EVALUATION OF BIAXIAL FLEXURAL STRENGTH AND TRANSLUCENCY OF MULTICHROMATIC TRANSLUCENT ZIRCONIA AND LITHIUM DISILICATE CERAMICS

Abstract

INTRODUCTION: Full-contour (monolithic) zirconia restorations are gaining in popularity. High translucent zirconia materials and multilayered zirconia blocks might help to overcome the aesthetic drawbacks of traditional zirconia for fabrication of monolithic restorations OBJECTIVES: Were to evaluate the biaxial flexural strength and translucency of CAD/CAM: multichromatic ultra-translucent zirconia and comparing it with multichromatic high translucency Lithium Disilicate glass-ceramic. MATERIALS AND METHODS40 ceramic specimens were divided into two main groups; Group I: CAD/CAM multichromatic ultratranslucent Zirconia( UTML KATANA Zirconia) & Group II: Pressable multichromatic high translucent Lithium Disilicate glass-ceramic (e.max press multi). Each group was subdivided into two sub groups; sub group A: disc specimens (12mm diameter×1.5mm thickness) were fabricated (n=10) & thermocycled (500 cycles, 5°/55°C, 15 sec dwell time).Then, biaxial flexural strength was measured in MPa. Sub group B: rectangular specimens (12mm length × 10mm width × 1.5mm thickness) were fabricated (n=10). Spectrophotometric analysis was conducted to evaluate and compare the degree of translucency by translucency parameter (TP). Data were analyzed using student t-test & ANOVA with repeated measures test. RESULTS Statistical analysis of Biaxial flexural strength using student t-test revealed that group I (607.24 ± 71.79) showed higher statistically significant biaxial flexural strength values than group II (290.69 ± 41.19) ( p <0.001*). Results of translucency revealed that there were significant statistical differences between the two subgroups where IPS e.max Press Multi provided better translucency than UTML KATANA zirconia. CONCLUSIONS: Multi layered zirconia showed higher mechanical, but lower optical properties than lithium disilicate. The multi layered zirconia showed four layers with different light transmittance capabilities. It might therefore be useful for enhancing the aesthetic appearance of full-contour zirconia restorations made from this material in stress bearing areas.