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Article
The Effect of Microwave Disinfection on Tensile Strength of Dental Gypsum

Author: Radhwan H Hasan
Journal: Al-Rafidain Dental Journal مجلة الرافدين لطب الأسنان ISSN: 18121217 Year: 2008 Volume: 8 Issue: 2 Pages: 213-218
Publisher: Mosul University جامعة الموصل

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Abstract

Aims: To evaluate the effect of microwave disinfection on diametral tensile strength (DTS) of type IIIand type IV dental stones. Materials and Methods: A total of 80 cylindrical specimens was preparedwith dimensions 40 mm in height and 20 mm in diameter. These specimens were divided into 4 maingroups: Geastone type III, Zeta type III, Micromod type IV and Silky Rock type IV. Twenty specimensfor each main group were divided into 10 specimens as control subgroup and 10 specimens representingmicrowave irradiated subgroup. The microwave irradiation was performed in a household microwaveoven at 900 watts for 5 minutes. The DTS was conducted on a mechanical testing machine at across head speed of 1.0 mm/minute. The data were statistically analyzed using Student's t–test, analysisof variance and Duncan's Multiple Range test. Results: The microwave disinfection caused significantincrease in DTS (p < 0.05) for all types of dental stone, and dental stones type IV (Micromod and SilkyRock) had significantly higher DTS (p < 0.05) than dental stones type III (Geastone and Zeta). Conclusion:Microwave disinfection of gypsum cast cause significantly increase in diametral tensile strengthof type III and type IV dental stone.


Article
Shear Bond Strength of Hard Chairside Reline Material to Denture Base Material

Author: Radhwan H Hasan
Journal: Al-Rafidain Dental Journal مجلة الرافدين لطب الأسنان ISSN: 18121217 Year: 2009 Volume: 9 Issue: 2 Pages: 203-210
Publisher: Mosul University جامعة الموصل

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Abstract

Aims: To evaluate the effect of different surface treatment on shear bond strength (SBS) of a hard chairside
reline material to denture base resin. Materials and methods: Cylindric columns of denture reline material
were bonded to columns of denture base resin. Fifty specimens were prepared and divided into 5 groups
according to the surface treatment used. Group I: Untreated; group II: Wetting with denture base resin monomer
(180 s); group III: Wetting with Kooliner monomer (180 s); group IV: Wetting with acetone (10 s);
and group V: Wetting with chloroform (5 s). The strength at which the bond failed under shear was recorded
and fracture site on the specimens was tested by visual examination and reflecting light microscope. The
data were statistically analyzed using one–way analysis of variance (ANOVA), Duncan’s Multiple Range
Test and Chi–square test. Results: All surface treatments caused significantly increase (p < 0.0001) in SBS.
Chloroform caused significantly higher SBS, and untreated group showed significantly lower SBS. Mixed
failure mode was predominant in groups with higher SBS, while adhesive failure mode was predominant in
groups with lower SBS. Conclusions: All surface treatments (Monomer, Kooliner monomer, acetone, chloroform)
achieved significantly higher SBS.

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Article
Evaluation of some adhesive materials for repairing gypsum models

Author: Radhwan H Hasan
Journal: Al-Rafidain Dental Journal مجلة الرافدين لطب الأسنان ISSN: 18121217 Year: 2005 Volume: 5 Issue: 2 Pages: 185-191
Publisher: Mosul University جامعة الموصل

