Objective:
Evaluating a cold atmospheric plasma (CAP) device using ambient air for enamel pretreatment before bracket bonding and the impact on surface roughness.

Material and methods:
180 human third molars were assigned to 12 groups. After pretreatment with a) phosphoric acid+Transbond XT Primer (TXP), H₃PO₄, b) CAP (30 s)+TXP, CAP-30, c) CAP (60 s)+TXP, CAP-60, d) CAP+Transbond Plus self-etching primer (SEP-CAP) a metal bracket was bonded (Transbond XT adhesive). Shear bond strength (SBS) was tested after 1) 24 hours wet storage, 2) 500 thermal cycles (5°/55°C), 3) 90 days of wet storage with a universal testing machine. The adhesive remnant index (ARI) was determined. Additional specimens were fabricated, pretreated as groups a),b),d) before application of Transbond XT adhesive, removal with a tungsten bur and surface measurements before and after polishing with a profilometer.

Results:
After 24 hours, SBS in the H₃PO₄ and SEP-CAP group was higher than in both CAP groups (p<0.001). 500 thermal cycles reduced SBS in both CAP groups compared to 24 hours (p<0.001) and 90 days (CAP-30 p=0.001; CAP-60 p=0.008). In both CAP groups, an ARI of 0 was predominant. Surface roughness before polishing was higher in the CAP group.

Conclusions:
The use of CAP with air as working gas does not ensure sufficient SBS for clinical use, but in combination with SEP. Surface roughness was more impacted by CAP than H₃PO₄.

Clinical relevance:
H₃PO₄ etching is still considered the gold standard for bracket bonding. Further research is required to understand the effect of CAP to enamel.