- Determining the accurate working length is critical for successful endodontic treatment. The working length is defined as the distance from a coronal reference point to the point where canal preparation and filling should terminate, usually 1mm short of the anatomical apex. Several radiographic and non-radiographic methods can be used to estimate the working length, with the goal of terminating instrumentation at the apical constriction. Common radiographic techniques include using pre-operative measurements, grids, or mathematical formulas based on relative instrument and tooth lengths on radiographs.

2. • The determination of an accurate working length is
one of the most critical steps of endodontic therapy.
• The cleaning, shaping and obturation of the root canal
system cannot be accomplished accurately unless the
working length is determined precisely.
• Definition: Working length is defined as the distance
from a coronal reference point to the point at which
canal preparation and obturation should terminate.
(American association of Endodontics 1998)

3. Significance of working length
• The working length determines till where the
instruments are placed in canal for the removal of
debris, metabolites, end products and other
unwanted items from the canal
.
• It will limit the depth to which the canal filling is
placed.

4. • If calculated properly, it will play an important role
in success of the treatment and if calculated
incorrectly may result in treatment failure.
• Affects the degree of pain and discomfort that the
patient will feel following the appointment.

5. Anatomical Considerations and
Terminologies
Anatomic Apex: It is defined as the tip or the end of the
root determined morphologically.
Radiographic Apex: It is defined as the tip or the end of
the root determined radiographically.

6. Cementodentinal Junction: It is the region where the
dentin and cementum are united. It is a histologic land
mark.
•Apical Foramen (Major Diameter):It is the main apical opening of
the root canal. It is frequently eccentrically located away from the
anatomic or radiographic apex.
•Apical constriction(Minor Diameter): It is the apical portion of
the root canal having the narrowest diameter.

8. Methods of Determining Working Length
1. Radiographic methods
-Ingle’s technique
-Best’s method
-Bregman’s method
-Bramante’s technique
-Grossman’s method
-Weine’s method
-Kuttler’s method

9. -X-ray grid method
-Xeroradiography
-Direct digital radioraphy
2.Non radiographic methods
-Tactile sense
-Apical periodontal sensitivity
-Paper point method
3.Electronic apex locators

10. CORONAL REFERENCE POINT
Before deciding the coronal reference point
-remove all the caries
-remove unsupported cusps
-remove restorations
-establish straight line access
-complete if any occlusal reduction
is required for pt. comfort
To ensure that the reference point to be used will remain unchanged

11.  Repeatable and recorded for future reference.
 The reference point can be the cusp tip of the canal
being measured or the same cusp tip for all the canal.
 If the file is deflected away from a particular cusp tip, the cavosurface
margin of that particular cusp may also be used.
 If no particular definable point can be located, a ledge can be made in
the tooth structure that can act as a reference point.
 Intra-coronal reference point should not be used so as to prevent the
movement of stopper during measurement.

12. The most common method for marking the instruments is with “silicon
stops”.
The special tear-shaped or marked rubber stops.
It is critical that stop attachments be perpendicular and not oblique to
the shaft of the instrument.
Instruments have been developed with millimeter marking rings etched
or grooved into the shaft of the instrument- 18, 19, 20, 22 and 24 mm.

13. -From a biological perspective the apical constriction is
the most rationale point at which to end the canal
preparation.
- Apical constriction is the narrowest point of the canal
and therefore the narrowest diameter of blood
supply.
-Thus cleaning and shaping to the apical constriction
most completely eliminates pathogenic canal contents
& allows inflammatory healing mechanism to
complete.

14.  -From procedural perspective, it is advantage to
treat till the constriction because it is a
morphologic landmark that can be felt by the
experienced clinician.
 -It is not advisable to treat the canals short to this
end point because lateral and accessory canals are
more common near the apex 1-2mm short of the
apical constriction and can leave nearly 2-4mm of
untreated canal-such a length could significantly
increase the chance of persistent periapical
pathosis.

