Shear bond strength of porcelain to milled and stereolithography additively manufactured zirconia with and without surface treatment: An in vitro study

Statement of problem. Delamination of veneering ceramic is one of the most common challenges relating to veneered zirconia restorations. Additive manufacturing (AM) is a fast-expanding technology that has gained widespread acceptance in dentistry and is increasingly being used to produce dental restorations. However, information about bonding of porcelain to AM zirconia is lacking. Purpose. The purpose of this in vitro study was to investigate the shear bond strength (SBS) of porcelain to milled and additively manufactured zirconia, and the effect of surface treatment on bond strength. Material and methods. A & Oslash;12x5-mm disk was designed virtually to fabricate all specimens, which were divided into 2 groups according to the manufacturing technique: additively manufactured or milled zirconia. The effect of airborne-particle abrasion and a zirconia liner before porcelain application was investigated in both groups. Veneering porcelain was fired into an alumina ring mold on the zirconia surface. SBS was measured by using a universal testing machine at a crosshead speed of 1 mm/min before and after aging (n=10). SBS data were analyzed with 3-way ANOVA (a=.05) Results. A significant difference was found between milled and AM zirconia. The SBS of porcelain to milled zirconia was significantly higher (1.38 MPa) than to AM zirconia (0.68 MPa) (P<.001). The surface treatment of zirconia had no significant effect on porcelain SBS in either group (P=.254), whereas thermocycling significantly reduced the SBS of porcelain to zirconia in both milled and AM groups (P=.001). Conclusions. Porcelain bonding to milled zirconia was better than to AM zirconia. Pretreating the zirconia substrate before porcelain application did not improve the porcelain bond. (J Prosthet Dent 2025;133:273-9)