Evaluation of Toothpaste

Evaluation of Toothpaste (IS: 6356-1953)

This standard prescribes requirement & methods of sampling & test for toothpaste. As per guidelines toothpaste shall be of either type I (Non-fluorinated) or type II (Fluorinated).

Composition

Toothpaste shall not contain mono or disaccharides for e.g. sucrose or other readily fermentable carbohydrates. All the raw materials used shall confirm to respective Indian standard wherever they exist.

Homogeneity

The paste shall extrude from the collapsible tube or any other suitable container in which it is packed at 27±2⁰C in the form of homogenous mass with the application of normal force & without using excessive force which could cause injury to the tubes or the container. It shall be possible to extrude bulk of contents from the container (tube) starting from crimp & then tube rolling it gradually.

Stability

The toothpaste shall not segregate, ferment or physically deteriorate during normal condition of storage & uses. When heated to a temperature of 45±2⁰C for a period of 28 days the toothpaste shall not undergo phase separation, gassing, fermentation or otherwise deteriorate aesthetically. When cooled to a temperature of 5⁰C for 1 hour after taking out & pressing the tube, the paste shall be found extrudable form the tube.

Tube inertness

Toothpaste packed in collapsible tubes or any other suitable container shall not corrode or deteriorate or cause contamination in the toothpaste during normal condition of storage & use. When heated to a temperature of 45±2⁰C for 10 days, the paste shall then be examined visually by extruding part of contents. The internal surface of the tube shall be examined after slitting (cut) it, open & removing the open contents, there should be no sign of corrosion, chemical attack or other damage.

The toothpaste shall also comply with the following requirements

Sr.No.	Characteristics	Requirement for type-1 (Non-fluorinated type)	Requirement for type -2 (Fluorinated type)
1.	Hard & sharp edge abrasive particles	Absent	Absent
2.	Spreadibility (cm), (max.)	8.5	8.5
3.	Fineness (a) Particle retained on 150µ sieve (%age by mass, maximum) (b)Particle retained on 75µ sieve (%age by mass, maximum)	0.5 2	0.5 2
4.	pH of 10% aq. suspension	5.5-10.5	5.5-10.5
5.	Test for Pb (maximum)	20 ppm	20 ppm
6.	Arsenic (As2O3)	2	2
7.	Foaming part in ml, min. (applicable to foaming toothpaste only	50	50
8.	Fluoride ion, ppm, max.	50	50
9.	Microbial purity (a) Total aerobic bacteria/gm, max. (b)Salmonella or E.coli	1000 Absent	1000 Absent

Determination of sharp &edge abrasive particles

Extrude the paste 15-20 cm long, each from at least 10 collapsible tubes on a butter paper, test the paste by pressing it along its entire length by a finger for the presence of hard & sharp edge abrasive particles. In all cases, the material shall be free from such particles.

Determination of spreadbility

Weigh about 1 gm of toothpaste at the centre of glass plate (10 by 10 cm) & place another glass plate over it carefully place 2 kg wt. at the centre of the plate (avoid sliding of the plate). Measure the diameter of the paste in cm after 3 minutes. Repeat the experiment thrice & report the average.

Determination of fineness

Place about 10 gm of toothpaste, accurately weight, in a 100 ml beaker. Add 50 ml of water & allow to stand for 30 minute with occasional stirring until the toothpaste is completely disperse. Transfer to the 150 µ IS sieve & wash by means of a slow stream of running tap water. Let the water drained from the sieve & then dry the sieve containing the residue in an oven, if there is any residue on the sieve carefully transfer it to a tare watch glass & dry it to constant mass in an oven at 105±2⁰C.

Calculation

i.)        Material retained on sieve % by mass

----------------------------------------------    ×   100

     Material taken   

ii.)       Sieve is now 75µ weigh accurately 10 gm of toothpaste & proceed as above & if there is any residue on the sieve. Transfer it to a tare watch glass & dry it to constant mass in an oven at 105±2⁰C.  

pH determination

Take 10 gm of toothpaste in 150 ml beaker. Add 10 ml of freshly boiled & cooled water (at 27⁰C). Stir well to make a thorough suspension. Determine the pH of the suspension within 5 minutes using pH meter.

