Clinical Research Associates
Prescription Level Dentifrices (5000 ppm F or 1.1% NaF)
Contents:
Procedure for Testing Dentifrice Fluoride Content
Determining Dentifrice Sample Size
- Cut a 5 ml pipette into sections of length equivalent to 1 ml volume.
- Weigh the cut pipette section (dempty).
- Carefully fill the cut and weighed pipette section with toothpaste, being careful to not include bubbles or voids. Smooth the ends of the dentifrice so it is even with the cut tube.
- Reweigh the pipette section with the toothpaste inside (dfull). This results in a density measurement of toothpaste in g/ml.
- Calculate the mass of toothpaste needed to equal 10 ml. (The amount needed for the test.)
m10ml toothpaste = 10 ml * (dfull - dempty)
- Repeat steps 2-5 above for each product several times and average to solve for each product’s mass in 10ml.
Preparing the Test Sample
- Dispense a mass of dentifrice equivalent to 10 ml (determined in step 6 above) into a 25 ml plastic sample vial.
- Add 10 ml of TISAB.
- Stir until smooth. This prepares a slurry of 50% TISAB and 50% dentrifice by volume.
- Use an Orion Ionalyzer and the Orion Model 96-09 Combination Fluoride Electrode to determine the mV reading. This mV reading can then be translated into parts per million (ppm) of fluoride using a calibration curve.
- Repeat the test several times for each product and determine the resulting ppm.
Basics of Fluoride Calibration Curve
- Using the ion probe, mV readings were obtained from five standard solutions (.01, .001, .0001, .00001, .000001 moles/liter fluoride concentration). Readings are graphed on log paper to create a standard curve.
- After the standard curve is established, a graphing program such as Tablecurve (Jandel Scientific) can fit an equation to the given data. The following are two equations resulting from this curve fitting procedure. The choice between equations depends on the amount of mV reading. If the mV reading is less than 100 mV use equation 1, otherwise use equation 2.
(Equation 1) If mV reading < 100 mV: lny = a + b
(Equation 2) If mV reading >100 mV: y0.5 = (a + cx)(1 + bx + dx2)
x = reading in mV
y = fluoride content in moles/L
a,b,c,d = constants to set equation
3. Solve for y (moles/L).
Equation 1. y = e (a + bx)
Equation 2. y = {(a + cx)(1 + bx + dx2)}2
This may be done using a spreadsheet. Enter information for the following: dentrifice name, sample #, dentrifice mass (g), measure date, constants, and reading (mV) value.
Compute results as needed.
F(µg) = {sol.vol.ml(moles/L)}*{F molecular weight(g/mole)}*{solution volume(L)}*(106µg/g)
F(ppm) = F(µg)/ml of solution
Dentifrice, Rx (5000 ppm F) Survey Methods
Three test dentifrices all claiming 5000 or higher ppm F (Control Rx, Prevident 5000 Plus, and Pro-Dentx 1.1% Plus) were included in this study. Two tubes of each test dentifrice were sent to each of 25 clinical field sites. The CRA Evaluator dentist then selected two subjects from among his/her patients to participate in the study. The tubes of test dentifrices were all unlabeled, white tubes so neither the dentist nor the test subject knew the brand of the dentifrices being tested. Each test subject received one tube of each test dentifrice and was instructed to use each test dentifrice twice daily for one month.
A total of 46 test subjects from 24 dentists completed the study. All products were graded on a standardized evaluation sheet, using a 4-point grading scale (Excellent, Good, Fair, Poor). Patients were asked to rate various characteristics for each of the 3 test dentifrices. They were also asked to indicate whether or not they would purchase each dentifrice and to give any comments desired.
A mean rating was computed by assigning 4 points for an Excellent, 3 points for a Good, 2 points for a Fair, and 1 point for a Poor. The mean ratings for the test dentifrices were compared using Analysis of Variance and Tukey's HSD multiple comparison procedure.
Dentifrice, Rx (5000 ppm F) Survey Results
| BRAND | AVERAGE GRADE | |
| Prevident 5000 Plus | 2.9 |  |
| Control Rx | 2.6 | |
| Pro-Dentx 1.1% Plus | 2.2 | |
The overall rating was calculated by combining the average grades for the 5 individual characteristics (taste, aftertaste, dispensing, consistency, appearance).There was no significant difference overall among the 3 test dentifrices.