NEET MDS Lessons
General Medicine
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.
Bone Graft Materials
Bone grafting is a critical procedure in periodontal and dental surgery, aimed at restoring lost bone and supporting the regeneration of periodontal tissues. Various materials can be used for bone grafting, each with unique properties and applications.
A. Osseous Coagulum
- Composition: Osseous coagulum is a mixture of bone dust and blood. It is created using small particles ground from cortical bone.
- Sources: Bone dust can be obtained from various
anatomical sites, including:
- Lingual ridge of the mandible
- Exostoses
- Edentulous ridges
- Bone distal to terminal teeth
- Application: This material is used in periodontal surgery to promote healing and regeneration of bone in areas affected by periodontal disease.
B. Bioactive Glass
- Composition: Bioactive glass consists of sodium and calcium salts, phosphates, and silicon dioxide.
- Function: It promotes bone regeneration by forming a bond with surrounding bone and stimulating cellular activity.
C. HTR Polymer
- Composition: HTR Polymer is a non-resorbable, microporous, biocompatible composite made from polymethyl methacrylate (PMMA) and polyhydroxymethacrylate.
- Application: This material is used in various dental and periodontal applications due to its biocompatibility and structural properties.
D. Other Bone Graft Materials
- Sclera: Used as a graft material due to its collagen content and biocompatibility.
- Cartilage: Can be used in certain grafting procedures, particularly in reconstructive surgery.
- Plaster of Paris: Occasionally used in bone grafting, though less common due to its non-biological nature.
- Calcium Phosphate Biomaterials: These materials are osteoconductive and promote bone healing.
- Coral-Derived Materials: Natural coral can be processed to create a scaffold for bone regeneration.
🟡 Jaundice & Liver Disorders
| Condition | Key Features |
|---|---|
| Unconjugated hyperbilirubinemia | No urine bilirubin; seen in hemolysis |
| Conjugated hyperbilirubinemia | Present in Dubin – Johnson syndrome |
| Crigler – Najjar Type II | Autosomal recessive |
| BSP test | Diagnoses Dubin – Johnson |
| ↑ 5’-Nucleotidase | Cholestasis marker |
| ↓ Alk Phosphatase | Seen in hypothyroidism |
🦠 Viral Hepatitis
- Hepatitis E: Feco-oral; dangerous in pregnancy
- Councilman bodies: Acute viral hepatitis
- Most chronic virus: Hepatitis C
- HBV infectivity: HBsAg + HBeAg
- Window period: ↓ HBsAg, ↑ anti-HBs
- Perinatal HBV transmission: 90% risk
- First marker in acute HBV: HBsAg
- HBV P gene: Codes reverse transcriptase
- Hepatitis A prophylaxis: Human Ig
- Most epidemic-prone hepatitis in India: Hepatitis E
Diagnosis Criteria
- FBS ≥ 126 mg/dL
- HbA1C > 6.5%
- eAG based on HbA1C
- Oral GTT 2-hr post-load: 140–199 mg/dL → Impaired Glucose Tolerance
- HbA1C 5.7–6.4% → Pre-diabetic range
Cushing's Syndrome
- Earliest feature: Loss of diurnal variation of cortisol
- High-dose dexamethasone suppression test: Differentiates pituitary adenoma vs ectopic ACTH
Adrenal Insufficiency (Addison's Disease)
- Most common cause in India: Tuberculosis
- Most common primary tumor metastasizing to adrenals: Melanoma
- Most confirmatory test: ACTH stimulation test
- Diagnostic: Low plasma cortisol (<3 mg/dL) at 8 AM + elevated ACTH (>200 pg/mL)
- Most common symptom: Asthenia (due to hypotension & hypoglycemia)
Progression from Gingivitis to Periodontitis
The transition from gingivitis to periodontitis is a critical process in periodontal disease progression. This lecture will outline the key stages involved in this progression, highlighting the changes in microbial composition, host response, and tissue alterations.
Pathway of Progression
-
Establishment and Maturation of Supragingival Plaque:
- The process begins with the formation of supragingival plaque, which is evident in gingivitis.
- As this plaque matures, it becomes more complex and can lead to changes in the surrounding tissues.
-
Migration of Periodontopathogenic Bacteria:
- When the microbial load overwhelms the local host immune response, pathogenic bacteria migrate subgingivally (below the gum line).
- This migration establishes a subgingival niche that is conducive to the growth of periodontopathogenic bacteria.
Initial Lesion
- Timeline:
- The initial lesion, characterized by subclinical gingivitis, appears approximately 2 to 4 days after the colonization of the gingival sulcus by bacteria.
- Clinical Manifestations:
- Vasculitis: Inflammation of blood vessels in the gingival tissue.
- Exudation of Serous Fluid: Increased flow of gingival crevicular fluid (GCF) from the gingival sulcus.
- Increased PMN Migration: Polymorphonuclear neutrophils (PMNs) migrate into the sulcus in response to the inflammatory process.
- Alteration of Junctional Epithelium: Changes occur at the base of the pocket, affecting the integrity of the junctional epithelium.
- Collagen Dissolution: Perivascular collagen begins to dissolve, contributing to tissue breakdown.
Early Lesion
- Timeline:
- The early lesion forms within 4 to 7 days after the initial lesion due to the continued accumulation of bacterial plaque.
- Characteristics:
- Leukocyte Accumulation: There is a significant increase in leukocytes at the site of acute inflammation, indicating an ongoing immune response.
- Cytopathic Alterations: Resident fibroblasts undergo cytopathic changes, affecting their function and viability.
- Collagen Loss: Increased collagen loss occurs within the marginal gingiva, contributing to tissue destruction.
- Proliferation of Basal Cells: The basal cells of the junctional epithelium proliferate in response to the inflammatory environment.
Contraindications and Limitations
Gingivectomy
- Major Contraindication: When pocket bottom is apical to mucogingival junction
- Risk: Inadequate attached gingiva post-surgery
Curettage Protocol
- Prerequisite: Should always be preceded by scaling and root planing
- Rationale: Reduce bacterial load before surgical intervention
GTR (Guided Tissue Regeneration)
Membrane Placement Technique
- Apical Extension: 3-4mm apical to defect margin
- Lateral Extension: 2-3mm laterally beyond defect
- Objective: Exclude epithelial and connective tissue cells
Implant Considerations
Placement Guidelines
- Distance from Mental Foramen: ≥5mm to avoid nerve damage
- Primary Stability: Critical for osseointegration
Micro-movement Tolerance
- Critical Threshold: >150μm causes fibrous tissue formation instead of osseointegration
- Clinical Implication: Importance of proper implant stability