Periodontology

Ecological Succession of Biofilm in Dental Plaque

Overview of Biofilm Formation

Biofilm formation on tooth surfaces is a dynamic process characterized by ecological succession, where microbial communities evolve over time. This process transitions from an early aerobic environment dominated by gram-positive facultative species to a later stage characterized by a highly oxygen-deprived environment where gram-negative anaerobic microorganisms predominate.

Stages of Biofilm Development

Initial Colonization:
- Environment: The initial phase occurs in an aerobic environment.
- Primary Colonizers:
  - The first bacteria to colonize the pellicle-coated tooth surface are predominantly gram-positive facultative microorganisms.
  - Key Species:
    - Actinomyces viscosus
    - Streptococcus sanguis
- Characteristics:
  - These bacteria can thrive in the presence of oxygen and play a crucial role in the establishment of the biofilm.
Secondary Colonization:
- Environment: As the biofilm matures, the environment becomes increasingly anaerobic due to the metabolic activities of the initial colonizers.
- Secondary Colonizers:
  - These microorganisms do not initially colonize clean tooth surfaces but adhere to the existing bacterial cells in the plaque mass.
  - Key Species:
    - Prevotella intermedia
    - Prevotella loescheii
    - Capnocytophaga spp.
    - Fusobacterium nucleatum
    - Porphyromonas gingivalis
- Coaggregation:
  - Secondary colonizers adhere to primary colonizers through a process known as coaggregation, which involves specific interactions between bacterial cells.
Coaggregation Examples:
- Coaggregation is a critical mechanism that facilitates the establishment of complex microbial communities within the biofilm.
- Well-Known Examples:
  - Fusobacterium nucleatum with Streptococcus sanguis
  - Prevotella loescheii with Actinomyces viscosus
  - Capnocytophaga ochracea with Actinomyces viscosus

Implications of Ecological Succession

Microbial Diversity: The transition from gram-positive to gram-negative organisms reflects an increase in microbial diversity and complexity within the biofilm.
Pathogenic Potential: The accumulation of anaerobic gram-negative bacteria is associated with the development of periodontal diseases, as these organisms can produce virulence factors that contribute to tissue destruction and inflammation.
Biofilm Stability: The interactions between different bacterial species through coaggregation enhance the stability and resilience of the biofilm, making it more challenging to remove through mechanical cleaning.

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Subgingival and Supragingival Calculus

Overview of Calculus Formation

Calculus, or tartar, is a hardened form of dental plaque that can form on both supragingival (above the gum line) and subgingival (below the gum line) surfaces. Understanding the differences between these two types of calculus is essential for effective periodontal disease management.

Subgingival Calculus

Color and Composition:
- Appearance: Subgingival calculus is typically dark green or dark brown in color.
- Causes of Color:
  - The dark color is likely due to the presence of matrix components that differ from those found in supragingival calculus.
  - It is influenced by iron heme pigments that are associated with the bleeding of inflamed gingiva, reflecting the inflammatory state of the periodontal tissues.
Formation Factors:
- Matrix Components: The subgingival calculus matrix contains blood products, which contribute to its darker coloration.
- Bacterial Environment: The subgingival environment is typically more anaerobic and harbors different bacterial species compared to supragingival calculus.

Supragingival Calculus

Formation Factors:
- Dependence on Plaque and Saliva:
  - The degree of supragingival calculus formation is primarily influenced by the amount of bacterial plaque present and the secretion of salivary glands.
  - Increased plaque accumulation leads to greater calculus formation.
Inorganic Components:
- Source: The inorganic components of supragingival calculus are mainly derived from saliva.
- Composition: These components include minerals such as calcium and phosphate, which contribute to the calcification process of plaque.

Comparison of Inorganic Components

Supragingival Calculus:
- Inorganic components are primarily sourced from saliva, which contains minerals that facilitate the formation of calculus on the tooth surface.
Subgingival Calculus:
- In contrast, the inorganic components of subgingival calculus are derived mainly from crevicular fluid (serum transudate), which seeps into the gingival sulcus and contains various proteins and minerals from the bloodstream.

Aggressive Periodontitis (formerly Juvenile Periodontitis)

Historical Names: Previously referred to as periodontosis, deep cementopathia, diseases of eruption, Gottleib�s diseases, and periodontitis marginalis progressive.
Risk Factors:
- High frequency of Actinobacillus actinomycetemcomitans.
- Immune defects (functional defects of PMNs and monocytes).
- Autoimmunity and genetic factors.
- Environmental factors, including smoking.
Clinical Features:
- Vertical loss of alveolar bone around the first molars and incisors, typically beginning around puberty.
- Bone loss patterns often described as "target" or "bull" shaped lesions.

