NEET MDS Synopsis
Lupus erythematosus
General Pathology
Lupus erythematosus
- chronic discoid lupus is primarily limited to the skin, while SLE can involve the skin and other systems.
- pathogenesis: light and other external agents plus deposition of DNA (planted antigen) and immune complexes in the basement membrane.
Histology:
- basal cells along the dermal-epidermal junction and hair shafts (reason for alopecia) are vacuolated (liquefactive degeneration)
- thickening of lamina densa as a reaction to injury.
- immunofluorescent studies reveal a band of immunofluorescence (band test) in involved skin of chronic discoid lupus or involved/uninvolved skin of SLE.
- lymphocytic infiltrate at the dermal-epidermal junction and papillary dermis.
Periodontium
Dental Anatomy
The periodontium consists of tissues supporting and investing the tooth and includes cementum, the periodontal ligament (PDL), and alveolar bone.
Parts of the gingiva adjacent to the tooth also give minor support, although the gingiva is Not considered to be part of the periodontium in many texts. For our purposes here, the groups Of gingival fibers related to tooth investment are discussed in this section.
Aspirin
Pharmacology
Aspirin
Mechanism of Action
ASA covalently and irreversibly modifies both COX-1 and COX-2 by acetylating serine-530 in the active site Acetylation results in a steric block, preventing arachidonic acid from binding
Uses of Aspirin
Dose-Dependent Effects:
Low: < 300mg blocks platelet aggregation
Intermediate: 300-2400mg/day antipyretic and analgesic effects
High: 2400-4000mg/day anti-inflammatory effects
Often used as an analgesic (against minor pains and aches), antipyretic (against fever), and anti-inflammatory. It has also an anticoagulant (blood thinning) effect and is used in long-term low-doses to prevent heart attacks
Low-dose long-term aspirin irreversibly blocks formation of thromboxane A2 in platelets, producing an inhibitory affect on platelet aggregation, and this blood thinning property makes it useful for reducing the incidence of heart attacks
Its primary undesirable side effects, especially in stronger doses, are gastrointestinal distress (including ulcers and stomach bleeding) and tinnitus. Another side effect, due to its anticoagulant properties, is increased bleeding in menstruating women.
Antiemetics
Pharmacology
Antiemetics
Antiemetic drugs are generally more effective in prophylaxis than treatment. Most antiemetic agents relieve nausea and vomiting by acting on the vomiting centre, dopamine receptors, chemoreceptors trigger zone (CTZ), cerebral cortex, vestibular apparatus, or a combination of these.
Drugs used in the treatment of nausea and vomiting belong to several different groups. These include:
1. Phenothiazines, such as chlorpromazine, act on CTZ and vomiting centre, block dopamine receptors, are effective in preventing or treating nausea and vomiting induced by drugs, radiation therapy, surgery and most other stimuli (e.g. pregnancy).
They are generally ineffective in motion sickness.
Droperidol had been used most often for sedation in endoscopy and surgery, usually in combination with opioids or benzodiazepines
2. Antihistamines such as promethazine and Dimenhyrinate are especially effective in prevention and treatment of motion.
3. Metoclopramide has both central and peripheral antiemetic effects. Centrally, it antagonizes the action of dopamine. Peripherally metoclopramide stimulates the release of acetylcholine, which in turn, increases the rate of gastric. It has similar indications to those of chlorpromazine.
4. Scopolamine, an anticholinergic drug, is very effective in reliving nausea & vomiting associated with motion sickness.
5. Ondansetron, a serotonin antagonist, is effective in controlling chemical-induced vomiting and nausea such those induced by anticancer drugs.
6. Benzodiazepines: The antiemetic potency of lorazepam and alprazolam is low. Their beneficial effects may be due to their sedative, anxiolytic, and amnesic properties
Nitrous Oxide
Pharmacology
Nitrous Oxide (N2O)
MAC 100%, blood/gas solubility ratio 0.47
- An inorganic gas., low solubility in blood, but greater solubility than N2
- Inflammable, but does support combustion.
- Excreted primarily unchanged through the lungs.
- It provides amnesia and analgesia when administered alone.
- Does not produce muscular relaxation.
- Less depressant to both the cardiovascular system and respiratory system than most of the other inhalational anesthetics.
- Lack of potency and tendency to produce anoxia are its primary limitations.
- The major benefit of nitrous oxide is its ability to reduce the amount of the secondary anesthetic agent that is necessary to reach a specified level of anesthesia.
Tooth Deformation Under Load
Conservative DentistryTooth Deformation Under Load
Biomechanical Properties of Teeth
Deformation (Strain): Teeth are not rigid structures;
they undergo deformation (strain) during normal loading. This deformation is
a natural response to the forces applied during chewing and other functional
activities.
Intraoral Loads: The loads experienced by teeth can
vary widely, with reported forces ranging from 10 to 431 N (1 N = 0.225 lb
of force). A functional load of approximately 70 N is considered clinically
normal.
