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R eview Article www.ejournalofdentistry.com

DENTAL PLAQUE..........UNVEILING THE BIOFILM INSIDE

ABSTRACT

Dental plaque is the diverse microbial community, embedded in a matrix of host and bacterial polymers, growing on teeth

as a biofilm. Dental plaque develops naturally, and contributes to the host defences by preventing colonization by

exogenous species. The composition of dental plaque varies at distinct surfaces as a result of the inherent biological

and physical properties at these sites; the balance of the predominant bacterial populations shifts in disease. Bacteria

growing on a surface display a novel phenotype; one consequence of which is an increased resistance to antimicrobial

agents. Such biofilm-associated traits, affect the mode of action and efficacy of antimicrobials. Agents with a broadspectrum of activity in laboratory studies may display a far narrower inhibitory profile in the mouth. This may result in

a selective inhibition of species implicated in disease, or reduced production of virulence factors, while preserving the

benefits associated with a resident oral microflora.

Key Words: Dental plaque, open architecture, diffusion reaction theory, selective inhibition.

Changing Views of Dental Plaque

Over the past 50 years, the understanding and

characterization of dental plaque have undergone

significant evolution. Loesche6 proposed both a

nonspecific and a specific plaque hypothesis for periodontal

disease initiation and progression. The nonspecific plaquehypothesis proposed that the entire microbial community

of plaque that accumulated on tooth surfaces and in the

gingival crevice contributed to the development of

periodontal disease. Plaque bacteria produced virulence

factors and noxious products that initiated inflammation,

challenged the host defence system, and resulted in the

destruction of periodontal tissues. Under this hypothesis,

the quantity of plaque was considered to be the critical

factor in the development of periodontal disease. Thus,

increases in the amount of plaque (quantity), as opposed

to specific pathogenic microorganisms (quality) found in

the plaque, were viewed as being primarily responsible for

inducing disease and disease progression7,8. Studies on

the microbial aetiology of various forms of periodontitis

support the specific plaque hypothesis, which proposes

that only certain microorganisms within the plaque complex

are pathogenic. Despite the presence of hundreds of

species of microorganisms in periodontal pockets, fewer

than 20 are routinely found in increased proportions at

per iodontally diseased sites. These specific virulent

bact er ial species act ivate th e hosts immun e an d

inflammatory responses that then cause bone and soft

tissue destruction 6,8,9. Socransky and colleagues4,10

recognized that early plaque consists predominantly of

gram-positive organisms and that if the plaque is left

undisturbed it undergoes a process of maturation resulting

in a more complex and predominantly gram-negative flora.

These investigators assigned the organisms of the

subgingival microbiota into groups, or complexes, based

on their association with health and various disease

severities4,10. Colour designations were used to denote the

association of particular bacterial complexes with

periodontal infections. The blue, yellow, green, and purple

complexes designate early colonizers of the subgingival

flora. Orange and red complexes reflect late colonizers

associated with mature subgingival plaque. Certain bacterial

complexes are associated with health or disease10,11. For

example, the bacteria in the red complex are more likely to

be associated with clinical indicators of periodontal diseasesuch as periodontal pocketing and clinical attachment loss.

Plaque Recognized as a Biofilm (Table: 1)

Research over the past decade has led to the recognition

of dental plaque as a biofilm - a highly organized

accumulation of microbial communities attached to an

environmental surface. Biofilms are organized to maximize

Shantipriya Reddy Professor and Head, Sanjay Kaul Professor,Prasad MGS Reader, Hrishikesh Asutkar

Postgraduate student, Nirjhar Bhowmik Postgraduate student, Jaya Senior Lecturer, Departmentof Periodontics,Dr. Syamala Reddy Dental College, Hospital and Research Center, Bengaluru, Karnataka, India.

Correspondence: Nirjhar Bhowmik, Postgraduate student, Department of Periodontics, Dr. Syamala Reddy Dental College, Hospitaland Research Center, Bengaluru, Karnataka, India. E-mail: nirbhowmik@yahoo.co.in

Received Feb 08, 2012; Revised Mar 13, 2012; Accepted Mar 24, 2012

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energy, spatial arrangements, communication, and

continuity of the community of microorganisms. Biofilms

protect bacteria living within their structures and thereby

provide an advantage over free-fl oating (planktonic)

bacteria. The slimy extracellular matrix produced by biofilm

bacteria encloses the microbial community and protects it

from the surrounding environment, including attacks fromchemotherapeutic agents. Chemotherapeutic agents have

difficulty penetrating the polysaccharide matrix to reach

and affect the microorganisms1, 11-13. Thus, the matrix helps

to protect bacteria deep within the biofilm from antibiotics

and antiseptics, increasing the likelihood of the colonies

survival. Furthermore, the extracellular matrix keeps the

bacteria banded together, so they are not flushed away by

the action of saliva and gingival crevicular fluid. Mechanical

methods, including toothbrushing, interdental cleaning, and

professional scaling procedures, are required to regularly

and effectively disrupt and remove the plaque biofilm.

