NEET MDS Synopsis
Third Generation Cephalosporins
Pharmacology
Third Generation Cephalosporins
Prototype drugs are CEFOTAXIME (IV) and CEFIXIME (oral). CEFTAZIDIME (for Pseudomonas aeruginosa.).
Further expansion of Gm negative spectrum to include hard to treat organisms such as Enterobacter, Serratia, and Pseudomonas.
In addition to better Gm negative spectrum, this group has improved pharmacokinetic properties (longer half-lives) that allow once daily dosing with some agents. In general, activity toward Gm + bacteria is reduced. These are specialty antibiotics that should be reserved for specific uses.
Enterobacteriaciae that are almost always sensitive (>95% sensitive)
E. coli
Proteus mirabilis (indole –)
Proteus vulgaris (indole +)
Klebsiella pneumoniae
Gram negative bacilli that are generally sensitive (>75% sensitive)
Morganella morganii
Providencia retgerri
Citrobacter freundii
Serratia marcescens
Pseudomonas aeruginosa (Ceftazidime only)
Gram negative bacilli that are sometimes sensitive (<75% sensitive)
Enterobacter
Stenotrophomonas (Xanthomonas) maltophilia (Cefoperazone & Ceftazidime only)
Acinetobacter
--> cefepime & cefpirome are promising for these bacteria
Bacteria that are resistant
Listeria monocytogenes
Pseudomonas cepacia
Enterococcus sp.
Uses
1. Gram negative septicemia & other serious Gm – infections
2. Pseudomonas aeruginosa infections (Ceftazidime - 90% effective)
3. Gram negative meningitis - Cefotaxime, Ceftriaxone, Cefepime. For empiric therapy add vancomycin ± rifampin to cover resistant Strep. pneumoniae
4. Gonorrhea - Single shot of Ceftriaxone is drug of choice. Oral cefixime and ceftibuten are also OK.
5. Complicated urinary tract infections, pyelonephritis
6. Osteomyelitis - Ceftriaxone in home health care situations
7. Lyme disease - ceftriaxone in home health care situations
OCCLUSION AND DENTAL DEVELOPMENT-Stages-Mixed Dentition Period
Dental Anatomy
Mixed Dentition Period.
-Begins with the eruption of the first permanent molars distal to the second deciduous molars. These are the first teeth to emerge and they initially articulate in an 'end-on' (one on top of the other) relationship.
-On occasion, the permanent incisors spread out due to spacing. In the older literature, is called by the 'ugly duckling stage.' With the eruption of the permanent canines, the spaces often will close.
-Between ages 6 and 7 years of age there are:
20 deciduous teeth
4 first permanent molars
28 permanent tooth buds in various states of development
Crocodile Tear Syndrome
Oral and Maxillofacial SurgeryCrocodile Tear Syndrome, also known as Bogorad syndrome, is characterized by
involuntary tearing while eating, often resulting from facial nerve damage, such
as that caused by Bell's palsy or trauma. Treatment typically involves botulinum
toxin injections into the lacrimal glands to alleviate symptoms. ### Overview of
Crocodile Tear Syndrome
Crocodile Tear Syndrome is a condition where individuals experience excessive
tearing while eating or drinking. This phenomenon occurs due to misdirection of
nerve fibers from the facial nerve, particularly affecting the lacrimal gland.
Causes
Facial Nerve Injury: Damage to the facial nerve,
especially proximal to the geniculate ganglion, can lead to abnormal nerve
regeneration.
Misdirection of Nerve Fibers: Instead of innervating
the submandibular gland, the nerve fibers may mistakenly connect to the
lacrimal gland via the greater petrosal nerve.
Symptoms
Paroxysmal Lacrimation: Patients experience tearing
during meals, which can be distressing and socially embarrassing.
Associated Conditions: Often seen in individuals
recovering from Bell's palsy or other facial nerve injuries.
Treatment Options
Surgical Intervention: Division of the greater petrosal
nerve can be performed to alleviate symptoms by preventing the misdirected
signals to the lacrimal gland.
Botulinum Toxin Injections: Administering botulinum
toxin into the lacrimal glands can help reduce excessive tearing by
temporarily paralyzing the gland.
Myocardial infarction (MI)—heart attack
General Pathology
Myocardial infarction (MI)—heart attack
A. Ischemia versus MI: Ischemia is a reversible mismatch between the supply and demand of oxygen. Infarction
is an irreversible mismatch that results in cell death caused by the lack of blood flow (oxygenation). For instance, chest pain caused by ischemia can be relieved by administering nitroglycerin (a vasodilator) to the patient. If the patient has an MI, the pain will not be relieved with nitroglycerin.
