n

Shaping

Endodontic Canal Preparation:New Developments

Ove A. Peters, DMD MS PhDDiplomate, American Board of Endodontics

January 17, 2013Seattle WAWashington State Association of Endodontists

Shaping

§ Clinical goals! -!antimicrobial efficacy! -!avoid preparation errors

§ Mechanical goals! -!providing space for obturation! -!avoid instrument fracture

§ Where are we standing with this?! -! rotary instruments have brought very significant improvement over the last 2 decades

Shaping Goalsn What is new?

n NiTi properties

n Metallurgy

n Discussion

Shaping

”... the prepared canal should include the original canal; the apical

constriction should be maintained; the canal should end in an apical

narrowing; and the canal should be tapered from crown to apex.“

ESE Consensus Paper 2006

n

n

Shaping

H. Messer

n What is new?

n NiTi properties

n Metallurgy

n Discussion

Shaping

Paqué et al Int Endod J,44:148; 2011

§ Accessory anatomy blocked

Accumulated Debrisn What is new?

n NiTi properties

n Metallurgy

n Discussion

n

Shaping

Paqué et al Int Endod J,44:148; 2011

nsion Hard Tissue Debris§ Superimposition shows blocked areas in green§ Volume can be quantified

Shaping

Metzger et al, 2010

The Self-Adjusting Filen What is new?

n NiTi properties

n Metallurgy

n Discussion

n

Shaping

n

Peters et al, 2010

n

Shaping

n

n

Shaping

n

Peters & Paqué, 2011

Shaping

§ Wide canal space: most d roots, bicuspids! -! inadequate shape and insufficient cleaning

Greater Degree Of Difficultyn What is new?

n NiTi properties

n Metallurgy

n Discussion

n

Shaping

n

Paqué & Peters, 2011

n

Shaping

n

Siqueira et al, 2010

n

Shaping

n

n

Shaping

n The Wave One System

n

Shaping

Yared G (2008)

§ Aim! -! to describe a novel preparation technique using only two instruments

§ Summary-!the technique described begins with negotiation to working length with hand instrument to size .08

! -! the bulk of the shaping is done with a ProTaper F2 (tip size 25)- the ProTaper is oscillated in a ATR electric motor that is programmed to generate reciprocating movements- r.p.m. is set at 400, the angles of rotation are CW 144CCW 72- instrumentation proceeds with very light apical pressure

Canal preparation using only one Ni-Ti rotary instruments: preliminary

observations.

Int Endod J 41: 339-344

n

n

Shaping

§ Discussion! -! the technique presented appears to be effective and safe- the exact settings need to be confirmed and more research is needed

§ Results! -! several cases are presented where curved canals could be prepared with

just one hand and one rotary instruments

Yared G Int Endod J (2008)n

§ Engine-driven! - reciprocating in special motor! - 3 sizes, small (21.06), primary (25.08), large (40.08) - must be single use (plastic ring expands)

n

Shaping

n The Wave One System

n

Shaping

§ Material & Methods! -!20 maxillary molars had db and mb roots instrumented with ProTaper either in continuous rotation or reciprocation (CW140, CCW45 degrees) - micro CT data was acquired and processed for canal transportation assessment (curvature, volume, surface, SMI, in-plane shift - parametric statistics were performed

J Endod 2011, 37:1296-1300

n

Shaping

J Endod 2011, 37:1296-1300

Shaping

Preparation Quality

§ Clinical data! - currently no studies available but case reports and in vitro data is encouraging

§ Overall outcomes ! - no increased incidence or severity of errors

- prepared surface and debris similar

n Introduction

n Physiology

n Microbiology

n Regeneration

§ Conclusion! - Reciprocation is an “...attractive alternative method to prevent procedural errors during root canal shaping”

Baek, 2011

n

Shaping

n

n

Shaping

§ Material & Methods! -!90 curved canals in extracted teeth were carefully randomized - canals were prepared to final size #50 with NiTi hand files, MTwo or ProTaper following manufacturers’ recommendations - micro CT scans were acquired initially and after subsequent preparation steps - prepared perimeters and canal outlines were determined

