Wear Resistance of Novel Machinable Glass Ceramics

Abstract: Objectives: In recent years, glass-ceramic blocks for CAD/CAM are clinically well accepted as “Single-Appointment Treatment” material. Conventionally, Feldspar glass ceramics have been frequently selected. Recently, it has been developed a Novel Lithium Disilicate Glass Ceramic which doesn’t require the crystallization process after CAD/CAM fabrication. The purpose of this study was to evaluate the wear resistance of machinable glass ceramic blocks.Methods: The wear resistance properties of a Novel Lithium Disilicate Glass Ceramic Block “Initial LiSi Block” (LS, GC Corp.) and 2 different Feldspar glass ceramic blocks of “GC Initial LRF BLOCK” (LRF, GC Europe N.V.) and “Block V” (BV) were compared by two-body wear test. Polished samples (Φ2.1mm) were prepared with diamond polishing paste “Cera Shine” (GC Corp.). They were set and contacted with hydroxyapatite as antagonist which sintered and polished with #4000 SiC paper in water. The wear test was performed with sliding on antagonist under a load of 0.3kgf with 10,000 cycles. Wear amounts were evaluated by measuring sample height (n=4) before and after wear test. In order to compare the crystal structure and the crystallinity, microscope observation with SEM (SU-70, HITACHI) and Reference Intensity Ratio method (RIR) with XRD (Empyrean, PANalytical) were carried out.Results: The averages of wear amount were LS 1μm, LRF 18μm and BV 39μm respectively and they showed significant difference in each other (p<0.01, One-way ANOVA and Turkey test). On the observation of SEM, the crystal type differences were seen between Lithium Disilicate and Feldspar. Moreover, the crystallinity of LS showed apparently higher than both LRF and BV. It was considered that the wear resistance property is influenced by both crystal type and crystallinity.Conclusions: It is considered that LS could be one of the most attractive “Single-Appointment Treatment Glass Ceramic Material”, because of its high wear resistance.