NEET MDS Synopsis
The Meatus of the Nose
AnatomyThe Meatus of the Nose
Sphenopalatine Recess
This space is posterosuperior to the superior concha.
The sphenoidal sinus opens into this recess.
Superior Meatus
This is a narrow passageway between the superior and middle nasal conchae.
The posterior ethmoidal sinuses open into it by one or more orifices.
Middle Meatus
This is longer and wider than the superior one.
The anterosuperior part of this meatus lead into a funnel-shaped opening, called the infundibulum, through which the frontonasal duct leads to the frontal sinus.
There is one duct for each frontal sinus and since there may be several, there may be several frontonasal ducts.
When the middle concha is removed, rounded elevation called the ethmoidal bulla (L. bubble), is visible
The middle ethmoidal air cells open on the surface of the ethmoidal bulla.
Inferior to this bulla is a semicircular groove called the hiatus semilunaris.
The frontal sinus opens into this hiatus anterosuperiorly.
Near the hiatus are the openings of the anterior ethmoid air cells.
The maxillary sinus also opens into the middle meatus.
Inferior Meatus
This is a horizontal passage, inferolateral to the inferior nasal concha.
The nasolacrimal duct opens into the anterior part of this meatus.
Usually, the orifice of this duct is wide and circular.
Ether (diethylether)
Pharmacology
Ether (diethylether)
Ether (diethylether) MAC 2.0%, Blood/gas solubility ratio 15
- Ether is generally mixed with 3% ethanol to retard oxidation. Peroxides form on exposure to air and can enhance the danger of an explosion.
- Slow rate of induction and recovery due to its high blood/gas solubility ratio.
- Produces profound muscular relaxation.
- Both the rate and the minute volume of ventilation tend to be elevated during the inhalation of ether.
- Ether maintains good circulatory stability and does not sensitize the heart to the arrhythmogenic action of catecholamines.
- More than 90% of the absorbed ether can be recovered unchanged in the expired air. Metabolism is not extensive and the metabolites are not hepatotoxic.
- Ether is a versatile anesthetic of unexcelled safety, but it is flammable and irritating to breathe. Secretions can be blocked with anticholinergics.
Lip habits
OrthodonticsLip habits refer to various behaviors involving the lips
that can affect oral health, facial aesthetics, and dental alignment. These
habits can include lip biting, lip sucking, lip licking, and lip pursing. While
some lip habits may be benign, others can lead to dental and orthodontic issues
if they persist over time.
Common Types of Lip Habits
Lip Biting:
Description: Involves the habitual biting of the
lips, which can lead to chapped, sore, or damaged lips.
Causes: Often associated with stress, anxiety, or
nervousness. It can also be a response to boredom or concentration.
Lip Sucking:
Description: The act of sucking on the lips,
similar to thumb sucking, which can lead to changes in dental alignment.
Causes: Often seen in young children as a
self-soothing mechanism. It can also occur in response to anxiety or
stress.
Lip Licking:
Description: Habitual licking of the lips, which
can lead to dryness and irritation.
Causes: Often a response to dry lips or a habit
formed during stressful situations.
Lip Pursing:
Description: The act of tightly pressing the lips
together, which can lead to muscle tension and discomfort.
Causes: Often associated with anxiety or
concentration.
Etiology of Lip Habits
Psychological Factors: Many lip habits are linked to
emotional states such as stress, anxiety, or boredom. Children may develop
these habits as coping mechanisms.
Oral Environment: Factors such as dry lips, dental
issues, or malocclusion can contribute to the development of lip habits.
Developmental Factors: Young children may engage in lip
habits as part of their exploration of their bodies and the world around
them.
Clinical Features
Dental Effects:
Malocclusion: Prolonged lip habits can lead to
changes in dental alignment, including open bites, overbites, or other
malocclusions.
Tooth Wear: Lip biting can lead to wear on the
incisal edges of the teeth.
Gum Recession: Chronic lip habits may contribute to
gum recession or irritation.
Soft Tissue Changes:
Chapped or Cracked Lips: Frequent lip licking or
biting can lead to dry, chapped, or cracked lips.
Calluses: In some cases, calluses may develop on
the lips due to repeated biting or sucking.
Facial Aesthetics:
Changes in Lip Shape: Prolonged habits can lead to
changes in the shape and appearance of the lips.
Facial Muscle Tension: Lip habits may contribute to
muscle tension in the face, leading to discomfort or changes in facial
expression.
Management
Behavioral Modification:
Awareness Training: Educating the individual about
their lip habits and encouraging them to become aware of when they
occur.
Positive Reinforcement: Encouraging the individual
to replace the habit with a more positive behavior, such as using lip
balm for dry lips.
Psychological Support:
Counseling: For individuals whose lip habits are
linked to anxiety or stress, counseling or therapy may be beneficial.
Relaxation Techniques: Teaching relaxation
techniques to help manage stress and reduce the urge to engage in lip
habits.
Oral Appliances:
In some cases, orthodontic appliances may be used to discourage lip
habits, particularly if they are leading to malocclusion or other dental
issues.
Dental Care:
Regular Check-Ups: Regular dental visits can help
monitor the effects of lip habits on oral health and provide guidance on
management.
