Radiography Flashcards
What is the atomic structure?
Proton
Neutron
Electrons
What charge does a proton carry?
+1
What charge does a neutron carry?
neutral
What charge does an electron carry?
-1
What is the binding energy of shell K (s)
70 keV
What is the binding energy of shell L (p)
12 keV
What is the binding energy of shell M (d)
3keV
What is the general rule for protons and electrons?
They are the same
How do you calculate atomic mass?
Protons + neutrons
What is the definition of ionisation?
The loss of an electron requiring energy to be used
What is the definition of radiation?
Emission and propagation of energy in the forms of waves or particles
How do ionising radiation produce ions?
removing an electron
Which radiation types can ionise atoms?
alpha and beta particles
gamma rays
What is the definition of radioactivity?
Unstable atoms which decay, an imbalance in protons and neutrons
Nucleus can’t generate enough binding strength
What forms can radioactivity be released as?
Alpha: 2 protons and 2 neutrons
Beta: fast moving electrons
gamma ray: high energy electromagnetic radiation
What is the definition of electromagnetic radiation?
The propagation of wave like energy through space or matter. Bundles of energy called photons travels as a wave, but in a straight line
Explain how the x-ray tube create x-rays?
- Filament is heated producing a cloud of electrons
- Potential difference across tube accelerates the electrons at high speed towards the anode
- Electrons bombard the target, then brought to rest fast, energy transferred to heat and x-rays
- heat removed by copper bar and oil
- x-rays emitted via small window in the lead casing creates beam
In which direction do electrons travel?
From cathode to anode
How to increase the necessary voltage needed to power a x-ray machine?
A step-up transformer
number of coils increase the step-up need
What are the 2 forms of heat being produced during ionisation?
The incoming electron is deflected by the outer electron shell creating heat
The incoming electron collides with the outer shell of electrons displacing the electron creating heat
What type of spectrum does 1-3 electron give?
Continuous
Braking radiation
Needs a filter to remove low energy photons
What type of spectrum does 4 electron give?
Characteristic
What is the definition of intensity?
Quantity of x-ray photons in the beam - current
WHat is the definition of quality?
The energy carried by the x-ray photon - voltage
What factors affect the intensity/quality of the beam?
Tube voltage Tube current Distance from target Time length of exposure Filtration Target material Tube voltage waveform
What rule do x-ray beams obey?
Inverse square law
What is the definition of kVp?
Changing this laters the force with which the electrons are drawn from the cathode to the anode
What changes if the kVp is reduced?
Gives better contract but higher tissue absorption (photoelectric effect predominates)
What changes if the kVp is increased?
Reduced attenuation in matter
Decreases contrast
Increases dose but not linearly (compton scatter)
What is the definition of mA?
Changing the current alters the number of electrons on the cathode which can be drawn to the anode (beam intensity)
What changes if the mA is increased?
Increases beam intensity, this can reduce image noise and improve radiographic contrast but does increase dose proportionally
What is the equation of the inverse square law?
Intensity = 1/d2
d = distance from source
e.g. in air, doubling the distance from an x-ray source reduce intensity to 1/4
How can radiation cause damage?
Damage DNA directly or indirectly
How does radiation damage DNA directly?
Radiation interacts with the atoms of a DNA molecule or another cell component
Gives off 33eV, therefore able to break a C-C bond (4.9eV)
How does radiation damage DNA indirectly?
Radiation interacts with water in the cell, producing free radicals which can induce damage
What types of damages can occur to the DNA?
Single break
Double break
Chemical change
What factors will change the biological effect caused by the radiation?
Type of radiation
Tissue or type of cell
Dose
Dose rate
What tissues are considered highly radiosensitive?
Lymphoid tissue Bone marrow GI epithelium Gonads Embryonic tissues
What tissues are considered moderatly radiosensitive?
Skin Vascular endothelium Lung Kidney Liver Lens
What tissues are considered lowly radiosensitive?
Salivary glands
CNS
Muscle
Bones/Cartilage
What is the definition of deterministic radiography effects? and signs?
High radiation dose received over a short time
Skin erythema, sterility and tissue necrosis
What is the definition of stochastic radiography effects? and future effects?
Low doses received over a prolonged period
Cancer, leukemia and genetic effects
What are the 4 possible fates of x-rays?
Absorption
Transmission
Scattering
Attenuation
Why can absorption be bad?
Photoelectric effect
Most likely to cause harm to tissues
Explain the photoelectric effect?
