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Article
The influence of different pH of saliva and thermal cycling on the adaptation of different denture base materials

Authors: Yasir A. Hussein ياسر حسين --- Shatha S. Al-Ameer شذى الامير
Journal: Journal of baghdad college of dentistry مجلة كلية طب الاسنان بغداد ISSN: 16800087 Year: 2012 Volume: 24 Issue: 3 Pages: 47-53
Publisher: Baghdad University جامعة بغداد

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Abstract

Background: The difference in the adaptation of denture bases processed from heat cure acrylic, light cure acrylicand nylon materials and the effect of artificial accelerated aging (thermal cycling and pH) on the adaptation wasstudied.Materials and methods: One hundred eighty stone cast were prepared and assigned into 3 main groups accordingto the denture base material that processed on them(heat cure, light cure, nylon), each denture base and its castwas sectioned at posterior palatal border and the gap between the denture base and the cast was measured usingdigital microscope. Half of each group exposed to thermal cycling (2000 cycle) between (5 C-55 C ) 30 second ineach bath then the adaptation was evaluated again. All denture bases were stored in artificial saliva of different pH(5.7, 7,8.3) at 37 C for 30 days, then the adaptation was measured again.Results and discussions: The results showed that the adaptation of heat cure acrylic was better than light cure andnylon before and after aging process. The nylon showed the poorest adaptation. Thermal cycling decreases theadaptation of all denture bases. Variation of pH effected the adaptation of heat cure and light cure denture basesand did not affect the adaptation of nylon


Article
Effect of thermocycling on some mechanical properties of polyamide hypoallergenic denture base material (comparative study)

Authors: Azad M.R. Al-Muthaffer ازاد المظفر --- Shatha S. Al-Ameer شذى الامير
Journal: Journal of baghdad college of dentistry مجلة كلية طب الاسنان بغداد ISSN: 16800087 Year: 2012 Volume: 24 Issue: special issue 2 Pages: 25-30
Publisher: Baghdad University جامعة بغداد

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Abstract

Background: Hypoallergenic denture base material became recently the most attractive option due to their use asalternative to poly methyl methacrylate in hypersensitive patients. The study of the effects of thermocycling on themechanical properties is very important, as it is beneficial for clinical purposes.Materials and methods: One hundred and sixty specimens were prepared according to manufacturer's instructionsand they were divided into two groups: Valplast and Vertex as a control group (eighty specimens for each), twentyspecimens from each material were used to test each of property. They were either thermocycled or notthermocycled (n = 10).Results: There was significant difference between polyamide and conventional heat cured acrylic in the four testedproperties. Furthermore, thermocycling significantly decreased the flexural strength of both polyamide and the heatcured acrylic and it significantly increased the tensile strength and hardness of both tested materials. Thermocyclingdid not significantly affect the impact strength of both materials.Conclusions: Vertex showed higher values of flexural strength than Valplast, flexural strength of both materialsdecreased post-thermocycling. Although the flexural strength of valplast was relatively low, it demonstrated greaterimpact strength than Vertex, impact strength of both tested materials was not affected by thermocycling. The tensilestrength of Vertex was more than Valplast, for both materials tensile strength increased after thermocycling. Thehardness of Vertex was higher than that of Valplast, both materials' hardness increased after thermocycling

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