This document discusses methods for determining working length in endodontic treatment. It defines working length and important anatomical landmarks at the root apex, including the apical constriction, apical foramen, and cementodentinal junction. The key methods described for determining working length are radiographic examination, use of electronic apex locators, tactile sensation with files, and assessing moisture on paper points. The document emphasizes that accurately determining working length is critical for successful cleaning, shaping and obturation of the root canal system.

1. Working Length Determination
and Root Apex Anatomy
By
Dr.Mahavosh Qazi
BDS

2. Introduction
• Determination of an accurate working length is
one of the most critical steps of endodontic
treatment.
• Cleaning, shaping and obturation cannot be
accomplished accurately unless working length
is determined correctly.

3. Definition
• It is defined as:
“The distance from a coronal
reference point to a point at which canal
preparation and obturation should terminate”

4. Reference Point
• A reference point is
that site on the insical
or occlusal surface
from which
measurements are
made.
• A reference point is
chosen which is stable
and visualized during
preparation.

5. Anatomy of the Root Apex
Three anatomic & histologic landmarks at the root
apex
• Apical Constriction
• Apical Foramen
• Cementodentinal Junction

6. APICAL CONSTRICTION
• Also termed as Minor Diameter of the canal
• It is the part of the root canal which is smallest
• Reference point clinicians use to terminate
cleaning/shaping & obturation
• AC is generally 0.5-1 mm inside the AF
• Postoperative discomfort is greater when this area is
violated

7. Dummers classification

8. Cementodentinal Junction
• CDJ is the point where cementum meets dentine
• It is the point where pulp tissue ends &
periodontium begins
• Approximately 1mm from AF

9. APICAL FORAMEN
• Also termed as Major Diameter of the canal
• Not always located at anatomical apex of tooth
• Space between AC & AF is funnel shaped or
hyperbolic
• Mean distance between AC & AF is 0.5 mm in
young & 0.67 mm in older individuals due to
cementum deposition

10. CLINICAL CONSIDERATIONS
• Location of AC & AF is difficult clinically
• Radiographic apex is a more reliable reference
point
• Clinical & biological evidence indicates in vital
cases a favorable point to terminate therapy is 2-
3 mm short from radiographic apex (RA)
• This leaves an apical pulp stump which prevents
extrusion of debris & filling materials into
periradicular tissues

11. Cont...
• In cases of necrotic pulp & apical periodontitis
bacteria & by products are present in apical root
• In these cases terminate therapy 0.5-1 mm from
RA

12. Apical Configuration
APICAL STOP
Complete barrier at the apex
Dentine chips are packed
APICAL SEAT
Incomplete barrier at the apex
OPEN APEX
No barrier

13. Wide vs Narrow Apical Preparation
PREPARATION BENEFITS DRAWBACKS
NARROW APEX Minimal risk of
transportation, extrusion
of irrigants & filling
materials
Little removal of infected
dentine & questionable
rinsing effect during
irrigation
Can be combined with
tapered preparation to
counteract drawbacks
Possibly compromised
disinfection
Not suitable for lateral
compaction
Wide Apex Removal of infected
dentine
Risk of preparation errors
Access of irrigants &
medications to apical
third
Risk of extrusion of
debris & filling materials
Not ideal for
thermoplastic obturation

14. Armamentarium for WL determination
• 10 K file
• 15 and 20 K file
• Radiographs
• Apex locators
• Paper points

15. WL determination methods
• Radiographic Method
• Electronic Apex Locator
• Use of anatomical averages and knowledge of
anatomy
• Tactile sensation
• Moisture on a paper point

16. Radiographic Method
• Using pre op radiographs to gauge root morphology,
number and curvature of roots, acts as initial guide.

17. Apex Locator

18. Apex Locator
Advantages Disadvantages
• Reduces number of radiographs
which need to be taken so
minimizes time
• Also useful in cases where apical
foramen is at a distance from
RA
• Helpful for detecting
perforations
• Researches say it is useful in
detecting fractures and
resorptions as well
• Some have added vitality testing
functions
• Intact vital tissue,
inflammatory exudate and
blood can cause inaccurate
readings
• Metallic restorations, saliva or
caries can cause short
circuiting
• Dentine debris and
calcifications can also affect
• Records not able to be
maintained
• Not recommended for patients
with cardiac pacemakers

19. Tactile Sensation
• If the coronal portion of the canal is not
constricted, clinician may detect an increase in
resistance as the file approaches the apical 2-3
mm. This detection is by tactile sense.
• In this region the canal frequently constricts
before exiting the roots. There is also tendency
for canal to deviate from radiographic apex.

20. Paper Point Moisture
• In an immature (wide open) apex,
the most reliable means of
determining working length is to
gently pass 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 maybe an
estimation of working length or
the junction between the root apex
and the bone.