Dental Physics and Radiography Flashcards
Intro to dental physics intraoral radiography radaition physics safety
Average max bite force
750N
Posterior occlusal Bite forces (1st and 2nd molar
region):
what is special about this region?
400-800N
The region that faces the most force
range of bite forces in adults
200-3500 N
Tooth wear
a complex, multifactorial phenomenon with the interplay of
biological, mechanical, chemical and tribological factors
amount of tooth wear is dependant on
4
factors such as muscular forces,
lubricants, patient diet habit and the type of restorative material used
Types of Non Carious Tooth Loss
erosion, abrasion,attrition, abfraction
attrition meaning and characteristics
gradual loss of tooth substance from occlusal contacts with opposing dentition
tooth to tooth wear
flat surface/anatomical features become indistinct
abrasion meaning
loss of tooth substance through mechanical means such as harsh brushing technique, not relating to occlusion
effects usually seen near gingival margin
Biting forces vary
patient age
dentition
decrreased with restored teeth or dentures
3 types of intra oral radiography
bitewing radiograph
periapical radiograph
oclussal radiograph
radiopaque
on film
white image dense
blocks xray beam
radiolucent
black image
x ray beam has passed through
bitewing
demonstrates (4)and techniques
caries,peridontal bone loss,crestal bone height and status of restorations
Film holder/ paper tab
periapical radiograph
demonstates (3) and techniques
shows crown,root and periapical tissue
dentist can see thing such as:
- implant status
- root fractures
- periapical inflammation
bisecting angle/paralleling
occlusal radiographs and what it
demonstrates(3)
uses largest intraoral film
demonstrates:
trauma
-fractures (fractures like alveolar bone fractures and even fragments of fracture can be seen)
- impacted teeth
- supernumeracy teeth
when does ionisation occur?
occurs when an atom loses an electron which causes the nucleus to become a postive ion
radiation
a transmission of energy through space and matter
bemsstrahlung radiation
aka
braking radiation
70% of xrays in dental machines
electrons sudden stopping or decrease in speed when it is close to the tungsten nuclei causes the electron to
lose kinetic energy which leads to the production of bremsstrahlung photons
characteristic radiation
occurs when an incident electron kicks out an inner orbit electron from the tungsten target
causing a space
the spcae gets filled by an electron from an outer orbit
later releasing a photon with energy equal to the difference in energy beteen two orbits
3 steps to xray production
- production of electrons at cathode
- apply high energy to cathode so electrons accelerate and have high kinetic energy
- electrons impact tungsten atoms creating x-rays
properties of x ray photons (8)
invisible
high energy and shortwavelengths
no mass/charge
travel at speed of light
travel in straight lines but can be scattered/deflected
cant focus on 1 point
can penetrate and be absorbed
cause biological damage
factors that can alter xray beam (5)
duration exposure rate energy shape intensity
inverse square law
2x distance=1/4x readiation
For a given
beam, the intensity is inversely
proportional to the square of the
distance from the source
3 ways x-rays interact with patient
- xray pases through patient w/o interaction
- xray photons absorbed by patient
- x-ray photons are scattered (cohrent or incoherent scattering)
biological effects of ionizing radiation (3)
- somatic stochastic
- somatic non-stochastic
- genetic stochastic
somatic stochastic(3)
no safe dose
every exposure has possiblity of causing effects
late signs
ex.leukaemia
somatic non-stochastic (4)
deterministic severity proportional to dose has a threshold dose early sign ex. cataract
genetic stochastic(4)
repro organ have been irradiated
damge goes to repro cells
no safe threshold occurs
delayed effect occurs in (offspring)
