EVIDENCE-BASED APPROACH TO ROOT CANAL CLEANING AND SHAPING / /certified fixed orthodontic courses by Indian dental academy

EVIDENCE-BASED
APPROACH TO
ROOT CANAL CLEANING
AND SHAPING

INDIAN DENTAL ACADEMY
Leader in Continuing Dental Education
www.indiandentalacademy.com

• Introduction
• What is Evidence Based Dentistry?
• What is cleaning and shaping??
• History of cleaning and shaping
• Objectives
• Armamentarium
• Techniques of canal instrumentation
• Non instrumentation technique

Introduction
Endodontic treatment is divided into
3 main phases
• Bio mechanical preparation
• Disinfection
• Obturation
The first step for effective BMP is
straight line access
Next step is exploration of the canal,
extirpation of remaining pulp
tissues and gross debridement of
necrotic tissues
Followed by proper instrumentation,
irrigation and debridement and
disinfection of the root canal

What is Evidence Based
Dentistry ??

The foundation for Evidence Based practice was
laid by David Sackett who has defined it as

“Integrating individual clinical expertise with
the best available external clinical evidence
from systemic research”

Evidence based dentistry; DCNA; Vol 46;no 1:Jan 2002


What is Cleaning and Shaping??
Major Objective of root canal treatment is to
remove the contents of the canal and
adjacent tissues in such a way that filling
procedures that follow will be facilitated….

To describe this aspect of treatment lucidly,
Schilder has dubbed these procedures
Cleansing and Shaping in emphasis of the
need for the debridement and development of a
specific receptacle for the filling material

History of Cleaning and
Shaping
1893 - Emil Schreier/Vienna -mixture of alkali
metals for cleaning and disinfecting root canal
1894 - Dr Callahan/Cincinnati used Sulphuric acid
within canals to clean root canals
1900 - Dr Harlan -Papain for digesting dead
tissues
1917 - Dr Hermann Prinz - 1% sodium chloride
during electromedication
1941 - Dr Louis Grossman - 5.25% sodium
hypochlorite dissolved pulp tissue in vitro


Principles of Endodontic Cavity
Preparation
 Coronal cavity preparation

I. Outline form
II. Convenience form
III. Removal of remaining carious dentin
IV. Toilet of cavity

 Radicular cavity preparation

I. Outline / Convenience form
IV. Toilet of cavity
V. Retention form
VI. Resistance form

Objectives of Cleaning and
Shaping
• Biologic
To free the root canal from pulp, bacteria and their
endotoxins
• Mechanical
 A continuously tapering preparation
 Original anatomy maintained
 Position of the foramen maintained
 Foramen as small as is practical


Traditional cleaning and
shaping breakdowns
 WORKING SHORT

 APICAL PREPARATION FIRST

 INSTRUMENTS AND METHODS OF
USE


Armamentarium for canal
preparation

 Instruments

 Cleaning reagents, Devices and Indicators


Instruments used for
canal preparation

 Broaches
 Hand Instruments
 Rotary NiTi Instruments


Endodontic Hand
Instruments
 Files

 Reamers

 Hedstroems

 NiTi Hand Files


Hand Files
• K files • K flex files
• Square blanks with • Diamond shaped
90o blank,80o
• Rasping/Filing motion • Greater flexibility


Hand Files
• Reamers

• Triangular blanks,60o
• Clockwise reaming action


Hand Files
• Hedstroems
• H style modifications include S file and U
file
• E. Schafer et al determined that
Hedstroem files had better cutting
efficiency than S or U files

IEJ 1996, 29, 302-08

Hand Files
• NiTi Hand Files
• NiTi K hand files, NiTi Mac hand files , NiTi
Hedstroem files, NiTi flex R hand files, NiTi U
hand files, NiTi X Hand Files, NiTi S Hand files

• G. Nagy et al concluded that NiTi K-files
produced more appropriate shapes in the roots
with apical curved canals than NiTi S-files

IEJ 2002, 35, 283-88.


