NEET MDS Synopsis
Water Acid Bases & Buffers -pKa
Biochemistry
Acids and bases can be classified as proton donors and proton acceptors, respectively. This means that the conjugate base of a given acid will carry a net charge that is more negative than the corresponding acid. In biologically relavent compounds various weak acids and bases are encountered, e.g. the acidic and basic amino acids, nucleotides, phospholipids etc.
Weak acids and bases in solution do not fully dissociate and, therefore, there is an equilibrium between the acid and its conjugate base. This equilibrium can be calculated and is termed the equilibrium constant = Ka. This is also referred to as the dissociation constant as it pertains to the dissociation of protons from acids and bases.
In the reaction of a weak acid:
HA <-----> A- + H+
the equlibrium constant can be calculated from the following equation:
Ka = [H+][A-]/[HA]
As in the case of the ion product:
pKa = -logKa
Therefore, in obtaining the -log of both sides of the equation describing the dissociation of a weak acid we arrive at the following equation:
-logKa = -log[H+][A-]/[HA]
Since as indicated above -logKa = pKa and taking into account the laws of logrithms:
pKa = -log[H+] -log[A-]/[HA]
pKa = pH -log[A-]/[HA]
From this equation it can be seen that the smaller the pKa value the stronger is the acid. This is due to the fact that the stronger an acid the more readily it will give up H+ and, therefore, the value of [HA] in the above equation will be relatively small.
Wedging Techniques
Conservative DentistryWedging Techniques
Various wedging methods are employed to achieve optimal results,
especially in cases involving gingival recession or wide proximal boxes. Below
are descriptions of different wedging techniques, including "piggy back"
wedging, double wedging, and wedge wedging.
1. Piggy Back Wedging
A. Description
Technique: In piggy back wedging, a second smaller
wedge is placed on top of the first wedge.
Indication: This technique is particularly useful
in patients with gingival recession, where there is a risk of overhanging
restoration margins that could irritate the gingiva.
B. Purpose
Prevention of Gingival Overhang: The additional
wedge helps to ensure that the restoration does not extend beyond the tooth
surface into the gingival area, thereby preventing potential irritation and
maintaining periodontal health.
2. Double Wedging
A. Description
Technique: In double wedging, wedges are placed
from both the lingual and facial surfaces of the tooth.
Indication: This method is beneficial in cases
where the proximal box is wide, providing better adaptation of the matrix
band and ensuring a tighter seal.
B. Purpose
Enhanced Stability: By using wedges from both
sides, the matrix band is held securely in place, reducing the risk of
material leakage and improving the overall quality of the restoration.
3. Wedge Wedging
A. Description
Technique: In wedge wedging, a second wedge is
inserted between the first wedge and the matrix band, particularly in
specific anatomical situations.
Indication: This technique is commonly used in the
maxillary first premolar, where a mesial concavity may complicate the
placement of the matrix band.
B. Purpose
Improved Adaptation: The additional wedge helps to
fill the space created by the mesial concavity, ensuring that the matrix
band conforms closely to the tooth surface and providing a better seal for
the restorative material.
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.
Mouth Protectors
Dental Materials
Mouth Protectors
Use - to protect against effects of blows to chin, top of the head, the face, or grinding of the teeth
Types
o Stock protectors-least desirable because of poor fit
o Mouth-formed protectors-improved fit compared with stock type
o Custom-made protectors-preferred because of durability. low speech impairment, and comfort
I. Components
a. Stock protectors-thermoplastic copolymer of PYA-PE (polyvinyl acetate-polyethylene copolymer)
b. Mouth-formed protectors-thermoplastic copolymer
c. Custom-made protectors- thermoplastic copolymer, rubber. or polyurethane
2. Reaction-physical reaction of hardening during cooling
3. Fabrication
Alginate impression made of maxillary arch. High-strength stone cast poured immediately. Thermoplastic material is heated in hot water and vacuum-molded to cast .
Mouth protector trimmed to within ½ inch of labial fold, clearance provided at the buccal and labial frena, and edges smoothed by flaming. Gagging, taste, irritation. and impairment of speech are minimized with properly fabricated appliances
4. Instructions for use
a. Rinse before and after use with cold water
b. Clean protector occasionally with soap and cool water
c. Store the protector in a rigid container
d. Protect from heat and pressure during storage
e. Evaluate protector routinely for evidence of deterioration
Properties
1. Physical-thermal insulators
2. Chemical-absorbs after during use
3. Mechanical-tensile strength, modulus, and hardness decrease after water absorption, but elongation, tear strength, and resilience increase
4. Biologic-nontoxic as long as no bacterial, fungal, or viral growth occurs on surfaces between uses
Progression from Gingivitis to Periodontitis
PeriodontologyProgression from Gingivitis to Periodontitis
The transition from gingivitis to periodontitis is a critical process in
periodontal disease progression. This lecture will outline the key stages
involved in this progression, highlighting the changes in microbial composition,
host response, and tissue alterations.
