NEET MDS Synopsis
Inlay Preparation
Conservative DentistryInlay Preparation
Inlay preparations are a common restorative procedure in dentistry,
particularly for Class II restorations.
1. Definitions
A. Inlay
An inlay is a restoration that is
fabricated using an indirect procedure. It involves one or more tooth
surfaces and may cap one or more cusps but does not cover all cusps.
2. Class II Inlay (Cast Metal) Preparation Procedure
A. Burs Used
Recommended Burs:
No. 271: For initial cavity preparation.
No. 169 L: For refining the cavity shape and creating the proximal
box.
B. Initial Cavity Preparation
Similar to Class II Amalgam: The initial cavity
preparation is performed similarly to that for Class II amalgam
restorations, with the following differences:
Occlusal Entry Cut Depth: The initial occlusal
entry should be approximately 1.5 mm deep.
Cavity Margins Divergence: All cavity margins must
diverge occlusally by 2-5 degrees:
2 degrees: When the vertical walls of the
cavity are short.
5 degrees: When the vertical walls are long.
Proximal Box Margins: The proximal box margins
should clear the adjacent tooth by 0.2-0.5 mm, with 0.5 ± 0.2 mm being
ideal.
C. Preparation of Bevels and Flares
Primary and Secondary Flares:
Flares are created on the facial and lingual proximal walls, forming
the walls in two planes.
The secondary flare widens the proximal box, which initially had a
clearance of 0.5 mm from the adjacent tooth. This results in:
Marginal Metal in Embrasure Area: Placing the
marginal metal in the embrasure area allows for better
self-cleansing and easier access for cleaning and polishing without
excessive dentin removal.
Marginal Metal Angle: A 40-degree angle, which
is easily burnishable and strong.
Enamel Margin Angle: A 140-degree angle, which
blunts the enamel margin and increases its strength.
Note: Secondary flares are omitted on the
mesiofacial proximal walls of maxillary premolars and first molars for
esthetic reasons.
D. Gingival Bevels
Width: Gingival bevels should be 0.5-1 mm wide and
blend with the secondary flare, resulting in a marginal metal angle of 30
degrees.
Purpose:
Removal of weak enamel.
Creation of a burnishable 30-degree marginal metal.
Production of a lap sliding fit at the gingival margin.
E. Occlusal Bevels
Location: Present on the cavosurface margins of the
cavity on the occlusal surface.
Width: Approximately 1/4th the depth of the respective
wall, resulting in a marginal metal angle of 40 degrees.
3. Capping Cusps
A. Indications
Cusp Involvement: Capping cusps is indicated when more
than 1/2 of a cusp is involved and is mandatory when 2/3 or more is
involved.
B. Advantages
Weak Enamel Removal: Helps in removing weak enamel.
Cavity Margin Location: Moves the cavity margin away
from occlusal areas subjected to heavy forces.
Visualization of Caries: Aids in visualizing the extent
of caries, increasing convenience during preparation.
C. Cusp Reduction
Uniform Metal Thickness: Cusp reduction must provide
for a uniform 1.5 mm metal thickness over the reduced cusps.
Facial Cusp Reduction: For maxillary premolars and
first molars, the reduction of the facial cusp should be 0.75-1 mm for
esthetic reasons.
D. Reverse Bevel (Counter Bevel)
Definition: A bevel given on the margins of the reduced
cusp.
Width: Varies to extend beyond any occlusal contact
with opposing teeth, resulting in a marginal metal angle of 30 degrees.
E. Retention Considerations
Retention Form: Cusp reduction decreases the retention
form due to reduced vertical wall height. Therefore, proximal retentive
grooves are usually recommended.
Collar and Skirt Features: These features can enhance
retention and resistance form.
Urinary tract infection
General Pathology
Urinary tract infection
Most often caused by gram-negative, rod-shaped bacteria that are normal residents of the enteric tract, especially Escherichia coli.
Clinical manifestations:
frequent urination, dysuria, pyuria (increased PMNs), hematuria, and bacteriuria.
May lead to infection of the urinary bladder (cystitis) or kidney (pyelonephritis).
