DENTAL PLAQUE / BIOFILM IN PERIODONTOLOGY

Comprehensive Theory Examination Notes

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1. DEFINITION AND RECENT TERMINOLOGY CHANGE

Recent Terminology Update (EXAMINER CRITICAL)

"It is now very common to see the term 'dental biofilm' used instead of the original descriptor 'dental plaque'. This does not mean that the term 'dental plaque' is now invalid or irrelevant; rather it emphasizes the point that the broader principles derived from work on biofilms from across the spectrum of biofilm habitats apply equally to dental plaque biofilms, and vice versa."

• Dental plaque is defined clinically as a structured, resilient, yellow-grayish substance that adheres tenaciously to the intraoral hard surfaces, including removable and fixed restorations.
• Plaque is primarily composed of bacteria in a matrix of salivary glycoproteins and extracellular polysaccharides.
• This matrix makes it impossible to remove the plaque by rinsing or the use of sprays - a key distinguishing feature.

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2. COMPOSITION OF DENTAL PLAQUE

Microbial Composition

• Dental plaque is composed primarily of microorganisms.
• One gram of plaque (wet weight) contains approximately 10¹¹ bacteria.
• The number of bacteria in supragingival plaque on a single tooth surface can exceed 10⁹.
• In a periodontal pocket, counts range from 10³ bacteria in a healthy crevice to greater than 10⁸ bacteria in a deep pocket.
• More than 500 distinct microbial species are found in dental plaque.
• New molecular approaches (ribosomal DNA sequence analysis) suggest that as much as 30% of microorganisms associated with gingivitis may represent uncultivated species.
• One individual may harbor 150 or more different species.
• Only approximately 50% of the resident oral microbiota can currently be cultivated in pure culture in the laboratory.
• 16S rRNA gene studies have identified around 900 species in the mouth; most sites yielded 20-30 different predominant species, while the number of species per individual mouth can range from 34 to 72.

Non-Bacterial Inhabitants of Dental Plaque

• Mycoplasma species, yeasts, protozoa, and viruses have been found in dental plaque.
• The microorganisms exist within an intercellular matrix that also contains a few host cells, such as epithelial cells, macrophages, and leukocytes.

Organic Components of the Plaque Matrix

Inorganic Components

• Predominantly calcium and phosphorus, with trace amounts of other elements.
• The source of inorganic components of supragingival plaque is primarily saliva.
• As the mineral content increases, the plaque mass becomes calcified (calculus formation).
• The inorganic components of subgingival plaque are derived from crevicular fluid (a serum transudate).
• Fluoride component of plaque is largely derived from external sources such as fluoridated toothpastes and fluoride rinses; fluoride inhibits the growth of many plaque microorganisms.

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3. CLASSIFICATION OF DENTAL PLAQUE

Primary Classification: Location-Based

Subgingival Plaque: Two Distinct Zones

Layers of Subgingival Biofilm (FISH Studies - Zijnge et al. 2010)

1. Basal layer - Rod-shaped bacteria (Actinomyces spp.) attached perpendicularly to the tooth surface
2. Intermediate layer - Spindle-shaped cells, including F. nucleatum and Tannerella forsythia
3. Top layer - Many putative periodontal pathogens, such as P. gingivalis, Porphyromonas endodontalis, P. intermedia, and Parvimonas micra
4. Fourth layer - Unattached cells mainly consisting of spirochetes; Synergistetes spp. formed a palisade-like layer along the outer edge, in direct contact with host immune cells.

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4. DENTAL PLAQUE AS A BIOFILM

Definition of Biofilm

• Biofilms are heterogeneous - variations in structure exist within individual biofilms, between different types of biofilms, and between individuals.
• Biofilms frequently contain microcolonies of bacterial cells.
• Water channels are commonly found in biofilms and can form a primitive circulatory system that removes waste products and brings fresh nutrients to the deeper layers.
• Surface structures (fronds) can dissipate the energy of fluid flowing over the biofilm.
• Mixed-species biofilms often have heterogeneity in the distribution of different species.
• Steep chemical gradients (oxygen, pH) produce distinct microenvironments within the biofilm.

