NEET MDS Synopsis
Diphenoxylate
Pharmacology
Diphenoxylate (present in Lomotil)
A meperidine congener
Not absorbed very well at recommended doses.
Very useful in the treatment of diarrhea.
ANTIGEN-ANTIBODY REACTIONS
General Microbiology
ANTIGEN-ANTIBODY REACTIONS
I. NATURE OF ANTIGEN-ANTIBODY REACTIONS
A. Lock and Key Concept
The combining site of an antibody is located in the Fab portion of the molecule and is constructed from the hypervariable regions of the heavy and light chains. Antigen-antibody reactions is one of a key (i.e. the antigen) which fits into a lock (i.e. the antibody).
B. Non-covalent Bonds
The bonds that hold the antigen to the antibody combining site are all non-covalent in nature. These include hydrogen bonds, electrostatic bonds, Van der Waals forces and hydrophobic bonds.
C. Reversibility
Since antigen-antibody reactions occur via non-covalent bonds, they are by their nature reversible.
II. AFFINITY AND AVIDITY
A. Affinity
Antibody affinity is the strength of the reaction between a single antigenic determinant and a single combining site on the antibody. It is the sum of the attractive and repulsive forces operating between the antigenic determinant and the combining site of the antibody .
B. Avidity
Avidity is a measure of the overall strength of binding of an antigen with many antigenic determinants and multivalent antibodies. Avidity is influenced by both the valence of the antibody and the valence of the antigen. Avidity is more than the sum of the individual affinities.
III. SPECIFICITY AND CROSS REACTIVITY
A. Specificity
Specificity refers to the ability of an individual antibody combining site to react with only one antigenic determinant or the ability of a population of antibody molecules to react with only one antigen. In general, there is a high degree of specificity in antigen-antibody reactions.
B. Cross reactivity
Cross reactivity refers to the ability of an individual antibody combining site to react with more than one antigenic determinant or the ability of a population of antibody molecules to react with more than one antigen.
Periodontal Fibers
PeriodontologyPeriodontal Fibers
Periodontal fibers play a crucial role in maintaining the integrity of the
periodontal ligament and supporting the teeth within the alveolar bone.
Understanding the different groups of periodontal fibers is essential for
comprehending their functions in periodontal health and disease.
1. Gingivodental Group
Location:
Present on the facial, lingual, and interproximal surfaces of the
teeth.
Attachment:
These fibers are embedded in the cementum just beneath the
epithelium at the base of the gingival sulcus.
Function:
They help support the gingiva and maintain the position of the
gingival margin.
2. Circular Group
Location:
These fibers course through the connective tissue of the marginal
and interdental gingiva.
Attachment:
They encircle the tooth in a ring-like fashion.
Function:
The circular fibers help maintain the contour of the gingiva and
provide support to the marginal gingiva.
3. Transseptal Group
Location:
Located interproximally, these fibers extend between the cementum of
adjacent teeth.
Attachment:
They lie in the area between the epithelium at the base of the
gingival sulcus and the crest of the interdental bone.
Function:
The transseptal fibers are primarily responsible for the
post-retention relapse of orthodontically positioned teeth.
They are sometimes classified as principal fibers of the periodontal
ligament.
Collectively, they form the interdental ligament of the arch,
providing stability to the interproximal areas.
4. Semicircular Fibers
Location:
These fibers attach to the proximal surface of a tooth immediately
below the cementoenamel junction (CEJ).
Attachment:
They go around the facial or lingual marginal gingiva of the tooth
and attach to the other proximal surface of the same tooth.
Function:
Semicircular fibers help maintain the position of the tooth and
support the gingival tissue around it.
5. Transgingival Fibers
Location:
These fibers attach to the proximal surface of one tooth and
traverse the interdental space diagonally to attach to the proximal
surface of the adjacent tooth.
Function:
Transgingival fibers provide support across the interdental space,
helping to maintain the position of adjacent teeth and the integrity of
the gingival tissue.
Lines in Third Molar Assessment
Oral and Maxillofacial SurgeryLines in Third Molar Assessment
In the context of third molar (wisdom tooth) assessment and extraction,
several lines are used to evaluate the position and inclination of the tooth, as
well as the amount of bone that may need to be removed during extraction. These
lines provide valuable information for planning the surgical approach and
predicting the difficulty of the extraction.
1. White Line
Description: The white line is a visual marker that
runs over the occlusal surfaces of the first, second, and third molars.
Purpose: This line serves as an indicator of the axial
inclination of the third molar. By assessing the position of the
white line, clinicians can determine the orientation of the third molar in
relation to the adjacent teeth and the overall dental arch.
Clinical Relevance: The inclination of the third molar
can influence the complexity of the extraction procedure, as well as the
potential for complications.
2. Amber Line
Description: The amber line is drawn from the bone
distal to the third molar towards the interceptal bone between the first and
second molars.
Purpose: This line helps to delineate which parts of
the third molar are covered by bone and which parts are not. Specifically:
Above the Amber Line: Any part of the tooth above
this line is not covered by bone.
Below the Amber Line: Any part of the tooth below
this line is covered by bone.
Clinical Relevance: The amber line is particularly
useful in the Pell and Gregory classification, which
categorizes the position of the third molar based on its relationship to the
surrounding structures and the amount of bone covering it.
