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International Dental Journal (2010) 60, 200-203

Microbial biolms are common in the human body and in the environment. In recent

years, dental plaque has been identied as a biolm, and the structure, microbiology,

and pathophysiology of dental biolms have been characterised. The nature of the biolm

enhances the component bacterias resistance to both the hosts defence system and an-

timicrobials. If not removed regularly the biolm undergoes maturation, resulting in dentalcaries, gingivitis, and periodontitis. The control of biolm accumulation on teeth has been

the cornerstone of periodontal disease prevention for decades. However, the widespread

prevalence of gingivitis suggests the inefciency of self-performed mechanical plaque

control in preventing gingival inammation. Studies indicate that effective antiseptic mouth-

washes can provide signicant gingivitis reduction beyond what can be accomplished with

only brushing and ossing. Particularly, mouthrinses containing essential oils have well

documented clinical antiplaque and antigingivitis effects. These mouthrinses have a posi-

tive track record of safety and their use does not increase the levels of resistant species.

In summary, use of a well-established, essential oil mouthrinse can be recommended for

daily use as an adjunct to mechanical methods of plaque control.

2010 FDI/World Dental Press

0020-6539/10/03200-04 (Supplement 1)

Biolm dynamics at the gingival

frontier

Key words: Plaque, biolm periodontal disease

Sebastian Ciancio

doi:10.1922/IDJ_2557Ciancio

Biolms are complex arrangements of bacteria whichare ubiquitous and are potentially found in a varietyof sites within the human body. In areas relatedto oral health care, bacterial biolms are found ontooth surfaces, dental prosthetic appliances and oralmucous membranes, and are referred to as dentalplaques. Biolm in the form of supragingival andsubgingival plaque is the aetiologic agent in dental car-ies and periodontal diseases1-4. The pathogenicity of

the dental plaque biolm is enhanced by the fact thatthe component bacteria have increased resistance toantimicrobials and are less able to be phagocytised byhost inammatory cells. Therefore, control of dentalplaque biolm is a major objective of dental profes-sionals and critical to the maintenance of optimal oralhealth. This article reviews the dental biolm, its rolein the aetiology of periodontal diseases, and providesan overview of strategies for controlling the biolmto promote oral health.

Besides being a prerequisite for caries occur-rence5.6, dental biolm is the direct cause of gingivi-

tis7

. In a classical study of experimental gingivitis, thewithdrawal of all measures of oral hygiene resultedin the accumulation of abundant biolm and the

Center of Dental Studies , State University of New York ( SUNY) , Buffalo, USA

development of marginal gingivitis8. As some patientsmay improve oral hygiene just before a dental appoint-ment, the assessment of the gingival condition seemsto be a reliable and valid measure relative to the qualityof biolm control9.

Overview of dental plaque development

The growth and development of biolms are charac-

terised by four stages: initial adherence, lag phase, rapidgrowth, and steady state. Biolm formation begins withthe adherence of bacteria to a tooth surface, followed bya lag phase in which changes in gene expression occur. Aperiod of rapid growth then occurs, and an exopolysac-charide matrix is produced. During the steady state, thebiolm reaches growth equilibrium. Surface detachmentand sloughing occur, and new bacteria are acquired.

The most prevalent oral biolm, i.e. dental plaque,exists as a complex multispecies entity, consisting ofmore than 700 bacterial species on the tooth surface. The bacteria in the biolm deposit on the teeth by

attaching to host-derived glycoproteins, mucins andother proteins coating the tooth surface10. These sali-vary proteins are deposited within minutes on a clean

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tooth surface and are called the acquired pellicle, whichmakes the surface receptive to colonisation by specicbacteria. Acquired pellicle formation begins within min-utes of a professional prophylaxis and within one hour,microorganisms attach to the pellicle.

Furthermore, microorganisms on the outer surfaceof biolms are not as strongly attached within the ma-trix and tend to grow faster than those bacteria deeper within the biolm. Surface microorganisms are moresusceptible to detachment, a characteristic that facilitatestravel and formation of new biolm colonies on nearbyoral structures and tissues.

Continued development of the plaque biolm relieson physical interaction of bacteria of the same or dif-ferent class through coaggregation and coadhesion11.Many of these bacteria would not usually interact witheach other in a way that results in aggregation. However,certain bacteria, such as Fusobacterium nucleatum, serve

as important bridges between these non-coaggregat-ing, early colonising bacteria and the late colonisers11,facilitating coaggregation.

Studies on the microbial aetiology of various formsof periodontitis demonstrate that only certain micro-organisms within the plaque complex are pathogenic. These specic virulent bacterial species activate thehosts immune and inammatory responses that thencause bone and soft tissue destruction12-14.

Biolms can harbour mucosal surfaces throughoutthe oral cavity. Microcolonies exist on oral mucosa,the tongue, and especially the dorsum of the tongue

(because of its long papilla (agiform papilla)), bioma-terials used for restorations and dental appliances, andtooth surfaces above and below the gingival margin.As the biolm begins to mature, there is a progressiveshift from a gram positive, aerobic ora to one pre-dominated by gram negative, anaerobic species. Thisshift is associated with the development of the biolmbeneath the gingival surface and is strongly inuencedby supragingival plaque biolm. However, salivary andmasticatory inuences that have an impact on the su-pragingival microora do not have the same inuenceon subgingival bacteria15. As the gingival inammatory

process continues, additional mediators are produced,and more inammatory cell types such as neutrophils,T cells, and monocytes are recruited to the area.