The Dental Plaque Biofilm - Specific Features

• The dental plaque biofilm has a heterogeneous structure, with clear evidence of open fluid-filled channels running through the plaque mass.
• These water channels permit the passage of nutrients and other agents throughout the biofilm, acting as a primitive circulatory system.
• The biofilm exists as a specialized environment, which distinguishes bacteria that exist within the biofilm from those that are free-floating (the so-called planktonic state in solutions such as saliva or crevicular fluid).
• The biofilm matrix functions as a barrier: substances produced by bacteria within the biofilm are retained and concentrated within the matrix.
• After 1 day, the term biofilm is fully deserved because organization takes place within the plaque.

Biofilm-Associated Infections - Criteria (Costerton 2003)

• Association with a surface
• Direct demonstration of biofilm in tissue
• Fastidious organisms or unusual antibiotic resistance patterns
• Failure to respond to antibiotics despite susceptibility in planktonic tests
• Recurrence after antibiotic therapy

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5. FORMATION OF DENTAL PLAQUE/BIOFILM

Three Major Phases (Carranza 10th Ed.)

1. Formation of the pellicle on the tooth surface
2. Initial adhesion and attachment of bacteria
3. Colonization and plaque maturation

Six Distinct Stages (Lindhe/Lang 6th Ed. - Marsh)

1. Adsorption of a conditioning film (acquired pellicle)
2. Reversible adhesion between the microbial cell surface and the conditioning film
3. More permanent (irreversible) attachment involving interactions between specific molecules on the microbial cell surface (adhesins) and complementary molecules (receptors) present in the conditioning film
4. Co-adhesion - secondary colonizers adhere to receptors on already attached bacteria
5. Multiplication of attached cells; increase in biomass and synthesis of exopolymers to form the biofilm matrix (plaque maturation)
6. Detachment of attached cells to promote colonization elsewhere

FLOWCHART: Dental Plaque/Biofilm Formation

CLEAN TOOTH SURFACE
        |
        v
[PHASE 1: PELLICLE FORMATION]
Within nanoseconds after polishing:
Saliva-derived layer (acquired pellicle) adsorbs onto tooth surface
Components: glycoproteins (mucins), proline-rich proteins,
phosphoproteins (statherin), histidine-rich proteins,
enzymes (alpha-amylase), acting as adhesion receptors
Mechanisms: electrostatic, van der Waals, hydrophobic forces
        |
        v
[PHASE 2: INITIAL ADHESION OF BACTERIA]
4-Stage Sequence (Busscher et al.):
  Stage 1: Transport to surface (Brownian motion,
           sedimentation, liquid flow, chemotaxis)
  Stage 2: Initial REVERSIBLE adhesion (long-range and
           short-range forces: van der Waals attractive
           + electrostatic repulsive forces from ~50 nm)
  Stage 3: Permanent attachment (specific adhesin-receptor
           interactions; stereochemical molecular binding)
  Stage 4: Colonization of surface and biofilm formation
        |
        v
[PHASE 3: PRIMARY COLONIZERS ESTABLISH]
Predominantly gram-positive facultative anaerobes:
- Streptococcus species (S. sanguis, S. mitis, S. oralis)
- Actinomyces species (A. naeslundii, A. viscosus)
These are members of the YELLOW and PURPLE complexes
Doubling times < 1 hour during first 4 hours
Primary colonizers remove oxygen, providing low-oxygen tension
for survival of secondary colonizers
        |
        v
[PHASE 4: CO-ADHESION AND SECONDARY COLONIZATION]
Secondary colonizers do NOT initially colonize clean surfaces -
they adhere to already-attached primary colonizers
Secondary colonizers: Fusobacterium nucleatum, Prevotella
intermedia, Capnocytophaga spp., Porphyromonas gingivalis
Key interactions:
- F. nucleatum + Streptococcus sanguis
- Prevotella loescheii + Actinomyces viscosus
- Capnocytophaga ochracea + A. viscosus
- F. nucleatum + P. gingivalis (in later stages)
- F. nucleatum + Treponema denticola
        |
        v
[PHASE 5: PLAQUE MATURATION]
- Synthesis of exopolymers forms BIOFILM MATRIX
- Matrix: more than a scaffold; binds and retains water/nutrients
- Microbial generation time increases: 1 hr (early plaque)
  to 12 hrs (3-day-old plaque) = explains leveling off after Day 4
- Ecologic shift: aerobic gram-positive environment
  -> oxygen-deprived gram-negative anaerobic predominance
- "Corncob" and "test-tube brush" formations appear
- Cell-cell signaling (Quorum Sensing) system activates
        |
        v
[MATURE PLAQUE/BIOFILM - with Open Fluid-filled Channels]
Bacteria communicate via quorum sensing;
Matrix acts as barrier; horizontal gene transfer occurs;
Antimicrobial resistance develops; Dysbiosis potential activated
        |
        (if undisturbed)
        v
[SUBGINGIVAL PLAQUE EXTENSION]
Biofilm exploits the ecologic niche of the deepening sulcus
Apical proliferation; further rendering effective plaque control difficult
->  Chronic inflammation -> Periodontitis

