Evaluation of effect of galvanic corrosion between nickel-chromium metal and titanium on ion release and cell toxicity

Preparation of capsaicin-loaded ultrafine fiber film and its application in the treatment of oral ulcers in rats

A drug-loaded diaphragm is an easy-to-use and effective drug delivery system that is often used to treat mouth ulcers. In this study, an ultrafine fiber film loaded with capsaicin was successfully prepared using the electrospinning technology. poly-L-lactic acid and gelatin were selected as the matrix materials to form the composite fiber, and trifluoroethanol was used as a co-solvent for poly-L-lactic acid, gelatin and capsaicin to prepare the spinning solution, which was simple to fabricate. The prepared fiber films were characterized based on their microscopic morphology and tested to derive their mechanical properties. Thereafter, the capsaicin release behavior of the film was investigated. In vitro experiments revealed certain anti-inflammatory and antibacterial abilities while animal experiments revealed that the capsaicin-loaded ultrafine fiber film could promote the healing of oral ulcers in rats. Healing of the tongue tissue in rats administered 10% capsaicin-loaded fiber film was found to be better than that in rats administered the commercial dexamethasone patch. Overall, this development strategy may prove to be promising for the development of oral ulcer patch formulations.

Quality of the Ceramic and Ni-Cr Alloy Joint after Al2O3 Abrasive Blasting

The purpose of this in vitro study was to determine the effect of airborne-particle abrasion process parameters on the strength of the Ni-Cr alloy-ceramic bond. One hundred and forty-four Ni-Cr disks were airborne-particle abraded with 50, 110 and 250 µm Al₂O₃ at a pressure of 400 and 600 kPa. After treatment, the specimens were bonded to dental ceramics by firing. The strength of the metal-ceramic bond was determined using the shear strength test. The results were analyzed with three-way analysis of variance (ANOVA) and the Tukey honest significant difference (HSD) test (α = 0.05). The examination also considered the thermal loads (5000 cycles, 5-55 °C) to which the metal-ceramic joint is subjected during exploitation. There is a close correlation between the strength of the Ni-Cr alloy-dental ceramic joint and the alloy roughness parameters after abrasive blasting: Rpk (reduced peak height), Rsm (the mean spacing of irregularities), Rsk (skewness of the profile) and RPc (peak density). The highest strength of the Ni-Cr alloy surface bonding with dental ceramics under operating conditions is provided by abrasive blasting under 600 kPa pressure with 110 µm Al₂O₃ particles (p < 0.05). Both the abrasive blasting pressure and the particle size of the Al₂O₃ abrasive significantly affect the joint's strength (p < 0.05). The most optimal blasting parameters are 600 kPa pressure with 110 µm Al₂O₃ particles (p < 0.05). They allow the highest bond strength between the Ni-Cr alloy and dental ceramics to be achieved.

Electrogalvanism in Oral Implantology: A Systematic Review

Purpose

The objective of this work is to study galvanic corrosion of different couples of prosthetic and implant alloys through the realization of a systematic review.

Materials and Methods

An electronic search was performed on Pubmed, Google Scholar, Scopus, ScienceDirect, EbscoHost, and Web of Science for published studies related to electrogalvanism in oral implantology. The keywords used were “dental implants” and “galvanic corrosion.” Two independent readers read the scientific articles.

Results

From 65 articles initially identified, only 19 articles met the eligibility criteria. The evaluation of the selected articles allowed us to determine the parameters compared, such as the resistance to galvanic corrosion, the influence of fluorine and pH on the electrochemical behavior, and the release of metal ions and their cytotoxicity. Indeed, Ti6Al4V and precious alloys coupled to titanium were found to be the most resistant to galvanic corrosion, followed by cobalt-chromium alloys and nickel-chromium alloys which were least resistant. This resistance decreases with increasing fluorine concentration and with decreasing pH of the environment. Discussion. The implant-prosthetic system's galvanic resistance is influenced by many intrinsic factors: alloy composition and surface condition, as well as extrinsic factors such as pH variations and amount of fluorine. The effects of oral electrogalvanism are essentially the result of two main criteria: effects due to electric currents generated by corrosion and effects due to the release of metal ions by corrosion.

Conclusion

To avoid this phenomenon, it is wise to follow the proposed recommendations such as the use of the minimum of distinct metals as much as possible, favoring the commercially pure titanium implant of Ti6Al4V, opting for the choice of couples, titanium/titanium, favoring daily mouthwashes of 227 ppm of fluoride, and avoiding fluorinated acid solutions.