1. MIs most commonly occur when a coronary artery is occluded by a thrombus generated in an atherosclerotic artery.
2. Symptoms include:
a. Chest pain, shortness of breath.
b. Diaphoresis (sweating), clammy hands.
c. Nausea, vomiting.
3. Consequences:
a. Death (one third of patients).
b. Arrhythmias (most common immediate cause of death).
c. Congestive heart failure.
d. Myocardial rupture, which may result in death from cardiac tamponade.
e. Thrombus formation on infarcted tissue; may result in systemic embolism.
Ethosuximide
Pharmacology
Ethosuximide (Zarontin): use in absence seizures (may exacerbate tonic-clonic seizures)
Mechanism: ↓ T-type Ca currents in thalamic neurons, inhibits bursts of APs, ↓ synchronous neuronal firing
i. Thalamo-cortical reverberating circuits: during absence type seizures, have reverberating circuits between cerebral cortex and thalamus at 3 Hz maintained by T-type Ca channels (since blocking these channels blocks the reverberating circuit)
Side effects: quite non-toxic; common= N/V and anorexia; less common = headache, sedation, photophobia
Muscles of the Soft Palate
AnatomyMuscles of the Soft Palate
The Levator Veli Palatini (Levator Palati)
Superior attachment: cartilage of the auditory tube and petrous part of temporal bone.
Inferior attachment: palatine aponeurosis.
Innervation: pharyngeal branch of vagus via pharyngeal plexus.
This cylindrical muscle runs inferoanteriorly, spreading out in the soft palate, where it attaches to the superior surface of the palatine aponeurosis.
It elevates the soft palate, drawing it superiorly and posteriorly.
It also opens the auditory tube to equalise air pressure in the middle ear and pharynx.
The Tensor Veli Palatini (Tensor Palati)
Superior attachment: scaphoid fossa of medial pterygoid plate, spine of sphenoid bone, and cartilage of auditory tube.
Inferior attachment: palatine aponeurosis.
Innervation: medial pterygoid nerve (a branch of the mandibular nerve).
This thin, triangular muscle passes inferiorly, and hooks around the hamulus of the medial pterygoid plate.
It then inserts into the palatine aponeurosis.
This muscle tenses the soft palate by using the hamulus as a pulley.
It also pulls the membranous portion of the auditory tube open to equalise air pressure of the middle ear and pharynx.
The Palatoglossus Muscle
Superior attachment: palatine aponeurosis.
Inferior attachment: side of tongue.
Innervation: cranial part of accessory nerve (CN XI) through the pharyngeal branch of vagus (CN X) via the pharyngeal plexus.
This muscle, covered by mucous membrane, forms the palatoglossal arch.
The palatoglossus elevates the posterior part of the tongue and draws the soft palate inferiorly onto the tongue.
Superior attachment: hard palatThe Palatopharyngeus Musclee and palatine aponeurosis.
Inferior attachment: lateral wall of pharynx.
Innervation: cranial part of accessory nerve (CN XI) through the pharyngeal branch of vagus (CN X) via the pharyngeal plexus.
This thin, flat muscle is covered with mucous membrane to form the palatopharyngeal arch.
It passes posteroinferiorly in this arch.
This muscle tenses the soft palate and pulls the walls of the pharynx superiorly, anteriorly and medially during swallowing.
The Musculus Uvulae
Superior attachment: posterior nasal spine and palatine aponeurosis.
Inferior attachment: mucosa of uvula.
Innervation: cranial part of accessory through the pharyngeal branch of vagus, via the pharyngeal plexus.
It passes posteriorly on each side of the median plane and inserts into the mucosa of the uvula.
When the muscle contracts, it shortens the uvula and pulls it superiorly.
Herpetic Gingivostomatitis
PedodonticsHerpetic Gingivostomatitis
Herpetic gingivostomatitis is an infection of the oral cavity caused by the
herpes simplex virus (HSV), primarily HSV type 1. It is characterized by
inflammation of the gingiva and oral mucosa, and it is most commonly seen in
children.
Etiology and Transmission
Causative Agent: Herpes simplex virus (HSV).
Transmission: The virus is communicated through
personal contact, particularly via saliva. Common routes include:
Direct contact with an infected individual.
Transmission from mother to child, especially during the neonatal
period.
Epidemiology
Prevalence: Studies indicate that antibodies to HSV are
present in 40-90% of individuals across different populations, suggesting
widespread exposure to the virus.
