The working length
After having realized a minimally invasive access cavity and removed the coronal interferences (preflaring) the next step is passed to the scouting of the apical third canal as described in the two preceding articles of Dr Massimo Giovarruscio (http://styleitaliano.hime.host/scouting-the-root-canal)
The advantages of the apical third scouting only after a preflaring in summary are:
– Best touch control for clinician in negotiating the apical third
– Gradual increase in the amount of available irrigant
– Reduction of the accumulation of dentin chips
– Better control of the apical foramen
The scouting phase terminates with the achievement of the correct working length.
The current, most common, and predictable method in determining the working length is the electronic apex location, which allows to introduce the concept of "electronic apex" that completes and integrates the concepts of anatomy and radiographic apex allowing the clinician to obtain reliable results.
TIPS & TRICKS
- Always take a measure of WL on preoperative rx
- Check the WL during all steps of the endodontic therapy, from scouting to the glide path to the shaping: more curved is canal and more it tends to shorten the WL
- Do the preflaring
- Attention to the presence of metallic restorations that can give false readings
- The reading of the WL must happen gradually in the apex locator scale
- The instrument must have an intimate contact with the canal walls for a correct reading: in presence of large canals use bigger files
- Do not perform readings in the presence of excessive humidity the canal
- Chicago I.L., in Glossary of Endodontic Terms,7th Edition in Ingle's Endodontics Ed :Ingle, Bakland, Baumgartner 6th Edition, Year 2008 BC Decker Inc. New York
- Fouad A.F., Reid L.C. Effect of using electronic apex locators on selected endodontic treatment parameters. Journal of Dental Education, 2000.
- Gutmann JL, Leonard JE. Problem solving in endodontic working-length determination. Compendium of Continuing Education in Dentistry, 1995; 16:288.
- Herrera M, Abalos C, Lucena C, Jimenez-Planas A, Llamas R. Critical diameter of apical foramen and of file size using the Root ZX apex locator: an in vitro study Journal of Endodontics, 2011 Sep; 37(9):1306-9.
- Hoer D., Attin T. The accuracy of electronic working length determination International Endodontic Journal, 2004 Feb; 37(2):125-31.
- Jarad F.D., Albadri S., Gamble C., Burnside G., Fox K., Ashley J.R., Peers G., Preston A.J. - Working length determination in general practice: a randomized controlled trial British Dental Journal, 2011 Dec; 211(12):595-8.
- Keller M.E., Brown C.E. Jr., Newton C.W. A clinical evaluation of the Endocater: an electronic apex locator Journal of Endodontics, 1991 Jun; 17(6):271-4.
- Lu YM, Qin JN, Cao DJ. A study on the accuracy of electronic root canal length measurement and its influential factors. Shanghai Kou Qiang Yi Xue, 2006 Apr; 15(2):140-2.
- Nair M.K., Nair U.P. Digital and advanced imaging in endodontics: a review Journal of Endodontics, 2007; 33:1.
- Odabas M.E., Bodur H., Tulunoglu O., Alacam A. Accuracy of an electronic apex locator: a clinical evaluation in primary molars with and without resorption. Journal of Clinical Pediatric Dentistry, 2011 Spring; 35(3):255-8.
- Parekh V., Taluja C. Comparative study of periapical radiographic techniques with apex locator for endodontic working length estimation: and ex vivo study Journal of Contemporary Dental Practice, 2011 Mar 1; 12(2):131-4.
- Pascon EA, Marrelli M, Congi O, Ciancio R, Miceli F, Version MA. An ex vivo comparison of working length determination by three electronic apex locators - Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontics, 2009 Sep; 108(3):147-51.
- Ravanshad S, Adl A, Anvar J. Effect of working length measurement by electronic apex locator or radiography on the adequacy of final working length: a randomized clinical trial. Journal of Endodontics, 2010 Nov; 36(11):1753-6.
- Saad Y., Al-Nazhan S. Radiation dose reduction during endodontic therapy: a new technique combining an apex locator (Root ZX) and a digital imaging system (RadioVisioGraphy) - Journal of Endodontics, 2000 Mar; 26(3):144-7.
- Smadi L. Comparison between two methods of working length determination and its effect on radiographic extent of root canal filling: a clinical study. BMC Oral Health, 2006 Feb; 11;6:4.
- Stober E.K., De Ribot J., Mercade M., Vera J., Bueno R., Roig M., Duran-Sindreu F. Evaluation of the Raypex 5 and the Mini Apex Locator: an in vivo study. Journal of Endodontics, 2011 Oct; 37(10):1349-52.
- Stober EK, Duran-Sindreu F, Mercade M, Vera J, Bueno R, Roig M. An evaluation of root ZX and iPex apex locators: an in vivo study - Journal of Endodontics, 2011 May; 37(5):608-10.
- Tinaz A.C., Maden M., Aydin C., Turkoz E. The accuracy of three different electronic root canal measuring devices: an in vitro evaluation. Journal of Oral Science, 2002 Jun; 44(2):91-5.
- Topuz O., Uzun O., Tinaz A.C., Sadik B. - Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontics, 2007 Mar; 103(3):73-6.
- Welk A.R., Baumgartner J.C., Marshall J.G. An in vivo comparison of two frequency-based electronic apex locators Journal of Endodontics, 2003 Aug; 29(8):497-500.