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The aim of this review article is to provide a scientific platform that will enable the dental team to develop a rational approach to plaque control based on the latest knowledge of the role of the oral microflora in health and disease. The resident oral microflora is natural and forms spatially-organised, interactive, multi-species biofilms on mucosal and dental surfaces in the mouth. These resident oral microbial communities play a key function in the normal development of the physiology of the host and are important in preventing colonisation by exogenous and often undesirable microbes. A dynamic balance exists between the resident microflora and the host in health, and disease results from a breakdown of this delicate relationship. Patients should be taught effective plaque control techniques that maintain dental biofilms at levels compatible with oral health so as to retain the beneficial properties of the resident microflora while reducing the risk of dental disease from excessive plaque accumulation. Antimicrobial and antiplaque agents in oral care products can augment mechanical plaque control by several direct and indirect mechanisms that not only involve reducing or removing dental biofilms but also include inhibiting bacterial metabolism when the agents are still present at sub-lethal concentrations.
Contemporary perspective
on plaque control
P. D. Marsh
requirements, how does the dental team
decide on a rational way forward? The aim
of this article is to briey review the cur-
rent knowledge in this area, give answers
to some common questions and provide
the evidence to support a contemporary
approach to plaque control.
It is a remarkable statistic that humans
are made up of about 10
of which
only ten percent are mammalian. The
majority are the micro-organisms (the
natural resident microora) that inhabit
all environmentally-exposed surfaces of
the body, where they form biolms.
composition of these biolms varies at dis-
tinct sites around the body and is directly
inuenced by the biological and physical
conditions associated with the particu-
lar habitat. These biolms are formed of
symbiotic communities of different micro-
organisms that grow on, and interact
with, the surfaces they colonise. Biolms
develop in a structured way, are spatially-
and functionally-organised, and the con-
stituent species communicate and interact
with one another.
These polymicrobial
Dental professionals are faced with a
number of apparent paradoxes when it
comes to advising patients on the most
appropriate strategy for plaque control.
During training, students are taught that
caries and periodontal diseases result from
the activity of bacteria in dental plaque
and that effective self-performed plaque
removal is an essential part of the preven-
tion and management of these diseases;
but now it is being reported that many of
the micro-organisms in the mouth make an
important contribution to our well-being!
Also, many plaque control products are
formulated with antimicrobial agents that
are described as being broad spectrum and
yet these products also have to meet the
regulatory guidelines that demand that
they do not disrupt the natural balance of
the normal oral microora. In the face of
these apparently contradictory views and
The aim of this review article is to provide a scientic platform that will enable the dental team to develop a rational ap-
proach to plaque control based on the latest knowledge of the role of the oral microora in health and disease. The resident
oral microora is natural and forms spatially-organised, interactive, multi-species biolms on mucosal and dental surfaces
in the mouth. These resident oral microbial communities play a key function in the normal development of the physiology
of the host and are important in preventing colonisation by exogenous and often undesirable microbes. A dynamic balance
exists between the resident microora and the host in health, and disease results from a breakdown of this delicate rela-
tionship. Patients should be taught effective plaque control techniques that maintain dental biolms at levels compatible
with oral health so as to retain the benecial properties of the resident microora while reducing the risk of dental disease
from excessive plaque accumulation. Antimicrobial and antiplaque agents in oral care products can augment mechanical
plaque control by several direct and indirect mechanisms that not only involve reducing or removing dental biolms but also
include inhibiting bacterial metabolism when the agents are still present at sub-lethal concentrations.
biofilms display novel properties; of
clinical relevance is that they are much
less susceptible to the host defences and
antimicrobial agents.
The reasons for this
are still the subject of much debate, but
are directly linked to the properties of the
biolm itself, since the organisms retain
their intrinsic sensitivity if the biolm is
dispersed. The most common explanations
for the reduced susceptibility of biolms
to antimicrobial agents include:
• Reduced penetration of the agent into
the biolm or quenching of the agent
at the surface of the biolm
• The novel properties expressed by
bacteria when growing on a surface
• Sub-optimal conditions for activity
• The slow growth rates of attached
bacteria within biolms.
The resident microora has evolved to
co-exist in harmony with the host and
carry out key functions that are essential
to our well-being. These functions include
the ability to prevent colonisation by
exogenous (and often pathogenic) micro-
organisms (a process termed colonisation
resistance), and in the normal development
of the physiology, nutrition and immune
system of the host.
Department of Oral Biology, Leeds Dental Institute,
University of Leeds, Clarendon Way, Leeds, LS2 9LU, UK
Correspondence to: Professor Philip Marsh
Email:; Tel: +44 (0)1980 612 287
Refereed Paper
Accepted 4 April 2012
DOI: 10.1038/sj.bdj.2012.524
British Dental Journal 2012; 212: 601-606
Explains current thinking on strategies to
control dental plaque biolms.
Argues that it is necessary to restrict
biolm accumulation to levels compatible
with a healthy mouth in order to
maintain important benets provided by
some resident bacteria.
Highlights that antimicrobial agents
delivered by effective oral care products
can augment mechanical plaque control
to improve oral health.
© 2012 Macmillan Publishers Limited. All rights reserved.
The mouth is similar to other sites in the
body in that it has a natural microora
with a characteristic composition that con-
fers benet (see later).
However, on occa-
sions, this benecial relationship can break
down and disease can occur (for example,
dental caries, periodontal diseases), while
halitosis can also be a consequence.
Therefore, it is essential to appreciate the
benets that are derived from a balanced
relationship between the oral microora
and the host and to understand the pro-
cesses that predispose a site to disease if
effective control and preventative meas-
ures are to be adopted. Of clinical rele-
vance is that these measures might vary
from person to person.
