NEET MDS Synopsis
Digital X-Ray
PedodonticsDigital X-Ray Systems in Pediatric Dentistry
Digital x-ray systems have revolutionized dental imaging, providing numerous
advantages over traditional film-based radiography. Understanding the technology
behind these systems, particularly in the context of pediatric patients, is
essential for dental professionals.
1. Digital X-Ray Technology
Solid State Detector Technology:
Digital x-ray systems utilize solid-state detector technology,
primarily through Charge-Coupled Devices (CCD) or Complementary
Metal Oxide Semiconductors (CMOS) for image acquisition.
These detectors convert x-ray photons into electronic signals, which
are then processed to create digital images.
2. Challenges with Wired Sensors in Young Children
Tolerability Issues:
Children under 4 or 5 years of age may have difficulty tolerating
wired sensors due to their limited understanding of the procedure.
The presence of electronic wires can lead to:
Fear or anxiety about the procedure.
Physical damage to the cables, as young children may "chew" on
them or pull at them during the imaging process.
Recommendation:
For these reasons, a phosphor-based digital x-ray system may
be more suitable for pediatric patients, as it minimizes the discomfort
and potential for damage associated with wired sensors.
3. Photostimulable Phosphors (PSPs)
Definition:
Photostimulable phosphors (PSPs), also known as storage phosphors,
are used in digital imaging for image acquisition.
Functionality:
Unlike traditional panoramic or cephalometric screen materials, PSPs
do not fluoresce instantly to produce light photons.
Instead, they store incoming x-ray photon information as a latent
image, similar to conventional film-based radiography.
Image Processing:
After exposure, the plates containing the stored image are scanned
by a laser beam in a drum scanner.
The laser excites the phosphor, releasing the stored energy as an
electronic signal.
This signal is then digitized, with various gray levels assigned to
points on the curve to create the final image.
4. Available Phosphor Imaging Systems
Several manufacturers provide phosphor imaging systems suitable for dental
practices:
Soredex: Digora
Air Techniques: Scan X
Gendex: Denoptix
Eosinopenia
General Pathology
Eosinopenia:
Causes
-Corticoid effect (Cushing's syndrome or therapy).
-Stress.
The Masseter Muscle
AnatomyThe Masseter Muscle
This is a quadrangular muscle that covers the lateral aspect of the ramus and the coronoid process of the mandible.
Origin: inferior border and medial surface of zygomatic arch.
Insertion: lateral surface of ramus of mandible and its coronoid process.
Innervation: mandibular nerve via masseteric nerve that enters its deep surface.
It elevates and protrudes the mandible, closes the jaws and the deep fibres retrude it.
RESPIRATORY DISORDERS - Emphysema
Physiology4. Emphysema
1. Permanent enlargement of airways with distension of alveolar walls
Thickened Bronchial Submucosa, Edema & Cellular Infiltration (loss of elasticity), Dilation of Air spaces, due to destruction of alveolar walls (Air trapped by obstruction)
2. Lower Respiratory tree destruction
Respiratory Bronchioles, Alveolar ducts, & Alveolar sacs
Types of Emphysema:
1. Centrilobular (Centriacinar) = Respiratory Bronchioles
Rarely seen in non Smokers, More in Men than Women, Found in Smokers with Bronchitis
2. Panlobular (Panacinar)
Hereditary, Single autosomal recessive gene. Deficient in 1-globulin (1-antitrypsin), Protects respiratory tract from neutrophil elastase (Enzyme that distroys lung connective tissue) , Aged persons, Results from Bronchi or Bronchiolar constriction
NOTE: Smoking = Leading cause of Bronchitis, Emphysema
Azithromycin
Pharmacology
Azithromycin
Azithromycin is the first macrolide antibiotic belonging to the azalide group. Azithromycin is derived from erythromycin by adding a nitrogen atom into the lactone ring of erythromycin A, thus making lactone ring 15-membered.
Azithromycin has similar antimicrobial spectrum as erythromycin, but is more effective against certain gram-negative bacteria, particularly Hemophilus influenzae.
azithromycin is acid-stable and can therefore be taken orally without being protected from gastric acids.
