NEET MDS Synopsis
Seddon’s Classification of Nerve Injuries
Oral and Maxillofacial SurgerySeddon’s Classification of Nerve Injuries
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.
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.
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.
Periodontal Medicaments
Periodontology
Periodontal Medicaments
Periodontal diseases often require adjunctive therapies to traditional
mechanical treatments such as scaling and root planing. Various medicaments have
been developed to enhance the healing process and control infection in
periodontal tissues. This lecture will discuss several periodontal medicaments,
their compositions, and their clinical applications.
1. Elyzol
Composition:
Elyzol is an oil-based gel containing 25% metronidazole.
It is formulated with glyceryl mono-oleate and sesame oil.
Clinical Use:
Elyzol has been found to be equivalent to scaling and root
planing in terms of effectiveness for treating periodontal
disease.
However, no adjunctive effects beyond those achieved with mechanical
debridement have been demonstrated.
2. Actisite
Composition:
Actisite consists of tetracycline-containing fibers.
Each fiber has a diameter of 0.5 mm and contains 12.7
mg of tetracycline per 9 inches of fiber.
Clinical Use:
The fibers are placed directly into periodontal pockets, where they
release tetracycline over time, helping to reduce bacterial load and
promote healing.
3. Arestin
Composition:
Arestin contains minocycline, which is delivered as
a biodegradable powder in a syringe.
Clinical Use:
Arestin is indicated for the treatment of periodontal disease and is
applied directly into periodontal pockets, where it provides localized
antibiotic therapy.
4. Atridox
Composition:
Atridox contains 10% doxycycline in a syringeable
gel system that is biodegradable.
Clinical Use:
The gel is injected into periodontal pockets, where it solidifies
and releases doxycycline over time, aiding in the management of
periodontal disease.
5. Dentamycin and Periocline
Composition:
Both Dentamycin and Periocline contain 2% minocycline
hydrochloride.
Clinical Use:
These products are used similarly to other local delivery systems,
providing localized antibiotic therapy to reduce bacterial infection in
periodontal pockets.
6. Periochip
Composition:
Periochip is a biodegradable chip that contains chlorhexidine.
Clinical Use:
The chip is placed in the gingival crevice, where it releases
chlorhexidine over time, providing antimicrobial action and helping to
control periodontal disease.
The Skeleton of the Nose
AnatomyThe Skeleton of the Nose
The immovable bridge of the nose, the superior bony part of the nose, consists of the nasal bones, the frontal processes of the maxillae, and the nasal part of the frontal bones.
The movable cartilaginous part consists of five main cartilages and a few smaller ones.
The U-shaped alar nasal cartilages are free and movable.
They dilate and constrict the external nares when the muscles acting on the external nose contract.
The Nasal Cavities
The nasal cavities are entered through the anterior nares or nostrils.
They open into the nasopharynx through the choanae.
The Roof and Floor of the Nasal Cavity
The roof is curved and narrow, except at the posterior end.
The floor is wider than the roof.
It is formed from the palatine process of the maxilla and the horizontal plate of the palatine bone.
The Walls of the Nasal Cavity
The medial wall is formed by the nasal septum; it is usually smooth.
The lateral wall is uneven owing to the three longitudinal, scroll-shaped elevations, called the conchae (L. shells) or turbinates (L. shaped like a top).
These elevations are called the superior, middle and inferior conchae according to their position.
The superior and middle conchae are parts of the ethmoid bone, whereas the inferior conchae are separate bones.
The inferior and middle conchae project medially and inferiorly, producing air passageways called the inferior and middle meatus (L. passage). Note: the plural of "meatus" is the same as the singular.
The short superior conchae conceal the superior meatus.
The space posterosuperior to the superior concha is called the sphenoethmoidal recess.
Maxillary Third Permanent Molar
Dental Anatomy
Maxillary Third Permanent Molar
They are the teeth most often congenitally missing
Facial: The crown is usually shorter in both axial and mesiodistal dimensions. Two buccal roots are present, but in most cases they are fused. The mesial buccal cusp is larger than the distal buccal cusp.
Lingual: In most thirds, there is just one large lingual cusp. In some cases there is a poorly developed distolingual cusp and a lingual groove. The lingual root is often fused to the to buccal cusps.
Proximal: The outline of the crown is rounded; it is often described as bulbous in dental literature. Technically, the mesial surface is the only 'proximal' surface. The distal surface does not contact another tooth.
Occlusal: The crown of this tooth is the smallest of the maxillary molars. The outline of the occlusal surface can be described as heart-shaped. The mesial lingual cusp is the largest, the mesial buccal is second in size, and the distal buccal cusp is the smallest.
Root Surface:-The root may have from one to as many as eight divisions. These divisions are usually fused and very often curved distally.
Hepatitis A virus.
General Pathology
Hepatitis A virus.
- Hepatitis A (HAV) is a self-limited hepatitis caused by an RNA virus
- Symptoms last 2 to 4 weeks.
- There is no risk of developing chronic hepatitis in the future.
- Incubation period is short, lasting 2 to 6 weeks.
- Infection is identified by HAV-specific antibodies (IgM if acute, IgG if past disease).
- The usual route of infection is fecal-oral transmission by contaminated food. There is no carrier state and no chronic disease
- Laboratory diagnosis: ELISA test for IgM antibody.
- Vaccine: killed virus.
- Prevention: serum immunoglobulins are available.
