NEET MDS Synopsis
Organic Nitrates
Pharmacology
Organic Nitrates
Relax smooth muscle in blood vessel
Produces vasodilatation
– Decreases venous pressure and venous return to the heart Which decreases the cardiac work load and oxygen demand.
– May have little effect on the coronary arteries CAD causes stiffening and lack of
– responsiveness in the coronary arteries
– Dilate arterioles, lowering peripheral vascular resistance Reducing the cardiac workload
Main effect related to drop in blood pressure by
– Vasodilation- pools blood in veins and capillaries, decreasing the volume of blood that the heart has to pump around (the preload)
– relaxation of the vessels which decreases the resistance the heart has to pump against (the afterload)
Indications
- Myocardial ischemia
– Prevention
– Treatment
Nitroglycerin (Nitro-Bid)
• Used
– To relive acute angina pectoris
– Prevent exercise induced angina
– Decrease frequency and severity of acute anginal episodes
Type
• Oral - rapidly metabolized in the liver only small amount reaches circulation
• Sublingual – Transmucosal tablets and sprays
• Transdermal – Ointment s
– Adhesive discs applied to the skin
• IV preparations
Sublingual Nitroglycerine
• Absorbed directly into the systemic circulation, Acts within 1-3 minutes , Lasts 30-60 min
Topical Nitroglycerine
• Absorbed directly into systemic circulation, Absorption at a slower rate. , Longer duration of action
Ointment - effective for 4-8 hours
Transdermal disc - effective for 18-24 hours
Isosorbide dinitrate
• Reduces frequency and severity of acute anginal episodes
• Sublingual or chewable acts in 2 min. effects last 2-3 hours
• Orally, systemic effects in about 30 minutes and last about 4 hours after oral administration
Tolerance to Long-Acting Nitrates
• Long-acting dosage forms of nitrates may develop tolerance
– Result in episodes of chest pain
– Short acting nitrates less effective
Prevention of Tolerance
• Use long-acting forms for approximately 12-16 hours daily during active periods and omit them during inactive periods or sleep
• Oral or topical should be given every 6 hours X 3 doses allowing a rest period of 6 hours
Isosorbide dinitrate (Isordil, Sorbitrate) is used to reduce the frequency and severity of acute anginal episodes.
When given sublingually or in chewable tablets, it acts in about 2 minutes, and its effects last 2 to 3 hours. When higher doses are given orally, more drug escapes metabolism in the liver and produces systemic effects in approximately 30 minutes. Therapeutic effects last about 4 hours after oral administration
Isosorbide mononitrate (Ismo, Imdur) is the metabolite and active component of isosorbide dinitrate. It is well absorbed after oral administration and almost 100% bioavailable. Unlike other oral nitrates, this drug is not subject to first-pass hepatic metabolism. Onset of action occurs within 1 hour, peak effects occur between 1 and 4 hours, and the elimination half-life is approximately 5 hours. It is used only for prophylaxis of angina; it does not act rapidly enough to relieve acute attacks.
Nerves of the Tongue
Anatomy
Anterior 2/3 of tongue
Posterior 1/3 of tongue
Motor Innervation
All muscles by hypoglossal nerve (CN XII) except palatoglossus muscle (by the pharyngeal plexus)
General Sensory Innervation
Lingual nerve (branch of mandibular nerve CN V3)
Glossopharyngeal nerve (CN IX)
Special Sensory Innervation
Chorda tympani nerve (branch of facial nerve)
Glossopharyngeal nerve (CN IX)
Neuron Basic Structure
Pharmacology
Neuron Basic Structure (How brain cells communicate)
• Synapse:A junction between the terminal button of an axon and the membrane of another neuron
• Terminal button(orbouton):The bud at the end of a branch of an axon; forms synapses with another neuron; sends information to that neuron.
• Neurotransmitter:A chemical that is released by a terminal button; has an excitatory or inhibitory effect on another neuron.
Different types of Synapses
1-Axo-denrdritic
2-Axo-axonal
3-Axo-somatic
Chemical transmission in the CNS
The CNS controls the main functions of the body through the action endogenous chemical substances known as “neurotransmitters”.
These neurotransmitters are stored in and secreted by neurons to “transmit”information to the postsynaptic sites producing either excitatoryor inhibitory responses.
Most centrally acting drugs exert their actions at the synaptic junctions by either affecting neurotransmitter synthesis, release, uptake, or by exerting direct agonistor antagonistaction on postsynaptic sites.
Rheumatic Fever - Major and Minor Criteria
Medicine
Rheumatic fever occurs after a streptococcal infection (usually caused by Group A Beta-Hemolytic Strep (GABHS)).
It is an inflammatory condition that affects the joints, skin, heart and brain.
Major criteria are referred to as Jones criteria
J – Joint involvement which is usually migratory and inflammatory joint involvement that starts in the lower joints and ascends to upper joints
O – (“O” Looks like heart shape) – indicating that patients can develop myocarditis or inflammation of the heart
N – Nodules that are subcutaneous
E – Erythema marginatum which is a rash of ring-like lesions that can start in the trunk or arms. When joined with other rings, it can create a snake-like appearance
S – Sydenham chorea is a late feature which is characterized by jerky, uncontrollable, and purposeless movements resembling twitches
Minor criteria include
C – CRP Increased
A – Arthralgia
F – Fever
E – Elevated ESR
P – Prolonged PR Interval
A – Anamesis
L – Leukocytosis
Diagnosis of rheumatic fever is made after a strep infection (indicated by either throat cultures growing GABHS OR elevated anti-streptolysin O titers in the blood) and:
Two major criteria OR
One major criterion and two minor criteria
Multiple sclerosis
General Pathology
Multiple sclerosis
a. A demyelinating disease that primarily affects myelin (i.e. white matter). This affects the conduction of electrical impulses along the axons of nerves. Areas of demyelination are known as plaques.
b. The most common demyelinating disease.
c. Onset of disease usually occurs between ages 20 and 50; slightly more common in women.
d. Disease can affect any neuron in the central nervous system, including the brainstem and spinal cord. The optic nerve (vision) is commonly affected.
