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Article
An evaluation of the effect of retention means on increasing the debonding strength of the denture acrylic teeth attached to the denture base resin

Author: Abbas F. Al-Huwaizi عباس فيصل الحويزي
Journal: Journal of baghdad college of dentistry مجلة كلية طب الاسنان بغداد ISSN: 16800087 Year: 2005 Volume: 17 Issue: 1 Pages: 14-17
Publisher: Baghdad University جامعة بغداد

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Abstract

Background: The debonding of acrylic teeth from the denture base is a challenging problem to the dentist and dental technician in which special means must be done to increase the debonding strength of the tooth.Material and method: Sixty specimens of acrylic central incisors were attached to acrylic rods and grouped into 5 groups according to the shape of the retention means placed at the tooth ridge lap. The specimens were strained under tension to examine their debonding strength.Results: The teeth with serrations (Group 2) have shown to be the most effective mean of increasing debonding strength, followed by the 2 longitudinal grooves (Group 4) where the difference between these groups was insignificant. Then followed by the teeth with 4 holes, and finally the difference between the teeth with a central groove and the control group were insignificant.Conclusions: It is recommended that the tooth ridge lap should be serrated with a fissure groove or placement of the 4 grooves to increase the debonding strength of the tooth.


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

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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
Assessment of the properties of locally produced impression compound

Authors: Nameer H. Al-Hashimi نمير الهاشمي --- Abbas F. Al-Huwaizi عباس فيصل الحويزي
Journal: Journal of baghdad college of dentistry مجلة كلية طب الاسنان بغداد ISSN: 16800087 Year: 2005 Volume: 17 Issue: 3 Pages: 23-26
Publisher: Baghdad University جامعة بغداد

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Abstract

Background: The goal of this study was the production of new type of impression compound that meets the ADA specifications along with being cheap and available in the local market.Materials and Methods: The basic ingredients were similar to those used by the commercially available products (Harvard, QD and Vevey). Specific properties were tested, like visual inspection, flow, reproduction of details, compatibility with stone, thermal expansion, and repeated use expiration.Results: The study proved that the new impression was within the limit of the American Dental Association specification No.3. (ADA No.3) (1), hence it could be used sufficiently.Conclusion: The use of the new impression compound for dental purpose is advised. Yet the reuse of the same product again and again is not advised because of the deterioration of the impression compound properties


Article
The Surface Hardness Measurement of Stone and Improved Die Stone After the Addition of a Mixture of Chemical Additives with Different Proportion

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Abstract

Background: Incorporation of chemical additives has long been a technique used to improve properties of the gypsum products. The purpose of this work was to study the effects of adding a combination of gum Arabic and calcium hydroxide to a type III dental stone and type IV improved die stone with different proportion. The effect on water/powder ratio, and surface hardness was determined.Material and method: Both material stone and die stone were blended with two proportion of additives so that each material was mixed twice but with different proportion of gum Arabic (0.1% and 0.2%) and calcium hydroxide (0.5 % and 0.3%). Data for hardness were subjected to two-way analysis of variance.Results: The results revealed that the chemical additives were reduced the water requirements of gypsum products so that the reduction of water lead to increase the density of mixture that sets harder. For type III dental stone the additives significantly improved the surface hardness, while for type IV improved die stone the surface hardness was not enhanced except it was designed to be mixed at low water/powder ratio, and in some instances a reduction in hardness was observed, especially at the most reduced water / powder ratio (0.18)

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