NEET MDS Synopsis
Opiate Antagonists
Pharmacology
Opiate Antagonists
Opiate antagonists have no agonist properties. They are utilized to reverse opiate induced respiratory depression and to prevent drug abuse.
A. Naloxone
Pure opiate antagonist , Short duration of action, Only 1/50th as potent orally as parenterally
B. Naltrexone
Pure opiate antagonist, Long duration of action, Better oral efficacy
Cells, cytoplasm, and organelles
PhysiologyCells, cytoplasm, and organelles:
Cytoplasm consists of a gelatinous solution and contains microtubules (which serve as a cell's cytoskeleton) and organelles
Cells also contain a nucleus within which is found DNA (deoxyribonucleic acid) in the form of chromosomes plus nucleoli (within which ribosomes are formed)
Organelles include:
Endoplasmic reticulum : 2 forms: smooth and rough; the surface of rough ER is coated with ribosomes; the surface of smooth ER is not , Functions include: mechanical support, synthesis (especially proteins by rough ER), and transport
Golgi complex consists of a series of flattened sacs (or cisternae) functions include: synthesis (of substances likes phospholipids), packaging of materials for transport (in vesicles), and production of lysosomes
Lysosome : membrane-enclosed spheres that contain powerful digestive enzymes , functions include destruction of damaged cells & digestion of phagocytosed materials
Mitochondria : have double-membrane: outer membrane & highly convoluted inner membrane
inner membrane has folds or shelf-like structures called cristae that contain elementary particles; these particles contain enzymes important in ATP production
primary function is production of adenosine triphosphate (ATP)
Ribosome-:composed of rRNA (ribosomal RNA) & protein , primary function is to produce proteins
Centrioles :paired cylindrical structures located near the nucleas , play an important role in cell division
Flagella & cilia - hair-like projections from some human cells
cilia are relatively short & numerous (e.g., those lining trachea)
a flagellum is relatively long and there's typically just one (e.g., sperm)
Villi Projections of cell membrane that serve to increase surface area of a cell (which is important, for example, for cells that line the intestine)
Dental Cavity Preparation
Conservative DentistryConcepts in Dental Cavity Preparation and Restoration
In operative dentistry, understanding the anatomy of tooth preparations and
the techniques used for effective restorations is crucial. The
importance of wall convergence in Class I amalgam restorations, the use of
dental floss with retainers, and specific considerations for preparing
mandibular first premolars.
1. Pulpal Wall and Axial Wall
Pulpal Wall
Definition: The pulpal wall is an external wall of a
cavity preparation that is perpendicular to both the long axis of the tooth
and the occlusal surface of the pulp. It serves as a boundary for the pulp
chamber.
Function: This wall is critical in protecting the pulp
from external irritants and ensuring the integrity of the tooth structure
during restorative procedures.
Axial Wall
Transition: Once the pulp has been removed, the pulpal
wall becomes the axial wall.
Definition: The axial wall is an internal wall that is
parallel to the long axis of the tooth. It plays a significant role in the
retention and stability of the restoration.
2. Wall Convergence in Class I Amalgam Restorations
Facial and Lingual Walls
Convergence: In Class I amalgam restorations, the
facial and lingual walls should always be made slightly occlusally
convergent.
Importance:
Retention: Slight convergence helps in retaining
the amalgam restoration by providing a mechanical interlock.
Prevention of Dislodgement: This design minimizes
the risk of dislodgement of the restoration during functional loading.
Clinical Implications
Preparation Technique: When preparing a Class I cavity,
clinicians should ensure that the facial and lingual walls are slightly
angled towards the occlusal surface, promoting effective retention of the
amalgam.
3. Use of Dental Floss with Retainers
Retainer Safety
Bow of the Retainer: The bow of the retainer should be
tied with approximately 12 inches of dental floss.
Purpose:
Retrieval: The floss allows for easy retrieval of
the retainer or any broken parts if they are accidentally swallowed or
aspirated by the patient.
Patient Safety: This precaution enhances patient
safety during dental procedures, particularly when using matrix
retainers for restorations.
Clinical Practice
Implementation: Dental professionals should routinely
tie dental floss to retainers as a standard safety measure, ensuring that it
is easily accessible in case of an emergency.
4. Pulpal Wall Considerations in Mandibular First Premolars
Anatomy of the Mandibular First Premolar
Pulpal Wall Orientation: The pulpal wall of the
mandibular first premolar declines lingually. This anatomical feature is
important to consider during cavity preparation.
Pulp Horn Location:
The facial pulp horn is prominent and located at a higher level than
the lingual pulp horn. This asymmetry necessitates careful attention
during preparation to avoid pulp exposure.
Bur Positioning
Tilting the Bur: When preparing the cavity, the bur
should be tilted lingually to prevent exposure of the facial pulp horn.
Technique: This technique helps ensure that the
preparation is adequately shaped while protecting the pulp from inadvertent
injury.