Low energy photons
Incoming photons interact with bound inner shell electron, which is ejected with high energy called the photoelectron into tissue
The ejected photoelectron behaves like other x-rays, and ejects other photoelectrons, which creates the majority of ionisation interactions, which can cause damage
The vacancy of the inner electron shell is filled by the outer electron shell, forming a low energy radiation
Atomic stability is restored by capture of a free electron
Explain the Compton effect?
High energy photons
Incoming x-ray photon interacts with free or loosely bound outer shell electron
Outer shell electron is ejected - Compton recoil electron - with loss of energy, undergoing further ionisation interactions within tissues
Remained of incoming photon is scattered from original path as a scattered photon
The scattered photon may undergo further compton interactions, photoelectric interactions and escape tissues via scatter
Atomic stability is regained after capture of anther free electron
What is essential for the photoelectric effect to occur?
The energy of the incoming x-ray photon must be equal to or greater than the binding energy of the inner shell electron
How does tissue density affect number of electron shells?
As tissue density increases, the number of electron shells increase, with a corresponding increase in binding energy at the inner shell
How to work out the probability of photoelectric reactions occuring?
Proportional to Z (atomic number)3 (cubed)
How is contrast produced between tissues?
As they have different radiodensities
What do intensifying screen use to convert x-rays to light? and what is it sued for?
Photoelectric effect
Extra-roal work
What is essential for the Compton effect to occur?
The energy of the incoming x-ray must be much greater than the binding energy of the outer shell electron
Why does the Compton effect not depend on the atomic number?
As it is an outer electron, and so does not contribute to the contrast of the image
What contributes to image degradation?
High energy scattered photons produce forward scatter
Low energy scattered photons produce back scatter
What do the Photoelectric and Compton effect result from?
Ionisation of tissues
What are the 4 major guidelines for radiographic radiation usage?
Radiographic standards in primary dental care
Dental practitioners on the safe use of X-ray equipment
Selection criteria for dental radiographs
Safe use of dental cone beam CT equipment
Explain the linear no-threshold model for radiographic radiation?
Increasing the dose with increase the change of side effects
Any dose can give side effects
Effect is directly proportional to dose at all dose levels
What are the side effect risk of causing fatal cancer from an intra-oral x-ray?
1:4,000,000
What are the side effect risk of causing fatal cancer from an OPG?
1:2,000,000
What are the side effect risk of causing fatal cancer from staff standing 1.5m away?
1:67,000,000
What is the definition of a radiation absorbed dose?
A measure of the amount of energy absorbed from the radiation beam per unit mass of tissue and can be measured using a dosimeter (not reflect biological damage)
Measured in Gray (Gy)
What is the definition of an equivalent dose?
This measures the effects of different types of radiation on tissues e.g. alpa are completely absorbed, x-rays are only partially absorbed
Equivalent dose = absorbed dose * radiation weighting dose factor
What is the radiation weighting factor for an x-ray?
1
What is the definition of the effective dose?
Takes account of the fact that different tissues show different sensitivities to radiation, and allows comparison of risk of different types of radiation exposure. Tissue weighting factor
Effect dose = Sum (absorbed dose * radiation weighting factor & tissue weighting factor)
What does the effective does allow us to compare? and its measurement?
Comparison between whole body irradiation and a radiation dose which is uniformly distributed
Sieverts (Sv)
What is the weighting factor for salivary glands?
0.01
What is the value of the natural dose of radiation be received daily?
7.5 millisieverts per day
Name the 5 main sources of radiation?
Medical Radon Gamma rays from ground and buildings Internal from food and drink Cosmic
What % source is radon?
50.1%
What are some everyday items that give off radiation?
Granite
Bananas
Brazil nuts
How do dental radiographs compare to everyday life radiation exposure/
200g brazil nuts
28 hours in Aberdeen
European flight
What is the ratio for 1mSv to give a fatal case of cancer?
1:20,000
What is the effective dose for an intraoral x-ray?
0.003mSv
What is the effective dose for an OPG?
0.010mSv
What dose will a staff member receives standing 1.5 metres away?
0.0003mSv
What is the ALARP principle?
As Low As Reasonably Practicable
What are the best ways to reduce dental raditation exposure?
Technique
IR rules/guidance
Equipment
What are the consentual laws for x-rays?
Implied
Explain which tooth and why
Double check the tooth
When is direct action film used?
Packet film
When is indirect action film used?
Intensifying screen
Cassette
Name 2 types of digital receptors?
Solid-state sensors
Phosphor plates*
Explain how direct action film work?
Sensitive to x-ray photons
Intra oral work (bitewings and occlusals)
Explain how indirect action film works?
