Platelet-Derived Growth Factor (PDGF)

Platelet-Derived Growth Factor (PDGF) is a crucial glycoprotein involved in various biological processes, particularly in wound healing and tissue repair. Understanding its role and mechanisms can provide insights into its applications in regenerative medicine and periodontal therapy.

Overview of PDGF

1. Definition:

   • PDGF is a glycoprotein that plays a significant role in cell growth, proliferation, and differentiation.

2. Source:

   • PDGF is carried in the alpha granules of platelets and is released during the process of blood clotting.

3. Discovery:

   • It was one of the first growth factors to be described in scientific literature.
   • Originally isolated from platelets, PDGF was found to exhibit mitogenic activity specifically in smooth muscle cells.

Functions of PDGF

1. Mitogenic Activity:

   • PDGF stimulates the proliferation of various cell types, including:
     • Smooth muscle cells
     • Fibroblasts
     • Endothelial cells
   • This mitogenic activity is essential for tissue repair and regeneration.

2. Role in Wound Healing:

   • PDGF is released at the site of injury and plays a critical role in:
     • Promoting cell migration to the wound site.
     • Stimulating the formation of new blood vessels (angiogenesis).
     • Enhancing the synthesis of extracellular matrix components, which are vital for tissue structure and integrity.

3. Involvement in Periodontal Healing:

   • In periodontal therapy, PDGF can be utilized to enhance healing in periodontal defects and promote regeneration of periodontal tissues.
   • It has been studied for its potential in guided tissue regeneration (GTR) and in the treatment of periodontal disease.

Clinical Applications

1. Regenerative Medicine:

   • PDGF is being explored in various regenerative medicine applications, including:
     • Bone regeneration
     • Soft tissue healing
     • Treatment of chronic wounds

2. Periodontal Therapy:

   • PDGF has been incorporated into certain periodontal treatment modalities to enhance healing and regeneration of periodontal tissues.
   • It can be used in conjunction with graft materials to improve outcomes in periodontal surgery.

Trauma from Occlusion

Trauma from occlusion refers to the injury sustained by periodontal tissues when occlusal forces exceed their adaptive capacity.

1. Trauma from Occlusion

• This term describes the injury that occurs to periodontal tissues when the forces exerted during occlusion (the contact between opposing teeth) exceed the ability of those tissues to adapt.
• Traumatic Occlusion: An occlusion that produces such injury is referred to as a traumatic occlusion. This can result from various factors, including malocclusion, excessive occlusal forces, or parafunctional habits (e.g., bruxism).

2. Clinical Signs of Trauma to the Periodontium

The most common clinical sign of trauma to the periodontium is:

• Increased Tooth Mobility: As the periodontal tissues are subjected to excessive forces, they may become compromised, leading to increased mobility of the affected teeth. This is often one of the first observable signs of trauma from occlusion.

3. Radiographic Signs of Trauma from Occlusion

Radiographic examination can reveal several signs indicative of trauma from occlusion:

1. Increased Width of Periodontal Space:

   • The periodontal ligament space may appear wider on radiographs due to the increased forces acting on the tooth, leading to a loss of attachment and bone support.

2. Vertical Destruction of Inter-Dental Septum:

   • Trauma from occlusion can lead to vertical bone loss in the inter-dental septa, which may be visible on radiographs as a reduction in bone height between adjacent teeth.

3. Radiolucency and Condensation of the Alveolar Bone:

   • Areas of radiolucency may indicate bone loss, while areas of increased radiopacity (condensation) can suggest reactive changes in the bone due to the stress of occlusal forces.

4. Root Resorption:

   • In severe cases, trauma from occlusion can lead to root resorption, which may be observed as a loss of root structure on radiographs.

Localized Aggressive Periodontitis and Necrotizing Ulcerative Gingivitis

Localized Aggressive Periodontitis (LAP)

Localized aggressive periodontitis, previously known as localized juvenile periodontitis, is characterized by specific microbial profiles and clinical features.

• Microbiota Composition:
  • The microbiota associated with LAP is predominantly composed of:
    • Gram-Negative, Capnophilic, and Anaerobic Rods.
  • Key Organisms:
    • Actinobacillus actinomycetemcomitans: The main organism involved in LAP.
    • Other significant organisms include:
      • Porphyromonas gingivalis
      • Eikenella corrodens
      • Campylobacter rectus
      • Bacteroides capillus
      • Spirochetes (various species).
  • Viral Associations:
    • Herpes viruses, including Epstein-Barr Virus-1 (EBV-1) and Human Cytomegalovirus (HCMV), have also been associated with LAP.

Necrotizing Ulcerative Gingivitis (NUG)

• Microbial Profile:
  • NUG is characterized by high levels of:
    • Prevotella intermedia
    • Spirochetes (various species).
• Clinical Features:
  • NUG presents with necrosis of the gingival tissue, pain, and ulceration, often accompanied by systemic symptoms.

Microbial Shifts in Periodontal Disease

When comparing the microbiota across different states of periodontal health, a distinct microbial shift can be identified as the disease progresses from health to gingivitis to periodontitis:

1. From Gram-Positive to Gram-Negative:

   • Healthy gingival sites are predominantly colonized by gram-positive bacteria, while diseased sites show an increase in gram-negative bacteria.