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Abstract

The aim of this study was to evaluate some adhesive materialsthat are used in dentistry for repairing of gypsum cast.The specimens were prepared with dimensions 121×16×10mm length, width and thickness, respectively. The total numberof specimens was 96 (48 specimens for dental plaster,while the other 48 specimens were for dental stone). The lengthof each specimen was measured and recorded on its surface,then the specimens were fractured into two pieces and reattachedtogether with one of the three adhesive materials, reattachmentwas done either immediately (time= 0) or after 4minutes of adhesive application. These specimens were dividedinto six groups for each gypsum product, which involved:Group 1: Control, unrepaired specimens; group 2: Polycarboxylatecement, time= 0; group 3: Polyacrylic acid solution,time= 0; group 4: Polyacrylic acid solution, time= 4 minutes;group 5: Cyanoacrylate adhesive, time= 0; group 6: Cyanoacrylateadhesive, time= 4 minutes. The length of each specimenwas measured again and differences in length for each repairedspecimen was measured. Then all specimens were subjectedto the flexure of transverse strength test. Data were analyzedusing analysis of variance and Duncan’s Multiple RangeTest.The results indicated that using of cyanoacrylate adhesive,time= 0 and polyacrylic acid solution, time = 4 minuteshad significantly higher transverse strength providing maximumadhesion for each gypsum product. The results of this studyalso showed that there were dimensional changes with polycarboxylatecement adhesive and such changes not observedwith cyanoacrylate and polyacrylic acid solution adhesives.


Article
Comparison of some physical properties of acrylic denture base material cured by water bath and microwave techniques

Author: Radhwan H Hasan
Journal: Al-Rafidain Dental Journal مجلة الرافدين لطب الأسنان ISSN: 18121217 Year: 2003 Volume: 3 Issue: 2 Pages: 143-147
Publisher: Mosul University جامعة الموصل

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Abstract

This study was designed to evaluate the physical properties (porosity and transverse strength) for microwave cured acrylic resin using new Iraqi microwavable flask. For transverse strength test, 20 acrylic samples were prepared with dimensions 65 × 10 + 0.03 × 2.5 mm. Ten samples were processed by conventional water bath technique, while the other 10 samples were prepared by microwave technique using new Iraqi microwavable flask. The transverse strength of the acrylic samples were measured by three–point bending test. For porosity test, 16 acrylic samples were prepared with dimensions 65 × 55 × 2.5 mm. Eight acrylic samples were processed by conventional water bath while the other 8 samples were processed by microwave technique using new Iraqi microwavable flask. Evaluation of porosity occurrence was done using microscope at 20× and 40× magnifications. The results of student’s t–test showed that there are no significant differences ( p > 0.05) in transverse strength for samples cured by water bath and microwave techniques while microscopical examination revealed that all acrylic samples which cured by both techniques were free from porosities. It was concluded that new Iraqi microwavable flask could be successfully used in curing of acrylic denture base material by microwave technique.


Article
Bond Strength Of Different Artificial Tooth Manufacturing To Microwave Cured Acrylic Denture Base

Authors: Radhwan H Hasan --- Nadira A Hatim
Journal: Al-Rafidain Dental Journal مجلة الرافدين لطب الأسنان ISSN: 18121217 Year: 2010 Volume: 10 Issue: 1 Pages: 8-16
Publisher: Mosul University جامعة الموصل

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Abstract

AIMS of this study are to investigate the bond strength and mode of failure of different tooth materials with and without surface treatment to acrylic resin denture base cured by microwave in relation to wa-ter bath techniques. MATERIALS AND METHODS: One hundred sixty samples of five different brands of acrylic teeth were divided into four groups (untreated and treated groups each of these were cured by water bath or microwave techniques). The bond strength between acrylic tooth and denture base resin was measured in shear mode by using unconfined compression machine. The shear bond strength (SBS) in MPa was calculated, debonded surfaces were examined using visual examination and reflecting light microscope . Analysis of variance (ANOVA) and Duncan’s multiple range tests were used for statistical analysis. RESULTS: there was a significant difference in bond strength of acrylic denture base to different tooth materials (P < 0.001). CONCLUSIONS: SBS of acrylic teeth treated by monomer surface treatment for 180 seconds to microwave cured resin was significantly higher than that of water – bath cured resin, and cross – linked acrylic teeth showed lowest SBS compared to other type of acrylic teeth.
Key words: Microwave, Bond strength, Cross – linked acrylic teeth.

