The effect of remelting various combinations of new and used cobalt-chromium alloy on the mechanical properties and microstructure of the alloy

Gupta, Sharad; Mehta, Aruna

doi:10.4103/0970-9290.102220

Cited by 8 publications

(6 citation statements)

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“…(2007) noticed a significant increase in Vickers hardness appearing in the fifth recast. Gupta and Mehta (2012) reported that repeated remelting of base metal alloy for dental casting without adding new alloy will affect the alloy properties. The increase in hardness reported in the work maybe due to intermetallic and carbide formation.…”

Section: Hardnessmentioning

confidence: 99%

“…Reisbick and Brantley (1995) reported no significant diminishment in the tensile properties after recasting type III Gold (46%) alloy up to three times. However, Gupta and Mehta (2012) noticed compositional and physical changes along with decreased fluidity after remelting of base alloys. Harcourt and Cotterill (1965) suggested that the elements such as Co, Ni, Cu, Cr, Sn, Fe, and Zn could alter during recasting due to evaporation and oxidation.…”

Section: Introductionmentioning

confidence: 99%

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Bulk Recycling of Ni-Cr-Mo Dental Alloy - A Sustainable Approach

Batra¹,

Detroja²,

Biradar³

et al. 2023

ASMScJ

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Many dental alloy manufacturers instruct not to recast alloys, but the dental laboratories reuse the casting surplus for economic reasons. It is a controversial topic in dental practice, so the present study attempts to assess the effects of recasting Ni-Cr-Mo alloys. Three sets of alloy pellets were recast. The first set was melted and allowed to solidify. The second and third sets were recast two times and three times, respectively. The elemental composition of all the recast samples was analysed using ED-XRF (Energy Dispersive X-ray Fluorescence) spectrometer. The variation in the chemical composition for the number of recasting was reported. It was observed that the recasting for one time doesn't change the elemental composition to a considerable extent. However, further increase in the number of recasting two and three times, the depletion of the major alloying elements (Ni, Cr, and Mo) was notable. Hence, the current study intends to calculate the exact amount of the depleted elements after each recast. Also, to have a theoretical analysis of the elements necessary for making a master alloy that can be added during the recasting to avoid changes in elemental composition. Moreover, the microstructure of the recast samples was observed using an optical electron microscope (OEM). No drastic variation in the microstructure was observed for the alloy with several melting and solidifying cycles, except for the orientation of the dendritic arm. Furthermore, to confirm the mechanical strength of the recast alloy Vickers microhardness test was conducted. The average microhardness of the base Ni-Cr-Mo alloy was 216 HV, and recasting once does not affect the hardness value. However, the three-time recast alloy showed only a 9% decrement. Finally, it can be concluded that the number of recasting can be as many times provided depleted elements are added in exact proportion after each recast. The current research suggests recycling dental alloys in bulk outside a dental clinic, and a dentist should responsibly segregate different base metal alloys and promote sustainable dentistry.

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Section: Hardnessmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Bulk Recycling of Ni-Cr-Mo Dental Alloy - A Sustainable Approach

Batra¹,

Detroja²,

Biradar³

et al. 2023

ASMScJ

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show abstract

“…9 Alloy recasting in dentistry, without the addition of new alloys, can affect the mechanical properties and affect the microstructure of the alloy. 11 Fracture toughness is important in frame denture and recasting is also needed to obtain frame denture that can be applied in dentistry. Based on the abovementioned description, this study examined whether there is an effect of Co-Cr alloy recasting on fracture toughness.…”

Section: Introductionmentioning

confidence: 99%

Effect of Co-Cr alloy recasting on the fracture toughness

Eka

Dharmastiti

Widjijono

2022

Majalah Kedokteran Gigi Indonesia

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Frame denture generally uses Co-Cr alloy. However, alloy is expensive, so dental laboratories use residual sprue casting for recasting. The purpose of this study was to determine the effect of Co-Cr alloy recasting on fracture toughness. This was a laboratory experiment, with five sample groups, namely R0: 100% of new alloys; R1: 50% one-time recasting procedure and 50% new alloys, R2: 50% two-time recasting procedure and 50% new alloys, R3: 50% three-time recasting procedure and 50% new alloys, R4: 50% four-time recasting procedure and 50% new alloys. Fracture toughness was tested using a universal testing machine; the data were analyzed by One-Way Anova test and LSD (p>0.05). The results showed that the fracture toughness was 233.103 MPa-m1/2 in R4, and the highest was 242.435 MPa-m1/2 in R0. The results of the analysis by the LSD test on fracture toughness showed that there were no significant differences in R0 with R1 and R2, but there were significant differences between R0 with R3 and R4. There was a decrease after recasting in each group because of the missing elements of the Co-Cr alloy. The percentage of each element decreased due to oxidation and evaporation during heating. There was a change in the composition of the Co-Cr alloy in R3 and R4. There was a decrease in the fracture toughness. Variation in recasting frequency of Co-Cr alloy affected the fracture toughness. In each sample groups, the fracture toughness of Co-Cr alloy decreased after recasting.

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“…Recasting with at least 50% of new alloy also does not affect the physico-chemical and mechanical properties of the alloys [15]. Some reports show that even 25% of new alloy could be used, when remelting only up to one or two times [16], while others state that using the contributions of scrap in castings deteriorates the strength properties substantially [17].…”

Section: Introductionmentioning

confidence: 99%

Investigation of CoCr Dental Alloy: Example from a Casting Workflow Standpoint

et al. 2021

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Cobalt-chromium (CoCr) alloys have been used in dentistry for dental bridges, crowns and implants for decades. When using CoCr alloys, a number of fractures have occurred in the Dental Laboratory, both when handling the castings and after they have been placed in the patient’s mouth. It is assumed that the key cause of the resulting fractures of CoCr dental bridges is the casting process, which includes the preparation and mixing of the basic components of the CoCr dental alloy, unstable solidification and the final treatment of the tooth casting surface. The aim of this study was, therefore, to examine three castings differently prepared from the CoCr alloy. For the initial CoCr alloy, we selected the one supplied directly from the manufacturer; three test samples were CoCr alloy remelted four times in the same crucible, while the fourth sample was the remaining solidified alloy from the crucible, taken at the last remelting. Characterisation of the microstructure of all four samples was performed by optical and scanning electron microscopy equipped with an energy dispersive X-ray spectroscope and X-ray diffractometry. Microhardness measurements were also performed. The investigation revealed that the microstructure of the castings is composed of a CoCr alloy matrix with a eutectic interdendritic composition and interdendritic precipitates, which were rich in W and Mo. The two oxides were identified as chromium oxide with silicon content and chromium oxide, which originated from the CoCr alloy as casting residue. The high content of silicon in the chromium oxide can be attributed to the silicon oxide from the ceramic melting crucible, mixed in with the remains from the CoCr alloy melting. The second oxide showed a more regular elemental content for chromium oxide, mixed with a small quantity of impurities and the casting CoCr alloy. Based on this research, some recommendations were made for working with CoCr alloys in the Dental Laboratory, with the aim of reducing the risk of dental bridge fractures in the future.

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The effect of remelting various combinations of new and used cobalt-chromium alloy on the mechanical properties and microstructure of the alloy

Cited by 8 publications

References 0 publications

Bulk Recycling of Ni-Cr-Mo Dental Alloy - A Sustainable Approach

Bulk Recycling of Ni-Cr-Mo Dental Alloy - A Sustainable Approach

Effect of Co-Cr alloy recasting on the fracture toughness

Investigation of CoCr Dental Alloy: Example from a Casting Workflow Standpoint

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