Effects of sterilization, conditioning, and thermal aging on the retention of zirconia hybrid abutments: A laboratory study.

ABSTRACT

OBJECTIVE: To investigate the effects of sterilization, conditioning method, and thermal aging on the retentive strength of two-piece zirconia abutments. MATERIALS AND METHODS: In total, 128 stock zirconia abutments were divided into four groups (n = 32) according to the conditioning parameters (A) air-abrasion using 50 µm alumina particles/1.0 bar, (B) 50 µm/2.0 bar, (C) 100 µm/1.0 bar, and (D) 100 µm/2.0 bar. All abutments were bonded onto titanium bases using DTK adhesive resin and stored in water bath (37°C) for 72 h. Each group was subdivided into two subgroups (n = 16), group 1 was disinfected, whereas group 2 followed disinfection and autoclave sterilization. Half of the specimens of each subgroup (n&#x02009;=&#x02009;8) was directly subjected to the axial retention test (groups N), while the other half was first subjected to 150&#x02009;days of thermocycling followed by retention test (groups T). Statistical analysis was performed with three-way ANOVA, additional statistical analysis was performed by using separate one-way ANOVAs followed by the Tukey's post-hoc test for post hoc pairwise comparisons among groups. RESULTS: The highest median retention strength was recorded for group B2N (1390 N), whereas the lowest strength was recorded for group C1T (688 N). No significant interaction (p ≥ 0.05) was detected between the different variables; conditioning method, sterilization, and the thermal cycling regarding the effect on the resulting retention. However, the sterilization always showed a positive effect. Thermocycling presented an adversely significant effect only in the absence of sterilization (p < 0.05), with the exception of subgroups A. For the sterilized groups, thermocycling had no statistically significant effect on the retention. CONCLUSION: Steam autoclaving increased the retention of hybrid zirconia abutments. DTK adhesive resin for two-piece zirconia abutments performed well after sterilization and thermocycling.