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

Dental Plaque

Dental plaque is a biofilm that forms on the surfaces of teeth and is composed of a diverse community of microorganisms. The development of dental plaque occurs in stages, beginning with primary colonizers and progressing to secondary colonization and plaque maturation.

Primary Colonizers

• Timeframe:
  • Acquired within a few hours after tooth cleaning or exposure.
• Characteristics:
  • Predominantly gram-positive facultative microbes.
• Key Species:
  • Actinomyces viscosus
  • Streptococcus sanguis
• Adhesion Mechanism:
  • Primary colonizers adhere to the tooth surface through specific adhesins.
  • For example, A. viscosus possesses fimbriae that bind to proline-rich proteins in the dental pellicle, facilitating initial attachment.

Secondary Colonization and Plaque Maturation

• Microbial Composition:
  • As plaque matures, it becomes predominantly populated by gram-negative anaerobic microorganisms.
• Key Species:
  • Prevotella intermedia
  • Prevotella loescheii
  • Capnocytophaga spp.
  • Fusobacterium nucleatum
  • Porphyromonas gingivalis
• Coaggregation:
  • Coaggregation refers to the ability of different species and genera of plaque microorganisms to adhere to one another.
  • This process occurs primarily through highly specific stereochemical interactions of protein and carbohydrate molecules on cell surfaces, along with hydrophobic, electrostatic, and van der Waals forces.

Plaque Hypotheses

1. Specific Plaque Hypothesis:

   • This hypothesis posits that only certain types of plaque are pathogenic.
   • The pathogenicity of plaque depends on the presence or increase of specific microorganisms.
   • It predicts that plaque harboring specific bacterial pathogens leads to periodontal disease due to the production of substances that mediate the destruction of host tissues.

2. Nonspecific Plaque Hypothesis:

   • This hypothesis maintains that periodontal disease results from the overall activity of the entire plaque microflora.
   • It suggests that the elaboration of noxious products by the entire microbial community contributes to periodontal disease, rather than specific pathogens alone.

• Gingival Conditions:
  • Pregnancy gingivitis: Bleeding.
  • Desquamative gingivitis: Fiery red, painful sloughing.
  • Gingival hyperplasia: Most commonly caused by phenytoin.
  • Gingival enlargement covering 3/4 of tooth: Grade III.
• ANUG:
  • Organism: Spirochetes.
  • Seen in: Young adults.
  • First-day management: Avoid deep scaling.
  • Stages: Superficial zone = bacterial contamination.
• Granulomatous Lesion: Pyogenic granuloma.
• Gingival Recession: Most commonly due to traumatic brushing.

ANUG symptoms: Metallic taste, Pasty saliva, Punched – out papilla

Red complex: Porphyromonas, Treponema denticola, Tannerella forsythia

Drug enlargement: Phenytoin = Fibrotic, Cyclosporine = Vascular

Healing times: 2 – 7 (epithelialization), 21 (collagen), 1 week (flap attachment)

Bone graft memory: FDBA = Conductive, DFDBA = Inductive

Zones of Periodontal Disease

Listgarten described four distinct zones that can be observed in periodontal lesions. These zones may blend with each other and may not be present in every case.

Zones of Periodontal Disease

1. Zone 1: Bacterial Zone

   • Description: This is the most superficial zone, consisting of a diverse array of bacteria.
   • Characteristics:
     • The bacterial zone is primarily composed of various microbial species, including both pathogenic and non-pathogenic bacteria.
     • This zone is critical in the initiation and progression of periodontal disease, as the presence of specific bacteria can trigger inflammatory responses in the host.

2. Zone 2: Neutrophil Rich Zone

   • Description: This zone contains numerous leukocytes, predominantly neutrophils.
   • Characteristics:
     • The neutrophil-rich zone is indicative of the body’s immune response to the bacterial invasion.
     • Neutrophils are the first line of defense and play a crucial role in phagocytosing bacteria and releasing inflammatory mediators.
     • The presence of a high number of neutrophils suggests an acute inflammatory response, which is common in active periodontal disease.

3. Zone 3: Necrotic Zone

   • Description: This zone consists of disintegrated tissue cells, fibrillar material, remnants of collagen fibers, and spirochetes.
   • Characteristics:
     • The necrotic zone reflects tissue destruction and is characterized by the presence of dead or dying cells.
     • Fibrillar material and remnants of collagen fibers indicate the breakdown of the extracellular matrix, which is essential for maintaining periodontal tissue integrity.
     • Spirochetes, which are associated with more aggressive forms of periodontal disease, can also be found in this zone, contributing to the necrotic process.

4. Zone 4: Zone of Spirochetal Infiltration

   • Description: This zone consists of well-preserved tissue that is infiltrated with large and medium spirochetes.
   • Characteristics:
     • The zone of spirochetal infiltration indicates a more chronic phase of periodontal disease, where spirochetes invade the connective tissue.
     • The presence of well-preserved tissue suggests that while spirochetes are present, the tissue has not yet undergone extensive necrosis.
     • This zone is significant as it highlights the role of spirochetes in the pathogenesis of periodontal disease, particularly in cases of necrotizing periodontal diseases.

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.