NEET MDS Lessons
Periodontology
Bacterial Properties Involved in Evasion of Host Defense Mechanisms
Bacteria have evolved various strategies to evade the host's immune defenses, allowing them to persist and cause disease. Understanding these mechanisms is crucial for developing effective treatments and preventive measures against bacterial infections, particularly in the context of periodontal disease. This lecture will explore the bacterial species involved, their properties, and the biological effects of these properties on host defense mechanisms.
Host Defense Mechanisms and Bacterial Evasion Strategies
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Specific Antibody Evasion
- Bacterial Species:
- Porphyromonas gingivalis
- Prevotella intermedia
- Prevotella melaninogenica
- Capnocytophaga spp.
- Bacterial Property:
- IgA- and IgG-degrading proteases
- Biologic Effect:
- Degradation of specific antibodies, which impairs the host's ability to mount an effective immune response against these bacteria.
- Bacterial Species:
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Evasion of Polymorphonuclear Leukocytes (PMNs)
- Bacterial Species:
- Aggregatibacter actinomycetemcomitans
- Fusobacterium nucleatum
- Porphyromonas gingivalis
- Treponema denticola
- Bacterial Properties:
- Leukotoxin: A toxin that can induce apoptosis in PMNs.
- Heat-sensitive surface protein: May interfere with immune recognition.
- Capsule: A protective layer that inhibits phagocytosis.
- Inhibition of superoxide production: Reduces the oxidative burst necessary for bacterial killing.
- Biologic Effects:
- Inhibition of PMN function, leading to decreased bacterial killing.
- Induction of apoptosis (programmed cell death) in PMNs, reducing the number of immune cells available to fight infection.
- Inhibition of phagocytosis, allowing bacteria to evade clearance.
- Bacterial Species:
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Evasion of Lymphocytes
- Bacterial Species:
- Aggregatibacter actinomycetemcomitans
- Fusobacterium nucleatum
- Tannerella forsythia
- Prevotella intermedia
- Bacterial Properties:
- Leukotoxin: Induces apoptosis in lymphocytes.
- Cytolethal distending toxin: Affects cell cycle progression and induces cell death.
- Heat-sensitive surface protein: May interfere with immune recognition.
- Cytotoxin: Directly damages immune cells.
- Biologic Effects:
- Killing of mature B and T cells, leading to a weakened adaptive immune response.
- Nonlethal suppression of lymphocyte activity, impairing the immune response.
- Impairment of lymphocyte function by arresting the cell cycle, leading to decreased responses to antigens and mitogens.
- Induction of apoptosis in mononuclear cells and lymphocytes, further reducing immune capacity.
- Bacterial Species:
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Inhibition of Interleukin-8 (IL-8) Production
- Bacterial Species:
- Porphyromonas gingivalis
- Bacterial Property:
- Inhibition of IL-8 production by epithelial cells.
- Biologic Effect:
- Impairment of PMN response to bacteria, leading to reduced recruitment and activation of neutrophils at the site of infection.
- Bacterial Species:
Automated Probing Systems
Automated probing systems have become increasingly important in periodontal assessments, providing enhanced accuracy and efficiency in measuring pocket depths and clinical attachment levels. This lecture will focus on the Florida Probe System, the Foster-Miller Probe, and the Toronto Automated Probe, discussing their features, advantages, and limitations.
1. Florida Probe System
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Overview: The Florida Probe System is an automated probing system designed to facilitate accurate periodontal assessments. It consists of several components:
- Probe Handpiece: The instrument used to measure pocket depths.
- Digital Readout: Displays measurements in real-time.
- Foot Switch: Allows for hands-free operation.
- Computer Interface: Connects the probe to a computer for data management.
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Specifications:
- Probe Diameter: The end of the probe is 0.4 mm in diameter, allowing for precise measurements in periodontal pockets.
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Advantages:
- Constant Probing Force: The system applies a consistent force during probing, reducing variability in measurements.
- Precise Electronic Measurement: Provides accurate and reproducible measurements of pocket depths.
- Computer Storage of Data: Enables easy storage, retrieval, and analysis of patient data, facilitating better record-keeping and tracking of periodontal health over time.
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Disadvantages:
- Lack of Tactile Sensitivity: The automated nature of the probe means that clinicians do not receive tactile feedback, which can be important for assessing tissue health.
- Fixed Force Setting: The use of a fixed force setting throughout the mouth may not account for variations in tissue condition, potentially leading to inaccurate measurements or patient discomfort.