The mouth is well equipped with an array
of host defences provided by both the
innate and adaptive arms of the immune
system and yet all mucosal and dental sur-
faces are naturally colonised by a diverse
collection of micro-organisms. It is becom-
ing clear that the host is not indifferent to
the presence of these consortia of microbes
and has developed mechanisms that per-
mit a benecial relationship.
There is
evidence for active communication (‘cross-
talk’) between some of the resident bacte-
ria and mucosal cells that downregulates
potentially damaging pro-inammatory
host responses to the normal oral micro-
ora, while the host retains the ability to
respond to genuine microbial insults.
precise biological mechanisms involved in
this ‘cross-talk’ are still being determined,
but pathogenic and non-pathogenic bac-
teria may initiate different intracellular
signalling pathways and innate immune
responses in epithelial cells.
As at other body sites, the resident oral
microora displays ‘colonisation resist-
ance’ and prevents the establishment in
the mouth of the many exogenous micro-
organisms we come into contact with on
a daily basis. This is because the natural
oral microora is better adapted at attach-
ment to oral surfaces, is more efcient at
metabolising the available nutrients for
growth and can produce inhibitory fac-
tors and create hostile environments that
restrict colonisation by potential microbial
invaders. A consequence for patients on
long-term broad spectrum antibiotic treat-
ment is that the resident oral microora
can be suppressed resulting in overgrowth
by yeasts and environmental bacteria in
the mouth.
Recent ndings suggest that the resi-
dent oral bacteria contribute to the main-
tenance of healthy gastrointestinal and
cardiovascular systems via the metabolism
of dietary nitrate. Approximately 25% of
ingested nitrate is secreted in saliva where
some oral resident bacteria reduce nitrate
to nitrite. Nitrite can affect a number of
key physiological processes including
the regulation of blood ow, blood pres-
sure, gastric integrity and tissue protec-
tion against ischemic injury. Nitrite can
be further converted to nitric oxide in the
acidied stomach, and this has antimicro-
bial properties, and contributes to defence
against enteropathogens and in the regu-
lation of gastric mucosal blood ow and
mucus formation. The reduction of nitrate
to nitrite in saliva fell markedly in human
and laboratory animals,
when the resident salivary microora was
deliberately suppressed using antimicro-
bial agents. The suppression of endoge-
nous nitrate reduction in the animal model
resulted in a loss of the predicted biological
benets of nitrite, including reduced gas-
tric mucus thickness, while the expected
fall in blood pressure following a nitrate
supplement was prevented.
It is of clinical importance, therefore, that
oral antimicrobials are applied according to
the recommended instructions which aim
to maintain the microora of the mouth at
levels that are compatible with oral health,
but below those which are associated with
disease. This is in order to preserve the
benecial functions of these important
resident microbes which, it is becoming
clear, are essential for both the general and
oral health of that person. Thus, antibiotics
are not a recommendation for managing
chronic periodontal disease.
It is surprisingly difcult to fully dene
what might be regarded as the normal,
resident oral microora. At present, only
about 50% of the oral microora can
be cultivated in the laboratory. This is
because of our ignorance of the growth
requirements of the more fastidious mem-
bers of the oral microora, but also due to
our naivety in attempting to grow bacteria
as pure cultures in the laboratory when
they have evolved to grow in oral bio-
lms as consortia and interact closely with
neighbouring species with complementary
The application of culture-
independent, molecular approaches has
identified about 1,200 different types
of microbe that can inhabit the human
However, any particular mouth
may contain only up to about 80 species,
although the application of more power-
ful and sensitive molecular approaches
will increase this number, as species that
are present only in low numbers will be
detected. The Human Oral Microbiome
project is underway and aims to identify
and characterise all members of the resi-
dent oral microora;
the conclusion of
these studies will permit a more accurate
description of what is the ‘normal oral
microora’. Information is being placed in
a publically accessible web-based Human
Oral Microbiome Database (http://www., which also feeds information
into the larger Human Microbiome project.
The normal oral microora is diverse
and varies in composition between sites
due to differences in the prevailing bio-
logical conditions.
The load on mucosal
sites is low due to desquamation. In con-
trast, teeth (being non-shedding surfaces)
potentially permit the accumulation of
large masses of bacteria and their prod-
ucts, especially at stagnant or ‘difcult-to-
reach’ areas, unless effective oral hygiene
is practised. The microbial composition of
oral biolms varies depending on the site
or surface, because local environmental
conditions dictate which organisms are
able to colonise, grow and be either major
or minor components of the established
microbial community. For example, the
bacteria found in occlusal ssures are
mainly Gram positive (especially strep-
tococci), are facultatively anaerobic and
metabolise host and dietary sugars, and
the site is affected by the properties of
saliva. In contrast, the biolms from the
healthy gingival crevice contain many
Gram negative and obligately anaerobic
species, that have a proteolytic style of
metabolism, and the community is inu-
enced by gingival crevicular uid (GCF), a
serum-like exudate.
Certain bacteria are
© 2012 Macmillan Publishers Limited. All rights reserved.
commonly found in high proportions at
healthy sites and can be regarded as part
of the core resident oral microora. These
include members of the bacterial genera:
Streptococcus, Actinomyces, Neisseria,
Haemophilus, Veillonella, Prevotella and
Fusobacterium, but the individual species
and their proportions may vary between
sites and between people.
One of the challenges in dening what
is ‘normal’ in terms of the resident oral
microora is that, traditionally, compari-
sons have been made from different stud-
ies of ‘lists’ of bacterial names. In diverse
biolms, such as those in the oral cavity,
this may not be an appropriate approach.
Within any microbial community, bacteria
will have a particular role or function (for
example, the catabolism of complex host
glycoproteins to individual sugars and
peptides; proteolysis of host proteins and
peptides to simpler peptides and amino
acids respectively; consumption of oxygen
to create a more anaerobic environment
etc). Organisms with different ‘names’
could carry out equivalent roles or activi-
ties, so that the denition and description
of the resident oral microora should be
based around functional characteristics
rather than simply by bacterial name.