Used with intensifying screens in a cassette
Film sensitive to light photons emitted by intensifying screen when they are stimulated by X-rays
Require less exposure to x-rays to produce an image
Panoramic, cephalometric films and sialography
Name the parts of a direct-action film?
Film
Protective black paper
Lead foil
Outer wrapper
What is the function of the outer wrapper?
Plastic
Sealed to maintain light tightness and prevent saliva ingress
White side must face x-ray beam
What is the function of the lead foil?
Absorbs some of the residual radiation, preventing further penetration
Prevents ‘backscatter’
Needs to be placed the correct way up
What is the function of the black paper?
On both sides of film
Protecting from light, saliva and damage whilst being unwrapped
What is the structure of radiographic film?
Protective layer Emulsion Adhesive Plastic base Adhesive Emulsion Protective layer
What is the active part of the radiographic film?
Emulsion
What is the function of the plastic base?
Supports the emulsion bit does not contribute to the image
Transparent cellulose acetate
What is the function of the adhesive?
Holds the emulsion on the base
Very thin
How does emulsion work and what is it’s overall function?
2 layers on either side of base
Attached by adhesive
A gelatin matrix contains silver halide crystals
These crystals are sensitive to X-ray photons, those that are struck by photons appear as black on the processed image
What is the function of the protective layer?
Outermost surface
Protect
How is latent image formation carried out?
Crystal exposed to x-ray photon
Displaces an electron
Attracts Ag
Forms black spot
How should you orient the intraoral film?
Dot embossed on one corner, with the raised aspect to the front (towards beam)
Dot appears on image raised, and viewed as if operator was facing patient
For periapicals where should the dot be found?
Occlusal surface
For bitewings where should the dot be found?
Palatally
For occlusal films where should the dot be found?
Anteriorly
What is the definition of optical density?
Describes the extent of film blackening
What does the characteristic curve show?
Variation in optical density with different exposures
What can affect the amount of background fog on a film?
Colour of plastic base
Development of some unexposed silver halide crystals
How is film speed determined?
Size and number of silver halide crystals
What are the advantages of using faster film?
Use less radiation to achieve the same optical density
What is the definition of film latitude?
Range of exposures that produce visible difference in optical density
What is the definition of film contrast?
The difference in optical density between 2 points on the film that have received different exposures
What is the definition of resolution?
A measure of the ability to differentiate between differing structures in close proximity
What is the resolution of direct action film?
10 lp per mm
What is the resolution of indirect action film?
5 lp per mm
What affects resolution?
Penumbra
Size of silver halide crystals Contrast
Name the parts of indirect action film?
Plastic front Front intensifier Double-sided film Rear intensifier Felt backing Metal back
Explain how do intensifying screens turn x-ray beams into a latent image?
Fluorescent phosphors absorb x-rays
Converting it to visible light by the photoelectric effect
The light then forms a latent image on the film emulsion
90% light and 10% x-ray reduces dose
How should you select film for intensifying screens?
Sensitive to the emissions wavelength of the screen
Speed
Resolution
Latitude
What must be taken under consideration when picking a film and screen type?
Quality of image
Dose to patient
What characteristics must a cassette have to be functional?
Strong but lightweight Reusable Radiotranslucent on tube side Light tight Rigid Easy to clean Cassette orientation tube side to patient Patient ID attached
What must be used when using a cassette?
A side marker
What are the stages of chemical processing?
Developing Washing Fixing Washing Drying
Explain the process of developing film?
Sensitised silver halide crystals in the emulsion are converted to black metallic silver to produce the back and gray parts of the image
Developer is alkaline
Explain the process of washing, after developing?
Film is washed in water to remove residual developer solution
Explain the process of fixing?
Desensitised silver halide crystals in the emulsion are removed to reveal the transparent or white parts of the image and the emulsion is hardened
Fixer is acidic
Explain the process of washing, after fixing?
Film is washed to remove residual dixer solution
Explain the process of drying?
Radiograph is dried
Explain how an automatic film processing device works?
Film is loaded in the darkroom, or a daylight process where darkroom facilities are still required for loading and maintenance. As with wet developing statis of chemical solutions must be well maintained
Explain how self-developing films work?
Are in a sachet containing developer and fixer. Once exposed frst the developer, then the fixer are introduced. The filam can be viewed after a minute but must be rinsed for at least 10 mins soon after to remove chemicals
Poor image quality and deteriorates rapidly
What are the requirements for a darkroom?
Must be light tight Safe light (red) Light tight film hopper Ventilation Well maintained Processor maintenance
Where to store film?
