NEET MDS Synopsis
Hepatitis B virus
General Pathology
Hepatitis B virus (“serum hepatitis”)
- Hepatitis B (HBV) may cause acute hepatitis, a carrier state, chronic active disease, chronic persistent disease, fulminant hepatitis, or hepatocellular carcinoma
- It is caused by a DNA virus, the virions are called Dane particles.
b. Incubation period: ranges from 4 to 26 weeks, but averages 6 to 8 weeks.
a. Symptoms last 2 to 4 weeks, but may be asymptomatic.
c. The hepatitis B viral structure has also been named the Dane particle.
Transmission is through contact with infected blood or other body fluids. It can be transmitted by sexual intercourse and is frequently transmitted to newborns of infected mothers by exposure to maternal blood during the birth process
- Associated antigens include core antigen (HBcAg) and surface antigen (HBsAg).
The latter is usually identified in the blood for diagnosis. HbsAg is the earliest marker of acute infection.
HBeAg is also associated with the core. Its presence indicates active acute infection; when anti-HBeAg appears, the patient is no longer infective
- HBV is associated with hepatocellular carcinoma; HBsAg patients have a 200-fold greater risk of hepatocellular carcinoma than subjects who have not been exposed.
Antibodies
- Antibodies to surface antigen (anti-HBs) are considered protective and usually appear after the disappearance of the virus.
-Antibodies to HBcAg are not protective. They are , detected just after the appearance of HBsAg and are used to confirm infection when both HBsAg and anti HBs are absent (window).
- Antibodies to HBeAg are associated with a low risk of infectivity.
d. Infection increases the risk for hepatocellular carcinoma.
e. Laboratory assay of hepatitis B antigens and antibodies:
(1) HBsAg—present only in acute infection or chronic carriers.
(2) HBsAb—detectable only after 6 months post-initial infection. HBsAb is present in chronic infections or vaccinated individuals. Note: HBsAb is also being produced during acute infections and in chronic carriers; however, it is not detectable via current laboratory methods.
(3) HBcAg—present in either acute or chronic infection.
(4) HBeAg—present when there is active viral replication. It signifies that the carrier is highly infectious.
(5) HBeAb—appears after HBeAg. It signifies that the individual is not as contagious.
f. Vaccine: contains HBsAg.
g. Prevention: immunoglobulins (HBsAb) are available.
ERUPTION - The mixed dentition
Dental Anatomy
The mixed dentition
I. Transition dentition between 6 and 12 years of age with primary tooth exfoliation and permanent tooth eruption
2. Its characteristic features have led this to be called the ugly duckling stage because of
a. Edentulated areas
b. Disproportionately sized teeth
c. Various clinical crown heights
d. Crowding
e. Enlarged and edematous gingiva
f. Different tooth colors
Other sedatives
Pharmacology
Other sedatives: carisoprodol, cyclobenzaprine, and methocarbamol are used for muscle relaxation.
Baclofen
1. Used in spasticity states to relax skeletal muscle.
2. Occasionally used in trigeminal neuralgia.
Antihistamines (first-generation H1 receptor blockers)
1. Used for sedation (e.g., diphenhydramine).
Ethyl alcohol
Anti-Parkinson Drugs
Pharmacology
Anti-Parkinson Drugs
The disease involves degeneration of dopaminergic neurons in the nigral-striatal pathway in the basal ganglia. The cause is usually unknown. Sometimes it is associated with hypoxia, toxic chemicals, or cerebral infections.
Strategy
1. Increase dopamine in basal ganglia.
2. Block muscarinic receptors in the basal ganglia, since cholinergic function opposes the action of dopamine in the basal ganglia.
3. Newer therapies, such as the use of β-adrenergic receptor blockers.
Drugs
a. L-dopa plus carbidopa (Sinemet).
b. Bromocriptine, pergolide, pramipexole, ropinirole.
c. Benztropine, trihexyphenidyl, biperiden, procyclidine.
d. Diphenhydramine.
e. Amantadine.
f. Tolcapone and entacapone.
g. Selegiline.
Mechanisms of action of three drugs affecting DOPA
1. L-dopa plus carbidopa:
L-dopa is able to penetrate the blood–brain barrier and is then converted into dopamine. Carbidopa inhibits dopa decarboxylase, which catalyzes the formation of dopamine.
Carbidopa does not penetrate the blood–brain barrier; it therefore prevents the conversion of L-dopa to dopamine outside the CNS but allows
the conversion of L-dopa to dopamine inside the CNS.
