1. dr VLADIMIR IVANOVIC, DDS, MSc, PhD, SDS
Professor in Restorative Odontology & Endodontics,
University of Belgrade, Republic of Serbia 1

2. Katarina Beljić- Ivanović
Mirjana Vujašković
Katarina Beljić- Ivanović
Jugoslav Ilić
Ivana Bošnjak
L E N G T H
THE WORKING
L E N G T H
DETERMINING 2

3. TO LOCATE THE APICAL TERMINUS OF THE ROOT CANAL PREPARATION
SEEKING WHERE,
WHEN, WHY AND HOW
Joshua Moshonov
TO LOCATE
THE APICAL
TERMINUS
Julian Webber
Paul Dummer
OF THE ROOT
CANAL
PREPARATION
William Saunders

4. Articles that have been “guiding light” in creating my own standpoints, and directing “pathways” of this lecture by their philosopohy and conception
Apical limit of root canal instrumentation and obturation (1 & 2)
D Ricucci & K Langeland, 1998, IEJ
Apical terminus location of root canal treatment procedures.
M-K Wu, P Wesselink & RE Walton, 2000, 4O’s & Endo
Considerations in working length determination.
LRG Fava & JF Siqueira, 2000, Endodontic Practice
The fundamental operating priciples of ERCLMDs.
MH Nekoofar, SJ Hayes & PMH Dummer, 2006, IEJ
Determination of true working length.
R Mounce, 2007, EndoPractice

5. METHODS OF DETERMINING THE WORKING LENGTH
Predetermined “normal” tooth length
Patient response to pain
Tactile sensation of the therapist
Paper point technique
Radiographic method
Electronic locators 5

6. Patient response to pain - apical sensitivity
Many false information, misleadings,
& limitations; extremely subjective =
=> unreliable
- remnants of vital pulp tissue
- pressure of the instrument tip via debris
- destruction of PA tissues – no sensation
- individual sensitivity – pain threshold
- local anaesthesia
- poor / no evidence in literature
Is it still in use, or gone to dental history ?

7. Tactile sensation of the operator
Very subjective, with limitations, often misleading
=> unreliable
- morphological irregularities: narrowing,
calcification,
multiple constrictions
- tooth type & age
- pathological resorption & wide AF
- a few evidence in literature
Still advocated as very useful in hands of an
experienced practitioner to feel and identify AC !?

8. Tactile sensation “Belgrade clinical study”
M.V. & M.P. : 1984
Literature data:
to locate apical constriction
accuracy varies: 30% - 44% - 60%
with wide and random distribution
of measured values
Referent point from Rö apex :
0.5mm in <25 yrs; mm in >25 yrs
Preflaring enhances locating
of the AC, and increases accuracy: 32% up to 75%
Precise in only 19%;
with +/- 0.5 mm tolerance accuracy in 42%.
Significant under and overestimations
up to 4.5 mm before and beyond RP !!!

9. Paper point technique Claimed as the most precise method to determine:
i) working length to the end of the canal, and
ii) min. apic. for.diam. (MAFD) in 3D
Allows practitoner to “see” the
cavosurface of the canal
with the precison of 0.25 mm;
- apical patency technique -
Wet (blood) / dry interface coincides with the location of the CS
Enables to customise gutta-percha master cone 3D
upon the information from the PP

10. Paper point technique
DB Rosenberg
By courtesy of J. Webber

11. Paper point technique
Even claimed as the most precise method in determining WL there is neither scientific nor clinical evidence in literature on its superiority
In spite of being advocated by many endodontic experts,
PP technique lacks in respect to morphological details and
pathological state within the root canal and in periapical tissues
“The use of PP as a simple device in sophisticated ways”- (Rosenberg)
could be advised as an accessory / assisting mean to establish and
confirm final WL, since it is non-aggressive, “soft” method, and
therefore cannot injure tissues or disturb wound healing

12. PREOPERATIVE – DIAGNOSTIC RADIOGRAPH IS MANDATORY !
Radiographic method
REVEALS, ASSISTS, BUT OFTEN GIVES AN “ILLUSORY TRUTH”
PREOPERATIVE – DIAGNOSTIC RADIOGRAPH IS MANDATORY !

