Types Of Dental Alloys Research Articles

Effect of Cu and Ti electrodes on surface and electrochemical properties of Electro Discharge Machined (EDMed) structures made of Co-Cr and Ti dental alloys

ObjectivesPrevious studies have shown that the use of Cu electrodes compromises the electrochemical properties of Co-Cr and Ti alloys used for the fabrication of implant retained superstructures by Electro Discharge Machining (EDM). A possible solution is the use of Ti instead of Cu electrodes and thus the aim of this study was to evaluate the effect of Cu and Ti electrodes on surface and electrochemical properties of two types of dental alloys used for fabrication of implant retained superstructures after EDM. MethodsThree full arch frameworks were prepared from a Co–Cr and three from Ti6Al7Nb alloy. One framework from each alloy was used as control, one was subjected to EDM with Cu electrodes and the last one with Ti electrodes. Morphological and elemental characterization was studied by SEM/EDX. The electrochemical properties of the alloys were evaluated by Open Circuit Potential (OCP) and Linear Sweep Voltammetry (LSV) in Ringer’s solution. Electrochemical data were analyzed statistically by one way ANOVA and SNK multiple comparison tests at a = 0.05 ResultsAll groups demonstrate the typical surface after EDM treatment with almost circular valleys and an increase in C and O content compared to control groups. Both alloys demonstrated an uptake of C and Cu by Cu electrodes and C and Ti after treatment with Ti electrodes. The use of Cu electrodes had a detrimental effect on corrosion resistance of Ti alloy. SignificanceThe use of Ti electrodes mitigates the degradation of electrochemical properties compared to Cu electrodes and from this standpoint is safer for the EDM of implant retained superstructures made of Co-Cr and Ti alloys.

Periodontal clinico-morphological changes in patients wearing old nickel–chromium and copper alloys bridges

Elderly population frequently presents more than one prosthetic restoration realized from different types of dental alloys which, in time, suffer various alterations in the oral environment. Metallic ions are released in saliva due to its electrolytic qualities, interacting with the contact tissues. Studies regarding cytotoxicity of dental alloys are providing contradictory results. Besides biocompatibility, the microbial factor is also greatly influencing the long-term success of the prosthetic rehabilitation. This study’s aim was to assess the response of the gingival tissue to nickel–chromium (Ni–Cr) and copper (Cu)-based dental casting alloys from fixed dentures present in many patients from Romania. Gingival samples were taken from 124 patients wearing fixed dental restorations made from these two types of alloys from injured areas surrounding the abutment teeth; histological specimens were prepared, fixed in 10% neutral buffered formalin, paraffin-embedded and stained with Hematoxylin–Eosin (HE). Histological analysis showed the existence of a chronic inflammatory infiltrate in the gingival chorion, necrosis areas, and vascular congestion. Various morphological alterations appeared, depending on the intensity of the inflammation and the immune response. The surface epithelium suffered a hyperplasic reaction, either limited to acanthosis or involving the whole epithelium, the release of the Cu2+ and Ni2+ ions from the dental alloys used in bridges and crowns being responsible for inducing gingival hyperplasia and a chronic inflammation in the areas situated around the abutment teeth. The immunohistochemical study allowed us to observe an increased number of positive cluster of differentiation 3 (CD3) T-lymphocytes in periodontium, proving that the cellular immune response is rapid and intense.

Applications of Laser Welding in Dentistry: A State-of-the-Art Review.

The dental industry without lasers is inconceivable right now. This captivating technology has outlasted other possible alternative technologies applied in dentistry in the past due to its precision, accuracy, minimal invasive effect as well as faster operating time. Other alternatives such as soldering, resistance (spot) welding, plasma (torch) welding, and single pulse tungsten inert gas welding have their pros and cons; nevertheless, laser welding remains the most suitable option so far for dental application. This paper attempts to give an insight into the laser principle and types of lasers used for dental purposes, types of dental alloys used by the dentist, and effect of laser parameters on prosthesis/implants. It is apparent from the literature review that laser assisted dental welding will continue to grow and will become an unparalleled technology for dental arena.

