Marginal gap of printed, milled, and heat-pressed two-piece polyetheretherketone abutments before and after thermal cycling, and their pull-off bond strength after thermal cycling.

Purpose: To evaluate the marginal gap of two-piece polyetheretherketone (PEEK) abutments fabricated with different methods, before and after thermal cycling, while also focusing on their pull-off bond strength.

Materials and methods: A two-piece abutment was virtually designed after digitizing a titanium-base (Ti-base) abutment. This design was used to fabricate printed (P-PEEK), milled (M-PEEK), and heat-pressed (HP-PEEK) PEEK abutments (n = 8). The marginal gaps of all abutments were evaluated under a stereomicroscope (15 points on each side, ×40 magnification), before and after thermal cycling (10,000 cycles, 5°C-55°C). Then, all abutments were subjected to a pull-off bond strength test. The marginal gap data were analyzed with a generalized linear model, while the pull-off bond strength data were analyzed with one-way analysis of variance and Tukey tests (α = 0.05).

Results: The marginal gaps were affected by the interaction between the fabrication method and aging condition, as well as by the fabrication method and aging condition (p ≤ 0.003). HP-PEEK abutments before thermal cycling had the lowest gap, whereas M-PEEK abutments after thermal cycling mostly had the highest (p ≤ 0.042). Thermal cycling increased the marginal gap of HP-PEEK (p < 0.001). M-PEEK had the lowest and HP-PEEK had the highest pull-off bond strength (p < 0.001). Most of the failures of P-PEEK and M-PEEK abutments were mixed.

Conclusions: The tested abutments had marginal gaps below the clinically acceptable threshold of 120 µm, both before and after thermal cycling. HP-PEEK abutments may be more resistant to dislodgment from the Ti-base abutments than P-PEEK and M-PEEK abutments.