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6. PELLICLE (ACQUIRED ENAMEL PELLICLE)

• All surfaces of the oral cavity (both hard and soft tissues) are coated with a pellicle (initial phase of plaque development).
• Within nanoseconds after vigorously polishing the teeth, a thin, saliva-derived layer, called the acquired pellicle, covers the tooth surface.
• Studies of early (2-hour) enamel pellicle reveal that its amino acid composition differs from that of saliva, indicating that the pellicle forms by selective adsorption of the environmental macromolecules.
• Note: The term "acquired pellicle" is currently less frequently used because it is misleading - it may imply that bacteria can colonize the tooth surface only when this pellicle is in place for some hours. However, it has been proved that bacteria can be part of the very early deposit, within seconds after prophylaxis.
• The physical and chemical nature of the solid substratum significantly affects several physicochemical surface properties of the pellicle, including its composition, packing, density, and configuration - thus characteristics of the underlying hard surface are transferred through the pellicle layers and can still influence initial bacterial adhesion.
• In the context of biofilm formation: "Bacteria rarely colonize clean enamel" - within seconds of eruption, or following cleaning, tooth surfaces become coated with a conditioning film.

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7. GROWTH DYNAMICS OF DENTAL PLAQUE

De Novo Supragingival Plaque Formation: Clinical Aspects

• Clinically, early undisturbed plaque formation follows an exponential growth curve.
• First 24 hours: Plaque growth is negligible from a clinical viewpoint (<3% coverage of the vestibular tooth surface - clinically almost undetectable).
• Following 3 days: Plaque growth increases at a rapid rate, then slows down.
• After 4 days: On average, 30% of the total tooth crown area will be covered with plaque.
• After the fourth day, plaque does not seem to increase substantially, but its composition continues to change - shift toward more anaerobic and gram-negative flora, including fusobacteria, filaments, spiral forms, and spirochetes.
• This ecologic shift represents a transition from the early aerobic environment (gram-positive facultative species) to a highly oxygen-deprived environment (gram-negative anaerobic microorganisms predominate).
• Microbial generation time: 1 hour for initial plaque to 12 hours for 3-day-old plaque - explains the leveling of the slope from day 4 onward.
• During the night: Plaque growth rate is reduced by about 50%. This is because supragingival plaque obtains its nutrients mainly from the saliva, and the decreased salivary flow at night reduces nutrient supply, which is of greater significance than antibacterial activity of saliva.

