Working length

“ I shall be telling this with a sigh Somewhere ages and ages hence; Two roads diverged in a wood, and I took the road less traveled by, And that has made all the difference.”

Robert Frost.

Good Morning

NON RADIOGRAPHIC WORKING LENGTH DETERMINATION

MOHD.SIBGHATULLAH KHATIB2ND YEAR PG STUDENT

Contents

Introduction

Anatomical considerations and terminology

Methods of determination of working length.

Clinical significances.

Conclusion.

References

INTRODUCTION

• ‘‘The distance from the coronal reference point to the point at which canal preparation and Obturation should terminate”.

INGLE 6TH EDITION

ANATOMY OF THE APICAL CANAL

Methods of determination of working length

1. RADIOGRAPHIC METHODS.2. ELECTRONIC METHODS.3. DIGITAL TACTILE SENSE METHOD.4. PAPER POINT MEASUREMENT.5. PATIENT RESPONSE

NON RADIOGRAPHICAL METHOD

1. DIGITAL TACTILE SENSE METHOD.

2. PAPER POINT MEASUREMENT.3. PATIENT RESPONSE4. ELECTRONIC METHODS.

Digital tactile sense

• The most common methods are radiographic methods, digital tactile sense, patients’ response to a file introduced into the canal, or a point to which a paper point can be placed and removed dry.

INGLE 6TH EDITION

• Seidberg et al. reported an accuracy in WL determination of just 64% using digital tactile sense.

• If the canals were preflared, it was possible for an expert to detect the apical constrictionin about 75% of the cases.

• If the canals were not preflared, determination of the apical constriction by tactile sensation was possible in only about one-third of the cases.

INGLE 6TH EDITION

Paper point method

• In a root canal with an immature (i.e., wide open) apex, a relatively reliable means of determining WL is by gently passing the blunt end of a paper point into the canal after profound anesthesia has been achieved.

• The moisture or blood on the portion of the paper point that passes beyond the apex may be an estimation of WL

INGLE 6TH EDITION

• A shortcoming of the technique is that if periapical soft tissues extend into the canal, underestimation of the working length could result.

• Rosenberg (2003) cautioned that the paper point should only remain in brief contact before any capillary action has taken place

International Endodontic Journal, 46, 483–491, 2013

ELECTRONIC METHODS

HISTORY

• CUSTER(1918) -Report the use of electric current to determine working length.

• Suzuki found that an electrode placed on the oral mucosa, and an instrument placed in the root canal, gave consistent measurements of electrical resistance. This is the basis for the resistance-based EALs

INGLE 6TH EDITION

• Sunada found that when the file reached the canal terminus, regardless of tooth shape, tooth type, or age of the patient, the resistance measured was consistent at 6.5 KΩ.

INGLE 6TH EDITION

HISTORY

How to measure the root canal by using EAL?

J Med Dent Sci 2007; 54: 125–136

International Dental Journal of Student’s Research, December 2015;3(4):159-162

Generation Electronic Apex Locators

• RESISTANCE apex locators• Principles: Measures opposition to the flow of direct

current (or) resistance.• When the file of the reamer reaches the apex in the

canal, the resistance value is 6.5 kΩ

J Med Dent Sci 2007; 54: 125–136

• Pain was often felt due to high electric currents.

• Strong electrolytes lead to inaccurate and even unstable results

• The more recent resistance-based apex locators provided accurate location of the apical constriction 55 to 75% of the time. However, their accuracy was still diminished in the presence of fluids

J Med Dent Sci 2007; 54: 125–136

INGLE 6TH EDITION

Example

• Root canal meter (Onuki medical Co.tokyo, Japan)

• Endodontic meter(Onuki medical Co.tokyo, Japan)

• Dentometer (Dahlin ectromedicine, Copenhagen, Denmark)

• Endo Radar (Electronica liarre, Imola, Italy)

Mosleh, et al.: Electronic apex locator


• Impedance apex locator

• Principle: Measures opposition to the flow of alternating current (or) impedance

• Developed in 1980’s to improve the resistance type apex locators

J Med Dent Sci 2007; 54: 125–136

• Sono-Explorer (Hayashi Dental Supply, Tokyo, Japan)• Endo Cater (Yamaura Seisokushu, Tokyo, Japan)• Digipex (Mada Equipment Co.Carlstadt, NJ, USA)• Exact-A-Pex (Ellman International Hewlett, NY, USA)• Formatron IV (Parkell Dental, Farmingdale, NY, USA)• Endodontic Meter S II (Onuki Medical Co., Tokyo,

Japan)• Sono-Explorer Mark II (Hayashi Dental Supply, Tokyo,

Japan).• Sono-Explorer Mark II Junior (Hayashi Dental Supply,

Tokyo, Japan)


Example

Accuracy studies for second generation apex locators


• Fouad et al. found that the Sono-Explorer Mark III to be accurate to + 0.5 mm from the AF 75% of the time & the Endocator to be accurate to + 0.5 mm from the AF 75% of the time.

