2. CONTENTS
• Introduction
• History
• Definitions
• Clinical consideration
• Methods of determining working length
• Recent advances
• Working width
• Conclusion
• Bibliography
3. INTRODUCTION
• Seltzer et al were the first to report greater success in
terminating cleaning & obturating the root canal system just
short of the radiographic apex rather than overfilling or
underfilling.(Seltzer S et al.Biologic aspects of endodontics.III Periapical tissue
reactions to canal instrumentation.Part II.Oral Surg Oral Med Oral Pathol Endod
1968;26:694-705)
• Sjogren et al reported the best outcome was when the canal
filling was between 0-2mm short of radiographic apex
4. • According to Cohen and Burns, 1 mm of a canal with a diameter of
0.25mm, which is the diameter of narrower foramens, provides
enough space to lodge nearly 80,000 streptococci.so filling should be
at the apex.
• Chugal found variations in success rates of root filled at different
levels :
• Normal preoperative pulp & periapical tissues – filled over 1mm from
radiographic apex
• Necrotic pulp & apical periodontitis – canal filling closer to
radiographic apex
Chugal NM,Clive JM et al.A prognostic model for assessment of the outcome treatment:effect of
biologic & diagnostic variables.Oral Surg Oral Med Oral Path Endod 2001;91:342-52
5. HISTORICAL PERSPECTIVES
• End of 19th
century: WL was calculated when file was placed in canal
& patient experienced pain
• 1899 : Kells introduced X-rays in dentistry
• 1929 : Collidge studied the anatomy of root apex in relation to
treatment problems
• 1955 : Kuttler microscopically studied the microscopic anatomy of
root tip, and decided that filling to the radiographic apex was an
unwise clinical procedure, contributing to post operative pain.
• 1969 : Inove significantly contributed to evolution of electronic apex
locators
6. DEFINITIONS
• Working length : the distance from a
coronal reference point to the point at
which canal preparation and obturation
should terminate (seventh edition of the
Glossary of Endodontic Terms)
• Reference point : It is the site on the
occlusal or incisal surface from which
measurements are made.
This point is used throughout canal
preparation & obturation
7. Anatomy of the Root Apex
(Kuttler’s studies)
A.Anatomic apex
B.Apical constriction (minor
diameter)
F. Apical foramen
The study of the dimensions of the internal anatomy of teeth has
been a challenge since the studies of Kuttler, Kerekes and Trostand
9. • CEMENTODENTINAL JUNCTION (CDJ)
CDJ does not always coincide with apical constriction.location of CDJ is
0.5-0.3 mm short of the anatomic apex.
Langeland
10. • APICAL FORAMEN :
An accessory foramen is an orifice on the
surface of the root communicating with a
lateral or accessory canal.They may exist as a
single foramen or as multiple foramina
Region where the canal leaves the root surface next to the periodontal ligament ( American
Association of Endontists,1984)
The apical foramen deviates from the root tip in at least two-thirds of all
teeth.this deviation occurs towards the buccal or lingual aspect TWICE
often as it does towards the mesial or distal aspect
Levy and Glatt
11. • LATERAL CANALS
• Periodontal vessels curve
around the root apex of a
developing tooth and
become entrapped in
Hertwig’s epithelial root
sheath resulting in
formation of lateral canals
• APICAL DELTA
• Branching patern of small
acessories canals and minor
foramen seen at the tip or
apex of some tooth
12. • APICAL CONSTRICTION :
It is the narrowest part of the root canal with the smallest
diameter of blood supply and preparation to this point
results in a small wound site and optimal healing conditions
(Ricucci & Langeland 1998)
13. Topography of the apical constriction (DUMMER
CLASSIFICATION)
“Traditional” single apical constriction was present more than half the time
JADA 16:1456;1929
14. MAJOR AND MINOR DIAMETER
Distance between major
diameter and minor
diameter
• 0.524mm (18-25yrs).
