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Shear Bond Strength and Enamel Effects of Bioactive Composite Attachments for Clear Aligners
Thanachot Sirichamratsakul1, Wikanda Khemaleelakul1, Supassara Sirabanchongkran1
1Department of Orthodontics and Pediatric Dentistry, Faculty of Dentistry, Chiang Mai University, Chiang Mai, Thailand.
Background:
Attachments improve retention and facilitate complex tooth movement during clear aligner therapy. However, enamel demineralization and white spot lesions remain concerns, particularly in patients with poor oral hygiene. Fluoride-releasing materials help prevent white spot lesions, and bioactive composites, which release fluoride ions, show promise in preventing demineralization while maintaining strong mechanical properties. However, their application in clear aligner therapy remains underexplored. Therefore, this study investigated the shear bond strength (SBS) of three materials-Filtek Z350 XT Flowable (resin composite), Beautifil Injectable X (giomer), and Cention N (bioactive composite) used as attachments in clear aligner therapy under non-thermocycling (T0) and thermocycling (T1) conditions.
Material And Methods:
A total of 120 intact maxillary first premolars were randomly divided into three groups according to the material, with each further subdivided into T0 and T1 subgroups. The thermocycling protocol involved 1,000 cycles between 5°C and 55°C to simulate intraoral aging. SBS was tested using a universal testing machine, and failure modes were analyzed with the adhesive remnant index (ARI).
Results:
Cention N exhibited the highest SBS (29.783 ± 4.741 MPa), followed by Filtek Z350XT Flowable (23.834 ± 4.708 MPa), while Beautifil Injectable X had the lowest (15.332 ± 4.087 MPa). The SBS was slightly higher in the T0 subgroup than in the T1 subgroup, but the difference was not significant. ARI analysis showed that Cention N was more likely to cause cohesive enamel failure during attachment detachment.
Conclusions:
All three materials demonstrated adequate SBS for use as attachments in clear aligner therapy. However, material selection should consider both SBS and potential risks to enamel integrity. These findings provide valuable data for optimizing material choices in clear aligner therapy and highlight the need for further research to assess long-term performance.