3. Red Line (George Winter's Third Line)
Description: The red line is a perpendicular line drawn
from the amber line to an imaginary line of application of an elevator. This
imaginary line is positioned at the cement-enamel junction (CEJ) on
the mesial aspect of the tooth, except in cases of disto-angular impaction,
where it is at the distal CEJ.
Purpose: The red line indicates the amount of bone that
must be removed before the elevation of the tooth can occur. It effectively
represents the depth of the tooth in the bone.
Clinical Relevance: The length of the red line
correlates with the difficulty of the extraction:
Longer Red Line: Indicates that more bone needs to
be removed, suggesting a more difficult extraction.
Shorter Red Line: Suggests that less bone removal
is necessary, indicating an easier extraction.
Essential vs. Nonessential Amino Acids
Biochemistry
Essential vs. Nonessential Amino Acids
Nonessential
Essential
Alanine
Arginine*
Asparagine
Histidine
Aspartate
Isoleucine
Cysteine
Leucine
Glutamate
Lysine
Glutamine
Methionine*
Glycine
Phenylalanine*
Proline
Threonine
Serine
Tyrptophan
Tyrosine
Valine
*The amino acids arginine, methionine and phenylalanine are considered essential for reasons not directly related to lack of synthesis. Arginine is synthesized by mammalian cells but at a rate that is insufficient to meet the growth needs of the body and the majority that is synthesized is cleaved to form urea. Methionine is required in large amounts to produce cysteine if the latter amino acid is not adequately supplied in the diet. Similarly, phenyalanine is needed in large amounts to form tyrosine if the latter is not adequately supplied in the diet.
Benzodiazepines
Pharmacology
Benzodiazepines
All metabolites are active sedatives except the final glucuronide product.
Elimination half-life varies a great deal from drug to drug.
?-Hydroxylation is a rapid route of metabolism that is unique to triazolam,
midazolam, and alprazolam.
This accounts for the very rapid metabolism and short sedative actions of these
drugs.
Pharmacological effects of benzodiazepines
- Antianxiety.
- Sedation.
- Anticonvulsant (including drug-induced convulsions).
- Amnesia, especially drugs like triazolam.
- Relax skeletal muscle (act on CNS polysynaptic pathways).
Indications
- IV sedation, (e.g., midazolam, diazepam, lorazepam).
- Antianxiety.
- Sleep induction.
- Anticonvulsant (e.g., diazepam, clonazepam).
- Panic disorders.
- Muscle relaxation.
Adverse effects
- Ataxia, confusion.
- Excessive sedation.
- Amnesia (not a desired effect with daytime sedation).
- Altered sleep patterns (increase stage 2 and decrease stage 4 sleep).
Classification of Cementum
PeriodontologyClassification of Cementum According to Schroeder
Cementum is a specialized calcified tissue that covers the roots of teeth and
plays a crucial role in periodontal health. According to Schroeder, cementum can
be classified into several distinct types based on its cellular composition and
structural characteristics. Understanding these classifications is essential for
dental professionals in diagnosing and treating periodontal conditions.
Classification of Cementum
Acellular Afibrillar Cementum:
Characteristics:
Contains neither cells nor collagen fibers.
Present in the coronal region of the tooth.
Thickness ranges from 1 µm to 15 µm.
Function:
This type of cementum is thought to play a role in the
attachment of the gingiva to the tooth surface.
Acellular Extrinsic Fiber Cementum:
Characteristics:
Lacks cells but contains closely packed bundles of Sharpey’s
fibers, which are collagen fibers that anchor the cementum to the
periodontal ligament.
Typically found in the cervical third of the roots.
Thickness ranges from 30 µm to 230 µm.
Function:
Provides strong attachment of the periodontal ligament to the
tooth, contributing to the stability of the tooth in its socket.
Cellular Mixed Stratified Cementum:
Characteristics:
Contains both extrinsic and intrinsic fibers and may contain
cells.
Found in the apical third of the roots, at the apices, and in
furcation areas.
Thickness ranges from 100 µm to 1000 µm.
Function:
This type of cementum is involved in the repair and adaptation
of the tooth root, especially in response to functional demands and
periodontal disease.
Cellular Intrinsic Fiber Cementum:
Characteristics:
Contains cells but no extrinsic collagen fibers.
Primarily fills resorption lacunae, which are areas where
cementum has been resorbed.
Function:
Plays a role in the repair of cementum and may be involved in
the response to periodontal disease.
Intermediate Cementum:
Characteristics:
A poorly defined zone located near the cementoenamel junction
(CEJ) of certain teeth.
Appears to contain cellular remnants of the Hertwig's epithelial
root sheath (HERS) embedded in a calcified ground substance.
Function:
Its exact role is not fully understood, but it may be involved
in the transition between enamel and cementum.
Clinical Significance
Importance of Cementum:
Understanding the different types of cementum is crucial for
diagnosing periodontal diseases and planning treatment strategies.
The presence of various types of cementum can influence the response
of periodontal tissues to disease and trauma.
Cementum in Periodontal Disease:
Changes in the thickness and composition of cementum can occur in
response to periodontal disease, affecting tooth stability and
attachment.
Clinical significance PTH secretion
Biochemistry
Clinical significance
Primary hyperparathyroidism is due to autonomous, abnormal hypersecretion of PTH in the parathyroid gland
Secondary hyperparathyroidism is an appropriately high PTH level seen as a physiological response to hypocalcemia.
A low level of PTH in the blood is known as hypoparathyroidism and is most commonly due to damage to or removal of parathyroid glands during thyroid surgery.