NEET MDS Synopsis
Molecular techniques
General Pathology
Molecular techniques
Different molecular techniques such as fluorescent in situ hybridization, Southern blot, etc... can be used to detect genetic diseases.
SALIVARY GLANDS -Structure
Dental Anatomy
Structure
There are 3 pairs
The functional unit is the adenomere.
The adenomere consists of secreting units and an intercalated duct, which opens, in a striated duct.
An secreting unit can be:
- mucous secreting
- serous secreting
THE SECRETING UNIT
THE CELLS
Serous cells
(seromucus cells=secrete also polysaccharides), They have all the features of a cell specialized for the synthesis, storage, and secretion of protein
Pyramidal, Nuclei are rounded and more centrally placed, In the basal 1/3 there is an accumulation of Granular EPR, In the apex there are proteinaceous secretory granules, Cells stain well with H & E (red), Between cells are intercellular secretory capillaries
Rough endoplasmic reticulum (ribosomal sites-->cisternae)
Prominent Golgi-->carbohydrate moieties are added
Secretory granules-->exocytosis
The secretory process is continuous but cyclic
There are complex foldings of cytoplasmic membrane
The junctional complex consists of: 1) tight junctions (zonula occludens)-->fusion of outer cell layer, 2) intermediate junction (zonula adherens)-->intercellular communication, 3)desmosomes-->firm adhesion
Mucus cells
Pyramidal, Nuclei are flattened and near the base, Have big clear secretory granules
Cells do not stain well with H & E (white)
Production, storage, and secretion of proteinaceous material; smaller enzymatic component
-more carbohydrates-->mucins=more prominent Golgi
-less prominent (conspicuous) rough endoplasmic reticulum, mitochondria
-less interdigitations
Myoepithelial cells
Star-shaped, Centrally located nucleus, Long cytoplasmic arms - bound to the secretory cells by desmosomes, Have fibrils like smooth muscle, Squeeze the secretory cell
One, two or even three myoepithelial cells in each salivary and piece body, four to eight processes
Desmosomes between myoepithelial cells and secretory cells myofilaments frequently aggregated to form dark bodies along the course of the process. The myoepithelial cells of the intercalated ducts are more spindled-shaped and fewer processes
Ultrastructure very similar to that of smooth muscle cells (myofilaments, desmosomal attachments)
Functions of myoepithelial cells
-Support secretory cells
-Contract and widen the diameter of the intercalated ducts
-Contraction may aid in the rupture of acinar cells of epithelial origin
Ductal system
Three classes of ducts:
Intercalated ducts
They have small diameter; lined by small cuboidal cells; nucleus located in the center. They have a well-developed RER, Golgi apparatus, occasionally secretory granules, few microvilli. Myoepithelial cells are also present. Intercalated ducts are prominent in salivary glands having a watery secretion (parotid).
Striated ducts
They have columnar cells, a centrally located nucleus, eosinophilic cytoplasm. Prominenty striations that refer to indentations of the cytoplasmic membrane with many mitochondria present between the folds. Some RER and some Golgi. The cells have short microvilli.
The cells of the striated ducts modify the secretion (hypotonic solution=low sodium and chloride and high potassium). There is also presence of few basal cells.
Terminal excretory ducts
Near the striated ducts they have the same histology as the striated ducts. As the duct reaches the oral mucosa the lining becomes stratified. In the terminal ducts one can find goblet cells, basal cells, clear cells. The terminal ducts alter the electrolyte concentration and add mucoid substance.
Connective tissue
Presence of fibroblasts, inflammatory cells, mast cells, adipose cells
Extracellular matrix (glycoproteins and proteoglycans)
Collagen and oxytalan fibers
Nerve supply
The innervation of salivary glands is very complicated. There is no direct inhibitory innervation. There are parasympathetic and sympathetic impulses, the parasympathetic are more prevalent.
The parasympathetic impulses may occur in isolation, evoke most of the fluid to be excreted, cause exocytosis, induce contraction of myoepithelial cells (sympathetic too) and cause vasodialtion. There are two types of innervation: epilemmal and hypolemmal. There are beta-adrenergic receptors that induce protein secretion and L-adrenergic and cholinergic receptors that induce water and electrolyte secretion.
Hormones can influence the function of the salivary glands. They modify the salivary content but cannot initiate salivary flow.
Age changes
Fibrosis and fatty degenerative changes
Presence of oncocytes (eosinophilic cells containing many mitochondria)
Clinical considerations
Role of drugs, systemic disorders, bacterial or viral infections, therapeutic radiation, obstruction, formation of plaque and calculus.
- Rich capillary networks surround the adenomeres.
Hand Instruments
Conservative DentistryHand Instruments - Design and Balancing
Hand instruments are essential tools in dentistry, and their design
significantly impacts their effectiveness and usability. Proper balancing and
angulation of these instruments are crucial for achieving optimal control and
precision during dental procedures. Below is an overview of the key aspects of
hand instrument design, focusing on the shank, angulation, and balancing.
