Intraoral Projection & Technique

Question 1

What are the 3 categories or projections?

Answer 1

1) Periapical (PA)
2) Bitewing (BW)
3) Occlusal (not commonly used)

Question 2

What does a Full Mouth (FMX) or Complete Mouth Series (CMS) consist of?

Answer 2

• 14 PA’s ad 4 Bitewings

- 18 images total

Question 3

Intraoral Radiographic Imaging

Answer 3

• Can provide diagnostic info for clinical exam
• Operator must understand goals of I/O & criteria to evaluate quality
• Images obtained only when clear diagnostic need exists
• Frequency of x-ray varies

Question 4

What is the Rationale for I/O imaging?

Answer 4

• Used to allow us to visualize hard structures (bone & teeth( that are not visible clinically (IP spaces, alveolar crest & apical anatomy/path)
• High detail, excellent contrast, low magnification, & good risk to benefit ratio for dose
• Use correct imaging modality to match diagnostic task

Question 5

Why not Pano?

Answer 5

• Resolution
• Ability to see fine details
• Differential magnification
• Large field of view
• Projection geometry is fixed
• There are definite indications for pano

Question 6

Why not cone beam CT?

Answer 6

• Limited access / cost
• Radiation high
• Inability to predictability & reliably diagnose dental caries when restoration present
• Artifacts such as beam hardening, patient motion, etc
• There are deficient indication for using CBCT

Question 7

What is the criteria for achieving diagnostically acceptable images?

Answer 7

1) x-rays should RECORD COMPLETE AREA of INTEREST on image
- PA’s see entire tooth, (root, plus at least 2mm of bone past root; entire lesion & normal bone of one x-ray)
- BW’s each posterior proximal surface should be seen at least once (no sig. overlap)

2) LEAST possible amt. of DISTORTION- importance of correct receptor poison & beam angulation
3) OPTIMAL DENSITY & CONTRAST use proper exposure setting

Question 8

What is the Paralleling Technique?

Answer 8

1) X-ray receptor supported parallel to LONG AXIS of teeth
2) Central ray of beam directed @ right angels to teeth & receptor
3) Minimize geometric distortion, presents teeth & supporting bone in anatomic relationship
4) X-ray should be relatively DISTANT from teeth to REDICE distortion
5) Use LONG source to object distance reduces apparent size of focal spot, INCREASING sharpness, & minimal magnification
6) Works equally well for film , CCD, CMOS, or PSP

Question 9

What is the proper receptor holding method?

Answer 9

1) Allow for precise positioning of receptor
2) May be specific for band of receptor
3) External guide ring
4) Used to align aiming cylinder & ensures that receptor & teeth are perpendicular to x-ray beam
5) Ideally used w/ rectangular collimators to reduce exposure

Question 10

What is the Receptor Placement?

Answer 10

1) positioned parallel to teeth
2) Deep in patient mouth
3) Max. projections, superior border of receptor generally rests at height of palatal vault in midline
4) Mandibular projection receptor used to displace tongue medially & posteriorly toward midline.
- Allows inferior border org receptor to rest of floor-of-mouth

Question 11

What is the angulation of tube head?

Answer 11

1) Orient aiming cylinder of x-ray in vertical & horizontal plane to align w/ aiming ring
2) Horizontal direction of beam primarily influences the degree of overlap of the images of the crowns at the IP spaces

Question 12

Describe the intraoral exposures

Answer 12

1) PREPARE the operator & x-ray unit
- Computer
- Infection control
- Sterile XCP
- Digital receptor plugged into wall
- Xray unit turned on

Question 13

Procedure for making I/O exposures?