The composition of the oral microora
can remain stable over time (microbial
This is not due to any bio-
logical indifference among the members
of the biolm community – the relation-
ship is not passive but highly dynamic.
Biofilm composition will respond to
changes in local environment (for exam-
ple, in saliva ow, status of host defences,
etc) and lifestyle (diet, smoking, etc). Such
changes can perturb biolm composition
and activity and predispose a site to dis-
ease. Oral diseases are generally associated
with shifts in the balance of the microora
at a site, so previously minor members
of the biolm become predominant, and
the overall metabolic activity of the bio-
lm changes.
Thus, in contrast to many
situations in medical microbiology, it is
too simplistic to talk of the presence of
‘good’ or ‘bad’ bacteria. Disease is a result
of undesirable changes to the microbial
balance, metabolism, and composition of
these dental biolms.
As we shall see, of clinical relevance
is the need to not only apply appropri-
ate plaque control strategies to reducing
dental disease, but to also try to identify
and remedy the factors that drive these
deleterious changes in the microbiologi-
cal composition and metabolism of these
Patients need to maintain plaque at levels
compatible with health in order to prevent
the breakdown of microbial homeostasis
which would increase the risk of disease. It
is inappropriate and futile for patients and
dental professionals to attempt to eliminate
plaque biolms; rather, patients should
be using effective oral hygiene practices,
combined with an appropriate lifestyle, to
try to control plaque at levels compatible
with health so as to maintain the benecial
properties of the resident oral microora,
and reduce the risk of disease. In peri-
odontitis, plaque control ‘thresholds’ that
are compatible with a health-promoting
biomass vary from patient-to-patient, with
some requiring extremely good plaque
control, while others manage with less
stringent regimes.
Dental diseases are associated with an
imbalance in the composition of the resi-
dent oral microora.
Disease is linked to
the presence of higher proportions of cer-
tain species that are normally only minor
components in the biolm. In dental car-
ies, demineralisation is associated with
increased proportions of mutans strepto-
cocci, lactobacilli and bidobacteria. The
virulence traits are relatively nonspecic
and centred around sugar metabolism,
such as the ability of these bacteria to
rapidly transport sugars into the cell and
metabolise them to acid, and then to sur-
vive and grow under the conditions of
low pH generated within the biolm (acid
tolerance). The ability to synthesise intra-
cellular and extracellular polysaccharides
from sucrose also plays a role in devel-
oping a cariogenic biolm. In gingivitis,
there is an increase in plaque mass, which
provokes an inammatory response by the
host. If unresolved, by-stander damage to
the periodontium can occur from an inap-
propriate and exaggerated host response
to subgingival bacteria and their metabo-
lites. Many of the implicated bacteria are
currently unculturable; others are Gram
negative, obligately anaerobic and highly
proteolytic. Virulence traits of these bac-
teria include the production of proteases,
cytotoxins and inammatory mediators.
Biolms can form on mucosal surfaces,
and substantial numbers of bacteria can be
found on the tongue. In some subjects, this
can result in halitosis, which is also linked
to the metabolism of obligately anaero-
bic, proteolytic bacteria resulting in the
production of volatile sulphur and other
malodorous compounds.
Evidence linking oral and general health
is accumulating, particularly with respect
to diabetes mellitus and cardiovascular
and respiratory diseases. Some studies
also report a weak positive association
between periodontal disease and adverse
pregnancy outcomes.
The hypothesis
behind the link between oral and general
health is that many oral bacteria act as
opportunistic pathogens, especially if they
enter the blood stream and reach sites not
normally accessible to them (including
heart valves and atheromatous plaques);
or if the host defences are compromised
and subgingival biolms in periodontal
disease contain bacteria which (a) express
inammatory cell surface components (for
example, lipopolysaccharide) and (b) shed
metabolites which induce prostaglandins
and inammatory mediators. The vascu-
lar nature of the periodontium means that
these pro-inammatory mediators can
affect distant sites in the body. Oral micro-
organisms may also give rise to aspira-
tion pneumonia in susceptible patients
as anaerobic bacteria from periodontal
pockets have been isolated from infected
This is another way in which effec-
tive oral hygiene can contribute to main-
taining the general health of an individual.
As discussed earlier, dental plaque prefer-
entially accumulates at stagnant sites on
teeth that many individuals nd difcult to
clean- these sites are also the most disease
susceptible. Mechanical plaque control can
be effective, but needs to be meticulous
and patients have to be highly motivated
and with an appropriate lifestyle (that is,
an appropriate diet, avoid smoking, etc).
Consequently, oral care products have
been formulated that contain antiplaque or
© 2012 Macmillan Publishers Limited. All rights reserved.
antimicrobial agents to augment conven-
tional mechanical plaque control activi-
ties and interfere with biolm composition
and metabolism, especially at sites that
are difcult to clean and are commonly
missed during self-performed mechanical
plaque control.
Antiplaque agents function by remov-
ing or disrupting biolms, or by prevent-
ing the formation of new biolm, without
necessarily killing the component micro-
organisms. In contrast, antimicrobial
agents inhibit the growth of (bacteriostatic
action) or kill (bactericidal action) micro-
organisms in oral biolms and are dened
in terms of the minimum inhibitory con-
centration (MIC) or minimum bactericidal
concentration (MBC) respectively.
activity of these agents can be against a
limited (narrow spectrum) or wider (broad
spectrum) target group of micro-organ-
isms. The mode of action of antimicrobial
agents is inuenced by their concentration
and the length of time they are in con-
tact with the target organisms. Typically,
the MIC/MBC of an agent is determined
in the laboratory on liquid grown (plank-
tonic) cells in tests where the agent is in
contact with a pure culture of the organ-
ism for prolonged periods (24-48+hours).