Cool and dry
Away from chemical and radiation
How to care for screens?
Reg cleaning
Avoid scratches
Check for any loss of film
Name 2 types of Solid state sensors?
Charge coupled device
Complementary metal oxide semiconductor
Describe the solid state drive sensor?
Film packet size but 5-7mm thick Cabled to transfer data to PC Can be wireless but bulkier Can't be autoclaved (barrier envelope) Consists of silicon chip based pixels and electronics encased in plastic holding
Explain the process of how a charge-coupled device converts x-rays to a latent image?
Individual pixels consists of P- and N-type silicon
Arranged in rows and columns
Scintillation layer above array
X-ray hit the scin layer and converted to light
Light interacts with silicon (photoelectric effect) to create a charge packed for each pixel
Light is concentrated by electrodes
Image is read by transferring each row of pixel charges
Transferred to amplifier and transmitted to PC
Each sensor has how many pixels in a CCD?
1.5-2.5 mil
WHat is the size of 1 pixel?
20-70um
Explain the process of how a complementary metal oxide detector converts x-rays to a latent image?
Similar construction to CCD
Consists of an array of pixels
Each pixel is isolated from it neighbour and directly connected to a translator
THe charge from each pixel is transferred t the transistor as a voltage enabling the individual pixel to be assessed
Describe what an extra-oral sensor is, what it’ll replace and an example?
A long narrow pixel array is aligned with a thin slit shaped x-ray beam which scans across the patient
Replace indirect, intensifying and cassette films
OPGs and cephalometry
How to use a photostimulable phosphor storage plate (PSP)?
No direct connections to computer Can be reused Placed in narrier envelope Dot is flat Blue side is active and must face x-ray tube
Name the parts of a PSP?
Protective layer Phosphor layer Reflective layer Conductive layer Support Backing layer
What is the phosphor layer function?
Absorbs and stores x-ray energy not attenuated by patient
What is the difference between CCD/CMOS and PSPs?
CCD and CMOS signal straight to a computer
PSPs require the plates to be placed into a reader
Explain how do phosphor plate reader work?
Read using laser beam
Stored x-ray energy in the phosphor layer is released as light which is detected by the multiplier tube and converted into a voltage which is input to the analogue to digital converted of the connected computer and displaced as a digital image
What does the plate reader laser do, other than read the image?
Resets the electrons, and so wipes the plate
Explain how the computer processes the phosphor plate reader data?
Analogue voltage from each pixel is changed by the analogue to digital converted into a discrete numerical digital signal
Each pixel has a x and y coordinate and is allocated a number between 0-255 grayscale
0 - no attenuation
255 - total attenuation
Computer allocates an appropriate colour from grayscale to create the visual image on the monitor
0 Grey scale?
Black
255 Grey scale?
White
What determines the information, size, detail and resolution of the image?
Number and size of pixels along with the number of shades of grey available
Manipulating the image and increasing the contrast can?
Remove the middle part of the greyscale
Manipulating the image and increasing the brightness can?
Increase or decrease the pixel number (darker or lighter)
Manipulating the image inversion can?
Make a positive image of the existing negative image
Manipulating the image and embossing it can?
Appear to enhance the edges of structures
Manipulating the image and increasing the magnifcaiton can?
Will lose some detail depending on pixel size and resolution
Manipulating the image and pseudo colouring aspects can?
Draw eye to certain areas due to colour use
Where to store film and hard copies?
Patient’s record
Where to store digital copies?
r4
Why is repetition of the same x-ray illegal?
Not justified under the IR(ME)R regulations
Name the 5 principles of shadow casting
Focus to object distance large Object to film distance small Object and film parallel X-ray beam perpendicular to object and film Radiation source as small as possible
What is the effect of focus to object distance?
Greater focus to object distance reduces magnification
What is the effect of change in object to film distance?
Larger object film distance increases magnification
What is the effect of object/film/beam angulation?
Film - image elongated
object - image foreshortened
x-ray - image distorted
What is the definition of sharpness?
How well the detail of an object are defined
What is the effect of focus size?
Smaller focus size produces a sharper image
Name the 5 factors that affect sharpness?
Focal spot size Focal spot to object distance Object to film distance Image receptor Movement
What is the definition of penumbra?
Zone of unsharpness along the edges of images in a radiograph
Partial shadow (between complete shadow and complete illumination)
What is the effect of focus to object distance (penumbra)?
Greater focus to object distance reduces magnification and penumbra
What problems does a radiograph give rise to?
