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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

  1. 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.
  2. 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.
  3. 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

  1. 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.
  2. 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

  1. 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.
  2. 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.

Papillon-Lefevre Syndrome

Classic Triad

  1. Plantar Hyperkeratosis: Thickening of palms and soles
  2. Early-Onset Periodontitis: Severe periodontal destruction in primary and permanent dentition
  3. Dural Calcification: Intracranial calcifications

Genetics and Pathogenesis

  • Inheritance: Autosomal recessive
  • Gene: CTSC gene mutation affecting cathepsin C

Drug-Induced Gingival Hyperplasia

Most Common Causative Drug

  • Primary Agent: Phenytoin (anti-seizure medication)
  • Other Drugs: Cyclosporine, nifedipine, amlodipine

Grading System

  • Grade III: Three-quarters of tooth crown covered by hyperplastic tissue
  • Management: Drug substitution when possible, surgical reduction

Assessing New Attachment in Periodontal Therapy

Assessing new attachment following periodontal therapy is crucial for evaluating treatment outcomes and understanding the healing process. However, various methods of assessment have limitations that must be considered.

1. Periodontal Probing

  • Assessment Method: Periodontal probing is commonly used to measure probing depth and attachment levels before and after therapy.

  • Limitations:

    • Coronal Positioning of Probe Tip: After therapy, when the inflammatory lesion is resolved, the probe tip may stop coronal to the apical termination of the epithelium. This can lead to misleading interpretations of attachment gain.
    • Infrabony Defects: Following treatment of infrabony defects, new bone may form so close to the tooth surface that the probe cannot penetrate. This can result in a false impression of improved attachment levels.
    • Interpretation of Results: A gain in probing attachment level does not necessarily indicate a true gain of connective tissue attachment. Instead, it may reflect improved health of the surrounding tissues, which increases resistance to probe penetration.

2. Radiographic Analysis and Reentry Operations

  • Assessment Method: Radiographic analysis involves comparing radiographs taken before and after therapy to evaluate changes in bone levels. Reentry operations allow for direct inspection of the treated area.

  • Limitations:

    • Bone Fill vs. New Attachment: While radiographs can provide evidence of new bone formation (bone fill), they do not document the formation of new root cementum or a new periodontal ligament. Therefore, radiographic evidence alone cannot confirm the establishment of new attachment.

3. Histologic Methods

  • Assessment Method: Histologic analysis involves examining tissue samples under a microscope to assess the formation of new attachment, including new cementum and periodontal ligament.

  • Advantages:

    • Validity: Histologic methods are considered the only valid approach to assess the formation of new attachment accurately.
  • Limitations:

    • Pre-Therapy Assessment: Accurate assessment of the attachment level prior to therapy is essential for histologic analysis. If the initial attachment level cannot be determined with certainty, it may compromise the validity of the findings.

Gingivitis

Gingivitis is an inflammatory condition of the gingiva that can progress through several distinct stages. Understanding these stages is crucial for dental professionals in diagnosing and managing periodontal disease effectively. This lecture will outline the four stages of gingivitis, highlighting the key pathological changes that occur at each stage.

I. Initial Lesion

  • Characteristics:
    • Increased Permeability: The microvascular bed in the gingival tissues becomes more permeable, allowing for the passage of fluids and immune cells.
    • Increased GCF Flow: There is an increase in the flow of gingival crevicular fluid (GCF), which is indicative of inflammation and immune response.
    • PMN Cell Migration: The migration of polymorphonuclear leukocytes (PMNs) is facilitated by various adhesion molecules, including:
      • Intercellular Cell Adhesion Molecule 1 (ICAM-1)
      • E-selectin (ELAM-1) in the dentogingival vasculature.
  • Clinical Implications: This stage marks the beginning of the inflammatory response, where the body attempts to combat the initial bacterial insult.

