The document defines key terms related to endodontics, including working length and working width, and their significance in root canal procedures. It discusses methods of determining working length, the importance of proper canal widening, and various tools like apex locators and digital radiography. Additionally, it outlines factors influencing working length accuracy and associated complications of improper measurements.

1. DEFINITIONS
• WORKING LENGTH:
According to endodontic glossary
working length is defined as “ the
distance from a coronal reference
point to a point at which canal
preparation and obturation
should terminate”

3. • REFERENCE POINT:
is that site on occlusal
or the incisal surface
from which
measurements are
made.

4. • ANATOMIC APEX: tip or
end of root determined
morphologically.

5. • RADIOGRAPHIC APEX: tip or
end of root determined
radiographically.

6. • APICAL FORAMEN (major diameter):
is main apical opening of the root
canal. It is frequently eccentrically
located away from the anatomic or
radiographic apex.
• APICAL CONSTRICTION (minor
diameter):
is apical portion of root canal having
narrowest diameter. It is usually 0.5
to 1 mm short of apical foramen.
• CEMENTODENTINAL JUNCTION:
the region where cementum and
dentin are united, the point at which
cemental surface terminates at or
near the apex of tooth.
• Location of CDJ ranges from 0.5-
3mm short of anatomic apex.

7. SIGNIFICANCE OF WORKING LENGTH
Determines how far into canal, instruments can be
placed and worked.
Consequences Of Over Extended Working Length:
Perforation through apical constriction.
Overinstrumentation
Overfilling of root canal
Increased incidence of postoperative pain.
Prolonged healing period
Lower success rate (because of incomplete
regeneration of cementum, periodontal
ligament and alveolar bone

8. Consequences Of Working Short of
actual working Length
• Incomplete cleaning & instrumentation of
canal.
• Persistent discomfort due to presence of pulpal
remnants
• Under filling of the root canal.
• Incomplete apical seal.
• Apical leakage which supports existence of
viable bacteria and contributes to poor healing
and periradicular lesion

9. Causes of loss of working length:
Presence of debris in apical 2/3rd
of
canal
Failure to maintain apical patency
Skipping instrument sizes
Ledge formation
Inadequate irrigation
Instrument separation
canal blockage

10. WORKING WIDTH
• Definition:
Working width is defined as “initial and postinstrumentation
horizontal dimensions of the root canal system at working length
and other levels”
• the minimum initial working width= initial apical file size
which binds at working length and other levels
• The maximum final working width corresponds to the master
apical file size.

11. • Reasons for widening root canal:
• To remove microorganism from the canal mechanically
• To increase the area of root canal for better irrigation
• To completely remove the pulp tissue
• To gain a sound apical stop so as to achieve a 3 dimensional
seal. The round shape confirms to the round cross sectional
tip of gutta percha

12. • 2 guidelines for instrumentation:
Enlarge the root canal at least 3 sizes beyond
the first instrument that binds the canal
Enlarge the canal until it is clean. It is indicated
by white dentinal shavings on the instrument
flutes
The main aim should be to remove the canal
irregularities of dentin to make the canal walls
smooth

13. Factors affecting size of working width
Whether root canal is vital/non-vital
Presence of periapical pathology
Presence or absence of root resorption
Canal configurations like C-shaped canal,
Presence or absence of isthmus

14. Advantages of narrow apex:
Decrease risk of canal transportation
Avoids extrusion of debris and obturating material
Disadvantages of narrow apex
Incomplete removal of infected dentin
Not ideal for lateral compaction
Irrigants may not reach the apical-third of canal
Advantages of wide apex
Complete removal of infected dentin
Better disinfection of canal at apical third
Disadvantages of wide apex
Increased chances of extrusion of irrigants and
oobturating material
Not recommended for thermoplastic obturation
More chances of preparation errors

15. METHODS OF WORKING LENGTH
DETERMINATION
• Average root length from anatomic studies
• Radiographs
• Bleeding on paper point
• Apical periodontal sensitivity
• Electronic apex locator

16. RADIOGRAPHIC METHOD OF
WORKING LENGTH DETERMINATION
Cementodentinal junction is impossible to locate clinically
and the radiographic apex is the only reproducible site
available for length determination.
Those who don’t follow this concept say that radiogrpahic
apex is not reproducible. Its position depends on number of
factors like angulation of tooth, position of film, film holder
etc.
Two techniques used: Paralelling technique (superior) and
bisecting angle technique

17. Before access opening, fractured cusps, weakened cusps are
reduced to avoid fracture of weakened enamel during the
treatment. This will avoid the loss of initial reference point and
thus the working length.

18. JOHN INGLE’S METHOD
Pre-op radiograph is used to calculate the working
length.
Measure estimated working length from
preoperative periapical radiograph
It can be confirmed by placing an endodontic
instrument (with stopper adjusted) into the canal
and taking a second radiograph.
Instrument inserted should be large enough not
to be loose in the canal because it can move while
taking radiograph and this may result in errors in
determining its working length.

20. Advantages
• Can see the anatomy of the tooth
• Can find out curvature of the root canal.
• Can see the relationship between the adjacent teeth and
anatomic structures.