• Himel & Cain found that the Foramatron IV to be accurate to +0.5 mm from the radiograph apex 65% of the time and within 1.0 mm 83% of the time.

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• Third-generation EALs are similar to the 2nd generation apex locator except that they use multiple frequencies to determine the distance from the end of the canal.

• These units have more powerful microprocessors

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• Endex/Apit (Osada Electrica Co. Tokyo, Japan)• Root ZX (J.Morita, Tokyo, Japan)• TCM Endo V (Nouvag Ag, Goldach, Switzerland)• Dat Apex (Dentsply Maillerfer, Ballaiques, Switzerland)• Just or Justy II (Yoshida Co.Yokyo, Japan)• Mark V Plus (Moyco/Union Broach, Bethpage, NY, USA)• Mini Apex Locator (Sybron Endo, Anaheim, CA, USA)• Dentaport ZX (J. Morita MFG Corp., Osaka, Japan)• Justwo or Justy II (Yoshida Co., Tokyo, Japan).• Mark V Plus (Moyco/Union Broach, Bethpage, New York,

USA).• Endox (Co. Lysis, Milan, Italy).• Endy (Loser, Leverkusen, Germany)

Example

• Neosono Ultima EZ (Satelec Inc., Mount Laurel, New Jersey, USA) is also known as the DatApex (Dentsply Maillefer, Ballaigues, Switzerland).

• Raypex 5, (VDW, Munich, Germany).• Foramatron D10 (Parkell Electronic Division, Farmingdale,

New York, USA).• Apex NRG (Kibbutz Afikim, Israel).• Apit 7 (Osada, Tokyo, Japan).• Neosono MC (Amadent Medical and Dental, Co.,Cherry Hill,

New Jersey, USA).• NovApex (Forum Technologies, Rishon Le-Zion, Israel).

J Med Dent Sci 2007; 54: 125–136

Example

• The device operates most accurately when the canal is filled with electrolyte such as saline or sodium hypochlorite.

• Needs “reset” or “calibrated” for each canal

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The Endex/Apit-

Accuracy studies for the Endex/ Apit apex locator


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The Root ZX(J. Morita Co., Kyoto, Japan)

•Uses dual-frequency

•The electronic method employed was the “ratio method.” The Root ZX simultaneously measures two impedances at two frequencies (8 and 0.4 kHz) inside the canal.

•A microprocessor in the device calculates the ratio of the two impedances. The quotient of the impedances is displayed on a liquid crystal display meter panel and represents the position of the instrument tip inside the canal

The Apex Finder AFA (all fluids allowed)

• The unit is self-calibrating and can measure with electrolytes present in the canal

• It detect the apical constriction in 76.6% of necrotic canals but was effective for 93.9% of vital canals

Pommer et al. 2002

• An accuracy of 95% in locating to within 0.5 mm of the CDJ in patients

McDonald et al. 1999


• Haffner et al. evaluated in vivo the accuracy of four EALs: Root ZX, Endy, Just II and Endox, to determine the working length.

• They reported that within the limit of 0.5 mm from the AC was attained –Root ZX - 78%Endy - 67%Justy II - 80% Endox - 31%

J Med Dent Sci 2007; 54: 125–136

• Lucena-Martin et al. evaluated in vitro the accuracy of three EALs: Justy II, Root ZX and Neosono Ultima EZ63.

• They reported that EAL reliability in detecting the apex – Justy II -80% to 85% Neosono-85% to 90% Root ZX -85%

J Med Dent Sci 2007; 54: 125–136

• Goldberg et al. evaluated in vitro the accuracy of three EALs: ProPex, NovApex and Root ZX, in determining the working length during the retreatment process.

• They reported that the ProPex, NovApex and Root ZX were accurate within 0.5 mm 80%, 85%, and 95% of the time, and within 1.0 mm 95%, 95% and 100%, respectively.

J Med Dent Sci 2007; 54: 125–136

• Fan et al. evaluated the accuracy of the Root ZX, the Neosono Ultima EZ and the ProPex EALs under different electrolyte conditions and different size of AF using a standardized model of glass tubules.

• They stated that the ProPex and Neosono Ultima EZ were more accurate than the Root ZX under various conditions in this laboratory study..

J Med Dent Sci 2007; 54: 125–136

• Tslenik et al. compared the accuracy of the Root ZX and the Elements-Diagnostic EALs in detecting the minor constriction in vivo under clinical conditions.