2. Bromocriptine, pergolide, pramipexole, and ropinirole are direct dopamine receptor agonists.
3. Benztropine, trihexyphenidyl, biperiden, and procyclidine are antimuscarinic drugs.
4. Diphenhydramine is an antihistamine that has antimuscarinic action.
5. Amantadine releases dopamine and inhibits neuronal uptake of dopamine.
6. Selegiline is an irreversible inhibitor of monoamine oxidase B (MAO-B), which metabolizes dopamine. Selegiline therefore increases the level of dopamine.
7. Tolcapone is an inhibitor of catechol-O-methyl transferase (COMT), another enzyme that metabolizes dopamine.
8. Entacapone is another COMT inhibitor.
Dopamine and acetylcholine.
Loss of dopaminergic neurons in Parkinsonism leads to unopposed action by cholinergic neurons. Inhibiting muscarinic receptors can help alleviate symptoms of Parkinsonism
Adverse effects
1. L-dopa
- The therapeutic effects of the drug decrease with time.
- Oscillating levels of clinical efficacy of the drug (“on-off” effect).
- Mental changes—psychosis.
- Tachycardia and orthostatic hypotension.
- Nausea.
- Abnormal muscle movements (dyskinesias).
2. Tolcapone, entacapone (similar to L-dopa).
3. Direct dopamine receptor agonists (similar to L-dopa).
4. Antimuscarinic drugs
- Typical antimuscarinic adverse effects such as dry mouth.
b. Sedation.
5. Diphenhydramine (see antimuscarinic drugs).
6. Amantadine
- Nausea.
- Dizziness.
- Edema.
- Sweating.
7. Selegiline
- Nausea.
- Dry mouth.
- Dizziness.
- Insomnia.
- Although selegiline is selective for MAO-B, it still can cause excessive toxicity in the presence of tricyclic antidepressants, SSRIs, and meperidine.
Indications
Parkinson’s disease is the obvious major use of the above drugs. Parkinson-like symptoms can occur with many antipsychotic drugs. These symptoms are often treated with antimuscarinic drugs or diphenhydramine.
Dental implications of anti-Parkinson drugs
1. Dyskinesia caused by drugs can present a challenge for dental treatment.
2. Orthostatic hypotension poses a risk when changing from a reclining to a standing position.
3. The dentist should schedule appointments at a time of day at which the best control of the disease occurs.
4. Dry mouth occurs with several of the drugs.
Fungal Diseases
General Medicine
Histoplasmosis
Histoplasmosis is a disease caused by the fungus Histoplasma capsulatum. Its symptoms vary greatly, but the disease primarily affects the lungs.
Occasionally, other organs are affected—this form of the disease is called disseminated histoplasmosis, and it can be fatal if untreated.
H. capsulatum grows in soil and material contaminated with bat or bird droppings. Spores become airborne when contaminated soil is disturbed. Breathing the spores causes infection.
Symptoms
they will start within 3 to 17 days after exposure.
The acute respiratory disease is characterized by respiratory symptoms, a general ill feeling, fever, chest pains, and a dry or nonproductive cough.
Chronic lung disease resembles tuberculosis and can worsen over months or years
Treatment
Antifungal medications are used to treat severe cases of acute histoplasmosis and all cases of chronic and disseminated disease
Candidiasis
Candidiasis, commonly called yeast infection or thrush, is a fungal infection of any of the Candida species, of which Candida albicans is probably the most common.
candidiasis can usually only be found in exposed and moist parts of the body, such as:
the oral cavity (oral thrush)
the vagina (vaginal candidiasis or thrush)
folds of skin in the diaper area (diaper rash)
the most common cause of vaginal irritation or vaginitis
can also occur on the male genitals, particularly in uncircumcised men.
Symptoms
itching and irritation of the vagina and/or vulva, and a whitish or whitish-gray discharge that may have a "yeasty" smell like beer or baking bread
Diagnosis
KOH (potassium hydroxide) preparation can be diagnostic
Aspergillosis
Aspergillosis is an infection or an allergic response caused by a fungus of the Aspergillus type. It may play a role in allergy, but is best known for causing serious pulmonary infections in immunocompromised patients
It causes illness in three ways:
as an allergic reaction in people with asthma
as a colonization and growth in a lung injury (such as from tuberculosis or lung abscess)
as an invasive systemic infection with pneumonia, nasal necrosis or aural inflammation and necrosis that is spread to other parts of the body by the bloodstream (pulmonary aspergillosis - invasive type).
