NEET MDS Lessons
Oral and Maxillofacial Surgery
Seddon’s Classification of Nerve Injuries
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Neuropraxia:
- Definition: This is the mildest form of nerve injury, often caused by compression or mild trauma.
- Sunderland Classification: Type I (10).
- Nerve Sheath: Intact; the surrounding connective tissue remains undamaged.
- Axons: Intact; the nerve fibers are not severed.
- Wallerian Degeneration: None; there is no degeneration of the distal nerve segment.
- Conduction Failure: Transitory; there may be temporary loss of function, but it is reversible.
- Spontaneous Recovery: Complete recovery is expected.
- Time of Recovery: Typically within 4 weeks.
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Axonotmesis:
- Definition: This injury involves damage to the axons while the nerve sheath remains intact. It is often caused by more severe trauma, such as crush injuries.
- Sunderland Classification: Type II (20), Type III (30), Type IV (40).
- Nerve Sheath: Intact; the connective tissue framework is preserved.
- Axons: Interrupted; the nerve fibers are damaged but the sheath allows for potential regeneration.
- Wallerian Degeneration: Yes, partial; degeneration occurs in the distal segment of the nerve.
- Conduction Failure: Prolonged; there is a longer-lasting loss of function.
- Spontaneous Recovery: Partial recovery is possible, depending on the extent of the injury.
- Time of Recovery: Recovery may take months.
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Neurotmesis:
- Definition: This is the most severe type of nerve injury, where both the axons and the nerve sheath are disrupted. It often results from lacerations or severe trauma.
- Sunderland Classification: Type V (50).
- Nerve Sheath: Interrupted; the connective tissue is damaged, complicating regeneration.
- Axons: Interrupted; the nerve fibers are completely severed.
- Wallerian Degeneration: Yes, complete; degeneration occurs in both the proximal and distal segments of the nerve.
- Conduction Failure: Permanent; there is a lasting loss of function.
- Spontaneous Recovery: Poor to none; recovery is unlikely without surgical intervention.
- Time of Recovery: Recovery may begin by 3 months, if at all.
Treatment by Location
1. Within Parotid Gland
- Close parotid capsule
- Apply pressure dressing
2. Over Masseter
- Primary anastomosis
3. Anterior to Masseter
- Primary anastomosis if possible
- If impossible: Drain proximal duct directly into mouth via new opening
Sliding Osseous Genioplasty
Sliding osseous genioplasty is a surgical technique designed to enhance the projection of the chin, thereby improving facial aesthetics. This procedure is particularly advantageous for patients with retrogathia, where the chin is positioned further back than normal, and who typically present with Class I occlusion (normal bite relationship) without significant dentofacial deformities.
Indications for Sliding Osseous Genioplasty
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Aesthetic Chin Surgery:
- Most patients seeking this procedure do not have severe dentofacial deformities. They desire increased chin projection to achieve better facial balance and aesthetics.
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Retrogathia:
- Patients with a receding chin can significantly benefit from sliding osseous genioplasty, as it allows for the forward repositioning of the chin.
Procedure Overview
Sliding Osseous Genioplasty involves several key steps:
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Surgical Technique:
- Incision: The procedure can be performed through an intraoral incision (inside the mouth) or an extraoral incision (under the chin) to access the chin bone (mandibular symphysis).
- Bone Mobilization: A horizontal osteotomy (cut) is made in the chin bone to create a movable segment. This allows the surgeon to slide the bone segment forward to increase chin projection.
- Fixation: Once the desired position is achieved, the bone segment is secured in place using plates and screws or other fixation methods to maintain stability during the healing process.
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Versatility:
- Shorter and Longer Advancements: The technique can be tailored to achieve both shorter and longer advancements of the chin, depending on the patient's aesthetic goals.
- Vertical Height Alterations: Sliding osseous genioplasty is particularly effective for making vertical height adjustments to the chin, allowing for a customized approach to facial contouring.
Recovery
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Postoperative Care:
- Patients may experience swelling, bruising, and discomfort following the procedure. Pain relief medications are typically prescribed to manage discomfort.
- A soft diet is often recommended during the initial recovery phase to minimize strain on the surgical site.
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Follow-Up Appointments:
- Regular follow-up visits are necessary to monitor healing, assess the alignment of the chin, and ensure that there are no complications.
- The surgeon will evaluate the aesthetic outcome and make any necessary adjustments to the postoperative care plan.
