Objective: To analyse the surface wear of four materials used in the fabrication of Invisalign attachments as a function of simulated aligner wear in vitro.
Materials and methods: BracePaste Adhesive (American Orthodontics, Sheboygan, WI, USA), Filtek Supreme Ultra Flowable (3M ESPE, Seefeld, Germany), Tetric EvoFlow (Ivoclar Vivadent, Schaan, Liechtenstein) and Transbond XT Light Cure Adhesive (3M Unitek, Monrovia, CA, USA) were used to fabricate passive attachments on 32 typodont premolars. A total of 30 weeks of wear were simulated through repeated manual aligner placement and removal. Surface scans were taken at baseline (T0) and at five time points corresponding to 6, 12, 18, 24 and 30 weeks of simulated wear (T1, T2, T3, T4 and T5, respectively). The scans from each time point were superimposed onto the baseline scan taken prior to wear to quantify the dimensional changes at the surface of the attachments. Vickers hardness was also measured for each material.
Results: Upon statistical analysis using a generalised linear mixed model, significant differences in negative dimensional deviation, a variable associated with material loss, were found among the four materials; however, time was not found to be a significant factor in the observed negative dimensional deviation. Significant differences in Vickers hardness values were observed among the four materials (P < 0.0001), with each one recording a different hardness value from all the others investigated.
Conclusions: Although statistically significant differences were observed between the wear properties of the materials, each material appears to be suitable for use in the fabrication of Invisalign attachments under the conditions investigated.