Evaluation of a newly developed calcium fluoride nanoparticles-containing orthodontic primer: An in-vitro study

Objectives: Fluoride and calcium ions have the ability to reduce the formation of white spot lesions (WSL) in enamel. This study aimed to develop a novel orthodontic primer that incorporates calcium fluoride nanoparticles (nCaF2) and investigate its cytotoxic and physical properties as this primer could enhance the remineralization process when used with the conventional acid etching technique. Materials and methods: Three groups of the newly introduced primers were prepared by adding and mixing nCaF2 (Nanoshell Company, USA at 5%, 10%, 20% in weight) to Transbond™ XT orthodontic primers (3M-Unitek, Monrovia, USA). X-Ray Diffraction (XRD) was performed to verify and evaluate the phase of the nanopowders. Field Emission Scanning Electron Microscope (FESEM) observation was used to assess the homogeneity of tested primers, and Energy Dispersive X-Ray Spectroscopy (EDS) was performed to analyze elements of the prepared samples. The three primer groups were compared to the control primer (without the addition of nCaF2) in terms of cytotoxic behavior, homogeneity, agglomeration, shear bond strength (SBS), and adhesive remnant index (ARI). Results: nCaF2 primers with all the prepared concentrations revealed good homogeneity with no apparent agglomeration after four months of mixing. Cytotoxicity of the new primers was higher than that of the control primer, but it was within the accepted limits of the ISO standards (70% cell viability). While the SBS and ARI values were comparable with the control primer (p > 0.05). Conclusions: The newly developed orthodontic primers with different concentrations of nCaF2 (5%, 10%, and 20%) showed a homogenous distribution of nCaF2 within the primers with no apparent agglomeration, acceptable cytotoxic level, adequate SBS, and ARI. Future clinical testing of nCaF2-containing orthodontic primer as a preventive measure for WSLs during fixed orthodontic treatment is suggested. © 2021 Elsevier Ltd