21. Disadvantages
• Varies with different observers.
• Superimposition of anatomical structures.
• Two- dimensional view of three-dimensional object.
• Cannot interpret if apical foramen has buccal or lingual exit.
• Risk of radiation exposure.
• Time consuming
• Limited accuracy

22. WEINE’S MODIFICATIONS
Weine’s recommendations for determining the working length based
on radiographic evidence of root or bone resorption
If no root or bone resorption: preparation should terminate 1.0
mm short of the apical foramen (shorten the length by 1 mm)
Bone resorption is present but no root resorption: shorten the
working length by 1.5 mm
Both root & bone resorption is present: shorten the length by
2.0mm

23. Direct digital radiography
• Digital image is formed
• 2 types:
• Radiovisiography
• Phosphor imaging system

24. DIGITAL TACTILE SENSE
Clinician may see an increase in resistance as file
reaches the apical 2 to 3mm.
Advantages:
Time saving
No radiation exposure
Disadvantages:
Inaccurate readings
Narrow canals, one may feel increased
resistance as file reaches apical 2 to 3mm.
Teeth with immature apex, instrument can go
periapically.

25. PERIODONTAL SENSITIVITY TEST
Based on patient’s response to pain.
Don’t always provide accurate readings
In case of narrow canals , instruments may feel
increased resistance as file approaches apical 2-3mm
In case of teeth with immature apex, instrument
can go beyond the apex
In apical periodontal sensitivity test,
In case of necrotic pulp: instrument can pass
beyond apical constriction
In case of vital or inflamed pulp: pain may occur
several mm before periapex is crossed by the
instrument

26. PAPER POINT MEASUREMENT METHOD
• Paperpoint is gently passed in the root canal to estimate the
working length.
• Most reliable: open apex cases
• Moisture of blood present on apical part of paper point
indicates that paper point working has passed beyond
estimated working length.
• Used as supplementary method.

27. ELECTRONIC APEX LOCATORS
Used as an adjunct to radiography
Used to locate the apical constriction or
cementodentinal junction or apical foramenand not
the radiographic apex.

28. Apex locators function by using human body to compete an electrical circuit.
One side of apex locator circuit is connected to endodontic instrument and
other side is connected to patient’s body.
Circuit is completed when endodontic instrument is advanced into root canal
until it touches the periodontal tissues

29. COMPONENTS
• Lip clip
• File clip
• Electronic device
• Cord which connects above three parts

30. Advantages
• Provide objective information with high degree of accuracy
• Easy and fast
• Reduction of exposure to radiation
• Perforation can be detected
• Can measure pulp space exactly to the constriction

31. Disadvantages
• Can provide inaccurate readings in following cases.
• Presence of pulp tissue in canal
• Too wet or too dry canal
• Use of narrow file
• Blockage of canal
• Incomplete circuit & low battery
• Immature apex
• Incorrect readings in teeth with periapical
radiolucenies, and necrotic pulp associated with
root resorption, etc.

32. Uses
Provide objective information
with high degree of accuracy
When apical portion of canal
system is obstructed.
In patients who cannot tolerate
X-ray film placement because of
gag reflex
Pregnant patients
Detecting site of root
perforations
Children, disabled patients,

33. Contraindications
• Patients who have cardiac pacemaker

34. CLASSIFICATION
Based on type of current flow and opposition to current flow and
number of frequencies involved
First generation apex locator( resistance apex locator)
Second generation apex locators (impedance apex locators)
Third generation apex locators
Fourth generation apex locators
Combination apex locators and endodontic handpiece

35. THIRD GENERATION (FREQUENCY
DEPENDENT APEX LOCATOR)
• High frequency
• Based on the fact that different sites in canal give
difference in impedance between high (8KHz) and low
(400Hz) frequencies
• Is least in coronal part of canal
• As the probe goes deeper into canal, difference
increases
• Greatest at cementodentinal junction
• These should be termed as ‘comparative impedance”
because they measure relative magnitudes of
impedance which are converted into length
information.

36. COMBINATION APEX LOCATORS &
ENDODONTIC HANDPIECE
• Tri Auto ZX is cordless electric endodontic handpiece with builtin
root ZX apex locator
It has three safety mechanisms:
Autostart stop mechanism: handpiece starts rotation when
instrument enters the canal and stops when it is removed.
Autotorque reverse mechanism: handpiece automatically stops
and reverses rotation when torque threshold (30gm/cm) is
exceeded. Prevents instrument breakage.

37. Autoapical –reverse mechanism
• It stops and reverses rotation when instrument tip reaches a
distance from apical constriction taken for working length
• Prevents apical perforation

38. BASIC CONDITIONS FOR ACCURACY OF EAL
• Canal should be free from most of the
tissue and debris
• Canal should be relatively dry
• No cervical leakage
• If residual fluid is present, it should be of
low conductivity (5.25%NaOCl > 17%EDTA >
saline)
• Proper adaptation of file to canal walls and
periapex
• No blockages or calcifications in canals
• Battery of apex locator and other
connections should be proper

39. THANKYOU