Seminar 1: Orthodontic Radiology Flashcards
when writing a radiographic report of an OPT for ortho assessment,
what should you write?
Acceptable
Teeth Present
Apical Pathology
Caries & Restorations
Bone Levels
Other Pathology
&
Justification for xray
what happens if a patient is placed too far forward in an opt machine?
teeth appear narrow/thin
what happens if a patient is placed too far backward in an opt machine?
teeth appear wider on the film
what are ghost images?
shadows created on opposite side of an OPT by the object which caused them
usually caused by METAL OBJECTS, RESTORATIONS, EARRINGS or sometimes NORMAL ANATOMIC FEATURES
When the occlusal plane on an OPT looks like the patient is smiling, what couldve caused this?
patients head is tilted too far downwards
When the occlusal plane on an OPT looks like the patient is SAD, what couldve caused this?
patients head tilted up
when do you request a maxillary occlusal radiograph?
- pathology in anterior region of maxilla
- confirm preference of unerupted teeth
- root resorption sometimes
- parallax (with OPT)
when do you request a periapical radiograph?
- assessing root resorption
- evidence of periapical infection
- assessing ankylosis
- parallax
when would you request bitewing radiographs?
- caries status
- more info on tooth prognosis
- alveolar bone levels
what are the combinations of radiographic views required for parallax?
OPT & Maxillary Occlusal
2 PA’s
When going from an OPT view to a maxillary occlusal view for parallax, what direction is the tube shifted?
Shifted Up
Indications for taking a lateral ceph?
- AP Discepancies
- Vertical discrepancies
Tx planning
- orthodontic & orthognathic planning
Progress monitoring:
- fixed appliance tx
- functional appliance tx
- facial growth monitoring
Important facts about lateral ceph?
- STANDARDISED lateral radiograph of face & base of skull
- REPRODUCIBLE - 1.5m set distance
- head correctly positioned using ear rods and forehead rest
what are important things to analyse in a lateral ceph?
- relationship between jaws & cranial base
- relationship between upper & lower jaw
- position of teeth relative to the jaws
- soft tissue profile
What are all of these?
Reference landmarks
what are all of these?
Reference lines
what is the most common analysis used for looking at lateral cephalograms?
Eastmans analysis
what things are included in EASTMAN ANALYSIS?
- SNA, SNB
- ANB (AP Discrepancy)
- FMPA (Vertical Discrepancy)
Angulation of teeth:
UIMxP: Upper incisor axis & Maxillary plane
LIMnP: Lower incisor axis & Mandibular plane
- Vertical face height proportions [LAFH/TAFH]
AP Discrepancy (ANB) for CLASS 1 Skeletal?
2-4*
AP Discrepancy (ANB) for Class 2 (Mild, Mod, Severe) Skeletal?
Mild: 4-6*
Mod: 6-8*
Sev: >8*
AP Discrepancy (ANB) for Class 3 (Mild, Mod, Severe) Skeletal?
Mild: 0 - 2*
Mod: -3 - 0*
Sev: < -3*
Average FMPA Angle?
27*
Average Measurements for:
- Ui/MxP
- Li/MnP
- Ui/Li
what are some errors in cephalometry?
Radiographic projection errors
- magnification
- distortion
Errors within the measuring system
- non-linear fields
Errors in landmark identification
- quality of image
- landmark definition & location
What is CBCT?
Cone beam computed Tomography (CBCT)
- 3D radiograph, similar but not EXACT as a CT scan
- computer software produces imagines in multiple planes
When do we use CBCT in orthodontics?
- localisation of impacted teeth IF we need more info on proximity to adjacent teeth
- better view of structural anomalies
- some orthognathic & cleft palate cases
why dont we use CBCT more often if its better & more detailed?
- radiation dose to PT is considerably higher than plain films
- Pt setup time takes longer so pt must hold still - high chance for movement causing radiographic errors
- Cost
