Fluoride ion emission, shear bond strength, and adhesive remnant index of calcium fluoride nanoparticles-containing orthodontic primer: an In Vitro study
Abstract
Objectives
This study investigated fluoride ion emission, shear bond strength (SBS), and the adhesive remnant index (ARI) of orthodontic primers containing varying percentages of calcium fluoride nanoparticles (nCaF2).
Methods
Four primers were prepared with nCaF2 concentrations of 0%, 20%, 30%, and 40%, mixed with Transbond XT primer (3M-Unitek, Monrovia, USA). Twenty-eight extracted upper premolars were equally divided into four groups, and bonded with orthodontic brackets using the respective primers following a standardised protocol. Fluoride ion emission was measured daily for two weeks, followed by assessments of SBS and ARI.
Results
The mean fluoride ion released was significantly different between the four groups. All groups showed higher initial fluoride ion levels, which later stabilised. Notably, only the primers with 40% nCaF2 consistently released fluoride ions above 0.010 ppm, reaching 0.014 ppm on most days and stabilising between 0.011 and 0.026 ppm from Day 6 to Day 14. SBS differed significantly between the groups [F(3,24)=4.977,p=0.008], with the 40% nCaF2 group showing significantly reduced SBS, although not to a clinically significant extent. ARI was unaffected [χ 2(2, N = 28) = 3.589, p = 0.263].
Conclusions
Orthodontic primers with 40% nCaF2 maintained fluoride ion release levels that may be clinically effective in combating white spot lesions, without compromising the SBS and ARI.
© 2025 Nurin Afrina Syasya Azren, Sunittha Gopala Krishnan, May Nak Lau, Yasmin Kamarudin, Ghee Seong Lim, Nosizana Mohd Salleh, Ninie Suhana Abdul Manan, published by Australian Society of Orthodontists Inc.
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