2D image of 3D
Shape determination
Superimposition
Distortion
Explain how to create the perfect intraoral image?
Image receptor should be flat
Image receptor should be parallel to long axis of the tooth
IR should be as close as tooth as possible
Central ray should be perpendicular to object and image receptor
Distance between focus and tooth should be large
WHat is the selection criteria to think about when choosing radiograph type?
Detection of caries Detection of apical infection/inflamm Perio status Trauma Presence and position of unerupted teeth Assessment of root morphology During endodontics Pre Op and Post OP apical surgery Detailed evaluation of apical cysts and other lesions evaluation of implants
Explain the paralleling technique theory?
Film placed in holder and positioned parallel to the long axis of the tooth
X-ray beam aimed at right angles to tooth and film
Use of holder allows the image to be reproducible
Explain the bisecting angle technique theory?
Film is placed as close to tooth as possible
Angle between long axis of tooth and film is assessed and mentally bisected
Beam is aimed at right angles to the bisected line
Give accurate image
What are the advantages and disadvantages of the paralleling compared to the bisecting angle technique?
Adv: - sharper less distorted image - correct centring of image on film - less guesswork - reproducible - head position not critical Dis: - difficult or impossible if palate low or FoM shallow Can be difficult if using rubber dam clamps - strong gag reflex
Selection criteria for a horizontal bitewing?
Caries in posterior Deficient/leaky restorations Poorly contoured restorations Calculus Early perio bone loss
Advantages of using a horizontal bitewing holder?
Improves centering
Reduces overlapping
Serial radiographs comparable
Explain the horizontal bitewing placement technique
Beam is aimed at right angles to the film and thog the interproximal space to prevent overlap
Selection criteria for a vertical bitewing?
Useful for demonstrating mild to moderate alveolar bone loss (BPE4)
Explain the vertical bitewing technique?
Same but different film holder
Selection criteria for an upper standard occlusal radiograph?
Periapical assessment of upper anterior teeth
Presence of unerupted canines or supernumeraries
For parallax in conjunction with OPG
Size of cysts/tumours
Assessment of alveolar fractures
Selection criteria for an upper oblique occlusal radiograph?
Similar to standard occlusal but shows premolar and molar regions
Cleft palate
Selection criteria for a upper vertex occlusal
Similar to standard occlusal but gives plan view of palate (will show buccolingual position of unerupted canines
No longer recommended
Selection criteria for Lower 90 true occlusal?
Detection of submandibular calculi
Assessment of buccolingual position of unerupted mandibular teeth
Evaluation of buccolingual cortical expansion
Assessment of mandibular width prior to implant placement
Selection criteria for Lower 45 standard occlusal?
Similar to a true occlusal but also as a periapical view of the lower anteriors
How to x-ray soft tissue?
Use film holder
Reduce exposure
How to quality assure the x-ray machine?
Check:
- machine outputs
- Image processing equipment
- Image quality
What is the basis of a Grade 1 radiograph?
Excellent
No error of patient prep, exposure, positioning, processing or film handling
What is the basis of a Grade 2 radiograph?
Diagnostically
Some errors of patient prep, exposure, acceptable positioning, processing or film handling, but which do not detract from the diagnostic utility of the radigraph
What is the basis of a Grade 3 radiograph?
Unacceptable
Errors of patient prep, exposure, positioning, processing or film handling, which render the radiograph diagnostically acceptable
Grade targets for minimum radiographic quality?
1 - no less than 70%
2 - no greater than 20%
3 - no greater than 10%
Grade targets for interim radiographic quality? (training or new equipment)
1 - no less than 50%
2 - no greater than 40%
3 - no greater than 10%
How does the x-ray tube move?
Passes behind the patient, the image receptor crosses in front of their face
Name the 5 parts of a tomograph?
Tube Connecting bar Pivot Cassette Stationary table top
Name the 2 parts of an OPG machine?
Detector
X-ray tube
Selection criteria for an OPG?
Bony lesions or unerupted teeth that can't be demonstrated on an ntraoal film Grossly neglected mouth Assessment of periodontal disease Assessment of 3rd molars Unable to tolerate intraoral views Ortho assessment Assessment prior to GA Mandibular fracture TMJ disease Antral disease Pre-implant planning
What are the positioning problems for an OPG?
Too high Too low Too close Too far Rotation Lateral inclination Artefact (earrings) Shoulders (large) Movement
What causes ghosting?
Bone’s density
What are the advantages of using an OPG?
