Long-term resin bonding to zirconia ceramic with a new universal primer

Abstract

Different surface conditioning, cleaning methods, and ceramic primers are used to improve bonding to zirconia ceramic. However, maintaining a durable bond with zirconia ceramic under various clinical conditions remains a challenge. This in vitro study investigated the durability of the bond strength of adhesive luting cement to zirconia ceramic after the application of a new universal primer. Ninety-six disks were fabricated from zirconia ceramic (e.max ZirCAD). Disks were conditioned either with airborne-particle abrasion with 110 μm Al(2)O(3) (AB) or silica-coated (SC). Thereafter, disks were cleaned either with oil-free air (A) or by ultrasonic cleaning (U) in alcohol. A conventional silane (S) (EspeSil) or a universal primer (P) (Monobond Plus) was applied to the conditioned surface. Six groups (n=16) were tested: SC-A-S; SC-U-S; SC-A-P; SC-U-P; AB-A-P, and AB-U-P. Transparent plastic tubes filled with composite resin were bonded to pretreated zirconia disks with adhesive luting cement (Multlink Automix). Each group was divided into 2 subgroups (n=8). Subgroups of 8 specimens each were either stored in 37°C water for 3 days without thermal cycling or in 37°C water for 150 days and exposed to 37,500 thermal cycles. Tensile bond strength (TBS) values were recorded with a universal testing machine. Statistical analyses were conducted with 3-way, 2-way, and 1-way ANOVAs and Tukey's HSD test (α=.05). Long-term water storage and thermal cycling produced significantly lower (P<.05) means (TBS) in MPa than 3 days storage in water for the following groups SC-A-S, (38.3 ± 9.7/11.3 ± 5.1); SC-U-S, (31.5 ± 8.5/4.8 ± 6.9), and AB-A-P, (42.5 ±7/21.7 ±6). However, long term water storage and thermal cycling did not decrease TBS for groups SC-A-P, (44 ±6.4/36 ±7.3; P = 0.6); SC-U-P, (45.2 ±4.7/38.1 ±6.2; P=0.8); and AB-U-P, (44.1 ±8.9/33 ±9; P=.2). A new universal primer provided significantly better long-term resin bonding to zirconia ceramic than a conventional silane. Cleaning methods had little effect on long-term resin bonding to zirconia ceramic.