showed a lower viability ( P ＜0.05), while Ti alloy leaching liquid promoted the proliferation of HGF. In Co-Cr alloy group, the rGSH content was significantly decreased (P＜0.05), while TNF-α content was significantly increased (P＜0.05) compared with control group. There were no significant differences in rGSH and TNF-α contents between the Ti alloy group and control group (P＞0.05). The expression of caspase-3 was significantly higher in Co-Cr alloy group than that of control group (P＜0.05), while there was no significant difference in the expression of caspase-3 between Ti alloy group and control group. Conclusion Results suggest that Co-Cr alloy possesses cytotoxicity, while there is better cell compatibility for Ti alloy.

Effect of chloride ion on corrosion of two commonly used dental alloys / 中南大学学报(医学版)

Objective: To investigate the effect of chloride concentration on the corrosion of Co-Cr alloy and pure Ti in a simulated oral environment. Methods: The electrochemical corrosion tests of pure Ti and Co-Cr alloy were carried out in neutral artiifcial saliva solutions with different NaCl concentrations (0.9%, 2.0%, and 3.0%). hTe morphologies of corroded surface for pure Ti and Co-Cr alloy were observed by scanning electron microscope (SEM). Results: hTe changes in the self-corrosion potentials (Ecorr) for pure Ti and Co-Cr alloy in three kinds of artificial saliva solutions was not obvious. However, the self-corrosion current densities (Icorr) of pure Ti were much lower than those of Co-Cr. TheIcorr of Co-Cr alloy increased in a concentration-dependent manner of NaCl, whereas the breakdown potential (Eb) of Co-Cr alloy decreased in a concentration-dependent manner. hTe potential ranged for the breakdown of oxide film (Ev) was shortened in a concentration-dependent manner of NaCl. There was no obviousdifference in theIcorr of pure Ti with different concentrations of NaCl. hTe breakdown potential was not seen according to the polarization curves. Conclusion: In a certain range, the increase of the concentration of Cl- leads to accelerate the corrosion behavior of Co-Cr alloy, but it does not affect pure Ti.

Evaluation of shear bond strength of repair acrylic resin to Co-Cr alloy

PURPOSE: The purpose of this study was to investigate the impact of different surface treatment methods and thermal ageing on the bond strength of autopolymerizing acrylic resin to Co-Cr. MATERIALS AND METHODS: Co-Cr alloy specimens were divided into five groups according to the surface conditioning methods. C: No treatment; SP: flamed with the Silano-Pen device; K: airborne particle abrasion with Al2O3; Co: airborne particle abrasion with silica-coated Al2O3; KSP: flamed with the Silano-Pen device after the group K experimental protocol. Then, autopolymerized acrylic resin was applied to the treated specimen surfaces. All the groups were divided into two subgroups with the thermal cycle and water storage to determine the durability of the bond. The bond strength test was applied in an universal test machine and treated Co-Cr alloys were analyzed by scanning electron microscope (SEM). Two-way analysis of variance (ANOVA) was used to determine the significant differences among surface treatments and thermocycling. Their interactons were followed by a multiple comparison' test performed uing a post hoc Tukey HSD test (alpha=0.05). RESULTS: Surface treatments significantly increased repair strengths of repair resin to Co-Cr alloy. The repair strengths of Group K, and Co significantly decreased after 6,000 cycles (P<.001). CONCLUSION: Thermocycling lead to a significant decrease in shear bond strength for air abrasion with silica-coated aluminum oxide particles. On the contrary, flaming with Silano-Pen did not cause a significant reduction in adhesion after thermocycling.

Effects of TiN coating on corrosion resistance of dental Co-Cr alloy / 上海第二医科大学学报

Objective To investigate the effects of titanium nitride(TiN) coating on corrosion resistance of dental Co-Cr alloy in the simulated oral environment. Methods The Co-Cr alloy commonly used was casted with specimen sized of 10 mm× 10 mm×3 mm. Then the specimen was coated with a thickness of 2.5 μm TiN coating on the surface by multi-arc physical vapor deposition. The Tafel polarization curves of the specimen before and after coating titanium nitride in artificial saliva were measured by electrochemical station. Results From the Tafel polarization curves, the specimen after coating TiN showed that both anodic polarization curve and cathodal polarization curve were fiat, natural corrosion potential moved to the positive way, and passivation interval got longer. From the annular anodic polarization curves, the specimen after coating TiN had almost no "delay area". Conclusion TiN coating can improve corrosion resistance of Co-Cr alloy.