Answer 13

1) Greet & seat patient
- pt upright w/ proper head support (head still & prevents neck muscles from getting tired)
- Describe procedure

2) REMOVE GLASSES & REMOVABLE APPLIANCES (sometimes parietal/denture can stabilize receptor)
3) USE LEAD APRON
4) Acknowledge patients complaints & EXPRESS APPRECIATION for the COOPERATION & HARD WORK

Question 14

What are the CLINICAL STEPS

Answer 14

1) Examine ORAL CAVITY
- missing teeth
- axial inclination and potion of apices
- anatomic features require accommodation

2) Position the TUBE HEAD TO THE SIDE of the pt that will be radiographed; FMX template default is to start w/ maxillary RIGHT molar projection , then around max. arch and drop to mandibular LEFT molar and finishing w/ Mandibular RIGHT molar projection.

Question 15

What are the steps to positioning the RECEPTOR?

Answer 15

1) ASSEMBLE DIGITAL SENSOR using yellow XCP for posteriors, BLUE for anteriors, and RED for bitewings

2) PLACE THE RECEPTOR IN MOUTH
- Apical end into mouth first
- keep receptor way from teeth
- Allow apical end of receptor to rest gently on hard palate or soft tissue of floor of mouth
- place bite tab on occlusal, keep center of bite tab in center of desired tooth
- place cotton roll btwn bite tab & opposing arch (optional)

Question 16

What is the position of the x-ray tube?

Answer 16

1) MOVE POSITION INDICATING DEVICE (PID) or ling cone of tube head, so that the OPEN END CORRESPONDS to the guide or AIMING RING.
- OPEN END of the cylinder MUST be flush w/ or parallel & close to within 1/4 inch or 3 to 4 mm the guide ring.

2) If conditions are not met DO NOT MAKE EXPOSURE!
3) EXCESSIVE HA or VA & images will not be diagnostic
4) Be cautious w/ retakes

Question 17

How to make the exposure?

Answer 17

1) DOUBLE CHECK that you are using correct exposure time. KEEP FINGER on button until exposure is FINISHED
2) You may need to INCREASE EXPOSURE TIME for some patients that have thicker, higher density (aka larger)
3) INCREASED ATTENUATION occurs, which DECREASES x-ray photons in remnant beam. Results in an underexposed image (too light). Therefore INCREASE EXPOSURE time to INCREASE # of x-ray photons

Question 18

What are the 6 rules for I/O Imaging? (Principal of Dental Imaging)

Answer 18

1) Place receptor to completely cover teeth that are intended to be x-rayed
2) Position vertical sides of receptor PARALLEL to long axis of teeth
3) Position horizontal sides of receptor PARALLEL to horizontal plane of teeth, aka occlusal plane or 90 degrees to long axis of teeth
4) Keep open end of cylinder parallel to receptor
5) Central ray should enter the proximal embrasure at a 90 degree angle
6) Central ray should be directed to central of the properly positioned receptor

Question 19

Why are Vertical Bitewings useful?

Answer 19

In cases of PERIODONTAL DISEASE since alveolar crest os coated more apically than in healthy patients

Question 20

Describe Occlusal Radiographs

Answer 20

• Limitation w/ CCD or CMOS receptors is size!!!! (Noral size 4 PSP or film receptor measure 3x 2.3 or 7.7 x 5.8 cm)
• Have a LARGER field of view; therefore will see more structures
• Useful when patients do NOT OPEN WIDELY b/c they can’t (truisms) or b/c of cooperation issues
• May be useful in LOCALIZATION (miller technique)
• locate supernumeraries, impactions, root tips.
• foreign bodies, sialoliths, etc
• Other uses:
  1) Visualize maxillary sinus
  2) Trauma patients , fractures, etc
  3) Pathology evaluation

Question 21

What are the Anatomic considerations?

Answer 21

1) Macroglossia- fortunately DO NOT See this often
2) Shallow palate- INCREASE VERTICAL ANGULATION which leaded to INCREASED image distortions

3) Tori
Maxillary: occur in midline & best approach is to move recapture closer to the opposite side of mouth; drawback then is that image of torus may be projected over apices

Mandible: Move receptor closer to midline & many need to adjust horizontal angulation of your beam

4) HIGH muscle attachments- Place receptors SLOWLY; ask pt to RELAX tongue; use COTTON ROLL on top of bite block; biting slowly