Abstract The mouthwash brands, Scope, Listerine ... - Franklin College

Abstract
The mouthwash brands, Scope, Listerine, Cepacol, Rembrandt, and Therasol,
were tested to see which was the best at killing the bacteria, Bacillus subtilis and
Staphylococcus epidermidis. Disks of the different mouthwashes were put on the
bacteria which grew on agar in petri disks. The zones of inhibition were measured which
showed that Therasol was most effective against the bacteria because it had the largest
significant difference in it’s zone of inhibition. Scope was significantly better at the 99%
confidence rate than all other mouthwashes except Therasol. Sterile techniques were
used in order to make sure that only the two bacteria were tested. The active ingredients
were found to be domiphen bromide, cetyl pyridinium chloride.
Introduction
When eating, bacteria in the mouth break down food causing unwanted
byproducts to be made, which can cause tooth decay and bad breath. Mouthwashes
contain different chemicals in order to be the best at killing the bacteria that causes these
problems. Mouthwash advertisements claim that certain mouthwashes are better at doing
this than others. These reports can sometimes be misleading to consumers because they
may not always portray the truth. Experiments can be performed that can prove to
consumers which mouthwash works the best. Bacteria can be seen growing on agar
when the clear, sterile agar becomes cloudy. Disks of different mouthwashes are but in
the bacteria infested agar, forming a zone of inhibition, which can be compared to other
mouthwashes to show how much bacteria they have killed. This experiment measures
the Zone of inhibitions that mouthwashes, Scope, Listerine, Cepacol, Rembrandt, and

Therasol, made on the Bacillus subtilis and Staphylococcus epidermidis bacteria.
According to Kevin Devin, the Bacillus subtilis bacteria are often used in cooking and in
the general food industry because of the enzymes it produces (Budavari 1989). As it’s
name suggest, the Staphylococcus epidermidis bacteria is found in the skin of humans
(Browder 2002). John Landolo said that an infection of this bacterium can occur as a
result of unsanitary handling of food and water, but can be treated with a high success
rate (Devin 2000). This bacterium forms a white colony, which can be seen on the agar
(http://medic.med.uth.tmc.edu/path/00001456.htm 2002). Listerine was hypothesized to kill the
most bacteria because it contained the highest amount of alcohol. This would be proven
true if the zone of inhibition for Listerine was greater than the other mouthwashes’ zones.
Materials and Methods
The procedure was followed exactly as in the lab handout except saliva was not
extracted or used, so only the bacteria were tested with the mouthwash (Browder 2002).
The mouthwashes used were Scope, Listerine, Cepacol, Rembrandt, and Therasol and the
bacteria tested were Staphylococcus epidermidis and Bacillus subtilis. The control of
water was used in place of a mouthwash so that comparisons can be made between the
zones of inhibition and the control, where no bacteria grew. Sanitation techniques were
involved in the handling of the agar and the bacteria are used in detail so that extra
bacteria wasn’t tested in the experiment. The techniques used were to leave the agar in
the water bath until they could be quickly used in order for the agar to not solidify. The
tops to the petri plates were left on until the material was ready to be poured into them,
which kept the plates sanitary until use. Sterile filter paper disks were used which

increased sanitation so that the mouthwash would only work on the bacteria and not
anything foreign that had gotten on the disks. Between retrieval of each disk, the forceps
were dipped in alcohol and put through a Bunsen burner flame in order to keep them
sterile. The lid to the petri plate was lifted just enough to place the disk on the agar in
order to keep sanitation as high as possible.
Results
The lab partner that I worked with was Dana Derrrico.
Table 1 shows the raw data for the class for the Bacillus subtilis.
Table 1
Name Water Scope Listerine Cepacol Rembrandt Therasol
Molly Jackson/
Dana Derrico
0 16 0 15 15 23
Jeanna/
Jamie/ Leah
0 12 0 9 11 14.5
Gina/Sarah 0 12 0 10 10 15
Linsey/Bradi//
Danny
0 14 0 10 13 19
John/Kara 0 20 0 10 12 16
Julie/Alanna 0 12 0 7 10 15
Katie/Lauren/
Meredith
0 8 0 5 6 8
Julie Drake/
Heath Ewing
0 12 0 8 13 16
Blake
Schepman/
Rich
Ashabranner
0 10 0 8 8 14
Amy
Sparks/Heather
Kessens
0 19 0 11 14 18
Spencer
Beard/Brandon
Armacost
0 11 0 18 13 17
Terry Coy/Lori 0 19 0 11 12 24
Jennifer
S./Kevin C.
0 15 0 9 9 23

