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:

1. Simple Non-Compression Bone Plates:

   • These plates provide stability without applying compressive forces across the fracture site.

2. Mini Bone Plates:

   • Smaller plates designed for use in areas where space is limited, providing adequate stabilization for smaller fractures.

3. Compression Plates:

   • These plates apply compressive forces across the fracture site, promoting bone healing by encouraging contact between the fracture fragments.

4. 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:

1. 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.

2. Reduction:

   • The fracture must be reduced independently, ensuring that the teeth are in occlusion before securing the wire.

3. 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.

4. 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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• Jones I & II tests: Assess nasolacrimal duct patency.
  • Jones I: Inject fluorescein dye into conjunctival sac; check nasal emergence.
  • Jones II: Locate obstruction if dye not retrieved.
• Dacryocystorhinostomy (DCR): Bypasses nasolacrimal duct; lacrimal sac anastomosed with nasal mucosa.
• Lund & Browder chart: Most accurate for burn surface area assessment (adjusts for age).
• Allan test: Checks collateral circulation via ulnar artery.
• Ice water caloric testing: SCOW (Same Cold, Opposite Warm) → eye movement toward ipsilateral ear with intact sensory system.

Classification and Management of Impacted Third Molars

Impacted third molars, commonly known as wisdom teeth, can present in various orientations and depths, influencing the difficulty of their extraction. Understanding the types of impactions and their classifications is crucial for planning surgical intervention.

Types of Impaction

1. Mesioangular Impaction:

   • Description: The tooth is tilted toward the second molar in a mesial direction.
   • Prevalence: Comprises approximately 43% of all impacted teeth.
   • Difficulty: Generally acknowledged as the least difficult type of impaction to remove.

2. Vertical Impaction:

   • Description: The tooth is positioned vertically, with the crown facing upward.
   • Prevalence: Accounts for about 38% of impacted teeth.
   • Difficulty: Moderate difficulty in removal.

3. Distoangular Impaction:

   • Description: The tooth is tilted away from the second molar in a distal direction.
   • Prevalence: Comprises approximately 6% of impacted teeth.
   • Difficulty: Considered the most difficult type of impaction to remove due to the withdrawal pathway running into the mandibular ramus.

4. Horizontal Impaction:

   • Description: The tooth is positioned horizontally, with the crown facing the buccal or lingual side.
   • Prevalence: Accounts for about 3% of impacted teeth.
   • Difficulty: More difficult than mesioangular but less difficult than distoangular.

Decreasing Level of Difficulty for Types of Impaction

• Order of Difficulty:
  • Distoangular > Horizontal > Vertical > Mesioangular

Pell and Gregory Classification

The Pell and Gregory classification system categorizes impacted teeth based on their relationship to the mandibular ramus and the occlusal plane. This classification helps assess the difficulty of extraction.

Classification Based on Coverage by the Mandibular Ramus

1. Class 1:

   • Description: Mesiodistal diameter of the crown is completely anterior to the anterior border of the mandibular ramus.
   • Difficulty: Easiest to remove.

2. Class 2:

   • Description: Approximately one-half of the tooth is covered by the ramus.
   • Difficulty: Moderate difficulty.

3. Class 3:

   • Description: The tooth is completely within the mandibular ramus.
   • Difficulty: Most difficult to remove.

Decreasing Level of Difficulty for Ramus Coverage

• Order of Difficulty:
  • Class 3 > Class 2 > Class 1

Pell and Gregory Classification Based on Relationship to Occlusal Plane

This classification assesses the depth of the impacted tooth relative to the occlusal plane of the second molar.

1. Class A:

   • Description: The occlusal surface of the impacted tooth is level or nearly level with the occlusal plane of the second molar.
   • Difficulty: Easiest to remove.

2. Class B:

   • Description: The occlusal surface lies between the occlusal plane and the cervical line of the second molar.
   • Difficulty: Moderate difficulty.

3. Class C:

   • Description: The occlusal surface is below the cervical line of the second molars.
   • Difficulty: Most difficult to remove.

Decreasing Level of Difficulty for Occlusal Plane Relationship

• Order of Difficulty:
  • Class C > Class B > Class A

Summary of Extraction Difficulty

• Most Difficult Impaction:
  • Distoangular impaction with Class 3 ramus coverage and Class C depth.
• Easiest Impaction:
  • Mesioangular impaction with Class 1 ramus coverage and Class A dep

Piezosurgery

Piezosurgery is an advanced surgical technique that utilizes ultrasonic vibrations to cut bone and other hard tissues with precision. This method has gained popularity in oral and maxillofacial surgery due to its ability to minimize trauma to surrounding soft tissues, enhance surgical accuracy, and improve patient outcomes. Below is a detailed overview of the principles, advantages, applications, and specific uses of piezosurgery in oral surgery.

Principles of Piezosurgery

• Ultrasonic Technology: Piezosurgery employs ultrasonic waves to create high-frequency vibrations in specially designed surgical tips. These vibrations allow for precise cutting of bone while preserving adjacent soft tissues.
• Selective Cutting: The ultrasonic frequency is tuned to selectively cut mineralized tissues (like bone) without affecting softer tissues (like nerves and blood vessels). This selectivity reduces the risk of complications and enhances healing.

Advantages of Piezosurgery

1. Strength and Durability of Tips:

   • Piezosurgery tips are made from high-quality materials that are strong and resistant to fracture. This durability allows for extended use without the need for frequent replacements, making them cost-effective in the long run.

2. Access to Difficult Areas:

   • The design of piezosurgery tips allows them to reach challenging anatomical areas that may be difficult to access with traditional surgical instruments. This is particularly beneficial in complex procedures involving the mandible and maxilla.

