Bond strength of orthodontic buttons on clear aligner materials

ABSTRACT

Purpose

To evaluate the shear bond strength of orthodontic buttons bonded on various clear aligner materials using orthodontic plastic adhesive.

Materials and methods

Three types of thermoplastic materials: 1) Duran (Polyethylene terephthalate glycol), 2) Essix A+ (Polyethylene terephthalate glycol), and 3) Zendura (Polyurethane) were bonded with either metal or plastic buttons using orthodontic plastic adhesive (Bond aligner®). Six experimental groups with 15 specimens per group were prepared. Bond strength testing was done according to the Lap Shear Test Method (ASTM D3163) using the universal testing machine. Bond failure mode (modified from ASTM D5573) was examined with a stereoscope. Kruskal-Wallis and post hoc tests were used to analyse the differences in shear bond strength among the six groups.

Results

Mean bond strengths were as follows: 1) Duran-metal (DM) (7.04 MPa); 2) Duran-plastic (DP) (5.37 MPa); 3) Essix-metal (EM) (5.55 MPa); 4) Essix-plastic (EP) (4.62 MPa); 5) Zendura-metal (ZM) (1.17 MPa); and 6) Zendura-plastic (ZP) (1.40 MPa). Shear bond strength among the three thermoplastic materials were significantly different (p < .05). For the bond failure mode, regardless of button type, Duran and Essix A+ showed substrate failure of the thermoplastic sheet, while Zendura showed adhesive failure at the thermoplastic sheet interface.

Conclusion

Orthodontic buttons bonded on Duran and Essix A+ using orthodontic plastic adhesive could achieve very high bond strength that the thermoplastic sheets would tear before button detachment occurred. Buttons bonded to Zendura resulted in significantly greater bond failure rates.

KEYWORDS:

• Clear aligner
• bond aligner
• bond strength
• PETG
• polyurethane
• orthodontic plastic adhesive

Authors’ contributions

Natnicha Pariyatdulapak: conducting experiments, data collection, statistical analysis and writing of original draft. Pornkiat Churnjitapirom: Experimental supervision. Toemsak Srikhirin: Scientific final approval. Nita Viwattanatipa: conceptualization, methodology, research supervision, conducting experiments, writing final draft and final approval. All authors read and approved the final manuscript.

Acknowledgments

The authors would like to express our gratitude to the research division of Mahidol University for use of the experimental facilities. We would like to thank W & H company for donating the Zendura thermoplastic sheets used in our study. We are indebted to Assoc. Prof. Dr. Julalak Komoltri (Epidemiology Clinic, Faculty of Medicine, Siriraj Hospital) for her statistic guidance and Dr. Siew Peng Neoh for her expertise in language editing.

Availability of data and materials

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Disclosure statement

The authors declare that they have no competing interests.

Additional information

Funding

Faculty of Dentistry, Mahidol University