NEET MDS Synopsis
Roxithromycin
Pharmacology
Roxithromycin
It is used to treat respiratory tract, urinary and soft tissue infections. Roxithromycin is derived from erythromycin, containing the same 14-membered lactone ring. However, an N-oxime side chain is attached to the lactone ring.
Roxithromycin has similar antimicrobial spectrum as erythromycin, but is more effective against certain gram-negative bacteria, particularly Legionella pneumophilae.
When taken before a meal, roxithromycin is very rapidly absorbed, and diffused into most tissues and Phagocytes Only a small portion of roxithromycin is metabolised. Most of roxithromycin is secreted unchanged into the bile and some in expired air
Nephritic syndrome
General Pathology
Nephritic syndrome
Characterized by inflammatory rupture of the glomerular capillaries, leaking blood into the urinary space.
Classic presentation: poststreptococcal glomerulonephritis. It occurs after a group A, β–hemolytic Streptococcus infection (e.g., strep throat.)
Caused by autoantibodies forming immune complexes in the glomerulus.
Clinical manifestations:
oliguria, hematuria, hypertension, edema, and azotemia (increased concentrations of serum urea nitrogen
and creatine).
Le Fort Fractures
Oral and Maxillofacial SurgeryLe Fort I Fracture
A horizontal fracture that separates the maxilla from the nasal and
zygomatic bones. It is also known as a "floating maxilla."
Signs and Symptoms:
Bilateral Periorbital Edema and Ecchymosis: Swelling
and bruising around the eyes (Raccoon eyes).
Disturbed Occlusion: Malocclusion due to displacement
of the maxilla.
Mobility of the Maxilla: The maxilla may move
independently of the rest of the facial skeleton.
Nasal Bleeding: Possible epistaxis due to injury to the
nasal mucosa.
CSF Rhinorrhea: If there is a breach in the dura mater,
cerebrospinal fluid may leak from the nose.
Le Fort II Fracture
A pyramidal fracture that involves the maxilla, nasal bones, and the
zygomatic bones. It is characterized by a fracture line that extends from
the nasal bridge to the maxilla and zygomatic arch.
Signs and Symptoms:
Bilateral Periorbital Edema and Ecchymosis: Swelling
and bruising around the eyes (Raccoon eyes).
Diplopia: Double vision due to involvement of the
orbital floor and potential muscle entrapment.
Enophthalmos: Posterior displacement of the eyeball
within the orbit.
Restriction of Globe Movements: Limited eye movement
due to muscle entrapment.
Disturbed Occlusion: Malocclusion due to displacement
of the maxilla.
Nasal Bleeding: Possible epistaxis.
CSF Rhinorrhea: If the dura is torn, cerebrospinal
fluid may leak from the nose.
Le Fort III Fracture
A craniofacial disjunction fracture that involves the maxilla, zygomatic
bones, and the orbits. It is characterized by a fracture line that separates
the entire midface from the skull base.
Signs and Symptoms:
Bilateral Periorbital Edema and Ecchymosis: Swelling
and bruising around the eyes (Raccoon eyes).
Orbital Dystopia: Abnormal positioning of the orbits,
often with an antimongoloid slant.
Diplopia: Double vision due to muscle entrapment or
damage.
Enophthalmos: Posterior displacement of the eyeball.
Restriction of Globe Movements: Limited eye movement
due to muscle entrapment.
Disturbed Occlusion: Significant malocclusion due to
extensive displacement of facial structures.
CSF Rhinorrhea: If there is a breach in the dura mater,
cerebrospinal fluid may leak from the nose or ears (CSF otorrhea).
Bleeding Over Mastoid Process (Battle’s Sign): Bruising
behind the ear may indicate a skull base fracture.
Springs in Orthodontics
OrthodonticsSprings in Orthodontics
Springs are essential components of removable orthodontic appliances,
playing a crucial role in facilitating tooth movement. Understanding the
mechanics of springs, their classifications, and their applications is vital for
effective orthodontic treatment.
Springs are active components of removable orthodontic appliances
that deliver forces to teeth and/or skeletal structures, inducing changes in
their positions.