Determination of lead

The color produced with hydrogen sulphide solution is matched against that obtain with standard lead solution.

Determination of arsenic

Arsenic is present in solution of material reduced to arsine, which is made to react with mercuric bromide paper. Stain produced is compared with standard stain.

Foaming power

A suspension of the material in water is taken in a graduated cylinder & given 12 shakes under prescribed condition. The volume of the foamed is observed after keeping the cylinder for 5 minutes.

Procedure: weigh about 5 gram of toothpaste, accurately in a 100ml glass beaker. Add 10 ml of water cover the beaker with a watch glass & allow it to stand for 30 minute. This operation is carried out to disperse the toothpaste. Ensure that the detergent is completely dissolve, warming the aqueous suspension if necessary. Stir the contents of the beaker with glass rod & transfer the slurry to the 250ml graduated cylinder, ensuring that no foam (more than 2 ml) is produced &  no lump paste goes into the cylinder. Repeat the transfer of the residue left in the beaker with further portions of 5-6 ml of water ensuring that all the matter in the beaker is transferred to the cylinder. Adjust the content in the cylinder to 50ml by adding sufficient water & bring the contents of the cylinder to 30⁰C. Stir the content of the cylinder with a glass rod or thermometer to ensure a uniform suspension as soon as the temperature of the contents of the cylinder reaches 30⁰C. Stopper the cylinder & give it 12 complete shakes, each shake comprising of upside-down movements. After the shakes allow the cylinder to stand still for 5 minute& read the volume of foam + water.

Determination of fluoride ion

Principle: sodium monoflurophosphate or fluoride ions are extracted with water from toothpaste & extract is fused with Na₂CO₃ to convert it into NaF & then determined potentiometrically with the help of fluoride ion sensitive electrodes.

Calculation: a graph is plotted for conc. of fluoride ion against potential (mV) on semi log graph paper. The potential is plotted on X-axis & mg of fluoride ion on Y-axis (on log scale). From calibration curve is determined the mg of fluoride ion in the test solution. Conc. Of fluoride ion in toothpaste (ppm)

                         =      2 a × 10000

                       M

a = mg of fluoride ion calculated from calibration graph

M= Mass of sample taken in gram

Microbial purity

i.)        For total aerobic bacteria: - the test consists of plotting a known dilution of sample on soyabean (casein digest, agar medium, and any other suitable for growth of aerobic bacteria) incubating them for the specified periods to permit the development of visual colonies for counting.

ii.)       For salmonella & E.coli: - the test consists of enrichment of above bacteria form simple in a suitable culture mediums & then a selective culture medium & after incubation, streaking on selective agar plates for identification

Shelf-life

This should be declared by the manufacture up to which the product may be used should be mentioned in tubing & carton

Packaging & Marketing

Toothpaste shall be packed in collapsible tubes or in any other suitable container like sashes. When packed in tubes, the tubes shall be properly crimped & shall have a leak proof cap. The tube if necessary may further be packed cartons

Marking

The tubes & cartons should be legibly marked with following information

i.)        Name & type of toothpaste

ii.)       Source of manufacture

iii.)      Net mass of the material in the tube

iv.)      Batch number

v.)       Fluoride ion content in ppm

vi.)      Date of expiring

vii.)     Critical ingredients of the formulation

viii.)    Foaming & non-foaming

*the container may also be marked with std. mark (ISI mark)

Sampling

Representative test samples of the material be drawn as prescribe in IS 3958-1984.

Number of test & criteria for conformity: -the test for stability & container inertness shall be type test & shall be performed for product approval whereas test for hard & sharp edge abrasive particles, spreadibility, fineness, Ph, heavy metals, foaming power, fluoride ion & microbial purity shall be carried out on each for acceptance of the product.