However, as discussed above, bacteria
growing on a surface as a biolm show
reduced sensitivity to killing by antimi-
crobial agents, especially in older (more
mature) biolms. Moreover, the maximum
length of time recommended for people
to brush their teeth is in the order of two
minutes, followed by ossing and rinsing
with a mouthwash for 30-60seconds. A
major requirement of the antiplaque for-
mulation, therefore, is to deliver sufcient
concentration of the active ingredients to
have an effect on the biolm in that short
period of time. Alternatively, the formula-
tion should ensure the prolonged retention
of the active components on dental and
mucosal surfaces in the mouth so that they
can be released over time at levels that will
still deliver biological activity.
An example of the pharmacokinetic
prole of a representative antimicrobial
agent delivered to the mouth from an oral
care product is shown in Figure1. There
are only short periods where the agent is
present at a high concentration (that is,
at concentrations greater than the MIC or
MBC) followed by longer periods where
the agent is present at sub-lethal levels.
This prole has a signicant inuence
on the mode of action of these agents.
Organisms reported to have an apparent
similar sensitivity to an antimicrobial
agent (as determined in a standard MIC
assay format under laboratory conditions)
can vary markedly in their susceptibil-
ity when exposed to the agent for only
relatively short periods, as occurs during
routine oral use; and sometimes favourable
selective inhibitory effects can be obtained.
For example, although displaying similar
MIC values against Triclosan, Gram nega-
tive obligately anaerobic bacteria impli-
cated in gingivitis and periodontal diseases
are more susceptible than the Gram posi-
tive bacteria (streptococci and Actinomyces
species) found in health when exposed to
this agent for only short periods.
Antimicrobial delivery
Time (hours)
Antimicrobial concentration
Fig. 1 Pharmacokinetics of antimicrobial agents delivered to the mouth.
A schematic
representation of the change in concentration over time following the delivery to the mouth on
two occasions of an antimicrobial agent from an oral care product. The agent may be present
above its MIC/MBC level for a relatively short period before it is lost from the mouth. The agent
may be present for longer at sub-lethal concentrations; agents may still exert benecial effects
by inhibiting traits associated with bacterial pathogenicity (see Table 1). The dynamics of the
curve will vary for each antimicrobial agent)
Table 1 Classes and examples of inhibitors used as antiplaque or antimicrobial agents
in mouthwashes and toothpastes, and their mode of action when present at sub-lethal
concentrations (see Fig. 1)
Class of inhibitor Example Antimicrobial action at sub-lethal concentrations*
Bisbiguanide Chlorhexidine**
Inhibits sugar transport and acid production
Inhibits amino acid uptake, polysaccharide synthesis
and bacterial membrane functions
Inhibits protease activity
Mutanase, dextranase,
glucose oxidase
Degrade bacterial polysaccharides that
make up plaque biolm matrix
Boosts salivary peroxidise system which
can inhibit bacterial glycolysis
Essential oil extracts
Menthol, thymol,
eucalyptol, methyl
salicylate **
Inhibit acid production and bacterial growth
Reduces lipopolysaccharide
Metal salts
Zinc, copper,
stannous ions
Inhibit sugar transport and acid production
Inhibit protease activity
Natural molecules
Plant extracts
(for example,
apigenin, tt-farnesol)
Inhibit acid production
Inhibit bacterial polysaccharide synthesis
Phenols Triclosan
Inhibit sugar transport and acid production
Inhibit protease activity
Quaternary ammonium
Sodium lauryl
sulphate, delmopinol
Damage cell membranes
Inhibit bacterial enzymes
Key *Some of these inhibitory actions will also inhibit metabolic activities involved in halitosis; **Generally delivered by mouthrinse;
compounds have yet to be incorporated into commercially-available oral care products
© 2012 Macmillan Publishers Limited. All rights reserved.
active agents used in oral care products
are able to exert a clinically relevant effect
when present below the MIC/MBC by
inhibiting the expression of virulence traits
by oral bacteria, such as sugar transport
mechanisms, acid production, extracellu-
lar polysaccharide synthesis and protease
activity (Table1).
In this way, small but
regular (for example, twice daily) subtle
and minor inhibitory effects on the plaque
biolm can:
• Reduce damage to oral and dental
tissues by inhibiting the expression of
virulence traits
• Suppress the competitiveness of some
of the putative pathogens by both
restricting their growth and denying
them the environment they need to
ourish (for example, acidic conditions
or presence of novel host proteins).
It has been shown that plaque biolms
need to be established for two days or
longer before the pH gradients following
sucrose metabolism fall below the critical
pH for enamel demineralisation,
that is,
thinner biolms are less damaging to the
host than thicker and more mature bio-
lms. Thus, the action of oral care prod-
ucts can help to preserve an appropriate
biolm structure and promote the stabil-
ity of the benecial resident microora
(microbial homeostasis).
It has been argued in this article that
the presence of biolms in the mouth is
both natural and is of benet to the host.