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Article
Preparation of Metal Mold For Production Of Microwave Flask

Authors: Radhwan H Hasan --- Nadira A Hatim
Journal: Al-Rafidain Dental Journal مجلة الرافدين لطب الأسنان ISSN: 18121217 Year: 2009 Volume: 9 Issue: 2 Pages: 175-182
Publisher: Mosul University جامعة الموصل

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Abstract

Aims: To design and prepare a metal mold used for production of Fiber Reinforced plastic flask (FRP)
suitable for curing of acrylic resin by microwave irradiation, and investigate the effect of the following variables
on the shear bond strength (SBS) of acrylic teeth to acrylic denture base material: A-curing techniques
(water bath and microwave). B-surface treatment with monomer. C-cross – linking of the tooth resin
by using the new microwave flask. Materials and methods: The FRP flask is not available in our country
so as a special design of metal mold was prepared for this study. Inner dimensions were determined according
to standard Ash metal flask. A microwave flask was fabricated from unsaturated polyester resin reinforced
with glass fibers, nuts and screws was fabricated from Teflon material which are available in our
country. One hundred sixty samples of five different brands of acrylic teeth were divided into four groups
{untreated and treated (with monomer )groups each of these were cured by water bath or microwave techniques}.
The bond strength between acrylic tooth and denture base resin was measured in shear mode by
using unconfined compression machine, the SBS in MPa was calculated. Analysis of variance (ANOVA)
and Duncan’s multiple range test were used for statistical analysis. Results: There was a significant differences
in bond strength of acrylic denture base to different tooth materials by using FRP flask in relation to
Ash metal flask at (P < 0.001). Conclusions: SBS of acrylic teeth improved by monomer surface treatment
for 180 seconds to microwave cured resin by new prepared flask (FRP) was significantly higher than that of
water – bath cured resin, and cross – linked acrylic teeth showed lowest SBS compared to other type of
acrylic teeth.

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Article
Reinforced Microwave - Cured Acrylic Resin Denture Base Material with Glass Fibers

Authors: Mohammed A Abdulla --- Radhwan H. Hasan
Journal: Al-Rafidain Dental Journal مجلة الرافدين لطب الأسنان ISSN: 18121217 Year: 2010 Volume: 10 Issue: 2 Pages: 314-321
Publisher: Mosul University جامعة الموصل

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AIMS: To evaluation the Effect of adding glass fibers on the transverse strength and the levels of the residual monomer of specially formulated acrylic resin to be cured by microwave and heat cured acryl-ic resin denture base materials. MATERIALS AND METHODS: The materials were used in this study heat cured acrylic resin and microwave cured acrylic resin which is formulated to be cured by microwave energy( Acronacrylic resin). Thirty two samples were prepared for transverse strength test and divided into the following groups Control group (I) heat cured alone, group (II) microwave cured alone, the group (III) heat cured+fibers, group (IV) microwave cured+fibers the transverse strength was evaluated by using an Instron testing machine . Thirty two samples were prepared for residual mono-mer test and divided into four groups water bath and microwave cured with and without glass fibers, the residual monomer was evaluated by using ultraviolet visible spectrophotometer for seven days. RESULTS: Transverse strength test: Statistical Analysis of Variance(ANOVA) shows that there is significant differences at (p>0.0001)among the four groups and Duncan's multiple range test showed that microwave cured + fibers significantly higher transverse strength followed by heat cured +fibers, microwave alone, while heat alone shows significantly lowest transverse strength. Residual monomer test: Analysis of variance(ANOVA) for the four groups from the first day of immersion in water until 7th day shows that there are significant differences between the four groups in the all six days except the 7th day shows that there are no significant differences among the four groups for the level of the residual monomer. CONCLUSIONS: Microwave cured acrylic resin with glass fibers have signifi-cantly higher transverse strength than that of acrylic resin cured by water bath, also microwave cured acrylic resin have significantly lower residual monomer content from the 1st day of immersion when compared to that of water bath which show the same level of residual monomer at the 7th day of im-mersion


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

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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
The Effect of Thickness on The Color Parameters of The Vinyl Addition Maxillofacial Elastomer

Authors: Abdullah J. Mohammed --- Radhwan H. Hasan
Journal: Medical Journal of Babylon مجلة بابل الطبية ISSN: 1812156X 23126760 Year: 2014 Volume: 11 Issue: 3 Pages: 699-704
Publisher: Babylon University جامعة بابل