Eosinopenia
General Pathology
Eosinopenia:
Causes
-Corticoid effect (Cushing's syndrome or therapy).
-Stress.
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.
Nitrous Oxide
Anaesthesia
Pharmacodynamics of Nitrous Oxide
Overview
Nitrous oxide (N2O), commonly known as "laughing gas," is an inhalational
anesthetic used primarily for its analgesic and anxiolytic properties.
Understanding its pharmacodynamics is crucial for safe and effective use in
clinical settings.
Pharmacodynamics
CNS Depression:
Nitrous oxide produces nonspecific central nervous system (CNS)
depression.
While it is classified as an inhalational general anesthetic, it
provides limited analgesia, making surgical anesthesia unlikely unless
concentrations that produce anoxia are reached.
Potency:
Nitrous oxide is the weakest of all inhalation agents, with a minimum
alveolar concentration (MAC) of approximately 105%.
The MAC is a measure of the potency of an inhalation agent, defined as
the concentration required to produce immobility in 50% of patients in
response to a surgical stimulus.
Effects at Various Concentrations:
30% to 50% Concentration:
Produces a relaxed, somnolent patient who may appear dissociated and
is easily susceptible to suggestion.
Some patients may experience amnesia, but there is typically little
alteration in learning or memory.
Greater than 60% Concentration:
Patients may experience discoordination, ataxia, giddiness, and
increased sleepiness.
It is recommended that the concentration of nitrous oxide should not
routinely exceed 50% to avoid adverse effects.
Titration:
One of the advantages of nitrous oxide is its ability to be easily
titrated.
It can be increased for stimulating procedures (e.g., injections) and
decreased during less stimulating periods (e.g., restorations).
Physiological Considerations
Entrapment in Gas-Filled Spaces:
Nitrous oxide can become entrapped in gas-filled spaces such as the
middle ear, sinuses, and gastrointestinal tract.
This can lead to increased middle ear pressure, which is generally
insignificant in patients with normal Eustachian tube function but can
induce pain in patients with acute otitis media.
Contraindications:
Acute Otitis Media: Use should be avoided in patients with this
condition due to the risk of increased middle ear pressure and pain.
Severe Behavioral Problems and Emotional Illness: Patients who
are uncooperative or have a fear of "gas" may not tolerate nitrous oxide
well.
Claustrophobia: Patients with this condition may feel
uncomfortable with the nasal hood placement.
Maxillofacial Deformities: Conditions that prevent proper
placement of the nasal hood can contraindicate its use.
Nasal Obstruction: Conditions such as upper respiratory
infections, nasal polyps, or a deviated septum can hinder effective
administration.
Chronic Obstructive Pulmonary Disease (COPD): Patients with
COPD may have difficulty with nitrous oxide due to respiratory issues.
Pregnancy: Caution is advised when using nitrous oxide in
pregnant patients.
High Oxygenation Situations: Situations where high oxygenation
is inadvisable, such as during Bleomycin therapy, contraindicate the use
of nitrous oxide.
Casting of glass or ceramic
Dental Materials
Casting of glass or ceramic
A castable ceramic is prepared in a similar manner as metal cast preparation .
Glass is heated to 1360 degrees & then cast.
Phosphate bonded investments are used for this purpose .
Hypoxia
PhysiologyHypoxia
Hypoxia is tissue oxygen deficiency
Brain is the most sensitive tissue to hypoxia: complete lack of oxygen can cause unconsciousness in 15 sec and irreversible damage within 2 min.
Oxygen delivery and use can be interrupted at several sites
Type of
Hypoxia
O2 Uptake
in Lungs
Hemoglobin
Circulation
Tissue O2 Utilization
Hypoxic
Low
Normal
Normal
Normal
Anemic
Normal
Low
Normal
Normal
Ischemic
Normal
Normal
Low
Normal
Histotoxic
Normal
Normal
Normal
Low
Causes:
Hypoxic: high altitude, pulmonary edema, hypoventilation, emphysema, collapsed lung
Anemic: iron deficiency, hemoglobin mutations, carbon monoxide poisoning
Ischemic: shock, heart failure, embolism
Histotoxic: cyanide poisoning (inhibits mitochondria)
Carbon monoxide (CO) poisoning:
CO binds to the same heme Fe atoms that O2 binds to
CO displaces oxygen from hemoglobin because it has a 200X greater affinity for hemoglobin.
Treatment for CO poisoning: move victim to fresh air. Breathing pure O2 can give faster removal of CO
Cyanide poisoning:
Cyanide inhibits the cytochrome oxidase enzyme of mitochondria
Two step treatment for cyanide poisoning:
1) Give nitrites
Nitrites convert some hemoglobin to methemoglobin. Methemoglobin pulls cyanide away from mitochondria.
2) Give thiosulfate.
Thiosulfate converts the cyanide to less poisonous thiocyanate.