Abstract
Introduction: Retention is a critical factor in the long-term success of cement-retained, implant-supported restorations. Insufficient retention may lead to prosthetic complications such as decementation, particularly in cases involving short abutments. Achieving adequate retention for abutments shorter than 4 mm is challenging because of the limited bonding surface. Various abutment design modifications have been proposed to enhance retention; however, comparative evidence on their effectiveness remains limited. This study aimed to evaluate the effect of different abutment design modifications on the retention of zirconia crowns cemented to short implant abutments.
Methods: Seventy-two implant abutments were digitally designed and divided into six groups (n=12). The control group had no modifications. Experimental groups included abutments with one axial wall removed, two opposing axial walls removed, an axial groove, a frustum-shaped groove, or a circumferential groove. Seventy-two zirconia crowns were fabricated using CAD/CAM technology and cemented with dual-cured resin cement under standardized laboratory conditions. Retention was measured using a pull-out test with a universal testing machine, recording the maximum force required to dislodge each crown.
Results: Mean retention values ranged from 155.93 N in the control group to 220.05 N in the circumferential groove group. Abutments with circumferential grooves and those with two opposing axial walls removed showed significantly higher retention than the control group (P<0.05).
Conclusions: Modifications to short abutment designs, particularly circumferential grooves and removal of opposing axial walls, significantly improved the retention of zirconia restorations, likely providing clinically relevant solutions for managing short implant abutments.