• 0.659 mm (55 yrs +)
(kutlers study,JADA 1955)
15. MORNING GLORY APPEARANCE
• From the AC (minor apical diameter) the canal widens as it
approaches the AF (major apical diameter).
• The space between the major and minor diameters has been
described as funnel shaped or hyperbolic or the shape of a
morning glory flower
16. SIGNIFICANCE OF WORKING
LENGTH
1. Determines how far into the canal the instruments are
placed & worked & thus how deeply the tissues, debris,
metabolites are removed .
2. Limits the depth to which the canal filling may be placed.
3. Affects the degree of pain & discomfort that the patient will
feel following the appointment.
4. If calculated within correct limits, it will play an important
role in determining the success of the treatment &
conversely, if calculated incorrectly, may cause the
17. Failure to accurately determine &
maintain working length
o Length too long can lead to :
1. Perforation through apical
constriction
2. Overfilling or over extension
3. Increased incidence of post
operative pain.
4. Prolonged healing period.
5. Lower success rate, owing to
incomplete regeneration of
Cementum, Periodontal
ligament and Alveolar bone
o Short working length can lead
to :
1. Incomplete cleaning
2. Underfilling
3. Persistant discomfort
4. Incomplete apical seal, apical
leakage which supports the
existence of viable bacteria and
contributes to a peri-radicular
lesion
5. Lower success rate
18. APICAL ROOT ANATOMY &
ITS IMPACT ON W.L
• Mandibular molar with apical root
resorption due to a necrotic, infected
dental pulp that destroyed the
natural cemental-dentinal junction.
• Histologic evidence of apical
resorption on external cementum
(black arrows) and layering of
cementum
19. Apical view of tooth with a C-shaped root formation.
Note root morphology around the canal exits as
cementum invaginates into the foramen. K-files (arrows)
are exiting from the canal long before they reach the
actual root surface. Actual foramina are much larger than
canal exits, as indicated by widths of the red lines.
Working length determination to the root length in these
cases would be destructive to periapical tissue.
These potential anatomic variances have had a
major impact on the precise region or location
for determining the working length and
termination of root canal instrumentation and
obturation
20. • Prior to establishing a definitive working length, coronal
access to the pulp chamber must provide a straight-line
access into the canal orifice, thereby facilitating
subsequent canal penetration.
• In anterior teeth, failure to remove the lingual ledge or
incisal edge often impedes this straight-line access,
resulting in lack of depth penetration to the CDJ, failure
to locate all canals present, or instrument penetration
into the canal wall with ledge formation.
• In posterior teeth, primarily molars, or multirooted
premolars, failure to remove cervical ledges or bulges
results in missed canals or binding of the penetrating
instrument in the coronal third of the canal with ledge
formation.The ability to penetrate unimpeded to
the
CDJ is crucial to determining the
22. HOW TO MEASURE W.L?
– In this era of improved illumination and magnification
working length determination should be to the nearest one
half millimeter,which is the maximum resolution of the
naked eyein working distance .
– Measurement should be made from a secure reference point
on the crown, that can be identified and monitored
accurately, in close proximity to the straight line path of the
instrument.
23. A silicon stop is a common aid for evaluating the
working length measurement and returning to a
secure reference point
Care must be taken to assure that the stop is placed
on the file and measured at a right angle to the file.
Otherwise, differences in length of a millimeter or
more between files may occur, leading to either
perforation and stripping of the apical foramen or
inadequate cleaning and shaping of the apical seat,
with corresponding loss of length
24. – Commercial stops, made of :
i. Metal
ii. Silicon rubber
iii. Plastic
Tear drop shaped
Round
25. – Advantages :
1. Do not have to be removed during sterilization.
2.In curved canals, to indicate the curvature - special tear -
shaped or marked rubber stops can be positioned with the
direction of the curve placed in a pre-curved stainless steel
instrument .
– Disadvantages :
1.Time consuming.