Catgut Sutures
- Composition: Processed animal intestine (usually sheep)
- Degradation mechanism: Enzymatic degradation by tissue enzymes
- Types:
- Plain catgut: Resorbs in 7-10 days
- Chromic catgut: Cross-linked with chromium, resorbs in 2-3 weeks
- Advantages: Natural, good handling
- Disadvantages: Variable absorption, inflammatory response, potential allergic reactions
Vicryl (Polyglactin 910)
- Composition: Synthetic copolymer of glycolic and lactic acid
- Degradation mechanism: Hydrolysis (broken down by water)
- Absorption time: 2-3 weeks (loses tensile strength in 2-3 weeks, completely absorbed in 60-90 days)
- Variants:
- Vicryl: Standard braided suture
- Vicryl Rapide: Faster absorption (7-10 days)
- Vicryl Plus: Contains triclosan for antibacterial properties
- Advantages: Predictable absorption, minimal tissue reaction, good knot security
- Clinical uses: Soft tissue closure, periodontal surgery, buried sutures
Polydiaxone (PDS-II)
- Composition: Synthetic polymer (polydioxanone)
- Structure: Monofilament
- Degradation mechanism: Hydrolysis
- Absorption time: ~6 months with minimal tissue reaction
- Tensile strength: Retains 70% at 2 weeks, 50% at 4 weeks
- Advantages:
- Longest absorption time among synthetic absorbables
- Excellent biocompatibility
- Minimal inflammatory response
- Good for wounds requiring extended support
- Clinical uses: Deep tissue layers, slow-healing wounds, pediatric surgery
Other Synthetic Absorbable Sutures
Monocryl (Poliglecaprone 25)
- Absorption: 3-4 months
- Advantages: Low tissue reaction, good cosmetic results
- Uses: Subcuticular closure, soft tissue approximation
Biosyn (Glycomer 631)
- Absorption: 3-4 months
- Advantages: Braided with monofilament properties
- Uses: General soft tissue approximation
Nasogastric Tube (Ryles Tube)
A nasogastric tube (NG tube), commonly referred to as a Ryles tube, is a medical device used for various purposes, primarily involving the stomach. It is a long, hollow tube made of polyvinyl chloride (PVC) with one blunt end and multiple openings along its length. The tube is designed to be inserted through the nostril, down the esophagus, and into the stomach.
Description and Insertion
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Structure: The NG tube has a blunt end that is inserted into the nostril, and it features multiple openings to allow for the passage of fluids and air. The open end of the tube is used for feeding or drainage.
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Insertion Technique:
- The tube is gently passed through one of the nostrils and advanced through the nasopharynx and into the esophagus.
- Care is taken to ensure that the tube follows the natural curvature of the nasal passages and esophagus.
- Once the tube is in place, its position must be confirmed before any feeds or medications are administered.
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Position Confirmation:
- To check the position of the tube, air is pushed into the tube using a syringe.
- The presence of air in the stomach is confirmed by auscultation with a stethoscope, listening for the characteristic "whoosh" sound of air entering the stomach.
- Only after confirming that the tube is correctly positioned in the stomach should feeding or medication administration begin.
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Securing the Tube: The tube is fixed to the nose using sticking plaster or adhesive tape to prevent displacement.
Uses of Nasogastric Tube
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Nutritional Support:
- Enteral Feeding: The primary use of a nasogastric
tube is to provide nutritional support to patients who are unable to
take oral feeds due to various reasons, such as:
- Neurological conditions (e.g., stroke, coma)
- Surgical procedures affecting the gastrointestinal tract
- Severe dysphagia (difficulty swallowing)
- Enteral Feeding: The primary use of a nasogastric
tube is to provide nutritional support to patients who are unable to
take oral feeds due to various reasons, such as:
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Gastric Lavage:
- Postoperative Care: NG tubes can be used for gastric lavage to flush out blood, fluids, or other contents from the stomach after surgery. This is particularly important in cases where there is a risk of aspiration or when the stomach needs to be emptied.
- Poisoning: In cases of poisoning or overdose, gastric lavage may be performed using an NG tube to remove toxic substances from the stomach. This procedure should be done promptly and under medical supervision.
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Decompression:
- Relieving Distension: The NG tube can also be used to decompress the stomach in cases of bowel obstruction or ileus, allowing for the removal of excess gas and fluid.
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Medication Administration:
- The tube can be used to administer medications directly into the stomach for patients who cannot take oral medications.
