research centers


Search results: Found 33

Listing 1 - 10 of 33 << page
of 4
>>
Sort by

Article
A finite element analysis of the effect of different margin designs and loading positions on stress concentration in porcelain veneers

Author: Hussain F. Al-Huwaizi حسين فيصل الحويزي
Journal: Journal of baghdad college of dentistry مجلة كلية طب الاسنان بغداد ISSN: 16800087 Year: 2005 Volume: 17 Issue: 2 Pages: 8-12
Publisher: Baghdad University جامعة بغداد

Loading...
Loading...
Abstract

Background: During mastication, stress may concentrate in points in the porcelain veneer which may lead to clinical failure. This study examined whether different finishing lines and different loading positions affect the bond of the porcelain veneers.Materials and methods: A 2- dimensional finite element model was made. Location and magnitude of maximum Von Mises and shear stresses were calculated in porcelain veneer.Results: Stress was concentrated in the butt finishing line more than the deep chamfer and chamfer finishing lines. Stress was concentrated in the incisal portion more than in the cervical portion of the porcelain veneer. The incisal loading exerted stress more than the bonding strength of the bonding agent, and more than the cervical and middle third loading.Conclusion: The best stress distribution was formed around the deep chamfer finishing line. Clinical failure is inevitable in the butt finishing line and incisal loading. Incisal edge fracture of the porcelain veneer may be due to debonding of the bonding agent to the enamel and later fracture of the porcelain veneer


Article
Evaluation of the effects of porcelain firing cycles on the marginal fit changes of porcelain– fused–to–metal crowns constructed utilizing two different marginal designs and alloys

Authors: Maan R Zakaria --- Haidar H Jassim
Journal: Al-Rafidain Dental Journal مجلة الرافدين لطب الأسنان ISSN: 18121217 Year: 2003 Volume: 3 Issue: 1 Pages: 13-20
Publisher: Mosul University جامعة الموصل

Loading...
Loading...
Abstract

In this study the marginal fit changes that occurred during the porcelain firing cycles of palladium–silver alloy (Pd–Ag) and nickel–chromium alloy (Ni–Cr) coping both with shoulder and heavy chamfer facial finishing lines were investigated with light microscope. Forty copings were fabricated which were divided into four groups according to alloy type and facial finishing line, each group consisted of ten copings: Group I (Pd–Ag) alloy copings with shoulder finishing line; group II (Pd–Ag) alloy copings with heavy chamfer finishing line; group III (Ni–Cr) alloy copings with shoulder finishing line; and group IV (Ni– Cr) alloy copings with heavy chamfer finishing line. Five control metal copings (non veneered) from each group were subjected to exactly the same firing cycles without the application of porcelain. Measurements were made during five stages of crown fabrication: (1) Before degassing, (2) after degassing, (3) after opaque application, (4) after body porcelain application, and (5) after glazing. Changes in the marginal fit of the coping after the various firing stages were calculated for each coping. The statistical analysis of the results showed that the mean marginal fit changes during porcelain firing cycles of the base metal alloy copings (Ni–Cr) were significantly greater than those of noble metal alloy copings (Pd–Ag).


Article
Empirical and Simulation of Thermal Insulator of SWCNTs – Ceramic/Polymer Nanocomposites

Author: I.F. Hussen
Journal: Iraqi Journal of Applied Physics المجلة العراقية للفيزياء التطبيقية ISSN: 18132065 23091673 Year: 2011 Volume: 7 Issue: 4 Pages: 3-9
Publisher: iraqi society for alternative and renewable energy sources and techniques الجمعية العراقية لمصادر وتقنيات الطاقة البديلة والمستجدة

Loading...
Loading...
Abstract

Ablation rate and thermal conductivity coefficient for phenol formaldehyde type resole resin reinforced with single well carbon nanotubes (SWCNTs) and porcelain have been studied via oxy–acetylene flame and Lee’s disc, techniques respectively. Thermal conductivity results show, that the values increase progressively by succession of volume fraction of SWCNTs. Ablation rate behaves inversely, where it drops at high volume fraction of SWCNTs. Simulation of thermal conductivity results, which are calculated according to microstructures model and when we compared it, with the experimental results, it can be observed, that the experimental results, were located in between the parallel direction values and random direction values for SWCNTs, with respect to heat flux direction. Ablation simulation results values coming higher than experimental results values, this could be explained, as the interface affect of nanocomposites, which had high strength and strong bond force.


