The Effect of carbon quantum dots on the microhardness and the morphological characteristics of human dental enamel: in vitro study

Background: Nanoparticles have been widely used in dentistry due to their numerous physical and biological benefits. Carbon quantum dots (CQD) are used in many biological applications due to their small size and low cytotoxicity. It is expected to improve the surface properties of tooth enamel against acid dissolution when applied at low concentrations. The objective: This study evaluated the effect of CQD solution on the microhardness and surface characteristics of sound and demineralized enamel surfaces. Material and Methods: The solution was prepared with laser ablation and then examined with UV light (325 mm). The distribution, size, and dimensions of particles were analyzed using field emission scanning electron microscopes and transmission electron microscopes. Forty solid teeth (the first upper premolar) were prepared and divided into four groups (n=10). Group 1 (control group), Group 2 (Sound + CQD), Group 3 (Sound + CQD + Demineralization) and Group 3 (Sound+ Demineralization + CQD). The sample was immersed in the test solution for 4 minutes at 37 °C. The enamel microhardness was tested using Vickers microhardness testers, and the morphological characteristics were observed under a scanning electron microscope. Results: The CQD particles appear to be sphere-shaped with diameters of 2-10 nm and blue cyan light. After application of CQDs, the average microhardness value increased significantly (p<0.001) compared to the control group. Demineralized enamel (group 4) recorded a higher microhardness (p=0.006) than sound enamel (group 3) after CQD application. The treated surface was smooth and homogeneous, with a better crystal structure and closed pores than the untreated surface. Conclusion: The addition of CQDs had a profound effect on the sound surface hardness and demineralized enamel with enhanced morphological properties, which is considered an effective method for the prevention of dental disease.