The role of dental plaque biofilm in oral health

Access, Sept-Oct, 2007 by JoAnn R. Gurenlian

Abstract

Overview. Microbial biofilms are complex communities of bacteria and are common in the human body and in the environment. In recent years, dental plaque has been identified as a biofilm, and the structure, microbiology, and pathophysiology of dental biofilms have been described. The nature of the biofilm enhances the component bacteria's resistance to both the host's defense system and antimicrobials. If not removed regularly, the biofilm undergoes maturation, and the resulting pathogenic bacterial complex can lead to dental caries, gingivitis, and periodontitis. In addition, dental biofilm, especially subgingival plaque in patients with periodontitis, has been associated with various systemic diseases and disorders, including cardiovascular disease, diabetes mellitus, respiratory disease, and adverse pregnancy outcomes.

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Clinical Implications. An understanding of the nature and pathophysiology of the dental biofilm is important to implementing proper management strategies. Although dental biofilm cannot be eliminated, it can be reduced and controlled through daily oral care. A daily regimen of thorough mechanical oral hygiene procedures, including toothbrushing and interdental cleaning, is key to controlling biofilm accumulation. Because teeth comprise only 20% of the mouth's surfaces, for optimal oral health, the use of an antimicrobial mouthrinse helps to control biofilm not reached by brushing and flossing as well as biofilm bacteria contained in oral mucosal reservoirs.

Key words: Antimicrobial mouthrinse, biofilm, dental plaque, oral health, periodontal disease

Introduction

In contrast to an accumulation of individual bacteria, a biofilm is a complex, communal, 3-dimensional arrangement of bacteria. Bacterial biofilms are ubiquitous and are potentially found in a variety of sites within the human body. For example, they can grow on indwelling catheters, ports, and implants; external surfaces of the eye; artificial heart valves; endotracheal tubes; and contaminated prosthetic joints. A bacterial biofilm is often the cause of persistent infections and has been associated with osteomyelitis, pneumonia in patients with cystic fibrosis, and prostatitis. (1)

In areas related to oral health care, bacterial biofilms are found in dental unit water lines, on tooth surfaces and dental prosthetic appliances, and on oral mucous membranes. Biofilm in the form of supragingival and subgingival plaque is the etiologic agent in dental caries and periodontal diseases (Figure 1). (2-5) The pathogenicity of the dental plaque biofilm is enhanced by the fact that in biofilm form, the component bacteria have increased resistance to antibiotics and other chemotherapeutic agents and are less able to be phagocytized by host inflammatory cells. Therefore, control of the dental plaque biofilm is a major objective of dental professionals and critical to the maintenance of optimal oral health. This article reviews the characteristics of dental biofilm, its role in the etiology of periodontal diseases, and strategies for controlling the biofilm to promote health.

Changing Views of Dental Plaque

Over the past 50 years, the understanding and characterization of dental plaque have undergone significant evolution. Loesche (6) proposed both a nonspecific and a specific plaque hypothesis for periodontal disease initiation and progression.

The nonspecific plaque hypothesis 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 defense 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 progression. (7,8)

Studies on the microbial etiology 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 periodontally diseased sites. These specific virulent bacterial species activate the host's immune and inflammatory responses that then cause bone and soft tissue destruction. (6,8,9)

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]

Socransky and colleagues (4,10) 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 severities (Figure 2). (4,10) Color designations were used to denote the association of particular bacterial complexes with peri odontal 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 disease. (10,11) For example, the bacteria in the red complex are more likely to be associated with clinical indicators of periodontal disease such as periodontal pocketing and clinical attachment loss.

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The role of dental plaque biofilm in oral health

Access, Sept-Oct, 2007 by JoAnn R. Gurenlian

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