Working length determination in endodontics

1. WORKING LENGTH
DETERMINATION
Dr.Genene Getachew(General
dentist)
@Jimma university
5/18/2024
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2. Introduction
Definition of terms and anatomical
considerations
Importance of Working Length
Methods of Working Length
Determination
Radiographic methods
Nonradiographic methods
References 5/18/2024
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Outline

3. Determination of accurate working length and its maintenance
during cleaning and shaping procedures are key factors for
successful endodontic treatment.
The cleaning, shaping, and obturation cannot be accomplished
accurately unless the working length is determined correctly.
The procedure for establishment of working length should be
performed with skill, using techniques which have shown to
give valuable and accurate results and are practical and
successful.
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Introduction

4. Working length: is defined as the distance from a
coronal reference point to the point at which
canal preparation and obturation should
terminate.
Reference point: is the site on occlusal or the incisal
surface from which measurements are made.
 it should be stable and easily visualized during preparation
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Definition of terms and anatomical
considerations

5.  Usually, it is the highest point on the incisal edge of anterior teeth
and buccal cusp of posterior teeth
 It should not change between the appointments
 To have stable reference point, undermined cusps and restorations
should be reduced before access preparation
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Cont’d

6.  Anatomic apex: is tip or end of root determined
morphologically.
 Radiographic apex: is tip or end of root determined
radiographically.
Apical foramen: is the main apical opening of the root canal
which may be located away from anatomic or radiographic apex.
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Cont’d

7. Cementodentinal junction (CDJ): is the region
where the cementum and dentin are united, the point at
which cemental surface terminates at or near the apex
of tooth.
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Cont’d
Apical constriction
(minor apical diameter):
is the apical portion of root
canal having narrowest
diameter.
It is usually 0.5–1 mm
short of apical foramen.

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Cont’d

9. determines how far into canal instruments can be placed and
worked
plays an important role in determining the success of the
treatment
It affects the degree of pain and discomfort the patient will
experience during or after the treatment.
If proper care is not taken, over or underinstrumentation can
occur
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Importance of Working
Length

10. means extension of instruments into periapical tissue
1. Pain as a result of response from mechanical damage to the
periapical tissue
2. In infected teeth, extrusion of microbes and infected debris
3. Overfilling, causes mechanical and chemical irritation of the
periapical tissue
4. Prolonged healing time and lower success rate due to incomplete
regeneration of cementum, periodontal ligament, and alveolar bone
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Consequences of
overinstrumentation

11. Incomplete cleaning and instrumentation of the canal
1. Persistent discomfort due to presence of pulpal remnants
2. Under filling of the root canal
3. Incomplete apical seal
4. Apical leakage which leads to poor healing and periradicular
lesion.
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Consequences of under-
instrumentation

12. Presence of debris in apical of canal
Failure to maintain apical patency
Skipping instrument sizes
Ledge formation
Inadequate irrigation
Instrument separation
Canal blockage
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Causes of loss of working
length

13. RADIOGRAPHIC METHODS
•Ingle’s technique
•Best’s method
•Bregman’s method
•Bramante’s technique
•Grossman’s method
•Weine’s method
•Kuttler’s method
•X-ray grid method
•Xeroradiography
NON-RADIOGRAPHIC
METHODS
•Electronic apex locators
•Tactile sense
•Apical periodontal
sensitivity
•paper point method
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METHODS OF DETERMINING
WORKING LENGTH

14. When radiographs are used in determining working length, the
quality of the image is important for accurate interpretations.
Advantages
 Anatomy of the tooth and curvature of root canal can be seen on
radiograph
 Radiograph helps in analyzing the relationship with adjacent teeth
and anatomic structures.
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RADIOGRAPHIC TECHNIQUES FOR
MEASURING WORKING LENGTH

15. Disadvantages
 Varies with different observers
 Superimposition of anatomical structures
 2D view of 3D object
 Cannot interpret if apical foramen has buccal or lingual exit
 Risk of radiation exposure
 Time consuming
 Limited accuracy
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Cont…

16. Clinical Prerequisites
Knowledge of average length of
teeth.
Instrument precurving
Stable occlusal reference point
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Ingle’s radiographic technique of
working length determination

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Cont…

18. Take the preoperative radiograph
Measure the estimated working length from preoperative
radiograph
 The estimated working length is kept as 1 mm short of the
length of the tooth measured on the radiograph.
This is done to compensate for the radiographic image
distortion and for the fact that the minor diameter is always
present short of the anatomical apex.
Adjust stopper of instrument to this estimated working
length
place it in the canal up to the adjusted stopper
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Clinical technique

19. Take the radiograph
On the radiograph, measure the difference between the tip of
the instrument and root apex.
a. If the tip of the instrument ends 0.5 mm–1.0 mm from the
radiographic root apex (working length established)
b. If short of the radiographic apex by more than 1.0 mm add this
value to the earlier estimated length and adjust stopper on the
diagnostic instrument accordingly retake the working length
radiograph
c. If beyond the radiographic apex Reduce this value from the
earlier estimated length and adjust stopper on the diagnostic
instrument accordingly Retake the working length radiograph
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Cont…

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Cont…

21. Weine modified calculation of working length
according to presence or abscence of resorption
 No resorption - subtract 1 mm
 Periapical bone resorption - subtract 1.5 mm
 Periapical bone + root apex resorption - subtract 2 mm
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Weine’s Modification

