NEET MDS Synopsis
FUNGAL INFECTION- Aspergillosis
General Pathology
FUNGAL INFECTION
Aspergillosis
Opportunistic infections caused by Aspergillus sp and inhaled as mold conidia, leading to hyphal growth and invasion of blood vessels, hemorrhagic necrosis, infarction, and potential dissemination to other sites in susceptible patients.
Symptoms and Signs: Noninvasive or, rarely, minimally locally invasive colonization of preexisting cavitary pulmonary lesions also may occur in the form of fungus ball (aspergilloma) formation or chronic progressive aspergillosis.
Primary superficial invasive aspergillosis is uncommon but may occur in burns, beneath occlusive dressings, after corneal trauma (keratitis), or in the sinuses, nose, or ear canal.
Invasive pulmonary aspergillosis usually extends rapidly, causing progressive, ultimately fatal respiratory failure unless treated promptly and aggressively. A. fumigatus is the most common causative species.
Extrapulmonary disseminated aspergillosis may involve the liver, kidneys, brain, or other tissues and is usually fatal. Primary invasive aspergillosis may also begin as an invasive sinusitis, usually caused by A. flavus, presenting as fever with rhinitis and headache
Pin size for Restoration
Conservative Dentistry
Pin size
In general, increase in diameter of pin offers more retention but large
sized pins can result in more stresses in dentin. Pins are available in four
color coded sizes:
Name
Pin diameter
Color code
·
Minuta
0.38 mm
Pink
·
Minikin
0.48mm
Red
·
Minim
0.61 mm
Silver
·
Regular
0.78 mm
Gold
Selection of pin size depends upon the following factors:
·
Amount of dentin present
·
Amount of retention required
For most posterior restorations, Minikin size of pins is used because
they provide maximum retention without causing crazing in dentin.
A. Retention vs. Stress
Retention: Generally, an increase in the diameter
of the pin offers more retention for the restoration.
Stress: However, larger pins can result in
increased stresses in the dentin, which may lead to complications such as
crazing or cracking of the tooth structure.
2. Factors Influencing Pin Size Selection
The selection of pin size depends on several factors:
A. Amount of Dentin Present
Assessment: The amount of remaining dentin is a
critical factor in determining the appropriate pin size. More dentin allows
for the use of larger pins, while less dentin may necessitate smaller pins
to avoid excessive stress.
B. Amount of Retention Required
Retention Needs: The specific retention
requirements of the restoration will also influence pin size selection. In
cases where maximum retention is needed, larger pins may be considered,
provided that sufficient dentin is available to accommodate them without
causing damage.
3. Recommended Pin Size for Posterior Restorations
For most posterior restorations, the Minikin size pin
(0.48 mm, color-coded red) is commonly used. This size provides a balance
between adequate retention and minimizing the risk of causing crazing in the
dentin.
SELECTION OF SPRUE
Dental Materials
SELECTION OF SPRUE
1 . DIAMETER :
It should be approximately the same size of the thickest portion of the wax pattern .
Too small sprue diameter suck back porosity results .
2 . SPRUE FORMER ATTACHMENT :
Sprue should be attached to the thickest portion of the wax pattern .
It should be Flared for high density alloys & Restricted for low density alloys .
3 . SPRUE FORMER POSITION
Based on the
1. Individual judgement .
2. Shape & form of the wax pattern .
Patterns may be sprued directly or indirectly .
Indirect method is commonly used
Electrochemical Corrosion
Conservative DentistryElectrochemical Corrosion
Electrochemical corrosion is a significant phenomenon that can affect
the longevity and integrity of dental materials, particularly in amalgam
restorations. Understanding the mechanisms of corrosion, including the role of
electromotive force (EMF) and the specific reactions that occur at the margins
of restorations, is essential for dental clinics
1. Electrochemical Corrosion and Creep
A. Definition
Electrochemical Corrosion: This type of corrosion
occurs when metals undergo oxidation and reduction reactions in the presence
of an electrolyte, leading to the deterioration of the material.
B. Creep at Margins
Creep: In the context of dental amalgams, creep
refers to the slow, permanent deformation of the material at the margins of
the restoration. This can lead to the extrusion of material at the margins,
compromising the seal and integrity of the restoration.
