NEET MDS Lessons
Oral and Maxillofacial Surgery
1. Radical Neck Dissection
- Complete removal of all ipsilateral
cervical lymph node groups (levels I-V) and three key non-lymphatic
structures:
- Internal jugular vein
- Sternocleidomastoid muscle
- Spinal accessory nerve
- Indication: Typically performed for extensive lymphatic involvement.
2. Modified Radical Neck Dissection
- Similar to radical neck dissection in terms
of lymph node removal (levels I-V) but with preservation of one or more of
the following structures:
- Type I: Preserves the spinal accessory nerve.
- Type II: Preserves the spinal accessory nerve and the sternocleidomastoid muscle.
- Type III: Preserves the spinal accessory nerve, sternocleidomastoid muscle, and internal jugular vein.
- Indication: Used when there is a need to reduce morbidity while still addressing lymphatic involvement.
3. Selective Neck Dissection
- Preservation of one or more lymph node groups that are typically removed in a radical neck dissection.
- Classification:
- Originally had named dissections (e.g., supraomohyoid neck dissection for levels I-III).
- The 2001 modification proposed naming dissections based on the cancer type and the specific node groups removed. For example, a selective neck dissection for oral cavity cancer might be referred to as a selective neck dissection (levels I-III).
- Indication: Used when there is a lower risk of lymphatic spread or when targeting specific areas.
4. Extended Neck Dissection
- Involves the removal of additional lymph
node groups or non-lymphatic structures beyond those included in a radical
neck dissection. This may include:
- Mediastinal nodes
- Non-lymphatic structures such as the carotid artery or hypoglossal nerve.
- Indication: Typically performed in cases of extensive disease or when there is a need to address additional areas of concern.
Management of Nasal Complex Fractures
Nasal complex fractures involve injuries to the nasal bones and surrounding structures, including the nasal septum, maxilla, and sometimes the orbits. Proper management is crucial to restore function and aesthetics.
Anesthesia Considerations
- Local Anesthesia:
- Nasal complex fractures can be reduced under local anesthesia, which may be sufficient for less complicated cases or when the patient is cooperative.
- General Anesthesia:
- For more complex fractures or when significant manipulation of the nasal structures is required, general anesthesia is preferred.
- Per-oral Endotracheal Tube: This method allows for better airway management and control during the procedure.
- Throat Pack: A throat pack is often used to minimize the risk of aspiration and to manage any potential hemorrhage, which can be profuse in these cases.
Surgical Technique
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Reduction of Fractures:
- The primary goal is to realign the fractured nasal bones and restore the normal anatomy of the nasal complex.
- Manipulation of Fragments:
- Walsham’s Forceps: These are specialized instruments used to grasp and manipulate the nasal bone fragments during reduction.
- Asche’s Forceps: Another type of forceps that can be used for similar purposes, allowing for precise control over the fractured segments.
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Post-Reduction Care:
- After the reduction, the nasal structures may be stabilized using splints or packing to maintain alignment during the healing process.
- Monitoring for complications such as bleeding, infection, or airway obstruction is essential.
Overview of Infective Endocarditis (IE):
- Infective endocarditis is an inflammation of the inner lining of the heart, often caused by bacterial infection.
- Certain cardiac conditions increase the risk of developing IE, particularly during dental procedures that may introduce bacteria into the bloodstream.
High-Risk Cardiac Conditions: Antibiotic prophylaxis is recommended for patients with the following high-risk cardiac conditions:
- Prosthetic cardiac valves
- History of infective endocarditis
- Cyanotic congenital heart disease
- Surgically constructed systemic-pulmonary shunts
- Other congenital heart defects
- Acquired valvular dysfunction
- Hypertrophic cardiomyopathy
- Mitral valve prolapse with regurgitation
Moderate-Risk Cardiac Conditions:
- Mitral valve prolapse without regurgitation
- Previous rheumatic fever with valvular dysfunction
Negligible Risk Conditions:
- Coronary bypass grafts
- Physiological or functional heart murmurs
Prophylaxis Recommendations
When to Administer Prophylaxis:
- Prophylaxis is indicated for dental procedures that involve:
- Manipulation of gingival tissue
- Perforation of the oral mucosa
- Procedures that may cause bleeding
Antibiotic Regimens:
- The standard prophylactic regimen is a single dose administered 30-60
minutes before the procedure:
- Amoxicillin:
- Adult dose: 2 g orally
- Pediatric dose: 50 mg/kg orally (maximum 2 g)
- Ampicillin:
- Adult dose: 2 g IV/IM
- Pediatric dose: 50 mg/kg IV/IM (maximum 2 g)
- Clindamycin (for penicillin-allergic patients):
- Adult dose: 600 mg orally
- Pediatric dose: 20 mg/kg orally (maximum 600 mg)
- Cephalexin (for penicillin-allergic patients):
- Adult dose: 2 g orally
- Pediatric dose: 50 mg/kg orally (maximum 2 g)
- Amoxicillin:
Marginal Resection
Marginal resection, also known as en bloc resection or peripheral osteotomy, is a surgical procedure used to treat locally aggressive benign lesions of the jaw. This technique involves the removal of the lesion along with a margin of surrounding bone, while preserving the continuity of the jaw.
