Title: Flexural Strength and Microhardness of a Zirconia Reinforced Lithium Silicate Glass Ceramic
Kyung Sunwoo (Presenter)
Alexander Hang, mwu
Allen Tang, mwu
Dustin Mueller, mwu
Qing Hong, Midwestern University
M. Teresa Pulido, Midwestern University
John Mitchell, Midwestern University
Objectives: Zirconia full crown restorations are a popular treatment option for posterior teeth among dentists. However, their clinical use is limited on the anterior region due to subpar esthetics. In this direction, a new type of ceramic is currently available in the market. Zirconia reinforced lithium silicate glass ceramic maintains the esthetic properties of lithium disilicate ceramics while reportedly increasing its mechanical properties due to the added zirconia. The purpose of this study is to measure and compare the flexural strength and microhardness of zirconia reinforced lithium silicate glass ceramic, Celtra Duoâ unfired (Dentsply Sirona, York, PA), to monolithic zirconia, ArgenZâ Esthetic Zirconia Disc, (Argen, San Diego, CA).
Methods: Bars of Celtra Duo (2.5mm×2.5mm×16mm) and Argen Z (25mm×2mm×4mm bars) were sectioned from blocks of the material using a Buehler IsoMet 500 Linear Precision Saw (Lake Bluff, IL). Samples (N=5) were tested for flexural strength using a 3-point bend test with an Instron (Electropuls 3000 Norwood, MA) with a crosshead speed of 0.5mm/min. The Argen Z material was treated in a furnace, the Celtra Duo was not. Blocks of 4x2x25 from both materials (N=5) were prepared for microhardness testing (Buehler WIlson VH1202 Lake Bluff, IL). Samples were embedded into epoxy and wet polished through 600 grit. Knoop values were obtained with a load of 1HV for Celtra Duo and 2HV for Argen Z with a dwell time of 10 seconds. An average of 9 indents were made per sample.
Results: Monolithic zirconia had a higher microhardness value with average of 1405.3 HV (4.3649) compared to zirconia reinforced lithium silicate glass ceramic with average of 698.7 HV (6.5464). Monolithic zirconia had a higher flexural strength with average of 1100.83 MPa (146.15) compared to zirconia reinforced lithium silicate glass ceramic with 256.56 Mpa (22.43)
Conclusions: Monolithic zirconia had twice the hardness and 4X greater flexural strength. It is still preferred when mechanical loading is high.