Analysis of tooth-bound fluoride after the application of coating materials on the enamel surface with an in-air micro PIXE/PIGE

Abstract

Tooth-bound (KOH-insoluble) fluoride prevents caries via long retention within the tooth structure. Tooth-bound fluoride in the enamel was investigated after applying various fluoride-containing tooth-coating materials using an in-air micro [Formula: see text] PIXE/PIGE system. Three different fluoride-containing or a non-fluoride containing coating materials were applied to the coronal enamel surface of 24 extracted human molars. The samples were stored in water for 1 or 7 days and then sectioned into two slices. One slice was immersed in 1M KOH solution for 24 h for KOH-insoluble fluoride (KOH(T)) analysis. The second slice was not subjected to KOH treatment and was used to analyze the whole fluoride (KOH-soluble plus insoluble fluoride: KOH(U)). Fluorine and calcium distribution were measured in all the slices with [Formula: see text]PIXE/PIGE. KOH(U) was higher than KOH(T) on some materials, especially those that released more fluoride. For KOH(T), there was no significant difference among all fluoride-containing materials in the 7-day group. However, there were significant differences in the KOH(U) samples during the same period. PIXE/PIGE analysis confirmed the presence of tooth-bound fluoride in the enamel adjacent to the fluoride-containing coating materials. The amount of tooth-bound fluoride depended on the type of material.

Fluoride Retention in Root Dentin following Surface Coating Material Application

“…We measured the T-F converted from material-released fluoride using an in-air µ PIXE/PIGE. Most previous studies [ 8 , 9 , 23 , 24 , 25 ] have demonstrated that T-F can be measured on dissolved enamel or dentin after KOH treatment [ 8 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ]. However, the KOH treated teeth were dissolved in HCl or HClO 4 , so the whole or part of the specimen was destroyed.…”

“…The fluoride and calcium distribution in the specimens were evaluated using an in-air µPIXE/PIGE system at the Wakasa Wan Energy Research Center, as previously described [ 22 , 23 , 35 ]. Briefly, a 2.5-MeV proton beam was extracted through a thin silicon nitride window into air and used to irradiate a sample mounted on a sample stage set in air.…”

“…Komatsu et al [ 22 ] measured and analyzed the T-F distribution in the enamel at the cavity wall and dentin at the cavity floor from restorative (filling) materials, and Okuyama et al [ 23 ] reported the distribution of T-F, which is derived from the tooth-coating materials on the enamel surface, using an in-air micro-particle-induced X-ray/gamma emission (in-air µPIXE/PIGE) system. The PIXE/PIGE system is one of the methods used to detect the distribution of elements on a surface.…”