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).

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

1. 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.

2. 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.

3. 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.

4. 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.

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

1. 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.

2. 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.

3. 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

1. 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.

2. 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.

3. 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.

4. 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.

Changes in Plaque pH After Sucrose Rinse

The pH of dental plaque is a critical factor in the development of dental caries and periodontal disease. Key findings from various studies that investigated the changes in plaque pH following carbohydrate rinses, particularly focusing on sucrose and glucose.

Key Findings from Studies

1. Monitoring Plaque pH Changes:

   • A study reported that changes in plaque pH after a sucrose rinse were monitored using plaque sampling, antimony and glass electrodes, and telemetry.
   • Results:
     • The minimum pH at approximal sites (areas between teeth) was approximately 0.7 pH units lower than that on buccal surfaces (outer surfaces of the teeth).
     • The pH at the approximal site remained below resting levels for over 120 minutes.
     • The area under the pH response curves from approximal sites was five times greater than that from buccal surfaces, indicating a more significant and prolonged acidogenic response in interproximal areas.

2. Stephan's Early Studies (1935):

   • Method: Colorimetric measurement of plaque pH suspended in water.
   • Findings:
     • The pH of 211 plaque samples ranged from 4.6 to 7.0.
     • The mean pH value was found to be 5.9, indicating a generally acidic environment in dental plaque.

3. Stephan's Follow-Up Studies (1940):

   • Method: Use of an antimony electrode to measure in situ plaque pH after rinsing with sugar solutions.
   • Findings:
     • A 10% solution of glucose or sucrose caused a rapid drop in plaque pH by about 2 units within 2 to 5 minutes, reaching values between 4.5 and 5.0.
     • A 1% lactose solution lowered the pH by 0.3 units, while a 1% glucose solution caused a drop of 1.5 units.
     • A 1% boiled starch solution resulted in a reduction of 1.5 pH units over 51 minutes.
     • In all cases, the pH tended to return to initial values within approximately 2 hours.

4. Investigation of Proximal Cavities:

   • Studies of actual proximal cavities opened mechanically showed that the lowest pH values ranged from 4.6 to 4.1.
   • After rinsing with a 10% glucose or sucrose solution, the pH in the plaque dropped to between 4.5 and 5.0 within 2 to 5 minutes and gradually returned to baseline levels within 1 to 2 hours.

Implications

• The studies highlight the significant impact of carbohydrate exposure, particularly sucrose and glucose, on the pH of dental plaque.
• The rapid drop in pH following carbohydrate rinses indicates an acidogenic response from plaque microorganisms, which can contribute to enamel demineralization and caries development.
• The prolonged acidic environment in approximal sites suggests that these areas may be more susceptible to caries due to the slower recovery of pH levels.

Sutures for Periodontal Flaps

Suturing is a critical aspect of periodontal surgery, particularly when managing periodontal flaps. The choice of suture material can significantly influence healing, tissue adaptation, and overall surgical outcomes.

1. Nonabsorbable Sutures

Nonabsorbable sutures are designed to remain in the tissue until they are manually removed. They are often used in situations where long-term support is needed.

A. Types of Nonabsorbable Sutures

1. Silk (Braided)

   • Characteristics:
     • Excellent handling properties and knot security.
     • Provides good tissue approximation.
   • Applications: Commonly used in periodontal surgeries due to its ease of use and reliability.

2. Nylon (Monofilament) (Ethilon)

   • Characteristics:
     • Strong and resistant to stretching.
     • Less tissue reactivity compared to silk.
   • Applications: Ideal for delicate tissues and areas requiring minimal tissue trauma.

3. ePTFE (Monofilament) (Gore-Tex)

   • Characteristics:
     • Biocompatible and non-reactive.
     • Excellent tensile strength and flexibility.
   • Applications: Often used in guided tissue regeneration procedures and in areas where long-term support is needed.

4. Polyester (Braided) (Ethibond)

   • Characteristics:
     • High tensile strength and good knot security.
     • Less pliable than silk.
   • Applications: Used in situations requiring strong sutures, such as in flap stabilization.

2. Absorbable Sutures

Absorbable sutures are designed to be broken down by the body over time, eliminating the need for removal. They are often used in periodontal surgeries where temporary support is sufficient.

A. Types of Absorbable Sutures

1. Surgical Gut

   • Plain Gut (Monofilament)

     • Absorption Time: Approximately 30 days.
     • Characteristics: Made from sheep or cow intestines; provides good tensile strength initially but loses strength quickly.
     • Applications: Suitable for soft tissue approximation where rapid absorption is desired.

   • Chromic Gut (Monofilament)

     • Absorption Time: Approximately 45 to 60 days.
     • Characteristics: Treated with chromium salts to delay absorption; retains strength longer than plain gut.
     • Applications: Used in areas where a longer healing time is expected.

2. Synthetic Absorbable Sutures

   • Polyglycolic Acid (Braided) (Vicryl, Ethicon)

     • Absorption Time: Approximately 16 to 20 days.
     • Characteristics: Provides good tensile strength and is absorbed predictably.
     • Applications: Commonly used in periodontal and oral surgeries due to its handling properties.

   • Dexon (Davis & Geck)

     • Characteristics: Similar to Vicryl; made from polyglycolic acid.
     • Applications: Used in soft tissue approximation and ligation.

   • Polyglycaprone (Monofilament) (Maxon)

     • Absorption Time: Similar to Vicryl.
     • Characteristics: Offers excellent tensile strength and is absorbed more slowly than other synthetic options.
     • Applications: Ideal for areas requiring longer support during healing.

Pathogens Implicated in Periodontal Diseases

Periodontal diseases are associated with a variety of pathogenic microorganisms. Below is a list of key pathogens implicated in different forms of periodontal disease, along with their associations:

General Pathogens Associated with Periodontal Diseases

• Actinobacillus actinomycetemcomitans:

  • Strongly associated with destructive periodontal disease.

• Porphyromonas gingivalis:

  • A member of the "black pigmented Bacteroides group" and a significant contributor to periodontal disease.

• Bacteroides forsythus:

  • Associated with chronic periodontitis.

• Spirochetes (Treponema denticola):

  • Implicated in various periodontal conditions.

• Prevotella intermedia/nigrescens:

  • Also belongs to the "black pigmented Bacteroides group" and is associated with several forms of periodontal disease.

• Fusobacterium nucleatum:

  • Plays a role in the progression of periodontal disease.

• Campylobacter rectus:

  • These organisms include members of the new genus Wolinella and are associated with periodontal disease.

Principal Bacteria Associated with Specific Periodontal Diseases

1. Adult Periodontitis:

   • Porphyromonas gingivalis
   • Prevotella intermedia
   • Bacteroides forsythus
   • Campylobacter rectus

2. Refractory Periodontitis:

   • Bacteroides forsythus
   • Porphyromonas gingivalis
   • Campylobacter rectus
   • Prevotella intermedia

3. Localized Juvenile Periodontitis (LJP):

   • Actinobacillus actinomycetemcomitans
   • Capnocytophaga

4. Periodontitis in Juvenile Diabetes:

   • Capnocytophaga
   • Actinobacillus actinomycetemcomitans

5. Pregnancy Gingivitis:

   • Prevotella intermedia

6. Acute Necrotizing Ulcerative Gingivitis (ANUG):

   • Prevotella intermedia
   • Intermediate-sized spirochetes