Arrest Dentine Caries in Vitro With Nondiscolouring Copper Tetraamine Fluoride

Objectives: To study the antimicrobial and remineralising properties of a nondiscolouring copper tetraamine fluoride (CTF) on artificial dentine caries.
Methods: The cytotoxicity of CTF was evaluated by human gingival fibroblasts (HGF-1) and stem cells from human exfoliated deciduous teeth (SHED). The antimicrobial property of Streptococcus mutans was evaluated by minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Totally 120 demineralised dentine blocks were divided into three groups and treated with CTF, Silver Diamine Fluoride (SDF) and water, respectively. After the cariogenic biofilm challenge, the effect of CTF on the morphology, viability, and growth kinetics of biofilm was determined using scanning electron microscopy, confocal laser scanning microscopy, and colony-forming unit (CFU) counting. The remineralising property of CTF was determined by the lesion depth, mineral loss, chemical structure, and full width at half maxima (FWHM) using micro-computed tomography, Fourier transform infrared, and X-ray diffraction, respectively. The discolouring property of CTF was assessed by spectrophotometry.
Results: The MIC and MBC of CTF against S. mutans were 320 ppm and 1280 ppm respectively. The IC50 of HGF-1 and SHED was 137±11 ppm and 195±16 ppm. Compared to the water group, the CTF group and SDF group had lower Log₁₀ CFU (p < 0.01), higher dead-live radio (p < 0.01), lower lesion depth (p < 0.001), lower mineral loss (p < 0.001), lower amide I-to-hydrogen phosphate (HPO₄^2-) ratio (p < 0.001) and lower FWHM (p < 0.01), whereas the CTF group and SDF group had similar results (p > 0.05). The colour change of the dentine blocks in the CTF group was smaller than that in the SDF group (p < 0.001) and was similar to that in the water group (p > 0.05).
Conclusions: The biocompatible CTF inhibits the growth of S. mutans and enhances the remineralisation of artificial dentine caries without discolouring effect.