NEET MDS Synopsis
Cholelithiasis
General Pathology
Cholelithiasis (Biliary calculi)
- These are insoluble material found within the biliary tract and are formed of bile constituents (cholesterol, bile pigments and calcium salts).
Sites: - -Gall bladder, extra hepatic biliary tract. Rarely, intrahepatic biliary tract.
Predisposing factors:-
- Change in the composition of bile. - It is the disturbance of the ratio between cholesterol and lecithin or bile salts which may be due to Hypercholesterolaemia which may be hereditary or the 4 F (Female, Forty, Fatty, Fertile). Drugs as clofibrate and exogenous estrogen. High intake of calories (obesity).
Increased concentration of bilirubin in bile- pigment stones
Hypercalcaemia:- Calcium carbonate stones.
2- Staisis.
3- Infection.
Pathogenesis i- Nucleation or initiation of stone formation:- The nidus may be cholesterol “due to supersaturation” Bacteria, parasite
RBCs or mucous.
ii- Acceleration:- When the stone remains in the gall bladder, other constituents are added to the
nidus to form the stone.
Complications of gall stones:-
- Predispose to infection.- Chronic irritation leading to
a. Ulceration b. Squamous metaplasia & carcinoma.
Drugs used in cough.
Pharmacology
PHARYNGEAL DEMULCENTS
Administered in the form of lozenges, cough drops and cough linctus.
Produce soothing action on throat directly and by increasing the flow of saliva and provide symptomatic relief from dry cough.
EXPECTORANT
Expectorants are the drugs which increase the production of bronchial secretion and reduce its viscosity to facilitate its removal by coughing.
ANTITUSSIVES
They are central cough suppressants and act centrally to raise the threshold of cough centre and inhibit the cough reflex by suppressing the coordinating cough centre in the medulla oblongata.
Codeine - it depresses cough centre but is less constipating and abuse liability is low.
Pholcodeine is similar to codeine in efficacy and is longer acting. It has no analgesic or addicting property.
Noscapine is another opium alkaloid of benzylisoquinoline group. It is used as antitussive with no analgesic and drug abuse or drug dependence property.
Dextromethorphan is a synthetic compound and its dextroisomer is used as antitussive and is as effective as codeine
Pipazethate is another synthetic compound of phenothiazine category used as antitussive with little analgesic and sedative properties.
ANTIHISTAMINICS
They do not act on cough centre but provide relief due to their sedative and anticholinergic action.
BRONCHODILATORS
Bronchodilators are helpful in individuals with cough and bronchoconstriction due to bronchial hyperreactivity. They help by improving the effectiveness of cough in clearing secretions.
Root Canal Sealers
Endodontics
Root canal sealers are materials used in endodontics to fill the space between
the root canal filling material (usually gutta-percha) and the walls of the root
canal system. Their primary purpose is to provide a fluid-tight seal, preventing
the ingress of bacteria and fluids, and to enhance the overall success of root
canal treatment. Here’s a detailed overview of root canal sealers, including
their types, properties, and clinical considerations.
Types of Root Canal Sealers
Zinc Oxide Eugenol (ZOE) Sealers
Composition: Zinc oxide powder mixed with eugenol (oil of
cloves).
Properties:
Good sealing ability.
Antimicrobial properties.
Sedative effect on the pulp.
Uses: Commonly used in conjunction with gutta-percha for
permanent root canal fillings. However, it can be difficult to remove if
retreatment is necessary.
Resin-Based Sealers
Composition: Composed of resins, fillers, and solvents.
Properties:
Excellent adhesion to dentin and gutta-percha.
Good sealing ability and low solubility.
Aesthetic properties (some are tooth-colored).
Uses: Suitable for various types of root canal systems,
especially in cases requiring high bond strength and sealing ability.
Calcium Hydroxide Sealers
Composition: Calcium hydroxide mixed with a vehicle (such as
glycol or water).
Properties:
Biocompatible and promotes healing.
Antimicrobial properties.
Can stimulate the formation of reparative dentin.
Uses: Often used in cases where a temporary seal is needed or
in apexification procedures.
Glass Ionomer Sealers
Composition: Glass ionomer cement (GIC) materials.
Properties:
Good adhesion to dentin.
Fluoride release, which can help in preventing secondary caries.
Biocompatible.
Uses: Used in conjunction with gutta-percha, particularly in
cases where fluoride release is beneficial.
Bioceramic Sealers
Composition: Made from calcium silicate and other bioceramic
materials.
Properties:
Excellent sealing ability and biocompatibility.
Hydrophilic, allowing for moisture absorption and expansion to fill
voids.
Promotes healing and tissue regeneration.
Uses: Increasingly popular for permanent root canal fillings
due to their favorable properties.
Properties of Ideal Root Canal Sealers
An ideal root canal sealer should possess the following properties:
Biocompatibility: Should not cause adverse reactions in periapical
tissues.
Sealing Ability: Must provide a tight seal to prevent bacterial
leakage.
Adhesion: Should bond well to both dentin and gutta-percha.
Flowability: Should be able to flow into irregularities and fill
voids.
Radiopacity: Should be visible on radiographs for easy
identification.
Ease of Removal: Should allow for easy retreatment if necessary.
Antimicrobial Properties: Should inhibit bacterial growth.
Clinical Considerations
Selection of Sealer: The choice of sealer depends on the clinical
situation, the type of tooth being treated, and the specific properties
required for the case.