15. Ingle’s method
Clinical prerequisites are
-Good, undistorted, preoperative radiographs showing
the total length and all roots of the involved tooth.
-Adequate coronal access to all the canals
-An endodontic millimeter ruler.
-Knowledge of average length of the tooth and root
anatomy.
-Stable coronal reference point
Anterior teeth→Incisal edges
Posterior teeth→Cusp tips

16. Method
 -Measure the tooth on the preoperative radiograph
 Subtract atleast 1.0 mm “safety allowance”for possible
image distortion or magnification
 -Set the endodontic ruler at this tentative working length
and adjust the stop on the instrument at that level.
 -Place the instrument in the canal until the stop is at the
plane of reference.
 -Expose, develop and clear the radiograph.

17.  -On the radiograph, measure the difference
between the end of the instrument and the end of
the root and add this amount to the original
measured length of the instrument extended into
the tooth. If the instrument has gone beyond the
apex, subtract this difference.
 -From this adjusted length of the tooth, subtract a
1.0mm “safety factor” to confirm the apical
termination of the root canal at the apical
constriction.

18.  -Set the endodontic ruler at this new corrected
length and readjust the stop on the instrument at
this level and take a confirmatory radiograph.
 -Record this final working length and the coronal
point of reference on the patient’s record.

20. -It is important to emphasize that the final working
length may shorten by as much as 1mm as a curved
canal is straightened out by instrumentation.
-It is therefore recommended that the “length of the
tooth” in a curved canal be reconfirmed after
instrumentation is completed.

23. Grossman’s method
• According to Grossman, an instrument extending
to the apical constriction is placed in the root
canal is determined by digital tactile sense and a
radiograph is taken.
• A stopper is placed at the occlusal or incisal
reference point which will also be detectable on
the radiograph.

24. • By measuring the length of radiographic images of
both the tooth and measuring instrument as well
as the actual length of the instrument the clinician
can determine the actual length of the tooth by a
mathematical formula.

25. Actual length Radiographic Actual length
of tooth = length of tooth X of instrument
Radiographic length
of instrument in tooth

26. Best’s method
• In 1960, Best described a technique for determining the
tooth length.
• In this method, a steel pin measuring 10mm is fixed to the
labial surface of the tooth with utility wax.
• Keeping the pin parallel to the long axis of the tooth, and a
radiograph obtained.
• The radiograph is then carried to a guage that would
indicate the tooth length.

27. Bregman’s method
- It is a method in which 25mm length flat probes are
prepared and each has a steel blade fixed with acrylic resin
as a stop
- Leaving a free end of 10 mm for placement into the root
canal.
- This probe is placed into the tooth until the metallic end
touches the incisal edge or cusp tip of the tooth. Then a
radiograph is taken.
- In the radiographic image the following is measured.

28. ALT-Apparent length of the tooth(as seen in the
radiograph)
RLI-Real length of the instrument
ALI-apparent length of the instrument
Now real length of the tooth(RLT)is calculated from the
formula
RLT=ALI X RLI/ALT

29. Bramante’s Method
• He employed stainless steel probes of various calibers
and lengths
• These were bent at one end at a right angle and this
bend is inserted partially into the acrylic resin in such
a manner that its internal surface is in flush with the
resin surface contacting the tooth surface.
• The probe is introduced into the canal so that the resin
touches the incisal edge or cusp tip.
• Then the tooth is radiographed

30. • The reference points are as follows
 A-Internal angle of intersection of the incisal and
radicular probe segment.
 B-Apical end of the probe
 C-Tooth apex
• The tooth length is calculated in two different ways
1. Measuring the radiographic image the length of the
probe A-B, measuring the radiographic image length
of the tooth from A-C, and then measuring the real
length of the probe .

31. Now the following equation is applied
CRD-Real tooth length
CRS-Real probe length
CAD-Tooth length in radiograph
CAS-Instrument length in radiograph
CRD=CRS X CAD/CAS
2.Measuring the distance between the apical end of the
probe and tooth apex in radiograph
This measure is either added or diminished to obtain the
correct length of the tooth.

32. X-RAY GRID SYSTEM
Everett & Fixott in 1963 designed a diagnostic X-ray grid system for
determining the length of the tooth.
The diagnostic X-ray grid designed consists of lines 1mm apart
running lengthwise and cross-wise. Every fifth Millimeter is
accentuated by a heavier line to make the reading easier on the
radiograph.
Enameled copper wires are placed in a plexi –glass
are fixed to a regular periapical film.
The grid is taped to film to lie between the tooth and film
during exposure so that the pattern becomes incorporated
in the finished film. The incorporated grid is used for
Accurate measurement of working length.

