NEET MDS Lessons
Oral and Maxillofacial Surgery
Basic Principles of Treatment of a Fracture
The treatment of fractures involves a systematic approach to restore the normal anatomy and function of the affected bone. The basic principles of fracture treatment can be summarized in three key steps: reduction, fixation, and immobilization.
1. Reduction
Definition: Reduction is the process of restoring the fractured bone fragments to their original anatomical position.
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Methods of Reduction:
- Closed Reduction: This technique involves
realigning the bone fragments without direct visualization of the
fracture line. It can be achieved through:
- Reduction by Manipulation: The physician uses manual techniques to manipulate the bone fragments into alignment.
- Reduction by Traction: Gentle pulling forces are applied to align the fragments, often used in conjunction with other methods.
- Closed Reduction: This technique involves
realigning the bone fragments without direct visualization of the
fracture line. It can be achieved through:
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Open Reduction: In some cases, if closed reduction is not successful or if the fracture is complex, an open reduction may be necessary. This involves surgical exposure of the fracture site to directly visualize and align the fragments.
2. Fixation
Definition: After reduction, fixation is the process of stabilizing the fractured fragments in their normal anatomical relationship to prevent displacement and ensure proper healing.
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Types of Fixation:
- Internal Fixation: This involves the use of devices such as plates, screws, or intramedullary nails that are placed inside the body to stabilize the fracture.
- External Fixation: This method uses external devices, such as pins or frames, that are attached to the bone through the skin. External fixation is often used in cases of open fractures or when internal fixation is not feasible.
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Goals of Fixation: The primary goals are to maintain the alignment of the bone fragments, prevent movement at the fracture site, and facilitate healing.
3. Immobilization
Definition: Immobilization is the phase during which the fixation device is retained to stabilize the reduced fragments until clinical bony union occurs.
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Duration of Immobilization: The length of the immobilization period varies depending on the type of fracture and the bone involved:
- Maxillary Fractures: Typically require 3 to 4 weeks of immobilization.
- Mandibular Fractures: Generally require 4 to 6 weeks of immobilization.
- Condylar Fractures: Recommended immobilization period is 2 to 3 weeks to prevent temporomandibular joint (TMJ) ankylosis.
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Frenectomy- Overview and Techniques
A frenectomy is a surgical procedure that involves the removal of a frenum, which is a thin band of fibrous tissue that connects the lip or tongue to the underlying alveolar mucosa. This procedure is often performed to address issues related to abnormal frenal attachments that can cause functional or aesthetic problems.
Key Features of Frenal Attachment
- A frenum consists of a thin band of fibrous tissue and a few muscle fibers, covered by mucous membrane. It serves to anchor the lip or tongue to the underlying structures.
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Common Locations:
- Maxillary Midline Frenum: The most commonly encountered frenum, located between the central incisors in the upper jaw.
- Lingual Frenum: Found under the tongue; its attachment can vary in length and thickness among individuals.
- Maxillary and Mandibular Frena: These can also be present in the premolar and molar areas, potentially affecting oral function and hygiene.
Indications for Frenectomy
- Functional Issues: An overly tight or thick frenum can restrict movement of the lip or tongue, leading to difficulties in speech, eating, or oral hygiene.
- Aesthetic Concerns: Prominent frena can cause spacing issues between teeth or affect the appearance of the smile.
- Orthodontic Considerations: In some cases, frenectomy may be performed prior to orthodontic treatment to facilitate tooth movement and prevent relapse.
Surgical Techniques
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Z-Plasty Procedure:
- Indication: Used when the frenum is broad and the vestibule (the space between the lip and the gums) is short.
- Technique: This method involves creating a Z-shaped incision that allows for the repositioning of the tissue, effectively lengthening the vestibule and improving the functional outcome.
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V-Y Incision:
- Indication: Employed for lengthening a localized area, particularly when the frenum is causing tension or restriction.
- Technique: A V-shaped incision is made, and the tissue is then sutured in a Y configuration, which helps to lengthen the frenum and improve mobility.
Postoperative Care
- Pain Management: Patients may experience discomfort following the procedure, which can be managed with analgesics.
- Oral Hygiene: Maintaining good oral hygiene is crucial to prevent infection at the surgical site.
Microvascular Trigeminal Decompression (The Jannetta Procedure)
Microvascular decompression (MVD), commonly known as the Jannetta procedure, is a surgical intervention designed to relieve the symptoms of classic trigeminal neuralgia by addressing the underlying vascular compression of the trigeminal nerve. This procedure is particularly effective for patients who have not responded to medical management or who experience significant side effects from medications.