• Root ZX was accurate 75% of the time to ≈0.5 mm, 83.3% ≈0.75 mm, and 88.9% to ≈1.0 mm. The Elements-Diagnostic was accurate 75% of the time to ≈0.5 mm, 88.9% to ≈0.75 mm, and 91.7% to ≈1.0 mm

J Med Dent Sci 2007; 54: 125–136

• Wrbas et al. compared the accuracy of two EALs: Root ZX and Raypex 5, under clinical conditions, in detecting the minor diameter in the same tooth.

• The minor diameter was located within the limits of ≈0.5 mm in 75% of the cases with the Root ZX and 80% of the cases with Raypex 5

J Med Dent Sci 2007; 54: 125–136

J Med Dent Sci 2007; 54: 125–136

• A fourth generation device and the unit use two separate frequencies 400 HZ and 8 KHZ similar to the 3rd generation units.



• Bingo1020/Raypex4 (Foroum Engineering Technologies Rishon Lezion, Israel)

• Raypex4 (VDW, Munich, Germany)• Element Dianostic Unit & Apex Locator (Sybron Endo, Anaheim,

CA, USA)• Neosono MC (Amadent Medical and Dental, Co.,Cherry Hill, New

Jersey, USA).• Propex (Dentsply Maillerfer, Ballaiques, Switzerland)• Novapex (Foroum Engineering Technologies Rishon Lezion, Israel)• Apex NRG XFR (Medic NRG Ltd, Tel Aviv, Israel)• Apex DSP (Septodont, Saint-Maur des Fosse´s, Cedex, France)• AFA Apex Finder, Model 7005 (Ana-lytic Endodontics, Orange, CA)• iPex (NSK Ltd, Tokyo, Japan)• Romi Apex D-30 (Romidan LTD, Kiryat-ono, Israel)


Example

Bingo 1020/Ray-Pex 4

• An in vitro study of the Bingo 1020 found it to be as reliable as the Root ZX and also user friendly

Kaufman et al. 2002

• The Bingo1020 to be as accurate as the Root ZX in an in vitro study

Tinaz et al.2002

• It is easier for a beginner to use in preflared canals. This unit has subsequently been marketed by Dentsply as the Ray-Pex 4


Elements Diagnostic Unit and Apex Locator


• It uses a composite waveform of two signals, 0.5 and 4 kHz, compared with the Root ZX at 8 and 0.4 kHz.

• The signals go through a digital-to-analogue converter to be converted into an analogue signal, which then goes through amplification and then to the patient circuit model which is assumed to be a resistor and capacitor in parallel. The feedback signal waveforms are then fed into a noise reduction circuit

• Both the Root ZX and Raypex 5 showed the accuracy of the results to the extent of 96.6% and 93.2% accurate in detecting the minor diameter to the strictest acceptable range of 0.5 mm.

• Raypex 5 is as effective as Root zx in determining the minor diameter

• DentaPort ZX was accurate in 93.3% of the samples and iPex was accurate in 90% of the samples at a position 0.5 mm short of the apical foramen. There was no statistically significant difference between the two apex locators


• The Root ZX located the minor foramen correctly 68% of the time in anterior and premolar teeth, and 58% of the time in molar teeth.

• The Elements-Diagnostic located the minor foramen correctly 58% of the time in anterior and premolar teeth and 49% of the time in molar teeth. Radiographs located the minor foramen correctly 20% of the time in anterior and premolar teeth and 11% of the time in molar teeth.

COMBINATION OF APEX LOCATOR & ENDONTIC HANDPIECE

• The Tri Auto ZX is primarily a cordless automatic, endodontic handpiece with a built in Root ZX apex locator.

• The hand piece uses nickel titanium rotary instruments that rotates at 280 ± 50rpm.

• The position of the tip of the rotary instrument is monitored on the LED control panel of the handpiece during the shaping and cleaning of the canal

• Three automatic safety mechanisms• Auto start-stop mechanism- The hand piece

automatically starts rotation when the instrument enters the canal and stops when the instrument is removed.

• Auto torque reverse mechanism-The handpiece automatically stops and reverses the rotation of the instrument when the torque threshold (30gms /centimeter) is exceeded.

• Auto – apical – reverse mechanism- The handpiece automatically stops and reverses rotation when the apical constriction that has been preset by the clinician.

• Developed in 2003

• Measure the capacitance and resistance separatelyJournal of Dental science & oral rehabilitation 2013

• Examle -Propex II (Dentsply Maillerfer, Ballaiques, Switzerland)

Apex Locator Joypex 5 (Henan, CBD Neihuan Road, Zhengzhou, China)

I-ROOT (E-Magic Finder)(S-Denti SEoul, South Korea)




• Adaptive apex locator overcome as the disadvantages of the popular apex locator 4th generation low accuracy on working in wet canals,as well the disadvantages of device Vth generation difficulty on working in dry canal.

