Retentive strength at the zirconia implant abutment and titanium base interface with different surface treatments

Abstract

Screw-retained zirconia implant crowns with an internal titanium base have favorable mechanical properties compared to single piece zirconia implant crowns; however, they require adequate bonding between the zirconia crown and the titanium base. This study measures the retention between a titanium base and a full contour zirconia implant crown following different surface treatments of their bonded surfaces.

Full contour zirconia implant crowns were fabricated to fit a 3.5mm titanium base. The crowns were bonded to the titanium bases following 4 protocols (n=15): no surface treatment (Group 1), MDP-primer on the intaglio of crown and exterior of base (Group 2), alumina particle abrasion of the intaglio of crown and exterior of base (Group 3), and alumina particle abrasion and an MDP-primer on the intaglio of crown and exterior of base (Group 4). All crowns were bonded to the base with resin cement. Specimens were stored in water for 24 hours at 37°C and then thermocycled between 5°-55°C water for 15,000 cycles with a 15 second dwell time. Crowns were separated from the titanium bases using a universal testing machine. The four protocols were compared using a one-way ANOVA, followed by Tukey’s post-hoc tests (alpha=0.05). Sectioned specimens were examined with SEM.

Retention forces for Group 1 (737.8±148.9 N) and Group 2 (804.1 ±114.5 N) were significantly greater than Group 4 (595.5 ±122.2 N) which was significantly greater than Group 3 (428.2 ±93.8 N). Visual inspection of the debonded specimens showed that the majority of the cement remnants were seen on the external surface of the titanium bases. Microscopic examination of the interface between the crown and the unaltered base shows that the cement gap is approximately 13μm at the crest of the microgrooves and 50μm within the channel of the microgrooves. After particle abrasion, the microgrooves become significantly dulled and the cement gap increased to 27-40μm at the crest and 55-58μm in the channels.

Particle abrasion of titanium bases that contain retentive microgrooves prior to bonding is contraindicated. Application of a 10-MDP-primer demonstrated limited improvement in the retention of the zirconia implant crowns.