Evaluation of the ceramic liner bonding effect between zirconia and lithium disilicate

Abstract

Statement of problemLittle information is available for the strength of bonding between zirconia and lithium disilicate as affected by surface pretreatment methods. PurposeThe purpose of this in vitro study was to investigate the shear bond strength (SBS) between zirconia core and lithium disilicate (LS2) veneered ceramic after surface pretreatments. Material and methodsFully sintered yttrium oxide partially stabilized tetragonal zirconia (Y-TZP) disk specimens were fabricated from zirconia ceramic materials. Specimens were divided into 4 groups with surface pretreatments applied (the as-received group, the liner group, the airborne-particle abrasion group, and the airborne-particle abrasion-plus-liner group). After pressing LS2 on a zirconia disk, shear force was applied perpendicular to the zirconia-LS2 interface. Data were analyzed using 2-way ANOVA and Tukey test (α=.05). For each group, the failure modes were measured by using optical microscopy, scanning electron microscopy, energy dispersive x-ray spectroscopy, and x-ray diffraction. ResultsAirborne-particle abrasion induced significantly lower interfacial strength between zirconia and lithium disilicate (P<.05). After airborne-particle abrasion of the surface, the increased monoclinic volume fraction and reduced coefficient of thermal expansion of zirconia may weaken the interfacial strength between zirconia and LS2. The liner treatment significantly improved the adhesion between zirconia core and veneering LS2 (P<.05). The SBS values decreased in the following order: liner group > airborne-particle abrasion-plus-liner group > airborne-particle abrasion group. The interfacial image of zirconia and LS2 showed a fusion of crystal structure between the 2 materials. Some components of the silica-containing glass-ceramic liner led to an increase in SBS as diffusion occurred on the zirconia surface. ConclusionsThe bond strength between zirconia and veneering LS2 was significantly increased by application of silica-containing glass-ceramic liner but was decreased with airborne-particle abrasion.