C. Mercuroscopic Expansion
Mercuroscopic Expansion: This phenomenon occurs
when mercury from the amalgam (specifically from the Sn7-8 Hg phase) reacts
with Ag3Sn particles. The reaction produces further expansion, which can
exacerbate the issues related to creep and marginal integrity.
2. Electromotive Force (EMF) Series
A. Definition
Electromotive Force (EMF) Series: The EMF series
is a classification of elements based on their tendency to dissolve in
water. It ranks metals according to their standard electrode potentials,
which indicate how easily they can be oxidized.
B. Importance in Corrosion
Dissolution Tendencies: The EMF series helps
predict which metals are more likely to corrode when in contact with other
metals or electrolytes. Metals higher in the series have a greater tendency
to lose electrons and dissolve, making them more susceptible to corrosion.
C. Calculation of Potential Values
Standard Conditions: The potential values in the
EMF series are calculated under standard conditions, specifically:
One Atomic Weight: Measured in grams.
1000 mL of Water: The concentration of ions is
considered in a liter of water.
Temperature: Typically at 25°C (298
K).
3. Implications for Dental Practice
A. Material Selection
Understanding the EMF series can guide dental professionals in
selecting materials that are less prone to corrosion when used in
combination with other metals, such as in restorations or prosthetics.
B. Prevention of Corrosion
Proper Handling: Careful handling and placement of
amalgam restorations can minimize the risk of electrochemical corrosion.
Avoiding Dissimilar Metals: Reducing the use of
dissimilar metals in close proximity can help prevent galvanic corrosion,
which can occur when two different metals are in contact in the presence of
an electrolyte.
C. Monitoring and Maintenance
Regular monitoring of restorations for signs of marginal breakdown
or corrosion can help in early detection and intervention, preserving the
integrity of dental work.
Example calculations of maximum local anesthetic doses for a 15-kg child
Pharmacology
Example calculations of maximum local anesthetic doses for a 15-kg child
Articaine
5 mg/kg maximum dose × 15 kg = 75 mg
4% articaine = 40 mg/mL
75 mg/(40 mg/mL) = 1.88 mL
1 cartridge = 1.8 mL
Therefore, 1 cartridge is the maximum
Lidocaine
7 mg/kg × 15 kg = 105 mg
2% lidocaine = 20 mg/mL
105 mg/(20 mg/mL) = 5.25 mL
1 cartridge = 1.8 mL
Therefore, 2.9 cartridges is the maximum
Mepivacaine
6.6 mg/kg × 15 kg = 99 mg
3% mepivacaine = 30 mg/mL
99 mg/(30 mg/mL) = 3.3 mL
1 cartridge = 1.8 mL
Therefore, 1.8 cartridges is the maximum.
Prilocaine
8 mg/kg × 15 kg = 120 mg
4% prilocaine = 40 mg/mL
120 mg/(40 mg/mL) = 3 mL
1 cartridge = 1.8 mL
Therefore, 1.67 cartridges is the maximum
Basic characteristics of enzymes
Biochemistry
The basic characteristics of enzymes includes
(i) Almost all the enzymes are proteins and they follow the physical and chemical reactions of proteins (ii) Enzymes are sensitive and labile to heat
(iii) Enzymes are water soluble
(iv) Enzymes could be precipitated by protein precipitating agents such as ammonium sulfate and trichloroacetic acid.
Age Groups and Radiographs
Radiology
Age Groups and Radiographs
Age 2:
Anterior IOPA's: 2
Posterior IOPA's: 4
Bitewings: 2
Total Films: 12
Age 8:
Anterior IOPA's: 8
Posterior IOPA's: 4
Bitewings: 2
Total Films: 14
Age 8 (another entry):
Anterior IOPA's: 8
Posterior IOPA's: 8
Bitewings: 2
Total Films: 20
Summary of Total Films by Type
Anterior IOPA's:
Age 2: 2
Age 8: 8
Age 8 (another entry): 8
Total Anterior IOPA's: 18
Posterior IOPA's:
Age 2: 4
Age 8: 4
Age 8 (another entry): 8
Total Posterior IOPA's: 16
Bitewings:
Age 2: 2
Age 8: 2
Age 8 (another entry): 2
Total Bitewings: 6
Overall Total Films
Total Films for Age 2: 12
Total Films for Age 8 (first entry): 14
Total Films for Age 8 (second entry): 20
Grand Total Films: 12 + 14 + 20 = 46
Porosity defects in Dental casting
Prosthodontics
Porosity
Porosity refers to the presence of voids or spaces within a solid material. In
the context of prosthodontics, it specifically pertains to the presence of small
cavities or air bubbles within a cast metal alloy. These defects can vary in
size, distribution, and number, and are generally undesirable because they
compromise the integrity and mechanical properties of the cast restoration.