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Abstract

Aim of the study : The study investigated the effect of material thickness on color parameters of maxillofacial silicon . Materials and methods :sixty samples made of silicone rubber. Samples ( 20 * 10 * 3) mm length , width , thickness, and (20 * 10 * 1.5) mm length, width, and thickness were divided into three groups, white, yellow and pink ( 10 samples a thickness of 3 mm and 10 samples thickness of 1.5 mm in each group) . And then the samples were tested for recording color parameters .Results : There was a significant difference for the three color values at different thicknesses, where the value of * L and a * in the three groups decreased as thickness increased while the b * value rose up with the thickness . Conclusions: The increase in the thickness of the maxillofacial silicon associated with a decrease in the value of L * , a * and a rise in the value of b *.

أهداف الدراسةِ: تَحرّتْ الدراسةُ تأثيرَ سمك مادة مطاط السليكون الوجه الفكي والمستعملة في تعويض اجزاء الوجه والفكين المفقودة على مقاييسِ لونَ المادة لما له من تاثيرعلى جمالية الجزء المصنع واندماجه مع بقية اجزاءالوجه. المواد وطرائق العمل: ستون عينة صنعت مِنْ مطاطِ السيليكونِ الوجه فكي. 30 عينة تحمل الابعاد (20*10*3) مليمتر طول ، عرض، وسُمك،و 30 عينة اخرى بالابعاد(20*10*1.5) مليمتر طول ، عرض، وسُمك قسمتَ إلى ثلاث مجموعاتِ أبيضَ ، أصفرَ ووردي (10عينات بسمك 3ملم و10 عينات بسمك 1.5ملم في كُلّ مجموعة من الالوان الثلاثة). وبعد ذلك إختبرَت العينات لتَسجيل مقاييس اللونَ. النَتائِج: كان هناك اختلاف معنوي لقيم اللون الثلاثة عند اختلاف السمك حيث ارتفعت قيمة *Lوa* في المجموعاتِ الثلاث بانخفاض السمك بينما ارتفعت قيمة b*بارتفاع السمك. الاستنتاجات: الزيادة في سمك مادة مطاط السيليكون الوجه الفكي تترافق مع نقصان في قيمة L* وa* وارتفاع في قيمة b*.


Article
Antifungal Effect: Comparison of Commercial Denture Cleansers and Microwave Energy

Authors: Radhwan H Hasan --- Eman A Mustafa --- Nagham H Kassab
Journal: Al-Rafidain Dental Journal مجلة الرافدين لطب الأسنان ISSN: 18121217 Year: 2009 Volume: 9 Issue: 1 Pages: 24-31
Publisher: Mosul University جامعة الموصل

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Abstract

and comparing this with microwave sterilization technique on heat cured acrylic resin denture base
material which was cured by two different techniques. Materials and Methods: thirty two samples of
heat cured acrylic resin denture base material had been used, half of them was cured by conventional
water bath technique, and the other half by microwave technique. A simple method to measure Candida
biofilm activity using pH change of Stomastat. Modified Sabouraud broth developed and used to evaluate
the efficacy of the following denture cleansers: Chlorhexidine 0.2% and sodium hypochlorite
0.5%, and microwave sterilization on Candida albicans biofilm. The initial number of yeasts inoculated
was correlated with pH value of Stomastat after 24 hours incubation period. Results: The acrylic
resin samples that cured by conventional water bath technique were most effectively disinfected by
chlorhexidine 0.2%. This demonstrated by increasing the pH value of Stomastat significantly than the
control group. The same result was obtained with those samples which were cured by microwave oven.
The initial number of Candida albicans cells in Stomastat was significantly decreased than the control
group after treatment of acrylic samples with denture cleansers and microwave sterilization technique,
while for those samples that cured by microwave technique the least number was obtained after treatment
with chlorhexidine 0.2%. Conclusion: Both of chlorhexidine 0.2% and sodium hypochlorite
0.5% and microwave technique had the ability to disinfect acrylic samples that cured by water bath and
microwave techniques effectively. However, chlorhexidine 0.2% was the most effective one.

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