2. Foster-Miller Probe
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Overview: The Foster-Miller Probe is another automated probing system that offers unique features for periodontal assessment.
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Capabilities:
- Pocket Depth Measurement: This probe can measure pocket depths effectively.
- Detection of the Cemento-Enamel Junction (CEJ): It is capable of coupling pocket depth measurements with the detection of the CEJ, providing valuable information about clinical attachment levels.
3. Toronto Automated Probe
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Overview: The Toronto Automated Probe is designed to enhance the accuracy of probing in periodontal assessments.
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Specifications:
- Probing Mechanism: The sulcus is probed with a 0.5 mm nickel titanium wire that is extended under air pressure, allowing for gentle probing.
- Angular Control: The system controls angular discrepancies using a mercury tilt sensor, which limits angulation within ±30 degrees. This feature helps maintain consistent probing angles.
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Limitations:
- Reproducible Positioning: The probe requires reproducible positioning of the patient’s head, which can be challenging in some clinical settings.
- Limited Access: The design may not easily accommodate measurements of second or third molars, potentially limiting its use in comprehensive periodontal assessments.
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
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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.
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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:
Attached Gingiva
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Location:
- The attached gingiva is the portion of the gingiva that is firmly bound to the underlying alveolar bone.
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Width of Attached Gingiva:
- The width of attached gingiva varies based on location and can increase with age and in cases of supraerupted teeth.
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Measurements:
- Greatest Width:
- Found in the incisor region:
- Maxilla: 3.5 mm - 4.5 mm
- Mandible: 3.3 mm - 3.9 mm
- Found in the incisor region:
- Narrowest Width:
- Found in the posterior region:
- Maxillary First Premolar: 1.9 mm
- Mandibular First Premolar: 1.8 mm
- Found in the posterior region:
- Greatest Width:
Clinical Significance
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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.
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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.
Gracey Curettes
Gracey curettes are specialized instruments designed for periodontal therapy, particularly for subgingival scaling and root planing. Their unique design allows for optimal adaptation to the complex anatomy of the teeth and surrounding tissues. This lecture will cover the characteristics, specific uses, and advantages of Gracey curettes in periodontal practice.
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Gracey curettes are area-specific curettes that come in a set of instruments, each designed and angled to adapt to specific anatomical areas of the dentition.
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Purpose: They are considered some of the best instruments for subgingival scaling and root planing due to their ability to provide excellent adaptation to complex root anatomy.
Specific Gracey Curette Designs and Uses
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Gracey 1/2 and 3/4:
- Indication: Designed for use on anterior teeth.
- Application: Effective for scaling and root planing in the anterior region, allowing for precise access to the root surfaces.
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Gracey 5/6:
- Indication: Suitable for anterior teeth and premolars.
- Application: Versatile for both anterior and premolar areas, providing effective scaling in these regions.
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Gracey 7/8 and 9/10:
- Indication: Designed for posterior teeth, specifically for facial and lingual surfaces.
- Application: Ideal for accessing the buccal and lingual surfaces of posterior teeth, ensuring thorough cleaning.
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Gracey 11/12:
- Indication: Specifically designed for the mesial surfaces of posterior teeth.
- Application: Allows for effective scaling of the mesial aspects of molars and premolars.
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Gracey 13/14:
- Indication: Designed for the distal surfaces of posterior teeth.
- Application: Facilitates access to the distal surfaces of molars and premolars, ensuring comprehensive treatment.
Key Features of Gracey Curettes
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Area-Specific Design: Each Gracey curette is tailored for specific areas of the dentition, allowing for better access and adaptation to the unique contours of the teeth.
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Offset Blade: Unlike universal curettes, the blade of a Gracey curette is not positioned at a 90-degree angle to the lower shank. Instead, the blade is angled approximately 60 to 70 degrees from the lower shank, which is referred to as an "offset blade." This design enhances the instrument's ability to adapt to the tooth surface and root anatomy.
Advantages of Gracey Curettes
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Optimal Adaptation: The area-specific design and offset blade allow for better adaptation to the complex anatomy of the roots, making them highly effective for subgingival scaling and root planing.
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Improved Access: The angled blades enable clinicians to access difficult-to-reach areas, such as furcations and concavities, which are often challenging with standard instruments.
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Enhanced Efficiency: The design of Gracey curettes allows for more efficient removal of calculus and biofilm from root surfaces, contributing to improved periodontal health.