2.May move up and down the shaft which may lead to
preparations short or past the apical constriction
Metal or silicone stoppers to mark the working length. The
stopper must clearly correspond to a cusp tip and rest
firmly on it. For electronic determination of working length,
the silicone stopper (left) is better than a metal stopper
(right) because the metal stopper can cause a short circuit
26. – Length adjustment of the stop attachments
should be made against the edge of a sterile
metric ruler or a gauge made specifically for
Endodontics.
– Eg - Guidener Endo - M - Bloc (Dentsply/Maillefer)
Has 32 depth guides in 2 rows. Front row indicators from 10-30 mm in 1mm
increments.
27. • Some instruments have millimeter marking
rings etched or grooved into the shaft .
• These act as a built-in ruler with the markings
placed at 18, 19, 20, 21,22,23 & 24mm
28. METHODS OF WORKING
LENGTH DETERMINATION
1. Radiographic method-
• Best’s method
• Bregman’s method
• Bramante’s method
• Grossman formula
• Ingles method
• Weine’s method
• Kutler’s method
• Radiographic grid
• Euclidean endometry
• Xeroradiography
• Direct digital
radiography
2. Non Radiographical
methods-
•Digital tactile sense
•Apical periodontal
sensitivity
•Electronic apex locator
•Paper point method
29.
30. SCHOOL OF THOUGHTS:
1.Those who follow this concept say that the CDJ is impossible to
locate clinically & radiographic apex is the only reproducible site
available for length determination
2.Those who don’t follow this concept say the position of
radiographic apex is not reproducible.its position depends on a
number of factors like tooth angulation,position of film & film
holder,adjacent anatomic structures,etc.
32. When two superimposed canals present, either-
A.Take 2 individual radiographs with instrument placed in
different canal at each time
B. Insert two different instrument- K file in one canal, H file in
other canal and take radiographs at different angulations.
C. Apply SLOB rule, that is expose tooth from mesial or distal
horizontal angle, canal which moves to same direction, is
lingual where as canal which moves to opposite is buccal
33. i. BEST’S METHOD
• Introduced in 1960
• A steel pin measuring 10 mm is fixed to the labial
surface of root with utility wax,keeping the pin
parallel to long axis of tooth & a radiograph is taken
• Then measurements were made with the help of a
BW gauge
34. ii. BREGMAN’s METHOD
• 25mm length flat probes are prepared & each has a steel
blade fixed with acrylic resin as a stop,leaving a free end of
10mm for placement into root canal
• This is placed in the tooth until the metallic end touches the
incisal edge or cusp tip of the tooth. Then a radiographic is
taken & following are measured –
ALT : apparent length of tooth
RLI : real length of instrument
ALI : apparent length of instrument
RLT = RLI x ALT/ALI
35. III. BRAMANTE’S METHOD
Introduced in 1974
Used stainless steel probes of various calibres & length
They were bent at one end at right angles & this bend is inserted
partially into acrylic resin in such a manner that its internal
surface is in flush with the resin surface contacting tooth surface
The probe is introduced in the canal such that the resin touches
the incisal or cusp tip taking care to see that the bent segment of
the probe would be parallel to mesiodistal diameter of crown
thus making it possible to visualize on radiograph
36. • In this radiograph the reference
points are as follows –
A : internal angle of intersection of
incisal &radicular probe segment
B : apical end of probe
C : tooth apex
Tooth length calculated in 2 ways :
(I) Measure radiographic image
length of probe A-B,measuring
radiographic image length of tooth
from A-C & then measuring real
37. Now following equation is applied :
CRD – real tooth length
CRS – real probe length
CAD – tooth length in radiograph
CAS – instrument length in radiograph
(II)Measure distance bet apical end of probe &
radiographic apex.add or subtract to obtain correct
WL
CRD = CRS x CAD/CAS
38. IV. GROSSMAN’S METHOD
CLT = KLI × ALT / ALI
• CLT= correct length of the tooth
•KLI= known length of the
instrument in the tooth
•ALT= apparent length of the
tooth on radiograph
•ALI= apparent length of the
instrument on radiograph
DISADVANTAGES :
Wrong reading can occur
because of :
1)Variations in angles of
radiograph
2)Curved roots
3)s-shaped , double curvature
canals
4)A small error will be
multiplied
39. V. INGLE’S METHOD
This method
recommended by
Ingle and reviewed
by Bramante and
Berbert, and
reported that this
method is superior
to other methods
40. VII. WEINE’S MODIFICATION
MODIFICATION IN LENGTH SUBTRACTION :
1)No resorption – subtract 1mm
2)Periapical bone loss – subtract 1.5mm
3)Periapical bone loss+root apex resorption – subtract 2mm
41. VIII. KUTTLER’S METHOD
• In young patients, average distance between minor and
major diameter is 0.524 mm where as in older patients its
0.66 mm
Advantages
•Minimal errors
•Has shown many successful
cases
Disadvantages
•Requires radiograph of
highest quality
•Time consuming
•Complicated
42. IX. X-RAY GRID
SYSYTEM
• Everett & Fixott in1963
• Consists of lines 1mm apart running lengthwise &
crosswise.