Bacterial Properties Involved in Evasion of Host Defense Mechanisms

Bacteria have evolved various strategies to evade the host's immune defenses, allowing them to persist and cause disease. Understanding these mechanisms is crucial for developing effective treatments and preventive measures against bacterial infections, particularly in the context of periodontal disease. This lecture will explore the bacterial species involved, their properties, and the biological effects of these properties on host defense mechanisms.

Host Defense Mechanisms and Bacterial Evasion Strategies

Specific Antibody Evasion
- Bacterial Species:
  - Porphyromonas gingivalis
  - Prevotella intermedia
  - Prevotella melaninogenica
  - Capnocytophaga spp.
- Bacterial Property:
  - IgA- and IgG-degrading proteases
- Biologic Effect:
  - Degradation of specific antibodies, which impairs the host's ability to mount an effective immune response against these bacteria.
Evasion of Polymorphonuclear Leukocytes (PMNs)
- Bacterial Species:
  - Aggregatibacter actinomycetemcomitans
  - Fusobacterium nucleatum
  - Porphyromonas gingivalis
  - Treponema denticola
- Bacterial Properties:
  - Leukotoxin: A toxin that can induce apoptosis in PMNs.
  - Heat-sensitive surface protein: May interfere with immune recognition.
  - Capsule: A protective layer that inhibits phagocytosis.
  - Inhibition of superoxide production: Reduces the oxidative burst necessary for bacterial killing.
- Biologic Effects:
  - Inhibition of PMN function, leading to decreased bacterial killing.
  - Induction of apoptosis (programmed cell death) in PMNs, reducing the number of immune cells available to fight infection.
  - Inhibition of phagocytosis, allowing bacteria to evade clearance.
Evasion of Lymphocytes
- Bacterial Species:
  - Aggregatibacter actinomycetemcomitans
  - Fusobacterium nucleatum
  - Tannerella forsythia
  - Prevotella intermedia
- Bacterial Properties:
  - Leukotoxin: Induces apoptosis in lymphocytes.
  - Cytolethal distending toxin: Affects cell cycle progression and induces cell death.
  - Heat-sensitive surface protein: May interfere with immune recognition.
  - Cytotoxin: Directly damages immune cells.
- Biologic Effects:
  - Killing of mature B and T cells, leading to a weakened adaptive immune response.
  - Nonlethal suppression of lymphocyte activity, impairing the immune response.
  - Impairment of lymphocyte function by arresting the cell cycle, leading to decreased responses to antigens and mitogens.
  - Induction of apoptosis in mononuclear cells and lymphocytes, further reducing immune capacity.
Inhibition of Interleukin-8 (IL-8) Production
- Bacterial Species:
  - Porphyromonas gingivalis
- Bacterial Property:
  - Inhibition of IL-8 production by epithelial cells.
- Biologic Effect:
  - Impairment of PMN response to bacteria, leading to reduced recruitment and activation of neutrophils at the site of infection.

Alveolar Process

The alveolar process is a critical component of the dental anatomy, providing support for the teeth and playing a vital role in periodontal health. Understanding its structure and composition is essential for dental professionals in diagnosing and treating various dental conditions.

Components of the Alveolar Process

External Plate of Cortical Bone:
- Description: The outer layer of the alveolar process is composed of cortical bone, which is dense and forms a protective outer shell.
- Composition:
  - Formed by Haversian bone, which consists of organized structures called osteons.
  - Compacted bone lamellae contribute to the strength and stability of the alveolar process.
Alveolar Bone Proper:
- Description: The inner socket wall of the alveolar process is known as the alveolar bone proper.
- Radiographic Appearance:
  - It is seen as the lamina dura on radiographs, appearing as a radiopaque line surrounding the tooth roots.
- Histological Features:
  - Contains a series of openings known as the cribriform plate.
  - These openings allow neurovascular bundles to connect the periodontal ligament with the central component of the alveolar bone, which is the cancellous bone.
Cancellous Bone:
- Description: Located between the external cortical bone and the alveolar bone proper, cancellous bone consists of trabecular structures.
- Function:
  - Acts as supporting alveolar bone, providing strength and flexibility to the alveolar process.
- Interdental Septum:
  - The interdental septum consists of cancellous supporting bone enclosed within a compact border, providing stability between adjacent teeth.

Structural Characteristics

Facial and Lingual Portions:
- Most of the facial and lingual portions of the tooth socket are formed by compact bone alone, providing robust support for the teeth.
Cancellous Bone Distribution:
- Cancellous bone surrounds the lamina dura in specific areas:
  - Apical Areas: The region at the tip of the tooth root.
  - Apicolingual Areas: The area where the root meets the lingual surface.
  - Interradicular Areas: The space between the roots of multi-rooted teeth.

PERIOTEST Device in Periodontal Assessment

The PERIOTEST device is a valuable tool used in dentistry to assess the mobility of teeth and the reaction of the periodontium to applied forces. This lecture covers the principles of the PERIOTEST device, its measurement scale, and its clinical significance in evaluating periodontal health.