Mechanics of Tooth Movement: To achieve effective tooth
movement, it is essential to apply light and continuous forces. Heavy forces
can lead to damage to the periodontium, root resorption, and other
complications.
Components of a Removable Appliance
A removable orthodontic appliance typically consists of three main
components:
Baseplate: The foundation that holds the appliance
together and provides stability.
Active Components: These include springs, clasps, and
other elements that exert forces on the teeth.
Retention Components: These ensure that the appliance
remains in place during treatment.
Springs as Active Components
Springs are integral to the active components of removable appliances. They
are designed to exert specific forces on the teeth to achieve desired movements.
Components of a Spring
Wire Material: Springs are typically made from
stainless steel or other resilient materials that can withstand repeated
deformation.
Shape and Design: The design of the spring influences
its force delivery and stability.
Classification of Springs
Springs can be classified based on various criteria:
1. Based on the Presence or Absence of Helix
Simple Springs: These springs do not have a helix and
are typically used for straightforward tooth movements.
Compound Springs: These springs incorporate a helix,
allowing for more complex movements and force applications.
2. Based on the Presence of Loop or Helix
Helical Springs: These springs feature a helical
design, which provides a continuous force over a range of motion.
Looped Springs: These springs have a looped design,
which can be used for specific tooth movements and adjustments.
3. Based on the Nature of Stability
Self-Supported Springs: Made from thicker gauge wire,
these springs can support themselves and maintain their shape during use.
Supported Springs: Constructed from thinner gauge wire,
these springs lack adequate stability and are often encased in a metallic
tube to provide additional support.
Applications of Springs in Orthodontics
Space Maintenance: Springs can be used to maintain
space in the dental arch during the eruption of permanent teeth.
Tooth Movement: Springs are employed to move teeth into
desired positions, such as correcting crowding or aligning teeth.
Retention: Springs can also be used in retainers to
maintain the position of teeth after orthodontic treatment.
Reaction- gypsum products
Dental Materials
Reaction
a. Calcium sulfate hemihydrate(one-half water) crystals dissolve and react with water
b. Calcium sulfate dihydrate(two waters) form and precipitate new crystals
c. Unreacted (excess) water is left between crystals in solid
HISTOLOGIC CHANGES OF THE PULP
Dental Anatomy
HISTOLOGIC CHANGES OF THE PULP
Regressive changes
Pulp decreases in size by the deposition of dentin.
This can be caused by age, attrition, abrasion, operative procedures, etc.
Cellular organelles decrease in number.
Fibrous changes
They are more obvious in injury rather than aging. Occasionally, scarring may also be apparent.
Pulpal stones or denticles
They can be: a)free, b)attached and/or c)embedded. Also they are devided in two groups: true or false. The true stones (denticles) contain dentinal tubules. The false predominate over the the true and are characterized by concentric layers of calcified material.
Diffuse calcifications
Calcified deposits along the collagen fiber bundles or blood vessels may be observed. They are more often in the root canal portion than the coronal area.
Histology of the Cementum
Cementum is a hard connective tissue that derives from ectomesenchyme.
Embryologically, there are two types of cementum:
Primary cementum: It is acellular and develops slowly as the tooth erupts. It covers the coronal 2/3 of the root and consists of intrinsic and extrinsic fibers (PDL).
Secondary cementum: It is formed after the tooth is in occlusion and consists of extrinsic and intrinsic (they derive from cementoblasts) fibers. It covers mainly the root surface.
Functions of Cementum
It protects the dentin (occludes the dentinal tubules)
It provides attachment of the periodontal fibers
It reverses tooth resorption
Cementum is composed of 90% collagen I and III and ground substance.
50% of cementum is mineralized with hydroxyapatite. Thin at the CE junction, thicker apically.
Unicystic Ameloblastoma
Oral and Maxillofacial SurgeryUnicystic Ameloblastoma
Unicystic ameloblastoma is a specific type of ameloblastoma
characterized by a single cystic cavity that exhibits ameloblastomatous
differentiation in its lining. This type of ameloblastoma is distinct from other
forms due to its unique clinical, radiographic features, and behavior.
Characteristics of Unicystic Ameloblastoma
Definition:
Unicystic ameloblastoma is defined as a single cystic cavity that
shows ameloblastomatous differentiation in the lining.
