Apex Locators and Tri Auto ZXApex Locators are the instruments used in Endodontics to determine

the Working length in Root Canal Treatment as an adjunct to

Radiography. They are used to locate the Apical foramen by

determining the Apical constriction or Cementodentinal junction.

These are divided into 4 types based on the way the apex is located

Classification of Apex locators based on Generations:

1st generation Apex locators:

These are also known as Resistance Apex locators. This measures

the opposition to flow of direct current i.e resistance. It is based on

the principle that resistance offered by periodontal ligament and

oral mucous membrane is the same i.e. 6.5 K ohms. It is called as

Sonoexplorer. These apex locators give false readings in the

presence of Blood, pus, chelating agents, irrigants in the root canal.

Advantages of 1st   generation Apex locators:

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Easily operated

Digital read out

Audible indication

Dtects perforation

Can be used with K-file

May incorporate pulp tester

Disadvantages of 1st   generation Apex locators:

Requires a dry field

Patient sensitivity

Requires calibration

Requires good contact with lip clip

Cannot estimate beyond 2mm

Examples:

Neosono Apex locator

2. 2nd Generation Apex Locators:

It works on the principles of Impedance, hence they are also called

as impedance apex locators. They work by measuring opposition to

flow of alternating current or impedance. A major disadvantage of

second generation apex locator is that root canal has to be free

of electro-conductive materials to obtain accurate readings.

Presence of electro-conductive materials to obtain accurate

readings. Presence of electro-conductive irrigants changes the

electric characteristics and lead to inaccurate readings. Examples of

Second generation apex locators.

Examples:

Endocater

Sono explorer

Apex finder endoanalyzer it is a combination of Apex locator and

pulp tester

Digipex

Extract a pex

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Foramatron IV

Pio apex locator

Advantages of 2nd generation Apex locators:

Does not require lip clip

No patient sensitivity

Analog method

Disadvantages of 2nd generation Apex locators:

No digital read out

Difficult to operate

Canal should be free of elecro-conductive irrigants and tissue

fluids

3. 3rd generation apex locator:

They are also called as Frequency dependent apex locator. Works on

the principle of frequency or Comparitive impedence. They are based

on the fact that different sites in canal give difference in impedance

between high (8 KHz) and low (400 Hz) frequencies.The difference in

impedance is least in the coronal part of canal. As the probe goes

deeper into canal, difference increases. It is the greatest at cemento

dentinal junction.

Advantages of 3rd generation apex locator:

Easy to operate

Uses K-type file

Audible indication

Can operate in presence of fluids

Analog read out

Disadvantages of 3rd generation apex locator:

 Requires lip clip

Chances of short circuit

Examples:

Endex

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Root ZX

Neosono Ultima

Mark V plus

Justwo or Justy II

Apex finder A.F.A

4th Generation Apex Locators: 

These measure the resistance and capacitance separately rather

than the resultant impedance value. There can be difference in the

combination of values of capacitance and resistance that provides

the same impedance, thus the same foraminal reading. But by using

4th generation apex locators this can be broken down into primary

components and measures saperately for better accuracy and thus

less chances of occurance of errors.

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Tri Auto ZXTri Auto ZX - Mechanical root canal enlargement with monitoring the file tip.

The Tri Auto ZX is a root canal treatment system with a low speed endodontic handpiece and built in apex locator by J. Morita Mfg. Corp. Mechanical root canal enlargement and the removal of gutta percha points can be performed safely and efficiently.

• Easy to use - cordless for maximum flexibility

• Safer mechanical enlargement - with apical reverse auto start/stop auto torque reverse

• Monitor position of file while cleaning and shaping

• Measuring Function - It can be used as the root canal measuring device.

• Flexible - by nickel titanium files

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References

http://www.juniordentist.com/apex-locators-classification-uses-types.html

http://www.endoexperience.com/documents/electronicapexlocator.pdf

http://www.morita.com/anz/cms/website.php?id=/en/products/dental/endodontic_systems/tri_auto_zx.html

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