electronic apex locators Flashcards
What is the anatomical apex?
End of root from a macro perspective
Doesn’t take into account micro anatomy
What is radiographic apex?
End of root determined by radiograph
Foramen located to one side of apex
Varies from 0.3-3mm
Deposition of cementum can cause discrepancies
Pathology, eg external resorption can change position
USEFUL BUT INACCURATE
What is major apical constriction?
Widest point of foramen
Entirely within cementum
Not ideal finish point as not a natural stop
What is minor apical constriction?
Narrowest point of foramen
Location is variable
Usually 0.5-1mm short of r. apex
Point where cementum fuses w dentine (CDJ)
What is the CDJ?
Point where cementum fuses w radicular dentine
Considered point where RC finishes and periodontium begins
Can only be detected histologically
Can be irregular in height
NOT A PRACTICAL LANDMARK
Why do we use the minor apical constriction?
Narrowest point
Good natural barrier
Consistent reference point
Most practical
What are the different minor apical constrictions?
TYPE A- traditional single
TYPE B- tapering down
TYPE C- multi constricted
TYPE D- parallel constricted
How can you determine WL?
1. Tactile feedback
2. Paper point technique
3. Radiographic
4. Electronic apex locator
What is tactile feedback?
Essential
Experienced endo could only detect in 60% cases
More complicated w sclerosis, resorption, anatomical differences
NOT RECOMMENDED
What is the paper point technique?
RC system is dry
Periodontium is wet
Wet dry interface is reference point
Placed incrementally at shorter lengths until no moisture
Useful for open apices/abnormal anatomy
Complicated by apical exudate in infected cases/patency not achieved
NOT RECOMMENDED
What is the radiographic technique?
Most commonly used
Paralleling technique
Flaw- apical constriction can be more than 0.5-1mm away- over instrumentation
Difficult- overlying structures/superimposition of canals
Exposes pt to ionising radiation
What is electronic apex locator?
Commonly used
Modern- v reliable (Root ZX)
Uses resistance/impedance of root canal and PDL
Can use as sole method but MUST have a GP confirmation xray
How do you use an electronic apex locator?
Advance file til you get a single line on the red part (APEX)
This means you have just gone through the MAC and have reached the peridontium
Need to deduct 0.5mm to get WL
The numbers don’t indicate mm
Clip goes onto file
Hook on cheek/or touching skin
Creates circuit
How does the electronic apex locator work?
Tooth=capacitor
Dentine/cementum=insulators of current
PDL/MAC/file in canal= conductors of electricity
Advancing file and PDL= conductors in capacitor
What are the different types of apex locators?
FIRST GEN
- resistance based
- 6.5kW
- accurate when dry but significantly affected by exudate, pulp tissue, haemorrhage, electrolytes
- small electric shock sometimes
SECOND GEN
- impedance based
- still affected by electrolytes
- highly variable
- not accurate enough
THIRD GEN
- multiple frequencies
- calibrated to detect
- abnormal MAC may misread
- improved w electrolytes
- 83-100% accuracy
- can be attached to rotary but not as accurate
FOURTH GEN
- 2 frequencies, one at a time
- reduces noise from multiple, no need for filter
- but 3rd and 4th gen equally accurate