Overview of the Procedure
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Indication:
- MVD is indicated for patients with classic trigeminal neuralgia, characterized by recurrent episodes of severe facial pain, often triggered by light touch or specific activities.
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Anesthesia:
- The procedure is performed under general anesthesia to ensure the patient is completely unconscious and pain-free during the surgery.
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Surgical Approach:
- The surgery is conducted using an intraoperative microscope for enhanced visualization of the delicate structures involved.
- The arachnoid membrane surrounding the trigeminal nerve is carefully opened to access the nerve.
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Exploration:
- The trigeminal nerve is explored from its entry point at the brainstem to the entrance of Meckel’s cave, where the trigeminal ganglion (Gasserian ganglion) is located.
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Microdissection:
- Under microscopic and endoscopic visualization, the surgeon performs microdissection to identify and mobilize any arteries or veins that are compressing the trigeminal nerve.
- The most common offending vessel is a branch of the superior cerebellar artery, but venous compression or a combination of arterial and venous compression may also be present.
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Decompression:
- Once the offending vessels are identified, they are decompressed.
This may involve:
- Cauterization and division of veins that are compressing the nerve.
- Placement of Teflon sponges between the dissected blood vessels and the trigeminal nerve to prevent further vascular compression.
- Once the offending vessels are identified, they are decompressed.
This may involve:
Outcomes and Efficacy
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Immediate Pain Relief:
- Most patients experience immediate relief from facial pain following the decompression of the offending vessels.
- Reports indicate rates of immediate pain relief as high as 90% to 98% after the procedure.
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Long-Term Relief:
- Many patients enjoy long-term relief from trigeminal neuralgia symptoms, although some may experience recurrence of pain over time.
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Complications:
- As with any surgical procedure, there are potential risks and complications, including infection, cerebrospinal fluid leaks, and neurological deficits. However, MVD is generally considered safe and effective.
Rigid Fixation
Rigid fixation is a surgical technique used to stabilize fractured bones.
Types of Rigid Fixation
Rigid fixation can be achieved using various types of plates and devices, including:
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Simple Non-Compression Bone Plates:
- These plates provide stability without applying compressive forces across the fracture site.
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Mini Bone Plates:
- Smaller plates designed for use in areas where space is limited, providing adequate stabilization for smaller fractures.
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Compression Plates:
- These plates apply compressive forces across the fracture site, promoting bone healing by encouraging contact between the fracture fragments.
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Reconstruction Plates:
- Used for complex fractures or reconstructions, these plates can be contoured to fit the specific anatomy of the fractured bone.
Transosseous Wiring (Intraosseous Wiring)
Transosseous wiring is a traditional and effective method for the fixation of jaw bone fractures. It involves the following steps:
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Technique:
- Holes are drilled in the bony fragments on either side of the fracture line.
- A length of 26-gauge stainless steel wire is passed through the holes and across the fracture.
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Reduction:
- The fracture must be reduced independently, ensuring that the teeth are in occlusion before securing the wire.
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Twisting the Wire:
- After achieving proper alignment, the free ends of the wire are twisted to secure the fracture.
- The twisted ends are cut short and tucked into the nearest drill hole to prevent irritation to surrounding tissues.
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Variations:
- The single strand wire fixation in a horizontal manner is the simplest form of intraosseous wiring, but it can be modified in various ways depending on the specific needs of the fracture and the patient.
Other fixation techniques
Open reduction and internal fixation (ORIF):
Surgical exposure of the fracture site, followed by reduction and fixation with
plates, screws, or nails
Closed reduction and immobilization (CRII):
Manipulation of the bone fragments into alignment without surgical exposure,
followed by cast or splint immobilization
Intramedullary nailing:
Insertion of a metal rod (nail) into the medullary canal of the bone to
stabilize long bone fractures
External fixation:
A device with pins inserted through the bone fragments and connected to an
external frame to provide stability
Tension band wiring:
A technique using wires to apply tension across a fracture site, particularly
useful for avulsion fractures
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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.
Ridge Augmentation Procedures
Ridge augmentation procedures are surgical techniques used to increase the volume and density of the alveolar ridge in the maxilla and mandible. These procedures are often necessary to prepare the site for dental implants, especially in cases where there has been significant bone loss due to factors such as tooth extraction, periodontal disease, or trauma. Ridge augmentation can also be performed in conjunction with orthognathic surgery to enhance the overall facial structure and support dental rehabilitation.
Indications for Ridge Augmentation
- Insufficient Bone Volume: To provide adequate support for dental implants.
- Bone Resorption: Following tooth extraction or due to periodontal disease.
- Facial Aesthetics: To improve the contour of the jaw and facial profile.