NiTi Rotary Instruments
 Light speed

 Profile

 Quantec

 Flexmaster

 ProTaper

 Race

 K3

 Mtwo

Terminologies used
• Rake angle
 Angle formed by the cutting edge and the
cross section taken perpendicular to the
long axis of the instrument
 POSITIVE RAKE ANGLE:Hero 642,K3
 NEGATIVE RAKE ANGLE: Profile, Protaper, Quantec,
Lightspeed , RaCe


Terminologies used
• HELICAL ANGLE
 Angle that the cutting edge makes with
the long axis of the file

 Varying Angle: Protaper, Quantec, K3, RaCe
 Constant Angle:Profile, Hero 642, and Lightspeed


Terminologies used
• PITCH
 Pitch refers to the number of flutes per unit
length

 Constant pitch
 Variable pitch


Terminologies used
• RADIAL LANDS
 Surfaces that project axially from the
central axis between the flutes

 Flat : Profile, GT
 Recessed : Quantec
 Combination : K3


 Light speed
 Short flame shaped

 Reduced diameter
shaft

 Decreased incidences
of canal
transportation


 Profile  Profile GT
 Tri helical, symmetric, • Same U shaped
U shaped flutes designs incorporated
separated by lands • Greater tapers
 Constant pitch available
 Instrument becomes • Variable pitch
rather stiff before apical
preparation has been
sufficiently enlarged


 Quantec  K3
 Wide radial land
 Positive rake angle, wide
 Safe cutting tip is radial lands and a
specially designed for peripheral blade for
small, narrow canals and reduced friction
calcified canal systems  Shaping ability similar to
that of ProTaper

IEJ 36:288,2003

 Flexmaster

 Round passive tips
 High percentage of instrument fractures
 Extended Working time
 Increased risk of transportation

OOOOE 101:807,2006


 Protaper (progressive Race (Reamer with
taper) Alternating Cutting Edges)
 Modified K Type file with  utilizes an “alternating
sharp cutting edges and helical design” that
no radial lands: Stable reduces rotational torque
core sufficient flexibility by using spiraled and non
 Wide canals insufficiently spiraled portions along
prepared the working length
 prevent threading or
blocking effect

IEJ 36:86,2003/OOOOE 101:807,2006

• Mtwo
• S shaped cross sectional design
• Positive rake angle with 2 cutting edges
• Increasing pitch length
• Prepared curved canals rapidly
• Respected original canal curvature well
• Safe to use
• Remained better centered
than K3 and Race

IEJ,39;196,2006

Physical and Chemical
properties of NiTi
• Instruments
Heat, probably during sterilization cycles could
even restore the molecular structure of NiTi
(Nickel Titanium instruments: Applications in
endodontics)
• Sterilization procedures are safe and produced
a significant increase in fatigue resistance of the
instruments (IEJ 39,709;2006)
• Cryogenic treatment resulted in microhardness
but this increase was not detectable
clinically(IEJ,38,364,2005)
• Linear deforming forces shunted into stepwise
transformation from austenitic to martensitic
form-leads www.indiandentalacademy.com of 7%
to elastic deformation

Physical and Chemical
properties of NiTi
•
Instruments modes:
Instruments break in 2 distinct
 Torsional
 Flexural
• NiTi can withstand several hundred
flexural cycles before they fracture
• Torque depends on contact area and axial
pressure
• Crown down approach is recommended to
prevent taper lock
IEJ 35:379,2002/IEJ 32:24,1999/IEJ 34:471,2001

Cleaning reagents, Devices and
Indicators
• Ideal irrigant
 Kills bacteria and inactivates endotoxins
 Dissolves necrotic tissue
 Lubricates the canal
 Removes the smear layer
 Does not irritate healthy tissues

IEJ 36:538,2001/JoE32;5;2006


Sodium Hypochlorite
• Effective against Enterococcus, Actinomyces
and Candida organisms
• Various concentrations range from 0.5% to
5.25%
• 0.25% NaOCl kills Enterococcus Faecalis in 15
mins in infected dentin blocks
• 1% NaOCl kill Candida Albicans in 1 hour
• Lower concentrations dissolve mainly necrotic
tissue
• Higher concentrations allow better tissue
dissolution but dissolves both necrotic and vital
tissue
JoE;32,5;2006/JoE16:580,1990/IEJ 34:429,2001

Sodium Hypochlorite
• To increase the efficacy of NaOCl

 Lower the pH
 Increase the temperature
 Ultrasonic activation of sodium
hypochlorite

JoE 32;5;2006/OOOOE 94;76:2002

Chlorhexidine
• Broad spectrum Antibiotic
• Its use as an endodontic irrigant is based on its
 substantivity
 Binding to Hydroxyapatite
 Long lasting antimicrobial effect
• 2% conc used as irrigant
• Unable to dissolve necrotic tissue
• Less effective of gram negative than on gram
positive