Large area is imaged, all anatomy within the focal trough will be visualised
Positioning is simple
Overall view for rapid assessment of underlying disease
Overall evaluation of periodontal disease or ortho assessment
Both condylar heads shown
Antral floor is visualised
very useful for fractures - see both sides of mandible
Radiation dose is likely to be lower than a full set of periapicals
What are the disadvantages of using an OPG?
Structures outwith the focal trough will be missed
Soft tissues, air shadow, ghost shadow and artefact can obscure structures
Magnification of image
Resolution is lower than intraoral
Require patient to remain still for 20+ seconds
Patient’s maxilla/mandible must be same shape as focal trough
Operator must be skilled
What are the ideal quality criteria for a successful OPG?
All upper and lower teeth and supporting bone should be clearly demonstrated
Whole mandible included
Right and left molar teeth should be equal in their mesiodistal dimension
Uniform density across the image, no air shadow above tongue
Hard palate should be above apices of maxillary teeth
No artefacts
Image must be annotated with side marker and name/ID
What equipment is needed for a cephalometric radiograph?
Apart of OPG Unit
Have a fixed FFD > 1m, usually 1.5-.7m (to minimise magnification effect)
X-ray output and film.image receptor parallel (beam perpendicular to image receptor)
Uses positioning aids to ensure standard position of patient and reproducibility of projection
Includes a radiopaque marker to calculate magnification factors
Requires collimation device to restrict radiation to cranial abs and thyroid
employs filters to ensure the soft tissues structures of the face are visualised
Name the 2 types of cephalometric projections?
True cephalometric lateral skull
Cephalometric posteroanterior of the j aws
What are the main indications for cepahlomerric radiographs?
Orthodontics: - initial diagnosis - treatment planning - monitoring treatment progress - appraisal of result Orthognathic surgery: - pre-OP eval - treatment planning - post OP appraisal - long term follow up
Explain how to position a patient for a cephalometric radiograph?
Sagittal plane parallel to image receptor
X-ray beam perpendicular to image receptor
Frankfort plane horizontal
Patient’s head is immobilised using ear prongs in EAM
Magnification measure applied to nasion
Check approp filtres are correctly positioned
Teeth should be in ICP
Tongue to roof of mouth with lips closed
What is essential in quality criteria for a successful cephalometric radiograph?
Patient facing to the right True lateral Marker on nasion Teeth in ICP Use of collimation Lower border of mandible visualised
What is the definition of parallax?
Trying to identify whether a structure is behind or infront of another structure
Explain the process of suing parallax to identify position of the structure?
If objects moves in the same direction as viewer shift, then it is positioned posteriorly
If object moves in opposite direction to viewer shift then it is position anteriorly
What is SLOB acronym?
Same lingual
Opposite buccal
A variably-sized radiolucent strip between the superior surface of the tongue and the palate can be seen, this may obscure the roots of the anterior teeth due to overexposure, how can you minimise this?
Patient place tongue flat against palate during imaging
Space created between the upper and lower lips can be seen as a kiss-shaped radiolucency over the crowns of the maxillary and mandibular incisors, how can you minimise this?
Patient to close lips around the bite-stick can prevent overexposure of this area
A ghost of the cervical spine is formed when the anterior teeth are imaged because of the x-ray beaming from behind, this may obscure the anterior region of the jaw, how can you minimise this?
Patient to stand as tall as possible with their cervical spine extended maximally helps minimise the superimposition
What may have occurred if the 3 thin radiopaque lines which run parallel to the posterior wall of the maxillary sinus are not present?
Destructive disease
Explain how to fully assess the alveolar processes and teeth for an OPG?
Assess the crestal bone position of the alveolar processes to identify any periodontal bone loss
Examine the periodontal ligament space and lamina duras around each tooth for signs of inflammatory disease
Examine the follicles and papillae of developing teeth to identify any abnormalities
Evaluate teeth for presence/absence/eruptive or positional abnormalities, caries, poor restos, calculus or developmental or acquired abnormalities
Name the 7 steps to interpret an OPG?
Assess the periphery and corners of the image
Examine the outer cortices of the mandible
Examine the cortices of the maxilla
Examine the zygomatic bones and arches
Assess the internal density of the maxillary sinuses
Assess the structures of the nasal cavity and the palates
Examine bone the pattern of the maxilla and mandible
What to assess when assessing the periphery and corners of the image
Orbits Articular processes of the temporal bones Cervical spine Styloid processes Pharynx Hyoid bone
What to assess when assessing the outer cortices of the mandible?
Anterior and posterior rami
Coronoid process
Condyles and condylar necks
Inferior border
Evenness
What to assess when assessing the cortices of the maxilla?