Metal-composite adhesion based on diazonium chemistry

ObjectiveComposite resins do not adhere well to dental alloys. This weak bond can result in failure at the composite-metal interface in fixed dental prostheses and orthodontic brackets. The aim of this study was to develop a new adhesive, based on diazonium chemistry, to facilitate chemical bonding between dental alloys and composite resin. MethodsSamples of two types of dental alloys, stainless steel and cobalt chromium were primed with a diazonium layer in order to create a surface coating favorable for composite adhesion. Untreated metal samples served as controls. The surface chemical composition of the treated and untreated samples was analyzed by X-ray photoelectron spectroscopy (XPS) and the tensile strength of the bond with composite resin was measured. The diazonium adhesive was also tested for shear bond strength between stainless steel orthodontic brackets and teeth. ResultsXPS confirmed the presence of a diazonium coating on the treated metals. The coating significantly increased the tensile and shear bond strengths by three and four folds respectively between the treated alloys and composite resin. Conclusion: diazonium chemistry can be used to develop composite adhesives for dental alloys. SignificanceDiazonium adhesion can effectively achieve a strong chemical bond between dental alloys and composite resin. This technology can be used for composite repair of fractured crowns, for crown cementation with resin based cements, and for bracket bonding.

Study on gingival tissue reaction to the materials used for making dental prosthesis

Fixed prosthetic restorations may generate periodontal irritation by various and complex mechanisms especially in the presence of the microbial factor. In this regard, changes that compromise the functional value of the support structures of the teeth occur. Studies on patients wearing fixed denture show that those prosthetic structures facilitate plaque accumulation. Close supervision leads to prevention of periodontal diseases, through learning of a proper hygiene. Between the marginal periodontium and the prosthetic restoration, there must be a relation of ‘mutual protection’ or at least ‘mutual respect’. In this study, we tried to analyze the reaction of the periodontal tissue in contact with fixed prosthesis depending on the prosthetic material used. There were 102 fixed prostheses considered by this study that have generated reactions in the periodontal tissues with which came into contact. Thus, from the total number of 102 fixed dental prostheses, 75% were made from metal alloys based on copper, 18% from Cr–Ni alloys, 2% from Cr–Co alloys, 4% from gold alloys, and one from stainless steel. In 35% of the cases, the patients had multiple fixed dentures made from different types of dental alloys, cases in which the symptoms of the periodontal problems may be also linked to the phenomenon of oral galvanism. The histological study showed various morphological changes from one patient to another, depending on the intensity of the inflammatory and reparative response, the associated diseases (diabetes, dyslipidemia, cardiovascular diseases) and especially on the dental hygiene status. Fixed prosthesis, in the absence of a proper cervical adaptation and an adequate local hygiene, may act as an irritative thorn and may induce gingivitis and periodontitis phenomena.

Influence of recasting different types of dental alloys on gingival fibroblast cytotoxicity

Surplus alloy from the initial casting is commonly reused with the addition of new alloy. This recasting procedure could affect the cytotoxicity of dental alloys. The purpose of this in vitro study was to evaluate the effect of repeated casting of high-noble and base metal alloys on gingival fibroblast cytotoxicity. Disk-shaped specimens (5 × 2 mm, n=60) of a high-noble (Au-Pt) and 2 base metal (Ni-Cr and Cr-Co, n=20) alloys were prepared with 100% new alloy and 50%, 65%, and 100% once recast alloy. The elemental composition of specimens was analyzed with X-ray energy-dispersive spectroscopy. Five specimens from each group were conditioned in saline with 3% fetal bovine serum albumin. The conditioning media were analyzed for elemental release with atomic absorption spectroscopy. Cytotoxic effects were assessed on human gingival fibroblast with a 3-(4.5-dimethylthiazol-2-yl)-2.5-diphenyl tetrazolium bromide (MTT) colorimetric assay. The data were analyzed with 1-way and 2-way ANOVA and Tukey's HSD multiple comparison test (α-=.05). Elemental compositions of Co-Cr and Au-Pt alloys were significantly different among casting protocols. Elemental release of Co-Cr and Ni-Cr alloys was significantly different between new and recast specimens (P<.001). Nickel release increased with recast alloy addition. The 2-way ANOVA showed a significant effect of the casting procedure (P<.001) alloy group (P<.001) and their interaction for cytotoxicity (P<.001). The Ni-Cr alloy groups with 65% and 100% recast alloy had lower cellular activity than all other specimens (P<.001). The results of this study indicated that alloys containing nickel have increased cytotoxic effects and that composition of the alloys affected the cytotoxicity. Furthermore, recasting nickel-containing alloys with 65% surplus metal addition significantly increased the cytotoxic activity.