Function: The PERIOTEST device measures the reaction of the periodontium to a defined percussion force applied to the tooth. This is done using a tapping instrument that delivers a controlled force to the tooth.

Contact Time: The contact time between the tapping head and the tooth varies between 0.3 and 2 milliseconds. This duration is typically shorter for stable teeth compared to mobile teeth, allowing for a quick assessment of tooth stability.

PERIOTEST Scale

The PERIOTEST scale ranges from -8 to +50, with specific ranges indicating different levels of tooth mobility:

Readings	Inference
-8 to 9	Clinically firm teeth
10 to 19	First distinguishable sign of movement
20 to 29	Crown deviates within 1 mm of its normal position
30 to 50	Mobility is readily observed

Clinical Significance

Assessment of Tooth Mobility:
The PERIOTEST device provides a quantitative measure of tooth mobility, which is essential for diagnosing periodontal disease and assessing the stability of teeth.

Correlation with Other Measurements:
The PERIOTEST values correlate well with:

Tooth Mobility Assessed with a Metric System: This allows for a standardized approach to measuring mobility, enhancing the reliability of assessments.
Degree of Periodontal Disease and Alveolar Bone Loss: Higher mobility readings often indicate more severe periodontal disease and greater loss of supporting bone, making the PERIOTEST a useful tool in monitoring disease progression.

Treatment Planning:
Understanding the mobility of teeth can aid in treatment planning, including decisions regarding periodontal therapy, splinting of mobile teeth, or extraction in cases of severe mobility.

Periodontal Diseases Associated with Neutrophil Disorders

Acute Necrotizing Ulcerative Gingivitis (ANUG)
- Description: A severe form of gingivitis characterized by necrosis of the interdental papillae, pain, and foul odor.
- Association: Neutrophil dysfunction can exacerbate the severity of ANUG, leading to rapid tissue destruction.
Localized Juvenile Periodontitis
- Description: A form of periodontitis that typically affects adolescents and is characterized by localized bone loss around the permanent teeth.
- Association: Impaired neutrophil function contributes to the pathogenesis of this condition.
Prepubertal Periodontitis
- Description: A rare form of periodontitis that occurs in children before puberty, leading to rapid attachment loss and bone destruction.
- Association: Neutrophil disorders can play a significant role in the development and progression of this disease.
Rapidly Progressive Periodontitis
- Description: A form of periodontitis characterized by rapid attachment loss and bone destruction, often occurring in young adults.
- Association: Neutrophil dysfunction may contribute to the aggressive nature of this disease.
Refractory Periodontitis
- Description: A form of periodontitis that does not respond to conventional treatment and continues to progress despite therapy.
- Association: Neutrophil disorders may be implicated in the persistent nature of this condition.

Periodontal Medicaments

Periodontal diseases often require adjunctive therapies to traditional mechanical treatments such as scaling and root planing. Various medicaments have been developed to enhance the healing process and control infection in periodontal tissues. This lecture will discuss several periodontal medicaments, their compositions, and their clinical applications.

1. Elyzol

Composition:
- Elyzol is an oil-based gel containing 25% metronidazole. It is formulated with glyceryl mono-oleate and sesame oil.
Clinical Use:
- Elyzol has been found to be equivalent to scaling and root planing in terms of effectiveness for treating periodontal disease.
- However, no adjunctive effects beyond those achieved with mechanical debridement have been demonstrated.

2. Actisite

Composition:
- Actisite consists of tetracycline-containing fibers.
- Each fiber has a diameter of 0.5 mm and contains 12.7 mg of tetracycline per 9 inches of fiber.
Clinical Use:
- The fibers are placed directly into periodontal pockets, where they release tetracycline over time, helping to reduce bacterial load and promote healing.

3. Arestin

Composition:
- Arestin contains minocycline, which is delivered as a biodegradable powder in a syringe.
Clinical Use:
- Arestin is indicated for the treatment of periodontal disease and is applied directly into periodontal pockets, where it provides localized antibiotic therapy.

4. Atridox

Composition:
- Atridox contains 10% doxycycline in a syringeable gel system that is biodegradable.
Clinical Use:
- The gel is injected into periodontal pockets, where it solidifies and releases doxycycline over time, aiding in the management of periodontal disease.

5. Dentamycin and Periocline

Composition:
- Both Dentamycin and Periocline contain 2% minocycline hydrochloride.
Clinical Use:
- These products are used similarly to other local delivery systems, providing localized antibiotic therapy to reduce bacterial infection in periodontal pockets.

6. Periochip

Composition:
- Periochip is a biodegradable chip that contains chlorhexidine.
Clinical Use:
- The chip is placed in the gingival crevice, where it releases chlorhexidine over time, providing antimicrobial action and helping to control periodontal disease.

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