J Endod 2011, 37:1580-1584

n

Shaping

J Endod 2011, 37:1580-1584

Sequential Enlargement

Shaping

Increased Apical Enlargement

§ Experimental data! - does not lead to more complete preparation but with

less flexible instruments may cause preparation errors

§ Intended to increase efficacy ! - circumferential dentin removal

- prepared canal surface

§ Clinical conclusion! - “...it may be recommended to keep the apical size of curved canals as minimal as possible provided that a sufficient irrigation is feasible.”

El Ayouti, 2011

n What is new?

n NiTi properties

n Metallurgy

n Discussion

n

Shaping

Crazy Root Canalsn

n

Shaping

n

Testarelli at al, 2011

n

Shaping

Martensitic Filesn

§ Bendable

100

Tem

pera

ture

[C]

residual deformation

n

Shaping

Heat Treatment after Machiningn

§ not treated § heat-treated (?)

prototypes, heat treated and controls, 2010

§ Surface topography

n

Shaping

J Endod 2011, 37:1293-1295

Shaping

Martensitic Alloys

§ Clinical data! - currently no studies available but case reports and in vitro data is interesting

§ Flexibility! - clearly greater than austentic initially

- under “normal” fatigue condition extended lifespan

Paqué, 2011

§ Conclusion! - need to reconsider fatigue testing norms - not clear how important fatigue is for single use

n What is new?

n NiTi properties

n Metallurgy

n Discussion

n

Shaping

Cyclic Fatigue [5mm radius, 90°]n

§ Effect of metal conformation on fatigue lifespan

prototypes, heat treated and controls, 2010

n

Shaping

n Blue™ File Technology§ New raw material! - the degree of shape memory is dependent on NiTi microstructure - this material promises to be much more fatigue resistant and more

Dentsply Tulsa Dental to be released

CuttingEfficienc

y of Conventiona

l and Martensiti

c

Nickel-Titanium

Instruments for C

oronal Flaring

RenataDorne

lles Morgental, DD

S, MS, PhD,*† Fabian

a VieiraVier-Pe

lisser, DDS, MS, PhD

,*

Patr!ıcia Maria Poli Ko

pper, DDS, MS, PhD

,‡ Jos!e Antonio

Poli deFiguei

redo, DDS, MS, PhD

,*

and Ove A.Peters,

DMD, MS, PhD†

Abstract

Introduction: T

his study aimed

at evaluating th

e influ-

ence of rotational sp

eed and numberof uses

on the

cuttingefficienc

y of 4 nickel-titanium

coronalflaring

instruments against

2 substrates, bov

ine dentin and

acrylic blocks.Methods:

BioRaCeBR0, Hy

Flex CM1,

ProFile OS#2, and

ProTaper Sx we

re usedin simulate

d

lateral action against

both substrates at 25

0 and 500

rpm up to 5 times, producing

5 notchesin each block.

Notch areas and

lengthswere me

asured under a s

tereo-

microscope, and

data were compared by using para-

metrictests (a = 0.05).

