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Laurence Bohan 
Content Writer
Laurence Bohan 
Content Writer

Laurence is a copywriter and trained journalist. His passion is creating insightful and educational content for dental professionals of every level. Outside of work, he enjoys watching sport, quizzing and spending time with his family.

Why is Measuring Working Length Important?

Successful root canal treatment depends on being able to accurately determine working length. Working length is essentially how far into the canal endodontic files and obturators can be placed and worked. For every millimetre short or long this estimation, the chances of a successful outcome lessen.

Risks of overextended working length include:

  • Perforation through apical constriction (narrowest apical portion of the root canal)
  • Overfilling of root canal
  • Increased chances of postoperative pain
  • Prolonged healing period

Risks of underestimating working length include:

  • Incomplete cleaning and instrumentation of canal
  • Under filling of root canal
  • Incomplete apical seal
  • Poor healing


How Does the Optima E+ Endo Motor Determine Working Length?


The Optima E+ relies on the same technology as electronic apex locators whereby the patient’s body is used to complete an electrical circuit. A measuring wire with two sockets is plugged into the motor. One socket is used for connecting the lip clip that attaches to the patient’s mouth and the other socket is used for connecting the file clip that attaches to the endodontic file.


The circuit is completed when the file contacts the apical foramen (the apex of the tooth). This is the point where the pulp meets the periodontal tissues that surround and support the tooth. This reference point is indicated when a reading of 00 begins flashing on the motor’s digital OLED display screen. As the file approaches the apex, the Optima E+’s Apical Slow Down function can automatically reduce the speed of the motor to alert the dentist.


This function is activated when the motor is being used in either the CW (clockwise rotation) or CCW (counterclockwise rotation) operation mode. It can be disabled if preferred.




How to Read the Optima E+ Display Screen



The motor’s display appears when a file is inside the canal and the lip hook is in contact with the patient’s mouth. Bars in meter show the location of the file tip. The meter numbers 1.0, 2.0, 3.0 and digital numbers 00-16 do not represent the actual length from the apical foramen. It simply indicates the file progression towards the apex. The digital numbers -1 and -2 indicate that the file has passed the apex foramen. The digital number “00” indicates that the file has reached the apex foramen. Subtract 0.5-1mm from the measured file length as the working length. These numbers are used to estimate the canal’s working length.
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