A novel digital method for evaluating attachment surface wear and failure in clear aligner treatment

Abstract

Background Structural alterations and adhesive or cohesive failures of attachments used in clear aligner therapy are factors that can significantly impact the clinical outcomes of orthodontic treatment. Quantitative methods capable of assessing such wear and failures are valuable tools in both research and clinical practice. Objectives This study aims to present a novel methodology that employs three-dimensional model superimposition and Boolean subtraction to rapidly and accurately evaluate surface wear and bonding failures in orthodontic attachments. Methods Three-dimensional models were obtained from patients undergoing clear aligner therapy at a private clinic, scanned at two different treatment stages. Using Meshmixer software, the models were imported and superimposed based on each tooth bearing an attachment. A cylindrical object was created and positioned on the buccal surface of the teeth with attachments, then duplicated. Using Boolean subtraction, the volumes of the attachments were subtracted from the cylindrical objects. The "stability" function was used to calculate the volume of each attachment, allowing comparison between the initial and final treatment stages. Results The proposed methodology effectively demonstrated that attachments undergo surface wear, as well as adhesive and cohesive failures. Anterior and lower teeth tended to show greater surface wear. One-quarter of the sample exhibited bonding failures (12% adhesive, 12% cohesive), with these failures occurring more frequently in posterior teeth. Both upper and lower arches showed a similar distribution of failures. Conclusions: The proposed method allows for a quantitative assessment of surface wear and adhesive or cohesive failures in attachments used during clear aligner therapy. Due to its simplicity and accessibility—using free software—it can be applied by both researchers and clinicians. Although the exact impact of attachment surface wear on aligner treatment outcomes remains uncertain, clinicians should be aware of its occurrence. Until further studies clarify this issue, careful monitoring of patients undergoing aligner therapy is strongly recommended.