Clinical Features:
More than 90% of unicystic ameloblastomas are found in the posterior
mandible.
They typically surround the crown of an unerupted mandibular third
molar and may resemble a dentigerous cyst.
Radiographic Features:
Appears as a well-defined radiolucent lesion, often associated with
the crown of an impacted tooth.
Histopathology:
There are three types of unicystic ameloblastomas:
Luminal: The cystic lining shows
ameloblastomatous changes without infiltration into the wall.
Intraluminal: The tumor is located within the
cystic cavity but does not infiltrate the wall.
Mural: The wall of the lesion is infiltrated by
typical follicular or plexiform ameloblastoma. This type behaves
similarly to conventional ameloblastoma and requires more aggressive
treatment.
Recurrence Rate:
Unicystic ameloblastomas, particularly those without mural
extension, have a low recurrence rate following conservative treatment.
Treatment of Ameloblastomas
Conventional (Follicular) Ameloblastoma:
Surgical Resection: Recommended with 1.0 to 1.5 cm
margins and removal of one uninvolved anatomic barrier.
Enucleation and Curettage: If used, this method has
a high recurrence rate (70-85%).
Unicystic Ameloblastoma (Without Mural Extension):
Conservative Treatment: Enucleation and curettage
are typically successful due to the intraluminal location of the tumor.
Unicystic Ameloblastoma (With Mural Extension):
Aggressive Treatment: Managed similarly to
conventional ameloblastomas due to the infiltrative nature of the mural
component.
Intraosseous Solid and Multicystic Ameloblastomas:
Mandibular Excision: Block resection is performed,
either with or without continuity defect, removing up to 1.5 cm of
clinically normal bone around the margin.
Peripheral Ameloblastoma:
Simple Excision: These tumors are less aggressive
and can be treated with simple excision, ensuring a rim of soft tissue
tumor-free margins (1-1.5 cm).
If bone involvement is indicated by biopsy, block resection with
continuity defect is preferred.
Recurrent Ameloblastoma:
Recurrences can occur 5-10 years after initial treatment and are
best managed by resection with 1.5 cm margins.
Resection should be based on initial radiographs rather than those
showing recurrence.
POLYCARBOXYLATE CEMENT
Dental Materials
POLYCARBOXYLATE CEMENT
Use:. The primary use of polycarboxylate cement is as a cementing medium of cast alloy and porcelain restorations. In addition, it can be used as a cavity liner, as a base under metallic restorations, or as a temporary restorative material.
Clinical Uses
Polycarboxylate cement is used in the same way as zinc phosphate cement, both as an intermediate base and as a cementing medium.
c. Chemical Composition.
(1) Powder:. It generally contains zinc oxide, 1 to 5 percent magnesium oxide, and 10 to 40 percent aluminum oxide or other reinforcing fillers. A small percentage of fluoride may be included.
(2) Liquid. Polycarboxylate cement liquid is approximately a 40 percent aqueous solution of polyacrylic acid copolymer with other organic acids such as itaconic acid. Due to its high molecular weight, the solution is rather thick (viscous).
d. Properties.
The properties of polycarboxylate cement are identical to those of zinc phosphate cement with one exception. Polycarboxylate cement has lower compressive strength.
e. Setting Reactions:
The setting reaction of polycarboxylate cement produces little heat. This has made it a material of choice. Manipulation is simpler, and trauma due to thermal shock to the pulp is reduced. The rate of setting is affected by the powder-liquid ratio, the reactivity of the zinc oxide, the particle size, the presence of additives, and the molecular weight and concentration of the polyacrylic acid. The strength can be increased by additives such as alumina and fluoride. The zinc oxide reacts with the polyacrylic acid forming a cross-linked structure of zinc polyacrylate. The set cement consists of residual zinc oxide bonded together by a gel-like matrix.
Precautions.
The following precautions should be observed.
o The interior of restorations and tooth surfaces must be free of saliva.
o The mix should be used while it is still glossy, before the onset of cobwebbing.
o The powder and liquid should be stored in stoppered containers under cool conditions. Loss of moisture from the liquid will lead to thickening.