Therefore, there is a clear need to maintain
these benecial micro-organisms. Disease
is due to imbalances in the proportions
of this resident microora driven by del-
eterious changes in local environmental
conditions (the ecological plaque hypoth-
Briey, poor oral hygiene can
lead to an increase in plaque mass which,
when coupled with a substantial change
in environmental conditions in the mouth,
can affect the competitiveness of plaque
bacteria within the biolm, leading to
the enrichment of organisms most suited
to the altered environment and result in
a breakdown of microbial homeostasis
(Fig.2). In caries, an increased frequency
of sugar intake, or a reduction in saliva
ow, results in plaque biolms spend-
ing more time at low pH. This selects for
acid-producing and acid-tolerating spe-
cies (most commonly mutans streptococci,
but not exclusively so) at the expense of
health-associated bacteria that prefer pH
values around neutrality. Increases in
the acidogenic populations lead to even
more acid production and lower pH levels
within the biolm, which further disrupts
microbial homeostasis and promotes dem-
In gingivitis, the inam-
matory response to plaque accumulation
results in an increased ow of GCF which,
in addition to introducing components of
the host defences, also delivers host mol-
ecules such as haemoglobin and transfer-
rin that act as essential nutrients for many
of the obligately anaerobic and proteolytic
bacteria detected in higher proportions in
periodontal disease. The metabolism of the
subgingival microora makes the site more
anaerobic and the local pH increases due to
proteolysis. These environmental changes
drive the selection of the diverse microbial
• Poor oral hygiene
• Lifestyle risk factors
Normal development
of host physiology
Cardiovascular and
gastrointestinal benets
Resident oral
• Effective oral hygiene
• Effective and regular interventions
Increased plaque
Thinner biolm
Maintain benecal microbes
Caries risk
Suppression of
benecial bacteria
Gingivitis risk
Halitosis risk
Lower selective pressure
for oral ‘pathogens’
Less acid production,
reduced pH drop
from dietary sugars
Fewer obligate
Fig. 2 The relationship between the resident oral microora and the host in health and disease. The resident oral microora is important for the
normal development of many functions of the host in health, and contributes to the host defences (colonisation resistance). If plaque is allowed
to accumulate then the patient is at risk of caries, gingivitis or halitosis. Effective plaque control should maintain the oral microora at levels
that are compatible with health so as to retain the benecial properties of the resident oral microora, while minimising the risk of disease
© 2012 Macmillan Publishers Limited. All rights reserved.
consortia that are detected at inamed
A key principle of this hypothesis
is that disease can be treated not only by
(a) improving oral hygiene or (b) targeting
the putative pathogens directly, but also
by (c) interfering with the environmental
pressures that select for the pathogenic
Antimicrobial agents in
oral care products can play an important
role in all of these stages,
for example,
by killing some of the key bacteria and
by reducing (at sub-lethal concentrations)
the deleterious consequences to the host
associated with acid production
that create the selection
pressures for the overgrowth of putative
pathogens in oral biolms.
The stratagem for using antimicrobial
agents in oral care products, therefore,
is quite distinct to that when prescribing
antibiotics in clinical medicine. In cases of
the latter, high doses of antibiotic (prefer-
ably with a bactericidal mode of action)
are given for a xed period with the inten-
tion of eliminating a recognised pathogen,
often from a site that should be relatively
sterile. In oral care, antimicrobial agents
are delivered in over-the-counter prod-
ucts and used unsupervised, on a regular
basis, at a site with a resident and bene-
cial microora. Thus, it can be appreciated
that agents that work subtly but effec-
tively over long time periods to suppress
or restrict the growth and metabolism of
certain sections of the biolm consortium
may be ideal for the long-term control of
oral biolms. These oral care products help
preserve the natural microbial composi-
tion and activity, as well as the important
benecial functions, of our resident oral
microora (Fig.2), and in so doing, help
reconcile the paradoxes described at the
start of this article.
The author has received a fee from Johnson &
Johnson for writing this review article and in the
past has acted as a consultant to, and received
research grants from, several oral care companies.
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© 2012 Macmillan Publishers Limited. All rights reserved.
... The oral biofilm is naturally colonized by a plethora of microorganism which exists in a exceedingly dynamic relationship with the host [1] The breakdown of this symbiotic relationship (Dysbiosis) or apparently the shift from a mutualistic relationship to a parasitic one is the principle behind the various endogenous oral infections [2,3] . Dental caries and gingivitis are the commonly occurring plaque evoked dental disease which are mostly initiated in childhood and thus early prevention is of a great importance [4] . ...
... Efficient plaque control strategies should involve correct understanding of the structural and pathophysiological properties of the oral biofilm and identifythe factors responsible for the alteration of the existing microbial balance [5] . Also, the plaque biofilm should be maintained at levels compatible with oral health, focusing on maintaining helpful resident micro flora which can contribute to health, hence reducing the disease risk [1] . For decades the mechanical plaque control has been the conventional method of plaque control, which is mostly dependent on the cooperation, motivation, and patient compliance, hence certain chemical modalities such as use of antibiotics and antiplaque agents are used to augment its action to achieve desirable results [6] The chemical method of plaque control which interfere with the composition and metabolism of oral biofilm had certain drawbacks such as increasing antimicrobial resistance, disrupting the stability of beneficial micro flora hence increase in the number of exogenous microorganisms [7] . ...
Introduction: The probiotics have the ability to modulate or influence the micro flora in a beneficial way leading to its increased use in various areas of healthcare. It provides a more natural and a non-invasive solution for management of commonly occurring oral diseases. Aim & Objectives: To clinically evaluate and compare the efficacy of probiotic and chlorhexidine mouthrinses on plaque and gingival inflammation in children. Materials and Method: The trial design was randomized parallel group study comprised of 60 healthy children of age group of 6-9 years. The subjects were assigned into three groups (A- control, Bchlorhexidine, C- probiotic). Plaque index and gingival index levels were recorded at baseline, 3rd day and 14th day. Results: The Probiotic and chlorhexidine group had less plaque and gingival accumulation at the end of 14th day. There was significant difference in the plaque as well as gingival index between the chlorhexidine and probiotic group, probiotic group, being better than the chlorhexidine (mean value: 0.86±0.24 and 0.66±0.14) p<0.05 respectively. Conclusion: Probiotic mouth rinse was found effective in reducing plaque accumulation as well as gingival inflammation. Hence, Probiotic mouth rinses have shown promising potential as an alternative effective and potentially safe anti-plaque agent in comparison to chlorhexidine.
