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References

Ingle JI, Himel VT, Hawrish CE, Glickman GN, Serene T, Rosenberg PA, Buchanan S, West JD, Ruddle CJ, Camp JH, Roane JB, Cecchini SB Endodontic cavity preparation, 5th edn. In: Ingle JI, Bakland LK (eds). London: BC Decker; 2002
Davis RD, Marshall JG, Baumgartner JC Effect of early coronal flaring on working length change in curved canals using rotary nickel-titanium versus stainless steel instruments. J Endod. 2002; 28:438-442

Dynamic working length determination

From Volume 41, Issue 2, March 2014 | Page 185

Authors

Vito Antonio Malagnino

MDS, DDS

Professor University of Chieti-Pescara, Chieti, Italy

Articles by Vito Antonio Malagnino

Luigi Canullo

DDS

Private Practice, Rome, Italy

Articles by Luigi Canullo

Giampiero Rossi-Fedele

DDS, MClinDent, PhD

University of Warwick, UK

Articles by Giampiero Rossi-Fedele

Article

Accurate determination of working length is an important step in root canal instrumentation, as incorrect preparation length can lead to:

  • Inadequate cleaning and shaping of root canal space;
  • Apical foramen perforation;
  • Periapical tissue damage;
  • Difficulties in controlling obturation length; and
  • Post-operative pain.1

    • It has been shown that the working length of a canal decreases after root canal preparation.2 Therefore, constant reconfirmation of the preparation endpoint is desirable. This is normally achieved by using an ‘apex locator’ in combination with regular radiographic controls.

    The ‘dynamic working length determination’ technique requires the preparation of a ligature on the endodontic handpiece using a stainless-steel orthodontic wire (Figure 1). The apex locator circuitry (the ‘file holder’ part) is directly connected to the ligature, rather than to the file, and the lip clip is connected to the patient's body to complete an electric circuit. It should be noted that this technique is not possible if the endodontic handpiece contains ceramic components, as they will interfere with the electric circuit. It is worth mentioning that some ‘apex locators’ provide delayed readings, thus these should not be used for ‘dynamic working length determination’, as there is a risk of overinstrumentation as a result of this factor.

    Figure 1. A stainless-steel orthodontic wire is attached to the endodontic handpiece to create a ligature.

    Combinations of ‘apex locator’ and endodontic handpieces and motors are available on the market, with simultaneous preparation and measuring functions; apart from the need to purchase further equipment, the combination ‘apex locator’ and handpiece size is larger than standard ones, making it more difficult to position when working on posterior segments. Furthermore, they might not be fully autoclavable, as an ‘apex locator’ is incorporated in the handpiece.

    The values of this technique are that:

  • It allows for continuous monitoring of the position of the apical foramen in relation to the rotating instrument;
  • If a mechanical glide path is opted for, there is control of the working length from the early stages of the procedure;
  • There is no need to purchase and maintain further specific equipment.