Evaluation of implant restoration retention on various custom abutment materials and surfaces

Abstract

Purpose: Clinical use of cement-retained implant crowns requires selecting the appropriate abutment materials, surface characteristics, and cement type, based on finding the right balance between the desired level of retention form and the potential need for retrievability for each patient case. The purpose of this study was to evaluate the forces needed to vertically displace a cement-retained implant crown, using a provisional cement and five different combinations of abutment materials and surface characteristics. Material & Methods: A clinical master cast with an implant analog in the maxillary right central incisor site was fabricated and facilitated the design and manufacturing of 25 implant custom abutments planned for cement-retained restorations. Although all 25 implant custom abutments were designed to be identical in contour, each group of five abutments was fabricated from different materials or had different surface characteristics. The five different implant abutment groups were titanium smooth surface (Ts), titanium with retentive grooves (Tr), titanium with a nitride coating and smooth surface (Gs), titanium with a nitride coating and retentive grooves (Gr), and zirconia (Z). A total of 25 lithium disilicate crowns were fabricated and each crown was cemented to its corresponding abutment with non-eugenol temporary resin cement. With the use of a universal testing machine, the maximum tensile strength needed to dislodge the crown from the abutment was recorded and evaluated. Results: The mean tensile force needed to decement the lithium disilicate crowns within each implant abutment group was 31.58 N for titanium smooth surface (Ts), 29.29 N for titanium with retentive grooves (Tr), 32.90 N for titanium with nitride coating with smooth surface (Gs), 28.75 N for the titanium with nitride coating with retentive grooves (Gr), and 139.49 N for zirconia (Z). The titanium abutment groups did not differ significantly (P=.92); however, the zirconia abutment group required a statistically significant higher tensile force to decement the lithium disilicate crowns cemented with non-eugenol temporary resin cement compared to the titanium abutment groups (P<.05) Conclusion: Surface characteristics of the titanium implant abutments, including retentive grooves and nitride coating, did not increase the tensile force required to decement the crowns compared to a smooth titanium surface. The fabrication of zirconia abutments has the potential to generate discrepancies in the size and shape of the zirconia abutments, especially compared to the milled titanium abutments. The possible discrepencies in the zirconia abutments, including larger surface areas and need for nonstandardized crowns to fit the zirconia abutments may contribute more significantly to the increased retention compared to the interaction of the abutment material and provisional cement.