Potential effect of airborne-particle abrasion (APA) on stainless steel and ceramic bracket base volume

Abstract

Background: Bracket failure due to loss of adhesion is common and influences treatment time and patient comfort in orthodontic practice. This pilot study is focused on a widely used adjunctive method for bracket recycling -Airborne-Particle Abrasion (APA) and its impact on the retentive mesh pad volume and surface area in two types of brackets.

Objectivities: To explore potential loss of retention volume on stainless steel and ceramic bracket bases after aluminium oxide Airborne-Particle Abrasion (APA) and limitations of the methods used in this pilot study.

Material and methods: Four stainless-steel and four ceramic brackets were bonded on extracted human teeth and debonded according to manufactures instructions. Sandblasting with an Airborne-Particle-Abrasion (APA) method using 5 bar pressure was performed using particles of 25- and 50-μm diameter aluminium-oxide with a distance between bracket-base and tip of the micro-etcher of 5 and 10 mm during 10 seconds. A Micro-CT scan of all brackets was completed before and after sandblasting to evaluate potential changes in retention volume. Loss of retention volume and adhesive substance was assessed in a qualitative and a quantitative ways. Results: None of the test combinations managed to completely remove adhesive material. Loss of retention volume was registered in all brackets. Ten mm distance and 50 µm abrasive powder appeared in this study setting as the most beneficial combination in reducing the adhesive substance and a 5 mm distance in combination with 50 µm abrasive powder seemed to have the highest attrition impact. Loss of mesh pad volume due to ASA showed similar results on SS- and CE brackets. Lack of appropriate standardization in bonding/debonding and sandblasting procedures clearly biased the results. Conclusion: Micro- CT could be a useful tool to study volume loss of the bracket bases. However, results show that the methods used to prepare brackets for sandblasting and sandblasting protocol should be improved to answer the research questions posed in this study.