NEET MDS Lessons
Oral and Maxillofacial Surgery
Differences between Cellulitis and Abscess
1. Duration
- Cellulitis: Typically presents in the acute phase, meaning it develops quickly, often within hours to days. It can arise from a break in the skin, such as a cut or insect bite, leading to a rapid inflammatory response.
- Abscess: Often represents a chronic phase of infection. An abscess may develop over time as the body attempts to contain an infection, leading to the formation of a localized pocket of pus.
2. Pain
- Cellulitis: The pain is usually severe and generalized, affecting a larger area of the skin and subcutaneous tissue. Patients may describe a feeling of tightness or swelling in the affected area.
- Abscess: Pain is localized to the site of the abscess and is often more intense. The pain may be throbbing and can worsen with movement or pressure on the area.
3. Localization
- Cellulitis: The infection has diffuse borders, meaning it spreads through the tissue without a clear boundary. This can make it difficult to determine the exact extent of the infection.
- Abscess: The infection is well-circumscribed, meaning it has a defined boundary. The body forms a capsule around the abscess, which helps to contain the infection.
4. Palpation
- Cellulitis: On examination, the affected area may feel doughy or indurated (hardened) due to swelling and inflammation. There is no distinct fluctuation, as there is no localized collection of pus.
- Abscess: When palpated, an abscess feels fluctuant, indicating the presence of pus. This fluctuation is a key clinical sign that helps differentiate an abscess from cellulitis.
5. Bacteria
- Cellulitis: Primarily caused by aerobic bacteria, such as Streptococcus and Staphylococcus species. These bacteria thrive in the presence of oxygen and are commonly found on the skin.
- Abscess: Often caused by anaerobic bacteria or a mixed flora, which can include both aerobic and anaerobic organisms. Anaerobic bacteria thrive in low-oxygen environments, which is typical in the center of an abscess.
6. Size
- Cellulitis: Generally larger in area, as it involves a broader region of tissue. The swelling can extend beyond the initial site of infection.
- Abscess: Typically smaller and localized to the area of the abscess. The size can vary, but it is usually confined to a specific area.
7. Presence of Pus
- Cellulitis: No pus is present; the infection is diffuse and does not form a localized collection of pus. The inflammatory response leads to swelling and redness but not to pus formation.
- Abscess: Yes, pus is present; the abscess is characterized by a collection of pus within a cavity. The pus is a result of the body’s immune response to the infection.
8. Degree of Seriousness
- Cellulitis: Generally considered more serious due to the potential for systemic spread and complications if untreated. It can lead to sepsis, especially in immunocompromised individuals.
- Abscess: While abscesses can also be serious, they are often more contained. They can usually be treated effectively with drainage, and the localized nature of the infection can make management more straightforward.
Clinical Significance
- Diagnosis: Differentiating between cellulitis and abscess is crucial for appropriate treatment. Cellulitis may require systemic antibiotics, while an abscess often requires drainage.
- Management:
- Cellulitis: Treatment typically involves antibiotics and monitoring for systemic symptoms. In severe cases, hospitalization may be necessary.
- Abscess: Treatment usually involves incision and drainage (I&D) to remove the pus, along with antibiotics if there is a risk of systemic infection.
Punch Biopsy Technique
A punch biopsy is a medical procedure used to obtain a small cylindrical sample of tissue from a lesion for diagnostic purposes. This technique is particularly useful for mucosal lesions located in areas that are difficult to access with conventional biopsy methods. Below is an overview of the punch biopsy technique, its applications, advantages, and potential limitations.
Punch Biopsy
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Procedure:
- A punch biopsy involves the use of a specialized instrument called a punch (a circular blade) that is used to remove a small, cylindrical section of tissue from the lesion.
- The punch is typically available in various diameters (commonly ranging from 2 mm to 8 mm) depending on the size of the lesion and the amount of tissue needed for analysis.
- The procedure is usually performed under local anesthesia to minimize discomfort for the patient.