Results: Against

both

substrates, HyF

lex CM1 and ProFileOS#2 were the

most and the lea

st cutting efficie

nt instruments, r

espec-

tively (P< .05). Ag

ainst acrylic, are

a and length val

ues

at 500 rpm were significantl

y higherthan those at

250

rpm for all brands. A

gainst dentin, s

ignificant differ-

ences were dete

cted between 25

0 and 500 rpm for Hy-

Flex CM1 and Pro

Taper Sx(area) a

nd for BioRace B

R0,

HyFlexCM1, and ProTape

r Sx (length). Regardin

g

cuttingefficienc

y loss, area and length for notc

hes 1

and 2 (first notches) a

nd 4 and 5 (last notches) w

ere

similaragainst

acrylic.Against

dentin,length values

for notches 1 an

d 2 weresignifica

ntly higher than t

hose

for notches 4 an

d 5 in ProFile O

S#2 andProTape

r Sx. A

strong correlation was detected

betweenthe overall

resultsobtained

on acrylic and dentin for area and

length (P < .0001),although

furtheranalysis

showed

that data against

acrylic were a poor pre

dictor of data

againstdentin a

fter repeated use

. Conclusions: H

yFlex

CM1 was the most c

utting efficient in

strument in later

al

action.An increase

in rotational speed

improved the

cuttingefficienc

y. Resultsagainst

acrylicshowed

a high correlation to data against

dentin,but acry

lic

may not bea proper s

ubstratewhen the intention

is

to assess cutting

efficiency loss w

ith repeated use.

(J En-

dod 2013;-:e1–e5)

Key Words

Coronalflaring,

cutting efficiency, marte

nsitic nickel-tita

nium

The introduction o

f nickel-titanium

(NiTi) toendodon

tics (1)significa

ntly changed

the wayroot can

al preparation is

performed. NiTi

rotary instrumen

ts have enabled

clinicians to obta

in tapered prepar

ations with little

or no procedura

l errorseven in

curved canals (2

).

New instrument de

signs, surface, an

d alloy treatments

have been develop

ed over the

years. Thus, sever

al brands are ava

ilable onthe mark

et, and directions

of use for most of

them recommend a cro

wn-downapproac

h. A so-called cor

onal flaring proce

dure is typi-

cally performed b

y more tapered in

struments and is

claimedto be adv

antageous during

the cleaning and s

haping phase of th

e root canal treatm

ent (3).It is com

monly accepted

that suchinstrume

nts should act lat

erally, avoiding th

e dangerzone des

cribed by Abou-

Rass et al (4). Als

o, the crown-down

techniquemay de

crease fracture ri

sks by preventing

a large portion of

an instrument fro

m engagingroot den

tin (5).

NiTi rotary instru

ments should hav

e some desirable

mechanical prop

erties, such

as shaping ability,

flexibility, resistan

ce to breakage, an

d cuttingefficienc

y (6). Different

methodologies ha

ve beenused to e

valuate the cuttin

g efficiency of end

odonticinstru-

ments, such as weight l

oss analysis(7–9),

profilometry (10, 11

), andmicro–

computed tomogra

phy (6). Moreo

ver, several subs

trates have been

used for such

purpose: human

dentin (9), bovi

ne bone(6, 10–1

2), andacrylic o

r plasticblocks

(7, 8, 13–18).

It appears that t

here isno consens

us regarding the

most adequate

criteria to assess

cutting efficiency

of endodontic ins

truments. Howeve

r, in principle,

the quantification of mater

ial removed in a specific

time seems arational

way to

determine cutting

efficiency.

Despite the exten

sive literature, th

ere is a lack of in

formation about

the behavior

of NiTicoronal

flaring instrume

nts related to lateral c

utting action. Sev

eral design

factors may affect

cutting efficiency

of rotaryinstrume

nts (6),but the

influence of

rotational speed

and numberof uses

on this property ha

s yet tobe investiga

ted

further.Thus, th

e aims of this stu

dy wereas follow

s:

1. To compare th

e cuttingbehavior

of 4 NiTi rotary i

nstruments in lat

eral action

2. To compare 2

differentsubstrate

s

3. To analyzethe influ

ence ofrotationa

l speedand number

of usesin the cutti

ng

efficiency

From the *Departmen

t of Endodontics

, Schoolof Denti

stry, Pontifical Ca

tholic University

of Rio Grande d

o Sul, Porto Alegre,

Brazil;†Arthur A

. Dugoni School

of

Dentistry, Unive

rsity of the Pacifi

c, San Francisco,

California; and

‡Department of En

dodontics, Schoo

l of Dentistry, Fed

eral University of

Rio Grande do Su

l, Porto Alegre,

Brazil.Renata D

ornellesMorgenta

l was supported

by MEC/CAPES (Brazil

ian Federal Agen

cy for Support an

d Evaluation of G

raduateEducatio

n) as anexchang

e scholarship

at the University

of the Pacific, A

rthur A.Dugoni

School of Dentis

try.

