Comparative Analysis of Internal Tapered Implant- Abutment Connections: the Morse Effect

The purpose of the present study was to evaluate the Morse effect of different internal tapered implant-abutment connections (ITCs) using a pullout test. Implants with different ITCs were selected: Short (Bicon, USA), G1; Novo Colosso (Medens, Brazil), G2; Epkut (SIN, Brazil), G3; Strong SW (SIN, Brazil), G4; Flash (Conex & atilde;o, Brazil), G5 and Bone Level (Straumann, Switzerland), G6. The respective computer-aided design (CAD) files were loaded into the analysis software to measure each ITC's taper angle and implant-abutment contact area. Six implants from each group were embedded in acrylic resin blocks, and the respective universal abutments were fixed using a mallet (G1) or by applying 20 Ncm of torque (G2 to G6). After 10 minutes, each abutment's retention screw was removed, and the force necessary for abutment rupture was recorded using a universal testing machine at a crosshead speed of 0.5 mm/min. The groups were compared using a one-way analysis of variance and Tukey's test. Spearman's correlation was used to check the correlation of the taper angle and contacting area with the pullout strength. G1, a no-screw abutment with a 3 degrees taper, and G2, a 10 degrees tapered abutment tightened by 20 Ncm, presented the highest pullout strength (P P < .05). The increased taper angle of G4, compared to G3, reduced the Morse effect despite their similar implant-abutment contacting areas (P P < .05). The G5 and G6 abutments loosened after screw removal and did not exhibit pullout resistance. The closer the tapered angle (r =-.958) and the higher the implant-abutment contact area (r = .880), the higher the pullout strength (P P < .001). Within the limits of this study, the Morse effect is different among tapered implant-abutment connections. The closer the tapered angle and the higher the interface area, the higher the Morse effect between the abutment and the implant.