Effects of sterilization, conditioning, and thermal aging on the retention of zirconia hybrid abutments

The objective of this study was to assess the impact of sterilisation, conditioning methods, and thermal ageing on the retention strength of two-piece zirconia abutments.

A total of 128 stock zirconia abutments were divided into 4 groups, each including 32 abutments. The groups were categorized based on the conditioning parameters used: Air-abrasion with (A) 50 µm alumina particles at 1.0 bar pressure, (B) 50 µm particles at 2.0 bar pressure, (C) 100 µm particles at 1.0 bar pressure, and (D) 100 µm particles at 2.0 bar pressure. All abutments were bonded to titanium bases using DTK adhesive resin and stored in a water bath at a temperature of 37°C for a duration of 72 hours.

The groups were divided into two subgroups (n=16) each. Group 1 was disinfected, while Group 2 underwent both disinfection and autoclave sterilisation. Half of the specimens from each grouping (n=8) were directly submitted to the axial retention test (group N), whereas the remaining half underwent 150 days of thermocycling before the retention test (group T).

The data was subjected to statistical analysis using a three-way analysis of variance (ANOVA) followed by Tukey's post-hoc tests.

Group that was air-abraded with 50 µm alumina particles at 2 bar pressure, subjected to sterilization, but not exposed to thermal cycling (group B2N) exhibited the highest median retention strength of 1390 N, whereas group that was air-abraded with 110 µm alumina particles at 1 bar pressure, not sterilized, but subjected to thermal aging for 150 days ( group C1T) had the lowest strength of 688 N. No statistically significant interaction (p>0.05) was seen between the different variables in relation to their impact on the resulting retention.

However, the sterilization always showed a positive effect. Thermocycling had a substantial negative effect only when sterilisation was not performed (p≤0.01). Thermocycling did not have a statistically significant impact on the retention of the sterilized groups. For the sterilized groups, thermocycling had no statistically significant effect on the retention.

In conclusion, our findings indicate that steam autoclaving significantly enhanced the retention of hybrid zirconia abutments. The DTK adhesive resin demonstrated excellent performance during sterilisation and thermocycling when used with two-piece zirconia abutments.

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