Bond strength enhancement for additively manufactured zirconia: Micro‐retentive design approach

AbstractPurposeTo investigate the effect of digitally designed micro‐retention features on the bond strength of additively manufactured (AM) zirconia copings.Materials and MethodsSixty titanium base abutments (NobelParallel, NobelBiocare), pretreated with 50 µm alumina particles were divided into four groups (n = 15 per group); one group with subtractively manufactured zirconia copings (SM), and three test groups comprising one group with AM zirconia copings without any intaglio surface modification (AM‐N), and two groups with digitally designed inverted pyramid‐shaped micro‐textures incorporated to the intaglio surface of the AM zirconia copings with two sizes: Ra 120 µm (AM‐120) and Ra 240 µm (AM‐240). All copings were bonded to the abutments using a conventional resin cement (Multilink Hybrid). Pull‐off tensile strength was measured with a universal testing machine (Instron), and statistical analysis was performed using analysis of variance and post‐hoc test.ResultsMean tensile strength values were 574.5 N for the SM group and 450.7 N, 990.8 N, 1097 N, for AM‐N, AM‐120, and AM‐240, respectively. No statistically significant difference was found between the SM and AM‐N groups (p > 0.05) or between the AM‐120 and AM‐240 groups (p > 0.05). However, the AM‐120 and AM‐240 groups demonstrated significantly higher tensile strength compared to the SM and AM‐N groups (p < 0.001).ConclusionProvision of inverted micro‐textured pyramidal shapes provided a simulation of etched surfaces to the intaglio surface of AM zirconia copings and significantly enhanced their retention strength to Ti‐base abutments compared to subtractive and non‐textured AM zirconia.