NEET MDS Synopsis
MAXILLARY CENTRAL INCISORS
Dental Anatomy
MAXILLARY CENTRAL INCISORS
Viewed mesially or distally, a maxillary central incisor looks like a wedge, with the point of the wedge at the incisal (cutting) edge of the tooth.
Facial Surface- The mesial margin is nearly straight and meets the incisal edge at almost a 90° angle, but the distal margin meets the incisal edge in a curve. The incisal edge is straight, but the cervical margin is curved like a half moon. Two developmental grooves are on the facial surface.
Lingual Surface:- The lingual aspect presents a distinctive lingual fossa that is bordered by mesial and distal marginal ridges, the incisal edge, and the prominent cingulum at the gingival. Sometimes a deep pit, the lingual pit, is found in conjunction with a cingulum.
Incisal: The crown is roughly triangular in outline; the incisal edge is nearly a straight line, though slightly crescent shaped
Contact Points: The mesial contact point is just about at the incisal, owing to the very sharp mesial incisal angle. The distal contact point is located at the junction of the incisal third and the middle third.
Root Surface:-As with all anterior teeth, the root of the maxillary central incisor is single. This root is from one and one-fourth to one and one-half times the length of the crown. Usually, the apex of the root is inclined slightly distally.
Procoagulant Drugs
Pharmacology
Procoagulant Drugs:
Desmospressin Acetate
• Is a synthetic analogue of the pituitary antidiuretic hormone (ADH).
• Stimulates the activity of Coagulation Factor VIII
• Use for treatment of hemophilia A with factor VIII levels less than or equal to 5%, treatment of hemophilia B or in clients who have factor VIII antibodies. Treatment of severe classic von Willebrand's disease (type I) and when an abnormal molecular form of factor VIII antigen is present. Use for type IIB von Willebrand's disease.
Cherubism
PedodonticsCherubism
Cherubism is a rare genetic disorder characterized by bilateral or asymmetric
enlargement of the jaws, primarily affecting children. It is classified as a
benign fibro-osseous condition and is often associated with distinctive
radiographic and histological features.
Clinical Presentation
Jaw Enlargement:
Patients may present with symmetric or asymmetric enlargement of the
mandible and/or maxilla, often noticeable at an early age.
The enlargement can lead to facial deformities and may affect the
child's appearance and dental alignment.
Tooth Eruption and Loss:
Teeth in the affected areas may exfoliate prematurely due to loss of
support, root resorption, or interference with root development in
permanent teeth.
Spontaneous loss of teeth can occur, or children may extract teeth
themselves from the soft tissue.
Radiographic Features
Bone Destruction:
Radiographs typically reveal numerous sharp, well-defined
multilocular areas of bone destruction.
There is often thinning of the cortical plate surrounding the
affected areas.
Cystic Involvement:
The radiographic appearance is often described as "soap bubble" or
"honeycomb" due to the multilocular nature of the lesions.
Case Report
Example: McDonald and Shafer reported a case involving
a 5-year-old girl with symmetric enlargement of both the mandible and
maxilla.
Radiographic Findings: Multilocular cystic
involvement was observed in both the mandible and maxilla.
Skeletal Survey: A complete skeletal survey did not
reveal similar lesions in other bones, indicating the localized nature
of cherubism.
Histological Features
Microscopic Examination:
A biopsy of the affected bone typically shows a large number of
multinucleated giant cells scattered throughout a cellular stroma.
The giant cells are large, irregularly shaped, and contain 30-40
nuclei, which is characteristic of cherubism.
Pathophysiology
Genetic Basis: Cherubism is believed to have a genetic
component, often inherited in an autosomal dominant pattern. Mutations in
the SH3BP2 gene have been implicated in the condition.
Bone Remodeling: The presence of giant cells suggests
an active process of bone remodeling and resorption, contributing to the
characteristic bone changes seen in cherubism.
Management
Monitoring: Regular follow-up and monitoring of the
condition are essential, especially during periods of growth.
Surgical Intervention: In cases where the enlargement
causes significant functional or aesthetic concerns, surgical intervention
may be considered to remove the affected bone and restore normal contour.
Dental Care: Management of dental issues, including
premature tooth loss and alignment problems, is crucial for maintaining oral
health.
Buffers
Biochemistry
Buffers
• Biological systems use buffers to maintain pH.
• Definition: A buffer is a solution that resists a significant change in pH upon addition of an acid or a base.
• Chemically: A buffer is a mixture of a weak acid and its conjugate base
• Example: Bicarbonate buffer is a mixture of carbonic acid (the weak acid) and the bicarbonate ion (the conjugate base): H2CO3 + HCO3 –
• All OH- or H+ ions added to a buffer are consumed and the overall [H+ ] or pH is not altered
H2CO3 + HCO3 - + H+ <- -> 2H2CO3
H2CO3 + HCO3 - + OH- <- -> 2HCO3 - + H2O
• For any weak acid / conjugate base pair, the buffering range is its pKa +1.
It should be noted that around the pKa the pH of a solution does not change appreciably even when large amounts of acid or base are added. This phenomenon is known as buffering. In most biochemical studies it is important to perform experiments, that will consume H+ or OH- equivalents, in a solution of a buffering agent that has a pKa near the pH optimum for the experiment.
Most biologic fluids are buffered near neutrality. A buffer resist a pH change and consists of a conjugate acid/base pair.
