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Article
Finite element stress analysis of endodontically treated teeth restored by prefabricated posts

Authors: Biland M. S. Shukri بلند شكري --- Walid N. Al-Hashimi وليد الهاشمي
Journal: Journal of baghdad college of dentistry مجلة كلية طب الاسنان بغداد ISSN: 16800087 Year: 2005 Volume: 17 Issue: 3 Pages: 27-32
Publisher: Baghdad University جامعة بغداد

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Abstract

Background: Endodontically treated teeth are restored by different types of posts. The study is to evaluate the stress distribution in endodontically treated teeth restored with prefabricated post: parallel (with different thread numbers and different materials) and tapered (with different coronal diameter and different materials).Materials and methods: The models are two-dimensional bucco-lingual section of maxillary central incisor with its supporting structure restored with parallel and tapered prefabricated post mad of two types of material, composite core and ceramic crown. A 100N force applied separately in three directions vertical, oblique and horizontal.Results: the maximum equivalent Von Mises stresses of all models subjected to vertical load are located within post material, while with oblique and horizontal loads are located at post surface on the labial side.Conclusion: Load directions and post materials have much greater effect than post designs on the stress distribution. The thickness of the dentin wall is directly proportional to the ability of the tooth to withstand the occlusal loads


Article
Assessment of Equivalent Grain Diameter for Soil Specific Surface Determination

Authors: Maysam Thamir Al-Hadidi --- Ahmed Abdul-Ezel Al-Mufty
Journal: Journal of Engineering مجلة الهندسة ISSN: 17264073 25203339 Year: 2005 Volume: 11 Issue: 2 Pages: 275-289
Publisher: Baghdad University جامعة بغداد

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Abstract

A procedure is presented to calculate an equivalent diameter for soil grains to be used to calculate the specific surface of the soil. The typical grain size distribution curve is expressed as a normal probability distribution cumulative curve and the frequency corresponding to the equivalent diameter is accordingly found. This frequency is adopted as the percent finer corresponding to the equivalent diameter. A relation is given for the calculation of the specific surface using the equivalent diameter. Grain size distribution curves of many soil samples are collected. A value for the specific surface of each soil is determined summing the surface area of subintervals in the distribution curve. The values of specific surface obtained from these gradation curves are compared to those calculated using the proposed values of the equivalent diameter for each soil. The results have shown good agreement for using the equivalent diameter that presented in this paper to determine the specific surface for soils instead of using the usual long procedure.

تم تقديم منهج عملي لحساب القطر المكافئ لذرات التربة لكي يتم استخدامها في حساب المساحة السطحية النوعية للتربة. وتم التعبير عن منحني التوزيع الحبيبي للتربة كمنحني احتمالات طبيعي متجمع و كذلك تم ايجاد التكرار المقابل للقطر المكافئ تبعا لذلك. وتم اعتماد هذا التكرار كمصحح مئوي مقابل للقطر المكافئ وقد اعطيت علاقة لحساب المساحة السطحية النوعية باستخدام القطر المكافئ.تم جمع بيانات لمنحني التوزيع الحبيبي للعديد من النماذج وتم تعيين قيمة المساحة السطحية النوعية لكل عينه بحساب المساحة السطحية للمسافات الثانوية في منحنى التوزيع. اجريت مقارنة لقيم المساحة السطحية النوعية التي تم الحصول عليها من منحنيات التوزيع الحبيبي هذه بتلك المحسوبة باستخدام القيم المقترحة للقطر المكافئ لكل عينة. وقد ظهرت نتائج جيدة لاستخدام القطر المكافئ المقدم في هذا البحث لحساب المساحة السطحية النوعية عوضا عن استخدام المنهج العملي الطويل المعتاد.

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