Practice questions

• Comment on this Radiograph:

  • Shows a left hand side bitewing of (list teeth in exam)
  • The position of the central long axis of the film: incorrect as can see crowns of upper and lower posteriors, however slightly lingually places as can see more of lower roots
  • Image contrast: aqequate as able so see different densities of enamel/dentine/cementum. Although bone tuberosity/lamina dura not overly clear
  • Blip? correct as top mesially placed

  
• Comment on:

  • density - adequate as directly exposed areas look dark, however bony details lost eg loss of tubecule, crest.
  • position of posterior border of the film - adequate, able to see distal surface of last molar, but could argue too much space shown.
  • area included on the radiograph - RHS, UR7, UR6, UR5, UR4, UR3, LR3, LR4, LR5, LR6, LR7.
  • central long axis poor as film palatally displaced, as we can see more of upper roots than the lowers.

  
• Comment:

  • lower edge film position: adequate as more 3mm space aware from the incisal edge
  • poor contrast as unable to see pulp/denting/enamel clearly
  • good sharpness as good bony trabeculae, lamina dura and PDL all visable

  
• Comment on PA to show LR6/7:

  • central point of central ray - adequate, positioned correctly however cone cut
  • vertical angle of beam - correct as molar crowns in profile, and shows LR6 and LR7, cusps not in bite block
  • position of short central axis of film - adequate, centre of film should be the interdental space of LR6 and LR7, too mesial, film needs to be more distal
  • mesio-distal angle - anatomical overlap

  
• Comment:

  • Frankforts Plane - horizontal as palate appears as one solid line
  • median sagittal plane - good as both condyles are level so not tilted, and both rami appear the same width so not rotated
  • position of tongue - not in roof of mouth as there is black shadowing at the apex of maxillary teeth
  • focal trough setting - anterior teeth appear clear, set correctly

  
• Comment:

  • focal trough setting - anterior teeth appear clear, detail of incisal edges same detail of molars
  • position of Frankforts Plane - incorrect as hard palate appears a double line
  • position of cervical spine - correct as cannot see spine
  • sharpness - good

  
• • the operator pressing the button will be within the control area, the door is not lead lined
  • during an exposure of the LHS BW, beam directed out of ground floor window, posing risk to members of the public walking past, RHS BW, beam directed out of the non-lead-lined doors, posing risk to members of staff/public walking past

  
• • central ray directly to middle of film? - incorrect as occlusal surfaces shown on all 4 molars, cone cut also
  • long central axis placed correctly? - poor, lingually displaced, as can see more of lowers than uppers, the exact centre of film is below the biteblock
  • short central axis - distally places as unable to full crown of LL4
  • Lateral angel - good
  • Blip in correcct place
  • density - adequate as directly exposed area appear very dark, bony margins can be seen but not overly clear

  
• Comment:

  • vertical angle incorrect - UL6 cusps in contact with edge of film (not more than 4mm), evidencce of cusp in biteblock, widely separated cusps
  • contract adequate - can distinguish between enamel and pulp, but not well, not easy to see bony trabecular
  • short central ray is good, tooth being x-rays is central

  
• Comment:

  • blip correctly placed - mesially
  • posterior edge is in correct place as BWs required last IP space, however could be argues unable to see distal of 7s and may required this for diagnosis
  • density - good as directly exposed area are very dark, able to see bony detail such as bony tubercule, lamina dura and PDL
  • contrast - poor, cannot distinguish between enamel/dentine/pulp
  • vertical angel correct and cusps in profile
  • central long axis correct as equal upper and lowers

  
• Comment:

  • correct area shown to exam LR5,6,7, however short central axis is not correct as does not pass directly though the 6 - which should be the center, film distally placed.
  • density is good, directly exposed areas appear dark, however apices are not clearly demonstrated in particular on the lower 7
  • poor contrast as unable to clearly see differences in densities of pulp/enamel/dentine
  • vertical angel correct, cusps in profile, 4mm from lower edge, 6 and 7 in profile
  • central ray is not directed to the centre, cone cut

  
• comment:

