08. 2014年3月19日 18:59:56
: nJF6kGWndY
と思って検索してみたら過酸化水素水とフッ素、リン酸Ca（ハイドロキシアパタイト？）らしい 別に新しくないのではないか？ 随分、怪しくなってきたな
http://homepage2.nifty.com/nmc/
A Synthetic Enamel for Rapid Tooth Repair
Conventional treatment of tooth decay involves removal of the affected part of the
tooth followed by filling of the hole with a material such as resin or metal alloy1-4. This
method is less than optimal for microscopic early decay5,6 because some of the healthy
tooth must also be removed to enable fixing of the filling. Here we describe a new
dental paste that achieves rapid repair of early tooth decayThe outer layer of a human tooth is called the enamel. It is 1-1.5 mm thick and is
composed of hydroxyapatite (HAP) crystalsEarly tooth decay involves microscopic
damage to the enamel (holes <50 μm deep) by acid-forming bacteria, which cannot be
repaired by simple filling materials because perfect adhesion with the enamel does not
occur due to differences of chemical composition and structure. Our paste grows HAP
crystals, which are exactly like those in natural enamel, at the affected site within 15
min (for the method and examples of treatment, see supplementary information). Figure
1a shows a transmission electron microscopy (TEM) image of a lower premolar
repaired with our paste. The interface between the repaired layer and the enamel shows
no clear gap. The repaired layer contains elongated crystals (100-400 nm long and
20-80 nm wide) that are regularly orientated to the tooth surface and have grown across
the interface, showing that the paste has strongly bonded to the tooth enamel. Atomic
resolution TEM of a crystal (Fig. 1b) shows a pattern that is consistent with the known
lattice pattern of HAP: 0.688 nm for the short axis (c) of the crystal (arrow), and 0.817
nm for the long axis (a). Then X-ray photoelectron spectroscopy confirms that these are
fluoridated HAP crystals growing parallel to the tooth surface7. The repaired enamel
layer shows a high durability and acid tolerance (see supplementary information). For
comparison with treatment using acidic phosphate fluoride (APF) solution, an
alternative for the repair of early decay, look at Fig. 1c. The TEM image shows an
irregular layer8,9 of calcium fluoride less than 1 μm thick covering the enamel, with a
clear gap at the interface (arrow and dotted line)Time-lapse atomic force microscopy (AFM) showed that the apatite crystals of the
original tooth enamel (Fig. 1d) are slightly dissolved by application of the paste, but
quickly grow again using the paste as a source of minerals. This dissolution and
re-growth occur due to the strong acidity (pH<2) of the paste, and the result is a
continuous structure of new crystals extending from the original enamel to the repaired
layer. The new fluoridated HAP crystals cover the whole tooth surface in a densely
packed array after 3 min (Fig. 1e), and are stacked three-dimensionally after 15 min (Fig1f). The acidic paste contributes to rapid growth of the crystals by breaking down
calcium phosphate clusters, the growth unit of HAP, to liberate calcium and phosphate
ions as reported previously10,11We demonstrated that the paste can repair and prevent early decay by constructing
“synthetic enamel”. When used on patients, the paste should not be allowed to contact
the gums to prevent inflammation due to its acidity and high concentration of hydrogen
peroxide, although similar strengths are already used in dental clinics
Methods
The mother solution was prepared by mixing a 35 % H2O2 aqueous solution with
an 85 % solution of H3PO4 at a volume ratio of 4:1. The paste was made by adding 2 ml
of mother solution to 1.5 g of fluorized-apatite powder, which was prepared by mixing
1 g of Ca-deficient HAP powder (Ube Materials Co., Japan. Ca/P=1.64) with 100 ml of
200 mM NaF solution. The NaF solution with dissolved HAP was stirred for 1 h at
60°C, and the precipitate (F-HAP) was filtered, washed with pure water and dried at
110°C for 24 h. In the treatment, a tiny amount of mother solution was brushed on the
affected part, and the paste was quickly applied before the solution dried without any
mechanical removal. Within 15 min of treatment, approximately 20 μm thick of F-HAP
layer is constructed on the affected part. APF treatment was done with APF solution
(480 mM NaF, pH=3.5), which is commonly used in dental clinics, following the
treatment protocol. The durability was tested using a brushing machine and a
commercially available toothbrush and toothpaste at a speed of 150 rev./min, a load
force of 200 g, brushing amplitude of 30 mm, and 10000 times of brushing. The acid
tolerance was tested using acidic simulated saliva conformed to the British Standard
Specification for Safety Harnesses; it contained 77 mM NaCl, 4.0 mM KCl, 2.1 mM
Na2SO4, 7.5 mM NH4Cl, 3.3 mM urea, and 33 mM lactic acid with a pH of 4.5 adjusted
by NaOH at 25°C. The dissolution rates of the re-grown layer and enamel were
compared using laser scanning confocal microscopy
http://www.amanodental.com/apagard-renamel.htm |
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