Dissertation > Medicine, health > Oral Sciences > Oral orthotics > Repair correction of dental defects

Effect of Core: Dentin Thickness Ratio on the Fracture Load and the Colormasking of IPS E.max Press All-ceramic Crown

Author JinHaiLi
Tutor JiaJun; DengZaiXi
School Fourth Military Medical University
Course Stomatology
Keywords thickness ratio of core veneer IPS e.max Press all-ceramic crown sculpting apparatus for thickness fracture load making color translucency
CLC R783.3
Type Master's thesis
Year 2012
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All-ceramic materials exhibit outstanding esthetics,the nature oftranslucency, excellent biocompatibility,age resistance and corrosion resistance.the performance of strength and tinct of all-ceramic prosthesis are greatly ascendwith material science progressing, in recent years.With the improvement ofaesthetic requirement, more and more people choose all-ceramic prosthesis. But,because of the good transparency of porcelain, the color of allochromasia teethand metal post appeared in many case, so that the total effect is not artistic; Onthe other hand, under the effect of maximum bite force and daily masticatoryforce, all-ceramic prosthesis can’t exhibit a long-term effect in the clinicalpractice. So investigating the influence factors on the strength and color of IPSe.max Press all-ceramic prosthesis are meaningful for clinical practice.IPS e.max Press is a lithium disilicate glass-ceramic for the presstechnology. It’s one of the most commonly used core all-ceramic materials andflexural strength reaches400Mpa. The production process creates homogeneousingot in different translucency levels, the pressed, tooth-colored and highly esthetic. This study selected IPS e.max Press LTA2and IPS e.max Ceram A2,manufactureed dental crown shape specimen. Learning the effects of thethickness on the strength and color of IPS e.max Press all-ceramic prosthesis forclinical practice.The study included three parts:Part one: Development of an Adjustable Sculpting Apparatus for DentalCrown Shape SpecimenWith AUTO CAD software analyse, we developed the sculpting apparatus tocontrol the thickness for dental crown shape specimen. Three groups of waxspecimens (0.75mm1.00mm1.20mm)were made respectively. Incising the waxpattern from the occlusal surface and measuring the thickness of the occlusalsurfaces and axial wall random, and then evaluate the accuracy and reliability ofthe instrument with statisticsTo conclude based on results:The design of the sculpting apparatus wasrational and scientific, the result of measurement was accurate and reliable,specimen processing was repeatable, the practical size of occlusal surfacethickness and axial wall thickness were accord with the theory. The precision ofthe sculpting apparatus had satisfied experiment testing requirements of dentalrestoration materials.Part two: Effect of core: dentin thickness ratio on the fracture load ofIPS e.max Press all-ceramic crownProcessing IPS e.max Press all-ceramic crown test specimens by theadjustable sculpting spparatus for dental crown shape specimen. Tcore/Tveener=1:41:21:12:1and4:1(n=60). The total thickness was controlled to1.50mm.Occlusal surfaces of specimens applied load with Hertzian contact experimentalmethod. Measurements of specimens fracture load and Statistical analysis.Study the effects of the thickness on the strength of IPS e.max Press all-ceramicprosthesis for clinical practice.To conclude based on results:After fracture load tests of the IPS e.max Pressporcelain specimens, as the core: dentin thickness ratio increasing, the fractureload was on the increase. When thickness ratio increased from1:1to1:2, therehad the biggest growth of fracture load, but groups of1:1,2:1,4:1had notapparently change. So, In order to prolong the service life, the core: dentinthickness ratio must be least of1:1.Part three: Effect of core: dentin thickness ratio on the making color ofIPS e.max Press all-ceramic crownUsing the adjustable sculpting spparatus for dental crown shape specimenprocessed IPS e.max Press all-ceramic crown test specimens. The final thicknesswas controlled to1.50mm.T core/T veener=1:41:21:12:1and4:1(n=60). Thecolour parameters were measured with minolta colorimeter. Measurements ofchromatic aberration(△E) and statistical analysis.Study the effects of thethickness on the colormasking of IPS e.max Press all-ceramic prosthesis forclinical practice.To conclude based on results:As the core: dentin thickness ratio increasing,The colour parameters (L~*、a~*、b~*) of IPS e.max Press porcelain specimens hada little change and no statistical significance. But for aesthetic effects ofporcelains,there were an important influence of core materials. IPS e.max Pressporcelain had good translucency, normal tooth color, use it, otherwise not. If mustuse it,the thickness must be more than1.20mm.

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