radiography

clinicians main diagnostic aid primarily taken to determine the presence or absence of underlying hard tissue in diseases effecting the teeth and bones

Xray generating machine patient image receptor placed intra and extra orally

dense areas within an object that have totally stopped the X-ray beam

areas where the xray beam has passed through and not stopped

areas where the xray beam has stopped to a varying degree

specific type of material of object thickness/density of material shape of object type of image receptor intensity of the xray beam used position of object in relation to xray beam and image receptor

teeth and patients are 3d so a 2D image may provide limited or misleading information on where a structure lies and its shape the shadows are cast by different parts of the object which are superimposed by one another

contrast sharpness/resolution characteristics of the xray beam image geometry

the object and the image receptor need to be as close as possible. they should be parallel. the tube head needs to be positioned so that the beam meets both the object and the image receptor at a right angle

produced from a point of source parallel sufficiently penetrating

partial images contrast context

xray only provides a partial image in the form of different density shadows clinician needs to complete it and fill the gaps - every clinical does this differently so we arrive at different conclusions

a- increased exposure b- normal exposure c- reduced exposure

contrast between adjacent structures can alter the perceived density

environment can effect our perception of radiographs. patient has conditioned out perceptual apparatus

central dense nucleus made up of neutron and protons surrounded by electrons in differed orbits/shells

the number of protons in the nucleus of an atom

the number of neutrons in the nucleus of an atom

the sun of neutrons and protons in the nucleus of an atom

an atom with the same atomic number but a different atomic mass and number of neutrons

X-ray generating compound - tube head. tube head contains a small evacuated glass container that is called the xray tube. the xray tube produces X-rays so when at a high speed they bombard the target and are attenuated and bought to a sudden rest

tungsten filament is ductile, thermionic emitter, can withstand high temperatures and gives off a lot of electrons

negative and it is the source of electrons

positive and it absorbs electrons and creates xrays

contains electrons and allows them to beam towards the anode

aborb/removes heat

angles directly to target for electrons to reach

lead casing oil to absorb excess heat

has a heated filament of tungsten that provides source of electrons

has a target that is directly set into the angled face of the copper block to allow for the removal of heat

aims the stream of electrons at the focal spot of the target

connected between the cathode and the anode and accelerated electrons from the negative filament to the positive target

flow between the cathode and anode. it is a measure of quantity of electrons being accelerated

it absorbs unwanted X-rays as a radiation protection measure because the X-rays get emitted in all directions

facilitates the removal of heat

1) the filament is heated electronically 2) a cloud of electrons are formed 3) the high voltage across the tube accelerates the electrons at high speed towards the anode 4) the focusing device directs the electrons to the focal spot on the target 5) electrons bombard the target and are then attenuated and bought to a sudden rest 7) heat and xrays are divided 8) heat is removed 9) X-rays pass through the lead casing window

incoming electrons are deflected by the outer shell with small loss of energy in the form of heat incoming electrons collide with outer shell tungsten electrons

incoming electrons penetrate outer shell electrons. incoming electrons pass close to the nucleus of the tungsten atom and are then slowed down and deflected. energy is lost in the form of X-rays

continuous and characteristic xray production

breaking radiation - X-ray photons are emitted by rapid deacceleration of bombarding electrons close to the nucleus of the tungsten atom. the amount of deflection determines the outcome of energy lost by bombarding electrons

high energy electrons collide with inner shell electrons both ejected from the tungsten atom which leaves a hole in the inner layer hole filled with outer shell electrons causes loss of energy emitted as a xray photon

k line - used for diagnosis and has a minimal voltage of 69kv l line - doesn’t have enough energy and is unable to reach the minimum

wave packets of energy of electromagnetic radiation

a quantum of energy caused by a photon

size of voltage size od tube current distance from target time filtration target material

1) completely scatted with no loss of energy 2) absorbed with total loss of energy 3) scatted with some absorption and loss of energy 4) transmitted unchanged

pure absorption and interaction with low energy photons incoming X-ray photon interacts with inner bound shell electron mall the energy of the photon is transferred to the electron hole is filled by electrons from outer shell

z3 (x3,3times)

1)x ray photons hit free outer shell electrons 2) inner shell electrons ejected 3) electron absorb some of the photons energy and is deflected 4)photos having lost some energy is scattered and deflected l

patient dose operator dose image quality

direct and indirect action

damage as a result of the ionisation of macromolecules

as a result of free radicals produced by the ionisation of water

amount of energy absorbed from the radiation beam per unit of tissue

effectiveness of different types of radiation

how diff tissues show diff sensitivity’s to radiation

measuring the total effective dose to a population from a radiation source

dose per unit of time

- damage to genetic material in the cell that can cause cells to become cancerous - abnormal replication - cell death