Antiseptics, such as mouthrinses, can help to control the

biofilm but must be formulated so as to be able to penetratethe plaque matrix and gain access to the pathogenic bacteria.

Biofilms have a definite architectural structure. The bacteria

are not uniformly distributed throughout the biofilm; rather,

there are aggregates of microcolonies that vary in shape

and size. Channels between the colonies allow for

circulation of nutrients and by-products and provide a

system to eliminate wastes14, 15. Microorganisms on the

outer surface of biofilms are not as strongly attached within

the matrix and tend to grow faster than those bacteria deeper

within the biofilm. Surface microorganisms are more

susceptible to detachment, a characteristic that facilitates

travel to form new biofilm colonies on nearby oral structures

and tissues. Bacteria in biofilm communicate with each other

by a process cal led quorum sensin g. This dynamic,

sophisticated communication system enables bacteria to

monitor each others presence and to modulate their gene

expression in response to the number of bacteria in a given

area of the biofilm8. In addition, as a result of quorum

sensing, portions of the biofilm can become detached in

order to maintain a cell density compatible with continued

survival.

Stages of Biofilm Formation

The growth and development of biofilm are characterized

by 4 stages: initial adherence, lag phase, rapid growth, and

steady state. Biofilm formation begins with the adherence

of bacteria to a tooth surface, followed by a lag phase in

which changes in genetic expression (phenotypic shifts)

occur. A period of rapid growth then occurs, and an

exopolysaccharide matrix is produced. During the steady

state, the biofilm reaches growth equilibrium. Surface

detachment and sloughing occur, and new bacteria are

acquired.

Initial Adherence and Lag Phase

The first phase of supragingival biofilm formation is the

deposition of salivary components, known as acquired

pellicle, on tooth surfaces. This pellicle makes the surface

receptive to colonization by specific bacteria. Salivary

glands produce a variety of proteins and peptides thatfurther contribute to biofilm formation. For example, salivary

mucins, such as MUC5B and MUC7, contribute to the

formation of acquired pellicle16, 17, and statherin, a salivary

acidic phosphoprotein, and proline-rich proteins promote

bacterial adhesion to tooth surfaces18. Acquired pellicle

formation begins within minutes of a professional

prophylaxis; within 1 hour, microorganisms attach to the

pell icle. Usual ly, gram-posit ive cocci ar e the fi rst

microorganisms to colonize the teeth. As bacteria shift from

planktonic to sessile life, a phenotypic change in the bacteria

occurs requiring significant genetic up-regulation (gene

signaling that promotes this shift). As genetic expression

shifts, there is a lag in bacterial growth.

Rapid Growth

During the rapid growth stage, adherent bacteria secrete

large amounts of water-insoluble extracellular

polysaccharides to form the biofilm matrix. The growth of

microcolonies within the matrix occurs. With time, additional

varieties of bacteria adhere to the early colonizers - a

process known as coaggr ega tion an d th e bacterial

complexity of the biofilm increases. These processes involve

unique, selective molecular interactions leading to structural

stratification within the biofilm. Coaggregation and

subsequent cell division also increase the thickness ofbiofilm19-21.

Steady State/Detachment

During the steady state phase, bacteria in the interior of

biofilms slow their growth or become static. Bacteria deep

within the biofilm show signs of death with disrupted

bacterial cells and other cells devoid of cytoplasm; bacteria

near the surface remain intact. During this phase, crystals

can be observed in the interbacterial matrix that may

represent initial calculus mineralization22. As noted above,

during the steady state stage, surface detachment and

sloughing also occur, with some bacteria travelling to formnew biofilm colonies.

Biofilm Structure

Extracellular Polymeric Substances

Biofilms are composed primarily of microbial cells and EPS.