Pathway of Progression
Establishment and Maturation of Supragingival Plaque:
The process begins with the formation of supragingival plaque, which
is evident in gingivitis.
As this plaque matures, it becomes more complex and can lead to
changes in the surrounding tissues.
Migration of Periodontopathogenic Bacteria:
When the microbial load overwhelms the local host immune response,
pathogenic bacteria migrate subgingivally (below the gum line).
This migration establishes a subgingival niche that is conducive to
the growth of periodontopathogenic bacteria.
Initial Lesion
Timeline:
The initial lesion, characterized by subclinical gingivitis, appears
approximately 2 to 4 days after the colonization of the gingival sulcus
by bacteria.
Clinical Manifestations:
Vasculitis: Inflammation of blood vessels in the
gingival tissue.
Exudation of Serous Fluid: Increased flow of
gingival crevicular fluid (GCF) from the gingival sulcus.
Increased PMN Migration: Polymorphonuclear
neutrophils (PMNs) migrate into the sulcus in response to the
inflammatory process.
Alteration of Junctional Epithelium: Changes occur
at the base of the pocket, affecting the integrity of the junctional
epithelium.
Collagen Dissolution: Perivascular collagen begins
to dissolve, contributing to tissue breakdown.
Early Lesion
Timeline:
The early lesion forms within 4 to 7 days after the initial lesion
due to the continued accumulation of bacterial plaque.
Characteristics:
Leukocyte Accumulation: There is a significant
increase in leukocytes at the site of acute inflammation, indicating an
ongoing immune response.
Cytopathic Alterations: Resident fibroblasts
undergo cytopathic changes, affecting their function and viability.
Collagen Loss: Increased collagen loss occurs
within the marginal gingiva, contributing to tissue destruction.
Proliferation of Basal Cells: The basal cells of
the junctional epithelium proliferate in response to the inflammatory
environment.
Operant Conditioning
PedodonticsOperant Conditioning
Operant conditioning is based on the idea that an individual's response can
change as a result of reinforcement or punishment. Behaviors that lead to
satisfactory outcomes are likely to be repeated, while those that result in
unsatisfactory outcomes are likely to diminish. The four basic types of operant
conditioning are:
Positive Reinforcement:
Definition: Positive reinforcement involves
providing a rewarding stimulus after a desired behavior is exhibited,
which increases the likelihood of that behavior being repeated in the
future.
Application in Pedodontics: Dental professionals
can use positive reinforcement to encourage cooperative behavior in
children. For example, offering praise, stickers, or small prizes for
good behavior during a dental visit can motivate children to remain calm
and follow instructions.
Negative Reinforcement:
Definition: Negative reinforcement involves the
removal of an unpleasant stimulus when a desired behavior occurs, which
also increases the likelihood of that behavior being repeated.
Application in Pedodontics: An example of negative
reinforcement might be allowing a child to leave the dental chair or
take a break from a procedure if they remain calm and cooperative. By
removing the discomfort of the procedure when the child behaves well,
the child is more likely to repeat that calm behavior in the future.
Omission (or Extinction):
Definition: Omission involves the removal of a
positive stimulus following an undesired behavior, which decreases the
likelihood of that behavior being repeated. It can also refer to the
failure to reinforce a behavior, leading to its extinction.
Application in Pedodontics: If a child exhibits
disruptive behavior during a dental visit and does not receive praise or
rewards, they may learn that such behavior does not lead to positive
outcomes. For instance, if a child throws a tantrum and does not receive
a sticker or praise afterward, they may be less likely to repeat that
behavior in the future.
Punishment:
Definition: Punishment involves introducing an
unpleasant stimulus or removing a pleasant stimulus following an
undesired behavior, which decreases the likelihood of that behavior
being repeated.
Application in Pedodontics: While punishment is
generally less favored in pediatric settings, it can be applied in a
very controlled manner. For example, if a child refuses to cooperate and
behaves inappropriately, the dental professional might explain that they
will not be able to participate in a fun activity (like choosing a toy)
if they continue to misbehave. However, it is essential to use
punishment sparingly and focus more on positive reinforcement to
encourage desired behaviors.
Vitamin B12: Cobalamin
Biochemistry
Vitamin B12: Cobalamin
Vitamin B12, also known as cobalamin, aids in the building of genetic material, production of normal red blood cells, and maintenance of the nervous system.
RDA The Recommended Dietary Allowance (RDA) for vitamin B12 is 2.4 mcg/day for adult males and females
Vitamin B12 Deficiency
Vitamin B12 deficiency most commonly affects strict vegetarians (those who eat no animal products), infants of vegan mothers, and the elderly. Symptoms of deficiency include anemia, fatigue, neurological disorders, and degeneration of nerves resulting in numbness and tingling.
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.