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Article
The Effect of Recasting on the Castability of Prepared Nickel-Chromium Dental Base-Metal Casting Alloy

Authors: Suhad Jabar Hemed سهى جبار حميد --- Mohammed Talib Al-khafagy محمد طالب الخفاجي
Journal: Al-Qadisiyah Medical Journal مجلة القادسية الطبية ISSN: 18170153 Year: 2007 Volume: 3 Issue: 4 Pages: 103-111
Publisher: Al-Qadisiyah University جامعة القادسية

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Abstract

Background: Evaluation the effect of recasting process on the castability value of prepared Ni-Cr dental base-metal casting alloy and compare it with other conventional alloy.Materials and methods: The prepared Ni-Cr alloy was locally prepared in Iraq by Al-Khafagy (2003), while the CB Blando Ni-Cr was used as conventional alloy. A wax mash of 1mm opening and (10*10) segments square was invested in phosphate-bonded investment and casted by using induction casting machine. The number of complete cast segments was counted, divided by (220) and multiplied by (100) to obtain a percentage designated the castability value (Cv).Results and discussion: The prepared Ni-Cr alloy samples were showed lower castability values than the conventional alloy, this may be related to unalloyed silicon and manages and loss the role of these elements in improvement of castability of prepared Ni-Cr alloy. The castibility value was decreased as the percentage of used alloy increased, however, ANOVA test revealed a non significant differences within the groups. Practically, the experimental and conventional alloys could be recastd if the recasted process will not affect the other properties of such alloys.


Article
Metal Ion Release From Ni-Cr Alloy with Different Artificial Saliva Acidities

Author: Amrah Y.Al-Jmmal
Journal: Al-Rafidain Dental Journal مجلة الرافدين لطب الأسنان ISSN: 18121217 Year: 2014 Volume: 14 Issue: 2 Pages: 266-271
Publisher: Mosul University جامعة الموصل

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Abstract

AIMS: evaluate the effects of changes in salivary pH on ion release from the Ni – Cr alloy at different time and calculate the amount of nickel, chromium ions released from these alloyes.MATERIALS AND METHODS: Fourty eight specimens of Ni-Cr alloy were divided, four specimens immersed in each of four types of artificial saliva at different pH (7 as control,6,5 and 2.5), in three storage periods (12, 24 and 36days). All test tubes were incubated at 37°C. After the immersion time was finished the quantities of metallic ions released for Ni and Cr were measured for each test solutions after 12, 24and 36days of immersion by atomic absorption spectroscopy. REULTS: The results of Nickel and Chromium ion release showed a statistically significant difference at p≤0.05 between three immersion solutions after (12, 24, 36) days, artificial saliva (pH2.5) showed higher rate of Ni and Cr release than artificial saliva (pH 7as control ,6,5) after various immersion times. It should mention the nickel ion release has been found to be more than chromium ion release. CONCLUSIONS: There is an evidence that the Ni and Cr ions release from Ni-Cr alloy at the presence of different acidity of artificial saliva. Chromium and nickel ion release in small amount in artificial saliva with pH(6,5), while in pH 2.5 release in large amount after (12, 24, 36) days of immersion. Nickel exhibited the highest level of ion release than Cr


Article
Thermal expansion of prepared dental base-metal casting alloys

Author: Mohammed Talib Al-khafagy محمد طالب الخفاجي
Journal: Journal of baghdad college of dentistry مجلة كلية طب الاسنان بغداد ISSN: 16800087 Year: 2012 Volume: 24 Issue: 1 Pages: 17-22
Publisher: Baghdad University جامعة بغداد

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Abstract

Background: This study aimed to evaluate the linear thermal expansion of prepared Ni-Cr and Co-Cr dental basemetalcasting alloys which has been prepared locally in Iraq and compare with other conventional alloys.Materials and methods: Cylindrical shape wax specimen was prepared of (15mm) length and (5mm) diameter,which invested in phosphate-bonded investment material and casted by using induction-casting machine. The linerthermal expansion has been tested by using Iraqi-made dialometer in which the furnace was set to reach from roomtemperature to 950 C in a rate of 10 C per minute.Results and discussion: The prepared Ni-Cr and Co-Cr alloys were showed a higher linear thermal expansion than theconventional alloys, however, statistical analysis revealed non-significant differences regarding the Co-Cr alloys andhighly significant differences regarding the Ni-Cr alloys


Article
CORROSION BEHAVIOR AND ROUGHNESS OF NI-CR/AL2O3 COMPOSITES AS DENTAL RESTORATIVE
السلوك التآكلي والخشونة لمتراكبات Ni-Cr/Al2O3 كمواد تعويضية في الاسنان

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Abstract

This work investigated on the corrosion behavior and roughness of Ni-Cr alloy as dental restorative. Alumina with three weight percentages (1, 5 and 10%) added as reinforcement to fabricate Ni-Cr/alumina composites. Corrosion behavior was tested in artificial saliva at 37+1 oC and pH=4.4. The data of corrosion indicated that the addition of alumina led to reduce the dissolution of metals in base alloy due to the enhancing of Cr2O3 passive film and producing Ni3Al phase in matrix. The roughness of surface was reduced for composites compared with base alloy (Ni-Cr) which is important factor to reduce the accumulation of bacteria on restorative materials in mouth; this reduction is due to the formation of ductile Ni3Al compared with brittle Ni2Cr3 in composites.

يتضمن البحث الحالي التقصي عن السلوك التآكلي والخشونة لسبيكة نيكل – كروم، كما اضيقت الالومينا بثلاث نسب وزنية 1 و5 و 10% كتقوية للسبيكة الاساس. اجري فحص التآكل في محلول اللعاب الصناعي عند اس هيدروجيني 4.4 ودرجة حرارة 37+1 درجة مئوية وقد اظهرت النتائج بان اضافة الالومينا يؤدي الى تقليل الذوبان المعدني للسبيكة الاساس بسبب تعزيز طبقة اوكسيد الكروم الحامية وتكوين الطور Ni3Al. كما بينتْ نتائج فحص الخشونة السطحية بان المواد المتراكبة تمتلك خشونة اقل من السبيكة الاساس وهذا ما يعد عامل اساسي لتقليل تجمع البكتريا على المواد التعويضية المستخدمة داخل الفم. ان النقصان الحاصل في الخشونة سببه تكوين Ni3Al اللدن مقارنة مع الطور Ni2Cr3 الهش.

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