II. Early Lesion

  • Characteristics:

    • Leukocyte Infiltration: There is significant infiltration of leukocytes, particularly lymphocytes, into the connective tissue of the junctional epithelium.
    • Fibroblast Degeneration: Several fibroblasts within the lesion exhibit signs of degeneration, indicating tissue damage.
    • Proliferation of Basal Cells: The basal cells of the junctional and sulcular epithelium begin to proliferate, which may be a response to the inflammatory process.
  • Clinical Implications: This stage represents a transition from initial inflammation to more pronounced tissue changes, with the potential for further progression if not managed.

III. Established Lesion

  • Characteristics:

    • Predominance of Plasma Cells and B Lymphocytes: There is a marked increase in plasma cells and B lymphocytes, indicating a more advanced immune response.
    • Increased Collagenolytic Activity: The activity of collagen-degrading enzymes increases, leading to the breakdown of collagen fibers in the connective tissue.
    • B Cell Subclasses: The B cells present in the established lesion are predominantly of the IgG1 and IgG3 subclasses, which are important for the immune response.
  • Clinical Implications: This stage is characterized by chronic inflammation, and if left untreated, it can lead to further tissue destruction and the transition to advanced lesions.

IV. Advanced Lesion

  • Characteristics:

    • Loss of Connective Tissue Attachment: There is significant loss of connective tissue attachment to the teeth, which can lead to periodontal pocket formation.
    • Alveolar Bone Loss: Extensive damage occurs to the alveolar bone, contributing to the overall loss of periodontal support.
    • Extensive Damage to Collagen Fibers: The collagen fibers in the gingival tissues are extensively damaged, further compromising the structural integrity of the gingiva.
    • Predominance of Plasma Cells: Plasma cells remain predominant, indicating ongoing immune activity and inflammation.
  • Clinical Implications: This stage represents the transition from gingivitis to periodontitis, where irreversible damage can occur. Early intervention is critical to prevent further progression and loss of periodontal support.

Anatomy and Histology of the Periodontium

Gingiva (normal clinical appearance): no muscles, no glands; keratinized

  • Color: coral pink but does vary with individuals and races due to cutaneous pigmentation
  • Papillary contour: pyramidal shape with one F and one L papilla and the col filling interproximal space to the contact area (col the starting place gingivitis)
  • Marginal contour: knife-edged and scalloped
  • Texture: stippled (orange-peel texture); blow air to dry out and see where stippling ends to see end of gingiva
  • Consistency: firm and resilient (push against it and won’t move); bound to underlying bone
  • Sulcus depth: 0-3mm
  • Exudate: no exudates (blood, pus, water)

  Anatomic and histological structures

Gingival unit: includes periodontium above alveolar crest of bone

a. Alveolar mucosa: histology- non-keratinized, stratified, squamous epithelium, submucosa with glands, loose connective tissue with collagen and elastin, muscles.  No epithelial ridges, no stratum granulosum (flattened cells below keratin layer)

b. Mucogingival junction: clinical demarcation between alveolar mucosa and attached gingiva

c. Attached gingiva: histology- keratinized, stratified, squamous epithelium with epithelial ridges (basal cell layer, prickle cell layer, granular cell layer (stratum granulosum), keratin layer); no submucosa

  • Dense connective tissue: predominantly collagen, bound to periosteum of bone by Sharpey fibers
  • Reticular fibers between collagen fibers and are continuous with reticulin in blood vessels

d. Free gingival groove: demarcation between attached and free gingiva; denotes base of gingival sulcus in normal gingiva; not always seen

e. Free gingival margin: area from free gingival groove to epithelial attachment (up and over ® inside)