Corrosive Studies of a Prosthetic Ni-Cr Alloy Coated with Ti(C,N) Type Layers

Background: Investigating the general corrosion resistance of Ti(C,N) type coatings on a prosthetic nickel alloy in the aspect of their use as protective coatings on prosthetic and orthodontic elements. Methods: Five groups of Ni-Cr alloy samples covered with Ti(C,N) type coatings differing in their carbon and nitrogen contents were used for the tests. The reference group included alloy samples without coatings. The samples were held for 105 days (2520 h) in salt spray chambers and examined by means of the NSS (neutral salt spray) and SWAAT (sea water acetic acid test) tests. After the periods of 14, 28, 81 and 105 days, the samples were removed and weighed, and their weight losses were determined. Results: In the case of each type of Ti(C,N) coating, the mass loss was lower than the mass loss of a sample without a coating, which makes it possible to state that coatings improve the corrosion resistance. No significant differences in the resistance were observed between the particular coatings. The corrosion rate of the examined coatings is close to parabolic. Conclusions: Ti(C,N) type coatings improve the resistance of a prosthetic Ni-Cr alloy and can be used as protective coatings for prosthetic and orthodontic elements.

Comparing Castability of Nickel-Chromium, Cobalt-Chromium, and Non-Precious Gold Color Alloys, Using two Different Casting Techniques

STATEMENT OF THE PROBLEM

The castability of nonprecious gold color alloy using torch/ centrifugal and induction/vacuum-pressure casting techniques has not been studied yet.

PURPOSE

This study was conducted to compare the castability of nickel chromium, cobalt-chromium and nonprecious gold color alloy using torch/centrifugal and induction/ vacuum-pressure casting techniques.

MATERIALS AND METHOD

In this in vitro study, a total number of 54 identical acrylic wax meshes were prepared and divided into 6 different groups of 9 each. Group 1: nickel-chromium alloy, which was casted with induction technique. Group 2: nickel-chromium alloy was casted with centrifugal technique. Group 3: cobalt-chromium alloy was casted with induction technique. Group 4: cobalt-chromium alloy was casted with centrifugal technique. Group 5: nonprecious gold color alloy was casted with induction technique. Group 6: nonprecious gold color alloy was casted with centrifugal technique. Then castability of specimens was measured using modified Whitlock's method. The results were analyzed using two way ANOVA and post hoc tests.

RESULTS

ANOVA test revealed no statistically significant difference between different alloys with a p Value of 0.313. Moreover, it represented no significant differences within the groups regarding alloy types and casting techniques with a p Value of 0.511 and 0.682, respectively.

CONCLUSION

No significant difference was found in the castability value of nickel-chromium, cobalt-chromium, and nonprecious gold color alloys. In addition, the castability value of three alloys tested in this study was not different by using torch/centrifugal or induction/vacuum-pressure casting machines.

Fatigue Resistance of Cast-on Implant Abutment Fabricated with Three Different Alloys

OBJECTIVES

 This study aimed to evaluate fatigue resistance of cast-on implant abutment using three alloys.

MATERIALS AND METHODS

 Forty specimens of implant-supported crowns were prepared; Group 1 (TA) stock titanium abutments, Group 2 (GS) abutment cast with 40% gold alloy, Group 3 (GP) abutment cast with palladium alloy, and Group 4 (CN) abutment cast with nickel-chromium alloy. Specimens were cyclic loaded at 20 Hz, starting from 200 N (5,000 cycles), followed by stepwise loading of 400, 600, 800, 1,000, 1,200, 1,400, 1,600, and 1,800 N (30,000 cycles/step). Specimens were loaded until failure or reached 245,000 cycles.

STATISTICAL ANALYSIS

 The withstand cycles were analyzed using one-way analysis of variance and Weibull survival analysis. Fracture surfaces were examined using scanning electron microscopy.

RESULTS

 The results of withstand cycles were TA (189,883 ± 22,734), GS (195,028 ± 22,371), GP (187,662 ± 22,555), and CN (200,350 ± 30,851). The statistical analysis showed no significant difference between the groups (p = 0.673).

CONCLUSION

 Although CN has higher Weibull characteristic strength which means greater durability, its lower Weibull modulus demonstrated less structural reliability. Consistent failures at implant fixture level were also found in CN group.