Shear bond strength of heat-cured denture base resin to surface treated Co-Cr alloy with different methods / 대한치과보철학회지

STATEMENT OF PROBLEM: For the long-term success of removable partial dentures, the bonding between metal framework and denture base resin is one of the important factors. To improve bonding between those, macro-mechanical retentive form that is included metal framework design has been generally used. However it has been known that sealing at the interface between metal framework and denture base resin is very weak, because this method uses mechanical bonding. PURPOSE: Many studies has been made to find a simple method which induces chemical bond, now various bonding system is applied to clinic. In this experiment, shear bond strengths of heat-cured denture base resin to the surface-treated Co-Cr alloy were measured before and after thermocycling. Chemically treated groups with Alloy Primer(TM), Super-Bond C&B(TM), and tribochemically treated group with Rocatec(TM) system were compared to the beadtreated control group. The data were analyzed with two-way ANOVA. RESULT: 1. Shear bond strength of bead-treated group is highest, and Alloy Primer(TM) treated group, Super-Bond C&B(TM) treated group, Rocatec(TM) system treated group were followed. Statistically significant differences were found in each treated group(p0.05). 3. Shear bond strengths of bead-treated group and Alloy Primer(TM) treated group showed no statistically significant difference before and after thermocycling(p>0.05), and those of Super-Bond CBTM treated group and RocatecTM system treated group showed statistically significant difference after thermocycling(p<0.05).

Comparative study of shear bond strength between cp-Ti / Co-Cr alloy and composite resins / 대한치과보철학회지

STATEMENT OF PROBLEM: Composite resin-veneered metal restorations can be used as an alternative to porcelain-fused-metal restorations. But, because of the relatively low bond strength of veneering composite to metal framework, various surface treatment methods have been introduced to improve the bond strength. PURPOSE: The object of this study was to compare the shear bond strength of different combinations of each of the two bonding systems and each of the two composite veneering resins to cp-Ti / Co-Cr alloy. MATERIAL AND METHODS: Two resin bonding systems (metal conditioner containing MEPS monomer, tribochemical silicoating system) and two composite resins (Gradia, Sinfony) were tested on cp-Ti and Co-Cr alloy. Then, according to manufacturers' instructions, resin bonding systems and composite resins were applied. All test specimens were divided into four groups for each alloy; I) sandblast + Metal Primer II+ Gradia (MG), II) sandblast + Metal Primer II + Sinfony (MS), III) Rocatec + Gradia (RG), IV) Rocatec + Sinfony (RS). The shear bond strength was determined using a universal testing machine and all data were statistically analyzed with Mann-Whitney test and Kruskal-Wallis test at the significance level of 0.05. RESULTS: The mean (standard deviations) of shear bond strength according to the combinations of two bonding systems and two composite resins to cp-Ti arranged from 16.44 MPa to 17.07 MPa and the shear bond strength to Co-Cr alloy ranged from 16.26 MPa to 17.70 MPa. The result shows that the difference were not statistically significant. CONCLUSION: The shear bond strengths of composite resins to both cast cp-Ti and Co-Cr alloy were not significantly different between the metal conditioner and the tribochemical silicoating system. And no differences in bond strength were found between cp-Ti and Co-Cr alloy.

Improvement of Lubrication Properties for New Surface Structure with Regular Patterning for the Frictional Surfaces of the Artificial Joints: Evaluation of Lubrication Properties by the Pendulum Type Hip Joint Simulator / 대한정형외과학회잡지

PURPOSE: A new surface structure with a regular patterning of the frictional surfaces of the artificial joints were designed to improve the wear problems. MATERIALS AND METHODS: The lubrication properties for the cup (ultra high molecular weight polyethylene, UHMWPE) vs. ball (Co-Cr alloy) were examined to evaluate the coefficient of friction, wear and surface roughness. The surface structure is a dent pattern, which has diameter of 0.3-0.8 mm, a pitch of 1.2 mm. In this study, such surface patterns were applied to artificial hip joints, and the effects of regular patterning on the frictional surface were examined using a pendulum type hip joint simulator. RESULTS: The coefficient of friction between the cup and a patterned ball showed the same value between the cup and the non-patterned ball. However, the amount of wear of the cup, which was in contact with the patterned head, was only 45% that of the cup, which was in contact with the non-patterned head, and the surface roughness of the cup with the non-patterned head was three times greater than that of the cup with a patterned head. CONCLUSION: These results demonstrate that the lubrication properties can be improved by patterning the frictional surface of the artificial joint. Consequently, patterning on the frictional surfaces can exted the life of an artificial joint.