Considerations and Complications
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Patient Comfort: Insertion of the NG tube can be uncomfortable for patients, and proper technique should be used to minimize discomfort.
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Complications: Potential complications include:
- Nasal and esophageal irritation or injury
- Misplacement of the tube into the lungs, leading to aspiration
- Sinusitis or nasal ulceration with prolonged use
- Gastrointestinal complications, such as gastric erosion or ulceration
Visor Osteotomy
Visor osteotomy is a surgical procedure primarily aimed at increasing the height of the mandibular ridge to enhance denture support. This technique is particularly beneficial for patients with resorbed or atrophic mandibles, where the lack of adequate bone height can compromise the retention and stability of dentures.
Goals of Visor Osteotomy
- Increase Mandibular Ridge Height: The primary objective is to augment the height of the mandibular ridge, providing a more favorable foundation for denture placement.
- Improve Denture Support: By increasing the ridge height, the procedure aims to enhance the retention and stability of dentures, leading to improved function and patient satisfaction.
Procedure Overview
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Incision and Exposure:
- A surgical incision is made in the oral mucosa to expose the mandible.
- The incision is typically placed along the vestibular area to minimize scarring and optimize healing.
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Central Splitting of the Mandible:
- The mandible is carefully split in the buccolingual dimension. This involves creating a central osteotomy that divides the mandible into two sections.
- The split allows for manipulation of the bone segments to achieve the desired height.
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Superior Positioning of the Lingual Section:
- The lingual section of the mandible is then repositioned superiorly. This elevation is crucial for increasing the height of the ridge.
- The repositioned segment is stabilized using wires or other fixation devices to maintain the new position during the healing process.
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Bone Grafting:
- Cancellous bone graft material is placed at the outer cortex over the superior labial junction. This grafting material helps to improve the contour of the mandible and provides additional support for the overlying soft tissues.
- The use of bone grafts can enhance the healing process and promote new bone formation in the area.
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Closure:
- The surgical site is closed in layers, ensuring that the mucosa and underlying tissues are properly approximated.
- Postoperative care instructions are provided to the patient to facilitate healing and minimize complications.
Indications
- Atrophic Mandible: Patients with significant bone resorption in the mandible, often seen in edentulous individuals, are prime candidates for this procedure.
- Denture Retention Issues: Individuals experiencing difficulties with denture retention and stability due to inadequate ridge height may benefit from visor osteotomy.
Benefits
- Enhanced Denture Support: By increasing the height of the mandibular ridge, patients can achieve better retention and stability of their dentures.
- Improved Aesthetics: The procedure can also enhance the facial contour, contributing to improved aesthetics for the patient.
- Functional Improvement: Patients may experience improved chewing function and overall quality of life following the procedure.
Considerations and Risks
- Surgical Risks: As with any surgical procedure, there are risks involved, including infection, bleeding, and complications related to anesthesia.
- Healing Time: Patients should be informed about the expected healing time and the importance of following postoperative care instructions.
- Follow-Up: Regular follow-up appointments are necessary to monitor healing and assess the need for any adjustments to dentures.
Hockey Stick or London Hospital Elevator
The Hockey Stick Elevator, also known as the London Hospital Elevator, is a dental instrument used primarily in oral surgery and tooth extraction procedures. It is designed to facilitate the removal of tooth roots and other dental structures.
Design and Features
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Blade Shape: The Hockey Stick Elevator features a straight blade that is angled relative to the shank, similar to the Cryer’s elevator. However, unlike the Cryer’s elevator, which has a triangular blade, the Hockey Stick Elevator has a straight blade with a convex surface on one side and a flat surface on the other.
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Working Surface:
- The flat surface of the blade is the working surface and is equipped with transverse serrations. These serrations enhance the instrument's grip and contact with the root stump, allowing for more effective leverage during extraction.
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Appearance: The instrument resembles a hockey stick, which is how it derives its name. The distinctive shape aids in its identification and use in clinical settings.
Principles of Operation
- Lever and Wedge Principle:
- The Hockey Stick Elevator operates on the same principles as the Cryer’s elevator, utilizing the lever and wedge principle. This means that the instrument can be used to apply force to the tooth or root, effectively loosening it from the surrounding bone and periodontal ligament.
- Functionality:
- The primary function of the Hockey Stick Elevator is to elevate and luxate teeth or root fragments during extraction procedures. It can be particularly useful in cases where the tooth is impacted or has a curved root.