Addressrequests

for reprints to Dr

Renata Dornelles

Morgental, Pontifi

cal Catholic Univ

ersity ofRio Gran

de do Sul – PUCR

S, Av. Ipiranga 6

681, Pr!edio 6, 9

0619-900

Porto Alegre, RS

, Brazil.E-mail a

ddress:remorge

ntal@hotmail.com

0099-2399/$ - s

ee frontmatter

Copyright ª 2013 Am

erican Associatio

n of Endodontist

s.

http://dx.doi.org/

10.1016/j.joen.2

013.08.016

Basic Research—Technolo

gy

JOE — Volume-, Numbe

r -, - 2013

Cutting Efficacy fo

r Coronal Flaring

1

n

Shaping

§ Cutting efficacy! -!was highest in martensitic instruments used in lateral action (orifice modification)

n

Shaping

The Vortex Systemn

Shaping

ProFile Vortex Rotariesn What is new?

n NiTi properties

n Metallurgy

n Discussion§ Sizing! -!similar to ProFile, .04 & .06 tapers, #15 to #50 tips! -!offers sizes for many cases and shapes

§ Benefits and limitations! -!supposedly more cutting efficient! -!M-wire may result in better fatigue resistance

§ Research! -!Vortex may be the successor to GT/ProFile - there is limited published research on this file

Rhodes et al 2011Gao et al 2010

n

Shaping

ProTaper Next

§ Clinical “feel”! -!brushing motion preferred! -! fairly safe instrument re.: breakage

§ Research data! - shaping potential good - not a minimal invasive instrument - fatigue-resistant, low torque when cutting apically

§ Clinical outcomes! -!no data at this point

n What is new?

n NiTi properties

n Metallurgy

n Discussion

n

Shaping

Shaping Assessmentn What is new?

n NiTi properties

n Metallurgy

n Discussion

n

Shaping

n What is new?

n NiTi properties

n Metallurgy

n Discussion

n

Shaping

Enlargement to #25, Paqué & Peters, unpublished

Example of CT Data

n

Shaping

Summary of CT Data

§ Minimal dentin thickness! -!0.60±0.18mm (X2), 0.55±0.17mm (X3)! -! initial dentin thickness ~ 1.0mm

§ Uninstrumented area! - 16.4±7.4%, range 8-29%, apical 23.2±10.7% (to X3) - very good values in small curved canals

Paqué & Peters, 2013 AAE Meeting

§ Canal transportation! -!70 to 120µm in apical and middle third

Paqué & Peters, unpublished

n What is new?

n NiTi properties

n Metallurgy

n Discussion

n

Shaping

Torque Testsn What is new?

n NiTi properties

n Metallurgy

n Discussion

In Vitro Assessment of T

orque and Force

Generated by

Novel ProTaper

Next Instrument

s duringSimulate

d Canal

Preparation

ErikaS.J. Per

eira, DDS, MS,*

† Rupinderpal

Singh,DDS,*

Ana Arias,DDS, P

hD,*

and Ove A.Peters,

DMD, MS, PhD*

Abstract

Introduction: T

he purpose of t

his study was to

assess

torque and force for simulated canal pr

eparation with

a new root canalinstrume

nt, ProTaper Next.

Methods:Six sets of ProTape

r Next Instruments

(X1–X5)were us

ed to prepare 36

artificialcanals. F

iles

were dividedinto 6 groups.