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Technique:
- Preparation: The area around the lesion is cleaned and sterilized.
- Anesthesia: Local anesthetic is administered to numb the area.
- Punching: The punch is pressed down onto the lesion, and a twisting motion is applied to cut through the skin or mucosa, obtaining a tissue sample.
- Specimen Collection: The cylindrical tissue sample is then removed, and any bleeding is controlled.
- Closure: The site may be closed with sutures or left to heal by secondary intention, depending on the size of the biopsy and the location.
Applications
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Mucosal Lesions: Punch biopsies are particularly useful for obtaining samples from mucosal lesions in areas such as:
- Oral cavity (e.g., lesions on the tongue, buccal mucosa, or gingiva)
- Nasal cavity
- Anus
- Other inaccessible regions where traditional biopsy methods may be challenging.
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Skin Lesions: While primarily used for mucosal lesions, punch biopsies can also be performed on skin lesions to diagnose conditions such as:
- Skin cancers (e.g., melanoma, basal cell carcinoma)
- Inflammatory skin diseases (e.g., psoriasis, eczema)
Advantages
- Minimal Invasiveness: The punch biopsy technique is relatively quick and minimally invasive, making it suitable for outpatient settings.
- Preservation of Tissue Architecture: The cylindrical nature of the sample helps preserve the tissue architecture, which is important for accurate histopathological evaluation.
- Accessibility: It allows for sampling from difficult-to-reach areas that may not be accessible with other biopsy techniques.
Limitations
- Tissue Distortion: As noted, the punch biopsy technique can produce some degree of crushing or distortion of the tissues. This may affect the histological evaluation, particularly in delicate or small lesions.
- Sample Size: The size of the specimen obtained may be insufficient for certain diagnostic tests, especially if a larger sample is required for comprehensive analysis.
- Potential for Scarring: Depending on the size of the punch and the location, there may be a risk of scarring or changes in the appearance of the tissue after healing.
Osteomyelitis of the Jaw (OML)
Osteomyelitis of the jaw (OML) is a serious infection of the bone that can lead to significant morbidity if not properly diagnosed and treated. Understanding the etiology and microbiological profile of OML is crucial for effective management. Here’s a detailed overview based on the information provided.
Historical Perspective on Etiology
- Traditional View: In the past, the etiology of OML was primarily associated with skin surface bacteria, particularly Staphylococcus aureus. Other bacteria, such as Staphylococcus epidermidis and hemolytic streptococci, were also implicated.
- Reevaluation: Recent findings indicate that S. aureus is not the primary pathogen in cases of OML affecting tooth-bearing bone. This shift in understanding highlights the complexity of the microbial landscape in jaw infections.
Microbiological Profile
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Common Pathogens:
- Aerobic Streptococci:
- α-Hemolytic Streptococci: Particularly Streptococcus viridans, which are part of the normal oral flora and can become pathogenic under certain conditions.
- Anaerobic Streptococci: These bacteria thrive in low-oxygen environments and are significant contributors to OML.
- Other Anaerobes:
- Peptostreptococcus: A genus of anaerobic bacteria commonly found in the oral cavity.
- Fusobacterium: Another group of anaerobic bacteria that can be involved in polymicrobial infections.
- Bacteroides: These bacteria are also part of the normal flora but can cause infections when the balance is disrupted.
- Aerobic Streptococci:
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Additional Organisms:
- Gram-Negative Organisms:
- Klebsiella, Pseudomonas, and Proteus species may also be isolated in some cases, particularly in chronic or complicated infections.
- Specific Pathogens:
- Mycobacterium tuberculosis: Can cause osteomyelitis in the jaw, particularly in immunocompromised individuals.
- Treponema pallidum: The causative agent of syphilis, which can lead to specific forms of osteomyelitis.
- Actinomyces species: Known for causing actinomycosis, these bacteria can also be involved in jaw infections.