  • tongue in roof of mouth
  • Median sagittal plane is tilted, the distance between condyles and end of film is not the same on both sides.
  • contrast is good, able to see different densities of enamel/pulp/dentine, able to see bony details clearly eg bony trabecule, lamina dura
  • frankforts plane is not horizontal as 2 lines of hard palate
  • median sagittal plane rotated as LHS ramus is wider than the RHS

  
• comment:

  • frankfort plane horizontal, one single line of the hard palate
  • tongue not in roof of mouth, as a full air shadow fills the full width of the vault
  • focal trough is not correctly set, anterior teeth seem as more unclear than molar teeth
  • median sagittal plane - not rotated as both rami same size, not tilted as the condyles are both the same position from the edge of the film

  
• list 7 essential elements needed for imaging geometry to produce and accurate image:

  • central beam has to be central to middle of object
  • film parallel to object (most important)
  • focus to film distance is long
  • short object to film relative distance (paralleling technique ignores this)
  • central ray should be perpendicular to image plate and object
• what are the consequences if object is not parallel to the film?

  • distortion
  • can get elongation and foreshortening
• if vertical angle incorrect

  • you wont get elongation and foreshortening
  • things that are closer to tube than fill, will be moved up and down the image
• if lateral angle correct:

  • no elongation or foreshortening
  • overlapping of cusp, incorrect diagnosis
• two reasons why an image might be low density on traditional radiography?

  • low density if too pale
  • over exposed to light
  • exhausted developer, underdevelopment
  • underexposed
  • film/plate back to front - so lead foil blocks x-ray photons
• 3 ways to assess the accuracy of vertical angel on a PA rad?

  • position of cusps, superinferiors? see the occlusal surfaces
  • ensuring bite block not superimposed/ incisal edge/cusps not inside the bite block
  • occlusal/incisal distance 3mm from edge of film
• how would you assess vertical angel using the bisecting technique?

  by assessing image for

  • elongation - shallow angle
  • foreshortening - steep angle
• effects of enlongation/foreshortening also worst at roots as area furthest away from film
• why do we have set parameters for an OPG? to ensure that

  • central ray is perpendicular to object
  • plate is parallel to object
• why in dental radiography might we not place the object in the middle of the film?

  if the last standing tooth is under investigation

  want to have is as far distal to maximise information obtained mesially
• a limitation of post-acquisition manipulation of the image?

  • if already underexposed? unable make darker, will not show information list, information lost altogether
  • manipulative to loose diagnostic detail from original image
• crani-caudal angle aka the vertical angle
• if the LHS looks bigger during an OPG, pt is looking left
• Median Sagittal Plane: line directly down the middle of face dividing hedd into equal left and right halves
• upper positioning line - line from ala of nose to top of tragus of ear, parallel to occlusal plane
• lower positioning line - line from canthus of mouth to top of tragus of ear, parallel to lower occlusal plane when mouth is open
• franforts plane - line from lower orbital margin to top of tragus of ear, parallel to hard palate
• why do we use parallelling technique?

  • always gives accurate image
  • reproducible and accurate
  • fewer repeats, due to error
  • rectangular collimator more practical
• what do we evaluate on xray image?

  • teeth required for exam shown
  • can all crowns be seen 4mm of apical tissue
  • any adjacent teeth
  • blip correct?
  • central long and short axis correct
  • lower edge 3mm of bite surface
• density considerations?

  • are directly exposed area black/dark
  • enough to see apical area for PA and bony crest for BWs
  • good, adequate, poor
• contrast consideration?

  • difference in density between adjacent area
  • good, adequate, poor
• Sharpness?

  • fine detail
  • check bony trabecular pattern, lamina dura, canal for perio ligament
  • good, adequate, poor
• Artefacts examples

  • tongue studs
  • gelatine mark
  • scratch mark on phosphor plate
• what do we comment on with OPG?

  • area shown - no of condyles, angles of mandible, symphysis menti
  • median sagittal plane? tilted - condyle distance, rotated - rami width
  • franforts plane horizontal? palate single line
  • focal trough setting 2/3 - detail of anterior teeth = molar teeth
  • tongue in roof of mouth - dark air shadow below palate
  • spine? if not straight white shadow obscuring the anterior teeth
  • density, contrast, sharpness