The effect of Electro Discharge Machining (EDM) on the corrosion resistance of dental alloys

Objective The aim of the present study was to evaluate the effect of Electro Discharge Machining (EDM) on the corrosion resistance of two types of dental alloys used for fabrication of implant retained superstructures. Methods Two groups of specimens were prepared from a Co–Cr (Okta-C) and a grade II cpTi (Biotan) alloys respectively. Half of the specimens were subjected to EDM with Cu electrodes and the rest were conventionally finished (CF). The corrosion resistance of the alloys was evaluated by anodic polarization in Ringer's solution. Morphological and elemental alterations before and after corrosion testing were studied by SEM/EDX. Six regions were analyzed on each surface before and after corrosion testing and the results were statistically analyzed by paired t-test ( a = 0.05). Results EDM demonstrated inferior corrosion resistance compared to CF surfaces, the latter being passive in a wider range of potential demonstrating higher polarization resistance and lower I corr values. Morphological alterations were found before and after corrosion testing for both materials tested after SEM analysis. EDX showed a significant decrease in Mo, Cr, Co, Cu (Co–Cr) and Ti, Cu (cpTi) after electrochemical testing plus an increase in C. Significance According to the results of this study the EDM procedure decreases the corrosion resistance of both the alloys tested, increasing thus the risk of possible adverse biological reactions.

Bond Strength of Resin Cements to Co-Cr and Ni-Cr Metal Alloys Using Adhesive Primers

The aim of this study was to evaluate the effectiveness of adhesive primers (APs) applied to Co-Cr and Ni-Cr metal alloys on the bond strength of resin cements to alloys. Eight cementing systems were evaluated, consisting of four resin cements (Bistite II DC, LinkMax, Panavia F 2.0, RelyX Unicem) with or without their respective APs (Metaltite, Metal Primer II, Alloy Primer, Ceramic Primer). The two types of dental alloys (Co-Cr, Ni-Cr) were cast in plate specimens (10 x 5 x 1 mm(3)) from resin patterns. After casting, the plates were sandblasted with aluminum oxide (100 microm) and randomly divided into eight groups (n = 6). Each surface to be bonded was treated with one of eight cementing systems. Three resin cement cylinders (0.5 mm high, 0.75 mm diameter) were built on each bonded metal alloy surface, using a Tygon tubing mold. After water storage for 24 hours, specimens were subjected to micro-shear testing. Data were statistically analyzed by two-way ANOVA and Tukey's studentized range test. The application of Metal Primer II resulted in a significantly higher bond strength for LinkMax resin cement when applied in both metal alloys. In general, the cementing systems had higher bond strengths in Co-Cr alloy than in Ni-Cr. The use of AP between alloy metal surfaces and resin cements did not increase the bond strength for most cementing systems evaluated.

Comparative study of the corrosion behavior between casting and recasting of three types of non-precious alloys.

Background: The practice of recasting in dentistry became familiar long time ago and many studies concerned with the effect of recasting on the physical and mechanical properties of non-precious alloys but only few studies concerned with the effect of recasting on the electrochemical properties .The aim of this study is to evaluate the corrosion behavior of three types of non-precious alloys which are Co-Cr, Ni-Cr (hard type) and Ni-Cr (soft type) before casting and after recasting. Materials and methods: Three types of dental alloys were used in this study Co-Cr and two types of Ni-Cr alloys (hard type used for denture base material and soft type used for crown and bridge ).A cylindrical disc-shape design was used in this study to prepare the specimen ,this in accordance to ASTM. The specimen were exposed to corrosion evaluation before casting and after recasting by potentiostatic polarization measurements .In addition to that the specimen were evaluated by microscopic examination before casting and after casting as well as after recasting Results: The results which is concerned with Co-Cr alloys showed that the corrosion potential shifted to more negative values with increasing recasting operation while for Ni-Cr hard type the corrosion potential shifted to less negative potential indicating a decrease in its activity for corrosion .On the other hand ,the soft type of Ni-Cr demonstrated that the corrosion potential became slightly more negative with recasting indicating some increase in the activity of the specimen for corrosion . Conclusion: Recasting generally increased the tendency of the alloys for corrosion as indicated by the behavior of Co-Cr and (Ni-Cr)2 alloys but the reverse behavior was observed with (Ni-Cr)1 alloy .Also the diffusion controlled corrosion was appreciably high on (Ni-Cr) alloys but recasting generally increased the (dcc) suggesting its effect in decreasing the ability of oxide film for corrosion protection

Evaluation of the apical seal after intraradicular retainer removal with ultrasound or carbide bur