Important Physiological Buffers include carbonate (H2CO3/HCO3-),
Phosphate (H2PO-4 /HPO2-4) and various protiens
Surgical Approaches in Oral and Maxillofacial Surgery
Oral and Maxillofacial SurgerySurgical Approaches in Oral and Maxillofacial Surgery
In the management of tumors and lesions in the oral and maxillofacial region,
various surgical approaches are employed based on the extent of the disease, the
involvement of surrounding structures, and the need for reconstruction. Below is
a detailed overview of the surgical techniques mentioned, along with their
indications and reconstruction options.
1. Marginal / Segmental / En Bloc Resection
Definition:
En Bloc Resection: This technique involves the complete
removal of a tumor along with a margin of healthy tissue, without disrupting
the continuity of the bone. It is often used for tumors that are
well-defined and localized.
Indications:
No Cortical Perforation: En bloc segmental resection is
indicated when there is no evidence of cortical bone perforation. This
allows for the removal of the tumor while preserving the structural
integrity of the surrounding bone.
Tumor Characteristics: This approach is suitable for
benign tumors or low-grade malignancies that have not invaded surrounding
tissues.
2. Partial Resection (Mandibulectomy)
Definition:
Mandibulectomy: This procedure involves the resection
of a portion of the mandible, typically performed when a tumor is present.
Indications:
Cortical Perforation: Mandibulectomy is indicated when
there is cortical perforation of the mandible. This means that the tumor has
invaded the cortical bone, necessitating a more extensive surgical approach.
Clearance Margin: A margin of at least 1 cm of
healthy bone is typically removed to ensure complete excision of the tumor
and reduce the risk of recurrence.
3. Total Resection (Hemimandibulectomy)
Definition:
Hemimandibulectomy: This procedure involves the
resection of one half of the mandible, including the associated soft
tissues.
Indications:
Perforation of Bone and Soft Tissue: Hemimandibulectomy
is indicated when there is both perforation of the bone and involvement of
the surrounding soft tissues. This is often seen in more aggressive tumors
or those that have metastasized.
Extensive Tumor Involvement: This approach is necessary
for tumors that cannot be adequately removed with less invasive techniques
due to their size or location.
4. Reconstruction
Following resection, reconstruction of the jaw is often necessary to restore
function and aesthetics. Several options are available for reconstruction:
a. Reconstruction Plate:
Description: A reconstruction plate is a rigid plate
made of titanium or other biocompatible materials that is used to stabilize
the bone after resection.
Indications: Used in cases where structural support is
needed to maintain the shape and function of the mandible.
b. K-wire:
Description: K-wires are thin, flexible wires used to
stabilize bone fragments during the healing process.
Indications: Often used in conjunction with other
reconstruction methods to provide additional support.
c. Titanium Mesh:
Description: Titanium mesh is a flexible mesh that can
be shaped to fit the contours of the jaw and provide support for soft tissue
and bone.
Indications: Used in cases where there is significant
bone loss and soft tissue coverage is required.
d. Rib Graft / Iliac Crest Graft:
Description: Autogenous bone grafts can be harvested
from the rib or iliac crest to reconstruct the mandible.
Indications: These grafts are used when significant
bone volume is needed for reconstruction, providing a biological scaffold
for new bone formation.
Biliary cirrhosis
General Pathology
Biliary cirrhosis(16%)
It is due diffuse chronic cholestaisis (obstruction of the biliary flow) leading to damage and scarring all over the liver. Two types are known
1. Primary biliary cirrhosis and
2. Secondary biliary cirrhosis.
Primary biliary cirrhosis
It is destructive chronic inflammation of intrahepatic bile ductules and small ducts leading to micronodular cirrhosis.
-Typically affects middle aged women.
- Patients present with fatigue, pruritis and eventually, jaundice.
Cause:- Autoimmune. Patients have autoantibodies directed against mitochondrial enzymes (AMA).
Pathology:-
Liver is enlarged, dark green in color (cholestaisis). Cirrhosis is micronodular.
M/E :-
- Early, portal tracts show lymphocytes and plasma cell infiltrate the bile ducts and destroy them.
- Granulomatous inflammation surrounding the damaged and inflamed bile ducts is the hallmark of (PBC).
- Cholestatic changes such as bile ductular proliferation, periportal Mallory’s hyaline and increased copper in periportal hepatocytes.
- In the end stage disease, micro nodular cirrhosis occurs and the inflammatory changes subside
Secondary biliary cirrhosis:-
It is extra hepatic (surgical) cholestaisis due to prolonged extra hepatic major bile duct obstruction.
Causes - Obstruction of hepatic or common bile duct by:
- Congenital biliary atresia.
- Pressure by enlarged LN or tumor * Biliary stones.
- Carcinoma of the bile duct, ampulla of Vater or pancreatic head
Effects of obstruction:-
Complete obstruction leads to back pressure all over the biliary tract
- damage by inspessated bile
- inflammation and scarring.
Incomplete obstruction leads to acute suppurative cholangitis and cholangiolitis.
The Lateral Wall of the Orbit
AnatomyThe Lateral Wall of the Orbit
This wall is thick, particularly its posterior part, which separates the orbit from the middle cranial fossa.
The lateral wall is formed by the frontal process of the zygomatic bone and the greater wing of the sphenoid bone.
Anteriorly, the lateral wall lies between the orbit and the temporal fossa.
The lateral wall is partially separated from the roof by the superior orbital fissure.
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