NEET MDS Synopsis
Pharyngeal Arch
Anatomy
Pharyngeal Arch
Arch Artery
Cranial Nerve
Skeletal elements
Muscles
1
Terminal Branch of maxillary artery
Maxillary and mandibular division of trigemenial (V)
Derived from arch cartilages (originating from neural crest):
From maxillary cartilages:
Alispenoid, incus
From mandibular:
Mackel’s cartilage, malleus
Upper portion of external ear (auricle) is derived from dorsal aspect of 1st pharyngeal arch.
Derived by direct ossification from arch dermal mesenchyme:
Maxilla, zygomatic, squamous portion of temporal bone, mandible
Muscles of mastication (temporalis, masseter, and pterygoids), mylohyoid, anterior belly of digastric, tensor tympani, tensor veli palatini (originate from cranial somitomere 4)
2
Stapedius artery (embryologic) and cortiotympanic artery (adult)
Facial nerve (VII)
Stapes, styloid process, stylohyoid ligament, lesser horns and upper rim of hyoid (derived from the second arch cartilage; originate from neural crest).
Lower portion of external ear (auricle) is derived from 2nd pharyngeal arch.
Muscles of facial expression (orbicularis oculi, orbicularis oris, auricularis, platysma, fronto-ooccipitalis, buccinator), posterior belly of digastric, stylohyoid, stapedius (originate from cranial somitomere 6)
3
Common carotid artery, most of internal carotid
Glossopharyngeal (IX)
Lower rim and greater horn of hyoid (derived from the third arch cartilage; originate from neural crest cells)
Sytlopharyngeus (originate from cranial somitomere 7)
4
Left: Arch of aorta;
Right: Right subclavian artery;
Original sprouts of pulmonary arteries
Superior laryngeal branch of vagus (X)
Laryngeal cartilages (Derived from the 4th arch cartilage, originate from lateral plate mesoderm)
Constrictors of pharynx, cricothyroid, levator veli palatine (originate from occipital somites 2-4)
6
Ductus arteriosus; roots of definitive pulmonary arteries
Recurrent laryngeal branch of vagus (X)
Laryngeal cartilages (derived from the 6th-arch cartilage; originate from lateral plate mesoderm)
Intrinsic muscles of larynx (originate from occipital somites 1 and 2)
Hepatitis Summary
General Pathology
Summary
Hepatitis A → ssRNA → Picornavirus → Oral–anal
Hepatitis B → dsDNA → Hepadnavirus → Sexual contact , Blood (needles), Perinatal
Hepatitis C → ssRNA → Flavivirus → Sexual contact , Blood (needles)
Hepatitis D → ssRNA → Deltavirus → Sexual contact, Blood (needles)
Hepatitis E → ssRNA → Calicivirus → Oral–anal
Superior Constrictor Muscle
AnatomySuperior Constrictor Muscle
Origin: Hamulus, pterygo-mandibular raphe, and
mylohyoid line of the mandible.
Insertion: Median raphe of the pharynx.
Nerve Supply: Vagus nerve via the pharyngeal plexus.
Arterial Supply: Ascending pharyngeal artery, ascending
palatine artery, tonsillar branch of the facial artery, and dorsal branch of
the lingual artery.
Action: Constricts the wall of the pharynx during
swallowing.
Monocytosis
General Pathology
Monocytosis:
Causes
-Infections causing lymphocytosis, especialy tuberculosis and typhoid.
-Monocytic leukaemia.
-Some auto immune diseases.
3-D Structure of proteins
Biochemistry
3-D Structure of proteins
Proteins are the main players in the life of a cell. Each protein is a unique sequence of amino acid residues, each of which folds into a unique, stable, three dimentional structure that is biologically functional.
Conformation = spatial arrangement of atoms that depends on rotation of bonds. Can change without breaking covalent bonds.
Since each residue has a number of possible conformations, and there are many residues in a protein, the number of possible conformations for a protein is enormous.
Native conformation = single, stable shape a protein assumes under physiological conditions.
In native conformation, rotation around covalent bonds in polypeptide is constrained by a number of factors ( H-bonding, weak interactions, steric interference)
Biological function of proteins depends completely on its conformation. In biology, shape is everything.
Proteins can be classified as globular or fibrous.
There are 4 levels of protein structure
Primary structure
linear sequence of amino acids
held by covalent forces
primary structure determines all oversall shape of folded polypeptides (i.e primary structure determines secondary , tertiary, and quaternary structures)
Secondary structure
regions of regularly repeating conformations of the peptide chain (α helices, β sheets)
maintained by H-bonds between amide hydrogens and carbonyl oxygens of peptide backbone.
Tertiary structure
completely folded and compacted polypeptide chain.
stabilized by interactions of sidechains of non-neighboring amino acid residues (fibrous proteins lack tertiary structure)
Quaternary structure
association of two or more polypeptide chains into a multisubunit protein.
Resistance Form in Dental Restorations
Conservative DentistryResistance Form in Dental Restorations
Resistance form is a critical concept in operative dentistry that refers to
the design features of a cavity preparation that enhance the ability of a
restoration to withstand masticatory forces without failure. This lecture will
cover the key elements that contribute to resistance form, the factors affecting
it, and the implications for different types of restorative materials.
1. Elements of Resistance Form
A. Design Features
Flat Pulpal and Gingival Floors:
Flat surfaces provide stability and help distribute occlusal forces
evenly across the restoration, reducing the risk of displacement.
Box-Shaped Cavity:
A box-shaped preparation enhances resistance by providing a larger
surface area for bonding and mechanical retention.