Causes of Porosity Defects
Porosity in castings can arise from several factors, including:
1. Incomplete Burnout of the Investment Material: If the wax pattern used to
create the mold is not completely removed by the investment material during the
burnout process, gases can become trapped and leave pores as the metal cools and
solidifies.
2. Trapped Air Bubbles: Air can become trapped in the investment mold during the
mixing and pouring of the casting material. If not properly eliminated, these
air bubbles can lead to porosity when the metal is cast.
3. Rapid Cooling: If the metal cools too quickly, the solidification process may
not be complete, leaving small pockets of unsolidified metal that shrink and
form pores as they solidify.
4. Contamination: The presence of contaminants in the metal alloy or investment
material can also lead to porosity. These contaminants can react with the metal,
forming gases that become trapped and create pores.
5. Insufficient Investment Compaction: If the investment material is not packed
tightly around the wax pattern, small air spaces may remain, which can become
pores when the metal is cast.
6. Gas Formation During Casting: Certain reactions between the metal alloy and
the investment material or other substances in the casting environment can
produce gases that become trapped in the metal.
7. Metal-Mold Interactions: Sometimes, the metal can react with the mold
material, resulting in gas formation or the entrapment of mold material within
the metal, which then appears as porosity.
8. Incorrect Spruing and Casting Design: Poorly designed sprues can lead to
turbulent metal flow, causing air entrapment and subsequent porosity.
Additionally, a complex casting design may result in areas where metal cannot
flow properly, leading to incomplete filling of the mold and the formation of
pores.
Consequences of Porosity Defects
The presence of porosity in a cast restoration can have several negative
consequences:
1. Reduced Strength: The pores within the metal act as stress concentrators,
weakening the material and making it more prone to fracture or breakage under
functional loads.
2. Poor Fit: The pores can prevent the metal from fitting snugly against the
prepared tooth, leading to a poor marginal fit and potential for recurrent decay
or gum irritation.
3. Reduced Biocompatibility: The roughened surfaces and irregularities created
by porosity can harbor plaque and bacteria, which can lead to peri-implant or
periodontal disease.
4. Aesthetic Issues: In visible areas, porosity can be unsightly, affecting the
overall appearance of the restoration.
5. Shortened Service Life: Prosthodontic restorations with porosity defects are
more likely to fail prematurely, requiring earlier replacement.
6. Difficulty in Polishing and Finishing: The presence of porosity makes it
challenging to achieve a smooth, polished finish, which can affect the comfort
and longevity of the restoration.
Prevention and Management of Porosity
To minimize porosity defects in prosthodontic castings, the following steps can
be taken:
1. Proper Investment Technique: Carefully follow the manufacturer's instructions
for mixing and investing the wax pattern to ensure complete burnout and minimize
trapped air bubbles.
2. Slow and Controlled Cooling: Allowing the metal to cool slowly and uniformly
can help to reduce the formation of pores by allowing gases to escape more
easily.
3. Pre-casting De-gassing: Some techniques involve degassing the investment mold
before casting to remove any trapped gases.
4. Cleanliness: Ensure that the metal alloy and investment materials are free
from contaminants.
5. Correct Casting Procedure: Use proper casting techniques to reduce turbulence
and ensure a smooth flow of metal into the mold.
6. Appropriate Casting Design: Design the restoration with proper spruing and a
simple, well-thought-out pattern to allow for even metal flow and minimize
trapped air.
7. Proper Casting Conditions: Control the casting environment to reduce the
likelihood of gas formation during the casting process.
8. Inspection and Quality Control: Carefully inspect the cast restoration for
porosity under magnification and radiographs before it is delivered to the
patient.
9. Repair or Replacement: When porosity defects are detected, they may be
repairable through techniques such as metal condensation, spot welding, or
adding metal with a pin connector. However, in some cases, the restoration may
need to be recast to ensure optimal quality.