Factors Influencing Load Distribution
Number of Teeth: The total number of teeth in the arch
affects how forces are distributed. More teeth can share the load, reducing
the stress on individual teeth.
Type of Occlusion: The occlusal relationship (how the
upper and lower teeth come together) influences how forces are transmitted
through the dental arch.
Occlusal Habits: Habits such as bruxism (teeth
grinding) can significantly increase the forces applied to individual teeth,
leading to greater strain and potential damage.
Clinical Implications
Restorative Considerations: Understanding the
biomechanical behavior of teeth under load is essential for designing
restorations that can withstand functional forces without failure.
Patient Management: Awareness of occlusal habits, such
as bruxism, can guide clinicians in developing appropriate treatment plans,
including the use of occlusal splints or other interventions to protect
teeth from excessive forces.
Cephalometric Landmarks
OrthodonticsKey Cephalometric Landmarks
Sella (S):
The midpoint of the sella turcica, a bony structure located at the
base of the skull. It serves as a central reference point in
cephalometric analysis.
Nasion (N):
The junction of the frontal and nasal bones, located at the bridge
of the nose. It is often used as a reference point for the anterior
cranial base.
A Point (A):
The deepest point on the maxillary arch, located between the
anterior nasal spine and the maxillary alveolar process. It is crucial
for assessing maxillary position.
B Point (B):
The deepest point on the mandibular arch, located between the
anterior nasal spine and the mandibular alveolar process. It is
important for evaluating mandibular position.
Pogonion (Pog):
The most anterior point on the contour of the chin. It is used to
assess the position of the mandible in relation to the maxilla.
Gnathion (Gn):
The midpoint between Menton and Pogonion, representing the most
inferior point of the mandible. It is used in various angular
measurements.
Menton (Me):
The lowest point on the symphysis of the mandible. It is used as a
reference for vertical measurements.
Go (Gonion):
The midpoint of the contour of the ramus and the body of the
mandible. It is used to assess the angle of the mandible.
Frankfort Horizontal Plane (FH):
A plane defined by the points of the external auditory meatus (EAM)
and the lowest point of the orbit (Orbitale). It is used as a reference
plane for various measurements.
Orbitale (Or):
The lowest point on the inferior margin of the orbit (eye socket).
It is used in conjunction with the EAM to define the Frankfort
Horizontal Plane.
Ectocanthion (Ec):
The outer canthus of the eye, used in facial measurements and
assessments.
Endocanthion (En):
The inner canthus of the eye, also used in facial measurements.
Alveolar Points:
Points on the alveolar ridge of the maxilla and mandible, often used
to assess the position of the teeth.
Importance of Cephalometric Landmarks
Diagnosis: These landmarks help orthodontists diagnose
skeletal and dental discrepancies, such as Class I, II, or III
malocclusions.
Treatment Planning: By understanding the relationships
between these landmarks, orthodontists can develop effective treatment plans
tailored to the individual patient's needs.
Monitoring Progress: Cephalometric landmarks allow for
the comparison of pre-treatment and post-treatment radiographs, helping to
evaluate the effectiveness of orthodontic interventions.
Research and Education: These landmarks are essential
in orthodontic research and education, providing a standardized method for
analyzing craniofacial morphology.
Nomenclature for stereoisomers
Biochemistry
Nomenclature for stereoisomers: D and L designations are based on the configuration about the single asymmetric carbon in glyceraldehydes
For sugars with more than one chiral center, the D or L designation refers to the asymmetric carbon farthest from the aldehyde or keto group.
Most naturally occurring sugars are D isomers.
D & L sugars are mirror images of one another. They have the same name. For example, D-glucose and L-glucose
Other stereoisomers have unique names, e.g., glucose, mannose, galactose, etc. The number of stereoisomers is 2 n, where n is the number of asymmetric centers. The six-carbon aldoses have 4 asymmetric centers, and thus 16 stereoisomers (8 D-sugars and 8 L-sugars
An aldehyde can react with an alcohol to form a hemiacetal
Similarly a ketone can react with an alcohol to form a hemiketal
Pentoses and hexoses can cyclize, as the aldehyde or keto group reacts with a hydroxyl on one of the distal carbons
E.g., glucose forms an intra-molecular hemiacetal by reaction of the aldehyde on C1 with the hydroxyl on C5, forming a six-member pyranose ring, named after the compound pyran
The representations of the cyclic sugars below are called Haworth projections.
Fructose can form either:
a six-member pyranose ring, by reaction of the C2 keto group with the hydroxyl on C6
a 5-member furanose ring, by reaction of the C2 keto group with the hydroxyl on C5.
Cyclization of glucose produces a new asymmetric center at C1, with the two stereoisomers called anomers, α & β
Haworth projections represent the cyclic sugars as having essentially planar rings, with the OH at the anomeric C1 extending either:
below the ring (α)
above the ring (β).
Because of the tetrahedral nature of carbon bonds, the cyclic form of pyranose sugars actually assume a "chair" or "boat" configuration, depending on the sugar