Walsh, Laurence J.

University of Queensland eSpace

22 auxiliary January/February 2007
infection | CONTROL
T he use of antimicrobial mouthrinses as anadjunct to mechanical methods forcontrolling dental plaque biofilms is well
established. Fewer clinicians, however, are aware
of the possible benefits of antimicrobial
mouthrinses used immediately before clinical
procedures to reduce the levels of microorganisms
in aerosols generated by air turbine handpieces;
ultrasonic scalers; air polishing and air abrasion
devices; and triple water sprays. These aerosol
clouds extend approximately one metre from the
patient’s mouth and contain bacteria, fungi and
viruses from the patient’s oral cavity as well as
bacteria from dental equipment waterlines. The
latter can pose a risk of respiratory infection to
dental staff with compromised physical or immune
defences. While large droplets generated from a
patient’s saliva may fall under the influence of
gravity to the floor, smaller droplets remain
suspended in the air for 30 minutes or more, during
which time they may be inhaled by dental staff as
well as by other patients.
A number of methods have been shown to reduce
(but not eliminate) the microbial content of
aerosols, including the use of rubber dam, place-
ment of high velocity evacuation, surgical plume
filtration near the oral cavity, and patients brushing
their teeth immediately before a dental visit.
In the past 15 years, numerous studies have
shown that antimicrobial mouthrinses when used as
pre-procedural rinses can decrease the number of
microorganisms aerosolized during clinical proce-
dures. These studies have typically involved
patients who have abstained from all oral hygiene
procedures for 24 hours, who then undergo a con-
ventional procedure whilst culture plates
positioned in multiple locations across the dental
surgery recover viable aerobic bacteria in the
aerosol cloud. These methods underestimate the
total effect of these rinses on the microbial flora
since fastidious bacteria, anaerobes, fungi and
viruses are not enumerated. Nevertheless, they give
some indication as to the reducing effect gained
from this strategy.
Essential oils
A double-blind, controlled, cross-over, clinical
study showed that using an essential oil antiseptic
mouthrinse for 30 seconds produced a 94.1%
reduction in recoverable bacteria (measured in
colony forming units - CFUs) during 10 minutes of
ultrasonic scaling, compared to non-rinsed con-
trols, while a vehicle control rinse produced a
33.9% reduction.1
Pre-procedural mouthrinsing:
beyond bacterial control
Having your patient rinse before a procedure is healthier for all
By Professor Laurence J. Walsh
Figure 1. Effect of a 30-second mouthrinse with
an essential oil product (Listerine) on salivary
microflora (aerobic bacteria). The upper part of
the culture plate (marked with an ink pen) shows
the baseline level of bacteria before rinsing, while
the lower panel shows bacteria recovered imme-
diately after rinsing, using sterile saline. Colony
counts show a reduction of greater than 2 logs
(recovery less than 1%).
January/February 2007 auxiliary 23
infection | CONTROL
Follow-up clinical studies which fol-
lowed the same basic design determined
that rinsing with an essential oil rinse
(Listerine Cool Mint) gave a 92.1%
reduction in viable bacteria in aerosols
generated immediately after rinsing and a
91.3% reduction in aerosols generated 40
minutes after rinsing,2,3 while using a 5%
hydroalcohol control rinse gave only a
10%-20% decrease relative to baseline
levels. Later studies documented that the
suppressing effect was sustained for up to
60 minutes.4
Chlorhexidine
Clinical studies assess-
ing the effect of
c h l o r h e x i d i n e
rinses on aerosols
have in general
used the 0.12%
c o n c e n t r a t i o n
products from the
North American
market rather than
the 0.2% products
commonly in use in
Australia. Nevertheless,
positive results have been
reported for these less concen-
trated chlorhexidine rinses, compared
with vehicle controls.5 While the spectrum
of action differs between the two, looking
at total microbial counts, the effect size is
similar between chlorhexidine and essen-
tial oil products, with some studies
indicating a greater effect with chlorhexi-
dine than with essential oils.6 Typical
suppression rates for 0.2% chlorhexidine
products (such as Colgate Savacol) are an
84-87% reduction immediately after
rinsing, and an 88-92% reduction up to 5
hours after mouthrinsing.