1. Importance of Balancing
A. Definition of Balance
Balanced Instruments: A hand instrument is
considered balanced when the concentration of force can be applied to the
blade without causing rotation in the grasp of the operator. This balance is
essential for effective cutting and manipulation of tissues.
B. Achieving Balance
Proper Angulation of Shank: The shank must be
angled appropriately so that the cutting edge of the blade lies within the
projected diameter of the handle. This design minimizes the tendency for the
instrument to rotate during use.
Off-Axis Blade Edge: For optimal anti-rotational
design, the blade edge should be positioned off-axis by 1 to 2 mm.
This slight offset helps maintain balance while allowing effective force
application.
2. Shank Design
A. Definition
Shank: The shank connects the handle to the blade
of the instrument. It plays a critical role in the instrument's overall
design and functionality.
B. Characteristics
Tapering: The shank typically tapers from the
handle down to the blade, which can enhance control and maneuverability.
Surface Texture: The shank is usually smooth,
round, or tapered, depending on the specific instrument design.
Angulation: The shank may be straight or angled,
allowing for various access and visibility during procedures.
C. Classification Based on Angles
Instruments can be classified based on the number of angles in the
shank:
Straight: No angle in the shank.
Monoangle: One angle in the shank.
Binangle: Two angles in the shank.
Triple-Angle: Three angles in the shank.
3. Angulation and Control
A. Purpose of Angulation
Access and Stability: The angulation of the
instrument is designed to provide better access to the treatment area while
maintaining stability during use.
B. Proximity to Long Axis
Control: The closer the working point (the blade)
is to the long axis of the handle, the better the control over the
instrument. Ideally, the working point should be within 3 mm of
the center of the long axis of the handle for optimal control.
4. Balancing Examples
A. Balanced Instrument
Example A: When the working end of the instrument
lies within 2-3 mm of the long axis of the handle, it
provides effective balancing. This configuration allows the operator to
apply force efficiently without losing control.
B. Unbalanced Instrument
Example B: If the working end is positioned away
from the long axis of the handle, it results in an unbalanced instrument.
This design can lead to difficulty in controlling the instrument and may
compromise the effectiveness of the procedure.
OEDEMA
General Pathology
OEDEMA
Excessive accumulation of fluid in the extra vascular compartment (intersttitial tissues). This includes ascites (peritoneal sac), hydrothorax (pleural cavity) hydropericardium (pericardial space) and anasarca (generalised)
Factors which tend to accumulate interstitial fluid are:
- Intravascular hydrostatic pressure
- Interstitial osmotic pressure.
- Defective lymphatic drainage.
- Increased capillary permeability.
Factors that draw fluid into circulation are:
- Tissue hydrostatic-pressure (tissue tension).
- Plasma osmotic pressure,
Oedema fluid can be of 2 types:
A. Exudate.
It is formed due to increased capillary permeability as in inflammation.
B. Transudate
Caused by alterations of hydrostatic and osmotic pressures.
Exudate
Transudate
Specific Gravity
>1.018
1.012
Protein Content
High
Low
Nature of Protein
All Plasma Protein
Albumin mostly
Spontaneous Clotting
High(Inflammatory Cells)
Low
Local Oedema
1. Inflammatory oedema. Mechanisms are.
- Increased capillary permeability.
- Increased vascular hydrostatic pressure.
- Increased tissue osmotic pressure.
2.Hypersensitivity reactions especially types I and III
3. Venous obstruction :
- Thrombosis.
- Pressure from outside as in pregnancy, tourniquets.
4. Lymphatic obstruction:
- Elephantiasis in fillariasis
- Malignancies (Peau de orange in breast cancer).
Generalized Oedema
1. Cardiac oedema
Factors :Venous pressure increased.
2. Renal oedema
- Acute glomerulonephritis
- Nephrotic syndrome
3. Nutritional (hypoproteinaemic) oedema. it is seen in
- Starvation and Kwashiorkor
- Protein losing enteropathy
4. Hepatic oedema (predominantly ascites)
Factors:
- Fall in plasma protein synthesis
- Raised regional lymphatic and portal venous pressure
5. Oedema due to adrenal corticoids
As in Cushing's Syndrome
Pulmonary oedema
- Left heart failure and mitral stenosis.
- Rapid flv infusion specially in a patient of heart failure.
PULP
Dental Anatomy
PULP
Coronal
Occupies and resembles the crown,
Contains the pulp horns
It decreases in size with age
Radicular
Occupies roots
Contains the apical foramen
It decreases in size with age
Accessory apical canals
PULP FUNCTIONS
Inductive: The pulp anlage initiates tooth formation and probably induces the dental organ to become a particular type of tooth.