Topography of Supragingival Plaque Formation

• Early plaque formation on teeth follows a typical topographic pattern, with initial growth along the gingival margin and from the interdental space (areas protected against shear forces).
• Later, further extension in the coronal direction can be observed.
• Within a dental arch, early plaque formation occurs faster:
  1. In the lower jaw compared to the upper jaw
  2. In molar areas
  3. On the buccal tooth surfaces compared to oral sites (especially in the upper jaw)
  4. In the interdental regions compared to strict buccal or oral surfaces

Effect of Surface Characteristics on Plaque Formation

• A rough surface (Ra 2.0 µm) contains a thicker plaque layer than a smooth surface (Ra 0.1 µm).
• Surface roughness predominates over surface free energy in determining plaque accumulation on rough regions.
• Low surface free energy (Teflon) and high surface free energy surfaces show similar plaque accumulation on rough regions, demonstrating the predominance of surface roughness over surface energy.

Spontaneous Tooth Cleaning

• Many clinicians believe that plaque is removed spontaneously during eating. This is incorrect - based on firm bacterial attachment, spontaneous removal is unlikely. Even in the occlusal part of molars, plaque remains even after chewing fibrous food (e.g., carrots, apples, chips). Only negligible differences in plaque extension could be observed before and after dinner.

De Novo Subgingival Plaque Formation

• It is technically impossible to record the dynamics of subgingival plaque formation in an established dentition because one cannot sterilize a periodontal pocket.
• Studies using culturing techniques found only partial reduction of about 3 logs (from 10⁸ to 10⁵) after mechanical debridement, followed by fast regrowth to almost pretreatment levels (-0.5 log) within 7 days.
• The regrowth of subgingival plaque is a slow process compared with that of supragingival plaque.
• During this period (perhaps months), the subgingival plaque may not induce inflammatory reactions, because subgingival plaque that reforms is initially primarily gram-positive.
• Inadequate subgingival plaque control can lead to continued loss of attachment, even without visible gingivitis.

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8. STRUCTURE OF MATURE DENTAL BIOFILM

Key Structural Features

Microscopic Studies and Methods

• Electron microscopy (EM): Gave important insights into structure of dental plaque; showed biofilms containing a range of morphologic types, often as a compacted structure.
• Confocal laser scanning microscopy (CLSM): Does not require harsh sample processing (no dehydration); allows samples to be seen in natural, hydrated state; biofilms are optically sectioned and reconstructed as 3D structures. Confirmed open architecture of dental plaque.
• Fluorescence in situ hybridization (FISH): Allows specific visualization and identification of individual bacteria within mixed populations using nucleic acid probes; can image bacteria that have never been cultured in the laboratory (e.g., members of phylum Synergistetes).
• Live/Dead stains: Indicated bacterial vitality varies throughout the biofilm.

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9. COAGGREGATION AND INTERBACTERIAL INTERACTIONS

• Coaggregation refers to the cell-to-cell recognition and adhesion between genetically distinct bacterial types.
• Many coaggregations among strains of different genera are mediated by lectin-like adhesins (proteins that recognize carbohydrates) and can be inhibited by lactose and other galactosides, or by amino acids such as L-arginine.
• Streptococci show intrageneric coaggregation, allowing them to bind to the nascent monolayer of already-bound streptococci.

Well-Characterized Coaggregation Interactions:

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10. MICROBIAL COMPLEXES IN SUBGINGIVAL PLAQUE (SOCRANSKY ET AL.)

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11. COMMUNICATION BETWEEN BIOFILM BACTERIA

Quorum Sensing

• Plaque bacteria have been described to communicate by quorum sensing - similar systems have been described for other biofilms.
• Quorum sensing systems also regulate genetic competence in S. mutans so that the transformation frequency of biofilm-grown S. mutans is increased.
• This quorum sensing system also functions to regulate acid tolerance in S. mutans biofilms.
• Lysed cells in biofilms could act as donors of DNA, thereby increasing the opportunity for horizontal gene transfer in dental plaque.