Article
An evaluation of the effects of different polishing materials and glazing techniques on the fracture toughness of dental porcelain

Authors: Ma’an R. Zakaria معن رشيد زكريا --- Saeed K. Shahwan سعيد شهوان
Journal: Journal of baghdad college of dentistry مجلة كلية طب الاسنان بغداد ISSN: 16800087 Year: 2012 Volume: 24 Issue: 4 Pages: 29-33
Publisher: Baghdad University جامعة بغداد

Loading...
Loading...
Abstract

Background: As there is an increase in the importance of measuring the fracture toughness of dental porcelain,different methods and materials were supposed. The aim of this study was to compare the fracture toughness offeldspathic porcelain with different polishing materials and glazing techniques.Materials and methods: Forty-nine metal-ceramic discs (width =10 mm, height =5 mm) were fabricated andrandomly divided into seven groups (n = 7); group one was left intact and considered as a control group, othergroups’ surfaces were treated with autoglaze only, applied glaze only, polished with ceramic rubber wheel only,polished with Dentaurum universal polishing paste only, polished with paste then autoglazed, and polished withpaste followed by applied glaze respectively. Porcelain fracture toughness (KIc) for each specimen was measuredby a Micro-Vickers Hardness Tester then the mean KIc for each group was determined. The data were analyzed byusing analysis of variance (ANOVA) followed by Least Significant Difference (LSD).Results: Mean porcelain fracture toughness of all groups were 1.320, 0.665, 1.469, 1.319, 1.480, 1.108, 1.548 MN/m-3/2respectively. Very high significant differences were found between the groups (P<0.001). The highest mean of KIcvalue was recorded in group VII which represented the toughest group while the lowest mean value wasrepresented by group II.Conclusions: Surface treatment of feldspathic porcelain restorations with polishing paste and applied glaze showedhighly significant increase in fracture toughness. Polishing unglazed porcelain using ceramic rubber wheel andDentaurum universal polishing paste showed no significant differences compared with specimens treated withapplied glaze only.


Article
The effect of scrap glass powder in traditional porcelain
تأثير اضافة مخلفات مسحوق الزجاج على البورسلين التقليدي

Author: Dunia K. M. Al-Nasrawy دنيا كامل مهدي النصراوي
Journal: Iraqi Journal of Physics المجلة العراقية للفيزياء ISSN: 20704003 Year: 2009 Volume: 7 Issue: 8 Pages: 11-16
Publisher: Baghdad University جامعة بغداد

Loading...
Loading...
Abstract

In this work, Soda Lime Glass (S.L.G.) powder was used ,as fluxe in traditional porcelain instead of feldspar. Two ceramics porcelain were compared; commercial or traditional porcelain that content of 50wt % kaolin, 25wt % quartz, and 25wt % feldspar. Feldspar mass was substituted by scraps soda lime glass yielding a new porcelain composition, to determine the softening points and then the effect of glass addition on porcelain firing process.
Eight samples, for each patch, were prepared and 8wt % water was added. The resulting composite blends were then die pressed at 2N, to produce disk specimens with diameter of 1.5 cm, and then they were sintered at (1000, 1100, 1200, 1250,1300,1350,1400 and 1450) &#730;C, for 2 hours in an electric furnace with a digital controller. Physical parameters, such as density, water absorption, and shrinkage were measured. It was concluded that the sintering process and physical properties were improved by heat treatment. However, the firing results showed that the addition of S.L.G. replacing feldspar lowers the melting points of porcelain and the addition of scrap powder has a positive effect on the quartz dissolution.
The purpose of the present work is to replace 25wt% of feldspar by soda lime glass in a standard porcelain composition and evaluate their differences in physical properties at different firing temperatures.