33. Kuttler’s method
The basis for this method's value are the
measurements provided by Kuttler relating to the
distance between the major diameter.
In younger patients- 0.5mm
In older patients- 0.67mm.
Using the radiograph the dentist must locate the major
diameter and then interpolate the position of the
minor diameter or locate the minor diameter by
seeing the funneled shape into the tooth from the
site of exiting
(These sites can be seen if they exit in the mesial or
distal direction on the straight film).

34. Step by Step tech for calculation of W.L. by
Kuttlers method :
Using the information from the straight and angled radiograph.
Locate the major diameter and minor diameter on the pre-op x ray.
Estimate the length of the root (s) either by measuring the length with
a mm- ruler on the pre-op radiograph.
Estimate the width of the canal (s) on the radiograph.
Narrow-size 10 or 15 file Average select – size 20 or 25 file
Wide-size 30 or 35 Very wide choose size 50 or
larger.

35.  Using the file selected set the stop for the W.L.
according to the measurement estimated, place
the file in the access cavity and take an initial
radiograph.
if the file seems to stop at a length that could be
accurate stop and take a radiograph rather than
force the file into the periapical tissues.

36. If the file appears too long or too short by more than 1mm from
the minor diameter make the interpolation and use that as the
calculated working length.
If your file reaches the major diameter exactly, subtract 0.5mm
from the length if the patient is 35 years old or younger, reduce
0.67mm from that length if the patient is older.
If the file reaches the site that you believe is the minor diameter
use that as the calculated W.L.
If it is obvious that a great deal of cementum has been
deposited at the root tip, subtract a greater amount from the site
of the major diameter to rectify the increased distance.

37. Kuttler’s phenomenon
The first extensive investigation of root apex anatomy was performed by
Kuttler in 1955.He evaluated 268 teeth from which 402 root ends were
split through the apical foramen and examined.
-deviation of the centre of the foramen further from the apical vertex with
age and subsequent cementum deposition.
-the minor diameter was usually found in dentin.
-the average distance from the minor diameter to the foramen is roughly
0.6mm.
-only 40% to 47% of apices had CDJs at the same level on the sections.
Kuttler concluded that the root canal should
be filled as far as 0.5mm from the foramen

38. Advantages of Kuttlers Techniques
It allows the rapid development of a solid dentin matrix.
If slight error in W.L. calculation occurs i.e.. less than 1mm in either
direction (too long/ too short) the variance rarely causes
serious problems.
For instance a slightly long calculation may cause a filling to
the radiographic apex or a slightly short calculation may end up
1mm from the apex.
Disadvantage of Kuttler’s technique
This calculation method is one of the most complicated methods,
takes the most time and requires radiographs of excellent
qualities and magnification.
Errors do occur with this method as well but these errors are usually
quite minimal.

39. Xeroradiography
• In endodontics, xeroradiography permits a better
visualization of the pulp chamber morphology, root
canal configuration and root canal outline.
• They record images produced by an X-ray but differ
from conventional radiography is that it does not
require a wet chemical processing or dark rooms.
• Xeroradiographs are superior to conventional
radiographs in that.

40. • This is especially evident in maxillary molars and
premolars in which zygomatic arch and maxillary
sinus superimpositions will hinder accurate
visualization of periapical area.
• The lamina dura is also clearly observed.
• Xeroradiographic images are sharper and features such
as edge enhancement, improves the visualization of
files and various anatomical structures such as apical
foramen and periodontal ligament space.

41. Radiovisiography(RVG)
• It produces diagnostically useful images at low
radiation.
• It provides an instantaneous image on a monitor, while
reducing exposure by 80%.
 It has 3 components
1.Radio: Has sensitive intraoral sensor
2.Vsio: Video monitor display processing Unit
3. Graphy: High resolution printers

42. NORMAL POSITIVE
COLORISE ZOOM

43. Advantages
-Reduction of radiation exposure.
-Instantaneous image and display.
-Control of contrast.
-Elimination of X-ray film.
-Ability to enlarge special areas.
-Potential for computer storage.
-No statistically significant differences in accuracy
between conventional and digital radiographic
methods has been observed.
Advantage-rapid imaging and reduction in radiation.