• Every 5th
millimeter is accentuated by a heavier line to
make reading easier
• Enameled copper wires are place in a Plexiglas & fixed
to a regular periapical film.
• The grid is taped to a film to lie in-between the tooth &
film during exposure so patterns become in cooperated
in the finished film
44. X. EUCLIDEAN ENDOMETRY
• Uses 2 geometrically distorted radiographs in
determining real length of tooth.
• The 2 radiographs are taken with a cone fitted with
a “updegraves XCP”(extension cone paralleling
method)device at 2 different vertical angulations
• The actual tooth length is calculated by geometric
principles from the length of the tooth in the two
radiographs & the known verticular angular
differences
45. XI. Walton and Torabinejad method
• Diagnostic film taken using paralleling technique & length is
measured
• From this 3mm is subtracted to obtain estimated working
length
• Place stops at this length to a series of files
• Then radiograph is taken
• Corrected working length is determined by measuring the
discrepancy between the tip of the file and the
radiographic apex
• File is then adjusted 1-2mm short of the radiographic apex
• No.8 , No.10 files are not used
46. XI. XERORADIOGRAPHY
• The term Xero-radiography is derived from the Greek
word XEROS which literally means dry which
differentiates this from the conventional
photochemical system.
• Newer technique
47.
48. XII. DIRECT DIGITAL
RADIOGRAPHY
• In this digital image is formed which is represented
by spatially distributed set of discrete sensors &
pixels
49. <A> RVG :
• invented by Dr. Frances Mouyens in 1984
50. ADVANTAGES :
•Low radiation dose
•Darkroom is not required as instant image is viewed
•Quality of the image is consistent
•Greater exposure latitude
•Image distortion from bent films is eliminated
DISADVANTAGES :
•Expensive
•Large disk space required to store images
•Bulky sensor with cable attachment can make placement in
mouth difficult
•Soft tissue imaging is not very accurate
51. <b> phosphor imaging system
Image is captured on a phosphor plate as analogue
information & converted into digital format when
plate is processed
ADVANTAGES :
1.Low radiation dose
2.Instant images are formed
3.Image manipulation facilites
4.Receptor is same size as film
53. ADVANTAGES AND DISADVANTAGES OF
RADIOGRAPHIC METHOD -
ADVANTAGES :
1.Can see anatomy of tooth
2.Can see curvature in roots
3.Can see relationship b/w adjacent teeth & anatomic structures
DISADVANTAGES :
1.Varies with different observers
2.Superimposition of anatomic structures
3.2D view of a 3D object
4.Radiation exposure
5.Cannot interpret if apical foramen has buccal or lingual exit
6.Limited accuracy
54.