EPS may account for 50% to 90% of the total organic carbon

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of biofilms23 and can be considered the primary matrix

material of the biofilm. EPS may vary in chemical and

physica l properties, but it is pr imari ly composed of

polysaccharides. Some of these polysaccharides are neutral

or polyanionic, as is the case for the EPS of gram-negative

bacteria. The presence of uronic acids (such as D-

glucuronic, D-galacturonic, and mannuronic acids) or ketal-linked pryruvates confers the anionic property24. This

proper ty is impor tant because it allows association of

divalent cations such as calcium and magnesium, which

have been shown to cross-link with the polymer strands

and provide greater binding force in a developed biofilm23.

In the case of some gram-positive bacteria, such as the

staphylococci, the chemical composition of EPS may be

quite different and may be primarily cationic. Hussain et

al25, found that the slime of coagulase-negative bacteria

consists of a teichoic acid mixed with small quantities of

proteins. EPS is also highly hydrated because it can

incorporate large amounts of water into its structure by

hydrogen bonding. EPS may be hydrophobic, althoughmost types of EPS are both hydrophilic and hydrophobic24.

EPS may also vary in its solubility. Sutherland24 noted two

important properties of EPS that may have a marked effect

on the biofilm. First, the composition and structure of the

polysaccharides determine their primary conformation. For

example, many bacterial EPS possess backbone structures

that contain 1,3- or 1,4--linked hexose residues and tend

to be more rigid, less deformable, and in certain cases poorly

soluble or insoluble. Other EPS molecules may be readily

soluble in water. Second, the EPS of biofilms is not generally

uniform but may vary spatially and temporally. Leriche26 et

al. used the binding specificity of lectins to simple sugars

to evaluate bacterial biofilm development by different

organisms. These researchers results showed that different

organisms produce differing amounts of EPS and that the

amount of EPS increases with age of the biofilm.EPS may

associate with metal ions, divalent cations, other

macromolecules (such as proteins, DNA, lipids, and even

humic substances)23. EPS production is known to be

affected by nutrient status of the growth medium; excess

available carbon and limitation of nitrogen, potassium, or

phosphate promote EPS synthesis24. Slow bacterial growth

will also enhance EPS production24 because EPS is highly

hydrated, it prevents desiccation in some natural biofilms.

EPS may also contribute to the antimicrobial resistanceproperties of biofilms by impeding the mass transport of

antibiotics through the biofilm, probably by binding directly

to these agents27.

Biofilm Architecture

Tolker-Nielsen and Molin noted that every microbial biofilm

community is unique28 although some structural attributes

can generally be considered universal. The term biofilm is

in some ways a misnomer, since biofilms are not a

continuous monolayer surface deposit. Rather, biofilms are

very heterogeneous, containing microcolonies of bacterial

cells encased in an EPS matrix and separated from other

microcolonies by interstitial voids (water channels). Liquid

flow occurs in these water channels, allowing diffusion ofnutrients, oxygen, and even antimicrobial agents. This

concept of heterogeneity is descriptive not only for mixed

culture biofilms (such as might be found in environmental

biofilms) but also for pure culture biofilms common on

medical devices and those associated with infectious

diseases. Stoodleyet al. defined certain criteria or

characteristics that could be considered descriptive of

biofilms in general, including a thin base film, ranging from

a patchy monolayer of cells to a film several layers thick

containing water channels29. The organisms composing the

biofilm may also have a marked effect on the biofilm

structure. For example, James et al showed that biofilm

thickness could be affected by the number of componentorganisms. Pure cultures of either K. pneumoniae or P.

aeruginosa biofilms in a laboratory reactor were thinner (15

and 30 respectively), whereas a biofilm containing both

species was thicker (40 ). Jones et al. noted that this could

be because one species enhanced the stability of the other.

Biofilm architecture is heterogeneous both in space and

time, constantly changing because of external and internal

processes. Tolker-Nielsen et al.32 investigated the role of

cell motility in biofilm architecture in flow cells by examining

the interactions of P. aeruginosa and P. putida by confocal

laser scanning microscopy. When these two organisms were

added to the flow cell system, each organism initially formed

small microcolonies. With time, the colonies intermixed,

showing the migration of cells from one microcolony to the

other. The microcolony structure changed from a compact

structure to a looser structure over time, and when this

occurred the cells inside the microcolonies were observed

to be motile. Motile cells ultimately dispersed from the

biofilm, resulting in dissolution of the microcolony.

Biofilm and Oral Disease

Biofilms can cover surfaces throughout the oral cavity.

