NEET MDS Synopsis
Erythema nodosum
General Pathology
Erythema nodosum is the MCC of inflammation of subcutaneous fat (panniculitis).
- it may be associated with tuberculosis, leprosy, certain drugs (sulfonamides), and is commonly a harbinger of coccidioidomycosis and sarcoidosis.
- commonly presents on the lower extremities with exquisitely tender, raised erythematous plaques and nodules.
- self-limited disease.
Microscopic structure
Anatomy
Cartilage model is covered with perichondrium that is converted to periosteum
Diaphysis-central shaft
Epiphysis-located at either end of the diaphysis
Growth in length of the bone is provided by the emetaphyseal plate located between the epiphyseal cartilage and the diaphysis
Blood capillaries and the mesenchymal cells infiltrate the spaces left by the destroyed chondrocytes
Osteoblasts are derived from the undifferentiated cells; form an osseous matrix in the cartilage
Bone appears at the site where there was cartilage
Microscopic structure
Compact bone is found on the exterior of all bones; canceIlous bone is found in the interior
Surface of compact bone is covered by periosteum that is attached by Sharpey's fibers
Blood vessels enter the periosteum via Volkmann's canals and then enter the haversian canals that are formed by the canaliculi and lacunae
Marrow
FiIls spaces of spongy bone
Contains blood vessels and blood ceIls in various stages of development
Types
Red bone marrow
Formation of red blood ceIls (RBCs) and some white blood cells (WBCs) in this location
Predominate type of marrow in newborn
Found in spongy bone of adults (sternum, ribs, vertebrae, and proximal epiphyses of long bones)
Yellow bone marrow
Fatty marrow
Generally replaces red bone marrow in the adult, except in areas mentioned above
Ossification is completed as the proximal epiphysis joins with the diaphysis between the twentieth and twenty-fifth year
Insulin
Biochemistry
Insulin
Insulin is a polypeptide hormone synthesized in the pancreas by β-cells, which construct a single chain molecule called proinsulin.
Insulin, secreted by the β-cells of the pancreas in response to rising blood glucose levels, is a signal that glucose is abundant.
Insulin binds to a specific receptor on the cell surface and exerts its metabolic effect by a signaling pathway that involves a receptor tyrosine kinase phosphorylation cascade.
The pancreas secretes insulin or glucagon in response to changes in blood glucose.
Each cell type of the islets produces a single hormone: α-cells produce glucagon; β-cells, insulin; and δ-cells, somatostatin.
Insulin secretion
When blood glucose rises, GLUT2 transporters carry glucose into the b-cells, where it is immediately converted to glucose 6-phosphate by hexokinase IV (glucokinase) and enters glycolysis. The increased rate of glucose catabolism raises [ATP], causing the closing of ATP-gated K+ channels in the plasma membrane. Reduced efflux of K+ depolarizes the membrane, thereby opening voltage-sensitive Ca2+ channels in the plasma membrane. The resulting influx of Ca2+ triggers the release of insulin by exocytosis.
Insulin lowers blood glucose by stimulating glucose uptake by the tissues; the reduced blood glucose is detected by the β-cell as a diminished flux through the hexokinase reaction; this slows or stops the release of insulin. This feedback regulation holds blood glucose concentration nearly constant despite large fluctuations in dietary intake.
Insulin counters high blood glucose
Insulin stimulates glucose uptake by muscle and adipose tissue, where the glucose is converted to glucose 6-phosphate. In the liver, insulin also activates glycogen synthase and inactivates glycogen phosphorylase, so that much of the glucose 6-phosphate is channelled into glycogen.
Diabetes mellitus, caused by a deficiency in the secretion or action of insulin, is a relatively common disease. There are two major clinical classes of diabetes mellitus: type I diabetes, or insulin-dependent diabetes mellitus (IDDM), and type II diabetes, or non-insulin-dependent diabetes mellitus (NIDDM), also called insulin-resistant diabetes. In type I diabetes, the disease begins early in life and quickly becomes severe. IDDM requires insulin therapy and careful, lifelong control of the balance between dietary intake and insulin dose.
Characteristic symptoms of type I (and type II) diabetes are excessive thirst and frequent urination (polyuria), leading to the intake of large volumes of water (polydipsia)
Type II diabetes is slow to develop (typically in older, obese individuals), and the symptoms are milder.
Fourth Generation:
Pharmacology
Fourth Generation:
These are extended spectrum antibiotics. They are resistant to beta lactamases.
Cefipime
Classification of Early Childhood Caries
Pedodontics
Classification of Early Childhood Caries (ECC)
Type 1 ECC (Mild to Moderate)
Affects molars and incisors
Typically seen in children aged 2-5 years
Type 2 ECC (Moderate to Severe)
Characterized by labiolingual caries affecting maxillary incisors,
with or without molar involvement
Usually observed soon after the first tooth erupts
Mandibular incisors remain unaffected
Often caused by inappropriate bottle feeding
Type 3 ECC (Severe)
Involves all primary teeth
Commonly seen in children aged 3-5 years
Mandibular First Deciduous Molar
Dental Anatomy
Mandibular First Deciduous Molar
-This tooth doesn't resemble any other tooth. It is unique unto itself.