What about fungi and viruses?
The anti-fungal actions of chlorhexidine
and essential oil products have been
known about for many years, however
less attention has been drawn to potential
antiviral actions of these agents. As bio-
cides, both work on multiple sites within
cell membranes. Their action on lipid-
based membranes gives them the ability to
affect viral envelopes.7,8 Many common
pathogenic viruses, including Herpes
Simplex virus (HSV) and HIV have
envelopes which are derived from human
host cells when the assembled viruses bud
off from the cell.
Laboratory studies exploring the effects
of various formulations of essential oils
(Listerine and Listerine Tartar Control)
and chlorhexidine (0.12% and 0.2%)
using cell cultures have shown that a 30
second exposure of concentrated prepara-
tions of HSV and HIV leads to
inactivation of these viruses. The antiviral
effects of all four products were found to
be similar.8 HIV is not transmitted via
saliva, whereas salivary transfer is the
major route of transmission for
HSV, since patients with
active lesions of herpes
labialis have Herpes sim-
plex virus type I in their
saliva. When such patients use
pre-procedural mouthrinses, direct meas-
urement can be made of the effects of
rinsing on viral levels. Use of an essential
oil rinse for 30 seconds has been shown to
reduce recoverable infectious viral parti-
cles (virions) to zero, with a 100 fold
reduction in viral levels at 60 minutes
after rinsing.9 While patients with active
oral or peri-oral HSV lesions are regarded
as unsuitable for dental treatment without
the use of additional precautions, the
finding of this clinical study reinforces the
point that using antimicrobial rinses can
exert effects on enveloped viruses as well
as bacteria. This is not to depreciate in any
way the importance of wearing a mask,
but does emphasize the value of pre-pro-
cedural rinsing as an adjunctive infection
control measure.
References
1. Fine DH, Mendieta C, Barnett ML, Fur-
gang D, Meyers R, Olshan A, Vincent J.
Efficacy of preprocedural rinsing with an
antiseptic in reducing viable bacteria in
dental aerosols. J Periodontol. 1992;
63(10):821-4. 
2. Fine DH, Yip J, Furgang D, Barnett
ML, Olshan AM, Vincent J. Reducing
bacteria in dental aerosols: pre-procedural
use of an antiseptic mouthrinse. J Am
Dent Assoc. 1993; 124(5):56-8.
3. Fine DH, Furgang D, Korik I, Olshan A,
Barnett ML, Vincent JW. Reduction of
viable bacteria in dental aerosols by pre-
procedural rinsing with an antiseptic
mouthrinse. Am J Dent. 1993; 6(5):219-21. 
4. DePaola LG, Minah GE, Overholser
CD, Meiller TF, Charles CH, Harper DS,
McAlary M. Effect of an antiseptic
mouthrinse on salivary microbiota. Am J
Dent. 1996; 9(3):93-5. 
5. Klyn SL, Cummings DE, Richardson
BW, Davis RD. Reduction of bacteria-
containing spray produced during
ultrasonic scaling. Gen Dent. 2001;
49(6):648-52.
6. Logothetis DD, Martinez-Welles JM.
Reducing bacterial aerosol contamination
with a chlorhexidine gluconate pre-rinse.
J Am Dent Assoc.1995; 126(12):1634-9.  
7. Dennison DK, Meredith GM, Shillitoe
EJ, Caffesse RG. The antiviral spectrum of
Listerine antiseptic. Oral Surg Oral Med
Oral Pathol Oral Radiol Endod.1995;
79(4):442-8. Meiller TF, Silva A, Ferreira
SM, Jabra-Rizk MA, Kelley JI, DePaola
LG. Efficacy of Listerine Antiseptic in
reducing viral contamination of saliva. J
Clin Periodontol. 2005 Apr;32(4):341-6. 
9. Baqui AA, Kelley JI, Jabra-Rizk MA,
Depaola LG, Falkler WA, Meiller TF. In
vitro effect of oral antiseptics on human
immunodeficiency virus-1 and herpes
simplex virus type 1. J Clin Periodontol.
2001 Jul;28(7):610-6.
Professor Laurence J. Walsh is the tech-
nology editor of Australasian Dental
Practice magazine. He is also a noted
commentator on and user of new technolo-
gies and is the Head of The University of
Queensland School of Dentistry.
Figure 2. Effect of a 30-second mouthrinse with 0.2% chlorhexi-
dine (Colgate Savacol) on salivary microflora (aerobic bacte-
ria). As with Figure 1, the upper part of the culture plate
(marked with an ink pen) shows the baseline level of bacteria
before rinsing, while the lower panel shows bacteria recovered
immediately after rinsing, using sterile saline. Colony counts
show a reduction of greater than 2 logs (recovery less than 1%).


Pre-procedural mouthrinsing: beyond bacterial control

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Pre-procedural mouthrinsing: beyond bacterial control

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