Microcolonies exist on oral mucosa, the tongue,

biomaterials used for restorations and dental appliances,

and tooth surfaces above and below the gingival margin. It

is important for oral health professionals to communicate

to their patients that both dental caries and periodontal

disease are infectious diseases resulting from dental plaque

biofilm accumulation. Each of these diseases requires

specific strategies for prevention and treatment. With

respect to periodontal disease, dental plaque biofilm

demonstrates a succession of microbial colonization with

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changes in bacterial flora observed from health to disease.

Bacterial species contained in the yellow, green, and purple

complexes appear to colonize the subgingival sulcus first

and predominate in gingival health. In contrast, orange

complex bacteria are associated with gingivitis and gingival

bleeding. Interestingly, bacteria of the orange complex may

also be associated with red complex microorganismsincluding Porphyromonas gingivalis, Tannerella

forsythensis, and Treponema denticola, organisms found

in greater numbers in diseased sites and in more advanced

periodontal disease. As the biofilm matures and proliferates,

soluble compounds produced by pathogenic bacteria

penetrate the sulcular epithel ium. These compounds

stimulate host cells to produce chemical mediators

associated with the inflammatory process; Interleukin-1 beta

(IL-1 ), prostaglandins, tumor necrosis factor alpha (TNF-

), and matrix metalloproteinases are mediators that recruit

neutrophils to the area via chemotaxis and cause increased

permeability of gingival blood vessels, permitting plasma

proteins to migrate from within the blood vessels into thetissue. As the gingival inflammatory process continues,

additional mediators are produced, and more inflammatory

cell types such as neutrophils, T cells, and monocytes are

recruited to the area. Proinflammatory cytokines are

produced in the tissues as a response to the chronic

inflammatory process, and these proteins may further

escalate the local inflammatory response and affect the

initiation and progression of systemic inflammation and

disease. The result of this chronic inflammation is a

breakdown of gingival collagen and accumulation of an

inflammatory infiltrate, leading to the clinical signs of

gingivitis. In some individuals, the inflammatory process

will also lead to the breakdown of collagen in the periodontal

ligament and resorption of the supporting alveolar bone. It

is at this point that the lesion progresses from gingivitis to

peri odonti tis, con tinu ing the same chal lenge from

proinflammatory mediators as with chronic gingivitis. Thus,

controlling dental plaque biofilm is essential to preventing

and reversing gingivitis as well as preventing and managing

periodontitis.

The Established Community: Biofilm Ecology

The basic structural unit of the biofilm is the microcolony.

Proximity of cells within the microcolony (or between

microcolonies) provides an ideal environment for creation

of nutrient gradients, exchange of genes, and quorum

sensing. Since microcolonies may be composed of multiple

species, the cycling of various nutrients (e.g., nitrogen,

sulfur, and carbon) through redox reactions can readily

occur in aquatic and soil biofilms. The primary colonizers

which are gram positive organisms are facultative

anaerobes in nature and they make the environment

conducive for the late colonizers. It has been proposed

that as a microbial biofilm develops the community will

ultimately form a more stable climax community. As the

community is able to adapt appropriately to outside

perturbations the term microbial homeostasis has been

suggested to reflect stability within a climax community.

Gene Transfer

Biofilms also provide an ideal niche for the exchange of

extra-chromosomal DNA (plasmids). Conjugation (the

mechanism of plasmid transfer) occurs at a greater rate

between cells in biofilms than between planktonic cells35-

37. Ghigo38 has suggested that medically relevant strains of

bacteria that contain conjugative plasmids more readily

develop biofilms. He showed that the F conjugative pilus

(encoded by the tra operon of the F plasmid) acts as an

adhesion factor for both cell-surface and cell-cell

interactions, resulting in a three dimensional biofilm of

Escherichia coli. Plasmid-carrying strains have also beenshown to transfer plasmids to recipient organisms, resulting

in biofilm formation; without plasmids these same organisms

pr oduc e on ly mic rocolon ie s wi thou t an y further

development. The probable reason for enhanced

conjugation is that the biofilm environment provides

minimal shear and closer cell-to-cell contact. Since plasmids

may encode for resistance to multiple antimicrobial agents,

biofilm association also provides a mechanism for selecting

for, and promoting the spread of, bacterial resistance to

antimicrobial agents.

Quorum Sensing

Cell-to-cell signalling has recently been demonstrated to

play a role in cell attachment and detachment from biofilms.