Main elimination route is through excretion in to the biliary fluid, and some can also be eliminated through urinary excretion
BETA-LACTAM ANTIBIOTICS
Pharmacology
Carbapenems: Broadest spectrum of beta-lactam antibiotics.
imipenem with cilastatin
meropenem
ertapenem
Monobactams: Unlike other beta-lactams, there is no fused ring attached to beta-lactam nucleus. Thus, there is less probability of cross-sensitivity reactions.
aztreonam
Beta-lactamase Inhibitors No antimicrobial activity. Their sole purpose is to prevent the inactivation of beta-lactam antibiotics by beta-lactamases, and as such, they are co-administered with beta-lactam antibiotics.
clavulanic acid
tazobactam
sulbactam
Pulmonary ventilation
PhysiologyVentilation simply means inhaling and exhaling of air from the atmospheric air into lungs and then exhaling it from the lung into the atmospheric air.
Air pressure gradient has to exist between two atmospheres to enable a gas to move from one atmosphere to an other.
During inspiration: the intrathoracic pressure has to be less than that of atmospheric pressure. This could be achieved by decreasing the intrathoracic pressure as follows:
Depending on Boyle`s law , the pressure of gas is inversely proportional to the volume of its container. So increasing the intrathoracic volume will decrease the intrathoracic pressure which will allow the atmospheric air to be inhaled (inspiration) . As decreasing the intrathoracic volume will increase the intrathoracic pressure and causes exhaling of air ( expiration)
So. Inspiration could be actively achieved by the contraction of inspiratory muscles : diaphragm and intercostal muscles. While relaxation of the mentioned muscles will passively cause expiration.
Contraction of diaphragm will pull the diaphragm down the abdominal cavity ( will move inferiorly) , and then increase the intrathoracic volume ( vertically) . Contraction of external intercostal muscle will pull the ribs upward and forward which will additionally increase the intrathoracic volume ( transversely , the net result will be increasing the intrathoracic volume and decreasing the intrathoracic pressure.
Relaxation of diaphragm will move it superiorly during expiration, the relaxation of external intercostal muscles will pull the ribs downward and backward , and the elastic lungs and chest wall will recoil. The net result is decreasing the intrathoracic volume and increasing intrathoracic pressure.
All of this occurs during quiet breathing. During forceful inspiration an accessory inspiratory muscle will be involved ( scaleni , sternocleidomastoid , and others) to increase negativity in the intrathoracic pressure more and more.
During forceful expiration the accessory expiratory muscles ( internal intercostal muscles and abdominal muscles ) will be involved to decrease the intrathoracic volume more and more and then to increase intrathoracic pressure more and more.
The pressure within the alveoli is called intralveolar pressure . Between the two phases of respiration it is equal to the atmospheric pressure. It is decreased during inspiration ( about 1 cm H2O ) and increased during expiration ( about +1 cm H2O ) . This difference allow entering of 0.5 L of air into the lungs.
Intrapleural pressure is the pressure of thin fluid between the two pleural layers . It is a slight negative pressure. At the beginning of inspiration it is about -5 cm H2O and reachs -7.5 cm H2O at the end or inspiration.
At the beginning of expiration the intrapleural pressure is -7.5 cm H2O and reaches -5 cmH2O at the end of expiration.
The difference between intralveolar pressure and intrapleural pressure is called transpulmonary pressure.
Factors , affecting ventilation :
Resistance : Gradual decreasing of the diameter of respiratory airway increase the resistance to air flow.
Compliance : means the ease , which the lungs expand.It depends on both the elastic forces of the lungs and the elastic forces , caused by the the surface tension of the fluid, lining the alveoli.
Surface tension: Molecules of water have tendency to attract each other on the surface of water adjacent to air. In alveoli the surface tension caused by the fluid in the inner surface of the alveoli may cause collapse of alveoli . The surface tension is decreased by the surfactant .
Surfactant is a mixture of phospholipids , proteins and ion m produced by type II pneumocytes.
Immature newborns may suffer from respiratory distress syndrome , due to lack of surfactant which is produced during the last trimester of pregnancy.
The elastic fibers of the thoracic wall also participate in lung compliance.
Pernicious anaemia
General Pathology
Pernicious anaemia
The special features are:
Due to intrinsic factor deficiency
Gastric atrophy with histamine fast achlorhydria
Genetic basis (racial distribution and blood group A).
Seen with auto immune disorders.
Antibodies to parietal cells and to intrinsic factors are seen