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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

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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
A comparison between the arbitrary and kinematic intercondylar distances of full mouth rehabilitation patients (An in-vivo study)

Authors: Ma'an R. Zakaria معن رشيد زكريا --- Hussain F. Al-Huwaizi حسين فيصل الحويزي --- Widad A. Alnakkash وداد النقاش
Journal: Journal of baghdad college of dentistry مجلة كلية طب الاسنان بغداد ISSN: 16800087 Year: 2012 Volume: 24 Issue: special issue 1 Pages: 11-17
Publisher: Baghdad University جامعة بغداد

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Abstract

Background: The intercondylar distance can change the radius of movement and affect the arcs traveled by thecusps during lateral mandibular excursions in the horizontal plane. The aim of this study was to record and comparethe intercondylar distances of male and female patients requiring full mouth rehabilitation by using arbitrary andkinematic face-bows.Materials and methods: Interfacial widths of fifty asymptomatic male and female full mouth rehabilitation patientswere recovered from arbitrary and kinematic face-bows. Intercondylar distances were recorded and statisticallycompared.Results: Results indicated that arbitrary and kinematic intercondylar distances of male patients were significantlygreater than females indicating asymmetry in locating the condylar axes of rotation in both sexes.Conclusion: The majority of intercondylar distances of patients were more than 110 mm indicating that an articulatorwith an adjustable intercondylar distance would be more anatomically correct for the treatment of full mouthrehabilitation cases

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