Zygomatic process of maxilla
Pterygomaxillary fissure
What to assess when assessing the internal density of the maxillary sinuses?
Compare left to right
Opacification common sign of inflammation or worse
What to assess when assessing the structures of the nasal cavity and the palates?
Hard palate and the conchae extending along both sides
Nasal septum in midline
Soft palate extending from posterior hard palate into oropharynx
What to assess when assessing the bone the pattern of the maxilla and mandible?
Density and pattern of the trabeculae
Mandible examine size, pstion, cortication and symmetry of the IAN canals, mandibular foramen and mental foramina
Name the 6 relevant points in the history that relate to CVD?
Chest pain Angina MI HT Medication SOB
When treating an emergency patient which has unstable angina, what is necessary to avoid and what can save their life?
Adrenaline GTN spray (under tongue)
What should be deferred for an uncontrolled cardiac failure?
Any form of anaesthesia until medication and symptoms are stabilised
Placing this sort of patient in a supine position could exacerbate dyspnoea, and should be avoided
How can you assess the severity of a patient’s cardiovascular health?
Waking up in the night with breathlessness or has orthopnoea
Name the 8 procedures which need antibiotic prophylaxis?
Dental extractions
Any procedure involving the raising of a mucosal/ mucoperiosteal flap
Biopsies
Any subgingival procedure eg placement of orthodontic bands (not brackets), scaling of teeth, irrigation of periodontal pockets
Intraligamentary injections
Reimplantation of avulsed teeth
Incision and drainage of an abscess Placement of dental implants
During diagnostic phase of root canal therapy if it is thought likely that an instrument may pass through the tooth apex
What is the main bacteria which causes infective endocarditis?
Viridans Streptococci
What instrument must be avoided with a patient with a pacemaker?
Ultrasonic scaler
Name the 6 post-transplant treatment complications can occur?
Immunosuppression
Steroid therapy
Risk of infective endocarditis (in the first 6 months)
Gingival overgrowth as a result of post-transplant drug therapy Supersensitivity of the transplanted heart to circulating catecholamines which may include epinephrine in dental local anaesthetics
Hepatitis, HIV Infection (rarely)
What to advice to a patient with lymphatic/venous disorder?
Patient should be treated with legs elevated to minimise dependent oedema, but the practitioner should beware of orthopnoea.
What to identify on the first observation of the patient?
Patient’s general demeanour Colour Whether short of breath at rest (SOBAR), or on minimal exertion, eg walking into the surgery Finger clubbing Cyanosis Swollen ankles
When does finger clubbing occur?
IE
Cyanotic congenital heart disease
Thyrotoxicosis
What limit should be put on LA + ADR for patients taking beta blockers/
2 cartridges max
Sides:
- dry mouth
- lichenoid reaction
What limit should be put on LA + ADR for patients taking non-K sparing diuretics?
1/2 cartridges max
What to avoid for patients which have just undergone cardiac transplatation?
Can super react to ADR so avoid LA
How long should elective dental surgery be avoided for recent MI?
At least 3 months but ideally a year
Under emergency situation, carried out with medical consultation
Name the 14 relevant points in the history that relate to respiratory disease?
Smoking history Cough Sputum (colour) Acute problem or chronic disorder? Infection —URTI/LRTI Sinusitis Pneumonia - primary, secondary, atypical Asthma COAD TB Bronchiectasis Cystic Fibrosis Haemoptysis Lung Cancer
What should be avoided for a patient suffering with COAD?
Treatment should be avoided during an exacerbation and always carried out with LA
If patient has Tb what necessary precautions should be taken by the dentist?
Aerosols should be reduced
Rubber dam
Masks and spectacles are mandatory
What are the oral symptoms of sarcoidosis?
Gingival swelling found to be due to sarcoid
Name 4 oral manifestations for respiratory disease?
Gingival swelling (sarcoid)
Ulceration (TB)
Hyperpigmentation (lung cancer) Drug induced xerostomia
What to look out for if suspicious of respiratory disease?
Colour Central cyanosis Dyspnoea Tachypnoea, (use of accessory muscles) Finger clubbing Cervical lymphadenopathy (URTI, TB) Bounding pulse Oral hyperpigmentation Flapping tremor
What are the oral side effects for corticosteroids?
As a result of this oro-pharyngeal candida infection may occur. In order to avoid this complication patients should be advised to rinse and gargle with water after use of their inhaler
What are the oral side effects for beta adrenergic agonist bronchodilators?
Dry mouth, taste alteration and discolouration of the teeth.