Ashley
G./Shayne G.
Ryan W./Jeff
M.
LaCoya
Hill/Lensa
Abera
Jesse K./Shawn
M.
0 12 0 10 11 13
0 14 12 11 15 15
0 10 0 12 10 16
0 13.5 0 9 10 15
Table 2 shows the raw data for the class for Staphylococcus epidermidis.
Table 2
Name Water Scope Listerine Cepacol Rembrandt Therasol
Molly
Jackson/
Dana Derrico
0 28 0 12 8 19
Jeanna/
Jamie/ Leah
0 30 12 10 7.5 15
Gina/Sarah 0 20 0 10 8 14
Linsey/Bradi/
Danny
0 18 0 10 9 21
John/Kara 0 10 0 12 11 15
Julie/Alanna 0 19 0 13 10 16
Katie/Lauren
/Meredith
0 9 0 22 6 11
Julie Drake/
Heath Ewing
0 18 0 14 10 19
Blake
Schepman/
Rich
Ashabranner
0 14 0 9 10 17
Amy
Sparks/Heath
er Kessens
0 28 0 33 9 18
Spencer
Beard/Brand
on Armacost
0 18 0 12 10 17
Terry
Coy/Lori
0 17 0 10 8 16
Jennifer
S./Kevin C.
0 19 0 10 11 26
Ashley
G./Shayne G.
0 11 0 26 18 15
Ryan W./Jeff
M.
4 23 0 12 10 7

LaCoya
Hill/Lensa
Abera
Jesse
K./Shawn M.
0 30 0 12 0 17
0 19 0 10 8 17
The mean values for the zone of inhibition are compared in Table 3 for Staphylococcus
epidermidis.
Table 3
Means of Zone of Inhibition
(mm)
2 5
2 0
1 5
1 0
5
0
Scope
Z o n e o f I n h i b i t i o n f o r S t a p h y l o c o c c u s
e p i d e r m i d i s
Listerine
Cepacol
Rembrandt
M o u t h w a s h
Therasol
The mean values for the zones of inhibition are compared in Table 4.
Table 4
Means of Zone of
Inhibition (mm)
18
16
14
12
10
8
6
4
2
0
Scope
Zone of Inhibition for B acillu s su b tilis
Listerine
Cepacol
The comparison values are shown in table 5.
Rembrandt
M o u th w a sh
Therasol

