ACCURATE WORKING LENGTH DETERMINATION Solaiman Al-Hadlaq B.D.S., M.S., Ph.D
Where to end your root canal preparation? “ The proper point to which root canals should be filled is the junction of the dentin and the cementum and that the pulp should be severed at the point of its union with the periodontal membrane” Groove C., JADA 1930
Methods of Working Length Determination Predetermined normal tooth length Radiographs Tactile sense Paper points Patient response Electronic Apex Locators
1.Tooth apex (radiographic apex) 2.Apical foramen (major foramen) 3.Apical constriction (minor foramen) 12 3 Anatomy of the Root Apex
1 2 3 Johnson WT, Color atlas of Endodontics, 2002 Anatomy of the Root Apex
1 2 3 Distance between 1 and 2: The apical foramen deviates from the apex in 50-98% of the teeth. This deviation averages 0.3 to 0.6 mm but could be as much as 3 mm. Kuttler, JADA, 1955; Green, OOO, 1960; Pineda and Kuttler, Oral Surg, 1972; Burch and Hulen, Oral Surg, 1972; Dummer et al., Int Endo J, 1984 1.Tooth apex (radiographic apex) 2.Apical foramen (major foramen) 3.Apical constriction (minor foramen) Anatomy of the Root Apex
1 2 3 Distance between 2 and 3: 0.5 mm in 18-25 y old, and 0.7 in 55+ y old. Kuttler, JADA, 1955, Distance between 1 and 3: 0.89 mm with a range of 0.1 to 2.7 mm. Dummer et al., Int Endo J, 1984 1.Tooth apex (radiographic apex) 2.Apical foramen (major foramen) 3.Apical constriction (minor foramen) Anatomy of the Root Apex
When radiographic working length in vitro was set to be 0.5 – 2.0 mm short of the apex: 25% of the time the file was beyond the apical foramen. 51% of premolars and 22 % of molars were beyond the apical foramen. 66% of files were longer than a point 0.5 mm shorter than the apical foramen. ElAyouti A et al., J Endodon, 2001
Walton and Torabinejad., Principles and practice of Endodontics, 1996
Electronic Apex Locators The idea of using electrical conductance to measure root length was suggested first by by Cluster in 1918. Cluster LE, J Natl Dent Assoc, 1918
Electronic Apex Locators In 1942 Suzuki noticed a constant value of electrical resistance between an instrument in the root canal and an electrode on the oral mucous membrane and speculated that this would measure canal length. Suzuki K, J Jpn Stomatol, 1942
Electronic Apex Locators In 1962 Sunada took the principle of Suzuki and constructed a simple device that used direct current to measure canal length. This was based on the concept that the resistance between the periodontium and the mucous membrane was constant and equal 6 k . Sunada I, J Dent Res, 1962
Electronic Apex Locators First generation Resistance type based on the principle of Suzuki and Sunada. Root canal meter, Endodontic meter, Dentometer, and Endo Radar. Pain was felt during earlier models due to high currents. Unreliable, electrolytes, exudate, hemorrhage, vital pulp tissue, and excessive moisture caused inaccurate results.
Electronic Apex Locators Second generation Single frequency impedance. Highest impedance at the apical constriction. Need to be calibrated before each use. Sono-Explorer, Endocator (sheath over probe). Incorrect readings with electrolytes in the canal.
Electronic Apex Locators Third generation Multiple frequencies to measure impedance. Calculate difference or ratio of impedance.
Electronic Apex Locators Third generation Endex (Osada Electric, Tokyo, Japan) measures the difference between two impdances. It works in the presence of pus and electrolytes. Needs to be calibrated for each canal.
