Dental Physics and Radiography

Question 1

Average max bite force

Answer 1

750N

Question 2

Posterior occlusal Bite forces (1st and 2nd molar
region):

what is special about this region?

Answer 2

400-800N

The region that faces the most force

Question 3

range of bite forces in adults

Answer 3

200-3500 N

Question 4

Tooth wear

Answer 4

a complex, multifactorial phenomenon with the interplay of

biological, mechanical, chemical and tribological factors

Question 5

amount of tooth wear is dependant on

4

Answer 5

factors such as muscular forces,

lubricants, patient diet habit and the type of restorative material used

Question 6

Types of Non Carious Tooth Loss

Answer 6

erosion, abrasion,attrition, abfraction

Question 7

attrition meaning and characteristics

Answer 7

gradual loss of tooth substance from occlusal contacts with opposing dentition

tooth to tooth wear

flat surface/anatomical features become indistinct

Question 8

abrasion meaning

Answer 8

loss of tooth substance through mechanical means such as harsh brushing technique, not relating to occlusion

effects usually seen near gingival margin

Question 9

Biting forces vary

Answer 9

patient age
dentition

decrreased with restored teeth or dentures

Question 10

3 types of intra oral radiography

Answer 10

bitewing radiograph

periapical radiograph

oclussal radiograph

Question 11

radiopaque

on film

Answer 11

white image dense

blocks xray beam

Question 12

radiolucent

Answer 12

black image

x ray beam has passed through

Question 13

bitewing

demonstrates (4)and techniques

Answer 13

caries,peridontal bone loss,crestal bone height and status of restorations

Film holder/ paper tab

Question 14

periapical radiograph

demonstates (3) and techniques

Answer 14

shows crown,root and periapical tissue

dentist can see thing such as:

• implant status
• root fractures
• periapical inflammation

bisecting angle/paralleling

Question 15

occlusal radiographs and what it

demonstrates(3)

Answer 15

uses largest intraoral film

demonstrates:
trauma
-fractures (fractures like alveolar bone fractures and even fragments of fracture can be seen)

• impacted teeth
• supernumeracy teeth

Question 16

when does ionisation occur?

Answer 16

occurs when an atom loses an electron which causes the nucleus to become a postive ion

Question 17

radiation

Answer 17

a transmission of energy through space and matter

Question 18

bemsstrahlung radiation
aka
braking radiation
70% of xrays in dental machines

Answer 18

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

Question 19

characteristic radiation

Answer 19

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

Question 20

3 steps to xray production

Answer 20

1. production of electrons at cathode
2. apply high energy to cathode so electrons accelerate and have high kinetic energy
3. electrons impact tungsten atoms creating x-rays

Question 21

properties of x ray photons (8)

Answer 21

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

Question 22

factors that can alter xray beam (5)

Answer 22

duration
exposure rate
energy
shape
intensity

Question 23

inverse square law

2x distance=1/4x readiation

Answer 23

For a given
beam, the intensity is inversely
proportional to the square of the
distance from the source

Question 24

3 ways x-rays interact with patient

Answer 24

1. xray pases through patient w/o interaction
2. xray photons absorbed by patient
3. x-ray photons are scattered (cohrent or incoherent scattering)

Question 25

biological effects of ionizing radiation (3)

Answer 25

1. somatic stochastic
2. somatic non-stochastic
3. genetic stochastic

Question 26

somatic stochastic(3)

Answer 26

no safe dose
every exposure has possiblity of causing effects
late signs
ex.leukaemia

Question 27

somatic non-stochastic (4)

Answer 27

deterministic
severity proportional to dose
has a threshold dose
early sign 
ex. cataract

Question 28

genetic stochastic(4)

Answer 28

repro organ have been irradiated

damge goes to repro cells

no safe threshold occurs

delayed effect occurs in (offspring)