Effect of SiC Abrasive Blasting Parameters on the Quality of the Ceramic and Ni-Cr Dental Alloy Joint

The SiC abrasive blasting parameters are vital in ensuring a suitable bond between dental ceramics and the Ni-Cr alloy. The purpose of this in vitro test was to examine the strength of the joint between the Ni-Cr alloy and fused dental ceramics for SiC abrasive blasting at a specific pressure (400, 600 kPa) and particle size (50, 110, 250 µm) in order to determine the optimal treatment parameters. The test also accounted for thermal loads (5000 cycles, 5–55 °C) to which the metal-ceramic joint is subjected during use. One hundred and forty-four Ni-Cr cylinders were divided into six groups (n = 12) and subjected to the airborne-particle abrasion with SiC with various pressure and grit size parameters. After treatment, the specimens were rinsed, dried, fused to dental ceramics, and examined for their shear strength using the Zwick/Roell Z020 machine. The results were statistically analysed using the ANOVA analysis of variance (α = 0.05). The highest metal-ceramic joint strength was obtained for abrasive blasting with 110 and 250 µm SiC grit at a pressure of 400 kPa. This relationship was also observed after the joint was subjected to thermal loads (5000 thermocycles). Additionally, thermal loads did not significantly reduce the joint’s strength compared with non-loaded joints. For small SiC abrasive grit sizes (50 µm) under pressure 400 kPa, the treatment pressure had a significant effect on the strength of the joint (p < 0.05). For larger particle sizes, the pressure had no effect. After abrasive blasting using SiC, the Ni-Cr metal-ceramic joint retained its properties, even under thermal load, ensuring the joint properties’ stability during use.

Cytotoxicity and Ion Release of Functionally Graded Al₂O₃- Ti Orthopedic Biomaterial

The aim of this study was to evaluate the biocompatibility of Al2O3-Ti functionally graded material (FGM) successfully fabricated by Spark Plasma Sintering (SPS) technology, and to compare with pure Ti and alumina. Pre-osteoblast MC3T3-E1 cells were used to examine cell viability, proliferation and differentiation using lactate dehydrogenase (LDH) cytotoxicity detection kit, MTT assay and Alkaline Phosphatase (ALP) colorimetric test at different time points. Furthermore, ion release from the materials into the culture medium was assessed. The results showed cell viability over 80% for FGM and alumina which dismissed any cytotoxicity risk due to materials or manufacturing. The results of MTT tests identified superiority of FGM than Ti and alumina, particularly in late proliferation. Nevertheless, in cell differentiation, all materials performed similarly with no statistical differences. Furthermore, it was indicated that Ti had no ion release, while alumina had small amount of Al ion dissolution. FGM, however, had more ions detachment, particularly Al ions.

The effect of thermo-mechanical fatigue on the retentive force and dimensional changes in polyetheretherketone clasps with different thickness and undercut

PURPOSE

Esthetic expectations have increased the use of polyetheretherketone (PEEK) clasps as alternatives to Cr-Co in removable partial dentures (RPDs). The objective of this study was to evaluate the retentive force and dimensional change of clasps with different thickness and undercut made from PEEK by the thermo-mechanical fatigue.

MATERIALS AND METHODS

PEEK clasps (N = 48) with thicknesses of 1 or 1.50 mm and 48 premolar monolithic zirconia crowns with undercuts of 0.25 mm or 0.50 mm were fabricated. Samples are divided into four groups (C1-C4) and were subjected to 7200 thermal aging cycles (at 5 - 55℃). The changes in the retentive force and dimensions of the clasps were measured by micro-stress testing and micro-CT devices from five measurement points (M1 - M5). One-way ANOVA, paired t-test, two-way repeated ANOVA, and post-hoc tests were used to analyze the data (P < .05).

RESULTS

The retentive forces of C1, C2, C3, and C4 groups in initial and final test were found to be 4.389-3.388 N, 4.67 - 3.396 N, 5.161 - 4.096 N, 5.459 - 4.141 N, respectively. The effects of retentive force of all PEEK clasps groups were significant decreased. Thermo-mechanical cycles caused significant dimensional changes at points with M2, M4, and M5, and abraded the clasp corners and increased the distance between the ends of the clasp, resulting in reduced retentive forces (P^* = .016, P^* = .042, P < .001, respectively).

CONCLUSION

Thermo-mechanical aging decreases the retentive forces in PEEK clasps. Increasing the thickness and undercut amount of clasps decreases the amount of dimensional change. The values measured after aging are within the clinically acceptable limits.