Key Features of Marginal Resection
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Indications:
- Marginal resection is indicated for benign lesions with a known
propensity for recurrence, such as:
- Ameloblastoma
- Calcifying epithelial odontogenic tumor
- Myxoma
- Ameloblastic odontoma
- Squamous odontogenic tumor
- Benign chondroblastoma
- Hemangioma
- It is also indicated for recurrent lesions that have been previously treated with enucleation alone.
- Marginal resection is indicated for benign lesions with a known
propensity for recurrence, such as:
-
Rationale:
- Enucleation of locally aggressive lesions is not a safe procedure, as it can lead to recurrence. Marginal resection is a more effective approach, as it allows for the complete removal of the tumor along with a margin of surrounding bone.
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Benefits:
- Complete Removal of the Tumor: Marginal resection ensures the complete removal of the tumor, reducing the risk of recurrence.
- Preservation of Jaw Continuity: This procedure allows for the preservation of jaw continuity, avoiding deformity, disfigurement, and the need for secondary cosmetic surgery and prosthetic rehabilitation.
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Surgical Technique:
- The procedure involves the removal of the lesion along with a margin of surrounding bone. The extent of the resection is determined by the size and location of the lesion, as well as the patient's overall health and medical history.
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Postoperative Care:
- Patients may experience some discomfort and swelling following the procedure, which can be managed with analgesics and anti-inflammatory medications.
- Regular follow-up appointments are necessary to monitor the healing process and assess for any potential complications.
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Outcomes:
- Marginal resection is a highly effective procedure for treating locally aggressive benign lesions of the jaw. It allows for the complete removal of the tumor, while preserving jaw continuity and minimizing the risk of recurrence.
Hemostatic Agents
Hemostatic agents are critical in surgical procedures to control bleeding and promote wound healing. Various materials are used, each with unique properties and mechanisms of action. Below is a detailed overview of some commonly used hemostatic agents, including Gelfoam, Oxycel, Surgical (Oxycellulose), and Fibrin Glue.
1. Gelfoam
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Composition: Gelfoam is made from gelatin and has a sponge-like structure.
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Mechanism of Action:
- Gelfoam does not have intrinsic hemostatic properties; its hemostatic effect is primarily due to its large surface area, which comes into contact with blood.
- When Gelfoam absorbs blood, it swells and exerts pressure on the bleeding site, providing a scaffold for the formation of a fibrin network.
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Application:
- Gelfoam should be moistened in saline or thrombin solution before application to ensure optimal performance. It is essential to remove all air from the interstices to maximize its effectiveness.
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Absorption: Gelfoam is absorbed by the body through phagocytosis, typically within a few weeks.
2. Oxycel
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Composition: Oxycel is made from oxidized cellulose.
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Mechanism of Action:
- Upon application, Oxycel releases cellulosic acid, which has a strong affinity for hemoglobin, leading to the formation of an artificial clot.
- The acid produced during the wetting process can inactivate thrombin and other hemostatic agents, which is why Oxycel should be applied dry.
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Limitations:
- The acid produced can inhibit epithelialization, making Oxycel unsuitable for use over epithelial surfaces.
3. Surgical (Oxycellulose)
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Composition: Surgical is a glucose polymer-based sterile knitted fabric created through the controlled oxidation of regenerated cellulose.
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Mechanism of Action:
- The local hemostatic mechanism relies on the binding of hemoglobin to oxycellulose, allowing the dressing to expand into a gelatinous mass. This mass acts as a scaffold for clot formation and stabilization.
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Application:
- Surgical can be applied dry or soaked in thrombin solution, providing flexibility in its use.
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Absorption: It is removed by liquefaction and phagocytosis over a period of one week to one month. Unlike Oxycel, Surgical does not inhibit epithelialization and can be used over epithelial surfaces.
4. Fibrin Glue
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Composition: Fibrin glue is a biological adhesive that contains thrombin, fibrinogen, factor XIII, and aprotinin.
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Mechanism of Action:
- Thrombin converts fibrinogen into an unstable fibrin clot, while factor XIII stabilizes the clot. Aprotinin prevents the degradation of the clot.
- During wound healing, fibroblasts migrate through the fibrin meshwork, forming a more permanent framework composed of collagen fibers.
