Fluoride and Silver Pharmacokinetics of DSF Applied Topically to Teeth of Adults. Erythema, Bleeding, White Changes, Ulceration and Pigmentation Were Assessed Clinical Trial
Official title:
Characterization of Fluoride and Silver Pharmacokinetics of Diammine Silver Fluoride Applied Topically to Teeth of Adults
There is growing worldwide interest in the use of diammine silver fluoride (DSF) as a topical
agent to treat dentin hypersensitivity and dental caries. It has been available in various
formulations for many years, but its safety profile has never been fully characterized.
This preliminary study determined the applied doses (3 teeth treated), maximum serum
concentrations, and time to maximum serum concentration for fluoride and silver in 6 adults
over 4 h. Fluoride was determined using the indirect diffusion method with a fluoride
selective electrode, and silver was determined using inductively coupled plasma-mass
spectrometry. The mean amount of DSF solution applied to the 3 teeth was 7.57 mg (6.04 µL).
Participants Six healthy volunteers (4 females, mean age 36.2, range 23-52 yr) were recruited
among staff members of the Universidad Católica de Santa María, Arequipa, Peru. Participants
were taking no medications and had most permanent teeth present. Participants were asked to
avoid fish or tea for 12 h before the study and not use fluoridated toothpaste 4 h prior. The
Comité de Etica de Investigacion, Universidad Católica de Santa María approved the study and
informed consent was obtained.
Study Agent DSF [Ag(NH3)2F, CAS RN 33040-28-7, Saforide, Toyo Seiyaku Kasei Co. Ltd. Osaka,
Japan] was used. DSF is clear and colorless, with a weak odor of ammonia. The 38% solution
contains between 24.4-28.8% (w/v) silver (Ag), and 5.0-5.9% fluoride (F). Concentrations of
Ag and F in the DSF used for study were 24.9% and 5.5%, respectively, and the specific
gravity was 1.253 at 25°C (Certificate of Analysis Lot #155060). Diammine silver fluoride is
also referred to in the literature as silver diammine fluoride, silver diamine fluoride or
silver fluoride.
Procedures Three maxillary teeth (cuspid and premolars) in the same quadrant were treated.
Three teeth were treated because this was the average number of sensitive teeth reported in
an epidemiological study of adults [5]. The teeth were free of restorations or cavitation.
The facial surface was dried with cotton gauze and then DSF was applied to the cervical area
of each tooth. The teeth were isolated in order to avoid wetting the brush with saliva. Each
tooth was coated using a separate microbrush, which was dipped in the DSF and weighed before
and after the application (Model S2000, Kern & Sohn GmbH, Balingen, Germany). The sum of the
differences in weight of material applied was calculated for each participant.
Blood Collection Immediately before application of DSF and then again at approximately 30
min, 1, 2,3 and 4 h after application, blood was obtained from a peripheral vein. The time
periods were picked based on a previous pharmacokinetics study of fluoride varnish [6]. The
blood was transferred to a fluoride-free plastic Vacutainer tube with clot activator (BD
Vacutainer Plus Plastic Serum Tube, BD Diagnostics, New Jersey). The tubes were spun at 1100
g for 10 min and serum transferred by plastic pipette to plastic cryogenic tubes. The samples
were frozen and transported to the University of Washington for analysis.
Analysis Fluoride. Samples were thawed and analyzed in duplicate or triplicate using the
diffusion and detection method with hexamethyldisiloxane (HMDS) and Orion F-sensitive
electrode [7-8]. To improve detection, the pre-diffusion step was omitted [9], and seals were
completed before mixing 1 mL serum with 1 mL HMDS, saturated 3 M H2SO4 [10]. The trapping
solution was 20 µmoles 1 M NaOH. It was dried down to eliminate variability of evaporation
and residual HMDS before adding 100 µL 3 M acetic acid to a final pH 3.4. Standards were 10
and 100 µM fluoride in the same final concentration of NaOH and acetic acid corresponding to
1 and 10 µM F in the samples. ORION F and sleeve type reference electrodes were coupled with
an Accumet Basic 0.1 mV meter (Thermo Fisher Scientific, Milwaukee WI).
Vacutainers were tested for fluoride by adding bovine plasma to 2 tubes and letting them sit
overnight before combining the 2 samples and comparing them to plasma directly placed in
diffusion dishes. Average concentrations (μM±SD) were 0.34±0.014 and 0.32±0.012,
respectively. Therefore, less than 2% F in the serum samples came from the Vacutainers and
clot enhancer. Recovery (mean±SD) of 1 nmole/ml F added to bovine serum was 101±4%. Fluoride
levels were averaged and are expressed as µM.
Silver. Samples were thawed and analyzed using Inductively Coupled Plasma-Mass Spectrometry
(EPA 6020a Rev.1 2007). Serum (0.5 mL) was brought to 2 mL with dilute acid (final
concentration: 2% HCl, 1% HNO3; trace metal grade, Fisher, Fairlawn, NJ). Samples were
centrifuged (1290 g) for 10 min and filtered (0.45 µm, PTFE; all polypropylene syringe) into
15 mL polypropylene centrifuge tubes. The samples were analyzed on an Agilent 7500CE (Santa
Clara, CA) inductively-coupled mass spectrometer (ICPMS) with He as the collision cell gas
and an ASX-510 autosampler (CETAC, Omaha, NB). A Micromist nebulizer (Glass Expansion,
Pocasset, MA) was used (1.15 L/min carrier gas; no makeup gas). Spray chamber temperature was
2°C. RF power was 1500 W. Ag was quantified using Y as internal standard. Calibrants were
diluted with 2% HCl and 1% HNO3 prepared from commercial ICPMS grade solutions (Ultra
Scientific, N. Kingstown, RI; BDH Aristar, VWR, Radnor, PA) and ranged from 0.5-50 ng/mL.
Calibration was by weighted (1/cps) linear regression. Data was corrected by procedure blank.
Values of silver less than 2 ng/mL were recoded to 2. Silver concentrations are expressed as
ng/mL.
Soft Tissue Assessment The gingiva adjacent to the application of DSF and the mucosa
generally were observed at baseline and 24 h after treatment. Erythema, bleeding, white
changes, ulceration and pigmentation were assessed using methods developed for an earlier
study [1].
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