... 4 A traditional method and a consensus to decrease dental calculus and microbiological plaque at the level of gingival margins are manual or ultrasonic debridement of root surfaces. 5 However, in the case of fixed orthodontic appliances, efficient cleaning becomes a daunting task. Therefore, it is imperative to practice comprehensive oral hygiene measures, including professional removal of dental plaque using ultrasonic scalers along with adjunctive chemical agents such as chlorhexidine mouthwashes. ...
Objective: To assess the efficiency of photodynamic therapy (PDT) adjunct to full mouth scaling (FMS) in improving periodontal, microbiological, and proinflammatory cytokines levels in patients undergoing fixed orthodontics treatment (FOT). Materials and methods: The study recruited 60 teenage patients who were undergoing FOT. All the patients were arbitrarily divided into two groups: Group 1, FMS +PDT and Group 2, FMS alone. Plaque scores (PS), bleeding on probing (BOP), and probing depth (PD) were assessed. Levels of biomarkers interleukin (IL)-6 and tumor necrosis factor-alpha (TNF-α) using enzyme-linked immunosorbent assay were evaluated. Samples were collected from gingival plaque for estimation of Prevotella intermedia and Porphyromonas gingivalis load. All measurements were completed at three intervals baseline, 4th week, and 8th week. Post Hoc corrections and intergroup comparisons were examined using Student's t-test and Bonferroni correction. To find differences between repeated follow-ups, analysis of variance (ANOVA) multiple rank tests were used. Results: At baseline, all the gingival parameters displayed comparable outcomes between patients of Group 1 and Group 2 (p > 0.05). However, at 4 and 8 weeks of follow-up, PS and BOP among tested groups exhibited significantly lower values than baseline (p < 0.001). At 8 weeks, there was a significant difference in PS between the two groups tested. Moreover, at 4 and 8 weeks, BOP revealed a significant difference between the groups. PD remains comparable with baseline at follow-up visits (p > 0.05). A significant decrease in IL-6 and TNF-α levels was observed in both investigated groups at 4 and 8 weeks of baseline. Moreover, it was identified that P. intermedia and P. gingivalis were reduced significantly at 4 weeks. Moreover, a significant difference existed between both Group 1 and Group 2 at 4 and 8 weeks of recall visit (p < 0.05). Conclusions: The use of photodynamic treatment adjuvant to FMS aids in improving periodontal parameters and cytokines levels.
... Dental biofilm is an important etiological factor of dental caries. Consequently, mechanical removal by brushing associated with fluoride toothpaste and lower sugar consumption are the traditional methods for controlling and preventing this disease [2]. However, tooth brushing effectiveness depends on the individual's motor ability and sometimes requires adjunctive therapies, such as the chemical control of dental biofilm [3]. ...
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The synergic effect of Streptococcus mutans and Candida albicans increases dental caries severity. Antimicrobial photodynamic therapy (aPDT) is a non-invasive treatment for antimicrobial aspects. However, the current photosensitizers (PS) have many downsides for dental applications. This study aimed to evaluate the efficiency of two different Brazilian green propolis (BGP-AF and BGP-AG) as PS for aPDT against these microorganisms. A single-species biofilm was irradiated with crude extracts and their fractions and controls. Such extracts showed the best results and were evaluated in dual-species biofilms. Photodegradation, reactive oxygen species (ROS), cytotoxicity, and color stability assays were also investigated. Reductions higher than 3 log10 CFU/mL (p < 0.0001) occurred for crude BGP in single- and dual-species biofilms. Singlet oxygen was produced in BGP (p < 0.0001). BGP-mediated aPDT delayed S. mutans and C. albicans regrowth after 24 h of treatment (p < 0.0001). Both BGP did not change the color of dental materials (p > 0.05). BGP-AF-mediated aPDT showed 72.41% of oral keratinocyte viability (p < 0.0001). BGP extracts may be used in aPDT against S. mutans and C. albicans. Specifically, BGP-AF may represent a promising PS for dental applications.
... Nevertheless, patients' efforts to maintain good biofilm control are often hampered by the difficulty of accessing interdental areas and gingival margins [6]. Antimicrobial mouthrinses complement mechanical oral hygiene regimens by improving biofilm removal [7][8][9]. ...
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Abstract Background The efficacy of mouth-rinses strongly depends upon their substantivity. The use of natural and non-toxic products that avoid secondary effects is gaining interest in preventive dentistry. The purpose of this study was to evaluate the substantivity of two formulations of mouth-washing solutions based on cetylpyridinium (CPC) and O-cymen-5-ol. Methods This was a randomized, double-blind, crossover trial conducted at the Faculty of Medicine and Health Sciences of the University of Barcelona. Bacterial re-colonization was followed by live/dead (SYTOTM9 + propidium iodide) bacterial staining and measured by confocal laser scanning microscopy and fluorometry. Unstimulated saliva samples were collected from 16 healthy individuals at baseline saliva and then, at 15 min, 30 min and 1, 2, 3, and 4 h after the following mouth-rinses: (i) a single, 1-min mouth-rinse with 15 ml of placebo (negative control); (ii) a single, 1-min mouth-rinse with 15 ml of CPC (0.05%) ; (iii) a single, 1-min mouth-rinse with 15 ml of O-cymen-5-ol (0.09%); (iv) a single, 1-min mouth-rinse with 15 ml of CPC (0.05%) + O-cymen-5-ol (0.09%). Results Proportion of dead bacteria was significantly higher for all mouthrinses during the first 15 min compared to baseline (CPC = 48.0 ± 13.9; 95% CI 40.98–56.99; p
... The accumulation of abundant Gram-negative species (e.g., Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, and Actinomyces actinomycetemcomitans) below the gingival margin may cause a detrimental host inflammatory-immune response, representing the most important risk factor for periodontitis [4]. So, the mechanical control of supra-gingival plaque represents one of the main goals of preventive dentistry and oral hygiene motivation and the efficacy of therapeutic instruments plays a key role in the daily domiciliary mechanical plaque control [4][5][6][7][8]. ...