Autopsy
General Pathology
Autopsy
Autopsy is examination of the dead body to identify the cause of death. This can be for forensic or clinical purposes.
Plate Fixation Techniques
Oral and Maxillofacial SurgeryManagement of Mandibular Fractures: Plate Fixation Techniques
The management of mandibular fractures involves various techniques for
fixation, depending on the type and location of the fracture. .
1. Plate Placement in the Body of the Mandible
Single Plate Fixation:
A single plate is recommended to be placed just below the apices of
the teeth but above the inferior alveolar nerve canal. This positioning
helps to avoid damage to the nerve while providing adequate support to
the fracture site.
Miniplate Fixation: Effective for non-displaced or
minimally displaced fractures, provided the fracture is not severely
comminuted. The miniplate should be placed at the superior border of the
mandible, acting as a tension band that prevents distraction at the
superior border while maintaining compression at the inferior border
during function.
Additional Plates:
While a solitary plate can provide adequate rigidity, the placement
of an additional plate or the use of multi-armed plates (Y or H plates)
can enhance stability, especially in more complex fractures.
2. Plate Placement in the Parasymphyseal and Symphyseal Regions
Two Plates for Stability:
In the parasymphyseal and symphyseal regions, two plates are
recommended due to the torsional forces generated during function.
First Plate: Placed at the inferior aspect of
the mandible.
Second Plate: Placed parallel and at least 5 mm
superior to the first plate (subapical).
Plate Placement Behind the Mental Foramen:
A plate can be fixed in the subapical area and another near the
lower border. Additionally, plates can be placed on the external oblique
ridge or parallel to the lower border of the mandible.
3. Management of Comminuted or Grossly Displaced Fractures
Reconstruction Plates:
Comminuted or grossly displaced fractures of the mandibular body
require fixation with a locking reconstruction plate or a standard
reconstruction plate. These plates provide the necessary stability for
complex fractures.
4. Management of Mandibular Angle Fractures
Miniplate Fixation:
When treating mandibular angle fractures, the plate should be placed
at the superolateral aspect of the mandible, extending onto the broad
surface of the external oblique ridge. This placement helps to
counteract the forces acting on the angle of the mandible.
5. Stress Patterns and Plate Design
Stress Patterns:
The zone of compression is located at the superior border of the
mandible, while the neutral axis is approximately at the level of the
inferior alveolar canal. Understanding these stress patterns is crucial
for optimal plate placement.
Miniplate Characteristics:
Developed by Michelet et al. and popularized by Champy et al.,
miniplates utilize monocortical screws and require a minimum of two
screws in each osseous segment. They are smaller than standard plates,
allowing for smaller incisions and less soft tissue dissection, which
reduces the risk of complications.
6. Other Fixation Techniques
Compression Osteosynthesis:
Indicated for non-oblique fractures that demonstrate good body
opposition after reduction. Compression plates, such as dynamic
compression plates (DCP), are used to achieve this. The inclined plate
within the hole allows for translation of the bone toward the fracture
site as the screw is tightened.
Fixation Osteosynthesis:
For severely oblique fractures, comminuted fractures, and fractures
with bone loss, compression plates are contraindicated. In these cases,
non-compression osteosynthesis using locking plates or reconstruction
plates is preferred. This method is also suitable for patients with
questionable postoperative compliance or a non-stable mandible.
CAD/CAM Restorations
Dental Materials
CAD/CAM Restorations
Applications-inlays, onlays, veneers, crowns, bridges, implants, and implant prostheses
Stages of fabrication
CSD-computerized surface digitization
CAD-computer-aided (assisted) design
CAM-computer-aided (assisted) machining
CAE-computer-aided esthetics (currently theoretic)
CAF-computer-aided finishing or polishing (which are currently theoretic steps)
Classification
Chairside or in-office systems
(1) Cerec (Siemens system)-inlays, onlays, veneers
(2) Sopha (Duret system)-inlays, onlays (and Crowns)
Laboratory systems
(1) DentiCAD (Rekow system)-inlay, onlays, veneers, crowns
(2) Cicero (Elephant system)-porcelain fused-to-metal crowns
Materials
a. Feldspathic oorcelains (Vita)
b. Machinable ceramics (Dicor MGC)
c. Metal alloys limited use)
Cementing
- Etching enamel and/or dentin for micromechanical retention
- Bonding agent for retention to etched surface
- Composite as a luting cement for reacting chemically with bonding agent and with silanated surface of restoration
- Silane for bonding to etched ceramic (or metal) restorations and to provide chemical reaction
- Hydrofluoric acid etching to create spaces for micromechanical retention on surface or restoration
Properties
1. Physical properties
a. Thermal expansion coefficient well matched to tooth structure
b. Good resistance to plaque adsorption or retention
2. Chemical properties-not resistant to acids and should be protected from APF
3. Mechanical properties
a. Excellent wear resistance (but may abrade opponent teeth)
b. Some wear of luting cements but self-limiting
c. Excellent toothbrush abrasion
4. Biologic properties-excellent properties