- can appear quickly and have delayed effects - may take years to appear

- can be passed onto off spring - can be congenital radiation - Deleon’s on stage of cells reproductive cycle

caused by interactions of radiation within water molecules. ionising radiation break down the bonds that hold the water molecule together producing free radicals that cause cell destruction

- somatic deterministic effects - somatic non deterministic effects (schotastic) - genetic non deterministic effects (schotastic)

somatic - effects cells deterministic - definitely happens at a certain level known threshold

eg Maligancy - radiation induced cancers do not appear until at least 10 years after exposure - can happen when body is exposed to any dose of radiation this means it hasn’t been able to establish a safe dose - no known threshold

direct damage is somatic and effects the genetic material of the cell where as indirect effects the bonds of macromolecules usually water and involves ioning radiation

- tooth and apices - apical infections - caries and perio status - trauma - assessment of presence/ positioning of unerupted teeth - root morphology - cysts - endodontics - implants

- tooth and film should be parallel and close to one another - receptor should be vertical for incisors - receptor should be horizontal for pre molars and molars - x ray beam and tube should be at a right angles - position should be reproduceable

- holder and receptor parallel to long axis of tooth - x ray tube head aimed at right angle - can’t always be achieved because patient anatomy - can be reproducible

Spitting a space into 2 equal parts Not partakes but get it as close as possible Operator led so Margin for error is higher

- little chance for coming off holders - reproduceable - geometrically accurate images - displays bone levels molars - good for caries detection - angulation automatically deteremined by bolder - displays apical tissue

- positioning of film can be uncomfortable for patient - positioning of holder can be difficult if the operator is inexperienced - holders should be autoclaved - apices can be very near to edge of film - difficult for 3rd molars - shallow/flat palate makes technique impossible

results in a radio graphic image the same length that is the same length as the tooth

results in a radiographic image that is not the same length as the tooth

elongated or foreshortened

- better patient comfort - positioning is quick and simple - should give adequate image of angulation are accurately checked

- not reproducible - many variables that can cause image distortion - hard to detect - shadow of zygomate buttress can overtly roots of upper molars - possibl horizontal overlapping

red - bite wings blue - anteriors green - endodontics yellow - molars

- crowns of molars and pre molars on 1 side of jaw - interdental crestal bone - caries

- apicies - periapical tissues

- caries progression - assessment of periodontal status - assessment of existing restorations

- film parallel to crowns of upper and lower teeth - x ray beam should beet the teeth and film at right angles - central x ray of bream directed towards death at 5-8 degrees vertical angulation

natural angulation of teeth so bite blocks help with this

- simple - avoid coming off - holders are sterilised - bite platform prevents tongue moving receptor - xray tube head and holder indicators allows beam to be directed at right angles

- position of holder is dependent on operator skill - can be uncomfortable - holders can be costly - not usually suitable for children

- operator dependent - ideal for children - reproducibly compromised - operator has to asscess Bertie angle at 10 degrees - aim the beam so it passes through contact points

simple reduced costs effective with children tabs are disposable so no extra infection control required

operator dependent reduced chance of reproducibility higher risk of conimh off not compatible with some digital sensors

maxillary occlusal projections mandibular occlusal projections

maxillary occlusal protections upper oblique occlusal

true occlusal (90 degree) lower oblique occlusal standard 45 degrees anterior occlusal

anterior part of maxilla and upper anterior teeth periapical assessment of upper renter or can be used for patients that can’t tolerate a Pa detecting unerupted canines or supernumerary size and extent of tumours/ cysts - fractures and alveolar bone

- occlusal plane horizontal and parallel to floor - long axis of film crossways in adults x day tune in midline aimed downwards through the bridge of the nose at an angle of 65-70 degrees

posterior part of maxilla and upper posterior teeth on one side periapical assessment of posterior teeth in adults who cannot tolerate PA size and extent of cysts condition of antral floor location and position of displaroots displayed during extraction fracture and post op alveolar bone

long axis anterioposteriorly on side of mouth tube head positioned to side of face aiming downwards through cheek - 65 degrees

view of mandible and FOM -bucolic - lingual position of unerupted teeth size of cysts and tumours fracture