Different setting

s of rota-

tions per minute

(250, 300, and 3

50 rpm)and num

bers

of in-and-out m

ovements to rea

ch working leng

th (3 or

4 insertions [ins

]) were applied in

each group (250

rpm/

3 ins, 250 rpm/4

ins, 300rpm/3 in

s, 300 rpm/4 ins,

350

rpm/3 ins, and350 rpm/4 ins) by u

sing an automated

torque bench. Peak torques

(Ncm) as well a

s positive

and negativeforces (N) wer

e registered. Analy

sis of

varianceand Tuk

ey posthoc test

s were applied. P

relim-

inary data for angle and stationa

ry torqueat failur

e

were also obtainedand compare

d with peak torque

for eachinstrume

nt. Results: Si

gnificant differe

nces

in peak torque (P < .0001),positive

force (P < .002),

and negative for

ce (P < .0001) were foun

d for ProTaper

Next instrument

s overall. X2 sho

wed thehighest

torque

with allsettings

. X5 showed the

highestpositive

force

in all groups. X1 and X2 showed

the highest nega

tive

forces for all gro

ups except for

350 rpm/4 ins. Signifi-

cantly lower torque(P < .0001)

and positiveforce

(P < .007) were mea

sured in the group 350 rpm/4 ins

for all instruments except

for X4. In contrast, X1

showeda significa

ntly lower negative

force for 350

rpm/4 ins. Torque at failure

according to America

n

Dental Associatio

n no. 28/ISO 36030-1

was lower for

X1, X2,and X3 than torque

during simulated canal

preparation (P < .0001).

Conclusions: Under

the

conditions of this

study, using ProTape

r Next at 350

rpm and with 4 in-and-out moveme

nts resultedin

lowestlevels of peak

torque as well aspositive

and

negativeforces. (

J Endod2013;-

:1–5)

Key Words

Nickel-titanium,

ProTaper Next, t

orque, simulated

preparation

Nickel-titanium (NiTi) ro

tary instruments a

re increasingly us

ed in root canal p

rep-

aration.Developm

ent continues to

design rotaries t

hat render shapi

ng not only

easier and faster

but arealso mo

re likelyto lead t

o improved outc

omes, compared

with stainless ste

el handinstrume

nts (1).However

, despiteincrease

d flexibility and

torsional strengt

h compared with

stainlesssteel ins

truments(2), NiT

i rotaryinstru-

ments still seem

to have arisk of fr

acture inthe clini

cal situation (3,

4).

Failure modes of N

iTi instruments ha

ve beenstudied e

xtensively (3–9).

Flexural

fatigue iscaused b

y repetitive comp

ressive and tensil

e stresses acting o

n outer fibers of

a file rotating in a

curved canal; tor

sional failure occ

urs whenthe tip o

f the instrument

binds, but the sh

ank of the file con

tinues torotate (3

). Shearfracture

of the material

then occurs when

the maximum strength

of the material is

exceeded(7).

The torque gener

ated by arotating

instrument durin

g root canal instr

umentation

dependson the c

ontact area betwe

en the file and th

e canal walls, the

appliedapical

force, instrumen

t diameter, and

preoperative canal vo

lume (10–12). In turn,

mechanical prop

erties ofendodon

tic instruments ar

e affected by a v

ariety offactors

such as size, taper, desi

gn, alloy chemica

l composition, a

nd thermomechanica

l

processes applied

during manufactu

ring (13–15).

It is believed that

there is astrong p

ositive correlation

betweenthe maxi

mum tor-

que an instrumen

t can withstand a

nd its diameter (1

2, 16). It has also

been suggested

that the cross-sec

tional shape of in

struments affects

the stress distribu

tion pattern and

thus their torsion

al resistance (17,

18). Moreover, fl

exural fatigue dev

eloped during

curvedroot can

al shaping may decrease

the torsional resista

nce of endodontic

instruments (12,

19–21).

ProTaper Next is

a novel set of rota

ry instruments th

at are designed w

ith variable

tapers and an off-

centeredrectangu

lar crosssection.

The set includes

5 shaping instru-

ments with overa

ll variable tapers

; at the tip, X1 is

#17/.04,X2 is #2

5/.06, X3is #30/

.075, X4is #40/.0

6, and X5 is #50

/.06. Allthe instr

uments are expec

ted passively to

follow the canal until th

e working length

(WL) isachieved

(22).

