NEET MDS Synopsis
Movements of the Temporomandibular Joint
AnatomyMovements of the Temporomandibular Joint
The two movements that occur at this joint are anterior gliding and a hinge-like rotation.
When the mandible is depressed during opening of the mouth, the head of the mandible and articular disc move anteriorly on the articular surface until the head lies inferior to the articular tubercle.
As this anterior gliding occurs, the head of the mandible rotates on the inferior surface of the articular disc.
This permits simple chewing or grinding movements over a small range.
Movements that are seen in this joint are: depression, elevation, protrusion, retraction and grinding
Propoxyphene
Pharmacology
Propoxyphene
A methadone analog.Used orally to relieve mild to moderate pain.
A typical opiate, it does not possess anti-inflammatory or antipyretic actions, but has little or no antitussive activity.
Cannot be used parenterally because of irritant properties.
Has a low addiction potential primarily due to its lack of potency as an opiate.
The most common adverse side effects are:• dizziness, drowsiness, and nausea and vomiting. • these effects are more prominent in ambulatory patients.
Withdrawal symptoms have occurred in both adults and in neonates following use of the drug by the mother during pregnancy.
CNS depression is additive with other CNS depressants.
Nervous System - Viral Infections
General Pathology
Viral meningitis
1. Can be caused by many different viruses, including cytomegalovirus, herpes virus, rabies, and HIV.
2. CSF fluid from a spinal tap differs from that seen in a bacterial infection. It shows mononuclear cells, higher levels of protein, and normal levels of glucose.
Anesthesia Management in TMJ Ankylosis Patients
Oral and Maxillofacial Surgery
Anesthesia Management in TMJ Ankylosis Patients
TMJ ankylosis can lead to significant trismus (restricted mouth opening),
which poses challenges for airway management during anesthesia. This condition
complicates standard intubation techniques, necessitating alternative approaches
to ensure patient safety and effective ventilation. Here’s a detailed overview
of the anesthesia management strategies for patients with TMJ ankylosis.
Challenges in Airway Management
Trismus: Patients with TMJ ankylosis often have limited
mouth opening, making traditional laryngoscopy and endotracheal intubation
difficult or impossible.
Risk of Aspiration: The inability to secure the airway
effectively increases the risk of aspiration during anesthesia, particularly
if the patient has not fasted adequately.
Alternative Intubation Techniques
Given the challenges posed by trismus, several alternative methods for
intubation can be employed:
Blind Nasal Intubation:
This technique involves passing an endotracheal tube through the
nasal passage into the trachea without direct visualization.
It requires a skilled practitioner and is typically performed under
sedation or local anesthesia to minimize discomfort.
Indications: Useful when the oral route is not
feasible, and the nasal passages are patent.
Retrograde Intubation:
In this method, a guide wire is passed through the cricothyroid
membrane or the trachea, allowing for the endotracheal tube to be
threaded over the wire.
This technique can be particularly useful in cases where direct
visualization is not possible.
Indications: Effective in patients with limited
mouth opening and when other intubation methods fail.
Fiberoptic Intubation:
A fiberoptic bronchoscope or laryngoscope is used to visualize the
airway and facilitate the placement of the endotracheal tube.
This technique allows for direct visualization of the vocal cords
and trachea, making it safer for patients with difficult airways.
Indications: Preferred in cases of severe trismus
or anatomical abnormalities that complicate intubation.
Elective Tracheostomy
When the aforementioned techniques are not feasible or if the patient
requires prolonged ventilation, an elective tracheostomy may be performed:
Procedure: A tracheostomy involves creating an opening
in the trachea through the neck, allowing for direct access to the airway.
Cuffed PVC Tracheostomy Tube: A cuffed polyvinyl
chloride (PVC) tracheostomy tube is typically used. The cuff:
Seals the Trachea: Prevents air leaks and ensures
effective ventilation.
Self-Retaining: The cuff helps keep the tube in
place, reducing the risk of accidental dislodgment.
Prevents Aspiration: The cuff also minimizes the
risk of aspiration of secretions or gastric contents into the lungs.
Anesthesia Administration
Once the airway is secured through one of the above methods, general
anesthesia can be administered safely. The choice of anesthetic agents and
techniques will depend on the patient's overall health, the nature of the
surgical procedure, and the anticipated duration of anesthesia.
Maxillectomy
Oral and Maxillofacial SurgeryMaxillectomy
Maxillectomy is a surgical procedure involving the resection
of the maxilla (upper jaw) and is typically performed to remove tumors, treat
severe infections, or address other pathological conditions affecting the
maxillary region. The procedure requires careful planning and execution to
ensure adequate access, removal of the affected tissue, and preservation of
surrounding structures for optimal functional and aesthetic outcomes.
Surgical Access and Incision
Weber-Fergusson Incision:
The classic approach to access the maxilla is through the Weber-Fergusson
incision. This incision provides good visibility and access to
the maxillary region.