55. I) DIGITAL TACTILE SENSE
ADVANTAGES :
•Time saving
•No radiation exposure
DISADVANTAGES :
•In case of narrow canals
one may feel increased
resistance as file
approaches apical 2-3mm
•In case of teeth with
immature apex,instrument
can go periapically
•In case of anatomical
variations in apical
constriction,sclerosis,
resorption, tooth type
and age this method
becomes unreliable
56. • Seidberg et al. reported an accuracy of just 64%
using digital tactile sense
• This method should be considered supplementary to
high-quality, carefully aligned, parallel, working
length radiograph or an apex locator
57. II) PERIODONTAL
SENSITIVITY TEST
• This method does not provide accurate readings, for
example in case of narrow canals, instrument may feel
increased resistance in apical 2-3mm.In immature apex, file
goes beyond apex.
• In case of canals with necrotic pulp, instrument can pass
beyond apical constriction, and in case of vital or inflamed
pulp, pain may occur several mm before periapex is
crossed by instrument.
58. III) PAPER POINT
MEASUREMENT METHOD
This method, however, may give unreliable data :
1. If the pulp not completely removed
2. If the tooth is pulpless but a periapical lesion rich
in blood supply is present.
3. If paper point is left in canal for a long time.
59. IV) ELECTRONIC APEX
LOCATOR
In addition to radiography,tactile sensation has been
used with questionable success , plus the drawbacks
cited about radiographic length determination along
with increasing concern about radiation exposure ,the
introduction & development of apex locators was
received with enthusiasm
These devices do not assess the position of the root apex and
the name “electronic apex locator” is not appropriate ;
“electronic apical foramen locator” or “electronic root canal
length measurement device” as a generic name would be
more appropriate.
60. • The ability to distinguish between minor & major
diameter of apical terminus is the most
important for creation of APICAL CONTROL
ZONE.
• The apical control zone is the mechanical
alteration of the apical terminus of root canal
space that provides resistance & retension form
to the obturating material against the
condensation pressure of obturation
62. PARTS OF APEX LOCATOR :
– has four parts :-
the lip clip
the file clip
Electronic device
Cord which connects the above
three parts
63. USES OF APEX LOCATORS :
1. Provide objective information with high degree of accuracy
2. Used when apical portion of canal is constricted :
• Impacted teeth
• Zygomatic arch
• Overlapping roots
• Excessive bone density
3. Used in patients with gag refles and cannot tolerate x-ray films
4. In pregnant ladies to reduce radiation exposure
5. Useful in children,disabled patients,heavily sedated patients,etc
64. 6. Can be used in teeth with incomplete root formation
,requiring apexification & to determine WL in primary
teeth
7. Valuable tool for :
i.Detecting site of root perforations
ii.Testing pulp vitality
iii.Determination of perforations caused during post preparation
iv.Detecting horizontal or vertical root fractures
v.Detecting internal or external resorption
65. Basic conditions for accuracy of
eals :
1. Canal should be relatively dry
2. Canal should be free from debris
3. No cervical leakage
4. No blockage or calcification of canals
5. Proper contact of file with canal walls &
periapex
66. CLASSIFICATION :
TYPES OF APEX LOCATORS
BASED ON DIRECT CURRENT BASED ON ALTERNATING CURRENT
ORIGINAL OHM
METER USED BY
SUZUKI & SUNANDA
RESISTANCE TYPE
•Root canal meter
•Endometric
meter
IMPEDENCE TYPE
•sonoexplorer
FREQUENCY TYPE
SUBTRACTION TYPE
•Endex
•Neosono ultima EZ
RATIO TYPE
2 FREQUENCIES
•Root ZX
5 FREQUENCIES
•AFA
•Apex finder
67. FIRST GENERATION APEX
LOCATOR
• Resistance apex locators
• Measures opposition to flow of direct current (ie
resistance)
• Eg : - root canal meter (Onuki Medical co.,japan)
- endometric meter
- endometric meter S II (Onuki Medical Co.)