Extracellular DNA (eDNA)

• eDNA is a ubiquitous constituent of all biofilms and of particular interest in biofilms associated with chronic diseases, such as periodontitis.
• The majority of eDNA is released after bacterial cell death.
• eDNA may be taken up by competent bacteria in plaque biofilm, increasing genetic diversity and facilitating the spread of antibiotic resistance.
• eDNA plays important roles in: biofilm formation; maintenance of structural integrity of the biofilm slime layer on hard surfaces; protection against antimicrobial agents.
• eDNA may ultimately prove to be an important target for biofilm disruption.

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12. BIOFILMS AND ANTIMICROBIAL RESISTANCE

Mechanisms of Reduced Susceptibility of Biofilms to Antimicrobials

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13. PLAQUE HYPOTHESIS - HISTORICAL EVOLUTION

FLOWCHART: Evolution of Plaque Hypotheses

[1] NONSPECIFIC PLAQUE HYPOTHESIS
(Early concept; unchallenged for decades)
  - Periodontal disease caused by overall accumulation of plaque
  - No distinction between species; quantity of plaque is key
  - All bacteria in plaque equally responsible for disease
  - Implication: complete plaque removal = disease prevention
            |
            | [CHALLENGED BY]
            | - Association of specific bacterial species with disease
            | - Microscopic examination showing different morphotypes
            |   in healthy vs. diseased sites
            v
[2] SPECIFIC PLAQUE HYPOTHESIS
(1960s onwards)
  - Specific bacteria responsible for specific diseases
  - Acceptance spurred by recognition of A. actinomycetemcomitans
    as pathogen in Localized Aggressive Periodontitis
  - Focus on identifying specific "periodontal pathogens"
  - Led to series of association studies in cross-sectional
    and longitudinal studies
  - Key pathogens: A. actinomycetemcomitans, P. gingivalis,
    T. forsythia, T. denticola
            |
            | [CHALLENGED BY]
            | - Presence of putative pathogens in healthy sites
            | - Holistic microbial changes rather than single species
            | - Community nature of pathogenesis
            v
[3] ECOLOGICAL PLAQUE HYPOTHESIS
(Marsh, 2003)
  - Dental caries/periodontal disease result from SHIFT in
    balance of normal resident microbiota (DYSBIOSIS)
  - Specific organisms normally present in low numbers
    can outgrow under altered environmental conditions
  - Perturbations can be: immunologic (neutrophil dysfunction,
    immune suppression) or non-immunologic (xerostomia,
    diet change)
  - Goal: maintaining microbial homeostasis, not eliminating
    all bacteria ("oral care practices should attempt to
    maintain plaque at levels compatible with health")
  - Describes the DYNAMIC relationship between oral
    microbiota and the host in health and disease
            |
            v
[4] THE COMMUNITY AS A PATHOGEN (DYSBIOSIS MODEL)
(Contemporary concept - Newman 14th Ed.)
  - Periodontitis results from a polymicrobial community
  - Not single organism but the COMMUNITY is pathogenic
  - Dysbiosis = deleterious alteration to the microbiota
  - "Keystone pathogen" concept: P. gingivalis, even at
    relatively low abundance in dental plaque, can cause
    dysbiosis by manipulating host immune responses
  - Interactions between the biofilm and host immune-
    inflammatory events drive disease progression

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14. MICROBIAL COMPOSITION IN HEALTH VS. DISEASE

Microbial Shift During Disease (Carranza 10th Ed.)

Bacteria in Chronic Periodontitis (Cultivation Studies)

• Porphyromonas gingivalis
• Tannerella forsythia (previously Bacteroides forsythus)
• Prevotella intermedia
• Campylobacter rectus
• Eikenella corrodens
• Fusobacterium nucleatum
• Aggregatibacter actinomycetemcomitans
• Parvimonas micra (previously Peptostreptococcus micros/Micromonas micra)
• Treponema and Eubacterium species

Microbial Composition - Subgingival Plaque by Pocket Depth

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15. CRITERIA FOR IDENTIFICATION OF PERIODONTAL PATHOGENS

Koch's Postulates (Classic)

1. Must be routinely isolated from diseased individuals
2. Must be grown in pure culture in the laboratory
3. Must produce a similar disease when inoculated into susceptible laboratory animals
4. Must be recovered from lesions in a diseased laboratory animal