There are situations in which intraradicular retainers have to be removed and replaced. The objective of this research was to evaluate the apical seal after the removal of a custom cast post and core with a carbide bur or with an ultrasound apparatus. Twenty five roots of extracted human incisors were used. They were endodontically treated and prepared to receive the posts. The posts and cores were cast with 2 types of dental alloys, CuAlZn and PdAg, and were cemented with zinc phosphate cement. After 24 hours, they were removed using the two above mentioned techniques. Then, the roots had their external surface made impermeable by two layers of cyanoacrylate adhesive, leaving only the cervical area for dye penetration. The teeth were immersed in rhodamine for 24 hours. They were then cut and observed under an optical microscope and analyzed with appropriate software (Imagelab). The results were submitted to ANOVA, and they evidenced that, regarding the alloy factor, PdAg posts presented a larger mean infiltration value (2.23 +/- 0.48 mm) as compared to the posts made of CuAlZn (1.39 +/- 0.48 mm) (p = 0.025). Regarding the technique factor, there was no significant difference (p = 0.9) between the removal of the intraradicular retainer using ultrasound (1.99 +/- 0.62 mm) or using a rotating cutting instrument (1.62 +/- 0.62 mm). Under these experimental conditions, it was possible to conclude that the degree of apical leakage was directly related to the alloy type, and it was present in both techniques used.

Long term urinary platinum, palladium, and gold excretion of patients after insertion of noble metal dental alloys

The aim of this study was to investigate to which extent noble-metal dental alloys contribute to the total platinum (Pt), palladium (Pd), and gold (Au) body burden of the general population. The urinary Pt, Pd, and Au excretion was determined in three non-occupationally exposed volunteers before and up to 3 months after insertion of a highgold dentalalloy. The in-vitro release of Pt, Pd, and Au from four different types of dental alloys into either artificial saliva or 1% lactic acid solution was additionally investigated. The Pt, Pd, and Au concentrations were determined by sector field inductively coupled plasma mass spectrometry (SF-ICP-MS). Before insertion of the high-gold dental alloy, the Pt excretion of the patients ranged between 1.0 and 7.4 ng l-1 (0.6-3.3 ng g-1 creatinine). In the immediate post-insertion phase the Pt excretion rose to 10.5-59.6 ng l-1 (14.5-33.2 ng g-1 creatinine). This is a mean increase by a factor of 12 compared with the average Pt excretion before insertion. Three months after insertion, the Pt excretion was still elevated by a factor of 7. Contrary to Pt, the Au and Pd excretion in urine was not significantly increased after insertion of this type of high-gold dental alloy. Our in-vitro investigations confirm the assumption that Pt, Pd, and Au are released from noble metal containing dental alloys by corrosion. Under the applied conditions, the release was in the lower ng cm-2 range. It can be concluded that the Pt release from dental alloys can predominantly contribute to the Pt exposure of non-occupationally exposed persons. It can exceed the exposure from all other environmental sources including the Pt release from automobile exhaust catalysts.

歯科用合金の新しい選択基準

Mechanical properties of various types of dental alloys were evaluated by measuring tensile strength, Vicker's hardness, elongation, 0.2% proof stress and modulus of elasticity. Specimens were made from dental casting alloys, dental alloys for ceramometal, chromium cobalt base metal alloys for casting, and wrought base metal alloys, respectively.It was expected that results of the test reveal the selection criteria of the dental alloys. The followings are the results of this test:1. Heat treatment has effect upon 0.2% proof stress of the alloys, but does not have upon modulus of elasticity. Required Time-Temperature for heat treatment should be obeyed strictly.2. Base metal alloy features high modulus of elasticity and low 0.2% proof stress thus its metal frame needs to be bulky when it is used for long-span bridge or adhesion bridge being subjected by severe occlusal force.3. High-gold dental alloy for ceramometal may not be suitable for long-span bridge.4. Chromium cobalt wrought alloy is suitable for the clasp of removable partial denture. But, care should be taken when the wrought wire is subjected to heat such as soldering. Severe heat treatment lowers 0.2% proof stress.5. The Pt added high gold casting alloy, namely MAX G, has superior 0.2% proof stress and high modulus of elasticity among the gold casting alloys. This indicates that MAX G is suitable for long-span and adhesion bridges.6. The gold alloys for ceramometal, namely TGB 50 and TGB 30, have superior 0.2% proof stress and modulus of elasticity among the gold alloys.