JoE 32;5:2006

Chlorhexidine
• CHX + Ca(OH)2 show strong antibacterial
activity against obligate anaerobes
• CHX did not affect the alkalinity of Ca(OH) 2
• CHX useful as a final irrigant

JoE 32;5:2006


Iodine Potassium Iodide
• IKI kills a wide spectrum of micro
organisms
• Low toxicity
• Acts as an oxidising agent against
sulfhydryl groups of bacterial enzymes
cleaving disulfide bonds
• Combination with CHX kills Ca(OH)2
resistant bacteria more effectively
• Possible allergic reaction

M T A D
• Mixture of Tetracycline isomer (doxycycline),
Acid (citric acid), Detergent (tween 80)
• Removes smear layer
• More effective in apical third than EDTA +
NaOCl
• Less destructive to tooth structure than EDTA
when used as final irrigant

JoE 29;3,2003

E D T A
• Forms stable calcium complex with dentin
mud, smear layer and calcific deposits and
prevent apical blockage
• Negotiating narrow, tortuous canals,
calcified canals and to establish patency
• Chelators detach biofilms adhering to root
canal walls

JoE 32;5:2006


E D T A
• Calcium binding releases protons and EDTA
loses efficiency in acidic environment
• Effervescence or bubbling effect
• EDTA reduce available chlorine in NaOCl
• So, EDTA should not be mixed with NaOCl
• Hydroxyethylidene bisphosphonate (Etidronate)
decalcifying agent – Alternative to EDTA as it
shows less interference with sodium
hypochlorite
JoE 32;5:2006

Other Irrigants used
• Calcium Hydroxide (requires prolonged
exposure)

• Hydrogen Peroxide

• Salvizol (N1-decamethylene- bis-4-
aminoquinaldinium diacetate)

• Advocated use of 0.5% CHX and NaOCl as
irrigant can overcome effect of dentin dust on
conventional medicaments

Suggested Irrigation
Regimen
• Hypochlorite solution should be employed
throughout instrumentation without altering it
with EDTA. Canals should always be filled with
Naocl. This will increase the working time of
irrigant and cutting efficiency of hand
instruments is increased (JOE 1990, 16 418-22) and
torsional load on rotary NiTi instruments is
improved (IEJ 2005, 38, 223-29)
• Between instruments copious irrigation with
NaOCl recommended

Suggested Irrigation
Regimen [continued]
• Once shaping is completed canals can be thoroughly
rinse with EDTA for about 1 min. Prolonged exposure
with EDTA may weaken the root dentin (JOE 2002, 28, 17)
 After removing smear layer final rinse with antiseptic
solution appears beneficial. The choice of final irrigant
depends upon the next treatment step.
 If intervisit dressing is planned like calcium hydroxide,
the final rinse should be Naocl as these chemicals are
perfectly complementary (JOE 1998, 24, 326).
 If the canal walls are perceived to be clean of debris and
plan is to fill the root canal, then CHX appears to be
most promising agent to be used as a final irrigant.
(OOOE 1980, 49, 455)

Alternative concepts
• Use of Laser light
• Electrochemically activated water
• Ozone gas infiltration

None of these approaches can match NaOCl

• Reducing surface tension of the solutions may
increase the penetration into dentinal tubules

JoE 32;5:2006

Indicators
• Ruddle Solution/Visualisation Endogram
 5% NaOCl
 Hypaque
 17% EDTA
• Clinicians use Endograms to visualize
microanatomy, verify the shape and
monitor remaining root canal thickness
• Visualising caries, certain fractures,
missed canals and leaking restorations

Ultrasonics
• Ultrasonics use sound as an energy source resulting in a
three dimensional activation of the file
• Alternating attractive and repulsive forces between the
plates affect the mechanical vibratory movements, which
are then transferred to the instrument

• Ultrasonics are available as two designs, either
• Piezoelectrical
• Magnetostrictive

• Endosonic ultrasonic synergistic system is a term
coined to describe combined use of ultrasonics in
instrumentation and irrigation

Ultrasonics
• Druttman and Stock pointed out, "with the
ultrasonic method, results depended on
irrigation time. “The cleanest canals are
achieved by irrigating with ultrasonics and
sodium hypochlorite for 3 minutes after the canal
has been totally prepared ” (IEJ 1989, 20, 233)
• James O. Johnson found that 2% CHX was
significantly superior to 5.25% NaOCl with
irrigation alone and with final passive ultrasonic
activation (JOE 2003, 29, NO 9).