- Orthognathic Surgery: To enhance the results of jaw repositioning procedures.
Types of Graft Materials Used
Ridge augmentation can be performed using various graft materials, which can be classified into the following categories:
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Autografts:
- Bone harvested from the patient’s own body, typically from intraoral sites (e.g., chin, ramus) or extraoral sites (e.g., iliac crest).
- Advantages: High biocompatibility, osteogenic potential, and lower risk of rejection or infection.
- Disadvantages: Additional surgical site, potential for increased morbidity, and limited availability.
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Allografts:
- Bone grafts obtained from a human donor (cadaveric bone) that have been processed and sterilized.
- Advantages: No additional surgical site required, readily available, and can provide a scaffold for new bone growth.
- Disadvantages: Risk of disease transmission and potential for immune response.
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Xenografts:
- Bone grafts derived from a different species, commonly bovine (cow) bone.
- Advantages: Biocompatible and provides a scaffold for bone regeneration.
- Disadvantages: Potential for immune response and slower resorption compared to autografts.
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Alloplasts:
- Synthetic materials used for bone augmentation, such as hydroxyapatite, calcium phosphate, or bioactive glass.
- Advantages: No risk of disease transmission, customizable, and can be designed to promote bone growth.
- Disadvantages: May not integrate as well as natural bone and can have variable resorption rates.
Surgical Techniques
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Bone Grafting:
- The selected graft material is placed in the deficient area of the
ridge to promote new bone formation. This can be done using various
techniques, including:
- Onlay Grafting: Graft material is placed on top of the existing ridge.
- Inlay Grafting: Graft material is placed within the ridge.
- The selected graft material is placed in the deficient area of the
ridge to promote new bone formation. This can be done using various
techniques, including:
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Guided Bone Regeneration (GBR):
- A barrier membrane is placed over the graft material to prevent soft tissue infiltration and promote bone healing. This technique is often used in conjunction with grafting.
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Sinus Lift:
- In the maxilla, a sinus lift procedure may be performed to augment the bone in the posterior maxilla by elevating the sinus membrane and placing graft material.
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Combination with Orthognathic Surgery:
- Ridge augmentation can be performed simultaneously with orthognathic surgery to correct skeletal discrepancies and enhance the overall facial structure.
Radiological Signs Indicating Relationship Between Mandibular Third Molars and the Inferior Alveolar Canal
In 1960, Howe and Payton identified seven radiological signs that suggest a close relationship between the mandibular third molar (wisdom tooth) and the inferior alveolar canal (IAC). Recognizing these signs is crucial for dental practitioners, especially when planning for the extraction of impacted third molars, as they can indicate potential complications such as nerve injury. Below are the seven signs explained in detail:
1. Darkening of the Root
- This sign appears as a radiolucent area at the root of the mandibular third molar, indicating that the root is in close proximity to the IAC.
- Clinical Significance: Darkening suggests that the root may be in contact with or resorbing against the canal, which can increase the risk of nerve damage during extraction.
2. Deflected Root
- This sign is characterized by a deviation or angulation of the root of the mandibular third molar.
- Clinical Significance: A deflected root may indicate that the tooth is pushing against the IAC, suggesting a close anatomical relationship that could complicate surgical extraction.
3. Narrowing of the Root
- This sign is observed as a reduction in the width of the root, often seen on radiographs.
- Clinical Significance: Narrowing may indicate that the root is being resorbed or is in close contact with the IAC, which can pose a risk during extraction.
4. Interruption of the White Line(s)
- The white line refers to the radiopaque outline of the IAC. An interruption in this line can be seen on radiographs.
- Clinical Significance: This interruption suggests that the canal may be displaced or affected by the root of the third molar, indicating a potential risk for nerve injury.
5. Diversion of the Inferior Alveolar Canal
- This sign is characterized by a noticeable change in the path of the IAC, which may appear to be deflected or diverted around the root of the third molar.
- Clinical Significance: Diversion of the canal indicates that the root is in close proximity to the IAC, which can complicate surgical procedures and increase the risk of nerve damage.
6. Narrowing of the Inferior Alveolar Canal (IAC)
- This sign appears as a reduction in the width of the IAC on radiographs.
- Clinical Significance: Narrowing of the canal may suggest that the root of the third molar is encroaching upon the canal, indicating a close relationship that could lead to complications during extraction.
7. Hourglass Form
- This sign indicates a partial or complete encirclement of the IAC by the root of the mandibular third molar, resembling an hourglass shape on radiographs.
- Clinical Significance: An hourglass form suggests that the root may be significantly impinging on the IAC, which poses a high risk for nerve injury during extraction.