13. . Radiographic apex and anatomical apex do not (always) coincide !
Apical foramen cannot be (always)
visualised on a radiograph !
Important details are not always
detectable on the clinical radiograph

14. Radiographic method “Belgrade clinical study” Literature data:
M.V. & M.P.:1988
Referent point from Rö apex :
0.5mm in <25 yrs; mm in >25 yrs
Literature data:
Accuracy widely ranges
from 50% - 77% - up to 97%
Precise in 51%;
tolerance +/- 0.5 mm -> accurate in 68%;
tolerance extended +/-1 mm accurate in 88%;
Under and overestimations not over 2 mm !

15. Measuring file is longer than it appears radiographically !
When instrument is short of the Rö apex
surprisingly is beyond AF in 43% !
I.B.
If AC is 0.5 mm before apex then 66% of all measurements are “beyond” !

16. but could be solved successfully
NO DOUBT – BEYOND
but could be solved successfully 22

17. When short of the Rö apex it is actually closer to the AF !
“... radiographic working length ending mm short of the radiographic apex provides, more often than expected,
a basis for unintentional overinstrumentation”

18. But could be solved successfully
NO DOUBT – SHORT
But could be solved successfully 12
Radiographs are indispensable for calculating,
but not for determining WL !

19. Radiovisiography - RVG
Digital radiography
K..B-I. 37
Assisted by RVG, only !
S. Andjelkovic
Radiovisiography - RVG

20. Digital radiography - RVG
Quantifies distances
Image could be varied by software programme
Fine file tip – low contrast structures –
affect visualisation and measuring precision
Better results with #15 or #20 files
Image quality bellow conventional Rö
Inferior to ELs – longer measurements
S. Andjelkovic 20

21. Adequate radiographs, knowledge of anatomy,
Radiographic method relies still on many
assumptions, arbitrary calculations, averages,
speculations and “illusory images”,
that add to the confusion rather than giving solution !
“GIVE LOCATORS A CHANCE”
Adequate radiographs, knowledge of anatomy,
and tactile sense, and not “apex locators” -
- will help to determine apical constriction ! 21

22. ELECTRONIC FORAMEN LOCATORS
ELECTRONIC APEX LOCATORS
ELECTRONIC FORAMEN LOCATORS
ERCLMD, ”lot of words descriptive” – no length
CLASSIFICATION of EFLs
Resistance-based devices I
Low frequency oscillation devices II
High frequency (capacitance-based) devices II
Capacitance & reistance device (access. look-up table) IV
Voltage gradient-based devices ??
Two frequences (impedance diference)-based devices III
Two frequences (impedance ratio-quotient) devices III
Multi frequency-based devices III
“The use of “generation X” to describe and clasify these devices is unhelpful, unscientific and perhaps best suited to marketing issues”
These are the very same devices, but just under different brand-name,
showing how market functions and manufacturers „cooperate“

23. In vitro (ex vivo) measuring the accuracy of EFLs
- variables influencing and affecting results -
Embedding media - simulate clinical conditions (peridontal ligament)
Electrical properties of intracanal solution:
extreme conductivity and ion concentration (type of EFL)
File size in respect to the diameter of the AC and AF:
wise to use smooth canal instruments - less damage to fine structures
Type of EFL: the newer model the better and more consistent results

24. Variables influencing and affecting results
of ex vivo measuring the accuracy of EFLs:
Preflaring: improves determination of apical diameter and
first file that binds, stabilises readings, increases precision
Range of tolerance: from +/- 0.1 mm, mostly +/- 0.5 mm, up to 2 mm;
the wider the range the higher the percent of EFL accuracy !
- Apical land mark chosen to determine “real/actual length” (RA / AL)
Most are valuable / useful for practice; majority was conducted
in single rooted / canal teeth and suffer of too many variables !

25. Differences bellow 0.5 mm are clinically not significant
Are differences between real values and on EFL’s significant ?
Figures/marks on a display of EFL’s scales do not represent values in mm !
303
300
Differences bellow 0.5 mm are clinically not significant
due to our manual abilities !

