NEET MDS Synopsis
Glucocorticoids
PharmacologyGlucocorticoids
Cortisol (hydrocortisone) and its synthetic derivatives
Drug
Duration
Cortisol
Short
Prednisone
Medium
Triameinolone
Intermediate
Betamethasone
Long
Dexamethasone
Long
Mechanism
↓ the production of leukotrienes and prostaglandins - inhibits phospholipase A2 , inhibits expression of COX-2 , will also stimulate the bone marrow to produce neutrophils resulting in leukocytosis
halts inflammatory cascade
↓ leukocyte migration
↓ capillary permeability
↓ phagocytosis
↓ platelet-activating factor
↓ interleukins (e.g. IL-2)
may trigger apoptosis in dividing and non-dividing cells
used in cancer chemotherapy
Clinical use
anti-inflammatory
immunosuppression
cancer chemotherapy (prednisone most common)
CLL
Hodgkin's lymphomas
part of MOPP regimen
Addison disease
asthma
Toxicity
1) must taper dose to avoid toxicity
2) suppression of ACTH → shock state if abrupt withdrawal - > cortical atrophy, malaise, myalgia, arthralgia, fever
3) iatrogenic Cushing syndrome ->buffalo hump, moon facies, truncal obesity, muscle weakness and atrophy, thin skin, easy bruising, acne
4) osteoporosis - vertebral fractures, aseptic hip necrosis, ↓ skeletal growth in children
5) hyperglycemia (diabetes) -due to ↑ gluconeogenesis , glaucoma, cataracts, and other complications can subsequently result
6) ↑ GI acid release -ulcers
7) Na+ retention -> edema, HTN, hypokalemia alkalosis, hypocalcemia
8)↓ wound healing
9) ↑ infections
10) mental status changes
11) cataracts
Use of Nitrous Oxide (N₂O) in Pedodontics
PedodonticsUse of Nitrous Oxide (N₂O) in Pedodontics
Nitrous oxide, commonly known as "laughing gas," is frequently used in
pediatric dentistry for its sedative and analgesic properties. Here’s a detailed
overview of its use, effects, dosages, and contraindications:
Dosage and Effects of Nitrous Oxide
Common Dosage:
40% N₂O + 60% O₂: This combination is commonly used
for conscious sedation in pediatric patients.
Effects Based on Concentration:
5-25% N₂O:
Effects:
Moderate sedation
Diminution of fear and anxiety
Marked relaxation
Dissociative sedation and analgesia
25-45% N₂O:
Effects:
Floating sensation
Reduced blink rate
45-65% N₂O:
Effects:
Euphoric state (often referred to as "laughing gas")
Total anesthesia
Complete analgesia
Marked amnesia
Benefits of Nitrous Oxide in Pediatric Dentistry
Anxiolytic Effects: Helps reduce anxiety and fear,
making dental procedures more tolerable for children.
Analgesic Properties: Provides pain relief, allowing
for more comfortable treatment.
Rapid Onset and Recovery: Nitrous oxide has a quick
onset of action and is rapidly eliminated from the body, allowing for a
quick recovery after the procedure.
Control: The level of sedation can be easily adjusted
during the procedure, providing flexibility based on the child's response.
Contraindications for Nitrous Oxide Sedation
While nitrous oxide is generally safe, there are specific contraindications
where its use should be avoided:
Chronic Obstructive Pulmonary Disease (COPD): Patients
with COPD may have difficulty breathing with nitrous oxide.
Asthma: Asthmatic patients may experience exacerbation
of symptoms.
Respiratory Infections: Conditions that affect
breathing can be worsened by nitrous oxide.
Sickle Cell Anemia: For general anesthesia, all forms
of anemia, including sickle cell anemia, are contraindicated due to the risk
of hypoxia.
Otitis Media: The use of nitrous oxide can increase
middle ear pressure, which may be problematic.
Epilepsy: Patients with a history of seizures may be at
risk for seizure activity when using nitrous oxide.
BIOLOGICAL BUFFER SYSTEMS
Biochemistry
BIOLOGICAL BUFFER SYSTEMS
Cells and organisms maintain a specific and constant cytosolic pH, keeping biomolecules in their optimal ionic state, usually near pH 7. In multicelled organisms, the pH of the extracellular fluids (blood, for example) is also tightly regulated. Constancy of pH is achieved primarily by biological buffers : mixtures of weak acids and their conjugate bases
Body fluids and their principal buffers
Body fluids Principal buffers
Extracellular fluids {Biocarbonate buffer Protein buffer }
Intracellular fluids {Phosphate buffer, Protein }
Erythrocytes {Hemoglobin buffer}
CHARACTERISTICS AND CHEMISTRY OF HORMONES
Physiology
Each hormone in the body is unique. Each one is different in it's chemical composition, structure, and action. With respect to their chemical structure, hormones may be classified into three groups: amines, proteins, and steroids.