Such a singlelength techniqu

e possibly requir

es greater torsio

nal strength of

a given instrume

nt because of gre

ater contact with

the dentin walls

resultingin high

stresseson its en

tire length (11).

However, the syst

em featuresan off-ce

ntered rectan-

gular cross sectio

n, whichis intend

ed to reduce torsi

onal stress on the

instrument (22).

From the *Departmen

t of Endodontics,

University of the

Pacific, Arthur A.

Dugoni School of

Dentistry, San Fr

ancisco,Californ

ia; and†Restorat

ive Dentistry, Fac

ulty of

Dentistry, Unive

rsidadeFederal

de Minas Gerais, Belo

Horizonte, Minas Ger

ais, Brazil.

Supported by th

e Fundac~ao de A

mparo!a Pesqu

isa do Estado de

Minas Gerais (FAP

EMIG), BeloHorizont

e, MG, Brazil, and Pr

"o-Reitoria de Pe

squisa da Univer

sidade

Federalde Minas Ger

ais, BeloHorizont

e, MG, Brazil.

Addressrequests

for reprints to D

r Erika S. J. Pere

ira, Restorative D

entistry,Faculty

of Dentistry, Un

iversidade Fede

ral de Minas Ger

ais (UFMG), Av. P

res. Antonio

Carlos, 6627 – Campus

Pampulha, 31.27

0-901 Belo Hori

zonte, MG, Brazi

l. E-mailaddress:

erikajoviano@gmail.co

m

0099-2399/$ - s

ee frontmatter

Copyright ª 2013 Am

erican Associatio

n of Endodontist

s.

http://dx.doi.org/

10.1016/j.joen.2

013.07.014

Basic Research—Technolo

gy

JOE — Volume-, Numbe

r -, - 2013

Torqueand Forc

e with ProTaper

Next1

n

Shaping

§ First published research! -! torque during shaping is low: 1.5 - 3Ncm - higher RPM (300) is better than lower - torque at failure (ISO 3630) is lower than working torque

n

Shaping

0

0.5

1

1.5

2

2.5

3

X1 X2

Peak

Tor

que

[Ncm

]

X1

X2

0.35

0.82

Torque at failure[Ncm]

350 rpm

In-and-out movements

Simulated Canal Preparation

n

Shaping

0

1.5

3

4.5

6

X1 X2

Forc

e [N

]

Simulated Canal Preparation350 rpm

In-and-out movements

n

Shaping

Torque Data in Plastic Blocks

§ Torque during simulated canal preparation! -! range from 1.6 to 2.8Ncm for X1 to X5 - higher compared to fracture torque

§ Torque at failure (ISO3630-1)! - range from 0.35 to 2.87Ncm for X1 to X5 - similar or slightly less to ProTaper Universal

§ Handling parameters! -!comparing rpm, higher speed is better - comparing in-and-out movement, gentle is better

Pereira et al, 2013 AAE Meeting

n What is new?

n NiTi properties

n Metallurgy

n Discussion

n

Shaping

Fatigue Datan What is new?

n NiTi properties

n Metallurgy

n Discussion

Weibull plots, Nguyen J Endod accepeted

n

Shaping

Fatigue Data

Weibull plots, Nguyen J Endod accepeted

n What is new?

n NiTi properties

n Metallurgy

n Discussion

n

Shaping

n

Shaping

Assessment??

§ WS, #7, 06 § AZ, #14, 06

n What is new?

n NiTi properties

n Metallurgy

n Discussion

n

Shaping

Torque Explained§ Torque is lever length times force! -! rotational axis, point of force K

n What is new?

n NiTi properties

n Metallurgy

n Discussion

n

Shaping

Fatigue Explained§ Cyclic nature! -! repetitive action below elastic limit (high cycle)! -!sometimes beyond elastic limit (low cycle, <105)

n What is new?

n NiTi properties

n Metallurgy

n Discussion

n

Shaping

Fatigue Explained§ Southwest Airlines accident! -! “...jetliner had gone through about 39,000 cycles of pressurizing, generally a count of takeoffs and landings. Cracks can develop from the constant cycle of pressurizing for flight, then releasing the pressure.”

