Innovation Glass-Ceramic Spray Deposition Technology Improving the Adhesive Performance for Zirconium-Based Dental Restorations

Abstract

Glass-ceramic spray deposition (GCSD) is a novel technique for coating lithium disilicate (LD) glass-ceramics onto zirconia through simple tempering steps. GCSD has been proven to improve the bonding of zirconia to resin cement, but the effect of etching time on GCSD and the long-term durability of the bond achieved remain unknown. The effects of air abrasion with aluminum particles (ABB) and air abrasion (GAB) or etching with 5.0% hydrogen fluoride (HF) for 20, 60, 90, and 120 s (G20, G60, G90, and G120) on the resin cement–zirconia bond were studied. LD was included as a control (LDG). The microstructure, sub-micron roughness, wettability, and phase changes of samples were analyzed. After resin cement was bonded to zirconia, half of the samples were subjected to thermocycling (5000 cycles at 5–55 °C). The bond strengths of the samples were determined in shear bond strength (SBS) tests (n = 10 per group). An LD structure can be formed on zirconia after GCSD and proper etching processes, which result in high roughness and a hydrophilic nature. GCSD and HF etching significantly improved SBS, with G90 and G120 samples with pre- or post-thermocycling exhibiting SBS values comparable to those of LDG (p > 0.760). The surface characteristics of the LD layer are influenced by the etching time and affect the SBS of the bond of zirconia to resin cement. HF etching for 90–120 s after GCSD results in zirconia with SBS and bond durability comparable to LD.

The Effect of Surface Treatments on Zirconia Bond Strength and Durability

“…The GCSD technique could produce a layer of glass-ceramic coatings with a thickness of approximately 11.78 μm on zirconia surfaces [ 23 ]. Previous studies have proved the improved bond strengths of GCSD on zirconia after etching with 5% HF for 90–120 s [ 22 , 23 ]. Herein, we demonstrated that 3Y-TZP with GCSD showed comparable SBSs with LDGC before thermocycling ( Table 2 ), which is partly consistent with previously published data [ 22 ].…”

“…Previous studies have proved the improved bond strengths of GCSD on zirconia after etching with 5% HF for 90–120 s [ 22 , 23 ]. Herein, we demonstrated that 3Y-TZP with GCSD showed comparable SBSs with LDGC before thermocycling ( Table 2 ), which is partly consistent with previously published data [ 22 ]. Paradoxically, Kang et al [ 22 ] and Peng [ 23 ] reported that 3Y-TZP with GCSD showed higher SBSs than 3Y-TZP with APA using 50 μm Al 2 O 3 at 0.3 Mpa combined with MDP-containing primer (Z-Prime Plus).…”

“…The sintered 3Y-TZP disks were abraded using 50 μm Al 2 O 3 (Hager &Werken GmbH & Co. KG, Germany) for 15 s under a pressure of 0.1 MPa at a distance of 10 mm (3Y-TZP with APA) [ 16 ]. The 3Y-TZP disks were treated with the GCSD method in accordance with the previous studies [ 22 , 23 ]. GCSD (Biomic LiSi connector, Aidite, China) was used to deposit a thin glass-ceramic coating layer on the surface of 3Y-TZP disks at a distance of 10 mm and sintered afterwards.…”

“…A condensed silanols layer with the sol-gel method that is hydrolyzed from tetraethyl orthosilicate [ 17 ] is prone to cracks under thermal treatment [ 21 ], and coatings via silicon nitride hydrolysis or vapor-phase deposition technique are time-consuming or demand complicated equipment; hence, it is impractical for clinical application [ 19 , 20 ]. Recently, a novel glass ceramic spray deposition (GCSD) method has been reported to improve the zirconia bond strength combined with 5% HF etching for 90–120 s when compared with an APA application at a pressure of 0.3 Mpa combined with an MDP-containing primer [ 22 , 23 ]. By spraying glass-ceramic powders on zirconia surfaces that are then sintered, a thin coating layer can be established [ 23 ] without affecting the physical properties of the zirconia [ 22 ].…”

“…Recently, a novel glass ceramic spray deposition (GCSD) method has been reported to improve the zirconia bond strength combined with 5% HF etching for 90–120 s when compared with an APA application at a pressure of 0.3 Mpa combined with an MDP-containing primer [ 22 , 23 ]. By spraying glass-ceramic powders on zirconia surfaces that are then sintered, a thin coating layer can be established [ 23 ] without affecting the physical properties of the zirconia [ 22 ]. MDP-containing resin cement has been recommended for bonding to zirconia because it achieved a higher bond strength of zirconia than an MDP-containing primer did [ 24 ].…”