Study of the Diffusion of Tetracycline in the Dentin of the Human Tooth Ex Vivo

Currently, manufacturers of tetracycline and tetracycline antibiotics necessarily warn about possible side effects when using tetracycline in children under 8 years of age and pregnant women. When tetracycline is used in utero or after birth, before the teeth erupt through the gum during mineralization or calcification, the antibiotic binds to calcium ions, which causes persistent gray or brown stains or often streaks on the teeth. In the present study, the diffuse reflectance spectroscopy with an integrating sphere was used to determine the molecular diffusion coefficient of tetracycline in the dentin of a human tooth ex vivo, which was found as D = (6.49 ± 1.12) · 10–6 cm2/s. The dependences following from Fick’s second law and the modified Bouguer-Lambert-Beer law, as well as restrictions for the free diffusion model, were used in the calculations. It was found that when dentinal samples are saturated with tetracycline hydrochloride, the total transmittance decreases over the entire studied wavelength range from 200 to 800 nm. These studies are important for clinical practice.