2. From Cocci to Rods (and Later to Spirochetes):

   • In health, cocci (spherical bacteria) are prevalent. As the disease progresses, there is a shift towards rod-shaped bacteria, and in advanced stages, spirochetes become more prominent.

3. From Non-Motile to Motile Organisms:

   • Healthy sites are often dominated by non-motile bacteria, while motile organisms increase in number as periodontal disease develops.

4. From Facultative Anaerobes to Obligate Anaerobes:

   • In health, facultative anaerobes (which can survive with or without oxygen) are common. In contrast, obligate anaerobes (which thrive in the absence of oxygen) become more prevalent in periodontal disease.

5. From Fermenting to Proteolytic Species:

   • The microbial community shifts from fermentative bacteria, which primarily metabolize carbohydrates, to proteolytic species that break down proteins, contributing to tissue destruction and inflammation.

Necrotizing Ulcerative Gingivitis (NUG)

Necrotizing Ulcerative Gingivitis (NUG), also known as Vincent's disease or trench mouth, is a severe form of periodontal disease characterized by the sudden onset of symptoms and specific clinical features.

Etiology and Predisposing Factors

• Sudden Onset: NUG is characterized by a rapid onset of symptoms, often following debilitating diseases or acute respiratory infections.
• Lifestyle Factors: Changes in living habits, such as prolonged work without adequate rest, poor nutrition, tobacco use, and psychological stress, are frequently noted in patient histories .
• Smoking: Smoking has been identified as a significant predisposing factor for NUG/NDP .
• Immune Compromise: Conditions that compromise the immune system, such as poor oral hygiene, smoking, and emotional stress, are major contributors to the development of NUG .

Clinical Presentation

• Symptoms: NUG presents with:
  • Punched-out, crater-like depressions at the crest of interdental papillae.
  • Marginal gingival involvement, with rare extension to attached gingiva and oral mucosa.
  • Grey, pseudomembranous slough covering the lesions.
  • Spontaneous bleeding upon slight stimulation of the gingiva.
  • Fetid odor and increased salivation.

Microbiology

• Mixed Bacterial Infection: NUG is caused by a complex of anaerobic bacteria, often referred to as the fusospirochetal complex, which includes:
  • Treponema vincentii
  • Treponema denticola
  • Treponema macrodentium
  • Fusobacterium nucleatum
  • Prevotella intermedia
  • Porphyromonas gingivalis

Treatment

1. Control of Acute Phase:

   • Clean the wound with an antibacterial agent.
   • Irrigate the lesion with warm water and 5% vol/vol hydrogen peroxide.
   • Prescribe oxygen-releasing mouthwash (e.g., hydrogen peroxide DPF, sodium perborate DPF) to be used thrice daily.
   • Administer oral metronidazole for 3 to 5 days. If sensitive to metronidazole, prescribe penicillin; if sensitive to both, consider erythromycin or clindamycin.
   • Use 2% chlorhexidine in select cases for a short duration.

2. Management of Residual Condition:

   • Remove predisposing local factors (e.g., overhangs).
   • Perform supra- and subgingival scaling.
   • Consider gingivoplasty to correct any residual gingival deformities.

Dark Field Microscopy in Periodontal Microbiology

Dark field microscopy and phase contrast microscopy are valuable techniques in microbiological studies, particularly in the field of periodontal research. These methods allow for the direct observation of bacteria in plaque samples, providing insights into their morphology and motility. This lecture will discuss the principles of dark field microscopy, its applications in periodontal disease assessment, and its limitations.

Dark Field Microscopy

• Definition: Dark field microscopy is a technique that enhances the contrast of unstained, transparent specimens, allowing for the visualization of live microorganisms in their natural state.
• Principle: The method uses a special condenser that directs light at an angle, creating a dark background against which the specimen appears bright. This allows for the observation of motility and morphology without the need for staining.

Applications in Periodontal Microbiology

1. Alternative to Culture Methods:

   • Dark field microscopy has been suggested as a rapid alternative to traditional culture methods for assessing bacterial populations in periodontal plaque samples. It allows for immediate observation of bacteria without the time-consuming process of culturing.

2. Assessment of Morphology and Motility:

   • The technique enables direct and rapid assessment of the morphology (shape and structure) and motility (movement) of bacteria present in plaque samples. This information can be crucial for understanding the dynamics of periodontal disease.

3. Indication of Periodontal Disease Status:

   • Dark field microscopy has been used to indicate the status of periodontal disease and the effectiveness of maintenance programs. By observing the presence and activity of specific bacteria, clinicians can gain insights into the health of periodontal tissues.

Limitations of Dark Field Microscopy

1. Analysis of Major Periodontal Pathogens:

   • While dark field microscopy can visualize motile bacteria, it is important to note that many major periodontal pathogens, such as Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Bacteroides forsythus, Eikenella corrodens, and Eubacterium species, are motile. However, the technique may not provide detailed information about their specific characteristics or pathogenic potential.

2. Differentiation of Treponema Species:

   • Dark field microscopy cannot differentiate between species of Treponema, which is a limitation when identifying specific pathogens associated with periodontal disease. This lack of specificity can hinder the ability to tailor treatment based on the exact microbial profile.

3. Limited Quantitative Analysis:

   • While dark field microscopy allows for qualitative observations, it may not provide quantitative data on bacterial populations, which can be important for assessing disease severity and treatment outcomes.

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).