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Plaque biofilm is considered one of the etiological factors involved in the onset of caries and gingivitis, and is associated with the progression of periodontitis and peri-implant inflammation. There is no agreement in the literature on the effectiveness of the oscillating-rotating (OR) powered toothbrush (PTB) and high-frequency sonic (HFS) PTB in improving oral health. Thus, using the present proof-of-concept study we aimed to evaluate the effectiveness of OR PTB versus HFS PTB in terms of the improvement in plaque, gingival inflammation, and lingual patina indexes in dental hygiene university students. Dental hygiene students from the University of Eastern Piedmont “A. Avogadro” of Novara, Italy from November 2019 to October 2021 were recruited. Based on the type of toothbrush previously used for at-home plaque removal, the study participants were divided into two groups: Group 1 (subjects that used MTB prior to the study beginning, asked to use OR PTB for 2 times/day for a minimum of 3 months) and Group 2 (subjects that used HFS PTB prior to the study beginning). All the participants were instructed to avoid floss aids during the study (i.e., pipe cleaners, dental floss, and mouthwash). The outcome measures were: New Method of Plaque Scoring (NMPS), simplified Oral Disease Index (OHI-S), Plaque Control Record (PCR), Gingival Bleeding Index, and Winkel Tongue Coating Index (WTCI). All the outcomes were assessed at baseline (T0) in both groups and after 3 months (T1) in Group 1. Fifty-seven subjects (44 females and 13 males) were included and allocated to the study group (n = 30, 22 females and 8 males) and control group (n = 27, 22 females and 5 males). At T0, all the indexes were significantly higher in Group 2 (p < 0.0001). At T1, NMPS, OHI-S, PCR, GBI, and WTCI were statistically improved in Group 1 (p < 0.0001). Lastly, there was a statistically significant difference between Group 1 at T1 and Group 2 at T0 in terms of NMPS (p = 0.043), OHI-S (p = 0.032), and PCR (p < 0.001). Taken together, the findings of this proof-of-concept study showed the effectiveness over a 3-month period of both oscillating-rotating and sonic PTB in terms of oral health status in a sample of dental hygiene students.
... They can be broadly divided into plaque removal and topical application of remineralizing agents [1]. To control dental plaque, antibacterial compounds such as chlorhexidine (CHX; 0.2%) and cetylpyridinium chloride can be used [5][6][7][8][9]. Mechanical plaque control can be achieved with tooth brushing, professional tooth cleaning, and flossing [10][11][12]. ...
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Toothpastes and mouth rinses contain fluoride as a protective agent against caries. The aim of this study was to determine the degree of fluoride-uptake by human tooth mineral during immersion into fluoride-containing aqueous solutions as different pH. Human teeth were immersed in fluoride-containing solutions to assess the extent of fluoride incorporation into tooth enamel. A total of 16 extracted teeth from 11 patients were immersed at 37 °C for one minute into aqueous fluoride solutions (potassium fluoride; KF) containing either 250 ppm or 18,998 ppm fluoride (1-molar). Fluoride was dissolved either in pure water (neutral pH) or in a citrate buffer (pH 4.6 to 4.7). The elemental surface composition of each tooth was studied by energy-dispersive X-ray spectroscopy in combination with scanning electron microscopy and X-ray powder diffraction. The as-received teeth contained 0.17 ± 0.16 wt% fluoride on average. There was no significant increase in the fluoride content after immersion in 250 ppm fluoride solution at neutral or acidic pH values. In contrast, a treatment with a 1-molar fluoride solution led to significantly increased fluoride concentrations by 0.68 wt% in water and 9.06 wt% at pH 4.7. Although such fluoride concentrations are far above those used in mouth rinses or toothpastes, this indicates that fluoride can indeed enter the tooth surface, especially at a low pH where a dynamic dissolution-reprecipitation process may occur. However, precipitations of calcium fluoride (globuli) were detected in no cases.
The oral microbiome delivers important benefits to the host (symbiosis). Changes to the oral environment drive deleterious shifts in this microbiome (dysbiosis). Low biofilm pH from dietary sugar catabolism selects for acidogenic/acid-tolerating species and promotes dental caries, while inflammation following biofilm accumulation enriches for the proteolytic and anaerobic microbial communities associated with periodontal disease. Prevention depends not only on biofilm control but also on eliminating drivers of dysbiosis, i.e., an ecological approach to disease prevention.
The review of the literature considers the current understanding of scientists about the risk factors for the development of diseases of hard dental tissues in children. Dental caries is an important social problem of childhood in all countries of the world. The worldwide prevalence of this disease ranges from 25 % to 72 %. While, according to the WHO, the frequency and intensity of dental caries in children have been declining in a number of countries in recent decades, in Ukraine these rates remain high and tend to increase. Caries of temporary teeth ranks tenth among the most common diseases in the world. It is a multifactorial, diet-associated dental disease manifested by foci of demineralization. The etiology and pathogenesis of dental nosology are well studied and known. Despite this, tooth caries remains an important social problem among children in all countries of the world, and is often accompanied by serious impacts on the health of children and their families.
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The long-term survival of restorations in the oral cavity has always been one of the most significant challenges in modern dental practice [...]
