working length

[burnish33]

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i have another question, you know how you want to establish working lenght about 1mm from the radiographic apex? well, what if the canal of , lets say a molar, doesn't exit at the apex, but at the side of the root, then do you set your WL from the root apex, or from where the canal ends?

 

[tinman831]

I thought the reason you want to measure the WL 0.5-1mm from the apex is to account for the fact that the apical foramen doesn't always exit at the radiographic apex?

 

[burnish33]

yes, you're right , I guess what I meant is what if the canal curves greater than 1mm away from the apex and exits the root laterally, so do you just fill the canal with gutta percha all the way to the exit point? or 1mm away from where it exits laterally? So i guess what i'm saying is if it curves laterally, do you fill the entire canal?? Sorry this sounds so confusing, maybe i'm missing something... ?

 

[NileBDS]

I thought the reason you want to measure the WL 0.5-1mm from the apex is to account for the fact that the apical foramen doesn't always exit at the radiographic apex?

Yes and No. The main reason you do not want to extend your WL to be flush with your root apex is in part because the junction where the Cementum meets the Dentin (CDJ) the tooth structure tends to be thin/brittle. You do not want to fracture that thin bridge with apical pressure while condensing (creating a ditch).

If you think of it also, even if your root is straight like an arrow, and your apical foramen is aligned with the root apex, the most constricted part of the root canal system (anatomically) is not at the root apex, but at the apical foramen (0.25-0.5mm shy of the actual apex). Think of the last 0.25-0.5mm being shaped like an hour glass.

 

[NileBDS]

i have another question, you know how you want to establish working lenght about 1mm from the radiographic apex? well, what if the canal of , lets say a molar, doesn't exit at the apex, but at the side of the root, then do you set your WL from the root apex, or from where the canal ends?

You set your WL to wherever your apex locator tells you to set it. You can always verify your WL afterwards with a radiograph also.

Apex locator (root ZX) has a respected %90+ accuracy rate, backed by studies, clinical practice and case reports.

To answer your question, you would set it 0.5mm shy of where the canal ends (apical foramen), not the apex (cementum).

 

[dheav005]

this is why the three endo guys at my clinic view radiographs as secondary evidence of canal length. patency is determined with the apex locator, to a full tone. the measured length is backed off by .5-1.0mm and WL radiographs are taken. by using the apex locator (and the literature does indicate the current crop are consistently better than radiographs alone), you account for any variation between radiographic apex and anatomic apex as well as avoiding blowing out the minor constriction. i have found this to be much easier than relaying on radiographs...i have taken out enough failed endo molars to see that careful radiographs can still leave you overextended in the end.