22. Technique
1. Locate minor and major diameter on preoperative radiograph
2. Estimate length of roots from preoperative radiograph
3. Estimate canal width on radiograph.
 If the canal is narrow, use 10 or 15 size instrument.
 If it is of average width, use 20 or 25 size instruments.
 If the canal is wide, use 30 or 35 size instrument
4. Insert the selected file in the canal up to the estimated canal
length and take a radiograph
5. If the file is too long or short by >1 mm from minor diameter,
readjust the file and take second radiograph
6. If the file reaches major diameter, subtract 0.5 mm from it for
younger patients and 0.67 for older patients 5/18/2024
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Kuttler’s Method

23. It is based on simple mathematical formulations to calculate
the working length.
In this, an instrument is inserted into the canal, stopper is
fixed to the reference point and radiograph is taken.
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Grossman method of working length
determination

24. It was designed by Everett and Fixott in 1963.
It is a simple method in which a millimeter grid is
superimposed on the radiograph
This overcomes the need for calculation, But it is not a good
method if the radiograph is bent during exposure
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Radiographic Grid

25. In this method, one uses the graduations on diagnostic file
which are visible on radiograph
But its main disadvantage is that the smallest file size to be
used is number 25
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Endometric Probe

26. Electronic apex locators
Currently, an electronic apex locator (EAL) is the most optimal
and accurate method to establish the root canal working
length.
The working length is determined by comparing the electrical
impedance of the periodontal membrane with that of the oral
mucosa both of which should be similar at 6.5 kΩ.
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Non-radiographic Methods of
Working Length Determination

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Components of EALs

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Cont’d

29.  high degree of accuracy
For patients with problem of gag reflex.
Useful in pregnant patients
Useful in children
Valuable tool for detecting root perforations , external and
internal resorption, horizontal and vertical root fracture
Testing pulp vitality
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Advantages of apex locators

30. The accuracy of EAL may be altered in teeth with the following:
Immature apices (open apex)
Calcified or blocked canals
Excessive hemorrhage/excessive inflammatory exudate in the
canal
 Measurements get altered when the file contacts any metallic
restoration
Teeth with periapical radiolucencies
necrotic pulp associated with root resorption, because of lack of
viable periodontal ligament
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Limitations of apex locators

31. 5/18/2024
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Classification of Electronic
Apex Locators

32. 1. First-generation apex locator
(resistance apex locator)
known as resistance apex locator which measures opposition to
flow of direct current, that is, resistance.
It is based on the principle that resistance offered by
periodontal ligament, and oral mucous membrane is the same,
at 6.5 kΩ.
Examples , root canal meter, endometric meter Dentometer,
Endo Radar.
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Classification According to
Generations of EALs

33. Inoue introduced the concept of impedance-based apex locator
which measure opposition to flow of alternating current or
impedance
This apex locator indicates the apex when two impedance
values approach each other.
 Sonoexplorer, Apex finder , Exact-A-Pex,
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2. Second-generation apex locator
(impedance-based apex locator)/low-
frequency apex locator

34. It is based on the fact that different sites in canal give
difference in impedance between high (8 kHz) and low (400 Hz)
frequencies
Endex , Mark V plus, Root ZX , Root ZX II , Root ZX mini
4. Fourth-generation apex locator
measures resistance and capacitance separately rather than the
resultant impedance value
 AFA apex finder, i-Pex, Rayapex 4, Propex,
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3. Third-generation apex
locator/high-frequency apex locator

35. based on comparison of data taken from the
electrical characteristic of the canal and additional
mathematical processing.
These show accurate reading in presence of dry, wet,
saline, EDTA, blood, or sodium hypochlorite.
Examples: Rayapex, Propex II, Propex Pixi, I -ROOT,
Joypex 5
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5. Fifth-generation EALs (dual-
frequency ratio type)

36. This apex locator is intended to overcome the
disadvantages of fourth- and fifth-generation EALs.
 It eliminates the need of drying the canals.
Examples: Adaptive apex locator, Raypex 6
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6. Sixth-generation EALs
(adaptive apex locators)

37. In this, clinician may see an increase in resistance as file reaches
the apical 2–3 mm.
Advantages
 Time saving
 No radiation exposure
Disadvantages
 Does not always provide the accurate readings
 increased resistance in narrow canals as file approaches apical 2–
3 mm
 In immature apex, instrument can go periapically
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Digital tactile sense

38.  based on patient’s response to pain
But this method does not always provide the accurate
readings in the case of narrow canals, canal with necrotic pulp
and in the case of vital or inflamed pulp.
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Apical periodontal sensitivity
test

39. In this method, paper point is gently passed in the root canal
to estimate the working length‰
 It is most reliable in cases of open apex where apical
constriction is lost because of perforation or resorption
Moisture of blood present on the apical part of paper point
indicates that paper point has passed beyond estimated
working length.
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Paper point measurement
method

40. 1. Garg, N., & Garg, A. (2019). Textbook of endodontics
(4th ed.). Jaypee Brothers Medical Publishers.
2. Gopikrishna, V., & Grossman, L. I. (2020).
Grossman’s endodontic practice (14th ed.). Wolters
Kluwer Health (India).
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References

41. 5/18/2024
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