Symptoms
Allergic aspergillosis
Fever
Malaise
Coughing
Coughing up blood or brownish mucous plugs
Wheezing
Weight loss
Recurrent episodes of lung obstruction
Invasive infection
Fever
Chills
Headaches
Cough
Shortness of breath
Chest pain
Increased sputum production, which may be bloody
Bone pain
Blood in the urine
Decreased urine output
Weight loss
Symptoms involving specific organs
Brain: meningitis
Eye: blindness or visual impairment
Sinuses: sinusitis
Heart: endocarditis
Signs and tests
Abnormal chest X-ray or CT scan
Sputum stain and culture showing Aspergillus
Tissue biopsy (see bronchoscopy with transtracheal biopsy) for aspergillosis
Aspergillus antigen skin test
Aspergillosis precipitin antibody or galactomannan positivity
Elevated serum total IgE (immunoglobulin)
Peripheral eosinophilia with allergic disease
Treatment
intravenous amphotericin B, an antifungal medication.
Itraconazole can also be used, or its newer counterpart voriconazole.
Caspofungin may be tried when other drug therapy has failed.
Endocarditis caused by Aspergillus is treated by surgical removal of the infected heart valves and long-term amphotericin B therapy.
Allergic aspergillosis is treated with oral prednisone.
THE PLASMIDS
General Microbiology
THE PLASMIDS
The extrachromosomal genetic elements, called as plasmids are autonomously replicating , cyclic ,double stranded DNA molecules which are distinct from the cellular chromosome
Classification
Plasmids can be broadly classified as conjugative and nonconjugative.
Conjugative plasmids are large and self-transmissible i.e. they have an apparatus through which they can mediate their own transfer to another cell after coming in contact with the same. Example: RF and certain bacteriocinogen plasmids.
Nonconjugative plasmids are small in size and can be mobilised for transfer into another cell only through the help of a conjugative plasmid. To this group belong some ‘r’ determinants and few bacteriocinogenic plasmids. Plasmids can also be transferred without cell contact by the process of transfection.
Properties of plasmids
Double stranded DNA , Autonomously replicate in host cell, Plasmd specific, Free DNA is transferred b transfection
Significance of Plasmids :The spread of resistance to antibiotics is one such well known example. These also play an important role in the geochemical cycle by spreading genes for the degradation of complex organic compounds.
Proteins
PhysiologyProteins:
about 50 - 60% of the dry mass of a typical cell
subunit is the amino acid & amino acids are linked by peptide bonds
2 functional categories = structural (proteins part of the structure of a cell like those in the cell membrane) & enzymes
Enzymes are catalysts. Enzymes bind temporarily to one or more of the reactants of the reaction they catalyze. In doing so, they lower the amount of activation energy needed and thus speed up the reaction
Edgewise Technique
OrthodonticsEdgewise Technique
The Edgewise Technique is based on the use of brackets that have a slot
(or edge) into which an archwire is placed. This design allows for precise
control of tooth movement in multiple dimensions (buccal-lingual,
mesial-distal, and vertical).
Mechanics:
The technique utilizes a combination of archwires, brackets, and
ligatures to apply forces to the teeth. The archwire is engaged in the
bracket slots, and adjustments to the wire can be made to achieve
desired tooth movements.
Components of the Edgewise Technique
Brackets:
Edgewise Brackets: These brackets have a vertical
slot that allows the archwire to be positioned at different angles,
providing control over the movement of the teeth. They can be made of
metal or ceramic materials.
Slot Size: Common slot sizes include 0.022 inches
and 0.018 inches, with the choice depending on the specific treatment
goals.
Archwires:
Archwires are made from various materials (stainless steel,
nickel-titanium, etc.) and come in different shapes and sizes. They
provide the primary force for tooth movement and can be adjusted
throughout treatment to achieve desired results.
Ligatures:
Ligatures are used to hold the archwire in place within the bracket
slots. They can be elastic or metal, and their selection can affect the
friction and force applied to the teeth.
Auxiliary Components:
Additional components such as springs, elastics, and separators may
be used to enhance the mechanics of the Edgewise system and facilitate
specific tooth movements.
Advantages of the Edgewise Technique
Precision:
The Edgewise Technique allows for precise control of tooth movement
in all three dimensions, making it suitable for complex cases.
Versatility:
It can be used to treat a wide range of malocclusions, including
crowding, spacing, overbites, underbites, and crossbites.
Effective Force Application:
The design of the brackets and the use of archwires enable the
application of light, continuous forces, which are more effective and
comfortable for patients.
Predictable Outcomes:
The technique is based on established principles of biomechanics,
leading to predictable and consistent treatment outcomes.
Applications of the Edgewise Technique
Comprehensive Orthodontic Treatment: The Edgewise
Technique is commonly used for full orthodontic treatment in both children
and adults.
Complex Malocclusions: It is particularly effective for
treating complex cases that require detailed tooth movement and alignment.
Retention: After active treatment, the Edgewise system
can be used in conjunction with retainers to maintain the corrected
positions of the teeth.