  • Oral surface: stratified, squamous epithelium with epithelial ridges
  • Tooth side surface (sulcular epithelium): non-keratinized, stratified, squamous epithelium with no epithelial ridges (basal cell and prickle cell layers)

f. Gingival sulcus: space bounded by tooth surface, sulcular epithelium, and junctional epithelium; 0-3mm depth; space between epithelium and tooth

g. Dento-gingival junction: combination of epithelial and fibrous attachment

  • Junctional epithelium (epithelial attachment): attachment of epithelial cells by hemi-desmosomes and sticky substances (basal lamina- 800-1200 A, DAS-acid mucopolysaccharides, hyaluronic acid, chondroitin sulfate A, C, and B), to enamel, enamel and cementum, or cementum depending on stage of passive eruption.  Length ranges from 0.25-1.35mm.
  • Fibrous attachment: attachment of collagen fibers (Sharpey’s fibers) into cementum just beneath epithelial attachment; ~ 1mm thick

h. Nerve fibers: myelinated and non-myelinated (for pain) in connective tissue.  Both free and specialized endings for pain, touch pressure, and temperature -> proprioception.  If dentures, rely on TMJ.

i.Mesh of terminal argyophilic fibers (stain silver), some extending into epithelium

ii  Meissner-type corpuscles: pressure sensitive sensory nerve encased in CT

iii.Krause-type corpuscles: temperature receptors

iv. Encapsulated spindles

i. Gingival fibers:

i.  Gingivodental group:

  • Group I (A): from cementum to free gingival margin
  • Group II (B): from cementum to attached gingiva
  • Group III (C): from cementum over alveolar crest to periosteum on buccal and lingual plates

ii.  Circular (ligamentum circularis): encircles tooth in free gingiva

iii. Transeptal fibers: connects cementum of adjacent teeth, runs over interdental septum of alveolar bone.  Separates gingival unit from attachment apparatus.

Transeptal and Group III fibers the major defense against stuff getting into bone and ligament.

 

2.  Attachment apparatus: periodontium below alveolar crest of bone

Periodontal ligament: Sharpey’s fibers (collagen) connecting cementum to bone (bundle bone).  Few elastic and oxytalan fibers associated with blood vessels and embedded in cementum in cervical third of tooth.  Components divided as follows:

i. Alveolar crest fibers: from cementum just below CEJ apical to alveolar crest of bone

ii.Horizontal fibers: just apical to alveolar crest group, run at right angles to long axis of tooth from cementum horizontally to alveolar bone proper

iii.Oblique fibers: most numerous, from cementum run coronally to alveolar bone proper

iv. Apical fibers: radiate from cementum around apex of root apically to alveolar bone proper, form socket base

v. Interradicular fibers: found only between roots of multi-rooted teeth from cementum to alveolar bone proper

vi. Intermediate plexus: fibers which splice Sharpey’s fibers from bone and cementum

vii. Epithelial Rests of Malassez: cluster and individual epithelial cells close to cementum which are remnants of Hertwig’s epithelial root sheath; potential source of periodontal cysts.

viii. Nerve fibers: myelinated and non-myelinated; abundant supply of sensory free nerve endings capable of transmitting tactile pressure and pain sensation by trigeminal pathway and elongated spindle-like nerve fiber for proprioceptive impulses

Cementum: 45-50% inorganic; 50-55% organic (enamel is 97% inorganic; dentin 70% inorganic)

i.  Acellular cementum: no cementocytes; covers dentin (older) in coronal ½ to 2/3 of root, 16-60 mm thick

ii. Cellular cementum: cementocytes; covers dentin in apical ½ to 1/3 of root; also may cover acellular cementum areas in repair areas, 15-200 mm thick

iii. Precementum (cementoid): meshwork of irregularly arranged collagen in surface of cementum where formation starts

iv. Cemento-enamel junction (CEJ): 60-65% of time cementum overlaps enamel; 30% meet end-to-end; 5-10% space between

v. Cementum slower healing than bone or PDL.  If expose dentinotubules ® root sensitivity.

