Length Determination Flashcards
1
Q
What is the error margin for length determination?
A
0.25-0.5mm
2
Q
What is the optimum working length for best chance of success?
A
0-2mm from radiographic apex
3
Q
What is the mechanism of action of apex locators?
A
- File clip is clipped onto endo file + lip clip placed in mouth
- Weak current is generated between clips and locator detects resistance between the clips
- Variable resistance while passing through canal impedes flow
- Once reach apex resistance decreases suddenly which is detected by locator
4
Q
What are some advantages of apex locators?
A
- More accurate than trying to estimate from radiograph
- Decreased radiation dose
-Perforations easily detected
- Can apex locate during instrumentation phase: better control with curved canals as early detection of decreased working length + decreased open apex
- Confident cleaning and shaping of apex
- Good control of apical constriction
5
Q
What are some disadvantages of apex locators?
A
- False conduction from wet field and metallic restorations and vertical root fractures + lateral canals
- If unable to reach apex can not make accurate measurement can not be made
- If open apex can get variable readings
- Only an additional tool, still need radiographs
- Do not use of patient has pacemaker
- If go to deep due to forgetting to check battery may cause damage to IAN on lower teeth
6
Q
How do you check the corrected working length?
A
- Set rubber stopper to estimated working length
- Place into canal such that rubber stopper at landmark
- Take image and assess if correct position
