Apex locator: A must have equipment to prevent under and over instrumentation of root apex


      Digital technology has become highly prevalent in Endodontics as a result of the rapid growth and advancements in daily dental practice. Endodontic technology has seen a spike in the last few decades with ease of treatment and less fatigue for both dentists as well as patient.

What is the role of an apex locator?     

Working length determination is one of the most crucial steps in root canal treatment. Canal preparation, which involves the removal of all soft tissue and germs from the root canal can be performed by correctly measuring the working length. This is where electronic apex locators come into the picture, which is an effective device, decreasing the number of radiographs required during the treatment and giving an accurate measure of the working length.

These devices measure the impedance, frequency, and resistance of the surrounding material to locate the working length of the root canal to be treated.

The conventional method          

Initially, the traditional method was used to measure the working length wherein files were kept in the canals, and radiographs were taken to see the exact position of the file inside the canal. The drawbacks of these methods are

·         Time- consuming

·         Requirement of multiple x-rays to get the accurate working length

·         Fear of over or under instrumentation of canal

·         File breakage

·         Less efficiency of final root canal treatment


        To overcome all these drawbacks digital dentistry has made tremendous advancements in the field of endodontics. An Apex locator is one such electronic device determining the apical constriction and thus determining the length of the root canal space.

Why apex locators are needed?

The working length determination sets the apical limit for biomechanical preparation as well as obturation without causing any harm to the peri apical tissues. The use of these apex locators helps to prevent

·         Over instrumentation or overfilling of the material

·         Under instrumentation or underfilling of the material

·         Improves efficacy and efficiency of the treatment

·         Consumes less chair side time

·         It helps to detect any perforation, fractures, or resorption


      One such best apex locator in the market with the latest advancement is the Dpex V apex locator by the company Woodpecker. It is a 6th generation apex locator with the anti-interference ability for effective working length determination.

The key features of this device:

·         It has multiple frequency technology for an accurate diagnosis in presence of blood, saliva, or pulp.

·         Measurements are accurate compared to the various other types of apex locator

·         It has a Multicolour 4.5” LCD with an alarm function to ease the operation. The file clip, lip hook, and file probe are autoclavable. The changes in the sound can indicate the position of the file in the root canal.

·         Measurements are not affected by any tooth type


Advantages of Dpex V apex locator

The Dpex V is a 97.78% accurate apex locator with good clinical data matching. It has an innovative algorithm with multi-frequency and anti-interference.

Avoids the influence of subjective factors on measurement results

The trajectory of the file can be clearly shown in different colors on the LCD.


How does the apex locator calculate the working length?


·         Attach the file clip with the K-file

·         Then touch both the file clip and lip hook to check whether the reading comes in negative i.e. “-3”.

·         Place the lip hook on the patient’s mouth

·         As you reach the apex, the reading on the display should reflect a seamless transition with a clear sound for easy measurement.

·         When the file reaches the front region of the apical foramen, the white bars are displayed with the reading till “05” & the high-frequency beep sound comes.

·         When the file has reached the apical constriction, the green bars are displayed with the reading “00”& the beep sound becomes continuous. The zero reading means the file has reached the exact position for working length determination.

·         When the file has exceeded the apical foramen, red bars are displayed along with an alarm sound indicating over instrumentation.


             Regardless of the sort of apex locator used, the most accurate reading is one in which the apex locator reads consistently as the file approaches the apex. Try switching to the next larger size file if the apex locator display is jumpy or fluctuates more.



Digital technology has become highly prevalent and crucial in endodontics as a result of the growth of digitalization in dentistry. The cementoenamel junction is a practical and anatomic endpoint for root canal preparation and obturation. Modern apex locators in endodontics can estimate this point with 90% accuracy so the correct knowledge of the devices with the use of the latest advancement will facilitate the dental practitioner to obtain the desired results.


About the Author:

Dr. Arpita Mohapatra - She is a dental surgeon who works to provide a forum for all dentists to learn about the latest advances and creative technologies in dentistry. She believes that this platform is an excellent approach for her to combine her dental and writing skills to help other dentists.