Efficiency in Heat Sterilization
Oral and Maxillofacial SurgeryTests for Efficiency in Heat Sterilization – Sterilization Monitoring
Effective sterilization is crucial in healthcare settings to ensure the
safety of patients and the efficacy of medical instruments. Various monitoring
techniques are employed to evaluate the sterilization process, including
mechanical, chemical, and biological parameters. Here’s an overview of these
methods:
1. Mechanical Monitoring
Parameters Assessed:
Cycle Time: The duration of the sterilization
cycle.
Temperature: The temperature reached during the
sterilization process.
Pressure: The pressure maintained within the
sterilizer.
Methods:
Gauges and Displays: Observing the gauges or
digital displays on the sterilizer provides real-time data on the cycle
parameters.
Recording Devices: Some tabletop sterilizers are
equipped with recording devices that print out the cycle parameters for
each load.
Interpretation:
While correct readings indicate that the sterilization conditions
were likely met, incorrect readings can signal potential issues with the
sterilizer, necessitating further investigation.
2. Biological Monitoring
Spore Testing:
Biological Indicators: This involves using spore
strips or vials containing Geobacillus stearothermophilus,
a heat-resistant bacterium.
Frequency: Spore testing should be conducted weekly to
verify the proper functioning of the autoclave.
Interpretation: If the spores are killed after the
sterilization cycle, it confirms that the sterilization process was
effective.
3. Thermometric Testing
Thermocouple:
A thermocouple is used to measure temperature at two locations:
Inside a Test Pack: A thermocouple is placed
within a test pack of towels to assess the temperature reached in
the center of the load.
Chamber Drain: A second thermocouple measures
the temperature at the chamber drain.
Comparison: The readings from both locations are
compared to ensure that the temperature is adequate throughout the load.
4. Chemical Monitoring
Brown’s Test:
This test uses ampoules containing a chemical indicator that changes
color based on temperature.
Color Change: The indicator changes from red
through amber to green at a specific temperature, confirming that the
required temperature was reached.
Autoclave Tape:
Autoclave tape is printed with sensitive ink that changes color when
exposed to specific temperatures.
Bowie-Dick Test: This test is a specific
application of autoclave tape, where two strips are placed on a piece of
square paper and positioned in the center of the test pack.
Test Conditions: When subjected to a temperature
of 134°C for 3.5 minutes, uniform color development
along the strips indicates that steam has penetrated the load
effectively.
Properties of inhalation anesthetics
Pharmacology
Properties of inhalation anesthetics
The lower the solubility, the faster the onset and the faster the recoverability.
All general anesthetics:
1. inhibit the brain from responding to sensory stimulation.
2. block the sensory impulses from being recorded in memory.
3. prevent the sensory impulses from evoking “affect”.
Most general anesthetic agents act in part by interacting with the neuronal membranes to affect ion channels and membrane excitability.
· If the concentration given is too low:
1. Movement may occur
2. Reflex activity present (laryngeal spasm)
3. Hypertension
4. Awareness
Premedication of analgesic drugs and muscle relaxants are designed to minimise these effects
· If the concentration given is too high:
1. Myocardial depression
2. Respiratory depression
3. Delayed recovery
INFLAMMATION
General Pathology
INFLAMMATION
Response of living tissue to injury, involving neural, vascular and cellular response.
ACUTE INFLAMMATION
It involves the formation of a protein .rich and cellullar exudate and the cardinal signs are calor, dolor, tumour, rubor and function loss
The basic components of the response are
Haemodynamic changes.
Permeability changes
Leucocyte events.
1. Haemodynamic Changes :
Transient vasoconstriction followed by dilatation.
Increased blood flow in arterioles.
More open capillary bed.
Venous engorgement and congestion.
Packing of microvasculature by RBC (due to fluid out-pouring)
Vascular stasis.
Change in axial flow (resulting in margination of leucocytes)
.2. Permeability Changes:
Causes.
Increased intravascular hydrostatic pressure.
Breakdown of tissue proteins into small molecules resulting in
increased tissue osmotic pressure.
Increased permeability due to chemical mediators, causing an
immediate transient response. .
Sustained response due to direct damage to microcirculation.
3. White Cell Events:
.Margination - due to vascular stasis and change in axial flow.
Pavementing - due to endothelial cells swollen and more sticky.
Leucocytes more adhesive.
Binding by a plasma component
Emigration - of leucocytes by amoeboid movement between endhothe1ial cells and beyond the basement membrane. The passive movement of RBCs through the gaps created during emigration is called diapedesis
Chemotaxis - This is a directional movement, especially of polymorphs and monocytes towards a concentration gradient resulting in aggregation of these cells at the site of inflammation. .Chemotactic agents may be:
Complement components. (C3and C5 fragments and C567)
Bacterial products.
Immune complexes, especially for monocyte.
Lymphocytic factor, especially for monocyte.
Phagocytosis - This includes recognition, engulfment and intracellular degradation. It is aided by .Opsonins., Specific antibodies., Surface provided by fibrin meshwork.
Functions of the fluid and cellular exudate
1. Dilution of toxic agent.
2. Delivers serum factors like antibodies and complement components to site of inflammation.
3. Fibrin formed aids In :
Limiting inflammation
Surface phagocytosis
Framework for repair.
4. Cells of the exudate:
Phagocytose and destroy the foreign agent.
Release lytic enzymes when destroyed, resulting in extracellular killing of organisms- and digestion of debris to enable healing to occur