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dc.contributor.advisorWaddell, John Neil
dc.contributor.advisorAl-Amleh, Basil
dc.contributor.advisorLyons, Karl
dc.contributor.advisorSwain, Michael
dc.contributor.authorMilmine, Hamish James
dc.date.available2014-10-23T21:43:21Z
dc.date.copyright2014
dc.identifier.citationMilmine, H. J. (2014). Effects of multiple firing on the physical properties of CAD/CAM produced lithium disilicate for dental restorations (Thesis, Doctor of Clinical Dentistry). University of Otago. Retrieved from http://hdl.handle.net/10523/5062en
dc.identifier.urihttp://hdl.handle.net/10523/5062
dc.description.abstractObjectives. To evaluate the effect of multiple thermal cycles on the physical and aesthetic properties of lithium disilicate CAD ceramic (IPS e.max CAD, Ivoclar Vivadent, Schaan, Liechtenstein). Methods. Experimental groups consisted of four test groups of crystallization firing plus one, three, five or seven “corrective” firings at the manufacturers recommended protocol of 820°C and a control “crystallization” group with one firing. Mechanical properties were analysed using the biaxial flexure strength method (n = 15) as per ISO6872 and scanning electron microscopy (SEM) was used to verify the origin of fracture (n = 1); fracture toughness change and hardness was determined by Vickers indentation method (n = 15). Physical crystalline phase change analysis was analysed with XRD (n = 1) (XPert PRO, Analytic, Almelo, Netherlands) and colour shift was quantified using a spectrophotometer (n = 5) (VITA Easyshade Compact, Vita GmbH, Bad Sackingen, Germany). Results. Mean biaxial flexure strengths and fracture toughness with standard deviations were: control 451(±57) (MPa) 1.60(±0.08) (MPa m1/2); +1 firing 390(±82) (MPa) 1.62(±0.09) (MPa m1/2); +3 firing 422(±125) (MPa) 1.63(±0.08) (MPa m1/2); +5 firing 417(±108) (MPa) 1.51(±0.24) (MPa m1/2); +7 firing 459(±106) (MPa) 1.53(±0.16) (MPa m1/2). XRD analysis showed lithium disilicate was the main crystal phase. Under all thermal conditions no further crystalline phases were identified. The colour of the specimens changed clinically significantly with increasing thermal cycles. Conclusion. There appears to be undesirable effects on strength, toughness and hardness due to thermal cycling IPS e.max CAD. There also appears to be a colour change effect as a result of increased numbers of firing cycles.
dc.format.mimetypeapplication/pdf
dc.publisherUniversity of Otago
dc.rightsAll items in OUR Archive are provided for private study and research purposes and are protected by copyright with all rights reserved unless otherwise indicated.
dc.subjectLithium disilicate
dc.subjecte.max
dc.subjectCAD/CAM
dc.subjectDental crown
dc.titleEffects of multiple firing on the physical properties of CAD/CAM produced lithium disilicate for dental restorations
dc.typeThesis
dc.date.updated2014-10-22T23:36:58Z
thesis.degree.disciplineOral Rehabilitation
thesis.degree.nameDoctor of Clinical Dentistry
thesis.degree.grantorUniversity of Otago
thesis.degree.levelDoctoral
otago.openaccessOpen
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