1. Inability to culture all organisms associated with disease (e.g., many oral spirochetes)
2. Difficulties in defining and culturing sites of active disease
3. Lack of a good animal model system for the study of periodontitis

Socransky's Criteria for Periodontal Pathogens

1. Must be associated with disease - increases in the number of organisms at diseased sites
2. Must be eliminated or decreased in sites that demonstrate clinical resolution of disease with treatment
3. Must demonstrate a host response (alteration in host cellular or humoral immune response)
4. Must be capable of causing disease in experimental animal models
5. Must demonstrate virulence factors responsible for enabling the microorganism to cause destruction of periodontal tissues

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16. SITE-SPECIFICITY OF PLAQUE AND CLINICAL RELEVANCE

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17. PLAQUE-INDUCED GINGIVAL DISEASES (CLASSIFICATION)

Historical Terminology vs. Current Terminology (2017 World Workshop Update)

"Gingivitis that is associated with retained dental biofilm (plaque) formation is the most common form of gingival disease."

• Biofilm-induced gingival disease is the result of an interaction between the microorganisms found in the dental biofilm and the tissues and inflammatory cells of the host.
• The biofilm-host interaction can result in a spectrum of gingival tissue responses including continuing loss of collagen in response to the microbial challenge. However, the alveolar bone is not affected.
• Microbial biofilm is still the primary etiologic factor even when systemic factors modify the host response.

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18. ROLE OF BIOFILM IN PERIODONTAL PATHOGENESIS

Experimental Gingivitis Study (Löe, 1965)

• Dental plaque began to form quickly, and the amount of plaque increased with time.
• All subjects developed gingivitis.
• The inflammation resolved within 1 week of resuming hygiene measures.
• "Bacterial plaque was essential in the initiation of gingival inflammation." The authors concluded that bacterial plaque was essential in the initiation of gingival inflammation.

FLOWCHART: Role of Biofilm in Periodontal Pathogenesis (Newman 14th Ed.)

[SUBGINGIVAL BIOFILM forms and accumulates]
           |
           v
[LOW-GRADE CHRONIC INFLAMMATORY RESPONSE]
(not detectable macroscopically at the microscopic level)
           |
           v
[Neutrophils are chemotactically attracted]
  - Phagocytose and kill bacteria
  - Most bacteria eliminated at the JE level
  - "Low-grade defense" against plaque bacteria
           |
           v
[If biofilm challenge continues / increases]
           |
     +-----+-----+
     |           |
     v           v
[Gingivitis]  [If progressive: Periodontitis]
  Reversible   - Pocket deepens
  Alveolar     - Biofilm proliferates apically
  bone not     - Subgingival biofilm exploits niche
  affected     - Effective plaque control becomes
               more difficult
               - Alveolar bone destruction occurs
           |
           v
[Host immune-inflammatory response]
  PROTECTIVE intent but can result in
  considerable tissue damage:
  - MMPs / Collagenases
  - Cytokines (IL-1, TNF-alpha, PGE2)
  - RANKL -> osteoclast activation -> bone loss
           |
           v
[KEY CONCEPT (Newman 14th Ed.)]
  "Although plaque bacteria INITIATE and PERPETUATE
  the inflammatory response, MOST OF THE TISSUE
  DAMAGE results from the host immune-inflammatory
  response."

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19. BENEFITS OF RESIDENT ORAL MICROBIOTA (Ecological Perspective)

"Oral care practices should attempt to maintain plaque at levels compatible with health rather than eliminating dental plaque altogether."

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20. COMPARISON TABLE: DIFFERENT PERSPECTIVES ACROSS REFERENCES

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21. INDICES FOR MEASURING DENTAL PLAQUE

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22. FACTORS MODIFYING PLAQUE ACCUMULATION (LOCAL TOOTH-RELATED FACTORS)

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23. ORAL BIOFILM AND SYSTEMIC DISEASE (DYSBIOSIS)

• Aims to identify and characterize all members of the resident oral microbiota in health and disease.
• Data accessible in the Human Oral Microbiome Database (HOMD), which also feeds into the larger Human Microbiome Project.
• More recently: CORE (http://microbiome.osu.edu) - phylogenetically curated 16S rDNA database.