-There are two roots.
-There is a strong bulbous enamel bulge buccally at the mesial.
- the mesiolingual cusps on this tooth is the highest and largest of the cusps.
Condensers/pluggers
Conservative DentistryCondensers/pluggers are instruments used to deliver the forces of compaction
to the underlying restorative material. There are
several methods for the application of these forces:
1.
Hand pressure: use of this method alone is contraindicated
except in a few situations like adapting the first piece of gold to
the convenience or point angles and where the line of force will not permit
use of other methods. Powdered golds are also
known to be better condensed with hand pressure. Small condenser points of
0.5 mm in diameter are generally
recommended as they do not require very high forces for their manipulation.
2.
Hand malleting: Condensation by hand malleting is a team work
in which the operator directs the condenser and moves it
over the surface, while the assistant provides rhythmic blows from the
mallet. Long handled condensers and leather faced
mallets (50 gms in weight) are used for this purpose. The technique allows
greater control and the condensers can be
changed rapidly when required. However, with the introduction of mechanical
malleting, use of this method has decreased
considerably.
3.
Automatic hand malleting: This method utilizes a spring loaded
instrument that delivers the desired force once the spiral
spring is released. (Disadvantage is that the blow descends very rapidly even
before full pressure has been exerted on the
condenser point.
4.
Electric malleting (McShirley electromallet): This instrument
accommodates various shapes of con-denser points and has a
mallet in the handle itself which remains dormant until wished by the
operator to function. The intensity or amplitude
generated can vary from 0.2 ounces to 15 pounds and the frequency can range
from 360-3600 cycles/minute.
5.
Pneumatic malleting (Hollenback condenser): This is the most
recent and satisfactory method first developed by
Dr. George M. Hollenback. Pneumatic mallets consist of vibrating nit
condensers and detachable tips run by
compressed air. The air is carried through a thin rubber tubing attached to
the hand piece. Controlling the air
pressure by a rheostat nit allows adjusting the frequency and amplitude of
condensation strokes. The construction
of the handpiece is such that the blow does not fall until pressure is placed
on the condenser point. This continues
until released. Pneumatic mallets are available with both straight and angled
for handpieces.
Sutures
Oral and Maxillofacial SurgerySutures
Sutures are an essential component of oral surgery, used to close wounds,
secure grafts, and stabilize tissues after surgical procedures. The choice of
suture material and sterilization methods is critical for ensuring effective
healing and minimizing complications. Below is a detailed overview of suture
materials, specifically focusing on catgut and its sterilization methods.
Types of Suture Materials
Absorbable Sutures: These sutures are designed to be
broken down and absorbed by the body over time. They are commonly used in
oral surgery for soft tissue closure where long-term support is not
necessary.
Catgut: A natural absorbable suture made from the
intestinal mucosa of sheep or cattle. It is widely used in oral surgery
due to its good handling properties and ability to promote healing.
Non-Absorbable Sutures: These sutures remain in the body
until they are removed or until they eventually break down. They are used in
situations where long-term support is needed.
Catgut Sutures
Sterilization Methods: Catgut sutures must be properly
sterilized to prevent infection and ensure safety during surgical procedures.
Two common sterilization methods for catgut are:
Gamma Radiation Sterilization:
Process: Catgut sutures are sterilized using gamma
radiation, typically at a dose of 2.5 mega-rads. This
method effectively kills bacteria and other pathogens without
compromising the integrity of the suture material.
Preservation: After sterilization, catgut sutures
are preserved in a solution of 2.5 percent formaldehyde and denatured
absolute alcohol. This solution helps maintain the sterility of
the sutures while preventing degradation.
Packaging: The sutures are stored in spools or
foils to protect them from contamination until they are ready for use.
Chromic Acid Method:
Process: In this method, catgut sutures are
immersed in a solution containing 20 percent chromic acid and five
parts of 8.5 percent glycerin. This process not only sterilizes
the sutures but also enhances their durability.
Benefits: The chromic acid treatment helps to
secure a longer stay in the pack, meaning that the sutures can maintain
their strength and integrity for a more extended period before being
used. This is particularly beneficial in surgical settings where sutures
may need to be stored for some time.
Characteristics of Catgut Sutures
Absorbability: Catgut sutures are absorbable, typically
losing their tensile strength within 7 to 14 days, depending on the type
(plain or chromic).
Tensile Strength: They provide good initial tensile
strength, making them suitable for various surgical applications.
Biocompatibility: Being a natural product, catgut is
generally well-tolerated by the body, although some patients may have
sensitivities or allergic reactions.
Handling: Catgut sutures are easy to handle and tie,
making them a popular choice among surgeons.
Applications in Oral Surgery
Soft Tissue Closure: Catgut sutures are commonly used
for closing incisions in soft tissues of the oral cavity, such as after
tooth extractions, periodontal surgeries, and mucosal repairs.
Graft Stabilization: They can also be used to secure
grafts in procedures like guided bone regeneration or soft tissue grafting.