Ultrasonics
• Guy's Hospital in London pointed out that acoustic streaming
"depends on free displacement amplitude of the file" and that
the vibrating file is "dampened" in its action by the restraining
walls of the canal
• The Guy's Hospital group found that the smaller files
generated greater acoustic streaming and hence much
cleaner canals.
• At Guy's Hospital, another interesting phenomenon was
discovered about ultrasonic canal preparation that ultrasonics
alone actually increased the viable counts of bacteria in
simulated root canals. This was felt to be caused by the lack
of cavitation and the dispersal effects of the bacteria by
acoustic streaming. On substitution of sodium hypochlorite
(2.5%) for water, however, all of the bacteria were killed,
proving once again the importance of using an irrigating
solution with bactericidal properties
JOE 1987, 13, 93/ JOE 1987, 13, 490

Sonics
• Sonic systems uses vibration in audible
frequency range for activation of endodontic files

• Three sonic files used are Rispisonic, shaper
sonic, Trio sonic

• When loaded in canal produces longitudinal, up
and down motion

• Disadvantanges include perforations,
transportation

Sonics
• Dummer et al the Shaper Sonic files widened the canals
more effectively than the Rispi Sonic files, whilst the Trio
Sonic files were particularly ineffective
• At the University of Minnesota, the ultrasonic units were
again tested against the sonic unit. The researchers
found the Micro Mega Sonic to be better as they were
the fastest in preparation time and caused the "least
amount of straightening of the canals.
• The sonic technique extruded the least and hand
instrumentation the most debris. Ultrasonic was halfway
between.

IEJ 1989, 22, 211/ JOE 1989, 15, 235


Position of the apical
foramen
• Traditional treatment has held that canal
preparation and subsequent obturation should
terminate at the apical constriction (CDJ)
• Some advocated
terminating the
preparation 0.5 to
1mm short in necrotic
cases and 2mm short
in irreversible pulpitis

IEJ31;3941998/OOOOE89;99,200
0

Factors related to
preparation length

• Use of a patency file

• Apical width


Patency File
• Small K File (#10 size or #15 size) that is passed
through the foramen
• Suggested for most rotary techniques
• Remove accumulated debris and help maintain
working length
• An in vitro study suggested that risk of
innoculation was minimal when canals were
filled with NaOCl
• Clinical experience suggests this technique

JoE 30:92,2004

Apical Width
• Position of apical constriction and diameter is
difficult to assess clinically
• Some have recommended gauging canal
diameters by passing a series of fine files until
one fits snugly-likely to result in under estimation
of the diameter
• Initial canal size determines the desired final
apical diameter
• Ongoing debate b/w smaller or larger apical
preparations


Narrow Apical
preparations
• Benefits
 Minimal risk of canal transportation, extrusion of
irrigants, or extrusion of filling material
 Can be combined with tapered preparation to
counteract drawbacks
• Drawbacks
 Little removal of infected dentin
 Apical rinsing effect is questionable
 Possibly compromised disinfection during inter-
appointment medication
 Not ideal for Lateral condensation

Wide Apical preparations
• Benefits
• Removal of infected dentin
• Access of irrigants and medications in
apical third of root canal
• Drawbacks
• Risk of preparation errors and of extrusion
of irrigants and filling material
• Not ideal for thermoplastic obturation

• Despite the disagreement it appears that
the root canal preparation

• should be confined to the canal space
• should be sufficiently wide
• should incorporate the original root canal
cross sections

IEJ 36:740,2000

Canal Preparation
Techniques
• Various instrumentation techniques
developed for Hand and Rotary
instruments
• Shape of the Access cavity is the pre
requisite that must be optimised before
any canal preparation


Techniques for Canal
Instrumentation

• Traditional step back technique
• Crown down technique
• Apical widening
• Balanced force technique
• Hybrid technique
• 8 Step Method


Step Back/Telescopic
technique
• Traditional cleaning and shaping strategy
• Initial preparation of the apical third of the root
canal system followed by various flaring
techniques
• Apical to coronal preparation
• Cuicchi B et al evaluated the curved canal shape
using filing and rotational instrumentation
technique and stated that step back shaping
consistently presented the best taper and stop
design

IEJ 1990, 23, 139

Step Back/Telescopic
• technique
Determine working
length
• Serially develop an
apical stop
• Step back
preparation by
shortening the
length of the file
and increasing the
file sizes
• Flaring technique