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Reduced Tissue Trauma: The precise design minimizes trauma to the surrounding soft tissues, promoting better healing and patient comfort.
Gingival crevicular fluid is an inflammatory exudate found in the gingival sulcus. It plays a significant role in periodontal health and disease.
A. Characteristics of GCF
- Glucose Concentration: The glucose concentration in GCF is 3-4 times greater than that in serum, indicating increased metabolic activity in inflamed tissues.
- Protein Content: The total protein content of GCF is much less than that of serum, reflecting its role as an inflammatory exudate.
- Inflammatory Nature: GCF is present in clinically normal sulci due to the constant low-grade inflammation of the gingiva.
B. Drugs Excreted Through GCF
- Tetracyclines and Metronidazole: These antibiotics are known to be excreted through GCF, making them effective for localized periodontal therapy.
C. Collection Methods for GCF
GCF can be collected using various techniques, including:
- Absorbing Paper Strips/Blotter/Periopaper: These strips absorb fluid from the sulcus and are commonly used for GCF collection.
- Twisted Threads: Placing twisted threads around and into the sulcus can help collect GCF.
- Micropipettes: These can be used for precise collection of GCF in research settings.
- Intra-Crevicular Washings: Flushing the sulcus with a saline solution can help collect GCF for analysis.
Theories Regarding the Mineralization of Dental Calculus
Dental calculus, or tartar, is a hard deposit that forms on teeth due to the mineralization of dental plaque. Understanding the mechanisms by which plaque becomes mineralized is essential for dental professionals in managing periodontal health. The theories regarding the mineralization of calculus can be categorized into two main mechanisms: mineral precipitation and the role of seeding agents.
1. Mineral Precipitation
Mineral precipitation involves the local rise in the saturation of calcium and phosphate ions, leading to the formation of calcium phosphate salts. This process can occur through several mechanisms:
A. Rise in pH
- Mechanism: An increase in the pH of saliva can lead to the precipitation of calcium phosphate salts by lowering the precipitation constant.
- Causes:
- Loss of Carbon Dioxide: Bacterial activity in dental plaque can lead to the loss of CO2, resulting in an increase in pH.
- Formation of Ammonia: The degradation of proteins by plaque bacteria can produce ammonia, further elevating the pH.
B. Colloidal Proteins
- Mechanism: Colloidal proteins in saliva bind calcium and phosphate ions, maintaining a supersaturated solution with respect to calcium phosphate salts.
- Process:
- When saliva stagnates, these colloids can settle out, disrupting the supersaturated state and leading to the precipitation of calcium phosphate salts.
C. Enzymatic Activity
- Phosphatase:
- This enzyme, released from dental plaque, desquamated epithelial cells, or bacteria, hydrolyzes organic phosphates in saliva, increasing the concentration of free phosphate ions and promoting mineralization.
- Esterase:
- Present in cocci, filamentous organisms, leukocytes, macrophages, and desquamated epithelial cells, esterase can hydrolyze fatty esters into free fatty acids.
- These fatty acids can form soaps with calcium and magnesium, which are subsequently converted into less-soluble calcium phosphate salts, facilitating calcification.
2. Seeding Agents and Heterogeneous Nucleation
The second theory posits that seeding agents induce small foci of calcification that enlarge and coalesce to form a calcified mass. This concept is often referred to as the epitactic concept or heterogeneous nucleation.
A. Role of Seeding Agents
- Unknown Agents: The specific seeding agents involved in calculus formation are not fully understood, but it is believed that the intercellular matrix of plaque plays a significant role.
- Carbohydrate-Protein Complexes:
- These complexes may initiate calcification by chelating calcium from saliva and binding it to form nuclei that promote the deposition of minerals.
Clinical Implications
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Understanding Calculus Formation:
- Knowledge of the mechanisms behind calculus mineralization can help dental professionals develop effective strategies for preventing and managing calculus formation.
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Preventive Measures:
- Maintaining good oral hygiene practices can help reduce plaque accumulation and the conditions that favor mineralization, such as stagnation of saliva and elevated pH.
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Treatment Approaches:
- Understanding the role of enzymes and proteins in calculus formation may lead to the development of therapeutic agents that inhibit mineralization or promote the dissolution of existing calculus.
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Research Directions:
- Further research into the specific seeding agents and the biochemical processes involved in calculus formation may provide new insights into preventing and treating periodontal disease.
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.