Table 5
B-Water B-Scope B-
Listerine
B-
Cepacol
B-Scope 16.41381
B-Listerine 1 11.80428
B-Cepacol 14.16084 3.04296 9.40171
B-
19.0576 2.175971 11.48806 1.199867
Rembrandt
B-
Rembran
dt
B-
Therasol
S-Water S-Scope S-
Listerine
B-Therasol 17.1375 2.410632 13.2482 5.300177 4.644653
S-Water 1 15.5057 0.632456 13.14668 17.34359 16.4143
S-Scope 12.18738 3.322738 10.74357 5.305495 4.798455 1.559539 11.9116
S-Listerine 1 11.80428 0 9.40171 11.48806 13.2482 0.632456 10.74357
S-Cepacol 8.623172 0.24322 8.186556 1.59419 1.537283 1.389819 8.38925 2.432753 7.502606
S-
Rembrandt
10.79688 3.811332 7.605713 1.040277 2.20949 5.892068 10.12252 5.790182 7.605713
S-Therasol 16.83877 2.324451 13.06928 5.185689 4.526232 0.064176 16.13787 1.601491 13.06928
S-
Cepacol
S-
Rembran
dt
2.698467
1.338613 5.782196
Table 6 contains the T-table to compare to table 4 to see if the differences were
significant.
Table 6
Degrees of freedom 32
95% 2.037
99% 2.738
99.9% 3.622
Scope ingredients: water, alcohol(9.9%), sorbitol, sodium becarbonate, poloxamer 407,
Polysorbate 80, sodium saccharin, cetyl pyridinium chloride, domiphen bromide.
Listerine: thymol, eucalyptol, methyl salicylate, and menthol. Also contains water, SD

alcohol 37 (26.9%), benzoic acid, poloxamer 407, and caramel
Cepacol: Ceepryn (cetylpyridinium chloride) (0.05%), Alcohol (14%), Edetate Disodium,
FD&C yellow No. 5, flavors, glycerin, polysorbate 80, saccharin, sodium
bephosphate, sodium phosphate, water
Rembrandt: water, sodium citrate, methylparaben, sodium lauryl sulfate, natural and
artificial flavors, polysorbate 20, citric acid, sodium benzoate, sodium saccharin
Therasol: water, SD alcohol 38B (8%), glycerine (6%), N,N-alkyl dimethyl amine oxide
and N,N-alkyl dimethyl glycine, sodium fluoride (0.02%), saccharine, FDC blue
No. 1, and flavoring
Discussion and Conclusions
The petri plate, which was prepared without using sterile techniques, had different
kinds of bacteria growing on it compared to the bacteria plates. This showed the
importance of using sterile techniques so that only one bacterium on the plates would be
tested. The results answered the question of which mouthwash works the best against
bacteria because Therasol showed to have a significant difference over the other
mouthwashes. The difference is shown when comparing table 3 to table 4 with the t-
values on the 95% confidence rate at being the best at killing the bacteria Bacillus
subtilis. With the Staphylococcus epidermidis, all mouthwashes, except Listerine were
significantly better than water. Scope and Therasol were both equally effective.
Therasol was significantly better than all mouthwashes except Scope and Cepacol at the
95% confidence rate. Scope had a significant difference at the 95% rate against all the
mouthwashes except for Therasol. Scope contained Sorbitol and sodium bicarbonate,

which the other mouthwashes did not. This shows that Sorbitol and sodium bicarbonate
could be the chemicals that are effective in killing bacteria. The hypothesis was proven
wrong because by statistical analysis, because Listerine was not effective against the
bacteria, which shows that alcohol is not the ingredient that kills the bacteria. Cepacol
and Scope were significantly better at killing Staph than Bacillus at the 99.9% confidence
rate and Therasol was equally effective at killing Staph and Bacillus. The difference
between the two bacteria tested shows that Staphylococcus epidermidis is slightly more
sensitive to the mouthwashes than the Bacillus subtilis since the mouthwashes on it had
bigger zones of inhibition. This experiment could be further tested on other bacteria in
order to see if the different mouthwash brands kill more kinds of bacteria than other
brands.

References
1. Budavari, Susan. The Merck Index. Rahway, NJ: 1989 ed. 11
2. Devin, Kevin M. “Bacillus subtilis, Genetics.” In Encyclopedia of Microbiology. New
York: Academic Press, 2000.
3. Landolo, John J. “Staphylococcus.” In Encyclopedia of Microbiology. New York:
Academic Press, 2000.
4. “Microbiology Lab.” Comparison of the Antibacterial Activity of Several
Mouthwashes. Browder 2002.
5. “Staphylococcus.” 17 April 2002.
.
6. “Staphylococcus.” 17 April 2002 .