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

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)

Significant Immune Findings in Periodontal Diseases

Periodontal diseases are associated with various immune responses that can influence disease progression and severity. Understanding these immune findings is crucial for diagnosing and managing different forms of periodontal disease.

Immune Findings in Specific Periodontal Diseases

1. Acute Necrotizing Ulcerative Gingivitis (ANUG):

   • Findings:
     • PMN (Polymorphonuclear neutrophil) chemotactic defect: This defect impairs the ability of neutrophils to migrate to the site of infection, compromising the immune response.
     • Elevated antibody titres to Prevotella intermedia and intermediate-sized spirochetes: Indicates an immune response to specific pathogens associated with the disease.

2. Pregnancy Gingivitis:

   • Findings:
     • No significant immune findings reported: While pregnancy gingivitis is common, it does not show distinct immune abnormalities compared to other forms of periodontal disease.

3. Adult Periodontitis:

   • Findings:
     • Elevated antibody titres to Porphyromonas gingivalis and other periodontopathogens: Suggests a heightened immune response to these specific bacteria.
     • Occurrence of immune complexes in tissues: Indicates an immune reaction that may contribute to tissue damage.
     • Immediate hypersensitivity to gingival bacteria: Reflects an exaggerated immune response to bacterial antigens.
     • Cell-mediated immunity to gingival bacteria: Suggests involvement of T-cells in the immune response against periodontal pathogens.

4. Juvenile Periodontitis:

   • Localized Juvenile Periodontitis (LJP):
     • Findings:
       • PMN chemotactic defect and depressed phagocytosis: Impairs the ability of neutrophils to respond effectively to bacterial invasion.
       • Elevated antibody titres to Actinobacillus actinomycetemcomitans: Indicates an immune response to this specific pathogen.
   • Generalized Juvenile Periodontitis (GJP):
     • Findings:
       • PMN chemotactic defect and depressed phagocytosis: Similar to LJP, indicating a compromised immune response.
       • Elevated antibody titres to Porphyromonas gingivalis: Suggests an immune response to this pathogen.

5. Prepubertal Periodontitis:

   • Findings:
     • PMN chemotactic defect and depressed phagocytosis: Indicates impaired neutrophil function.
     • Elevated antibody titres to Actinobacillus actinomycetemcomitans: Suggests an immune response to this pathogen.

6. Rapid Periodontitis:

   • Findings:
     • Suppressed or enhanced PMN or monocyte chemotaxis: Indicates variability in immune response among individuals.
     • Elevated antibody titres to several gram-negative bacteria: Reflects an immune response to multiple pathogens.

7. Refractory Periodontitis:

   • Findings:
     • Reduced PMN chemotaxis: Indicates impaired neutrophil migration, which may contribute to disease persistence despite treatment.

8. Desquamative Gingivitis:

   • Findings:
     • Diagnostic or characteristic immunopathology in two-thirds of cases: Suggests an underlying immune mechanism.
     • Autoimmune etiology in cases resulting from pemphigus and pemphigoid: Indicates that some cases may be due to autoimmune processes affecting the gingival tissue.

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.

Periodontal Fibers

Periodontal fibers play a crucial role in maintaining the integrity of the periodontal ligament and supporting the teeth within the alveolar bone. Understanding the different groups of periodontal fibers is essential for comprehending their functions in periodontal health and disease.

1. Gingivodental Group

• Location:
  • Present on the facial, lingual, and interproximal surfaces of the teeth.
• Attachment:
  • These fibers are embedded in the cementum just beneath the epithelium at the base of the gingival sulcus.
• Function:
  • They help support the gingiva and maintain the position of the gingival margin.

2. Circular Group

• Location:
  • These fibers course through the connective tissue of the marginal and interdental gingiva.
• Attachment:
  • They encircle the tooth in a ring-like fashion.
• Function:
  • The circular fibers help maintain the contour of the gingiva and provide support to the marginal gingiva.

3. Transseptal Group

• Location:
  • Located interproximally, these fibers extend between the cementum of adjacent teeth.
• Attachment:
  • They lie in the area between the epithelium at the base of the gingival sulcus and the crest of the interdental bone.
• Function:
  • The transseptal fibers are primarily responsible for the post-retention relapse of orthodontically positioned teeth.
  • They are sometimes classified as principal fibers of the periodontal ligament.
  • Collectively, they form the interdental ligament of the arch, providing stability to the interproximal areas.

4. Semicircular Fibers

• Location:
  • These fibers attach to the proximal surface of a tooth immediately below the cementoenamel junction (CEJ).
• Attachment:
  • They go around the facial or lingual marginal gingiva of the tooth and attach to the other proximal surface of the same tooth.
• Function:
  • Semicircular fibers help maintain the position of the tooth and support the gingival tissue around it.

5. Transgingival Fibers

• Location:
  • These fibers attach to the proximal surface of one tooth and traverse the interdental space diagonally to attach to the proximal surface of the adjacent tooth.
• Function:
  • Transgingival fibers provide support across the interdental space, helping to maintain the position of adjacent teeth and the integrity of the gingival tissue.

Keratinized Gingiva and Attached Gingiva

The gingiva is an essential component of the periodontal tissues, providing support and protection for the teeth. Understanding the characteristics of keratinized gingiva, particularly attached gingiva, is crucial for assessing periodontal health.

Keratinized Gingiva

1. Definition:

   • Keratinized gingiva refers to the gingival tissue that is covered by a layer of keratinized epithelium, providing a protective barrier against mechanical and microbial insults.

2. Areas of Keratinized Gingiva:

   • Attached Gingiva:
     • Extends from the gingival groove to the mucogingival junction.
   • Marginal Gingiva:
     • The free gingival margin that surrounds the teeth.
   • Hard Palate:
     • The roof of the mouth, which is also covered by keratinized tissue.

Attached Gingiva

1. Location:

   • The attached gingiva is the portion of the gingiva that is firmly bound to the underlying alveolar bone.

2. Width of Attached Gingiva:

   • The width of attached gingiva varies based on location and can increase with age and in cases of supraerupted teeth.

3. Measurements:

   • Greatest Width:
     • Found in the incisor region:
       • Maxilla: 3.5 mm - 4.5 mm
       • Mandible: 3.3 mm - 3.9 mm
   • Narrowest Width:
     • Found in the posterior region:
       • Maxillary First Premolar: 1.9 mm
       • Mandibular First Premolar: 1.8 mm

Clinical Significance

• Importance of Attached Gingiva:

  • The width of attached gingiva is important for periodontal health, as it provides a buffer zone against mechanical forces and helps maintain the integrity of the periodontal attachment.
  • Insufficient attached gingiva may lead to increased susceptibility to periodontal disease and gingival recession.

• Assessment:

  • Regular assessment of the width of attached gingiva is essential during periodontal examinations to identify potential areas of concern and to plan appropriate treatment strategies.