Oral-Systemic Axis Relevant to Biofilm:

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24. SUMMARY FLOWCHART: DENTAL PLAQUE/BIOFILM - CLINICAL SIGNIFICANCE

DENTAL PLAQUE (BIOFILM)
         |
    +----+-----+
    |           |
    v           v
SUPRAGINGIVAL      SUBGINGIVAL
  PLAQUE            PLAQUE
    |                  |
    |           +------+------+
    v           |             |
  Gingivitis  Tooth-       Tissue-
  (reversible) associated   associated
    |          |             |
    v          v             v
  Calculus  Root         TISSUE
  formation  caries    DESTRUCTION
                       Periodontitis
                       (irreversible
                        if untreated)
         |
         v
[DYSBIOSIS] - Shift in microbial ecology
    |
    v
HOST RESPONSE (Immune-inflammatory)
    |
    +- PROTECTIVE (Neutrophils, antibodies, cytokines)
    |
    +- DESTRUCTIVE (If excessive/prolonged)
         -> MMPs, RANKL, IL-1beta, TNF-alpha, PGE2
         -> Alveolar bone loss, attachment loss

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KEY EXAMINER KEYWORDS (QUICK REVISION)

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1. Carranza's Clinical Periodontology, 10th Edition (Carranza, Newman, Takei, Klokkevold) - Chapter 9: Dental Plaque and Calculus
2. Clinical Periodontology and Implant Dentistry, 6th Edition (Lindhe, Lang, Karring) - Chapter 8: Dental Biofilms (Marsh); Chapter 9: Dental Calculus; Chapter 10: Periodontal Infections
3. Newman & Carranza's Clinical Periodontology and Implantology, 14th Edition (Newman, Takei, Klokkevold, Carranza) - Chapter 10: Biofilm and Periodontal Microbiology; Chapter 5: Classification of Diseases

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What These Notes Cover (Summary for the Student)

• Every point is tagged to its source (Carranza 10th Ed., Lindhe/Lang 6th Ed., or Newman/Carranza 14th Ed.)
• Where references differ (e.g., 3-stage vs. 6-stage plaque formation, 2-zone vs. 4-layer subgingival biofilm architecture), both are presented with attribution

1. Definition and the recent "dental plaque" → "dental biofilm" terminology change (with verbatim textbook justification)
2. Composition - bacterial counts (10¹¹/gram), species diversity (>500), uncultivated organisms (30%), non-bacterial organisms
3. Classification - supragingival vs. subgingival; tooth-associated vs. tissue-associated
4. Plaque as a biofilm - structure, water channels, planktonic vs. biofilm state
5. Pellicle formation - with note that "acquired pellicle" is now a less preferred term
6. Biofilm formation flowchart - 6 sequential stages with all key organisms named
7. Growth dynamics - exponential curve, Day 4 plateau, 30% crown coverage, night reduction of 50%
8. Microbial complexes (Socransky) - Yellow, Purple, Green, Orange, Red complex with clinical associations
9. Coaggregation - mediators, inhibitors, specific interactions
10. Quorum sensing and eDNA - biofilm communication mechanisms
11. Antimicrobial resistance mechanisms - 6 mechanisms tabulated
12. Plaque hypothesis evolution - Nonspecific → Specific → Ecological → Community/Dysbiosis (with flowchart)
13. Microbial shift table (health → gingivitis → periodontitis)
14. Koch's vs. Socransky's criteria for periodontal pathogens
15. 2017 Classification update - Dental biofilm-induced gingivitis (replacing "plaque-induced")
16. Pathogenesis flowchart with host response
17. Comparison table across all three references on key topics
18. Key examiner keywords table for rapid revision