Course -MDS

Digital Radiology


Digital Radiology

Advances in computer and X-ray technology now permit the use of systems that employ sensors in place of X-ray films (with emulsion). The image is either directly or indirectly converted into a digital representation that is displayed on a computer screen. 

DIGITAL IMAGE RECEPTORS

- charged coupled device (CCD) used
- Pure silicon divided into pixels.
- Electromagnetic energy from visible light or X-rays interacts with pixels to create an electric charge that can be stored.
- Stored charges are transmitted electronically and create an analog output signal and displayed via digital converter (analog to digital converter). 

ADVANTAGES OF DIGITAL TECHNIQUE

Immediate display of images.

Enhancement of image (e.g., contrast, gray scale, brightness).

Radiation dose reduction up to 60%.

Major disadvantage: High initial cost of sensors. Decreased image resolution and contrast as compared to D speed films.

DIRECT IMAGING

- CCD or complementary metal oxide semiconductor (CMOS) detector used that is sensitive to electromagnetic radiation.

- Performance is comparable to film radiography for detection of periodontal lesions and proximal caries in noncavitated teeth.

INDIRECT IMAGING

- Radiographic film is used as the image receiver (detector). 

- Image is digitized from signals created by a video device or scanner that views the radiograph.

 

Sensors

STORAGE PHOSPHOR IMAGING SYSTEMS

Phosphor screens are exposed to ionizing radiation which excites BaFBR:EU+2 crystals in the screen storing the image.

A computer-assisted laser then promotes the release of energy from the crystals in the form of blue light.

The blue light is scanned and the image is reconstructed digitally.

ELECTRONIC SENSOR SYSTEMS

X-rays are converted into light which is then read by an electronic sensor such as a CCD or CMOS.

Other systems convert the electromagnetic radiation directly into electrical impulses.

Digital image is created out of the electrical impulses. 

 

Zirconia Crowns


Zirconia Crowns

Dental zirconia is zirconium dioxide (ZrO2), which is a powdered form of zirconium

Types of Zirconia used

- Yttrium cation-doped tetragonal zirconia polycrystals.

- Magnesium cation-doped partially stabilized zirconia.

- Zirconia toughened alumina.

 

Indications:


Anterior Crowns – better aesthetics, prevents gingival discoloration commonly seen in PFM or metal ceramic crowns.

Non Vital or Fluorosis affected anterior teeth with discoloration – Ceramic crowns tend to show the underlying discoloration in such teeth whereas due to the opacity of Zirconia the severe discoloration is masked.

Bruxism patients complaining of frequent chip off of ceramic seen in high stress areas (posterior teeth). Monolithic Zirconia crowns are best suited for these regions whereas Porcelain used to zirconia are not indicated.

Patients allergic to other substances, as Zirconia is 100% bio-compatible and non allergic with no reported cases or allergy reported so far.

Short teeth where less tooth removal should be done, Zirconia crowns require less tooth removal when compared to other crowns.

High Strength: Monolith or Solid Zirconia crowns have high flexural strength of 1200 MPa


Contra-indications:

Expensive: The first factor which makes patients reject this material is the cost, it is much costlier than it counterpart the PFM crown.

Wear opposing teeth: If given in patients with bruxism or grinding of teeth, due to the high strength they can wear out the opposing natural tooth.

Cantilever Pontic: These are not indicated in Cantilever cases where a single tooth is taken as an abudment to replace a missing tooth.
When Abutment is Mobile

Zirconium crown is not indicated in Abutment tooth whose height less than 4mm

Cori Cycle


Cori Cycle

The Cori Cycle operates during exercise, when aerobic metabolism in muscle cannot keep up with energy needs.

For a brief burst of ATP utilization, muscle cells utilize ~P stored as phosphocreatine. For more extended exercise, ATP is mainly provided by Glycolysis.

Lactate, produced from pyruvate, passes via the blood to the liver where it is converted to glucose. The glucose may travel back to the muscle to fuel Glycolysis.

The Cori Cycle costs 6 P in liver for every 2P made available in muscle. The net cost is 4 P Although costly in terms of "high energy" bonds, the Cori Cycle allows the organism to accommodate to large fluctuations in energy needs of skeletal muscle between rest and exercise.

Anti-Diuretic Hormone Feedback


An anti-diruetic is a substance that decreases urine volume, and ADH is the primary example of it within the body. ADH is a hormone secreted from the posterior pituitary gland in response to increased plasma osmolarity (i.e., increased ion concentration in the blood), which is generally due to an increased concentration of ions relative to the volume of plasma, or decreased plasma volume.

The increased plasma osmolarity is sensed by osmoreceptors in the hypothalamus, which will stimulate the posterior pituitary gland to release ADH. ADH will then act on the nephrons of the kidneys to cause a decrease in plasma osmolarity and an increase in urine osmolarity.

ADH increases the permeability to water of the distal convoluted tubule and collecting duct, which are normally impermeable to water. This effect causes increased water reabsorption and retention and decreases the volume of urine produced relative to its ion content.