68. • ADVANTAGES :
1. Easily operated
2. Digital readout
3. Audible indication
4. Detect perforation
5. Can be used with K-file
• DISADVANTAGES :
1. Requires a dry field
2. Patient sensitivity
3. Requires calibration
4. Requires good contact with lip clip
5. Cannot estimate beyond 2mm
69. SECOND GENERATION APEX
LOCATOR
• Inoue introduced the concept of impedance based AL
• PRINCIPLE :measures opposition to flow of alternating
current or impedence
egs : -Sonoexplorer
-Apex finder
-endo analyzer
-Digipex
-Digipex II
-Exact-A-Pex
70. • ADVANTAGES :
1.Does not require lip clip
2.No patient sensitvity
3.Analog meter
4.Detects perforations
• DISADVANTAGES :
1.No digital readout
2.Difficult to operate
3.Requires coated probes
71. THIRD GENERATION APEX
LOCATORS• Based on the fact that different sites in the canal give
difference in impedance b/w high (8 KHz) & low(400 Hz)
frequencies
• Difference in impedance is least in the CORONAL part &
greatest at the CDJ
• As impedance is influenced by frequency of current flow
these are also known as frequency dependent
• They should be called comparative impedance because
they measure magnitudes of impedance which is converted
to length information
72. • Egs :
• Endex (original 3rd
gen AL)
• Root ZX (shaping & cleaning of canals with simultaneous monitoring
of WL)
• Mark V plus
• Co-pilot
• Endo analyser 8005
73. • ADVANTAGES :
1. Easy to operate
2. Audible indication
3. Can operate in presence of fluids
4. Analogue readout
5. Uses K-file
• DISADVANTAGES :
1. Requires lip clip
2. Chances of short circuit
3. Needs fully charged battery
4. Must calibrate each canal
74. FOURTH GENERATION APEX
LOCATORS
• Measures resistance & capacitance separately
• There can be different combination of values of
capacitance and resistance that provides the same
foraminal reading
• This is broken down into primary components and
measured separately for better accuracy and thus
less chances of occurrence of errors
• Eg :neosono ultima ZX
sybronendo
75. FIFTH GENERATION APEX
LOCATORS
• It uses multiple frequencies rather than the dual
frequencies of the third and fourth generations of apex
locators, so it works in dry or wet canals and requires no
calibration. Eg :RAYPEX
76. SIXTH GENERATION APEX
LOCATORS
• Also called adaptive apex locators
• Multi-frequency Operating System
• Sound operated switching device can produce
different kinds of sound to indicate the different
positions of file in the root canal. Dry and wet
condition are also available for accurate reading
77. COMBINATION OF A.L &
ENDODONTIC HANDPIECES
•Tri auto ZX
•Safy ZX
•Endy 7000
78. TRIAUTO ZX
– Is cordless electric endodontic handpiece with built in
RootZx apex locator. The handpiece uses Ni-Ti rotary
instruments that rotate at 280±50 rpm.
oAuto start-stop mechanism
oAuto torque reverse mechanism
oAutoapical reverse mechanism
The Root ZX is not capable of detecting the '0.5 mm from the foramen' position and thus,
should
only be used to detect the major diameter. (i.e. Contrary to manufacturer claims,
Apex Locators can only reliably determine when the file is actually touching the PDL at the
apex. Set your working length 1 to 1.5 mm back from this length to avoid over-instrumentation).
Ounsi HF, Naaman A. In vitro evaluation of the reliability of the Root ZX electronic apex
locator. Int Endod J 1999;32:120-23.
79. ENDY 7000
•Endodontic handpiece connected to an endy apex
locator
•Reverses the rotation of the instrument when it
reaches a point in the apical region preset by the
clinician
80. SAFY ZX
•New development of ultrasonic systems
•Handpiece + apex locator
•Uses Root ZX to monitor location of file during
instrumentation
•Minimizes danger of over instrumentation
81. Comparison of accuracy of two electronic apex
locators in the presence of various irrigants: An in
vitro study
• Aim: This study was designed to compare the accuracy of Root ZX
and SybronEndo Mini EALs, in the presence of various irrigants.