في هذا العمل ،استخدم مسحوق زجاج الصودا لايم (S.L.G) كمصهر في البورسلين التقليدي بدل الفلدسبار،حيث تم مقارنة نوعين من البورسلين السيراميكي. البورسلين التجاري او التقليدي والذي يحتوي على 50% كاؤلين, 25% كوارتز, 25% فلدسبار. عوضت كمية الفلدسبار بمخلفات زجاج الصودا لايم لأنتاج تركيب جديد من البورسلين وحساب درجة انصهاه ثم حساب تأثير اضافة الزجاج على عملية حرق البورسلين.تم تحضير ثماني عينات من كل خلطة باضافة 8% من الماء ثم كبس المخلوط المركب بضغط مقداره 2 نيوتن للحصول على عينة قرصية بقطر 1,5 سم بعدها تم تلبيد العينات بدرجات حرارة (1000, 1100, 1200, 1250, 1300, 1350, 1400, 1450) مº لمدة ساعتين في فرن كهربائي. تم قياس المعاملات الفيزيائية مثل الكثافة, امتصاصية الماء, والتقلص. تم الاستنتاج ان عملية التلبيد والخصائص الفيزيائية قد تحسنت بالمعاملة الحرارية ,حيث اظهرت نتائج الحرق ان اضافة زجاج الصودا لايم بدل الفلدسبار قد خفض درجة انصهار البورسلين وان اضافة المسحوق المتخلف له تأثير ايجابي في ذوبان الكوارتز. الغرض من هذا العمل, هو استبدال 25% من الفلدسبار بمخلفات زجاج الصودا لايم في تركيب البورسلين القياسي ثم تقييم الاختلاف في الخصائص الفيزيائية بدرجات حرارية مختلفة.

Keywords

scrap glass --- new porcelain --- S.L.G


Article
Evaluation of the stress concentration of different incisal ridge preparations of porcelain veneers (Finite element analysis)

Author: Abbas F. Al-Huwaizi عباس فيصل الحويزي
Journal: Journal of baghdad college of dentistry مجلة كلية طب الاسنان بغداد ISSN: 16800087 Year: 2013 Volume: 25 Issue: 4 Pages: 1-4
Publisher: Baghdad University جامعة بغداد

Loading...
Loading...
Abstract

Background: Porcelain veneers are under a great deal of stress which may lead to clinical failure as fracture ordettachment. This study examined whether different finishing lines and lingual shoulder preparations in the incisalarea of the maxillary central incisor affect the bond of the porcelain veneers.Materials and methods: A two- dimensional finite element model was made. Location and magnitude of maximumVon Mises stresses were calculated in porcelain veneer. Six types of preparations were drawn as:incisal overlap of0.5mm, 1mm and 1.5mm depth and lingual shoulder, and incisal overlap of 0.5mm, 1mm and 1.5mm depth withoutshoulder preparation.Results: Stress formation is maximum in the incisal edge region. All the lingual shoulder preparations presented betterstress distribution than the non shoulder preparationsConclusion: Stress is distributed more evenly when the tested preparation possesses a good thickness of porcelainand the more the surface area with incisal overlap the less possibility of bond failure


Article
Cracking in the ceramic surface Technical and aesthetically
التصدع في السطح الخزفي تقنيا وجماليا

Author: Dr. Samer Ahmad م.د. سامر أحمد
Journal: Journal Of Babylon Center for Humanities Studies مجلة مركز بابل للدراسات الانسانية ISSN: 22272895 23130059 Year: 2015 Volume: 5 Issue: 2 Pages: 177-200
Publisher: Babylon University جامعة بابل

Loading...
Loading...
Abstract

This study included disclosure of the aesthetics of cracking through the technical data varied connotations , through the case of understanding the aesthetic associated with the mentality of a potter and by evidence that carry a variety of forms connotations and elevate the significance of the aesthetic to the level of nature abstract of the surface of the ceramic is also a cracking in the surface of ceramic system of signs that carry the variety gives indications of cracking nature Mch show signs of the foot and the researcher finds that the aesthetics of contemporary ceramics in cracking the case marks the transformation of scientific research in the technical and aesthetic associated Moundz ceramic .This study also included the production of glass Rift using local materials where the body of the potter made from Tine province of Babylon " MAHAWEEL " glass of local salt (NaCl) was drafted in accordance with the mixture of glass and base Seker by four blends ranging proportion of sodium chloride ( 23.7 % to 9.7 % ) with the use of lead oxide (Pb3O4) Ksahir complementary to the base Seker .Prototypes have been formed on a potter's wheel was burning by electric furnace and an electronic scale to measure the temperature , the glass plate using spray gun , the agenda was adopted to reach the desired temperature . The results of the Aaanat (1-2 ) with a cracked surface is very large and in the form of a network of minute cracks either at the level of the glass layer did not give good results because of the high proportion of sodium at the expense of either models lead (3-4 ) with cracks were less in terms of size cracking as well as the depth of the notch inside any cracking that increasing the ratio of sodium lead to increased network faults