Xie et al.39showed that certain dental plaque bacteria can

modulate expression of the genes encoding fimbrial

expression (fimA) in Porphyromonas gingivalis. P. gingivalis

would not attach to Streptococcus cristatis biofilms grown

on glass slides. P. gingivalis, on the other hand, readily

attached to S. gordonii. S. cristatus cell-free extract

substantially affected expression of fimA in P. gingivalis,

as determined by using a reporter system. S. cristatus is

able to modulate P. Gingivalis fimA expression and prevent

its attachment to the biofilm. Davies et al.40 showed that

two different cell-to-cell signalling systems in P. aeruginosa,lasR-lasI and rhlR-rhlI, were involved in biofilm formation.

At sufficient population densities, these signals reach

concentrations required for activation of genes involved

in biofilm differentiation. Mutants unable to produce both

signals (double mutant) were able to produce a biofilm, but

unlike the wild type, their biofilms were much thinner, cells

were more densely packed, and the typical biofilm

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architecture was lacking. In addition, these mutant biofilms

were much more easily removed from surfaces by a

surfactant treatment. Addition of homoserine lactone to

the medium containing the mutant biofilms resulted in

biofilms similar to the wild type with respect to structure

and thickness.

Stickler et al.41 also detected acylated homoserine lactone

signals homoserine lactone signals in biofilms of gram-

negative bacteria on urethral catheters. Yung-Hua et al.42

showed that induction of genetic competence (enabling

the uptake and incorporation of exogenous DNA by

transformation) is also mediated by quorum sensing in S.

mutans. Transformational frequencies were 10600 times

higher in biofilms than planktonic cells.

Predation and Competition

Bacteria within biofilms may be subject to predation by

free-living protozoa, Bdellovibrio spp., bacteriophage, andpolymorphonuclear leukocytes (PMNs) as a result of

localized cell concentration. Murga et al.43 demonstrated

the colonization and subsequent predation of heterotrophic

biofilms by Hartmannella vermifor mis, a free- living

protozoon. Predation has also been demonstrated with

Acanthamoeba spp. in contact lens storage case biofilms44.

James et al.31 noted that competition also occurs within

biofilm s an d dem on st rated that in vasi on of a

Hyphomicrobium sp. biofilm by P. putida resulted in

dominance by the P. putida, even though the biofilm-

associated Hyphomicrobium numbers remained relatively

constant. Stewart et al.45

investigated biofilms containingK. pneumoniae and P. aeruginosa and found that both

species are able to coexist in a stable community even

though P. aeruginosa growth rates are much slower in the

mixed culture biofilm than when grown as a pure culture

biofilm. P. aeruginosa grow primarily as a base biofilm,

whereas K. pneumoniae form localized microcolonies

(covering only about 10% of the area) that may have greater

access to nutrients and oxygen. Apparently P. aeruginosa

can compete because it colonizes the surface rapidly and

establishes a long-term competitive advantage. K.

pneumoniae apparently survives because of its ability to

attach to the P. Aeruginosa biofilm, grow more rapidly, and

out-compete the P. Aeruginosa in the surface layers of thebiofilm.

Dispersal

Biofilm cells may be dispersed either by shedding of

daughter cells from actively growing cells, detachment as a

result of nutrient levels or quorum sensing, or shearing of

biofilm aggregates (continuous removal of small portions

of the biofilm) because of flow effects. The mechanisms

underlying the process of shedding by actively growing

cells in a biofilm are not well understood. Gilbert et al. 53

showed that surface hydrophobicity characteristics of

newly divided daughter cells spontaneously dispersed from

either E. coli or P. aeruginosa biofilms differ substantially

from those of either chemostat-intact biofilms orresuspended biofilm cells. These researchers suggested

that these differences might explain newly divided daughter

cells detachment. Hydrophobicity was lowest for the newly

dispersed cells and steadily increases upon continued

incubation and growth. Alginate is the major component of

the EPS of P. aeruginosa. Inducing alginate lyase expression

substantially decreased the amount of alginate produced,

which corresponded with a significant increase in the

number of detached cells. The authors54 suggested that

the role of algL (the gene cassette for alginate lyase

production) in wild type P. aeruginosa may be to cause a

release of cells from solid surfaces or biofilms, aiding in the

dispersal of these organisms. Polysaccharidase enzymesspecific for the EPS of different organisms may possibly be

produced during different phases of biofilm growth of these

organisms. Detachment caused by physical forces has been

studied in greater detail. Brading et al.55 have emphasized

the importance of physical forces in detachment, stating

that the three main processes for detachment are erosion

or shearing (continuous removal of small portions of the

biofilm), sloughing (rapid and massive removal), and

abrasion (detachment due to collision of particles from the

bulk fluid with the biofilm). Characklis 56 noted that the rate

of erosion from the biofilm increases with increase in biofilm

thickness and fluid shear at the biofilm-bulk liquid interface.

