Influence of Abutment Geometry on Zirconia Crown Retention: An In Vitro Study

<b>Background/Objectives</b>: This in vitro study investigated the retention of three different geometrical designs of short titanium base (Ti-base) abutments used in implant-supported zirconia crowns. The advent of digital technology has facilitated the integration of Ti-base abutments into implant dentistry by improving time efficiency, precision, and patient comfort. <b>Methods</b>: Three types of short Ti-base abutments were evaluated: Geo SRN multibase^® (Group A), Herilink^® (Group B), and TS Link^® (Group C), each with a height of 4 mm and gingival height of 1 mm (n = 20 per group). Zirconia crowns (LUXEN^® Smile S2, DentalMax, Republic of Korea) were modified for the testing setup and fabricated using CAD/CAM technology, then bonded to the abutments with RelyX^® Luting 2 resin-modified glass ionomer cement. Pull-out tests were conducted at a crosshead speed of 1 mm/min to assess retention. <b>Results</b>: One-way ANOVA and post hoc Tukey tests revealed significant differences in retention values among the different abutment shapes (<i>p</i> < 0.05). The mean retention forces were 194.65 N for Group A, 241.33 N for Group C, and 360.20 N for Group B. <b>Conclusions</b>: The geometrical design of Ti-base short abutments significantly affects the retention of CAD/CAM zirconia crowns, with hexagonal shapes (Group B) demonstrating superior retention. Clinically, selecting an abutment design with enhanced mechanical retention may improve the long-term success of implant-supported restorations.