Amines- these simple hormones are structural variation of the amino acid tyrosine. This group includes thyroxine from the thyroid gland and epinephrine and norepinephrine from the adrenal medulla.
Proteins- these hormones are chains of amino acids. Insulin from the pancreas, growth hormone from the anterior pituitary gland, and calcitonin from the thyroid gland are all proteins. Short chains of amino acids are called peptides. Antidiuretic hormone and oxytocin, synthesized by the hypothalamus, are peptide hormones.
Steroids- cholesterol is the precursor for the steroid hormones, which include cortisol and aldosterone from the adrenal cortex, estrogen and progesterone from the ovaries, and testosterone from the testes.
Flossing
PeriodontologyFlossing Technique
Flossing is an essential part of oral hygiene that helps remove plaque and
food particles from between the teeth and along the gumline, areas that
toothbrushes may not effectively clean. Proper flossing technique is crucial for
maintaining gum health and preventing cavities.
Flossing Technique
Preparation:
Length of Floss: Take 12 to 18 inches of dental
floss. This length allows for adequate maneuverability and ensures that
you can use a clean section of floss for each tooth.
Grasping the Floss: Hold the floss taut between
your hands, leaving a couple of inches of floss between your fingers.
This tension helps control the floss as you maneuver it between your
teeth.
Inserting the Floss:
Slip Between Teeth: Gently slide the floss between
your teeth. Be careful not to snap the floss, as this can cause trauma
to the gums.
Positioning: Insert the floss into the area between
your teeth and gums as far as it will comfortably go, ensuring that you
reach the gumline.
Flossing Motion:
Vertical Strokes: Use 8 to 10 vertical strokes with
the floss to dislodge food particles and plaque. Move the floss up and
down against the sides of each tooth, making sure to clean both the
front and back surfaces.
C-Shaped Motion: For optimal cleaning, wrap the
floss around the tooth in a C-shape and gently slide it beneath the
gumline.
Frequency:
Daily Flossing: Aim to floss at least once a day.
Consistency is key to maintaining good oral hygiene.
Best Time to Floss: The most important time to
floss is before going to bed, as this helps remove debris and plaque
that can accumulate throughout the day.
Flossing and Brushing:
Order of Operations: Flossing can be done either
before or after brushing your teeth. Both methods are effective, so
choose the one that fits best into your routine.
EXOCRINE PANCREAS pathology
General Pathology
EXOCRINE PANCREAS
Congenital anomalies
1. Ectopic pancreatic tissue most commonly occurs in the stomach, duodenum, jejunum, Meckel's diverticulum, and ileum. It may be either asymptomatic or cause obstruction, bleeding, intussusception.
2.Annular pancreas is a ring of pancreatic tissue that encircle the duodenum and may cause duodenal obstruction.
Cystic fibrosis
Cystic fibrosis is a systemic disorder of exocrine gland secretion presenting during infancy or childhood.
Incidence is 1:2500 in Caucasians; it is less common in Black and extremely rare in Asians.
Pathogenesis. Cystic fibrosis shows autosomal recessive transmission; heterozygotes are unaffected. It results in a defective chloride channel, which leads to secretion of very thick mucus.
Characteristics
- Tissues other than exocrine glands are normal, and glands are structurally normal until damaged by cystic fibrosis.
- The only characteristic biochemical abnormalities are an elevation of sodium and chloride levels in sweat, and a decrease in water and bicarbonate secretion from pancreatic cells, resulting in a viscous secretion.
Clinical features
- Fifteen percent of cases present with meconium ileus.
- Most cases present during the first year with steatorrhea (with resultant deficiencies of vitamins A, D, E, and K), abdominal distention, and failure to thrive.
Complications are also related to pulmonary infections'and obstructive pulmonary disease as a result of viscous bronchial secretions.
Pathology
- There is mucus plugging of the pancreatic ducts with cystic dilatation, fibrous proliferation, and atrophy. Similar pathology develops in salivary glands.
- Lungs. Mucus impaction leads to bronchiolar dilatation an secondary infection.
- The gastrointestinal tract shows obstruction caused mucus impaction in the intestines with areas of biliary cirrhosis, resulting from intrahepatic bile duct obstruction
Diagnosis depends on demonstrating a "sweat test" abnomality associated with at least one clinical feature In sweat test, high levels of chloride are demonstrated.
Prognosis. Mean survival is age 20; mortality is most often due to pulmonary infections.
Degenerative changes
1. Iron pigmentation (e.g., from hemochromatosis) may be deposited within acinar and islet cells and may cause insulin deficiency.