Electronic Apex Locators Third generation Endex has an average accuracy of 81% to within + 0.5 mm of the apical foramen. InvestigatorAccuracy (%)Test conditionCompared with Fouad et al. (1993)73 (±0.5 mm)In vitro - NaOCITooth length Mayeda et al. (1993)66 (±0.75 mm)In vivoTooth length Frank & Torabinejad (1993)90 (±0.5 mm)In vivoRM Felippe 8< Scares (1994)96.5 (±0.5 mm)In vitroTooth length Arora & Gulabivala (1995)72 (±0.5 mm)In vivoTooth length Pratten & McDonald (1996)82 (±0.5 mm)In vitroRM and tooth length Lauper etal. (1996)93 (±0.5 mm)In vivoTooth length Ounsi & Haddad (1998)85 (±0.5 mm)In vitroTooth length Weiger et al. (1999)59 (±0.5 mm)In vitro - NaOCITooth length De Moor et al. (1999)100 (±0.5 mm)In vitroTooth length Martinez-Lozano et al. (2001)68 (±0.5 mm)In vitroTooth length Accuracy studies for the Endex/ Apit apex locator (Gordon and Chandler, 2004)
Electronic Apex Locators Third generation Root ZX (J. Morita, Tokyo, Japan) measures the ratio of two impedance frequencies. Self calibrating. Was not affected by electrolytes in the canal.
Investigator Variable tested Accuracy (%) Compared with Sample (n) Clinical accuracy permanent teeth in vitro Czerw et al. (1995) Accuracy in vitro 100 (±0.5 mm) Tooth length 30 White et al. (1996) Accuracy in vitro 84 (±0.5 mm) Tooth length 51 Ounsi & Naaman (1999) Accuracy in vitro 85 (±0.5 mm) Tooth length 39 Accuracy in the presence of irrigants Shabahang et al. (1996) Accuracy in vivo 96 (±0.5 mm) Extracted tooth length 26 McGinty et al. (1996) Irrigants and accuracy in vitro No difference Tooth length 16 between irrigants Weiger et al, (1999) Irrigants and accuracy in vitro - NaOCI 85 (±0.5 mm) Tooth length 41 Jenkins era/. (2001) Various irrigants and accuracy in vitro No difference Tooth length 30 Meares & Steiman (2002) Accuracy with NaOCI in vitro 83 (±0.5 mm) Tooth length 40 No difference Clinical accuracy permanent teeth in vivo Vajrabhaya & Accuracy in vivo 100 (±0.5 mm) Extracted tooth length 20 Tepmongkol (1997) Pagavino et al. (1998) Accuracy in vivo - SEM 83 (±0.5 mm) Extracted tooth length 29 100 (±1.0 mm) Dunlap et al. (1998) Accuracy vital versus necrotic in vivo 82 (±0.5 mm) Extracted tooth length 34 McDonald et a/. (1999) Accuracy in vivo 95 (±0.5 mm) Extracted tooth length 20 Welk et al. (2003) Accuracy in vivo 91 (±0.5 mm) Extracted tooth length 32 Minor diameter Clinical accuracy in primary teeth Katz et al. (1996) Accuracy in primary teeth - in vitro 100 (±0.5 mm) Extracted tooth length 20 Mente et al. (2002) Accuracy in resorbed primary teeth – 98 (±1.0 mm) Tooth length 24 In vitro Kielbassa et al. (2003) Accuracy in primary teeth - in vivo 64 (±1.0 mm) Extracted tooth length 71 The properties of the Root ZX (Gordon and Chandler, 2004) Root ZX has an average accuracy of 89 % to within + 0.5 mm of the apical foramen.
