Research Information System
Thesis Type: Doctorate
Institution Of The Thesis: Gazi Üniversitesi, Sağlık Bilimleri Enstitüsü, Turkey
Approval Date: 2014
Student: BANU ÇUKURLUÖZ BAYINDIR
Supervisor: SEÇİL NEMLİ
Abstract:In dentistry, the most recent dental ceramic is yttria-stabilized zirconium oxide polycrystals (Y-TZP). Zirconia based restorations is used in both anterior and posterior regions of the mouth due to its superior mechanical properties. Due to optical opacity of these materials, zirconia cores are covered with veneering ceramics. The most cited mechanical complication with zirconia restorations is chipping of the veneer. With the recent advances in CAD/CAM technology and the techniques used for zirconia materials nonveneered monolithic zirconia restorations have become increasingly popular. Zirconia with increased translucency is expected to resolve problems related to veneering ceramic. The purpose of this study is to evaluate the effect of zirconia thickness on the degree of conversion of dual-cure resin cements used for cementation of zirconia. Materials and Methods: In this study, disk shaped ceramic specimens were prepared. Five ceramic groups including 2 mm thick monolithic zirconia, 1,5 mm thick monolithic zirconia, 1 mm thick monolithic zirconia, 1 mm zirconia substructure veneered with 1 mm ceramic, and 2 mm thick lithium disilicate ceramic prepared. The resin cements used in the study were Variolink II light-cure, Variolink II dual-cure, and Zirconite dual-cure resin cements. For degree of conversion test, resin cements were placed in the molds, ceramic disks were placed on the cements and polymerisation was activated using light source. Resin cement specimens (n=6) 0.07 mm in thickness and 14 mm in diameter were stored in the dark for 24 hours at room temperature before FTIR spectrometer was used for degree of conversion measurements. For microhardness test, resin cement specimens 0.07 mm in thickness and 14 mm in diameter (n=6) were prepared by curing under ceramic disks. Using 50 gf Vickers load with a dwell time of 10 s, microhardness values of the resin cement specimens were determined. Results were statisticaly evaluated. Results: In this study, FTIR analysis revealed that the highest degree of conversion was found for Zirconite dual cured resin cement polymerized under 1 mm monolithic zirconia samples followed by Variolink II dual cure resin cement and Variolink II light cure resin cement under same ceramic. Comparing microhardness of resin cements, zirconite dual cure polymerized under 2 mm zirconia veneered porcelain showed the highest microhardness value. Evaluation of top surface of resin cement, the highest microhardness value found for Variolink II light cure resin cement and zirconite dual cure resin cement which was poymerized under 1 mm monolithic zirconia. Comparision of top/bottom surface microhardness ratios of the groups, the best result was found for Zirconite dual cure resin cement under polymerized 2 mm monolithic zirconia.