شملت هذهِ الدراسة الكشف عن جماليات التصدع من خلال المعطيات التقنية المتنوعة الدلالات وذلك عبر حالة الفهم الجمالية المرتبطة بذهنية الخزاف ومن خلال الشواهد التي تحمل اشكال متنوعة الدلالات وترتقي هذهِ الدلالة الجمالية الى مستوى الطبيعة التجريدية للسطح الخزفي كما يشكل التصدع في السطح الخزفي منظومة من العلامات التي تحمل دلالات متنوعة وقد يعطي التصدع طبيعة ملمسية تظهر دلالات القدم ويجد الباحث ان جماليات التصدع في الخزف المعاصر يؤشر حالة التحول التقني في البحوث العلمية والجمالية المرتبطة بالمنجز الخزفي


Article
Preparation and Characterization of BeO-Supported Feldspar Porcelain
خصائص ومواصفات خزف الفلدسبار المدعم باوكسيد البريليوم

Author: Dunia K. M. Al-Nasrawy دنيا كامل مهدي النصراوي
Journal: Iraqi Journal of Science المجلة العراقية للعلوم ISSN: 00672904/23121637 Year: 2016 Volume: 57 Issue: 1B Pages: 404-416
Publisher: Baghdad University جامعة بغداد

Loading...
Loading...
Abstract

Due to the specific characteristic of porcelain, the insertion of Beryllium oxide has been studied. The basic materials and quantities were selected carefully. In this work, porcelain containing 32 wt% feldspar, 24 wt% quartz and 44 wt% clay was synthesized and beryllium oxide (BeO) (1 wt.%, 3 wt.%, 5 wt% and 7wt%) were add. The basic and new composition porcelain powders were uniaxially compacted into standard samples dimensions and fired at various sintering temperatures, 1100°C, 1300°C, and 1450°C then held for 2 hour in a furnace.The effects of sintering temperatures and beryllium oxide content on mechanical, electrical and structural properties were studied. The increasing of sintering temperature on the basic porcelain leads to an enhancement in bulk density and compressive strength. Basic porcelain which suffering lower sintering temperature (1300°C) introduces higher dielectric constant values in contrast with that suffering higher temperature (1450°C). The addition of BeO to the basic porcelain leads to decrease the bulk density and compressive strength. Porcelain with lower sintering temperature introduces higher έ values in contrast with higher temperature. The FTIR measurement show the existence of absorption at 800 cm-1 which attributable to Si-O-Si symmetrical stretching vibration band in all prepared samples. Band near 780 cm-l is attributed to the vibration of a beryllium atom moving in a tetrahedron of fixed oxygen atoms, while the absorption bands in the region 400-1500 cm-1 are due to the Be-O stretching and bending vibrations.

نظرا للاهمية الخاصة للخزف، تم دراسة تأثير اضافة اوكسيد البريليوم اليه. وقد تم اختيار المواد الأساسية والكميات بدقة. تم في هذا العمل تصنيع الخزف الذي يحتوي على 32٪ فلدسبار، 24٪ كوارتز و 44٪ من الطين وتم اضافة (1٪ ، 3٪ ، 5٪ و7٪) من أوكسيد البريليوم (BeO). وقد تم كبس مساحيق الخزف الأساسي و ذي المكونات الجديدة بطريقة الضغط الاحادي المحور للحصول على عينات قياسية الابعاد وتم حرق العينات بدرجات تلبيد مختلفة 1100م° ، 1300 م°، و1450 م° درجة مئوية لمدة ساعتين في الفرن. تمت دراسة تأثير درجات الحرارة ومحتوى أوكسيد البريليوم على الخواص الميكانيكية والكهربائية والهيكلية للخزف المصنع. لقد وجد ان زيادة درجة حرارة التلبيد للخزف الأساسي يؤدي إلى تحسين في الكثافة وقوة الانضغاط. الخزف الأساسي الذي عانى من درجة حرارة تلبيد أقل (1300 درجة مئوية) اعطى قيم ثابت عزل أعلى بالمقارنة مع تلك التي عانت من درجة حرارة تلبيد اعلى (1450 درجة مئوية). ان إضافة اوكسيد البريليوم إلى الخزف الأساسي أدى إلى تقليل الكثافة الظاهرية وقوة الانضغاط. الخزف الملبد بدرجة حرارة اقل أظهر قيم ثابت عزل έ اعلى بالمقارنة مع ارتفاع درجات الحرارة. أظهرت قياسات تحويلات فورير للاشعة تحت الحمراء في كل العينات المحضرة والملبدة حزمة امتصاص في 800 سم -1 والتي ترجع إلى حزمة اهتزاز الشد المتناظرة Si-O- Si. وتعزى الحزمة قرب 780 سم-1 إلى اهتزاز ذرة البريليوم المتحركة في رباعي الوجوه ذو ذرات الأوكسجين الثابتة الموقع، في حين أن حزم الامتصاص في المنطقة 400-1500 سم -1 تعود لاهتزاز الانحناء والشد لآصرة الـO- Be .


