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Register a new userNi release from polished or PFM fired Ni-Cr dental casting alloys
تحرر النيكل من خلائط نيكل – كروم السنية المصبوبة بعد تلميعها أو معالجتها حرارياً لخبز الخزف
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سهام سايس( باحث )
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قد يتسبب معدن النيكل بسمية جهازية و تحسس ، حيث يرتبط التقبل الحيـوي للخلائط السنية المصبوبة بمقدار تحرر العناصر منها . هدفت هذه الدراسة إلى تحديد علاقة تحرر النيكل من خلائط نيكل-كـروم السـنية بتركيـب هـذه الخلائط، و إلى تحديد تأثير المعالجة الحرارية لخلائط نيكل-كروم فـي أثنـاء عملية خبز الخزف في تحرر النيكل. استخدمت في هذه الدراسة خمس خلائط نيكل-كروم شائعة الاسـتخدام فـي الممارسة السريرية، احتوت على تراكيز نيكل مختلفة تراوحت بـين ٣،٥٩– ٨١ % احتوت اثنتان منها على البريليوم.
Nickel metal may cause systemic toxicity and allergy The compatibility of dental casting alloys correlates with their release of elements .The aim of this study was to specify the relationship of the release of nickel from Ni- Cr dental alloys with their composition , and to determine the effects of thermal treatment of Ni-Cr alloys during porcelain firing process on the release of nickel . Ranging Five Ni-Cr alloys commonly used in clinical practice were used, They have different nickel percentage Ranging between ٥٩،٣ and ٨١ % , two of them containing beryllium .
References used
Bayramoglu G , Alemdaroglu T, Kedici S, Aksut AA , ; The effect of PH on the corrosion of dental metal alloys . J Oral Rehabil2000
Benatti OFM, Miranda WG, Muench A : In vitro and in vivo corrosion evaluation of nickel – chromium and copper – aluminum based alloys . J Prosthet Dent2000
Bezzon OL : Allergic sensitivity to several base metals : A clinical report.J Prosthet Dent1993
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Co-Cr alloys have excellent corrosion resistance, but in the
ceramic firing process, they are exposed to high temperatures that may affect the alloy corrosion causing ions' release.
We aimed to study the effect of ceramic firing on Co, Cr ions rele
ase from Co-Cr frameworks.
So, 30 Co-Cr models were fabricated and divided randomly into
two equal groups: 1st group: (control), 2nd group: exposed to ceramic firing conditions. Then samples were submerged in artificial saliva for one month, and measurements of released ions were performed using atomic absorption spectrometry.
Concentrations of both cobalt and chromium ions released in
control group (in μg/l) were less than those in 2nd group (without a
statistically significant difference).
We can consider ceramic firing as safe and acceptable process
that slightly increase Co, Cr ions release from Co-Cr frameworks.
The Syrian natural zeolite from om'ozon area has been studied as adsorbent for Ni(II) ions from aqueous solution. The removal of Ni(II) ions under different conditions was studied adsorption of Ni(II) enhanced with an increase of initial concentratio
n, temperature and PH .all experiments were carried out at contact time 6h.
The amount of Ni(II) adsorption was increased from 16.36 mgNi/g for initial solution concentration of 100mg Ni/l to 71.33 mgNi/g (for C0=1000mgNi/L). The experimental data fitted well to Langmuir isotherm. The maximum capacity was qmax=142.85mgNi/g Adsorption amount at 298K varies from 16.36mgNi/g for initial solution concentration of 100mg Ni/l to 47.93mg Ni/g(for C0=400mgNi/L) and it increases at 333K to 16.65 mgNi/g and 51mgNi/g (for C0=100 and 400 mg Ni/L )respectively. The adsorption of Ni(II) ions was increased by increasing PH up to ~ 5 and then stabilized up to PH=6 and after that the precipitation process was accured.
The aim of this study is to evaluate the role of Bauhinia variegate, Bouganivillea
glabra, Ligustrum vulgare and Ficus brnjamina as bioaccumulators for Nickel. The
concentration of Nickel in the studied plant leaves, bark, wood and soils in Al-Fors
an
Garden (Lattakia City) was determined. The results showed that the Nickel concentration
in the Ficus brnjamina leaves and bark was significantly high (11.04 and 12.37 ppm)
respectively compared to other studied plants, whereas the nickel concentration was
approximately the same in the other studied parts, and approximately the same as its
natural concentration in plants. Our results also showed that the nickel concentration in the
studied soil did not exceed the international norms of children gardens (about 57ppm), but
it was very low regarding the park soils. The relationship between the nickel concentration
in Ficus brnjamina wood and Bouganivillea glabra bark was the most significant.
Powder metallurgy method was used during this study to manufactor magnetic
specimens of the two alloys: FeNi65% and FeNi78%. These specimens were treated by
heat with or without the presence of of magnetic field. The mangetic properties was
amusem
ent by using special measurement circle. Crystalline structures were studied
using XRD.
It was recently noted that the costs of the
base metal alloy manufacturing have been increased, so some dental
laboratories have recasted the alloy many times although the company's
recommendations by using the alloy once. Therefore, this study aims to
investigate the effect of re-casting the Co- Cr alloy several times on
bridge bending.
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