Alveolar bone: 65% inorganic, 35% organic

i. Alveolar bone proper (cribriform plate): lamina dura on x-ray; bundle bone receive Sharpey fibers from PDL

ii. Supporting bone: cancellous, trabecular (vascularized) and F and L plates of compact bone

Blood supply to periodontium

i. Alveolar blood vessels (inferior and superior)

A) Interalveolar: actually runs through bone then exits, main supply to alveolar bone and PDL

B) Supraperiosteal: just outside bone, to gingiva and alveolar bone

C) Dental (pulpal): to pulp and periapical area

D) Terminal vessels (supracrestal): anastomose of A and B above beneath the sulcular epithelium

E) PDL gets blood from: most from branches of interalveolar blood vessels from alveolar bone marrow spaces, supraperiosteal vessels when interalveolar vessels not present, pulpal (apical) vessels, supracrestal gingival vessels

ii. Lymphatic drainage: accompany blood vessels to regional lymph nodes (esp. submaxillary group)

  • Biological Width: Composed of connective tissue (1.07 mm) and epithelial attachment (0.97 mm).
  • Gingival Sulcus: Shallower in primary teeth; probing depth is 1 – 2 mm.
  • Gingival Blood Supply: Includes supraperiosteal arterioles, periodontal ligament vessels, and interdental septa arterioles.
  • GCF (Gingival Crevicular Fluid): Can be exudative or transudative; becomes exudative during inflammation.

Pediatric & Pregnancy Considerations

  • Safest Dental Care Period: Early second trimester.
  • Pregnancy Gingivitis: Characterized by pronounced bleeding.
  • Puberty-Related Changes: Increase in P. intermedia and Capnocytophaga.

Modified Gingival Index (MGI)

The Modified Gingival Index (MGI) is a clinical tool used to assess the severity of gingival inflammation. It provides a standardized method for evaluating the health of the gingival tissues, which is essential for diagnosing periodontal conditions and monitoring treatment outcomes. Understanding the scoring criteria of the MGI is crucial for dental professionals in their assessments.

Scoring Criteria for the Modified Gingival Index (MGI)

The MGI uses a scale from 0 to 4 to classify the degree of gingival inflammation. Each score corresponds to specific clinical findings:

  1. Score 0: Absence of Inflammation

    • Description: No signs of inflammation are present in the gingival tissues.
    • Clinical Significance: Indicates healthy gingiva with no bleeding or other pathological changes.
  2. Score 1: Mild Inflammation

    • Description:
      • Slight change in color (e.g., slight redness).
      • Little change in texture of any portion of the marginal or papillary gingival unit, but not affecting the entire unit.
    • Clinical Significance: Suggests early signs of gingival inflammation, which may require monitoring and preventive measures.
  3. Score 2: Mild Inflammation (Widespread)

    • Description:
      • Similar criteria as Score 1, but involving the entire marginal or papillary gingival unit.
    • Clinical Significance: Indicates a more widespread mild inflammation that may necessitate intervention to prevent progression.
  4. Score 3: Moderate Inflammation

    • Description:
      • Glazing of the gingiva.
      • Redness, edema, and/or hypertrophy of the marginal or papillary gingival unit.
    • Clinical Significance: Reflects a moderate level of inflammation that may require active treatment to reduce inflammation and restore gingival health.
  5. Score 4: Severe Inflammation

    • Description:
      • Marked redness, edema, and/or hypertrophy of the marginal or papillary gingival unit.
      • Presence of spontaneous bleeding, congestion, or ulceration.
    • Clinical Significance: Indicates severe gingival disease that requires immediate intervention and may be associated with periodontal disease.

Clinical Application of the MGI

  1. Assessment of Gingival Health:

    • The MGI provides a systematic approach to evaluate gingival health, allowing for consistent documentation of inflammation levels.
  2. Monitoring Treatment Outcomes:

    • Regular use of the MGI can help track changes in gingival health over time, assessing the effectiveness of periodontal treatments and preventive measures.
  3. Patient Education:

    • The MGI can be used to educate patients about their gingival health status, helping them understand the importance of oral hygiene and regular dental visits.
  4. Research and Epidemiological Studies:

    • The MGI is often used in clinical research to evaluate the prevalence and severity of gingival disease in populations.

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