44.  Direct imaging is subdivided into two
1. Direct Digital Imaging
2. Semi-direct Image Plate System.
Direct Imaging
-Produces the image immediately on the monitor post-
exposure.
-Direct digital images are acquired using a solid state
sensor.

45. • The solid state sensors are based on charge coupled
device(CCD) or complementary metal oxide
semiconductor (CMOS) based chips.
• Semidirect images are obtained using a phosphor plate
system. Phosphor plates are flexible in nature.
Sensors are available in various sizes such as size 0, size 1
and size 2 to simulate the different film sizes used
clinically.

46. • For infection control, a disposable plastic sleeve is
fitted over the sensor and part of the cable, as the
sensor cannot be autoclaved or disinfected.
• There are two types of digital sensor array design.
-Area and linear array design
-Area arrays are used for intraoral radiography, while
linear arrays are used in extra oral imaging.

47.  -Both wired and wireless sensors can be used.
 -wireless sensors are thicker than wired.
 Disadvantages
 -Cost of devices
 -Wire attached to the sensor
 -Thickness of the sensor
 -Rigidity of the sensor
 - Infection Control : The sensors are used on multiple
patients and must be covered by barriers. Sensors that
become contaminated are incapable of being
sterilized.

48. Non Radiographic Methods
Digital Tactile Sense
-If the coronal portion of the canal is not constricted, an
experienced clinician may detect an increase in
resistance as the file approaches the apical 2-3mm.
-This detection is by tactile sense.
-In this region, the canal frequently constricts(minor
diameter) before exiting the root.
-All clinicians should be aware that this method, by
itself ,is often inexact.

49. -It is ineffective in root canals with an immature apex
and is highly inaccurate if the canal is constricted
throughout its entire length or if the canal has
excessive curvature.
-This method should be considered as supplementary to
high-quality working length radiographs or an apex
locator.

50. Apical Periodontal Sensitivity
-This method is based on patient’s pain reaction to
determine working length.
-If an instrument is advanced in the canal towards
inflamed tissue, the hydrostatic pressure developed
inside the canal may cause moderate to severe,
instantaneous pain.

51. -At the onset of pain, the instrument tip may still
be several millimeters short of the apical
constriction.
-When the canal contents are totally necrotic,
however, the passage of an instrument into the
canal and past the apical constriction may evoke
only a mild awareness or possibly no reaction at
all.

52. -On the other hand, Langeland and associates reported
that the vital pulp tissue with nerves and vessels may
remain in the most apical part of the main canal even
in the presence of a large periapical lesion
-This suggests that a painful response may be obtained
inside the canal even though the canal “contents” are
necrotic and there is periapical lesion.

53. -It would appear any response from the patient, even
an eye squint or wrinkling of the forehead, calls for
reconfirmation of working length by other
methods available.
-This is not an acceptable method anymore.

54. Paper Point Method
-In a root canal with 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 anaesthesia has been achieved.

55. -The moisture or blood on the portion of the paper point
that passes beyond the apex may be an estimation of
working length or the junction between the root apex
and the bone.
-This paper point method is a supplementary one.

56. -A new dimension has recently been added to paper
points by the addition of millimeter markings.
-These paper points have markings at 18,19,20,22 and
24mm from the tip and can used to estimate the point
at which the paper point passes out of the apex.
-The accuracy of these markings should be checked on a
millimeter ruler.

57. LIMITATION OF TRADITIONAL WORKING LENGTH
DETERMINATION
Conventional methods cannot pin point location of apical
foramen.
40% of the canals exit short of the radiographic apex either in
buccal or lingual direction.
Further more, age changes at the root apex - secondary dentin
and cementum deposition or resorption at the root apex can
move the apical constriction and cause preparation errors.

