Endex Plus Apex Locator

Endex Plus Apex Locator
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The “END” of the root canal is what we are looking for—finding the end is the desired result we must achieve before instrumentation. When we begin a case, the tooth must be evaluated and measured to assess where the apical limit must be set before instrumentation. Knowing the correct apical limit allows us to determine the correct working length. The practitioner who does not know the correct working length may inadvertently:

  • Create an apical perforation;
  • Over-instrument;
  • Over-extend obturation material;
  • Under-prepare the root canal space with inadequate obturation.

Biomechanical preparation with obturation that is not based on an accurate determination of the apical limit could lead to postoperative pain and complications. Determining the correct working length is essential.

An apex locator is currently the only tool for finding the location of the apical foramen, which is usually not at the anatomical apex. The apical foramen and the anatomical apex usually differ by approximately 0.5 mm to 1.0 mm. In older patients, the deviation can be greater. The apex locator locates the apical foramen with great accuracy; the apex locator readout locates the apex or apical foramen and the apical constriction. (The apical foramen is also called the major diameter, while the apical constriction is called the minor diameter.) The practitioner needs to decide which value is to be the working length. The apex locator reliably gives the correct values. Though the radiographic apex is often used as the working length, 50% of the time it does not correspond to the actual apical foramen. This leaves the dentist open to all of the problems enumerated above.

The Endex Plus is the successor to the original third generation Endex by Osada. The Endex Plus and Endex operate on the principle that impedance measurements between two electrodes differ depending on the frequencies used and differ greatly at apical constriction regions. Using an initial reading at the middle of each canal as a reference (reset about 2 to 3 mm from the canal orifice), the Endex Plus and Endex monitor the changes in impedances at 5 kHz and 1kHz as the file probe approaches the apex. The critical apical region is magnified and indicated on the panel meter and by an audio alarm.

While the manual reset method (used in the original Endex) is the most accurate method capable of measuring even difficult cases (such as widely open or perforated teeth), the Endex Plus can give a quick automatic reset as soon as the switch is turned on. The red line on the needle meter indicates the anatomical apex and the green zone approximately indicates the initial apical constriction. The meter magnifies the area of the apical region about 3mm from the apex when the Endex has been reset (auto or manual).

Basic Technique
Once the access has been achieved, remove as much metallic filling material as possible, then remove as much bloody tissue as possible from the canal, leaving the canal moist but not overly wet. The ideal condition for precise readings is to cover the cervix of the canal with a good conducting fluid, such as saline or sodium hypochlorite. Existing conditions with pus, blood etc. in the canal may be easily improved with the addition of such fluid. Excess irrigant in the canal should be reduced to isolate the electrode (inside the root canal) from tissue or fluid outside the canal.

At this point, place the endodontic instrument in the canal and attach it to the clip. The lip clip should be in place on the patients lip to complete the circuit. Advance the endodontic instrument into the canal. The new Endex Plus will automatically reset using the auto-reset mode. This will be achieved when the blue auto-reset lamp goes on. Continue down the canal until the desired end is reached. I usually go to the red line marked “Apex.” I have found that in at least 10% of cases the blue light will not go on and the Endex will not work in the auto mode. When this happens I remove the endo instrument from the canal and turn off the unit. I then switch the setting to manual and turn the unit back on. I proceed into the canal and hit the manual reset button when the endo instrument is in the canal approximately 3-5mm. The green lamp lights when the manual reset is completed. The endo instrument is advanced until the apical setting that you desire is reached.

The availability of both an auto and manual setting for taring the instrument is a great asset. I have used other apex locators that just have an auto tare feature. I could not get a reading in approximately 10% of the cases. The Endex offers a fallback position with the availability of the manual mode when needed. In our multi-endodontist office we have been using this instrument for about two years. We are all extremely happy with its ease of use and clinical accuracy. Our cases look good and, best of all, our patients feel good.

Review Synopsis

Product
Endex Plus Apex Locator
The Good

The availability of both an auto and manual setting for taring the instrument is a great asset.

The Bad

I could not get a reading in approximately 10% of the cases.

The Bottom Line

We are all extremely happy with its ease of use and clinical accuracy.

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