Articulations and Movement
Anatomy
Articulations
Classified according to their structure, composition,and movability
• Fibrous joints-surfaces of bones almost in direct contact with limited movement
o Syndesmosis-two bones united by interosseous ligaments
o Sutures-serrated margins of bones united by a thin layer of fibrous tissue
o Gomphosis-insertion of a cone-shaped process into a socket
• Cartilaginous joints-no joint cavity and contiguous bones united by cartilage
o Synchondrosis-ends of two bones approximated by hyaline cartilage
o Symphyses-approximating bone surfaces connected by fibrocartilage
• Synovial joints-approximating bone surfaces covered with cartilage; may be separated by a disk; attached by ligaments
o Hinge-permits motion in one plane only
o Pivot-permits rotary movement in which a ring rotates around a central axis
o Saddle-opposing surfaces are convexconcave. allowing great freedom of motion
o Ball and socket - capable of movement in an infinite number of axes; rounded head of one bone moves in a cuplike cavity of the approximating bone
Bursae
• Sacs filled with synovial fluid that are present where tendons rub against bone or where skjn rubs across bone
• Some bursae communicate with a joint cavity
• Prominent bursae found at the elbow. hip, and knee'
Movements
• Gliding
o Simplest kind of motion in a joint
o Movement on a joint that does not involve any angular or rotary motions
• Flexion-decreases the angle formed by the union of two bones
• Extension-increases the angle formed by the union of two bones
• Abduction-occurs by moving part of the appendicular skeleton away from the median plane of the body
• Adduction-occurs by moving part of the appendicular skeleton toward the median plane of the body
• Circumduction
o Occurs in ball-and-socket joints
o Circumscribes the conic space of one bone by the other bone
• Rotation-turning on an axis without being displaced from that axis
Hormones of the Pituitary -The Posterior Lobe
Physiology
The Posterior Lobe
The posterior lobe of the pituitary releases two hormones, both synthesized in the hypothalamus, into the circulation.
Antidiuretic Hormone (ADH).
ADH is a peptide of 9 amino acids. It is also known as arginine vasopressin. ADH acts on the collecting ducts of the kidney to facilitate the reabsorption of water into the blood.
A deficiency of ADH
leads to excessive loss of urine, a condition known as diabetes nsipidus.
Oxytocin
Oxytocin is a peptide of 9 amino acids. Its principal actions are:
stimulating contractions of the uterus at the time of birth
stimulating release of milk when the baby begins to suckle
Spinal Anaesthesia
AnaesthesiaSpinal Anesthesia
A. Anatomy
Spinal anesthesia targets the spinal cord, which arises from the foramen magnum
and extends to the conus medullaris, typically ending around the third lumbar
vertebrae (L3) in adults. The spinal column is protected by three layers: the
dura mater, arachnoid mater, and pia mater. The subarachnoid space, where the
spinal anesthetic is administered, contains cerebrospinal fluid (CSF), spinal
nerves, and the arachnoid and pial vessels. The arachnoid membrane provides
significant resistance to drug diffusion, accounting for approximately 90% of
the barrier.
The epidural space lies outside the dura mater and is bounded by the ligamentum
flavum, lamina, and spinous processes. It is important to distinguish between
the epidural and subarachnoid spaces, as the needle placement determines the
type of anesthesia administered.
Key anatomic landmarks for spinal anesthesia include the iliac crests, which can
be used to approximate the L4-L5 interspace. The spinal needle is commonly
inserted at the L3 or L4 level in adults to avoid the termination of the spinal
cord.
B. Indications
1. Lower abdominal and pelvic surgeries: Spinal anesthesia is suitable for
surgeries below the umbilicus, such as hernia repairs, gynecological and
urological procedures.
2. Lower extremity surgeries: This includes orthopedic procedures and lower limb
surgeries.
3. Cesarean sections: It provides adequate analgesia and muscle relaxation while
allowing the mother to remain awake and participate in the birth.
C. Contraindications
Absolute contraindications:
1. Patient refusal or inability to cooperate and maintain a still position.
2. Coagulation disorders or use of anticoagulants, which increase the risk of
spinal hematoma.
3. Local infection at the injection site.
Relative contraindications:
1. Sepsis: Due to the risk of spreading infection to the central nervous system.
2. Neurological conditions: Such as myelitis, which can be exacerbated by
invasive procedures.
