NDAEB Exam Prep Questions with Correct Answers , Graded to Pass

What two basic methods are used to acquire a digital x-ray image? - Direct imaging(sensor) & indirect imaging(PSP) Advantages of Digital Radiography - Immediate viewing of images, less radiation, no chemicals, ability to enhance images, communication with other dentists, no more lost films, remote consultation capability Disadvantages of Digital Radiography - Cost, converting previous records to digital, learning the computer software, thickness and rigidity of sensors, infection control What is intraoral film composed of? - Film Base - Clear Cellulose Acetate Thin Adhesive Layer Silver Halide Crystals - absorb radiation A protective layer to protect the emulsion surface. What is a latent image? - The image on the film that is not yet visible because it has not been processed. What does 'film speed' refer to? - The amount of radiation that is required to produce a radiograph of standard density. True or false: The larger the silver halide crystals, the faster the film speed? - True What is the fastest film speed currently available? - F-Speed. (It reduces patient exposure to radiation by 20-60% compared to E or D speed film) What are the 3 types of x-ray film used in dental radiography? - Intraoral film, extraoral film, and duplicating film. When does a "Herringbone" pattern occur on dental film? - When it is placed in the mouth backwards. What are the 5 basic sizes that intraoral film comes in? - Child Size: 0 Narrow Anterior: 1 Adult Size: 2 Preformed bitewing: 3 (infrequently used) Occlusal: 4 What are two common extraoral radiographs taken? - Panoramic and Cephalometric. What is an intensifying screen? - A device that intensifies or increases the effect of radiation and thus decreases the amount of exposure time needed. It is coated with phosphor which gives off light when struck by x-radiation. What are the 5 steps in processing film? - 1. Developing (reduce the silver halide crystals into black metallic silver) 2. Rinsing (remove developer from film) 3. Fixing. (use an acidic solution to remove unexposed silver halide crystals) 4. Washing (wash the film) 5. Drying What are the two techniques that can be used for exposing intraloral images? - Bisecting & Paralleling 5 Basic Rules of the Paralleling Technique - 1. Placement: it must cover correct teeth to be examined 2. Position: it must be parallel to the long axis of the tooth. 3. Vertical Angulation: Central ray must be directed perpendicular to the receptor & tooth. 4. Horizontal Angulation: Central ray must be directed through the contact areas. 5. Central Ray: it must be centered on the receptor. Why is it important to have an 'exposure sequence' for receptor placement? - To ensure an area is not omitted or exposed twice. What occurs if the horizontal angulation is incorrect? - Overlapping of teeth. What two errors can occur if the vertical angulation is incorrect? - Foreshortened or elongated images. What qualities must an endodontic x-ray have? - Tooth centered on the image At least 5mm of bone visible beyond apex of the tooth The image is as anatomically accurate as possible Two methods of mounting radiographs are: - 1. Labial mounting method: radiographs placed in the mount with the raised dots facing up (as if the viewer is looking directly at the pt) 2. radiographs placed in the mount with the raised dots facing down (as if the viewer is inside the patients mouth looking out) Two types of panoramic machines are in use today: - Film-based imaging & direct digital imaging. The main difference is the image receptor, digital units use a sensory array rather than film. What is Cone Beam Computed Tomography? - Use of a cone-shaped x-ray beam to acquire three-dimensional information. What is a film grid? (used for extraoral imaging) - It is used to reduce the amount of scatter radiation that reaches an extraoral film during exposure. What is a Lateral Cephalometric Projection used for? - Used to evaluate facial growth and development, trauma, disease, and developmental abnormalities. It shows the bones of the face and skull as well as the soft tissue profile. What is a Posteroanterior Projection used for? - Used to evaluate facial growth and development, trauma, disease, and development abnormalities. It shows the frontal and ethmoid sinuses, the orbits, and the nasal cavities. What happens if a patient does not remove jewellery or metallic/radiodense objects from their head/neck? - Ghost images If a lead apron is incorrectly placed on a pt during a panoramic radiograph, what occurs? - "Lead Apron Artifact" a radiopaque cone-shaped artifact results. What happens if a patient's chin is positioned too high during a pan? - It will create a "reverse smile line" What happens if a patient's chin is positioned too low during a pan? - It will create an "exaggerated smile line" What are three types of stress and strain? - Tensile stress: pulls and stretches a material Ex. tug-of-war Compressive stress: pushes a material together. ex. chewing Shear stress: the breakdown of material as the result of something sliding over two areas. ex. cutting with scissors. What is amalgam alloy powder composed of? - Silver - gives it its strength. Tin - gives it workability and strength. Copper - gives it strength and resistance to corrosion. Zinc - to suppress oxidation.