58. The use of tactile sensation has many limitations-
SEIDBERG et al 1975.
Radiographs are often misinterpreted because of the
difficulty of discerning radicular anatomy
Radiographs are of limited use in pregnant patients,
uncooperative children, pts. with severe gag reflex or
pts. with disability such as parkinsonism

59. Determination of Working Length
by Electronic Apex Locators
Evolution of Apex Locators
• Although the term “Apex Locator” is commonly used
and has become an accepted terminology it is a
misnomer.
• These devices all attempt to locate the apical
constriction, the cementodentinal junction, or the
apical foramen.
• They are not capable of routinely locating the
radiographic apex.

60. • In 1918 Custer was the first to report the use of
electronic current to determine working length.
 The scientific basis for apex locators originated and
research conducted by Suzuki in 1942
• He showed in his in vivo research on dogs using direct
current discovered that the electrical resistance
between the periodontal ligament and the oral mucosa
was a constant value of 6.5 Kilo-ohms.
• In 1960 Gordon was the second to report the use of a
clinical device for electrical measurement of root
canals.

61. • Sunada adopted the principle reported by Suzuki and
was the first person to describe the detail of a simple
clinical device to measure working length in patients.
• He used a simple DC Ohm meter to measure a
constant resistance of 6.5 kilo ohms between oral
mucous membrane and the periodontium regardless
of the size or shape of the teeth.

62. • The device used by Sunada in his research became the
basis for most apex locators.
• Inoue made contributions to the evolution of apex
locators on the Sono-Explorer by providing several
advancements and modification in the electronic
design of apex locators

63. Concept
• All apex locators function by using the human body to
complete an electrical circuit.
• One side of the apex locator circuitry is connected to
an endodontic instrument.

64. • The other side is connected to the patient body either
by a contact to the patient lip or by an electrode held
in the patients hand.
• The electrical circuit is complete when the endodontic
instrument is advanced apically inside the root canal
until it touches periodontal tissue

65. • The display on the apex locator indicates that the
apical area has been reached
• 1-3mm discrepancy is evaluated by electronic apex
locators,
• Studies have shown that radiographic estimation was
no more accurate than electronic determination.

66. basic principle on which apex locators work
1. Body around the tooth resists the flow of
current and the value of that resistance is
6.5 kilo ohms whenever current of 40 micro
amperes passes through.
2. Every “body” has a capacity to store current
whenever current flows through it. It is
called capacitance of that “body”. It is
measured in farads. It particularly happens
when 2 plates of any material are close to
each other.

67. • Apex locators are the instruments used in endodontics
to determine the working length in root canal
treatment as an adjunct to radiographs.
• They are used to locate the apical foramen by
determining the apical constriction or
cementodentinal junction.
First Generation Apex Locators

68. • First Generation Apex Locators are also called as
Resistance based electronic apex locators.
• They work by measuring opposition to the flow of
Direct Current(DC).

69. • These are based on resistance principle
• They worked best in dry canals. The original device
was reported to be most accurate in palatal canals of
maxillary molars and premolars.
• But the presence of pus, pulpal tissue, blood and
irrigants lead to inaccurate readings.
 Ex Sono -Explorer

70.  Advantages
-Easily operated
-Digital read out
-Audible indication
-Detects perforations

71. Disadvantages
-Requires a dry field
-Patient sensitivity
-Requires good contact with lip clip
-Cannot estimate beyond 2mm
Today most of the first generation apex locators are
off the market.

72. Second Generation Apex Locators
• In order to overcome the problems associated with
the resistance based apex locators.
• Works on the principle of Impedance hence they
are also called as Impedance apex locators.

73. • They work by measuring the opposition to flow of an
alternating current or impedance, these indicate the apex
when two impedance values approach each other.
• Very technique sensitive and error prone

74. Second generation apex locators
These were based on single frequency alternating
current and used to measure opposition to the flow of
alternating current or impedance.

 Alternating current has a sinusoidal amplitude wave.
The property is utilized to measure distance in
different canal conditions by using different
frequencies.
The major dis-advantage of second generation apex
locators is that the root canal has to be reasonably free
of electro-conductive materials to obtain accurate
readings.