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Applications:
- Fibrin glue is used in various surgical procedures to promote hemostasis and facilitate tissue adhesion. It is particularly useful in areas where traditional sutures may be challenging to apply.
WAR Lines in the Assessment of Impacted Mandibular Third Molars
The WAR lines, as described by George Winter, are a set of three imaginary lines used in radiographic analysis to determine the position and depth of impacted mandibular third molars (wisdom teeth). These lines help clinicians assess the orientation and surgical approach needed for extraction. The three lines are color-coded: white, amber, and red, each serving a specific purpose in evaluating the impacted tooth.
1. White Line
- Description: The white line is drawn along the occlusal surfaces of the erupted mandibular molars and extended posteriorly over the third molar region.
- Purpose: This line helps visualize the axial inclination of the impacted third molar.
- Clinical Significance:
- If the occlusal surface of the vertically impacted third molar is parallel to the white line, it indicates that the tooth is positioned in a vertical orientation.
- Deviations from this line can suggest different angulations of impaction (e.g., mesioangular, distoangular).
2. Amber Line
- Description: The amber line is drawn from the surface of the bone on the distal aspect of the third molar to the crest of the interdental septum between the first and second mandibular molars.
- Purpose: This line represents the margin of the alveolar bone covering the third molar.
- Clinical Significance:
- The amber line indicates the amount of bone that will need to be removed to access the impacted tooth.
- After removing the soft tissue, only the portion of the impacted tooth structure that lies above the amber line will be visible, guiding the surgeon in determining the extent of bone removal required for extraction.
3. Red Line
- Description: The red line is an imaginary line drawn perpendicular to the amber line, extending to an imaginary point of application of the elevator, typically at the cementoenamel junction (CEJ) on the mesial surface of the impacted tooth.
- Exceptions: In cases of distoangular impaction, the point of application may be at the CEJ on the distal aspect of the tooth.
- Purpose: The length of the red line indicates the depth of the impacted tooth.
- Clinical Significance:
- This measurement helps the surgeon understand how deep the impacted tooth is positioned relative to the surrounding bone and soft tissue.
- It assists in planning the surgical approach and determining the necessary instruments for extraction.
Airway Management in Medical Emergencies: Tracheostomy and Cricothyrotomy
1. Establishing a Patent Airway
- Immediate Goal: The primary objective in any emergency involving airway obstruction is to ensure that the patient has a clear and patent airway to facilitate breathing.
- Procedures Available: Various techniques exist to achieve this, ranging from nonsurgical methods to surgical interventions.
2. Surgical Interventions
A. Tracheostomy
- A tracheostomy is a surgical procedure that involves creating an opening in the trachea (windpipe) through the neck to establish an airway.
- Indications:
- Prolonged mechanical ventilation.
- Severe upper airway obstruction (e.g., due to tumors, trauma, or swelling).
- Need for airway protection in patients with impaired consciousness or neuromuscular disorders.
- Procedure:
- An incision is made in the skin over the trachea, A tracheostomy incision is made between the second and third tracheal rings, which is below the larynx. The incision is usually 2–3 cm long and can be vertical or horizontaland the trachea is then opened to insert a tracheostomy tube.
- This procedure requires considerable knowledge of anatomy and technical skill to perform safely and effectively.
B. Cricothyrotomy
- Definition: A cricothyrotomy is a surgical procedure that involves making an incision through the skin over the cricothyroid membrane (located between the thyroid and cricoid cartilages) to establish an airway.
- Indications:
- Emergency situations where rapid access to the airway is required, especially when intubation is not possible.
- Situations where facial or neck trauma makes traditional intubation difficult.
- Procedure:
- A vertical incision is made over the cricothyroid membrane, and a tube is inserted directly into the trachea.
- This procedure is typically quicker and easier to perform than a tracheostomy, making it suitable for emergency situations.
3. Nonsurgical Techniques for Airway Management
A. Abdominal Thrust (Heimlich Maneuver)
- The Heimlich maneuver is a lifesaving technique used to relieve choking caused by a foreign body obstructing the airway.
- Technique:
- The rescuer stands behind the patient and wraps their arms around the patient's waist.
- A fist is placed just above the navel, and quick, inward and upward thrusts are applied to create pressure in the abdomen, which can help expel the foreign object.
- Indications: This technique is the first-line approach for conscious patients experiencing airway obstruction.
B. Back Blows and Chest Thrusts
- Back Blows:
- The rescuer delivers firm blows to the back between the shoulder blades using the heel of the hand. This can help dislodge an object obstructing the airway.
- Chest Thrusts:
- For patients who are obese or pregnant, chest thrusts may be more effective. The rescuer stands behind the patient and performs thrusts to the chest, similar to the Heimlich maneuver.