Age of Onset:
The incidence of primary herpes simplex infection increases after 6
months of age, peaking between 2 to 5 years.
Infants under 6 months are typically protected by maternal
antibodies.
Clinical Presentation
Incubation Period: 3 to 5 days following exposure to
the virus.
Symptoms:
General Symptoms: Fever, headache, malaise, and
oral pain.
Oral Symptoms:
Initial presentation includes acute herpetic gingivostomatitis,
with the gingiva appearing red, edematous, and inflamed.
After 1-2 days, small vesicles develop on the oral mucosa, which
subsequently rupture, leading to painful ulcers with diameters of
1-3 mm.
Course of the Disease
Self-Limiting Nature: The primary herpes simplex
infection is usually self-limiting, with recovery typically occurring within
10 days.
Complications: In severe cases, complications may
arise, necessitating hospitalization or antiviral treatment.
Treatment
Supportive Care:
Pain management with analgesics for fever and discomfort.
Ensuring adequate hydration through fluid intake.
Topical anesthetic ointments may be used to facilitate eating and
reduce pain.
Severe Cases:
Hospitalization may be required for severe symptoms or
complications.
Antiviral agents (e.g., acyclovir) may be administered in severe
cases or for immunocompromised patients.
Recurrence of Herpetic Infections
Reactivation: Recurrent herpes simplex infections are
due to the reactivation of HSV, which remains dormant in nerve tissue after
the primary infection.
Triggers for Reactivation:
Mucosal injuries (e.g., from dental treatment).
Environmental factors (e.g., sunlight exposure, citrus fruits).
Location of Recurrence: Recurrent infections typically
occur at the same site as the initial infection, commonly manifesting as
herpes labialis (cold sores).
Dental Burs: Design, Function, and Performance
Conservative DentistryDental Burs: Design, Function, and Performance
Dental burs are essential tools in operative dentistry, used for cutting,
shaping, and finishing tooth structure and restorative materials. This guide
will cover the key features of dental burs, including blade design, rake angle,
clearance angle, run-out, and performance characteristics.
1. Blade Design and Flutes
A. Blade Configuration
Blades and Flutes: Blades on a bur are uniformly
spaced, with depressed areas between them known as flutes. The design of the
blades and flutes affects the cutting efficiency and smoothness of the bur's
action.
Number of Blades:
The number of blades on a bur is always even.
Excavating Burs: Typically have 6-10 blades,
designed for efficient material removal.
Finishing Burs: Have 12-40 blades, providing a
smoother finish.
B. Cutting Efficiency
Smoother Cutting Action: A greater number of blades
results in a smoother cutting action at low speeds.
Reduced Efficiency: As the number of blades increases,
the space between subsequent blades decreases, leading to less surface area
being cut and reduced efficiency.
2. Vibration Characteristics
A. Vibration and Patient Comfort
Vibration Frequency: Vibrations over 1,300 cycles per
second are generally imperceptible to patients.
Effect of Blade Number: Fewer blades on a bur tend to
produce greater vibrations, which can affect patient comfort.
RPM and Vibration: Higher RPMs produce less amplitude
and greater frequency of vibration, contributing to a smoother experience
for the patient.
3. Rake Angle
A. Definition
Rake Angle: The angle that the face of the blade makes
with a radial line from the center of the bur to the blade.
B. Cutting Efficiency
Positive Rake Angle: Burs with a positive rake angle
are generally desired for cutting efficiency.
Rake Angle Hierarchy: The cutting efficiency is ranked
as follows:
Positive rake > Radial rake > Negative rake
Clogging: Burs with a positive rake angle may
experience clogging due to debris accumulation.
4. Clearance Angle
A. Definition
Clearance Angle: This angle provides clearance between
the working edge and the cutting edge of the bur, allowing for effective
cutting without binding.
5. Run-Out
A. Definition
Run-Out: Refers to the eccentricity or maximum
displacement of the bur head from its axis of rotation.
Acceptable Value: The average value of clinically
acceptable run-out is about 0.023 mm. Excessive run-out can lead to uneven
cutting and discomfort for the patient.
6. Load Characteristics
A. Load Applied by Dentist
Low Speed: The minimum and maximum load applied through
the bur is typically between 100 � 1500 grams.
High Speed: For high-speed burs, the load is generally
between 60 � 120 grams.
7. Diamond Stones
A. Abrasive Efficiency
Diamond Stones: These are the hardest and most
efficient abrasive stones available for removing tooth enamel. They are
particularly effective for cutting and finishing hard dental materials.