75. • The presence of tissue and electro conductive irrigants
in the canal changes the characteristics and leads to
inaccurate, usually shorter measurements.
• Catch 22 situation---should the canals be cleaned and
dried to measure the working length or should the
working length be measured to clean and dry the
canals.

76. Advantages
-Does not require lip clip
-No patient sensitivity
-Analog method
Disadvantages
-No digital read out
-Difficult to operate
-Canals should be free of electroconductive irrigants and
tissue fluids.
-The most important disadvantage of second generation
devices was the need for individual calibration which was
done by correlation of gingival crevice sound.
Ex The Apex Finder
Sonoexplorer II

77.  Different types
1. Sono Explorer II
-It is one of the earliest of the second generation
apex locators
-Later a number of improvements were available in
the sono explorer.
2. The Apex Finder
-It has a visual digital LED indicator and is self
calibrating.
-Compared to radiographic working length
estimations, placed the accuracy at 67 percent.
3.Endo Analyzer
-I t is a combined apex locator and pulp tester

78. 4. Digipex
-It has a visual LED digital indicator and an audible
indicator.
-It requires calibration.
5. Digipex II
-It is a combination of the apex locator and the pulp
vitality tester.
6 Exact-A-Pex
-It has a LED bar graph display and an audio
indicator.
-An in vivo study reported an accuracy of 55%
(0.5mm from apex)

79. Third Generation Apex locators
• These are also called as frequency dependent apex
locators.
• Works on the principle of frequency or comparative
impedance.
• They are based on the fact that different sites in canal
give difference in impedance between high(8KHz) and
low (400Hz) frequencies.

80. • The difference in impedance is least in the coronal
part of the canal.
• As the probe goes deeper into the canal, difference
increases.
• It is greater at cemento dentinal junction

81. Advantages
-Easy to operate
-Uses K type file
-Audible indication
-Can operate in presence of fluids
-Analog read out and accuracy was 96.5%
Disadvantages
-Requires lip clip
-Chances of short circuit
Ex Endex
Root Zx
Neosono ultima
Apex Finder A.F.A

82. Different types are
1.Apex Finder AFA(all fluids allowed)
-It is a third generation apex locator.
-It functions best with an electrolyte present.
It uses multiple frequencies and comparative impedance
principles in its electronic circuitry.
-It is operated to be accurate regardless of irrigants or
fluids in the canals being measured.
It has a liquid crystal display(LCD) panel that indicates
the distance of the instrument tip from the apical
foramen in 0.1 mm increments

83. -It has an audio chime indicator.
-The display has a bar graph “ Canal condition indicator”
that reflects canal wetness or dryness and allows the
user to improve canal conditions for electronic
working length determination.
The Endo Analyzer 8005 combines electronic apex
location and pulp testing in one unit.

84. 2. Neosono Ultima Ez apex locator
-It is the third generation device that supersedes the
second generation sonoexplorer line
-Two alternating current frequencies are used with a
microchip that sorts out two of the many
frequencies to give an accurate reading in either
wet or dry canals.
-The ultima Ez is mounted with a root canal graphic
showing file position as well as an audible signal.
-I t works best in the presence of sodium
hypochlorite.

85.  3. Endo analyzer 8005
-It combines apex location and pulp tester in one unit.
-The Endo Analyzer 8005 features two self-calibrating
apex location programs that utilize five frequencies
with graphical display of the apical foramen in 0.1 mm
increments as well as an audible chime when the
foramen is reached.
4. Root Zx
-The Root Zx is mainly based on detecting the change in
the electrical capacitance that occurs near the apical
constriction.

90. Fourth Generation Apex L ocators
• These measure the resistance and capacitance
separately rather than the resultant impedance value
• There can be difference in the combination of values of
capacitance and resistance that provides the same
impedance, thus the same foraminal reading.
• Easier for a beginner to use in preflared canals.
 Ex Ray-Pex 4/Bingo-1020
 Disadvantage
• Need to perform in relatively dry canals

92. Fifth-GenerationApex locators
The Neosono-copilot is a combination of an electronic apex locator and pulp tester
and is most recent innovation in apex location
•This new generation of apex
locator can measure pulp space
lengths accurately even in the
presence of conducting fluids.
•The device provides the operator
with a digital read out, graphic
illustration and an audible
signal.
•The built in pulp tester can be
used to access tooth vitality and
determine proper and effective
anesthesia.