The biocompatibility and mechanical properties of plasma sprayed zirconia coated abutment

PURPOSE

The aim of this study was to evaluate the clinical performance and reliability of plasma sprayed nanostructured zirconia (NSZ) coating.

MATERIALS AND METHODS

This study consisted of three areas of analysis: (1) Mechanical property: surface roughness of NSZ coating and bond strength between NSZ coating and titanium specimens were measured, and the microstructure of bonding interface was also observed by scanning election microscope (SEM). (2) Biocompatibility: hemolysis tests, cell proliferation tests, and rat subcutaneous implant test were conducted to evaluate the biocompatibility of NSZ coating. (3) Mechanical compatibility: fracture and artificial aging tests were performed to measure the mechanical compatibility of NSZ-coated titanium abutments.

RESULTS

In the mechanical study, 400 µm thick NSZ coatings had the highest bond strength (71.22 ± 1.02 MPa), and a compact transition layer could be observed. In addition, NSZ coating showed excellent biocompatibility in both hemolysis tests and cell proliferation tests. In subcutaneous implant test, NSZ-coated plates showed similar inflammation elimination and fibrous tissue formation processes with that of titanium specimens. Regarding fatigue tests, all NSZ-coated abutments survived in the five-year fatigue test and showed sufficient fracture strength (407.65–663.7 N) for incisor teeth.

CONCLUSION

In this study, the plasma-sprayed NSZ-coated titanium abutments presented sufficient fracture strength and biocompatibility, and it was demonstrated that plasma spray was a reliable method to prepare high-quality zirconia coating.

Massive osteolysis due to galvanic corrosion after total knee arthroplasty: a rare cause for early revision?

A 66-year-old male underwent a total knee arthroplasty for osteoarthritis after previous anterior cruciate ligament (ACL) reconstruction. Seven years postoperatively, a symptomatic large lytic lesion was present surrounding the tibial stem. A titanium interference screw, which was used prior to fixate the Anterior Cruciate Ligament (ACL) graft, was in direct contact with the tibial component. Galvanic corrosion may have attributed to the development of the lytic lesion. It is advised to remove any metal hardware in the vicinity of joint prosthesis in order to prevent a possible galvanic corrosive reaction.

Evaluation of the effects of the solution used for electrochemical dissolution of nickel-titanium endodontic files on dentine structure, microhardness and cell viability

AIM

To evaluate the effects of the [NaF 12 g L^-1  + NaCl 1 g L^-1 ] solution used in the electrochemical dissolution process of fractured endodontic files, as well as its NiTi-containing product, on dentine hardness, topography and human fibroblast viability.

METHODOLOGY

Sixty single-rooted human teeth were evaluated for dentine microhardness using the Vickers hardness test and the area and number of dentinal tubules by scanning electron microscopy. The samples were divided according to the dentine surface treatment: distilled water; 17% EDTA; [NaF 12 g L^-1  + NaCl 1 g L^-1 ]; and 17% EDTA + [NaF 12 g L^-1  + NaCl 1 g L^-1 ]. Thirty-six single-rooted human teeth were divided according to the irrigation protocol: Dulbecco's Modified Eagle's Medium + 10% foetal bovine serum; 5.25% NaOCl; [NaF 12 g L^-1  + NaCl 1 g L^-1 ]; and [NaF 12 g L^-1  + NaCl 1 g L^-1  + NiTi]. The extracts in contact with the apical foramen were used in the MTT assay to evaluate human fibroblast viability, with dilutions of 100%, 50%, 25% and 12.5%. Statistical tests used were paired t-tests, one-way anova, Tukey's test, Kruskal-Wallis test and Dunn's post-test.

RESULTS

The [NaF 12 g L^-1  + NaCl 1 g L^-1 ] solution did not modify dentine microhardness or the average dentinal tubule area. However, EDTA induced changes in dentine structure and microhardness (P < 0.05). The [NaF 12 g L^-1  + NaCl 1 g L^-1 ] solution, and its NiTi-containing product had lower cytotoxicity than NaOCl at dilutions of 25% and 50% (P < 0.01).

CONCLUSIONS

The [NaF 12 g L^-1  + NaCl 1 g L^-1 ] solution did not alter dentine microhardness or damage the dentine structure. It also demonstrated lower cytotoxicity than NaOCl.