Article
Effect Of Industrial Pollution On Different Types Of High Voltage Insulators
تأثير التلوث الصناعي على انواع مختلفة للعوازل العالية الفولتية

Authors: Sabah S. Salih صباح صديم صالح --- Yaroub G. Jasim يعرب جاسم --- Arkan A. Hussein اركان احمد
Journal: Journal of Engineering and Sustainable Development مجلة الهندسة والتنمية المستدامة ISSN: 25200917 Year: 2011 Volume: 15 Issue: 1 Pages: 108-117
Publisher: Al-Mustansyriah University الجامعة المستنصرية

Loading...
Loading...
Abstract

High voltage insulators is essential part of the high voltage electric power transmission line . This paper investigate the electrical performance of two types of insulator (porcelain and silicon rubber) used in service and subjected to pollution condition from Baiji Refinery and thermal power station of Baiji for more than(10) years .The test data of flashover voltage measurements, surface resistance measurements and the insulators hydrophobicity are evaluated. The test result show that the silicon rubber insulator has a better performance compare with porcelain insulator.

عوازل الضغط العالي عنصر أساسي من مكونات خطوط الضغط العالي . هذا البحث تناول الخصائص الكهربائية لنوعين من العوازل ( البورسلين و مطاط السيلكون) مستخدمين في الخدمة ومعرضين إلى التلوث الصادر من مصفى بيجي و محطة بيجي الحرارية لأكثر من عشرة سنوات . النتائج المختبرية لقياس فولتية الشرر ، ومقاومة السطح ومقاومة العازل للماء تم حسابها . النتائج المختبرية أظهرت أن عوازل مطاط السيلكون لها الخصائص الأفضل مقارنة مع عوازل البورسلين .


Article
Assessment of Dewkhla kaoline,Um-Radhuma sand and domestic glass waste for the preparation of chemical porcelain
تقييم صلاحية كاؤولين دويخلة ورمال ام ارضمة ومخلفات الزجاج المنزلية لاغراض تحظير البورسلين الكيميائي

Loading...
Loading...
Abstract

Thirteen mixtures from natural raw materials (Dwekhla kaoline, um-radhuma sand) and synthetic waste glass were prepared to evaluate their suitability for preparation of chemical porcelain.The mixture were formed under 300 kg/cm2 using semi dry method, then the mixtures were fired at 1050, 1100,1150, 1200o C respectively.The result of physical (porosity, water absorption, bulk density, and specific gravity) chemical and mechanical properties at prepared samples showed an agreement with the American and russian specifications for chemical porcelain, as well as the results showed that waste glass was suitable as a flux material in preparation of chemical porcelain instead of feldspar.

ثلاثة عشر خلطة من اطيان كاؤولين دويلخة ورمال ام ارضمة ومخلفات الزجاج تم تشكيلها تحت ضغط 300 كغم/سم2 و بالطريقة شبه الجافة وحرقها بدرجات حرارة 1050م, 1100م, 1150,1200م, على التوالي باستخدام برنامج حرق خاص.اجريت الفحوصات الفيزيائية (المسامية و الامتصاصية والكثافة والوزن النوعي) والكيميائية والميكانيكية علة النماذج المحروقة وبينت النتائج فعالية مخلفات الزجاج كمادة مصهرة بديلة عن الفلدسبار مع مطابقة مواصفات المنتوج الى درجة كبيرة مع المواصفات العالمية لبورسلين الكيميائي

Listing 1 - 10 of 33 << page
of 4
>>
Sort by
Narrow your search

Resource type

article (33)


Language

English (20)

Arabic (11)

Arabic and English (2)


Year
From To Submit

2019 (2)

2018 (1)

2017 (5)

2016 (7)

2015 (3)

More...