93. •Other examples :
Apex Locator C-root-1 (V)
Root Pi Apex Locator
Features :
•5th generation multi-frequency for the most
precise length-détermination Under both wet and
dry conditions.
•Two separate work-modes, apex locator and pulp
testing.
•Accurate up to 0.1mm
•Large LCD screen, simple to operate.
•Pulp tester gives a clear indication of the vitality.
•Progressive sound signal combined with display
on screen.

94. Advantages
•Can measure the pulp space length to the
constriction or marginally short of it.
•Safe to use irrespective of whether the pulp
space is wet, dry or filled with any conductive
fluids.
•Does not interfere with the function of cardiac
pacemakers.
•Perform very well in the presence of blood and
exudates.
•Works well in wet canals but not very
accurate in dry canals.

95. S SssiixthGenerationApexLocators
Sixth Generation Apex Locator
•Also known as Adaptive Apex Locator.
•Combines advantages of both fourth and fifth
generation apex locator
Utilizes a steady algorithm to match the canal
moisture

96.  Design:
o Sixth Generation Apex Locator is a small sized
device no longer than a dentist’s palm.
o The measuring mode provides for graphic
information to be displayed on colour
multimedia displays.

97.  By a clinician’s wish, the adaptive apex locator
will retrieve audio information either through the
familiar beeping signals typical of fifth
generation apex locators, or through sensible
speech messages.

98. o The display of the apex locator is split into 2
sectors.
 At the stage of penetrating the root
canals by means of an endodontic device
information is obtained about the start of
measurement when touching the outermost and
the inner dentine structures.

99. o In the RC, before the apex zone/sector II/, the device
provide information that we are in contact with
dentine.
oPrior to reaching the apical zone/ sector II/, and after a
sound signal, the screen displays the zones reached by
the tip of the instrument.

100. o The device issues sound or speech information that
repeats the data on the display/ “two” - if the tip is in
zone II before the physiological narrowing “one” - if
the tip is in zone I before the physiologic narrowing
.
o The appearance of the message “apex” means that the
tip of the instrument is between the physiological
narrowing and the anatomical foramen

101. oThe message “over” means that the tip has passed through the
anatomical foramen.
Examples:
•Root RZ-600
•MAL-III
•Apex locator (BSC-AL12)

102. Problems associated with apex locators
1.Biological phenomenon's such as inflammation can
have effect on accuracy.
2.Short circuiting can occur due to presence of metallic
restorations
3.Canal patency is another issue as the presence of
dentinal debris may disrupt the electrical resistance
between the inside of the canal and the periodontal
ligament

103. 4.Immature or blunderbuss apices tend to give short
measurements when apex locators are used
5.Interface with cardiac pace makers
6.Medico legal issues. The use of apex locator alone with
out pre and post operative radiograph is not
recommended practice due to large variation in
tooth morphology and medico legal record keeping
requirements

104. Uses of apex locators
Apex location
Detect root perforation
Diagnostic test for root fractures
Multiple functions with vitality testing function as well as
combination of apex locator and electric hand pieces.
Combination of apex locator and Ultrasonics.

105. Contraindications
-The use of apex locators and other electrical devices
such as pulp testers, electrosurgical instruments and
desensitizing equipment, is contraindicated for
patients who have cardiac pacemakers.

106. BETTER METHOD ????
 Comparison of working length determination with
radiographs and four electronic apex locators by
J.P.Vieyra et al.in 2011 concluded that Measuring the
location of the apical constriction using the four apex
locators ( Root ZX, Elements, Precision AL, Raypex 5) was
more accurate than radiographs and would reduce the risk
of instrumenting and filling beyond the apical foramen.

107.  Accuracy of working length determination
using 3 electronic apex locators and direct
digital radiography by Real et al. in 2011
concluded that Root ZX and Elements Diagnostic
are more accurate in determining working length
when compared with Just II and Schick direct
digital radiography.

108. CONCLUSION
 A combination of radiographic and other methods are
essential for working length determination .

109. THANK YOU