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The mouth contains both distinct mucosal (lips, cheek, tongue, palate) and, uniquely, non-shedding surfaces (teeth) for microbial colonisation. Each surface harbours a diverse but characteristic microflora, the composition and metabolism of which is dictated by the biological properties of each site. The resident oral microflora develops in an orderly manner via waves of microbial succession (both autogenic and allogenic). Pioneer species (many of which are sIgA protease-producing streptococci) colonise saliva-coated surfaces through specific stereo-chemical, adhesin-receptor interactions. The metabolism of these organisms modifies local environmental conditions, facilitating subsequent attachment and growth by later, and more fastidious, colonisers. Eventually, a stable biofilm community develops, that plays an active role in (a) the normal development of the physiology of the habitat, and (b) the innate host defences (colonisation resistance). Thus, when considering treatment options, clinicians should be aware of the need to maintain the beneficial properties of the resident oral microflora.
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The human oral cavity contains a number of different habitats, including the teeth, gingival sulcus, tongue, cheeks, hard and soft palates, and tonsils, which are colonized by bacteria. The oral microbiome is comprised of over 600 prevalent taxa at the species level, with distinct subsets predominating at different habitats. The oral microbiome has been extensively characterized by cultivation and culture-independent molecular methods such as 16S rRNA cloning. Unfortunately, the vast majority of unnamed oral taxa are referenced by clone numbers or 16S rRNA GenBank accession numbers, often without taxonomic anchors. The first aim of this research was to collect 16S rRNA gene sequences into a curated phylogeny-based database, the Human Oral Microbiome Database (HOMD), and make it web accessible ( The HOMD includes 619 taxa in 13 phyla, as follows: Actinobacteria, Bacteroidetes, Chlamydiae, Chloroflexi, Euryarchaeota, Firmicutes, Fusobacteria, Proteobacteria, Spirochaetes, SR1, Synergistetes, Tenericutes, and TM7. The second aim was to analyze 36,043 16S rRNA gene clones isolated from studies of the oral microbiota to determine the relative abundance of taxa and identify novel candidate taxa. The analysis identified 1,179 taxa, of which 24% were named, 8% were cultivated but unnamed, and 68% were uncultivated phylotypes. Upon validation, 434 novel, nonsingleton taxa will be added to the HOMD. The number of taxa needed to account for 90%, 95%, or 99% of the clones examined is 259, 413, and 875, respectively. The HOMD is the first curated description of a human-associated microbiome and provides tools for use in understanding the role of the microbiome in health and disease.
For more than ten years, interdental plaque-pH telemetry has been used in Switzerland to investigate the in vivo acidogenicity and acid clearance time of confec- tionery, food, beverages and medicines. The measurements are routinely done in adults. For this study, telemetry devices were built into space maintainers of two seven- year-old children and o( a (ourteen-year-old boy. The pH- changes in the interdental plaque of these voluntkers recorded after oral administration of dietary carbohy- drates were in agreement with the results routinely found in adults. In both age groups, immediate, pronounced a~d long lasting pH-falls were recorded under undisturbed layers of plaque at the level of the enamel surface.
Recent studies surprisingly show that dietary inorganic nitrate, abundant in vegetables, can be metabolized in vivo to form nitrite and then bioactive nitric oxide. A reduction in blood pressure was recently noted in healthy volunteers after dietary supplementation with nitrate; an effect consistent with formation of vasodilatory nitric oxide. Oral bacteria have been suggested to play a role in bioactivation of nitrate by first reducing it to the more reactive anion nitrite. In a cross-over designed study in seven healthy volunteers we examined the effects of a commercially available chlorhexidine-containing antibacterial mouthwash on salivary and plasma levels of nitrite measured after an oral intake of sodium nitrate (10mg/kg dissolved in water). In the control situation the salivary and plasma levels of nitrate and nitrite increased greatly after the nitrate load. Rinsing the mouth with the antibacterial mouthwash prior to the nitrate load had no effect on nitrate accumulation in saliva or plasma but abolished its conversion to nitrite in saliva and markedly attenuated the rise in plasma nitrite. We conclude that the acute increase in plasma nitrite seen after a nitrate load is critically dependent on nitrate reduction in the oral cavity by commensal bacteria. The removal of these bacteria with an antibacterial mouthwash will very likely attenuate the NO-dependent biological effects of dietary nitrate.
The aim of this article is to review the properties of compounds available for the control of dental plaque biofilms, and describe their mode of action. The mouth is colonised by a diverse but characteristic collection of micro-organisms, which confer benefit to host. Numerous antiplaque (e.g. surfactants, essential oils) and antimicrobial agents (e.g. bisbiguanides, metal ions, phenols, quaternary ammonium compounds, etc.) have been successfully formulated into toothpastes and mouthrinses to control plaque biofilms. At high concentrations, these agents can remove biofilm and/or kill disease-associated bacteria, while even at sub-lethal levels they can inhibit the expression of pathogenic traits. Successful antimicrobial agents are able to meet the apparently contradictory requirements of maintaining the oral biofilm at levels compatible with oral health but without disrupting the natural and beneficial properties of the resident oral microflora.
Only around half of oral bacteria can be grown in the laboratory using conventional culture methods. Molecular methods based on 16S rRNA gene sequence are now available and are being used to characterize the periodontal microbiota in its entirety. This review describes the cultural characterization of the oral and periodontal microbiotas and explores the influence of the additional data now available from culture-independent molecular analyses on current thinking on the role of bacteria in periodontitis. Culture-independent molecular analysis of the periodontal microbiota has shown it to be far more diverse than previously thought. A number of species including some that have yet to be cultured are as strongly associated with disease as those organisms traditionally regarded as periodontal pathogens. Sequencing of bacterial genomes has revealed a high degree of intra-specific genetic diversity. The use of molecular methods for the characterization of the periodontal microbiome has greatly expanded the range of bacterial species known to colonize this habitat. Understanding the interactions between the human host and its commensal bacterial community at the functional level is a priority.