Crown Down/Step down
technique
• Most rotary techniques require a crown down
approach
• Minimizes torsional loads
• Reduce risk of instrument fracture
• Minimizes the extrusion of necrotic debris
periapically
• Facilitates better cleaning
• Reduces canal curvature
• Eases instrument penetration
• Increases apical tactile awareness
DCNA 48;183,2004

technique
• Step apically by using
a series of files while
decreasing instrument
size or instrument
taper
• Next smaller file will
perform its cutting
action deeper leaving
the engagement
surface of each
instrument minimal

technique


Crown Down Pressureless
technique
• Similar to crown down concept
• Rotate straight files 2 times in a clockwise
direction sequentially from larger to smaller
sizes until a depth of 16mm is reached
• Passively use GG or orifice shapers
• Establish a provisional WL 3mm short of
radiographic apex
• Rotate straight files again 2 times from larger to
smaller sizes until WL is achieved
• Complete crown down preparation with a size 2
times larger than the first file

Balanced Force technique
• Roane et al described this technique
1. Using a Flex K file/Flex R file, the instrument is
rotated clockwise 90o using only light apical
pressure
2. Instrument is rotated counter clockwise 180-
270 degrees with sufficient apical pressure,
dentin shavings are removed with a
characteristic clicking sound
3. Similar to step 1;advances the instrument
apically
4. The file is removed with a prolonged clockwise
rotation

Hybrid Instrumentation
• Ideal preparation for the hybrid concept
takes its pattern from the definition by
Herbert Schilder and is slightly modified

“A three dimensional continuously tapering cone in
multiple planes with sufficient apical
enlargement preserving foramen position and
size”

Hybrid/Double Flared
technique
• All the basic techniques combined to eliminate
the short comings of individual instruments
• Use straight files progressively and passively in
a larger to smaller sequence
• Establish working length
• Continue to use larger to smaller files until full
WL is reached
• Serially prepare apical stop and apical
preparation to blend with the coronal step down
flare

Benefits of Hybrid
technique
• Instruments can be used in a manner that
promotes their individual strengths
• Hand instruments secure a patent glide
path
• Tapered rotary instruments enlarge
coronal canal areas
• Less tapered instruments allow additional
apical enlargement
DCNA48;195,2004

8 step technique
• Enlargement of coronal third with K/H
files/rotary/GG
• Working Length determination
• Enlargement of apical third with K files upto size
#25
• Enlargement of middle third to blend coronal
flare with apical preparation using reaming
motion with K files larger than MAF

IEJ 36,49,2003

Rotary Instrumentation
• Light speed instrumentation


• Profile instrumentation


• Protaper instrumentation



DCNA48;197,2004

Non Instrumentation
Technique
• Lussi and his associates at the University of Bern,
Switzerland, introduced devices to cleanse the root canal
"without the need of endodontic instrumentation." The first
device, reported in 1993, consisted of a "pump" that
inserted an irrigant into the canal, creating "bubbles" and
cavitation that loosened the debris. This pressure action
was followed by a negative pressure (suction) that
removed the debris: "The irrigant fluid was injected
through the outer tube while the reflux occurred through
the inner tube.

JOE 1993, 19, 549

Non Instrumentation
•
Technique the device
More recently, they have improved
and reported that the "smaller new machine
produced equivalent or better cleanliness results
in the root canal system using significantly less
irrigant (NaOCl). This cleanses the canal but, of
course, does nothing to shape the canal.


Laser assisted Canal
preparation
• Levy G et al -the Nd:YAG, in combination with
hand filing, is able to produce a cleaner root
canal with a general absence of smear layer
• Takeda et al - root canal walls irradiated by the
Erbium:YAG laser were free of debris, the smear
layer was removed, and the dentinal tubules
were opened
• Er:YAG Laser proved more effective than Co2
laser, NaOCl and EDTA irrigation regimens


CONCLUSION
• Clinically, it is important to envisage the shaping
procedure extending beyond antimicrobial
efficacy
• Although successful therapy depends on many
factors, the most important steps is canal
preparation as it determines the subsequent
procedures, includes mechanical debridement ,
creation of space for medicament delivery and
optimised canal geometries for adequate
obturation.

EVIDENCE-BASED APPROACH TO ROOT CANAL CLEANING AND SHAPING / /certified fixed orthodontic courses by Indian dental academy

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