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.

Gingival Crevicular Fluid (GCF)

Gingival crevicular fluid is an inflammatory exudate found in the gingival sulcus. It plays a significant role in periodontal health and disease.

A. Characteristics of GCF

Glucose Concentration: The glucose concentration in GCF is 3-4 times greater than that in serum, indicating increased metabolic activity in inflamed tissues.
Protein Content: The total protein content of GCF is much less than that of serum, reflecting its role as an inflammatory exudate.
Inflammatory Nature: GCF is present in clinically normal sulci due to the constant low-grade inflammation of the gingiva.

B. Drugs Excreted Through GCF

Tetracyclines and Metronidazole: These antibiotics are known to be excreted through GCF, making them effective for localized periodontal therapy.

C. Collection Methods for GCF

GCF can be collected using various techniques, including:

Absorbing Paper Strips/Blotter/Periopaper: These strips absorb fluid from the sulcus and are commonly used for GCF collection.
Twisted Threads: Placing twisted threads around and into the sulcus can help collect GCF.
Micropipettes: These can be used for precise collection of GCF in research settings.
Intra-Crevicular Washings: Flushing the sulcus with a saline solution can help collect GCF for analysis.

Periodontal Bone Grafts

Bone grafting is a critical procedure in periodontal surgery, aimed at restoring lost bone and supporting the regeneration of periodontal tissues.

1. Bone Blend

Bone blend is a mixture of cortical or cancellous bone that is procured using a trephine or rongeurs, placed in an amalgam capsule, and triturated to achieve a slushy osseous mass. This technique allows for the creation of smaller particle sizes, which enhances resorption and replacement with host bone.

Particle Size: The ideal particle size for bone blend is approximately 210 x 105 micrometers.

Rationale: Smaller particle sizes improve the chances of resorption and integration with the host bone, making the graft more effective.

2. Types of Periodontal Bone Grafts

A. Autogenous Grafts

Autogenous grafts are harvested from the patient�s own body, providing the best compatibility and healing potential.

Cortical Bone Chips
- History: First used by Nabers and O'Leary in 1965.
- Characteristics: Composed of shavings of cortical bone removed during osteoplasty and ostectomy from intraoral sites.
- Challenges: Larger particle sizes can complicate placement and handling, and there is a potential for sequestration. This method has largely been replaced by autogenous osseous coagulum and bone blend.
Osseous Coagulum and Bone Blend
- Technique: Intraoral bone is obtained using high- or low-speed round burs and mixed with blood to form an osseous coagulum (Robinson, 1969).
- Advantages: Overcomes disadvantages of cortical bone chips, such as inability to aspirate during collection and variability in quality and quantity of collected bone.
- Applications: Used in various periodontal procedures to enhance healing and regeneration.
Intraoral Cancellous Bone and Marrow
- Sources: Healing bony wounds, extraction sockets, edentulous ridges, mandibular retromolar areas, and maxillary tuberosity.
- Applications: Provides a rich source of osteogenic cells and growth factors for bone regeneration.
Extraoral Cancellous Bone and Marrow
- Sources: Obtained from the anterior or posterior iliac crest.
- Advantages: Generally offers the greatest potential for new bone growth due to the abundance of cancellous bone and marrow.

B. Bone Allografts

Bone allografts are harvested from donors and can be classified into three main types:

Undermineralized Freeze-Dried Bone Allograft (FDBA)
- Introduction: Introduced in 1976 by Mellonig et al.
- Process: Freeze drying removes approximately 95% of the water from bone, preserving morphology, solubility, and chemical integrity while reducing antigenicity.
- Efficacy: FDBA combined with autogenous bone is more effective than FDBA alone, particularly in treating furcation involvements.
Demineralized (Decalcified) FDBA
- Mechanism: Demineralization enhances osteogenic potential by exposing bone morphogenetic proteins (BMPs) in the bone matrix.
- Osteoinduction vs. Osteoconduction: Demineralized grafts induce new bone formation (osteoinduction), while undermineralized allografts facilitate bone growth by providing a scaffold (osteoconduction).
Frozen Iliac Cancellous Bone and Marrow
- Usage: Used sparingly due to variability in outcomes and potential complications.

Comparison of Allografts and Alloplasts

Clinical Outcomes: Both FDBA and DFDBA have been compared to porous particulate hydroxyapatite, showing little difference in post-treatment clinical parameters.
Histological Healing: Grafts of DFDBA typically heal with regeneration of the periodontium, while synthetic bone grafts (alloplasts) heal by repair, which may not restore the original periodontal architecture.

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.

Dental Calculus

Dental calculus, also known as tartar, is a hard deposit that forms on teeth due to the mineralization of dental plaque. Understanding the composition and crystal forms of calculus is essential for dental professionals in diagnosing and managing periodontal disease.

Crystal Forms in Dental Calculus

Common Crystal Forms:
- Dental calculus typically contains two or more crystal forms. The most frequently detected forms include:
  - Hydroxyapatite:
    - This is the primary mineral component of both enamel and calculus, constituting a significant portion of the calculus sample.
    - Hydroxyapatite is a crystalline structure that provides strength and stability to the calculus.
  - Octacalcium Phosphate:
    - Detected in a high percentage of supragingival calculus samples (97% to 100%).
    - This form is also a significant contributor to the bulk of calculus.
Other Crystal Forms:
- Brushite:
  - More commonly found in the mandibular anterior region of the mouth.
  - Brushite is a less stable form of calcium phosphate and may indicate a younger calculus deposit.
- Magnesium Whitlockite:
  - Typically found in the posterior areas of the mouth.
  - This form may be associated with older calculus deposits and can indicate changes in the mineral composition over time.
Variation with Age:
- The incidence and types of crystal forms present in calculus can vary with the age of the deposit.
- Younger calculus deposits may have a higher proportion of brushite, while older deposits may show a predominance of hydroxyapatite and magnesium whitlockite.

Clinical Significance

Understanding Calculus Formation:
- Knowledge of the crystal forms in calculus can help dental professionals understand the mineralization process and the conditions under which calculus forms.
Implications for Treatment:
- The composition of calculus can influence treatment strategies. For example, older calculus deposits may be more difficult to remove due to their hardness and mineral content.
Assessment of Periodontal Health:
- The presence and type of calculus can provide insights into a patient�s oral hygiene practices and periodontal health. Regular monitoring and removal of calculus are essential for preventing periodontal disease.
Research and Development:
- Understanding the mineral composition of calculus can aid in the development of new dental materials and treatments aimed at preventing calculus formation and promoting oral health.

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.

Erythema Multiforme

Characteristics: Erythema multiforme presents with "target" or "bull's eye" lesions, often associated with:
- Etiologic Factors:
  - Herpes simplex infection.
  - Mycoplasma infection.
  - Drug reactions (e.g., sulfonamides, penicillins, phenylbutazone, phenytoin).

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