The result of this chronic inammation is a break-down of gingival collagen and accumulation of an inam-matory inltrate, leading to the clinical signs of gingivitis.In some individuals, the inammatory process will alsolead to the breakdown of collagen in the periodontalligament and resorption of the supporting alveolar bone,leading to periodontitis. Thus, controlling dental plaquebiolm is essential to preventing and reversing gingivitisas well as preventing and managing periodontitis.

Inorganic components are also found in dentalplaque; largely calcium and phosphorus which areprimarily derived from saliva. The inorganic content

of plaque is greatly increased with the development ofcalculus. The process of calculus formation involvesthe calcication of dental plaque. The practical con-sequences of calculus formation are that the depositis signicantly more difcult to remove once calcied,and it leaves a rough surface on the root which is easilycolonised by plaque.

The extracellular matrix produced by biolm bac-teria encloses the microbial community and protects itfrom the surrounding environment, including attacksfrom chemotherapeutic agents16-19. Thus, the matrixhelps to protect bacteria deep within the biolm fromantibiotics and antiseptics, increasing the likelihood ofthe colonies survival. Furthermore, the extracellularmatrix keeps the bacteria banded together, so they arenot ushed away by the action of saliva and gingivalcrevicular uid. Mechanical methods, including tooth-brushing, interdental cleaning, and professional scaling

procedures, are required to regularly and effectivelydisrupt and remove the plaque biolm. Antiseptics,such as mouthrinses, can help to control the biolmbut must be formulated so as to be able to penetrate theplaque biolm matrix and gain access to the pathogenicbacteria.

It is important for oral health professionals to com-municate to their patients that both dental caries andperiodontal disease are infectious diseases resultingfrom dental plaque biolm accumulation. Each of thesediseases requires specic strategies for prevention andtreatment.

Penetrating the plaque biolm role of

essential oil containing mouthwash

Bacteria in plaque biolms are more resistant to antimi-crobial agents than they are in the free-oating (plank-tonic) form. The efcacy of any antiseptic mouthwashdepends on its ability to penetrate the biolm in additionto its ability to kill bacteria invivo20.

Essential oil (EO) mouthwashes kill microorgan-isms by disrupting their cell walls and inhibiting theirenzymic activity. They prevent bacterial aggregation,

slow multiplication and extract endotoxins. Studies alsosuggest that an effective mouthwash must also penetratethe plaque biolm.

The efcacy of oral antiseptics is usually attributedto their bactericidal activity, but essential oils also workby interfering with bacterial colonisation of the toothsurface. Essential oils stop bacteria from aggregatingwith gram positive pioneer species, slow bacterial mul-tiplication, and extract endotoxins from gram negativepathogens21. This can lead to a reduced bacterial load,slow plaque maturation and decreased plaque mass andpathogenicity.

The essential oils in an over-the-counter mouthwash,Listerine (Johnson & Johnson), have demonstrated theability to penetrate the plaque biolm and have also been

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shown in vitro to kill 99.9% of oral gram positive andgram negative bacteria, opportunistic bacteria and yeastwithin a 30 second exposure22-24. The active ingredientsof this essential oil mouthwash are a xed combina-tion of four essential oils; thymol 0.064%, eucalyptol0.092%, methyl salicylate 0.06%, and menthol 0.042%25-27. These essential oils slow plaque maturation anddecrease plaque mass and pathogenicity20,28. Listerine isthe only over-the-counter mouthwash to have receivedthe ADA (American Dental Association) Council onScientic Affairs Seal of Acceptance for control ofsupragingival plaque and gingivitis.

Rinsing with essential oils could also impact thesubgingival microbiota29. The subgingival antimicrobialeffect of the mouthrinse is most likely mediated bydisruption of the contiguous supragingival biolm29.A regimen of twice daily rinsing with essential oils for14 days can reduce the levels of total anaerobes, gram

negative anaerobes and volatile sulphur compound-pro-ducing organisms in plaque and on the dorsum of thetongue up to 12 hours after the nal rinse, indicating acertain level of substantivity24.

A study examining the adjunctive benet of essentialoils in reducing plaque and gingivitis in subjects whobrush and oss regularly, demonstrated that in additionto brushing, the essential oil mouthrinse group had sta-tistically and clinically signicantly lowered plaque levels,suggesting that essential oils are an effective adjunct toregular brushing and ossing30 or brushing alone31.

Conclusions

In summary, dental biolm is a complex, organised mi-crobial community that is the primary aetiologic factorfor the most frequently occurring oral diseases: dentalcaries and periodontal diseases. Dental plaque accumu-lates not only on teeth, dentures and orthodontic appli-ances but also on oral soft tissues. This accumulation isfacilitated by the absence of adequate oral hygiene pro-cedures. Dental plaque consists of a biolm containing amass of microorganisms embedded in an organic matrixof host and microbial origin. Consequences of plaque

include dental caries, gingivitis, periodontal disease anddenture associated problems. Thus the prevention ofplaque formation, the reduction of plaque accumulationand the effective removal of plaque play a signicantrole in maintaining optimal oral hygiene.

The goal of keeping dental biolm growth to lowlevels has been shown to be more achievable whenchemotherapeutic agents such as essential oils rinsesare used in conjunction with conventional mechanicalmeans of plaque reduction. Based on the evidence-basesupporting this, it is recommended that dental patientsbe educated on the benets of rinsing with an estab-

lished and clinically proven antimicrobial mouthrinse,after brushing and interdental cleaning, in order toachieve optimal oral hygiene levels.

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Correspondence to: Sebastian Ciancio, Distinguished Service

Professor and Chair, Department of Periodontics and Endodontics,

Adjunct Professor of Pharmacology Director , Center for Dental

Studies, 250 Squire Hall, University at Buffalo, SUNY, Buffalo, NY

14212, USA. Email: ciancio@buffalo.edu