Photon Factory Activity Report 2016 #34 (2017)

BL-9A/2016Y032

Analysis of silver compounds in reaction products of silver diamine fluoride, an anticaries agent, with bovine tooth
Noriko Hiraishi*1, Takahiro Wada1, Ken'ichi Kimijima2,
Masao kimura2, 3, Motohiro Uo1, Junji Tagami1
1.
Tokyo Medical and Dental University, 113 -8549, Japan,
2.
Photon Factory, Institute of Materials Structure Science, High Energy Accelerator ResearchOrganization, 305-0801, Japan,
3.
School of High Energy Accelerator Science, SOKENDAI, 305-0801 Japan
1 Introduction
Silver compounds have a long history of use because of
their potent antimicrobial properties. In dentistry, silver
diamine fluoride (SDF) is a topical fluoride solution thathas been used for caries prevention and treatment. The
38% SDF solution was developed in Japan and approved
for use as a therapeutic agent in the 1960s. More recently,
the US Food and Drug Administration (FDA) admitted its
safety and effectiveness to meet FDA's requirements formarketing approval. The application of SDF is indicatedto arrest caries of the primary teeth in children andprevent root caries in elderly people. However, the main
disadvantage of SDF is discoloration of teeth surface.
A number of clinical studies have demonstrated that
SDF is effective in reducing carious lesions [1]. In vitro
studies reported that SDF increases the mineral density of
the carious lesion and that SDF hardens teeth surface due
to formation of highly mineralized zone [2]. The
antibacterial effect was sufficient enough to inhibit
cariogenic biofilm formation [3]. However, only a limited
number of publications have reported on the mode ofaction of SDF on mineralized tissue and on silver
compounds that cause teeth-discoloration. When SDF
reacted with hydroxyapatite in teeth, it is believed thatCaF2 and Ag3PO4 are readily formed, which wasconfirmed by means of energy-dispersive X-ray analysis
and X-ray diffraction. In this study, we investigated on
silver salts formation when SDF reacts with teeth
component (enamel, dentin and collagen type I) by XAFS
measurements
2 Experiment
Bovine enamel and dentin were pulverized under liquid
nitrogen in a cryogenic mill into fine particles withdiameters less than 75 μm. Collagen Type I from bovine
achilles tendon was also used as substrate. The 0.05 g ofbovine enamel, dentin and collagen powder was treatedwith the 0.1 ml of 38% SDF solution (55000 ppm fluorideherein). After 3 min reaction time, the powder samples
were washed with DW three times and centrifuged. The
deposit of sample powder was kept at 37°C for 7 days
with ambient light exposure. The XAFS measurements
were carried out on these powder samples with He filled
sample chamber at BL-9A beamline. The Ag L3-edge
XANES spectra were measured by the fluorescence yield
method using a Lytle detector and scanned for the spectral
range of 3.32 keV - 4.42 keV. The spectra of metallic
silver and silver compounds such as Ag3PO4, Ag2O, AgO,Ag2S, AgF, AgI and AgNO3 were measured to compare
those of SDF-reacted samples.
3 Results and Discussion
Figure shows XANES spectra of (a) SDF-treatedenamel, (b) SDF Figure -treated dentin, (c) SDF-treatedcollagen type I and (d) SDF without substrate. When
compared with references (metallic silver and other silver
compounds), these spectra are differed from those ofreferences (references spectra not shown). This indicatesthat SDF does not give a positive reaction with enamel,dentin or collagen Type I.
In this study, we did not use artificial saliva during SDF
reaction. Since SDF is alkaline, minerals in teeth are not2+32dissolved or not release Ca , PO4 and HPO4 . Therefore,
SDF is unlikely to react teeth components. For a further
2+study, we should use artificial saliva that includes Ca
22+2and HPO4 . The high concentration of Ca and HPO4 insaliva should be responsible to form SDF-salts.

Figure Ag L3-edge XANES spectra of (a)SDF-treated enamel,(b) SDF-treated dentin, (c) SDF-treated collagen type I, and (d)SDF without substrate.

Acknowledgement
This work was supported by Grant-in Aid from the Japan
Society for the Promotion of Science (JSPS No.
25462951) and Grant-in-Aid for JSPS Fellows.
References[1] Chu CH et al. J Dent Res. 81(11):767–770, 2002.
[2] Mei ML et al. Med Oral Patol Oral Cir Bucal.
18(6):824–831, 2003
[3] Chu CH et al. J Dent. 36(6):387–391, 2008
* hiraope@tmd.ac.jp