• Conclusion: The measurements of Root ZX in the presence of saline
& 1% NaOCl were closer to the AL and with no significant difference
between them, while significant differences were observed with 2%
CHX & 17% EDTA .Sybron Mini, in the presence of saline, 1% NaOCl
and 17% EDTA, gave measurements which were shorter than the AL,
whereas, in the presence of 2% CHX,WL was more accurate.
Although statistically significant differences existed between the
irrigants the majority of the readings were within the acceptable
range of ±0.5 mm for both EALs. overall accuracy of measurements
by Root ZX and Sybron Mini was 88.3% and 87.5%, respectively.
J Conserv Dent 2012;15:178-82
82. An in vitro evaluation of the
accuracy of the Root-ZX in the presence of
various agents.
• The purpose of this study was to evaluate the accuracy of the Root
ZX in vitro in the presence of a variety of endodontic irrigants: Saline,
2% Lidocaine with 1:100,000 epi., 5.25% NaOCl, RC Prep & 3%
hydrogen peroxide.
RESULTS : The most deviation (raw numbers) occurred with NaOCl, but
it was not statistically significant. The Root ZX was able to
consistently determine the location of the apical foramen (within
approximately ±0.4mm) in the presence of any of the tested irrigants
(only fill the canal, not the chamber during EAL use).
J Endodon 2001;27:209-11
83. Evaluation of working length determination
methods: an in vivo / ex vivo study.
• This comparative study was done to determine the accuracy in
measuring the working length of root canal using tactile method,
electronic apex locator and radiographic method, in vivo and
comparing the lengths so measured to the actual working length, ex
vivo, after extraction.
• The results indicated that among the three methods, the electronic
apex locator showed the highest accuracy and the highest reliability
for working length determination
Indian J Dent Res. 2007 Apr-Jun;18(2):60-2
84. An in vivo evaluation of different methods
of working length determination
• The purpose of this in vivo study was to compare the ability
of digital tactile, digital radiographic and electronic
methods to determine reliability in locating the apical
constriction.
• RESULT : The percentage accuracy indicated that EAL
method (Root ZX) shows maximum accuracy, i.e. 99.85%
and digital tactile and digital radiographic method (DDR)
showed 98.20 and 97.90% accuracy respectively
J Contemp Dent Pract. 2013 Jul 1;14(4):644-8
85. Comparison of working length determination using
apex locator, conventional radiography and
radiovisiography: an in vitro study.
• The purpose of this study was to compare
the working length determination done using three
methods, namely, apex locator (Foramatron D-10, Parkell),
radiovisiography (Planmeca) and conventional radiography
• Result: The results revealed that all the three methods
located the apex nearly as accurately as the actual root
canal length obtained by histological ground sectioning,
and among three methods apex locator being the closest to
the actual root canal length.
• Journal of contemporary dental practice july 201213(4)550
86. Precision of Endodontic Working Length Measurements:
A Pilot Investigation Comparing Cone-Beam Computed
Tomography Scanning with Standard Measurement
Techniques
• Study was conducted to evaluate the utility and precision
of already existing limited CBCT scans in measuring the
endodontic working length, and to compare it with
standard clinical procedures
• Result suggested that great correlation was found between
the endodontic working length as measured in the CBCT
images and the EAL
JOE August 2011
88. (A) LASER OPTIC DISK STORAGE
• Laser optical disks are a useful medium to store
radiographic images.
• An 8-inch optical disk is capable of storing up to 10,000
images with a 0.5 sec retrieval & display time.
• The image is recorded by a focused laser beam heating a
thin tellurium sub oxide at specific points on the optical
disk.
• When compared with normal radiographs, this method has
been shown to produce images of superior diagnostic merit
89. (B) CONE BEAM COMPUTED
TOMOGRAPHY
• Has been introduced that may prove to be more
efficient and economical than either conventional
tomography or computed tomography
• CBCT uses a round or rectangular cone shaped x ray
beam centered on a 2-dimentional x ray sensor to scan
a 360 degree rotation about the patients head
• The radiation dose delivered to the patient as aresult of
one CBCT may be as little as 3% to 20% that of
conventional CT scan.