Temporary Tarsorrhaphy: The eyelids are temporarily
closed using tarsorrhaphy sutures to protect the eye during the
procedure.
Tattooing for Aesthetic Alignment:
To achieve better cosmetic results, it is recommended to tattoo the
vermilion border and other key points on both sides of the incision with
methylene blue. These points serve as guides for alignment during
closure.
Incision Design:
The incision typically splits the midline of the upper lip but can
be modified for better cosmetic outcomes by incising along the philtral
ridges and offsetting the incision at the vermilion border.
The incision is turned 2 mm from the medial canthus
of the eye. Intraorally, the incision continues through the gingival
margin and connects with a horizontal incision at the depth of the
labiobuccal vestibule, extending back to the maxillary tuberosity.
Continuation of the Incision:
From the maxillary tuberosity, the incision turns medially across
the posterior edge of the hard palate and then turns 90 degrees
anteriorly, several millimeters to the proximal side of the
midline, crossing the gingival margin again if possible.
Incision to Bone:
The incision is carried down to the bone, except beneath the lower
eyelid, where the orbicularis oculi muscle is
preserved. The cheek flap is then reflected back to the tuberosity.
Surgical Procedure
Extraction and Elevation:
The central incisor on the involved side is extracted, and the
gingival and palatal mucosa are elevated back to the midline.
Deepening the Incision:
The incision extending around the nose is deepened into the nasal
cavity. The palatal bone is divided near the midline using a saw blade
or bur.
Separation of Bone:
The basal bone is separated from the frontal process of the maxilla
using an osteotome. The orbicularis oculi muscle is retracted
superiorly, and the bone cut is extended across the maxilla, just below
the infraorbital rim, into the zygoma.
Maxillary Sinus:
If the posterior wall of the maxillary sinus has not been invaded by
the tumor, it is separated from the pterygoid plates using a pterygoid
chisel.
Specimen Removal:
The entire specimen is removed by severing the remaining attachments
with large curved scissors placed behind the maxilla.
Postoperative Considerations
Wound Care: Proper care of the surgical site is
essential to prevent infection and promote healing.
Rehabilitation: Patients may require rehabilitation to
address functional issues related to speech, swallowing, and facial
aesthetics.
Follow-Up: Regular follow-up appointments are necessary
to monitor healing and assess for any complications or recurrence of
disease.
Endocrine System
Physiology
The endocrine system along with the nervous system functions in the regulation of body activities. The nervous system acts through electrical impulses and neurotransmitters to cause muscle contraction and glandular secretion and interpretation of impulses. The endocrine system acts through chemical messengers called hormones that influence growth, development, and metabolic activities
CEMENTUM vs. BONE
Dental Anatomy
CEMENTUM vs. BONE
Cementum simulates bone
1) Organic fibrous framework, ground substance, crystal type, development
2) Lacunae
3) Canaliculi
4) Cellular components
5) Incremental lines (also known as "resting" lines; they are produced by continuous but phasic, deposition of cementum)
Differences between cementum and bone
1) Cementum is not vascularized
2) Cementum has minor ability to remodel
3) Cementum is more resistant to resorption compared to bone
4) Cementum lacks neural component
5) Cementum contains a unique proteoglycan interfibrillar substance
6) 70% of bone is made by inorganic salts (cementum only 46%)
Relation of Cementum to Enamel at the Cementoenamel Junction (CEJ)
"OMG rule"
In 60% of the teeth cementum Overlaps enamel
In 30% of the teeth cementum just Meets enamel
In 10% of the teeth there is a small Gap between cementum and enamel
Hypothalamic - Pituitary Drugs
Pharmacology
Hypothalamic - Pituitary Drugs
Somatropin
Growth hormone (GH) mimetic
Mechanism
agonist at GH receptors
increases production of insulin growth factor-1 (IGF-1)
Clinical use
GH deficiency
increase adult height for children with conditions associated with short stature
Turner syndrome
wasting in HIV infection
short bowel syndrome
Toxicity
scoliosis
edema
gynecomastia
increased CYP450 activity
Octreotide
Somatostatin mimetic
Mechanism
agonist at somatostatin receptors
Clinical use
acromegaly
carcinoid
gastrinoma
glucagonoma
acute esophageal variceal bleed
Toxicity
GI upset
gallstones
bradycardia
Oxytocin
Mechanism
agonist at oxytocin receptor
Clinical use
stimulation of labor
uterine contractions
control of uterine hemorrhage after delivery
stimulate milk letdown
Toxicity
fetal distress
abruptio placentae
uterine rupture
Desmopressin
ADH (vasopressin) mimetic
Mechanism
agonist at vasopressin V2 receptors
Clinical use
central (pituitary) diabetes insipidus
hemophilia A (factor VIII deficiency)
increases availability of factor VIII
von Willebrand disease
increases release of von Willebrand factor from endothelial cells
Toxicity
GI upset
headache
hyponatremia
allergic reaction