Treatment of Dental Issues: Addressing any
underlying dental problems, such as cavities or misalignment, can help
reduce the urge to engage in lip habits.
Infectious Mononucleosis
General Pathology
Infectious Mononucleosis
It is an Epstein Barr virus infection in children and young adults.
Features
-Constitutional symptoms.
-Sore throat.
-Lymphnode enlargement.
-Skin rashes
-Jaundice.
-Rarely pneumonia, meningitis and encephalitis.
Blood Picture
- Total count of I0,000. 20,000 /cu.mm.
- Lymphocytosis (50-90%) with atypical forms. They are larger with more cytoplasm which may be vacuolated or basophilic. Nucleus may be indented. with nucleoli (Downy type I to III).
- Platelets may be reduced.
- Paul Bunell test (for heterophil antibody against sheep RBC) is positive
Enzyme Kinetics
Biochemistry
Enzyme Kinetics
Enzymes are protein catalysts that, like all catalysts, speed up the rate of a chemical reaction without being used up in the process. They achieve their effect by temporarily binding to the substrate and, in doing so, lowering the activation energy needed to convert it to a product.
The rate at which an enzyme works is influenced by several factors, e.g.,
the concentration of substrate molecules (the more of them available, the quicker the enzyme molecules collide and bind with them). The concentration of substrate is designated [S] and is expressed in unit of molarity.
the temperature. As the temperature rises, molecular motion - and hence collisions between enzyme and substrate - speed up. But as enzymes are proteins, there is an upper limit beyond which the enzyme becomes denatured and ineffective.
the presence of inhibitors.
competitive inhibitors are molecules that bind to the same site as the substrate - preventing the substrate from binding as they do so - but are not changed by the enzyme.
noncompetitive inhibitors are molecules that bind to some other site on the enzyme reducing its catalytic power.
pH. The conformation of a protein is influenced by pH and as enzyme activity is crucially dependent on its conformation, its activity is likewise affected.
The study of the rate at which an enzyme works is called enzyme kinetics.
Weine Classification
Endodontics
Weine Classification
The Weine classification divides root canal systems into three main categories:
The pulp canal system is complex, and it may branch, divide, and rejoin.
Weine categorized the root canal systems in any root
into four basic types. Others, using cleared teeth in which the root canal
systems had been stained with hematoxylin dye, found a
much more complex canal system. They identified eight pulp space
configurations, that can be briefly described as following :
Type I : A single canal extends from the pulp chamber to the apex (1).
Type II: Two separate canals leave the pulp chamber and join short of the
apex to form one canal (2-1).
Type III: One canal leaves the pulp chamber and divides into two in the root;
the two then merge to exit as one canal (1-2-1).
Type IV: Two separate, distinct canals extend from the pulp chamber to the
apex (2).
Type V: One canal leaves the pulp chamber and divides short of the apex into
two separate, distinct canals with separate apical foramina (1-2).
Type VI: Two separate canals leave the pulp chamber, merge into the body of
the root, and redivide short of the apex to exit as two distinct canals (2-1-2).
Type VII: One canal leaves the pulp chamber, divides and then rejoins in the
body of the root, and finally redivides into two distinct canals short of the apex (1-2-1-2).
Type VIII: Three separate, distinct canals extend from the pulp chamber to
the apex (3).
INNERVATION OF THE DENTIN-PULP COMPLEX
Dental Anatomy
INNERVATION OF THE DENTIN-PULP COMPLEX
Dentine Pulp
Dentin
Nerve Fibre Bundle
Nerve fibres
The nerve bundles entering the tooth pulp consist principally of sensory afferent fibers from the trigeminal nerve and sympathetic branches from the superior cervical ganglion. There are non-myelinated (C fibers) and myelinated (less than non, A-delta, A-beta) fibers. Some nerve endings terminate on or in association with the odontoblasts and others in the predentinal tubules of the crown. Few fibers are found among odontoblasts of the root.
In the cell-free zone one can find the plexus of Raschkow.
Cutting Edge Mechanics
Conservative DentistryCutting Edge Mechanics
Edge Angles and Their Importance
Edge Angle: The angle formed at the cutting edge of a
bur blade. Increasing the edge angle reinforces the cutting edge, which
helps to reduce the likelihood of blade fracture during use.
Reinforcement: A larger edge angle provides more
material at the cutting edge, enhancing its strength and durability.
Carbide vs. Steel Burs
Carbide Burs:
Hardness and Wear Resistance: Carbide burs are
known for their higher hardness and wear resistance compared to steel
burs. This makes them suitable for cutting through hard dental tissues.
Brittleness: However, carbide burs are more brittle
than steel burs, which means they are more prone to fracture if not
designed properly.
Edge Angles: To minimize the risk of fractures,
carbide burs require greater edge angles. This design consideration is
crucial for maintaining the integrity of the bur during clinical
procedures.
Interdependence of Angles
Three Angles: The cutting edge of a bur is defined by
three angles: the edge angle, the clearance angle, and the rake angle. These
angles cannot be varied independently of each other.
Clearance Angle: An increase in the clearance angle
(the angle between the cutting edge and the surface being cut) results
in a decrease in the edge angle. This relationship is important for
optimizing cutting efficiency and minimizing wear on the bur.