2. Atrophy
a. Ischemic atrophy is due to atherosclerosis of pancreatic arteries and is usually asymptomatic.
b. Obstruction of pancreatic ducts affects only the exocrine pancreas, which becomes small, fibrous, and nodular.
Acute hemorrhagic pancreatitis
presents as a diffuse necrosis of the pancreas caused by the release of activated pancreatic
enzymes. Associated findings include fat necrosis and hemorrhage into the pancreas.
Incidence. This disorder is most often associated with alcoholism and biliary tract disease.
It affects middle-aged individuals and often occurs after a large meal or excessive alcohol ingestion; approximately 50% of patients have gallstones.
Pathogenesis. There are four theories.
- Obstruction of the pancreatic duct causes an elevated intraductal pressure, which results in leakage of enzymes from small ducts.
- obstruction may be caused by a gallstone at the ampulla of Vater; chronic alcohol ingestion may cause duct obstruction by edema.
- Hypercalcemia may cause activation of trypsinogen; its mechanism is unclear. Pancreatitis occurs in 20% of patients with hyperparathyroidism.
- Direct damage to acinar cells may occur by trauma, ischemia, viruses, and drugs.
- Hyperlipidemia may occur as a result of exogenous estrogen intake and alcohol ingestion.
Clinical features are typically the sudden onset of acute, continuous, and intense abdominal pain, often radiating to the back and accompanied by nausea, vomiting, and fever. This syndrome frequently results in shock.
Laboratory values reveal elevated amylase (lipase elevated after 3-4 days) and leukocytosis. Hypocalcemia is a poor prognostic sign.
Chronic pancreatitis
It refers to remitting and relapsing episodes of mild pancreatitis, causing progressive pancreatic damage.
Incidence is similar to acute pancreatitis. It is also seen in patients with ductal anomalies. Almost half the cases occur without known risk factors.
Pathogenesis is unclear; possibly, there is excess protein secretion by the pancreas, causing ductal obstruction.
Clinical features include flareups precipitated by alcohol and overeating, and drugs. Attacks are characterized by upper abdominal pain, tenderness, fever, and jaundice.
Laboratory values reveal elevated amylase and alkaline phosphatase, X-rays reveal calcifications in the pancreas. Chronic pancreatitis may result in pseudocyst formation, diabetes, and steatorrhea.
Carcinoma of the pancreas
Incidence:
Carcinoma of the pancreas accounts for approximately 5% of all cancer deaths. Increased risk is associated with smoking. high-fat diet, and chemical exposure. There is a higher incidence in the elderly, Blacks, males, and diabetics.
Clinical features
- The disease is usually asymptomatic until late in its course.
- Manifestations include weight loss, abdominal pain frequently radiating to the back, weakness, malaise, anorexia, depression, and ascites.
- There is jaundice in half of the patients who have carcinoma of the head of the pancreas.
- Courvoisier's law holds that painless jaundice with a palpable gallbladder is suggestive of pancreatic cancer.
Pathology
Carcinomas arise in ductal epithelium. Most are adenocarcinomas.
- Carcinoma of the head of the pancreas accounts for 60% of all pancreatic cancers.
- Carcinoma of the body (20%) and tail (5%) produce large indurated masses that spread widely to the liver and lymph nodes.
- In 15% of patients, carcinoma involves the pancreas diffusely.
Complications
include Trousseau's syndrome, a migratory thrombophlebitis that occurs in 10% of patients.
Prognosis is very poor. if resectable, the 5-year survival rate less than 5%. The usual course is rapid decline; on average death occurs 6 months after the onset of symptoms.
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.
Metabolism
Pharmacology
Metabolism
Hepatic Drug-Metabolizing Enzymes: most drug metabolism in the liverperformed by the hepatic microsomal enzyme system.
Therapeutic Consequences of Drug Metabolism
- Accelerated Renal Drug Excretion: The most important consequence of drug metabolism is the promotion of renal drug excretion. Metabolism makes it possible for the kidney to excrete many drugs that it otherwise could not.
- Drug Inactivation
- Increased Therapeutic Action: Metabolism may increase the effectiveness of some drugs.
- Activation of Prodrugs: A prodrug is a compound that is inactive when administered and made active by conversion in the body.
- Increased or Decreased Toxicity
Factors that influence rate of metabolism:
- Age: Hepatic maturation doesn't occur until about a year old.
- Induction of Drug-Metabolizing Enzymes: Some drugs can cause the rate of metabolism to increase, leading to the need for an increased dosage. May also influence the rate of metabolism for other drugs taken at the same time, leading to a need for increased dosages of those drugs as well.
- First-Pass Effect: Hepatic inactivation of certain oral drugs. Avoided by parentaral administration of drugs that undergo rapid hepatic metabolism.
- Nutritional Status
- Competition between Drugs