§ 2009 § 2011

n What is new?

n NiTi properties

n Metallurgy

n Discussion

Shaping

www.nitinol.com/nitinol-university/university-resources/

n

Shaping

Cyclic Fatigue in vivon

n

Shaping

Hooke’s Lawn

n

Shaping

Cyclic Fatigue in vitron

§ Effect of pseudoelasticity on fatigue lifespan?

FlexMaster, 5mm radius, 90°, Hübscher et al 2003

n

Shaping

Deformation Mechanisms

Elasticbehavior

Pseudoelasticbehavior

Force

Steel

NiTi

n What is new?

n NiTi properties

n Metallurgy

n Discussion

n

Shaping

n

n

Shaping

Nickel-Titanium Components§ austenite (B2)! -! hard, exists at room temperature for most endodontic instruments (with some exceptions)

§ martensite (B19’)! -! ductile, very flexible; trace amounts present in many endodontic instruments at room temperature

§ R-phase (R)! -! ductile, stress- or temperature induced, a pre- martensitic phase that provides shape memory

n What is new?

n NiTi properties

n Metallurgy

n Discussion

n

Shaping

Components§ austenite (also found in iron)! -!Austenite, also known as gamma phase iron, is a

metallic non-magnetic allotrope of iron. From about 900

to 1,400°C alpha iron undergoes a phase transition from

body-centered cubic (BCC) to the face-centered cubic

(FCC) configuration of gamma iron, also called

austenite.

wikipedia.org

n What is new?

n NiTi properties

n Metallurgy

n Discussion

n

Shaping

Components§ martensite (also found in iron, steel)

! -!Martensite, named after the German metallurgist

Adolf Martens (1850–1914), most commonly refers to a

very hard form of steel crystalline structure, but it can

also refer to any crystal structure that is formed by

diffusionless transformation.

wikipedia.org

- for NiTi martensite is in a monoclinic configuration

and more flexible than austenite

n What is new?

n NiTi properties

n Metallurgy

n Discussion

n

Shaping

Nickel-Titanium Components§ R-phase! -!The R-phase transformation is best thought of as a

second (or pre-) martensitic transformation that provides

a small, nearly hysteresis-free shape memory and

superelastic effect that exhibits virtually no degradation

during cycling.

- the name derives from the concept that the crystal

lattice is rhombohedral (may in fact be trigonal)

from Duerig et al 2010

n What is new?

n NiTi properties

n Metallurgy

n Discussion

n

Shaping

The R-Phase

From Otsuka & Ren 2005

n What is new?

n NiTi properties

n Metallurgy

n Discussion

n

Shaping

§ It is a bit obscure, even for a physicist! -!shows up through changes in electrical conductance, heat flow (total energy) or in stress-strain diagrams

from Duerig et al 2007

n What is new?

n NiTi properties

n Metallurgy

n Discussion

The R-Phase

n

Shaping

R-Phase Crystal Latticen

from Duerig et al 2010

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Shaping

Nickel-Titanium Properties

Aust

enite

[%]

Temperature

§ Temperature and strain-dependent

§ Transition of crystal phases

n What is new?

n NiTi properties

n Metallurgy

n Discussion

n

Shaping

Nickel-Titanium Properties§ Clinical application! -!martensitic phase (at low temperature) is flexible! -!higher flexibility ~ less cutting (=efficiency?)