90. The radiation dose delivered to the patient as
aresult of one CBCT may be as little as 3% to
20% that of conventional CT scan.
92. Introduction -
• Haga found that mechanical preparation of root
canal to two sizes larger than the original was
adequate
• Walton’s histologic study showed that canals that
were instrumented to three sizes larger still were
not thoroughly cleaned.
Dr. Tapish Garg et al. / IJRID Volume 3 Issue 4 Jul-Aug. 2013
The horizontal dimension of the root canal system is not only more
complicated
than the vertical dimension (root canal length or working length) but
also more difficult to investigate because the horizontal dimension
varies greatly at each vertical level
93. • “The initial and post instrumentation horizontal
dimensions of the root canal system at WL and other
levels” Dent Clin North Am. 2004 Jan;48(1):323-35.
• Minimum initial working width (Min IWW)
• maximum final working width (Max FWW)
Current descriptions of the horizontal dimensions (crosssections)of the
root canal –
1. Round (circular) : Max FWW equals Min IWW
2. Oval : Max FWW is greater than Min IWW (upto two times more)
3. Long Oval : Max FWW is two or more times greater than Min
IWW (upto four times more)
4. Flattened (flat, ribbon) : Max FWW is four or more times greater
than Min IWW.
5. Irregular : cannot be defined by above
95. FACTORS AFFECTING WORKING WIDTH
DETERMINATION :
1. Canal Shape
2. Canal Length
3. Canal Taper
4. Canal Curvature
5. Canal Content
6. Canal Wall Irregularities
Without the knowledge of above factors, “key hole or dumbbell”
effects can occur with reaming or
modified reaming actions . So, Circumferential instrumentation can
conform to the outline of
horizontal dimensions of root canal at different levels of canal.
96. Apical Widening Concepts by various
authors:-
MAXILLARY TEETH RECOMMENDED APICAL ENLARGEMENT
Central incisor 70-90
Later incisor 60-80
Canine 50-70
First premolar One canal : 50-70
Two canals : 35-50
Three canals : 35
Second premolar One canal : 40-70
Two canals : 35-50
Three canals : 35
molars MB root with one canal : 35-50
MB root with two canals : 35-45
DB root : 40-60
Palatal root : 60-100
TRONSTAD CONCEPT
97. Dr. Tapish Garg et al. / IJRID Volume 3 Issue 4 Jul-Aug. 2013
MANDIBULAR TEETH RECOMMENDED APICAL ENLARGEMENT
Incisors One canal : 35-60
Two canals : 35-50
Canines 40-70
First premolar 40-70
Second premolar One canal : 40-70
Two canals :35-50
molars Mesial root :35-45
Distal root
One canal : 60-80
Two canals : 40-60
98. • Few points against it:-
• Weine et al stated that bringing every canal to
similar size is incorrect as some canals will be vastly
overprepared and others will be insufficiently
cleaned.
• Wu et al,2008 stated that since diameters of apical
canals vary greatly in all tooth groups , no standard
size is advisable for apical enlargement.
99. • Few points against it:-
• Taking successively larger files to same length in
curved canal lead to apical lacerations or ledging
• Wu et al stated that first file to bind didn't reflect
the apical diameter and aim of removing infected
dentin may not be achieved.
WEINE’S CONCEPT
100. to sum up….
• Not possible to determine canal diameter from
radiographs.CT scans are needed
• Clinically, canal width – series of K-files suggested
by Ruddle
• Depends on-file type & preflaring
• Wu et al – diameter of the “binding” instrument
was smaller than canal diameter in 90% cases
• Preflaring is essential (Tan & Messer)
So keeping in mind all the above mentioned factors, canals
should be enlarged until necrotic dentin is removed and
search still goes on…
