research centers


Search results: Found 2

Listing 1 - 2 of 2
Sort by

Article
The effects of drying techniques on the compr-essive strength of gypsum products

Authors: Radhwan H Hasan --- Kasim A Mohammad
Journal: Al-Rafidain Dental Journal مجلة الرافدين لطب الأسنان ISSN: 18121217 Year: 2005 Volume: 5 Issue: 1 Pages: 63-68
Publisher: Mosul University جامعة الموصل

Loading...
Loading...
Abstract

Excess water in set dental stone decreases its strength.So different methods were used to expel excess water but thecompressive strength may be affected by drying technique.The purpose of this study was to evaluate the compressive strengthof two types of set dental stone after air, conventionaloven and microwave drying techniques.A total of 60 stone specimens (30 specimens made fromSilky Rock stone and 30 Zeta stone) were prepared by the aidof an acrylic split mold according to ADA Specification No.25. Specimens were divided into six groups of 10 identicalspecimens for each. Then groups were either dried by air,conventional oven or microwave oven. Using UnconfinedCompression Machine, the specimens were loaded by a crosshead speed of 1 mm/minute till the specimen being fractured.The load required to fracture the stone specimens was recordedand analyzed using analysis of variance followed by Duncan’sMultiple Range Test for the statistical comparisons betweendrying techniques at a significance level of p< 0.05, andStudent’s t–test was used to compare between the two stonetypes.The results revealed that high significant differenceswere present between the different drying techniques(p<0.0001) with air dried specimens were significantly strongerthan others and microwave dried specimens were significantlystronger than conventional oven dried specimens. SilkyRock (type IV) stone was significantly stronger than Zeta(type III) stone (p<0.001).From this study, it could be concluded that the highestcompressive strength can be obtained by air drying of the stonefor 24 hours, while microwave drying technique give betterresults than conventional oven drying technique with theadvantage of time saving over the two other drying techniques.


Article
Evaluation of Some Properties of Iraqi Plaster by Using Some Additives and Microwave Drying Technique

Author: Dr. Areej Shehab Ahmad. (Lecturer), M.Sc. in Prosthodontics د. اريج شهاب احمد
Journal: MUSTANSIRIA DENTAL JOURNAL مجلة المستنصرية لطب الاسنان ISSN: 18138500 Year: 2015 Volume: 12 Issue: 1 Pages: 39-52
Publisher: Al-Mustansyriah University الجامعة المستنصرية

Loading...
Loading...
Abstract

Aims of this study:1- Evaluation of some properties of Iraqi plaster, compressivestrength & surface roughness. 2- Improving the quality of Iraqi plaster byincorporation of some additives. 3- Studying the effect of microwave drying onthe compressive strength & surface roughness of Iraqi plaster.Methods: 56 samples of Iraqi plaster used in this study, divided into two main groupsaccording to the main tests used, 28 samples for compressive strength & 28samples for surface roughness.Samples of each test were divided into two groups (each group 14 samples).The first group was without additives, while the second includes the modifiedgypsum products (Iraqi plaster) with additives, (Gum Arabic 0.5%, calcium oxide0.75%, and ferric oxide 0.2%).Samples of each subgroup are subdivided into two subgroups also according tothe drying method of Iraqi plaster, Open air drying method & Microwave dryingmethod (7 samples for each)Measuring of both tests was done in Technology University in Baghdad.Compressive strength measurement by using (unconfined compression machine),while, surface roughness of the samples was measured by Profilometer.Results: The results showed that incorporation of additives to Iraqi plaster result inchanging their evaluated properties & Comparing with open air drying method,microwave drying enhanced the properties tested in this study.Conclusions: incorporation of additives to Iraqi plasters result in (Improvement of thecompressive strength, reduction of the surface roughness and increasesmoothness).

Listing 1 - 2 of 2
Sort by
Narrow your search

Resource type

article (2)


Language

English (2)


Year
From To Submit

2015 (1)

2005 (1)