Apex Locators

Question 1

In terms of WL what increase chance failure?

Answer 1

More 2mm short

Extend beyond apex

Question 2

Anatomical apex?

Answer 2

End of root from macro-perspective

Question 3

What is radiographic apex?

Answer 3

Similar anatomical

Dertmined by radiograph

Question 4

Why is radiographic apex inaccurate?

Answer 4

Foramen often at ride of apex - varies usually 0.3-0.6mm

Question 5

What is major apical constriction?

Answer 5

Widest point foramen

Question 6

Issue with WL being major apical constriction?

Answer 6

No natural stop for filling materia

Question 7

What is minor apical constriction?

Answer 7

Narrowest point of foramen - usually 0.5-1mm short radiographic apex

Question 8

Ideal limit of root filling?

Answer 8

At CDJ - considered point canal system finish and periodontium begins

Question 9

Why CDJ not practical to use?

Answer 9

Only detected on histology

Question 10

Method determine WL?

Answer 10

Tactile feel
Paper point
Radiographic determination
Electronic apex locator

Question 11

Issue w/ tactile feel?

Answer 11

Not reducible / tricky

Question 12

What is paper point technique?

Answer 12

Based on premise root canal system of uninfected tooth is dry while periodontium is wet - use wet/dry interface

Question 13

How use radiographic determination?

Answer 13

Must use parallelling technique

Premise apical constriction 0.5-1mm short radiographic apex

Question 14

Disadv radiographic determination?

Answer 14

Diff to determine if superimposition of canals

Expose pt ionising radiation

Question 15

Most commonly used method of WL?

Answer 15

Reliable - uses resistance/ impedance of root canal/PDL

Question 16

How use electronic apex locator?

Answer 16

Electrical circuit formed 
Light green at nears apex
Red line = into PDL 
Aim for green 
Measure file with stopped and deduct 0.5mm so otherside apical constriction

Question 17

Why take 0.5mm away apex locator reading?

Answer 17

Don’t want filling in contact w/ PDL

Question 18

What would cause problem when using apex locator?

Answer 18

Amalgam
Perforations
Lateral canals

Question 19

Why are amalgam issue w/ apex lcoator?

Answer 19

Metallic short cut locator = mis-reading

Question 20

Why perforation issue w/ apex lcoator?

Answer 20

Trigger apex response as contact PDL

Question 21

How can using apex locator on perforation be advantageous?

Answer 21

If unsure if have perforation

Question 22

If using apex locator can skip pre-op radiograph?

Answer 22

No always need pre-op radiograph

Question 23

When accept apex reading?

Answer 23

Bar is stable and moves with movement of file