Week 1 Lecture Objectives Flashcards
Explain purpose of bitewing radiography
Early detection of interproximal dental caries
Ability to detect decay around margins of fillings
Accurate representation of bone level
List desired criteria for bitewings
All contacts open Film shows equal amounts of crowns Alveolar crest visible between all teeth No cone cutting Good density and contrast
What is an element?
Smallest particle of substance
What is an atom?
Smallest particles of an element
Discuss the components of the nucleus
The central, positively charged core of an atom; composed of protons and neutrons
Discuss the components of an electron
Tiny negatively charged particle found outside of the nucleus in the atom
Discuss the components of a proton
positively(+) charged particle with a mass of one
Discuss the components of a neutron
an electrically neutral or unchanged particle
Ionization
Ion ejected from shell (+ or -) causing it to be uneven
How are x-rays produced?
When high speed electrons are suddenly decelerated or brought to a stop
Some energy is converted into electromagnetic radiation or x-rays
What are the 4 conditions necessary for x-ray production?
- Generation of electrons
- Production of high speed electrons
- Focusing of electrons
- Sudden stoppage of electrons
Explain the process of generation of electrons
Electrical current heats cathode (made of tungsten and focusing cup)
Separation of electrons from tungsten filament
Boil off; called “thermionic emission”
Electron cloud – controlled by mA
Explain the production of high speed electrons
High voltage created between sides (kVp Kilovolt Peak)
“Boiled off” electrons sent from cathode to anode. Always in one direction, Negative to positive
Explain focusing the electrons
The focusing cup designed to direct the electrons to target spot (anode)
Explain sudden stoppage of electrons
Electrons hit hard solid anode –stopped abruptly
The efficiency of x-ray production is very low
What is tungsten?
A strong metal, a lot of electrons, retains shape and properties, high melting point
Explain Bremsstrahlung Radiation
Bombarding electron comes at a high speed and hits another electron of tungsten. It gets really close to the nucleus and the electron stops and veers off in another direction giving off a lot of heat and a little bit of x-ray.
Explain characteristic radiation
Bombarding electron comes at a high speed and hits another electron of tungsten. The electron knocks off a K-shell electron and ejects it.
How much kVp is needed to eject the electron from characteristic radiation?
70 kVp
Explain particulate radiation
Although extremely small, is still does possess mass
Does contain a charge
Alpha particles
Electrons (Beta particles and Cathode rays)
Explain electromagnetic radiation
Propagation of wavelike energy through space or mass at the speed of light
What is the wave concept of x-rays?
Wavelike energy which has no mass or charge and travels through space or matter at the speed of light
Wavelength
More waves if there is more power, length between each peak
Short wavelengths
Great penetration
High energy
High frequency
Long wavelengths
Low penetration
Low energy
Low frequency
Gets absorbed
Characteristics of x-rays
Behaves like light, invisible
Spread over distance like a beam of light
Travels in a straight line - even if it is wavelength
Penetrate materials that absorb or reflect visible light
Ionize atoms
Produce fluorescence of certain substances
Differentially absorbed by matter
Produce biologic changes
Where is the placement supposed to be for a premolar bite wing?
Far enough forward to see the distal of canine
Where is the placement supposed to be for a molar bite wing?
Far enough back to see the third molar space and the 2nd molar needs to be centered
When the electrons are stopped abruptly what does the kinetic energy of the electrons convert to?
99% is converted to heat energy
1% converted to x-radiation
What does incorrect vertical angulation cause?
Causing cusps to overlap
What are two types of electromagnetic radiation?
X-rays and gamma rays
Explain how gamma rays work (simply)
Emitted from the nucleus of radioactive atoms
