Narrow Results

Fluoride (F) distributions in a synthesized hydroxyl apatite (HAp) block of uniform structure and in teeth were measured using in-air micro-PIGE (particle induced gamma-ray emission) and micro-PIXE system, which was developed at the Japan Atomic Energy Agency (JAEA) in Takasaki. We used a nuclear reaction ¹⁹F(p,αγ)¹⁶O to measure F density. The characteristic important feature of this technique is that it can measure F quantitatively in a microscopic area of the specimen placed in air. A surface of the HAp, the enamel buccal surface of a human molar, and a class V cavity wall in dentin were applied a sodium fluoride solution (NaF) four times and immersed in a normal saline solution. After one month, specimens were cut longitudinally. The F distributions were measured from the surface toward the inner part of the cut surface. The F penetration into specimens following NaF application was quantitatively configured in a two-dimensional mapping form. This method is quite useful for characterizing F distribution in a microscopic area of a tooth.

Fluoride (F) distribution in human teeth was measured using an in-air micro-PIGE and micro-PIXE system. Class V cavities in the extracted teeth were prepared with Fluoro-Bond Shake One to provide a thin layer of an F-releasing material (FRM). The cavities were then filled with Beautifil Flow F10 (FRM, Group I) or LITE FIL IIP (non-FRM, Group II). Following a four-year period, specimens were cut longitudinally perpendicular to the cavity floor. The F distribution was measured at the floor of the cut surface. The position including 90% of the intact Ca level was defined as the wall surface. Based on this demarcation, indices of F distribution (surface F concentration and F penetration depth) were determined. Thickness of FRM thin layers varied (≈339 μm) and did not affect F distribution. Both values of F distribution indices in Group I [821–8763 (mean 3797) ppm, 34–668 (mean 241) μm] were significantly larger than those in Group II [0–7064 (mean 1865) ppm, 0–143 (mean 21) μm]. The F distribution in Group I was affected more by the filling material than by the FRM thin layer during the four-year exposure. Methodologies using this system may give insightful information for the development of new dental materials.

Whether fluorine penetrated from material completely incorporates into tooth mineral is a matter of debate, although it is well known that the fluoride from material penetrates directly into tooth structures. The purpose of this study is to determine tooth-bound fluoride uptake from fluoride-containing materials using PIGE/PIXE system at the Wakasa Wan Energy Research Center. Class V cavities in buccal surfaces of eighteen extracted human teeth were drilled and filled with six fluoride-containing materials. After being stored in distilled water for one year, a longitudinal section including materials was obtained from each tooth. Fluorine and calcium distribution of specimens were evaluated using PIGE/PIXE system. After evaluation, the specimens were immersed in 10 mL of 1M KOH solution and were agitated at room temperature for 24 h to remove a KOH soluble fluoride. The specimens were washed with 200 mL distilled water and left to dry. Again, to estimate tooth-bound fluorine (KOH-insoluble fluoride) uptake, the same portion of the specimens after KOH treatment were evaluated using PIGE/PIXE system. It was confirmed that fluorine penetrated from material partly incorporated into tooth mineral. This tooth-bound fluoride have the potential to prevent dental caries after loss of the bond between the filling material and tooth structure.

Tooth pain, especially tooth thermal pain, is one of the most important symptoms and signs in dental clinic and daily life. As a special sensation, pain has been studied extensively in both clinic and experimental research aimed at reducing or eliminating the possible negative effects of pain. Unfortunately, the full underlying mechanism of pain is still unclear, because the pain could be influenced by many factors, including physiological, psychological, physical, chemical, and biological factors and so on. Besides, most studies on pain mechanisms in the literature are based on skin pain sensation and only few are based on tooth pain. In this paper, we present a comprehensive review on both neurophysiology of tooth pain mechanism, and corresponding thermal, mechanical, and thermomechanical behaviors of teeth. We also describe a multiscale modeling approach for quantifying tooth thermal pain by integrating the mathematic methods of engineering into the neuroscience. The mathematical model of tooth thermal pain will enable better understanding of thermal pain mechanism and optimization of existing diagnosis and treatment in dental clinic.