Inclusion of Weakened Tooth Structure:
Including weakened areas in the preparation helps to prevent
fracture under masticatory forces by redistributing stress.
Rounded Internal Line Angles:
Rounding internal line angles reduces stress concentration points,
which can lead to failure of the restoration.
Adequate Thickness of Restorative Material:
Sufficient thickness is necessary to ensure that the restoration can
withstand occlusal forces without fracturing. The required thickness
varies depending on the type of restorative material used.
Cusp Reduction for Capping:
When indicated, reducing cusps helps to provide adequate support for
the restoration and prevents fracture.
B. Deepening of Pulpal Floor
Increased Bulk: Deepening the pulpal floor increases
the bulk of the restoration, enhancing its resistance to occlusal forces.
2. Features of Resistance Form
A. Box-Shaped Preparation
A box-shaped cavity preparation is essential for providing resistance
against displacement and fracture.
B. Flat Pulpal and Gingival Floors
These features help the tooth resist occlusal masticatory forces without
displacement.
C. Adequate Thickness of Restorative Material
The thickness of the restorative material should be sufficient to
prevent fracture of both the remaining tooth structure and the restoration.
For example:
High Copper Amalgam: Minimum thickness of 1.5 mm.
Cast Metal: Minimum thickness of 1.0 mm.
Porcelain: Minimum thickness of 2.0 mm.
Composite and Glass Ionomer: Typically require
thicknesses greater than 2.5 mm due to their wear potential.
D. Restriction of External Wall Extensions
Limiting the extensions of external walls helps maintain strong marginal
ridge areas with adequate dentin support.
E. Rounding of Internal Line Angles
This feature reduces stress concentration points, enhancing the overall
resistance form.
F. Consideration for Cusp Capping
Depending on the amount of remaining tooth structure, cusp capping may
be necessary to provide adequate support for the restoration.
3. Factors Affecting Resistance Form
A. Amount of Occlusal Stresses
The greater the occlusal forces, the more robust the resistance form
must be to prevent failure.
B. Type of Restoration Used
Different materials have varying requirements for thickness and design
to ensure adequate resistance.
C. Amount of Remaining Tooth Structure
The more remaining tooth structure, the better the support for the
restoration, which can enhance resistance form.
4. Clinical Implications
A. Cavity Preparation
Proper cavity preparation is essential for achieving optimal resistance
form. Dentists should consider the design features and material requirements
when preparing cavities.
B. Material Selection
Understanding the properties of different restorative materials is
crucial for ensuring that the restoration can withstand the forces it will
encounter in the oral environment.
C. Monitoring and Maintenance
Regular monitoring of restorations is important to identify any signs of
failure or degradation, allowing for timely intervention.
Dens in Dente
PedodonticsDens in Dente (Tooth Within a Tooth)
Dens in dente, also known as "tooth within a tooth," is a developmental
dental anomaly characterized by an invagination of the enamel and dentin,
resulting in a tooth structure that resembles a tooth inside another tooth. This
condition can affect both primary and permanent teeth.
Diagnosis
Radiographic Verification:
The diagnosis of dens in dente is confirmed through radiographic
examination. Radiographs will typically show the characteristic
invagination, which may appear as a radiolucent area within the tooth
structure.
Characteristics
Developmental Anomaly:
Dens in dente is described as a lingual invagination of the enamel,
which can lead to various complications, including pulp exposure,
caries, and periapical pathology.
Occurrence:
This condition can occur in both primary and permanent teeth,
although it is most commonly observed in the permanent dentition.
Commonly Affected Teeth
Permanent Maxillary Lateral Incisors:
Dens in dente is most frequently seen in the permanent maxillary
lateral incisors. The presence of deep lingual pits in these teeth
should raise suspicion for this condition.
Unusual Cases:
There have been reports of dens invaginatus occurring in unusual
locations, including:
Mandibular primary canine
Maxillary primary central incisor
Mandibular second primary molar
Genetic Considerations
Inheritance Pattern:
The condition may exhibit an autosomal dominant inheritance pattern,
as evidenced by the occurrence of dens in dente within the same family,
where some members have the condition while others present with deep
lingual pits.
Variable Expressivity and Incomplete Penetrance:
The variability in expression of the condition among family members
suggests that it may have incomplete penetrance, meaning not all
individuals with the genetic predisposition will express the phenotype.
Clinical Implications
Management:
Early diagnosis and management are crucial to prevent complications
associated with dens in dente, such as pulpitis or abscess formation.
Treatment may involve restorative procedures or endodontic therapy,
depending on the severity of the invagination and the health of the
pulp.
Applegate's Rules
Prosthodontics→ Following rules should be considered to classify partially edentulous
arches, based on Kennedy's classification.
Rule 1:
→ Classification should follow, rather than precede extraction, that might
alter the original classification.
Rule 2:
→ If 3rd molar is missing and not to be replaced, it is not
considered in classification.
Rule 3:
→ If the 3rd molar is present and is to be used as an abutment, it
is considered in classification.
Rule 4:
→ If second molar is missing and is not to be replaced, it is not
considered in classification.
Rule 5:
→ The most posterior edentulous area or areas always determine the
classification.
Rule 6:
→ Edentulous areas other than those, which determine the classification are
referred as modification spaces and are designated by their number.
Rule 7:
→ The extent of modification is not considered, only the number of additional
edentulous areas are taken into consideration (i.e. no. of teeth missing in
modification spaces are not considered, only no. of additional edentulous spaces
are considered).
Rule 8:
→ There can be no modification areas in class IV.