26. In clinical use to wait for 3-5 seconds to achieve stable reading !
What about occasionally unstable readings
- bouncing indicating marks ?
In clinical use to wait for 3-5 seconds to achieve stable reading !

27. Tolerate small differences which are not noticeable clinically ?
Bellow 0.5 mm !
Differences clinically acceptable !!

28. How strong readings on a display correspond to the real values on a high-tech measuring instrument ?
0.012– mm
0.022– mm
Far away of any concern!
Precision and high resolution !
Extremely small distorsions from the real measures!

29. Indicate high level of resolution !
How exact readings on a display correspond to the real values
on the high-tech measuring instrument ? What do they indicate ?
What is the clinical relevance ?
=0.20mm
=0.16mm
< 0.06 mm
0.001 mm
Indicate high level of resolution !
Differences far bellow clinically tolerable +/- 0.5 mm !!
The closer to the apex, the more precise the readings are & higher is the resolution!!

30. Can we follow with confidence what display indicates
upon manufacturer’s instructions ?
EFLs scales do not represent values in mm !
Four yellow segments indicate region between AF and AC (0.5 – 1.0 mm) !

31. Follow what display indicates and manufacturers instructions,
but ”filtrate” and reconsider unusual and “strange” readings !!
Three green segments indicate region of the apical constricion (~1.0 mm)

32. Do different foramen locators display the same values
for the same distance in the same root canal ?
Until spreader reached plastic barrier
Tip of the finger spreader to the flat
plastic surface placed firmly at the
plane of the anatomical foramen !

34. Do different foramen locators display the same values for the same distance in the same root canal ?
No, they do not !

35. 351 (340) 307 (350) 193 (300) 169 (202) Raypex 5 Propex I Apex NRG XFR
Distance between warning “beyond foramen” => reading foramen
=> ”switch” to one mark/segment “short of foramen”
Electronic foramen locator
from – to
range in m
resolution / “subtlety”
Raypex 5
Propex I
Apex NRG XFR
Dentaport ZX
Apex Pointer +
(m)
193 (300)
351 (340)
0.0
0.1
– 380
(48)
Apex
307 (350)
Apex
(202)
AP EX

36. Different foramen locators show different values
with different level of resolution for the same distance
in the same root canal !
All deviations are far bellow range of clinically
acceptable tolerance of +/- 0.5 mm, therefore they
do not significantly influence the accuracy of EFLs
in locating apical foramen !!

37. In vivo studies - on teeeth to be extracted:
more realistic / relevant / reliable information useful for practitioners
Factors that affect readings and/or accuracy of EFLs:
- Vital – necrotic cases
- Preflaring
- Diameter of the minor and major foramen (pathol. – instrum.)
- Size of the measuring file
- Type of material the measuring file is made of
- Canal content: infl. pulp tissue, puss, detritus; empty/dry
- Conductive properties and ions concentration of irrigating solution
- Tooth type: front - posterior / single – multi canal

38. No affect on readings and accuracy:
More consistent, straight forward, faster and precise readings when:
- coronal /middle/ portion preflared
- pulp tissue extirpated – debris removed
- foramen is not enlarged by periapical pathosis / instrumentation
- size of the file coincides with lumen of the apical portion
- moderately conductive irrigating solution: 2% NaOCl, CHX, EDTA
No affect on readings and accuracy:
- Tooth type: front - posterior / single – multi rooted (canal)
- Type of material the measuring file is made of

39. Contradictory & controversial results / statements on:
- vital vs. necrotic
- moist vs. dry: type of EFL
- high conductive vs. low conductive irrigant: type of EFL
Adverse effect on readings:
- PA lesions associated with destruction of PL, AF, AC and bone
- wide open AF in immature teeth
- extremes in conductive properties of a solution in the canal:
saline vs. destilled water

40. Variables influencing clinical results of EFLs accuracy :
(varies from 15% up to 100%)
- method to establish precision of the locator:
micrsocsopy measurement - software programmes for extracted
teeth samples vs. comparison with clinical radiograph
- range of tolerance/targeted interval:
+/- 0.5; +/- 1.0; +/- 1.5 mm; higher tolerance -> higher % of accuracy
mark on a display chosen to be “apical terminus” for EWL:
“00” / “Apex” vs. “-0.5”/”AC; -1.0; yellow or green segment –
or each operator will chose the mark that he wants to call his
OWN APICAL TERMINUS
- anatomical land mark chosen to measure distance from the file tip:
AC & CDJ vs. AF & AnAp
Manufacturers should define clearly which lendmark their product locates !