Electronic Apex Locators Other third generation apex locators Apex Finder AFA (EIE Analytic Endodontics, CA) Five frequencies 86 % accuracy at –1 + 0.5 mm from radiographic apex. Pommer et al., JOE, 2002 Bingo 1020 (Forum Engineering Technologies, Lishon Lezion, Israel) also marketed as Ray-Pex 4 (Dentsplay). Two separate frequencies No difference between Root ZX or Bingo under different irrigants. Kaufman et al., Int Endo J, 2002
Electronic Apex Locators Other third generation apex locators Justy II (Yoshida Co., Tokyo, Japan) 82 % accuracy in determining the area between minor and major foramen. Hoer and Attin, Int Endo J, 2004. Endy 5000 (Loser, Leverkusen, Germany) 81 % accuracy in determining the area between minor and major foramen. Hoer and Attin, Int Endo J, 2004. Neosono Ultima EZ (Satelec Inc., NJ) 100 % accuracy within 0.5 mm range. De moor et al, Endodon Dent Traumatol, 1999. Mark V plus (Moyco/Union Broach, Bethpage, NY)
Electronic Apex Locators Apex locators with other functions Tri Auto ZX (J. Morita Corp) an apex locator and a rechargeable electric handpiece for NiTi rotary files. 95 % accuracy to within 0.5 mm of the constriction. Gimberg et al., Int Endo J, 2002
Electronic Apex Locators Apex locators with other functions Dentaport ZX (J. Morita Corp) is Root ZX with attached endodontic hand piece for rotary NiTi files.
Electronic Apex Locators Apex locators with other functions Element Diagnostic Unit (SybronEndo, CA) and Apex Locator and EPT.
When radiographic working length in vitro was set to be 0.5 – 2.0 mm short of the apex and using the Root ZX in premolars: The proportion of overestimation was reduced from 51% for radiographic method to 21% when the Root ZX was used. ElAyouti A et al., J Endodon, 2002
Using an apex locator reduces exposure to radiation by minimizing the number of radiographs required to get an acceptable working length radiograph and also produces more accurate working length determination. Brunton P.A. et al., J Endodon, 2002
Third generation Electronic Apex Locators work well in the presence of different irrigants including NaOCl, EDTA, and RC Prep. Jenkins et al., J Endodon, 2001; Kaufman et al., Int Endo J, 2002; Weiger et al., J Endodon, 1999
Preflaring the canal increases the accuracy of Electronic Apex Locator reading (Ibarrola et al., J Endodon, 1999) and tactile sensation (Stabholtz et al., J Endodon, 1995). It also reduces the potential reduction in canal length due to the elimination of curvatures. Cohen and Burns., Pathways of the Pulp, 2002
Apex locators are not affected with the use of stainless steel files or NiTi files. (Thomas et al., J Endodon, 2003; Nekoofar et al., J Cali Dent Assoc, 2002) Apex locators are not affected by the size of the file used (Nguyen et al., Int Endo J, 1996).
Investigator Country Use % Whitten et al. (1996) USA GDPs 10 Saunders et al. (1999) Scotland GDPs 7.7 Yoshikawa et al. (2001) Japan GDPs 90 Chandler & Koshy (2002) New Zealand GDPs 27.5 Specialists 60 Hommez et al. (2003) Belgium GDPs 16 Electronic apex locator use (Gordon and Chandler, 2004) Acceptance of Electronic Apex Locators
Although a recent study have shown no effect of 4 types of Electronic apex locators in vitro on Cardiac Pace Maker (Garofalo et al. J Endodon, 2002). Use in patients with Cardiac Pace Maker should be consulted with their cardiologists.
Limitations of Electronic Apex Locators Touching a metallic restoration will affect performance of Electronic Apex Locators. Leakage of saliva through cervical caries or open margin will also affect Electronic Apex Locators. Immature “Blunderbuss” apex will give short readings on Electronic Apex Locators.
Accurate Working Length Determination A recent preoperative diagnostic quality radiograph is a must. Do not rely on a single method for accurate working length determination. Preflare the canal to increase your tactile sensation. Use an Electronic Apex Locator to determine you working length. Confirm you working length with a radiograph.
Accurate Working Length Determination The key to accurate working length determination is clear understanding of apex anatomy, knowledge of limitations of current techniques, and corroboration of information gained by different methods for working length determination.