3. Intracranial hypertension: As spinal anesthesia can cause a sudden drop in
systemic vascular resistance and increase intracranial pressure.
4. Severe spinal or spinal cord deformities: These may lead to complications in
needle placement and drug distribution.
5. Cardiovascular conditions: Stenotic heart valve lesions and severe
hypertrophic cardiomyopathy can be poorly tolerated due to the hemodynamic
changes associated with spinal anesthesia.
6. Lack of anesthesiologist experience: This may increase the risk of
complications.
D. Equipment
1. Patient monitors: ECG for heart rhythm monitoring, pulse oximeter for oxygen
saturation, and a blood pressure cuff to assess circulation.
2. Resuscitation equipment: Oxygen supply, bag and mask for ventilation, and
suction to clear the airway if needed.
3. Sterile environment: Sterile gloves, mask, gown (if required), and a clean
field are essential to prevent infection.
4. Intravenous access: To administer fluids and medications during the
procedure.
5. Sterile prep solution: Typically Betadine or a non-iodine alternative for
skin preparation.
6. Spinal needle: Small gauge (24-26 gauge) for minimizing trauma.
7. Sterile drapes: To maintain the sterility of the area.
8. Local anesthetic: For skin infiltration to reduce pain during the spinal
block.
9. Syringes: A small syringe for local anesthetic and a 3-5 mL syringe for the
spinal anesthetic agent.
10. Anesthetic agent: Typically a local anesthetic with or without additives
like epinephrine or opioids to prolong the block and enhance analgesia.
11. Bandage: For securing the needle site post-procedure
Casting Alloys
Dental Materials
Casting Alloys
Applications-inlay, onlay, crowns, and bridges
Terms
a. Precious-based on valuable elements
b. Noble or immune-corrosion-resistant element or alloy
c. Base or active-corrosion-prone alloy
d. Passive -corrosion resistant because of surface oxide film
e. Karat (24 karat is 100% gold; 18 karat is 75% gold)
f. Fineness (1000 fineness is I00% gold; 500 fineness is 50% gold)
Classification
High-gold alloys are > 75% gold or other noble metals
Type 1- 83% noble metals (e.g., in simple inlays)
Type II-≥78% noble metals (e.g.,in inlays and onlays)
Type IlI-≥75% noble metals (e.g., in crowns and bridges)
Type IV-≥75% noble metals (e.g., in partial dentures)
Medium-gold alloys are 25% to 75% gold or other noble metals
Low-gold alloys are <25% gold or other noble metals
Gold-substitute alloys arc alloys not containing gold
(1) Palladium-silver alloys-passive .because of mixed oxide film
(2) Cobalt-chromium alloys-passive because of Cr203 oxide film
(3) Iron-chromium alloys-passive because of Cr203 oxide film
Titanium alloys are based on 90% to 100% titanium ; passive because of TiO2 oxide film
Components of gold alloys
- Gold contributes to corrosion resistance
- Copper contributes to hardness and strength
- Silver counteracts orange color of copper
- Palladium increases melting point and hardness
- Platinum increases melting point
- Zinc acts as oxygen scavenger during casting
Manipulation
- Heated to just beyond melting temperature for casting
o Cooling shrinkage causes substantial contraction
Properties
Physical
- Electrical and thermal conductors
- Relatively low coefficient of thermal expansion
Chemical
- Silver content affects susceptibility to tarnish
- Corrosion resistance is attributable to nobility or passivation
Mechanical
- High tensile and compressive strengths but relatively weak in thin sections, such as margins, and can be deformed relatively easily
- Good wear resistance except in contact with Porcelain
Sufentanil
Pharmacology
Sufentanil
A synthetic opioid related to fentanyl.
About 7 times more potent than fentanyl.
Has a slightly more rapid onset of action than fentanyl.
Cholangitis
General Pathology
Cholangitis
Cholangitis is inflammation of the bile ducts.
1. It is usually associated with biliary duct obstruction by gallstones or carcinoma, which leads to infection with enteric organisms. This results in purulent exudation within the bile ducts and bile stasis.
2. Clinically, cholangitis presents with jaundice, fever, chills. leukocytosis, and right upper quadrant pain