41. “Belgrade clinical studies on EFLs”
M P, M V & V I : in early 80’s of the last century
Domestic hand-made device “Diapex”
“Odontometer” – Goof, DK

42. “Belgrade clinical studies on EFLs”
M.V. & D. I.: 1996
M.P & M.V. :
Referent point from Rö apex :
0.5mm in <25 yrs; mm in >25 yrs
“Odontometer”
Alternating current impedance
measuring device- in dry canal
Precise in 67% of vital teeth,
and in 76% of teeth with necrotic pulp,
with +/- 0.5 mm range of tolerance.
Mostly underestimations of mm !
Precise in 77% with +/- 0.5 mm tolerance.
Overestimations of mm in only 4% !

43. Accuracy of EFLs checked in clinical situation by Rö ?
Traditionally EFLs accuracy has been corroborated by Rö, but any correction of the file position according to Rö projections would invariably lead to overextension !
Comparison of precision of EFLs with Rö is not accurate because Rö is unreliable method in determining AC & AF !

44. “Belgrade in vivo studies”
In vivo - in molars and multirooted premolars to be extracted:
30 canals per locator !
“Propex I”: Dentsply/MAILLEFER (D. Nobs & S. Fultinavicius)
“Raypex 5”: VDW (L. Satanovskij)
“Apex NRG XFR”: Medic NRG (M. Zach, A. Beker, E. Friedman)
“ApexPointer+”: MicroMega (C. Dort & A. Stephany)
“Dentaport ZX”: J. Morita (J. Bohnes)

45. tangential line to the AF
Referent point was
tangential line to the AF
Mark on a display
indicated AF:
“0.0”, “Apex”, “red segment”

46. NRG XFR small SD - consistent measuring; no beyond AF
Mean distance from the file tip to the AF - in vivo determined
Electronic foramen locator
Mean (+/- SD)
Beyond AF
Apex NRG XFR
Dentaport ZX
Propex I
Raypex 5
Apex Pointer + Ø
(0.079)
(0.222) 2;
(0.149)
9; (0.102)
(0.142) 3; 1;
(0.168)
Majority showed high SD – dispersion of values
All EFLs 100% precise within 0.2 mm range of tolerance;
Seldom overestimations with small values - clinically acceptable
NRG XFR small SD - consistent measuring; no beyond AF

47. “When apical foramen is located the position
of the apical constriction (if exists)
can be estimated”

48. Always have preoperative radiograph
and stay within confines of the root canal !
K..B-I.
Determining WL upon preop Rö and EFL, only !

49. TRUST in EFLs , BUT NOT BLINDLY !! Extreme narrow canals: Rö and EFL
WL upon preop RVG, and EFL, only !!
K..B-I.
TRUST in EFLs ,
BUT NOT BLINDLY !!

50. Crown-down tapered preparation; WL - 0.25 mm before AF:
tactile sensation, EFL, Rö and PP;
rotary NiTi instrumentation & cold lateral
COMBINING AND
COMPARING SEVERAL METHODS
GIVE MORE CONFIDENCE,
ACCURACY AND SUCCESS THAN
USING ONLY ONE OR EVEN NONE !

51. 36 46 PREDICTABLE, RELIABLE AND SUCCESSFUL ENDODONTICS
Let’s produce perls of endodontic treatment giving always our best 36 46
twin-like

52. MANY THANKS FOR YOUR ATTENTION
Regards from Belgrade !!!
MANY THANKS FOR YOUR ATTENTION
1997 th