NEET MDS Lessons
General Medicine
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
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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.
- Hydroxyapatite:
- Dental calculus typically contains two or more crystal forms. The
most frequently detected forms include:
-
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.
- Brushite:
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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
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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.
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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.
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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.
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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.
🧬 Risk Factors
- Increased homocysteine levels
- Raised lipoprotein(a)
- Nephrotic syndrome increases CAD risk
- Unsaturated fatty acid intake: Protective
- Best probability predictor in elderly: LDL/HDL ratio
⚕️ Diagnosis & Presentation
| Condition | Diagnostic Best Practice |
|---|---|
| Angina pectoris | History |
| Stable angina | Cardiac markers unchanged |
| Acute MI | Tall T wave (earliest ECG sign) |
| MI ≥12 hrs post-onset | Test of choice: Cardiac troponin |
| Prinzmetal’s angina | First-line agent: Nitrates |
| Intraoperative MI | Transesophageal echocardiography |
| Best biomarker of MI | Troponin T |
| WHO MI criteria | Echo not part of official criteria |
🧪 Enzymes & Drugs
- Enzyme ↑ at 4 – 6 hrs, ↓ in 3 – 4 days: CPK
- Stress ECHO agent: Dobutamine
- Intervention of choice: Streptokinase + Heparin
- Thrombolytics window: Within 12 hrs of MI
🚨 Prognosis & Complications
- Day 1: Maximum MI mortality
- Post-MI valvular lesion: Mitral regurgitation
- Best predictor of morbidity: LVEF
- Fatal thrombolysis complication: Intracranial hemorrhage
- LAD artery nicknamed: Widow’s artery
Gingival Crevicular Fluid is a serum-like exudate that flows from the gingival sulcus into the oral cavity. It serves as a crucial diagnostic medium and plays a vital role in the host defense mechanism against periodontal pathogens.
Immunological Characteristics
- Predominant Immunoglobulin: IgG (contrasts with saliva where IgA predominates)
- T:B Lymphocyte Ratio: 1:3 (higher B cell concentration indicates active antibody production)
- Inflammatory Nature: Primarily exudative, reflecting the body's response to bacterial challenge
Clinical Significance
- Drug Expression: Tetracycline and Metronidazole are expressed in GCF, making it useful for targeted antimicrobial therapy
- Diagnostic Value: GCF volume and composition change with gingival inflammation, serving as biomarkers for periodontal disease progression
- Collection Methods: Non-invasive collection using absorbent papers or micropipettes for research and diagnostic purposes
Laser Classifications
Hard Tissue Lasers
- Er:YAG and Er:YSGG: Highest water absorption coefficients
- Applications: Calculus removal, root surface modification, bone surgery
Soft Tissue Applications
- CO2 Laser: Excellent for soft tissue procedures
- Diode Lasers: Hemostasis and bacterial reduction
Microsurgery Principles
Wound Approximation
- Technique: Butt joint approximation for optimal healing
- Instrumentation: Instruments weighing ≤15-20g for precision
- Attached Gingiva Width:
- Maxillary incisors: 3.5 – 4.5 mm
- Mandibular incisors: 3.3 – 3.9 mm
- Least in premolars (~1.8 – 1.9 mm)
- Cementum:
- Thickest in apical third and furcation (150 – 200 µm)
- Acellular cementum: cervical third
- Cellular cementum: forms after occlusal contact
- PDL Fibres:
- Principal: Type I collagen
- Reticular: Type III collagen
- Oblique fibres: Largest group, resist vertical forces
- Transseptal fibres: Reconstructed post bone loss
- Alveolar crest fibres: Prevent extrusion
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
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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.
- Characteristics:
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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.
- Characteristics:
-
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.
- Characteristics:
-
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.
- Characteristics:
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
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Surgical Gut
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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.
-
-
Synthetic Absorbable Sutures
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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.
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Calculus Composition
- Brushite: More common in mandibular anterior
- Magnesium whitlockite: More common in posterior
- Ca:P ratio: Higher subgingivally
- Mineralization: 50% in 2 days, 60 – 90% in 12 days
Microbiology
- First colonizers: S. salivarius and S. mitis
- Red complex: P. gingivalis, T. denticola, T. forsythia (cause BOP)
- Growth enhancement: P. gingivalis grows better with succinate (C. ochracea) and protoheme (C. rectus)
Pellicle Structure
- Basal layer: Thin, difficult to remove
- Globular layer: 1 μm thick, easier to detach
Bacterial Recognition
- Gram positive: Activate TLR2 → IL – 8
- Gram negative: Activate TLR4 → TNF – α