After ADH acts on the nephron to decrease plasma osmolarity (and leads to increased blood volume) and increase urine osmolarity, the osmoreceptors in the hypothalamus will inactivate, and ADH secretion will end. Due to this response, ADH secretion is considered to be a form of negative feedback.

Pulmonary embolism


Pulmonary embolism

A pulmonary embolism (thromboembolism) occurs when a blood clot, generally a venous thrombus, becomes dislodged from its site of formation and embolizes to the arterial blood supply of one of the lungs.

Clinical presentation

Signs of PE are sudden-onset dyspnea (shortness of breath, 73%), tachypnea (rapid breathing, 70%), chest pain of "pleuritic" nature (worsened by breathing, 66%), cough (37%), hemoptysis (coughing up blood, 13%), and in severe cases, cyanosis, tachycardia (rapid heart rate), hypotension, shock, loss of consciousness, and death. Although most cases have no clinical evidence of deep venous thrombosis in the legs, findings that indicate this may aid in the diagnosis.

Diagnosis

The gold standard for diagnosing pulmonary embolism (PE) is pulmonary angiography

An electrocardiogram may show signs of right heart strain or acute cor pulmonale in cases of large PEs

In massive PE, dysfunction of the right side of the heart can be seen on echocardiography, an indication that the pulmonary artery is severely obstructed and the heart is unable to match the pressure.

Treatment

Acutely, supportive treatments, such as oxygen or analgesia

In most cases, anticoagulant therapy is the mainstay of treatment. Heparin or low molecular weight heparins are administered initially, while warfarin therapy is given

Enzyme Kinetics


Enzyme Kinetics

Enzymes are protein catalysts that, like all catalysts, speed up the rate of a chemical reaction without being used up in the process. They achieve their effect by temporarily binding to the substrate and, in doing so, lowering the activation energy needed to convert it to a product.

The rate at which an enzyme works is influenced by several factors, e.g.,

  • the concentration of substrate molecules (the more of them available, the quicker the enzyme molecules collide and bind with them). The concentration of substrate is designated [S] and is expressed in unit of molarity.
  • the temperature. As the temperature rises, molecular motion - and hence collisions between enzyme and substrate - speed up. But as enzymes are proteins, there is an upper limit beyond which the enzyme becomes denatured and ineffective.
  • the presence of inhibitors.
    • competitive inhibitors are molecules that bind to the same site as the substrate - preventing the substrate from binding as they do so - but are not changed by the enzyme.
    • noncompetitive inhibitors are molecules that bind to some other site on the enzyme reducing its catalytic power.
  • pH. The conformation of a protein is influenced by pH and as enzyme activity is crucially dependent on its conformation, its activity is likewise affected.

The study of the rate at which an enzyme works is called enzyme kinetics.

Movements of the Temporomandibular Joint

Movements 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

Chronic lymphocytic leukaemia


Chronic lymphocytic leukaemia

Commoner in middle age. It starts insidiously and often runs a long chronic course

Features:

- Lymphnode enlargement.
- Anaemia (with haemolytic element).
- Moderate splenomegaly.
- Haemorrhagic tendency in late stages.
- Infection.

Blood picture:

- Anaemia with features of haemolytic anaemia
- Total leucocytic count of 50-100,OOO/cu.mm.
- Upto 90-95% cells are lymphocytes and prolymphocytes.
- Thrombocytopenia may be seen.

Bone marrow.  Lymphocytic series cells-are seen. Cells of other series are reduced,
 

Larynx

3 basic functions
o    protection of respiratory tract during swallowing food/air pathways cross.
    epiglottis provides protection
o    control intra-thoracic pressure (in coughing) -    close off airway to build pressure then rapidly open to release stuff
o    production of sound (in speaking, singing, laughing)

Important structures

o    hyoid bone
o    thyroid cartilage
o    arytenoids cartilage: vocal and muscle process
    sits on slope on posterior side of cricoid - spin and slide
o    cricoid cartilage: signet ring
o    thyroepiglottic ligament

Membranes and ligaments

o    membrane: general; ligament: thickening of membrane
o    folds: free edges of membranes or ligaments
o    names: tell you where located

Important membranes:
    quandrangular/vestibular membrane—from epiglottis to arytenoids
•    inferior edge: false vocal fold
    thyrohyoid membrane
    conus elasticus = cricothyroid = cricovocal
•    superior/medial edge = vocal fold
•    vocal ligaments: true folds, top of cricothyroid membrane

Plasma

Plasma:  is the straw-colored liquid in which the blood cells are suspended.

Composition of blood plasma

Component

Percent

Water

~92

Proteins

6–8

Salts

0.8

Lipids

0.6

Glucose (blood sugar)

0.1

Plasma transports materials needed by cells and materials that must be removed from cells:

  • various ions (Na+, Ca2+, HCO3, etc.
  • glucose and traces of other sugars
  • amino acids
  • other organic acids
  • cholesterol and other lipids
  • hormones
  • urea and other wastes

Most of these materials are in transit from a place where they are added to the blood

  • exchange organs like the intestine
  • depots of materials like the liver

to places where they will be removed from the blood.

  • every cell
  • exchange organs like the kidney, and skin.