Evaluation of compatibility of different attachment types used in orthodontic clear aligners with electron microscopy

This study evaluated the compatibility between different orthodontic clear aligner materials and attachment designs using Scanning Electron Microscopy (SEM). The research aimed to measure gap distances between attachments and aligners to optimize tooth movements by minimizing compatibility problems. Fifty-six samples were divided into four groups: rectangular attachments with Duran+ aligners, rectangular attachments with Zendura FLX aligners, optimized attachments with Duran+ aligners, and optimized attachments with Zendura FLX aligners. Attachments were bonded to bovine incisors, aligners were thermoformed over them, and cross-sectional samples were analyzed using SEM at 250x magnification. Measurements were taken at seven points for rectangular attachments and five points for optimized attachments. Results showed that perfect adaptation was not achieved with any combination tested, with gaps ranging from 14.75±1.41μm to 91.07±3.11μm. Zendura FLX demonstrated significantly better adaptation than Duran+ with rectangular attachments (42.10±1.07μm vs 44.52±1.51μm, p<0.001). Optimized attachments showed better overall adaptation than rectangular attachments. All material-attachment combinations showed regional variation patterns, with largest gaps at gingival borders (67.18-91.07μm) and smallest gaps at flat buccal surfaces (14.75-20.98μm). These findings explain the clinical limitations in certain orthodontic movements and provide mechanical basis for improving aligner design and attachment selection in orthodontic treatment.