Sloughing is more random than erosion and is thought to

result from nutrient or oxygen depletion within the biofilm

structure 55. Sloughing is more commonly observed with

thicker biofilms that have developed in nutrient-rich

environments 56.

Possible Strategies to Control Oral Biofilm.

Disruption of biofilm matrix

The mechanical disruption of the biofilm matrix has been

one of the oldest and most successful means to control

oral biofilms, the main advantage of the technique is it is

simple to perform, gives consistent results, helps to reduce

the bacterial load, no development of resistance so may be

performed regular ly as home care procedure or as

professional oral prophylaxis.

Control of nutrients

Addition of base-generating nutrients (arginine)

Reduction of GCF flow through anti-inflammatory agents

Inhibition of key microbial enzymes

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Nirjhar Bhowmiket al

Control of biofilm pH

Sugar substitutes

Antimicrobial agents

Fluoride

Stimulate base production

Control of redox potential

Redox agents

Oxygenating agents

Conclusion

The key to a more complete understanding of the role of

microorganisms in dental diseases such as periodontal

diseases and caries may depend on a paradigm shift away

from concepts that have evolved from studies of classical

medical infections with a simple and specific (e.g. single

species) aetiology to an appreciation of ecologicalprinciples. The development of plaque-mediated disease

at a site may be viewed as a breakdown of the homeostatic

mechanisms that normally maintain a beneficial relationship

between the resident oral microflora and the host. When

assessing treatment options, an appreciation of the ecology

of the oral cavity will enable the enlightened clinician to

take a more holistic approach and consider the nutrition,

physiology, host defences, and general well-being of the

patient, as these will affect the balance and activity of the

resident oral microflora. Future episodes of disease will

occur unless the cause of any breakdown in homeostasis

is recognized and remedied.

Table 1: Basic Biofilm Properties.

Cooperating community of various types of

microorganisms

Microorganisms are arranged in microcolonies

Microcolonies are surrounded by protective matrix

Within the microcolonies are differing environments

Microorganisms have primitive communication system

Microorganisms in biofilm are resistant to antibiotics,

antimicrobials, and host response.

REFERENCES1. Costerton JW, Stewart PS, Greenberg EP. Bacterial biofilms: a common cause of

persi stent infect ions.Science. 1999; 284: 1318-1322.

2. van Houte J. Role of micro-organisms in caries etiology. J Dent Res. 1994;73:

672-681.

3. Stenudd C, Nordlund A, Ryberg M, et al.. The association of bacterial adhesion

with dental caries.. J Dent Res. 2001; 80: 2005-2010.

4. Socransky SS, Haffajee AD, Cugini MA, et al.. Microbial complexes in

subgingival plaque. J Clin Periodontol. 1998;25: 134-144.

5. Haffajee AD, Socransky SS. Microbial etiological agents of destructive

periodontal diseases. Perio dontol 2000. 1995;5: 78-11.

6. Loesche WJ. Chemotherapy of dental plaque infections.. Oral Sci Rev. 1976;9:

65-107.

7. Theilade E. The non-specific theory in microbial etiology of inflammatory

periodont al disease . J Clin Periodon tol. 1986;13: 905-911.

8. Thomas JG, Nakaishi LA. Managing the complexity of a dynamic biofilm. J Am

Dent Assoc.. 2006;137(11 suppl): 10S-13S.

9. Loesche WJ. DNA probe and enzyme analysis in periodontal diagnostics. J

Periodontol. 1992;63: 1102-1109.

10. Socransky SS, Haffajee AD. Periodontal microbial etiology. Periodontol 2000.

2005;38: 135-187.

11. Socransky SS, Haffajee AD. Dental biofilms: difficult therapeutic targets.

Periodontol 2000. 2002;28: 12-34.

12. Brown MR, Gilbert P. Sensitivity of biofilms to antimicrobial agents. J Appl

Bacteriol. 1993;74(suppl): 87S-97S.

13. Gilbert P, Das J, Foley I. Biofilm susceptibility to antimicrobials. Adv Dent

Res. 1997;11: 160-167.

14. Costerton JW, Lewandowski Z, DeBeer D, et al.. Biofilms, the customized

microniche. J Bacteriol. 1994;176: 2137-2142.

15. Wood SR, Kirkham J, Marsh PD, et al.. Architecture of intact natural human

plaque biofi lms studied by confocal laser scanning microscopy.. J Dent Res.