Formative: Pulp odontoblasts develop the organic matrix and function in its calcification.
Nutritive: Nourishment of dentin through the odontoblasts.
Protective: Sensory nerves in the tooth respond almost always with PAIN to all stimuli (heat, cold, pressure, operative procedures, chamical agents).
Defensive or reparative: It responds to irritation by producing reparative dentin. The response to stimuli is inflammation.
Histologically the pulp consists of delicate collagen fibers, blood vessels, lymphatics, nerves and cells. A histologic section of the pulp reveals four cellular zones:
Odontoblastic
Cell-free (Weil)
Cell-rich
Pulp core
Pemphigus
General Pathology
Pemphigus
1. Ulcerative lesions on the skin and oral mucosa.
2. An autoimmune disease in which patients have autoantibodies against hemidemosomal attachment of epidermis cells.
3. Histologically characterized by acantholysis, in which epidermal cells appear to detach and separate from each other, as seen by Tzanck smears.
4. Can be life-threatening if untreated.
5. A positive Nikolsky sign is observed.
Because of sloughing of the epidermis, a red blister forms after pressure is applied to affected skin.
6. Treatment: corticosteroids.
Pulpectomy
Pedodontics
Pulpectomy
Primary tooth endodontics, commonly referred to as pulpectomy, is a dental
procedure aimed at treating the pulp of primary (deciduous) teeth that have
become necrotic or infected. The primary goal of this treatment is to maintain
the integrity of the primary tooth, thereby preserving space for the permanent
dentition and preventing complications associated with tooth loss.
Indications for Primary Tooth Endodontics
Space Maintenance:
The foremost indication for performing a pulpectomy on a primary tooth is to
maintain space in the dental arch. The natural primary tooth serves as the
best space maintainer, preventing adjacent teeth from drifting into the
space left by a lost tooth. This is particularly crucial when the second
primary molars are lost before the eruption of the first permanent molars,
as constructing a space maintainer in such cases can be challenging.
Restorability:
The tooth must be restorable with a stainless steel crown.
If the tooth is structurally sound enough to support a crown after the
endodontic treatment, pulpectomy is indicated.
Absence of Pathological Root Resorption:
There should be no significant pathological root resorption present. The
integrity of the roots is essential for the success of the procedure and the
longevity of the tooth.
Healthy Bone Layer:
A layer of healthy bone must exist between the area of pathological bone
resorption and the developing permanent tooth bud. Radiographic evaluation
should confirm that this healthy bone layer is present, allowing for normal
bone healing post-treatment.
Presence of Suppuration:
The presence of pus or infection indicates that the pulp is necrotic,
necessitating endodontic intervention.
Pathological Periapical Radiolucency:
Radiographic evidence of periapical radiolucency suggests that there
is an infection at the root apex, which can be treated effectively
with pulpectomy.
Contraindications for Primary Tooth Endodontics
Floor of the Pulp Opening into the Bifurcation:
If the floor of the pulp chamber opens into the bifurcation of the
roots, it complicates the procedure and may lead to treatment failure.
Extensive Internal Resorption:
Radiographic evidence of significant internal resorption indicates that the
tooth structure has been compromised to the extent that it cannot support a
stainless steel crown, making pulpectomy inappropriate.
Severe Root Resorption:
If more than two-thirds of the roots have been resorbed, the tooth may not
be viable for endodontic treatment.
Inaccessible Canals:
Teeth that lack accessible canals, such as first primary molars, may not be
suitable for pulpectomy due to the inability to adequately clean and fill
the canals.
The Pulpectomy Procedure
Accessing the Pulp Chamber:
The procedure begins with the use of a high-speed bur to create an access
opening into the pulp chamber of the affected tooth.
Canal Preparation:
Hedstrom files are employed to clean and shape the root canals.
This step is crucial for removing necrotic tissue and debris from the
canals.
Irrigation:
The canals are irrigated with sodium hypochlorite (hypochlorite
solution) to wash out any remaining tissue and loose dentin,
ensuring a clean environment for filling.
Filling the Canals:
After thorough cleaning and shaping, the canals and pulp chamber are
filled with zinc oxide eugenol, which serves as a biocompatible filling
material.
Post-Operative Evaluation:
A post-operative radiograph is taken to evaluate the condensation of the
filling material and ensure that the procedure was successful.
Restoration:
Finally, the tooth is restored with a stainless steel crown to provide
protection and restore function.
Applications of the Henderson-Hasselbalch equation
Biochemistry
Applications of the Henderson-Hasselbalch equation
• Calculate the ratio of CB to WA, if pH is given
• Calculate the pH, if ratio of CB to WA is known
• Calculate the pH of a weak acid solution of known concentration
• Determine the pKa of a WA-CB pair
• Calculate change in pH when strong base is added to a solution of weak acid. This is represented in a titration curve
• Calculate the pI