Application Technique: Proper application techniques are crucial
for achieving an effective seal. This includes ensuring that the root canal
is adequately cleaned and shaped before sealer application.
Retreatment: Some sealers, like ZOE, can be challenging to remove
during retreatment, while others, like bioceramic sealers, may offer better
retrievability.
Setting Time: The setting time of the sealer should be considered,
especially in cases where immediate restoration is planned.
Conclusion
Root canal sealers play a vital role in the success of endodontic treatment by
providing a seal that prevents bacterial contamination and promotes healing.
Understanding the different types of sealers, their properties, and their
clinical applications is essential for dental professionals to ensure effective
and successful root canal therapy.
Role of Coenzymes
Biochemistry
Role of Coenzymes
The functional role of coenzymes is to act as transporters of chemical groups from one reactant to another.
Ex. The hydride ion (H+ + 2e-) carried by NAD or the mole of hydrogen carried by FAD;
The amine (-NH2) carried by pyridoxal phosphate
Types of Expansion
OrthodonticsExpansion in orthodontics refers to the process of widening the dental arch
to create more space for teeth, improve occlusion, and enhance facial
aesthetics. This procedure is particularly useful in treating dental crowding,
crossbites, and other malocclusions. The expansion can be achieved through
various appliances and techniques, and it can target either the maxillary
(upper) or mandibular (lower) arch.
Types of Expansion
Maxillary Expansion:
Rapid Palatal Expansion (RPE):
Description: A common method used to widen the
upper jaw quickly. It typically involves a fixed appliance that is
cemented to the molars and has a screw mechanism in the middle.
Mechanism: The patient or orthodontist turns
the screw daily, applying pressure to the palatine suture, which
separates the two halves of the maxilla, allowing for expansion.
Indications: Used for treating crossbites,
creating space for crowded teeth, and improving the overall arch
form.
Duration: The active expansion phase usually
lasts about 2-4 weeks, followed by a retention phase to stabilize
the new position.
Slow Palatal Expansion:
Description: Similar to RPE but involves slower,
more gradual expansion.
Mechanism: A fixed appliance is used, but the screw
is activated less frequently (e.g., once a week).
Indications: Suitable for patients with less severe
crowding or those who may not tolerate rapid expansion.
Mandibular Expansion:
Description: Less common than maxillary expansion,
but it can be achieved using specific appliances.
Mechanism: Appliances such as the mandibular
expansion appliance can be used to widen the lower arch.
Indications: Used in cases of dental crowding or to
correct certain types of crossbites.
Mechanisms of Expansion
Skeletal Expansion: Involves the actual widening of the
bone structure (e.g., the maxilla) through the separation of the midpalatine
suture. This is more common in growing patients, as their bones are more
malleable.
Dental Expansion: Involves the movement of teeth within
the alveolar bone. This can be achieved through the application of forces
that move the teeth laterally.
Indications for Expansion
Crossbites: To correct a situation where the upper
teeth bite inside the lower teeth.
Crowding: To create additional space for teeth that are
misaligned or crowded.
Improving Arch Form: To enhance the overall shape and
aesthetics of the dental arch.
Facial Aesthetics: To improve the balance and symmetry
of the face, particularly in growing patients.
Advantages of Expansion
Increased Space: Creates additional space for teeth,
reducing crowding and improving alignment.
Improved Function: Corrects functional issues related
to occlusion, such as crossbites, which can lead to better chewing and
speaking.
Enhanced Aesthetics: Improves the overall appearance of
the smile and facial profile.
Facilitates Orthodontic Treatment: Provides a better
foundation for subsequent orthodontic procedures.
Limitations and Considerations
Age Factor: Expansion is generally more effective in
growing children and adolescents due to the flexibility of their bones. In
adults, expansion may require surgical intervention (surgical-assisted rapid
palatal expansion) due to the fusion of the midpalatine suture.
Discomfort: Patients may experience discomfort or
pressure during the expansion process, especially with rapid expansion.
Retention: After expansion, a retention phase is
necessary to stabilize the new arch width and prevent relapse.
Potential for Relapse: Without proper retention, there
is a risk that the teeth may shift back to their original positions.
Rheumatic fever
General Pathology
Rheumatic fever
Before antibiotic therapy, this was the most common cause of valvular disease.
1. Usually preceded by a group A streptococci respiratory infection; for example, strep throat.
2. All three layers of the heart may be affected. The pathologic findings include Aschoff bodies, which are areas of focal necrosis surrounded by a dense inflammatory infiltration.
3. Most commonly affects the mitral valve, resulting in mitral valve stenosis, regurgitation, or both.
Hereditary spherocytosis
General Pathology
Hereditary spherocytosis.
Functionally normal cells which are destroyed .in spleen because of the structural abnormality. It is transmitted as an autosomal dominant trait
Congenital hemolytic anemia due to genetically determined abnormal spectrin and ankyrin molecules, leading to defects in red blood cell membrane, causing spherical shape and lack of plasticity
Red blood cells become trapped within spleen and have less than usual 120 day lifespan
Splenic function is normal
Osmotic fragility: increased; basis for diagnostic testing
Description
Firm, deep red tissue, thin capsule, no grossly identifiable malpighian follicles, 100-1000g
Peripheral blood images
Marked congestion in cords
Sinuses appear empty but actually contain ghost red blood cells
May have prominent endothelial lined sinuses, hemosiderin deposition, erythrophagocytosis
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