- Gram-Negative Organisms:
Polymicrobial Nature of OML
- Polymicrobial Disease: Established acute OML is
typically a polymicrobial infection, meaning it involves multiple types of
bacteria. The common bacterial constituents include:
- Streptococci (both aerobic and anaerobic)
- Bacteroides
- Peptostreptococci
- Fusobacteria
- Other opportunistic bacteria that may contribute to the infection.
Clinical Implications
- Sinus Tract Cultures: Cultures obtained from sinus tracts in the jaw may often be misleading. They can be contaminated with skin flora, such as Staphylococcus species, which do not accurately represent the pathogens responsible for the underlying osteomyelitis.
- Diagnosis and Treatment: Understanding the polymicrobial nature of OML is essential for effective diagnosis and treatment. Empirical antibiotic therapy should consider the range of potential pathogens, and cultures should be interpreted with caution.
Intraligamentary Injection and Supraperiosteal Technique
Intraligamentary Injection
- The intraligamentary injection technique is a simple and effective method for achieving localized anesthesia in dental procedures. It requires only a small volume of anesthetic solution and produces rapid onset of anesthesia.
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Technique:
- Needle Placement:
- The needle is inserted into the gingival sulcus, typically on the mesial surface of the tooth.
- The needle is then advanced along the root surface until resistance is encountered, indicating that the needle is positioned within the periodontal ligament.
- Anesthetic Delivery:
- Approximately 0.2 ml of anesthetic solution is deposited into the periodontal ligament space.
- For multirooted teeth, injections should be made both mesially and distally to ensure adequate anesthesia of all roots.
- Needle Placement:
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Considerations:
- Significant pressure is required to express the anesthetic solution into the periodontal ligament, which can be a factor to consider during administration.
- This technique is particularly useful for localized procedures where rapid anesthesia is desired.
Supraperiosteal Technique (Local Infiltration)
- The supraperiosteal injection technique is commonly used for achieving anesthesia in the maxillary arch, particularly for single-rooted teeth.
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Technique:
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Anesthetic Injection:
- For the first primary molar, the bone overlying the tooth is thin, allowing for effective anesthesia by injecting the anesthetic solution opposite the apices of the roots.
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Challenges with Multirooted Teeth:
- The thick zygomatic process can complicate the anesthetic delivery for the buccal roots of the second primary molar and first permanent molars.
- Due to the increased thickness of bone in this area, the supraperiosteal injection at the apices of the roots of the second primary molar may be less effective.
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Supplemental Injection:
- To enhance anesthesia, a supplemental injection should be administered superior to the maxillary tuberosity area to block the posterior superior alveolar nerve.
- This additional injection compensates for the bone thickness and the presence of the posterior middle superior alveolar nerve plexus, which can affect the efficacy of the initial injection.
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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
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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.
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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.
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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.
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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
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Class 1:
- Description: Mesiodistal diameter of the crown is completely anterior to the anterior border of the mandibular ramus.
- Difficulty: Easiest to remove.
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Class 2:
- Description: Approximately one-half of the tooth is covered by the ramus.
- Difficulty: Moderate difficulty.
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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.
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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.
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Class B:
- Description: The occlusal surface lies between the occlusal plane and the cervical line of the second molar.
- Difficulty: Moderate difficulty.
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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
Mandibular Tori
Mandibular tori are bony growths that occur on the mandible, typically on the lingual aspect of the alveolar ridge. While they are often asymptomatic, there are specific indications for their removal, particularly when they interfere with oral function or prosthetic rehabilitation.
Indications for Removal
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Interference with Denture Construction:
- Mandibular tori may obstruct the proper fitting of full or partial dentures, necessitating their removal to ensure adequate retention and comfort.
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Ulceration and Slow Healing:
- If the mucosal covering over the torus ulcerates and the wound exhibits extremely slow healing, surgical intervention may be required to promote healing and prevent further complications.
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Interference with Speech and Deglutition:
- Large tori that impede normal speech or swallowing may warrant removal to improve the patient's quality of life and functional abilities.