2000;79: 21-27.

16. Levine MJ, Reddy MS, Tabak LA, et al.. Structural aspects of salivary

glycoproteins. J Dent Res. 1987;66: 436-441.

17. Tabak LA, Levine MJ, Mandel ID, Ellison SA. Role of salivary mucins in the

protection of the oral cavity. J Oral Pathol. 1982;11:1-17.

18. Gibbons RJ, Hay DI. Human salivary acidic proline-rich proteins and statherin

promote the attachment of Actinomyces viscosus LY7 to apatitic surfaces. Infect

Immun. 1988;56: 439-445.

19. Costerton JW, Cheng KJ, Geesey GG, et al.. Bacterial biofilms in nature and

disease. Annu Rev Microbiol.. 1987;41: 435-464.

20. Gibbons RJ. Microbial ecology: adherent interactions which may affect

microbial ecology in the mouth. J Dent Res. 1984;63:378-385.

21.Whittaker CJ, Klier CM, Kolenbrander PE. Mechanisms of adhesion by oral

bacteria. Annu Rev Microbio l. 1996;50: 513-552.

22. Wirthlin MR, Armitage GC. Dental plaque and calculus: microbial biofilms

and periodontal diseases. . In: Rose LF, Mealey BL,Genco RJ, Cohen W. , editors.

Periodontics: Medicine, Surgery and Implants. St. Louis, MO: Elsevier Mosby;

2004.

23. Flemming H-C, Wingender J, Griegbe, Mayer C. Physico-chemical properties

of biofilms. In: Evans LV, editor. Biofilms: recent advances in their study and

control. Amsterdam: Harwood Academic Publishers; 2000. p. 1934.

24. Sutherland IW. Biofilm exopolysaccharides: a strong and sticky framework.

Microbiology 2001;147:39.

25. Hussain M, Wilcox MH, White PJ. The slime of coagulase-negative

staphylococci: biochemistry and relation to adherence. FEMS Microbiol Rev

1993;104:191208.

26. Leriche V, Sibille P, Carpentier B. Use of an enzyme-linked lectinsorbent assay

to monitor the shift in polysaccharide composition in bacterial biofilms. Appl

Environ Microbiol 2000;66:18516.

27. Donlan RM. Role of biofilms in antimicrobial resistance. ASAIO J

2000;46;S47S52.

28. Tolker-Nielsen T, Molin S. Spatial organization of microbial biofilm

communities. Microb Ecol 2000;40:7584.

29. Lewandowski Z. Structure and function of biofilms. In: Evans LV, editor.

Biofilms: recent advances in their study and control. Amsterdam: Harwood

Academic Publishers; 2000. p. 117.

30. Stoodley P, Boyle JD, Dodds I, Lappin-Scott HM. Consensus model of biofilm

structure. In: Wimpenny JWT, Gilbert PS, Lappin-Scott HM, Jones M, editors.

Biofilms: community interactions and control. Cardiff, UK: Bioline; 1997. p. 1

9.

31. James GA, Beaudette L, Costerton JW. Interspecies bacterial interactions in

biofilms. Journal of Industrial Microbiology 1995;15: 25762. 47. Tolker-Nielsen

T, Brinch UC, Ragas PC, Andersen JB, Jacobsen CS, Molin S. Development and

dynamics of Pseudomonas sp. biofilms. J Bacteriol 2000;182:64829.

32. Durack DT. Experimental bacterial endocarditis. IV Structure and evolution of

very early lesions. J Pathol 1975;115:819.

7/28/2019 e-JOD7BD5F6F930-02FB-4209-8A09-D82522

7/7

www.ejournalofdentistry.comDental Plaque..........unveiling the biofilm inside

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33. Tunney MM, Jones DS, Gorman SP. Biofilm and biofilm-related encrustations

of urinary tract devices. In: Doyle RJ, editor. Methods in enzymology, vol. 310.

Biofilms. San Diego: Academic Press; 1999. p. 55866.

34. Donlan RM. Biofilm control in industrial water systems: approaching an old

problem in new ways. I n: Evans LV, editor. Biofilms: recent advances in their

study and control. Amsterdam: Harwood Academic Publishers; 2000. p. 33360.

35. Ehlers LJ, Bouwer EJ. RP4 plasmid transfer among species of Pseudomonas in

a biofilm reactor. Water Sci Technol 1999;7:163171.

36. Roberts AP, Pratten J, Wilson M, Mullany P. Transfer of a conjugativetransposon, Tn5397 in a model oral biofilm. FEMS Microbiol Lett 1999;177:636.