Dry mouth may increase caries incidence and thus a preventive regimen is important.
If the dry mouth is severe artificial saliva may be indicated.
What to be wary about when a patient is taking cough suppressants?
There is a theoretical possibility that the adrenergic effects of epinephrine in dental local anaesthetics will be enhanced by ephedrine so dose reduction should be considered.
What to do for anaphylactic shock?
ADR IM dose of 0.5ml increments of 1:1000 and IV hydrocortisone (200-500mg)
What are the signs and symptoms for bleeding disorders?
- Pale
- Jaundice
- Bruising
- Bleeding gingiva
- Glossitis
- Opportunistic infections
- Gingiva enlargement
What is the current advice for surgical operations with a patient taking Warfarin?
INR less than 3.0 without alteration of the Warfarin dosage
What should NEVER be used with Warfarin?
Antifungals
MICONAZOLE
Which sedation should be avoided for a patient suffering from pernicious anaemia?
NO sedation
Which LA block is contraindicated for patient with bleeding disorders?
IAN
What are the optimal viewing conditions for a digital radiograph?
Reduce surrounding light
Use magnification
Look directly at image
What are the optimal viewing conditions for a film radiograph?
Good light box or back lit screen
Low ambient light
Allow time for eyes to adjust
Use a magnifier
What are the disadvantages of radiographs?
2D representation of a 3D image
Grayscale
Artefacts
Guessing game
Describe the attenuation of x-rays from decreasing attenuation to increasing attenuation?
Mental Enamel Dentine Cementum/bone Soft tissues Fluid Air
Cervical burnout?
Shadowing interproximally can be deceiving
What other shadows may be seen on a radiograph?
Lip shadow
Tori
How to structure a radiographic report?
Patient ID Age Name the views (horizontal/vertical) Grade Teeth present Caries Restorations Prosthetics Perio Bone levels Other (lesions, PDL widening and tooth wear) Incidental findings Summarise
What are the 2 legislations for radiography?
IRR17
IR(ME)R 2017
What is the size of the controlled area?
Area may be defined within the primary X-ray
beam until it has been sufficiently attenuated by distance or shielding and within 1.5m of the X-ray
tube and the patient
What minimum unintended dose is necessary to investigate?
1mSv
When should IR equipment receive maintenance and routine testing?
Annual
At least 3 yearly intervals
What is the kV range for new intraoral sets?
60-70
What can you wear for x-ray protection?
Lead apron
Thyroid collar
What is the basic framework pathway to be followed during the course of exposure to ionising radiation?
Referral Procedure justification PAtient identified Exposure Report
What does ALARP stand for?
As low as reasonably practicable
What can be used to reduce dose?
Holder and beam aiming device
What information must a referrer supply?
Accurate, unique identification of the patient
Accurate clinical information sufficient to allow justification to take place
Where relevant – information on pregnancy (not usually required in dentistry)
The unique identification of the referrer (should be legible)
What information must the operator possess to be entitled to carry out practical IR exposure?
Patient ID Making the radiographic exposure Reporting radiographs Processing radiographs Calibrating equipment
What roles in IR does a dentist have?
Practitioner - justify
Referrer - request
Operator - operating and reporting
What should you do in times of accidental or unintended exposures?
An unintended dose is one when an examination should not have taken place. e.g. the
wrong patient is imaged. This is normally externally reportable
A dose ‘significantly greater than that generally considered to be proportionate in the
circumstances’ e.g. if a view is repeated or if the wrong exposure factors are selected or if
the wrong procedure is carried out (e.g. wrong side)
Reporting depends on the additional dose:
For intraoral and extraoral dental films – if unintended dose is x 20 (this may be
reduced in the near future when the updated IPEM guide is published).
For CBCT – if unintended dose is x 3.
If reportable this will be to the IR(ME)R enforcer.
ALL INCIDENTS MUST BE REPORTED ON DATIX, THIS INCLUDES NEAR MISSES
Explain duty of candour in respect to IR?
In the event of an accidental or unintended exposure, you have a duty of candour. This requires the referrer, practitioner and the individual (patient) being informed of the occurrence of a clinically
significant unintended or accidental exposure.
Explain other ways for dose limitation of IR?
Ascertain if there is any previous imaging that may affect the current prescription/request.
Check records and ask the patient. This can be tricky in dentistry as not all records are held centrally, and some patients may be confused as to the exact type and timing of any imaging.
Consider if the prescribed/requested imaging is the most suitable for the patient at this time
– it might be advantageous to use ultrasound, CBCT or MRI.
Limit the field that is irradiated