3. Minimized Trauma:

   • The ultrasonic cutting action produces less heat and vibration compared to traditional rotary instruments, which helps to preserve the integrity of surrounding soft tissues and reduces postoperative pain and swelling.

4. Enhanced Precision:

   • The ability to perform precise cuts allows for better control during surgical procedures, leading to improved outcomes and reduced complications.

5. Reduced Blood Loss:

   • The selective cutting action minimizes damage to blood vessels, resulting in less bleeding during surgery.

Applications in Oral Surgery

Piezosurgery has a variety of applications in oral and maxillofacial surgery, including:

1. Osteotomies:

   • LeFort I Osteotomy: Piezosurgery is particularly useful in performing pterygoid disjunction during LeFort I osteotomy. The ability to precisely cut bone in the pterygoid region allows for better access and alignment during maxillary repositioning.
   • Intraoral Vertical Ramus Osteotomy (IVRO): The lower border cut at the lateral surface of the ramus can be performed with piezosurgery, allowing for precise osteotomy while minimizing trauma to surrounding structures.
   • Inferior Alveolar Nerve Lateralization: Piezosurgery can be used to carefully lateralize the inferior alveolar nerve during procedures such as bone grafting or implant placement, reducing the risk of nerve injury.

2. Bone Grafting:

   • Piezosurgery is effective in harvesting bone grafts from donor sites, as it allows for precise cuts and minimal damage to surrounding tissues. This is particularly important in procedures requiring autogenous bone grafts.

3. Implant Placement:

   • The technique can be used to prepare the bone for dental implants, allowing for precise osteotomy and reducing the risk of complications associated with traditional drilling methods.

4. Sinus Lift Procedures:

   • Piezosurgery is beneficial in sinus lift procedures, where precise bone cutting is required to elevate the sinus membrane without damaging it.

5. Tumor Resection:

   • The precision of piezosurgery makes it suitable for resecting tumors in the jaw while preserving surrounding healthy tissue.

Structure of Orbital Walls

The orbit is a complex bony structure that houses the eye and its associated structures. It is composed of several walls, each with distinct anatomical features and clinical significance. Here’s a detailed overview of the structure of the orbital walls:

1. Lateral Wall

• Composition: The lateral wall of the orbit is primarily formed by two bones:
  • Zygomatic Bone: This bone contributes significantly to the lateral aspect of the orbit.
  • Greater Wing of the Sphenoid: This bone provides strength and stability to the lateral wall.
• Orientation: The lateral wall is inclined at approximately 45 degrees to the long axis of the skull, which is important for the positioning of the eye and the alignment of the visual axis.

2. Medial Wall

• Composition: The medial wall is markedly different from the lateral wall and is primarily formed by:
  • Orbital Plate of the Ethmoid Bone: This plate is very thin and fragile, making the medial wall susceptible to injury.
• Height and Orientation: The medial wall is about half the height of the lateral wall. It is aligned parallel to the antero-posterior axis (median plane) of the skull and meets the floor of the orbit at an angle of about 45 degrees.
• Fragility: The medial wall is extremely fragile due to its proximity to:
  • Ethmoid Air Cells: These air-filled spaces can compromise the integrity of the medial wall.
  • Nasal Cavity: The close relationship with the nasal cavity further increases the risk of injury.

3. Roof of the Orbit

• Composition: The roof is formed by the frontal bone and is reinforced laterally by the greater wing of the sphenoid.
• Thickness: While the roof is thin, it is structurally reinforced, which helps protect the contents of the orbit.
• Fracture Patterns: Fractures of the roof often involve the frontal bone and tend to extend medially. Such fractures can lead to complications, including orbital hemorrhage or involvement of the frontal sinus.

4. Floor of the Orbit

• Composition: The floor is primarily formed by the maxilla, with contributions from the zygomatic and palatine bones.
• Thickness: The floor is very thin, typically measuring about 0.5 mm in thickness, making it particularly vulnerable to fractures.
• Clinical Significance:
  • Blow-Out Fractures: The floor is commonly involved in "blow-out" fractures, which occur when a blunt force impacts the eye, causing the floor to fracture and displace. These fractures can be classified as:
    • Pure Blow-Out Fractures: Isolated fractures of the orbital floor.
    • Impure Blow-Out Fractures: Associated with fractures in the zygomatic area.
  • Infraorbital Groove and Canal: The presence of the infraorbital groove and canal further weakens the floor. The infraorbital nerve and vessels run through this canal, making them susceptible to injury during fractures. Compression, contusion, or direct penetration from bone spicules can lead to sensory deficits in the distribution of the infraorbital nerve.

• Trismus case extraction: Use Vazirani – Akinosi closed mouth mandibular nerve block
• Pregnancy – safe anesthetics: Category B (Lignocaine, Prilocaine, Etidocaine)
• Common allergen in LA: Methylparaben (preservative in multi – dose vials)
• MI patient on aspirin: Do not stop aspirin for extraction
• Steroid patient (RA): Double steroid dose before surgery
• AV malformation: Pre – op embolization, extract after 48 – 72 hrs
• Safe adrenaline dose (cardiac patient): 0.04 mg
• Max dose of 2% lignocaine with 1:200,000 adrenaline (60 kg adult): 21 mL
• Local anesthetic mechanism: Blocks inactivated Na⁺ channels
• Unionized form (RNH⁺): Enters nerve terminal
• Ionized form (RN⁺H₃): Active inside cell
• Metabolism of amide LA: Liver via P – 450 enzymes
• LA half – lives: Lidocaine – 90 min, Bupivacaine – 200 min, Articaine – 20 – 40 min
• Least toxic LA: Chloroprocaine
• Antioxidant for vasoconstrictor in LA: Sodium bisulfite/metabisulfite
• Noradrenaline not used with lignocaine: Causes intense vasoconstriction