Surgical Technique
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Incision Placement:
- The incision should be made on the crest of the ridge if the patient is edentulous (without teeth). This approach allows for better access to the torus while minimizing trauma to surrounding tissues.
- If there are teeth present in the area, the incision should be made along the gingival margin. This helps to preserve the integrity of the gingival tissue and maintain aesthetics.
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Avoiding Direct Incision Over the Torus:
- It is crucial not to make the incision directly over the torus.
Incising over the torus can lead to:
- Status Line: Leaving a visible line on the traumatized bone, which can affect aesthetics and function.
- Thin Mucosa: The mucosa over the torus is generally very thin, and an incision through it can result in dehiscence (wound separation) and exposure of the underlying bone, complicating healing.
- It is crucial not to make the incision directly over the torus.
Incising over the torus can lead to:
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Surgical Procedure:
- After making the appropriate incision, the mucosal flap is elevated to expose the underlying bone.
- The torus is then carefully removed using appropriate surgical instruments, ensuring minimal trauma to surrounding tissues.
- Hemostasis is achieved, and the mucosal flap is repositioned and sutured back into place.
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Postoperative Care:
- Patients may experience discomfort and swelling following the procedure, which can be managed with analgesics.
- Instructions for oral hygiene and dietary modifications may be provided to promote healing and prevent complications.
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Follow-Up:
- Regular follow-up appointments are necessary to monitor healing and assess for any potential complications, such as infection or delayed healing.
Classes of Hemorrhagic Shock (ATLS Classification)
Hemorrhagic shock is a critical condition resulting from significant blood loss, leading to inadequate tissue perfusion and oxygenation. The Advanced Trauma Life Support (ATLS) course classifies hemorrhagic shock into four classes based on various physiological parameters. Understanding these classes helps guide the management and treatment of patients experiencing hemorrhagic shock.
Class Descriptions
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Class I Hemorrhagic Shock:
- Blood Loss: 0-15% (up to 750 mL)
- CNS Status: Slightly anxious; the patient may be alert and oriented.
- Pulse: Heart rate <100 beats/min.
- Blood Pressure: Normal.
- Pulse Pressure: Normal.
- Respiratory Rate: 14-20 breaths/min.
- Urine Output: >30 mL/hr, indicating adequate renal perfusion.
- Fluid Resuscitation: Crystalloid fluids are typically sufficient.
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Class II Hemorrhagic Shock:
- Blood Loss: 15-30% (750-1500 mL)
- CNS Status: Mildly anxious; the patient may show signs of distress.
- Pulse: Heart rate >100 beats/min.
- Blood Pressure: Still normal, but compensatory mechanisms are activated.
- Pulse Pressure: Decreased due to increased heart rate and peripheral vasoconstriction.
- Respiratory Rate: 20-30 breaths/min.
- Urine Output: 20-30 mL/hr, indicating reduced renal perfusion.
- Fluid Resuscitation: Crystalloid fluids are still appropriate.
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Class III Hemorrhagic Shock:
- Blood Loss: 30-40% (1500-2000 mL)
- CNS Status: Anxious or confused; the patient may have altered mental status.
- Pulse: Heart rate >120 beats/min.
- Blood Pressure: Decreased; signs of hypotension may be present.
- Pulse Pressure: Decreased.
- Respiratory Rate: 30-40 breaths/min.
- Urine Output: 5-15 mL/hr, indicating significant renal impairment.
- Fluid Resuscitation: Crystalloid fluids plus blood products may be necessary.
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Class IV Hemorrhagic Shock:
- Blood Loss: >40% (>2000 mL)
- CNS Status: Confused or lethargic; the patient may be unresponsive.
- Pulse: Heart rate >140 beats/min.
- Blood Pressure: Decreased; severe hypotension is likely.
- Pulse Pressure: Decreased.
- Respiratory Rate: >35 breaths/min.
- Urine Output: Negligible, indicating severe renal failure.
- Fluid Resuscitation: Immediate crystalloid and blood products are critical.