37. Hausner M, Wuertz S. High rates of conjugation in bacterial biofilms as

determined by quantitative in situ analysis. Appl Environ Microbiol

1999;65:371013.

38. Ghigo J-M. Natural conjugative plasmids induce bacterial biofilm

development. Nature 2001;412:4425.

39. Xie H, Cook GS, Costerton JW, Bruce G, Rose TM, Lamont RJ. Intergeneric

communication in dental plaque biofilms. J Bacteriol 2000;182:70679.

40. Davies DG, Parsek MR, Pearson JP, Iglewski BH, Costerton JW, Greenberg

EP. The involvement of cell-to-cell signals in the development of a bacterial biofilm.

Science 1998;280:2958.

41. Stickler DJ, Morris NS, McLean RJC, Fuqua C. Biofilms on indwelling urethral

catheters produce quorum-sensing signal molecules in situ and in vitro. Appl

Environ Microbiol 1998;64:348690.

42. Yung-Hua L, Lau PCY, Lee JH, Ellen RP, Cvitkovitch DG. Natural genetic

transformation of Streptococcus mutans growing in biofilms. J Bacteriol2001;183:897908.

43. Murga R, Forster TS, Brown E, Pruckler JM, Fields BS, Donlan RM. The role

of biofilms in the survival of Legionella pneumophila in a model potable water

system. Microbiology 2001;147:31216.

44. McLaughlin-Borlace L, Stapleton F, Matheson M, Dart JKG. Bacterial biofilm

on contact lenses and lens storage cases in wearers with microbial keratitis. J

Appl Microbiol 1998;84:82738.

45. Stewart PS, Camper AK, Handran SD, Huang C-T, Warnecke M. Spatial

distribution and coexistence of Klebsiella pneumoniae and Pseudomonas

aeruginosa in biofilms. Microb Ecol 1997;33:210.

46. Raad II, Sabbagh MF, Rand KH, Sherertz RJ. Quantitative tip culture methods

and the diagnosis of central venous catheter-related infections. Diagn Microbiol

Infect Dis 1992;15:1320.

47. Wirtanen G, Alanko T, Mattila-Sandholm T. Evaluation of epifluorescence

image analysis of biofilm growth on stainless s teel surfaces. Col loids and Surfaces

B: Biointerfaces 1996;5:31926.

48. Buswell CM, Herlihy YM, Lawrence LM, McGuiggan JTM, Marsh PD, Keevi l

CW, et al. Extended survival and persistence of Campylobacter spp. in water and

aquatic biofilms and their detection by immunofluorescent-antibody and -rRNA

staining. Appl Environ Microbiol 1998;64:73341.

49. Camper AK, Warnecke M, Jones WL, McFeters GA. Pathogens in model

distribution system biofilms. Denver: American Water Works Association

Research Foundation; 1998.

50. Hood SK, Zottola EA. Adherence to stainless steel by foodborne

microorganisms during growth in model food systems. Int J Food Microbiol

1997;37:14553.

51. Watnick PI, Kolter R. Steps in the development of a Vibrio cholerae El Tor

biofilm. Mol Microbiol 1999;34:58695.

52. Stark RM, Gerwig GJ, Pitman RS, Potts LF, Williams NA, Greenman J, et al.

Biofilm formation by Helicobacter pylori. Lett Appl Microbiol 1999;28:1216.

69. Gilbert P, Evans DJ, Brown MRW. Formation and dispersal of bacterial biofilms

in vivo and in situ. J Appl Bacteriol Symposium Supplement 1993;74:67S78S.

53. Boyd A, Chakrabarty AM. Role of alginate lyase in cell detachment ofPseudomonas aeruginosa. Appl Environ Microbiol 1994;60:23559.

54. Brading MG, Jass J, Lappin-Scott HM. Dynamics of bacterial biofilm formation.

In: Lappin-Scott HM, Costerton JW, editors. Microbial biofilms. Cambridge:

Cambridge University Press; 1995. p. 4663.

55. Characklis WG. Biofilm processes. In: Characklis WG, Marshall KC, editors.

Biofilms. New York: John Wiley & Sons; 1990. p. 195231.

56. Korber DR, Lawrence JR, Lappin-Scott HM, Costerton JW. Growth of

microorganisms on surfaces. In: Lappin-Scott HM, Costerton JW, editors.

Microbial biofilms. Cambridge: Cambridge University Press; 1995. p.1545.

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