Journal of Dental science & oral rehabilitation 2013

• Adaptive apex locator continuously defines humidity of the canal and immediately adapt to dry or wet canal.

• This is why it is possible to be used in dry canal or wet canal as well , canal with blood or exudates, canal with not extripitated pulp

Journal of Dental science & oral rehabilitation 2013

Problems Associated with the Use ofElectronic Apex Locators

• Fan et al. used different diameters of glass tubules in their study to mimic root canals.When they filled the canals with less conductive electrolytes such as 3% hydrogen peroxide the accuracy of the real length within 1.0 mm was 75–100% despite the increase in tubule diameter.

• When they filled the canals with strong electrolytes such as 0.9% saline solution, 2.5% sodium hypochlorite solution and 17% ethylenediamine tetraacetic acid (EDTA), the accuracy of the Root ZX decreased as the tubule diameter increased.

J Med Dent Sci 2007; 54: 125–136

• McDonald recommended the use of files with sizes comparable with the root canal diameter, claiming that this would result in more accurate readings.

• Ebrahim et al. evaluated in vitro the effect of file size on the accuracy of Root ZX when sodium hypochlorite or blood was present during electronic measurements in enlarged root canals.

• They found that as the diameter of the root canal increased, the measured length with the smaller size files became shorter.

J Med Dent Sci 2007; 54: 125–136

• A file of a size close to the prepared canal diameter should be used for root length measurement in the presence of blood, and possibly serum or pus .

• In the presence of sodium hypochlorite, the Root ZX was highly accurate even when the file was much smaller than the diameter of the canal

J Med Dent Sci 2007; 54: 125–136

• Azabal et al. found the Justy II apex locator (3rd gen) was able to detect simulated horizontal root fractures but was unreliable when measuring simulated vertical root fractures.

• Oishi et al. investigated whether constriction of the root canal could be recognized by using an EAL. They reported that the Root ZX apex locator was not only effective for accurately detecting the location of the AF but also useful for detecting root canal constrictions

J Med Dent Sci 2007; 54: 125–136

• Ebrahim et al. evaluated in vitro the accuracy of five different 3GEALs: Dentaport ZX, APEX LOCATORS ProPex, Foramatron D10, Apex NRG and Apit 7, in determining the working length in teeth after removal of root canal obturation materials.

• They found that the Dentaport ZX, ProPex and Foramatron D10 were more accurate than the other two EALs in determining the working length in teeth after removing the root canal obturation materials.

• However, the Apex NRG and Apit 7 were also reliable for

determination of the working length in majority of the cases.

J Med Dent Sci 2007; 54: 125–136

Cardiac Pacemaker

• Electrical devices such as electric pulp tester, EALs, and electrosurgical instruments has been potential interfere with cardiac pacemaker.

• Garofalo et al. reported that four out of five 3rd gen. tested with a single cardiac pacemaker showed normal pacing and only one produced an irregular pace recording on an oscilloscope.

J Med Dent Sci 2007; 54: 125–136

• Wilson et al.was determine in vitro if EALs or electric pulp testers interfere with the function of implanted cardiac pacemakers or cardioverter/defibrillators.

• They concluded that EAL or electric pulp testers are safe for use in patients with cardiac pacemakers or cardioverter/defibrillators.

• As this study was not clinical it might beprudent to confer with the patients cardiologist prior to treatment.

J Med Dent Sci 2007; 54: 125–136

ADVANTAGES • Only method that can

measure length up to apical foramen, not to radiographic apex..

• Accurate• Easy and fast• Reduction of X-ray

exposures• Artificial perforation can be

recognized

DISADVANTAGES• Requires special device• Accuracy is influenced by

electrical condition of canal

• Difficult in teeth with wide open apex.

• Inconsistent results in cases of vital teeth (except newly developed devices).

ELECTRONIC METHODS

Conclusion

• No individual technique is truly satisfactory in determining endodontic working length.

• Knowledge of apical anatomy, prudent use of radiographs and the correct use of an electronic apex locator will assist practitioners to achieve predictable.

• Based on biological principal and experimental evidence instrumentation (or) obturation should not extend beyond the apical foramen).

References • INGLE 6TH EDITION• Journal of Conservative Dentistry | Nov-Dec 2013 | Vol 16 |

Issue 6• Journal of Conservative Dentistry | Jul-Aug 2015 | Vol 18 |

Issue 4• Journal of Dental science & oral rehabilitation 2013 • J Med Dent Sci 2007; 54: 125–136• International Endodontic Journal, 37, 425–437, 2004• International Endodontic Journal, 43, 16–20, 2010• International Endodontic Journal, 39, 595–609, 2006• International Endodontic Journal, 46, 483–491, 2013• International Dental Journal of Student’s Research, December

2015;3(4):159-162

Education

Working length