Aust

enite

[%]

Temperature

n What is new?

n NiTi properties

n Metallurgy

n Discussion

n

Shaping

n NiTi Phase Transformation

exothermic

endothermic

From Miyai et al 2006

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Shaping

Transition Temperatures [C°]n

Ms Mf As Af

EndoWave 29 -3.2 -21 37Hero 642 6 -41 -38 9K3 9 -44 -41 5ProFile .06 23 -16 -21 30ProTaper 19 -10 -17 32

coolingcooling heatingheating

From Miyai et al 2006

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Shaping

n

Shaping

n NiTi Phase Transformation

auste

nite el

astic martensitic transformation

martensite elastic

martensite plastic

2%4% 2%

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Shaping

Appraisal I§ Thermal processing! -!drawn NiTi wire is work-hardened! -!heat treatment increases flexibility, fatigue resistance! -!downside: cutting ability is lower, high rpm required

§ Martensitic files (e.g., with shape memory)! -!current market share is small! -!martensitic files cannot utilize the pseudoelastic SIM transformation; rely on 2% recoverable strain

§ Hybrid files (e.g., segmental martensitic)! -!small market share! -!maybe a compromise but better?

n What is new?

n NiTi properties

n Metallurgy

n Discussion

Shaping

n What is new?

n NiTi properties

n Metallurgy

n Discussion

n

Shaping

What is here already...§ The alloy! -! thermal treatment: M-wire! -!surface treatment: electropolishing, PVD! -!cold treatment, nitrogen ion implantation! -!production process, twisting/stamping vs grinding

§ Intelligent motors! -! torque control is a standard feature! -!may detect individual instruments

§ Modified usage! -!glide path, single-patient use! -!change of sequence, hybrid techniques, etc.

n What is new?

n NiTi properties

n Metallurgy

n Discussion

Shaping

Summary of Current Data§ GTX! - fatigue resistance ↑(p<0.001) compared to stock NiTi

- similar torsional resistanceJohnson et al 2008

§ TF (Twisted File)! - flexibility ↑ compared to same size ProFiles (p<0.05)

- fatigue resistance: TF > K3 = GTX (different sizes)Gambarini et al 2008

§ Comparisons! - fatigue: EndoSequence>ProFile>TF> GTX; .06>.04

- difference not significant for TF vs. ProFile- Fatigue, angle at fracture: GT=GTX; .06>.04

- Multiple usage: GT, GT ↓ angle, torque at fractureKramkowski et al 2009

Kell et al 2009

Larsen et al 2009

n What is new?

n NiTi properties

n Metallurgy

n Discussion

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Shaping

§ Material & Methods! - 100 central maxillary incisors were prepared with either Reciproc, WaveOne, ProTaper or MTwo - teeth were embedded in Technovit, sectioned and observed under a stereomicroscope at 25x magnification - complete cracks were defined as “ a line extending from the root canal wall to the outer surface of the root” - the numbers of complete and incomplete cracks was compared by parametric statistics

Bürklein et al J Endod in press

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Shaping

Bürklein et al J Endod, 39:501;2013

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Comparison of 2

Canal Preparati

on Techniques

in the Induction

of Microcracks: A Pilot Stu

dy

with Cadaver M

andibles

Ana Arias,DDS, P

hD, Yoon H. Lee

, BS, Christin

e I. Peters, DM

D, Alan H. Glu

skin, DDS,

and Ove A.Peters,

DMD, MS, PhD

Abstract

Introduction: The purpose

of this pilot study in a

cadavermodel w

as to compare 2 d

ifferentshaping

tech-

niques regarding

the induction of

dentinalmicrocra

cks.

Methods:Three lower in

cisors from each of 6 adult

humancadaver

skulls were randomly distribut

ed into

3 groups: the con

trol group (CG, n

o instrumentation

), the

GT group (GT Profile hand files; Dentsply Tulsa Dental,

Tulsa, OK), and t

he WO group (WaveOne;

DentsplyTulsa

Dental).In the GT group, m

anual shaping in a crown-

down sequence w

ith GT Profile han

d files was perfo

rmed.

In the WO group, P

rimary WaveOne

files were used to

the

workinglength. T

eeth were separa

ted fromthe man

dibles

by careful remova

l of softtissue an

d bone under ma

gnifi-

cation. Roots were sectione

d horizontally at 3, 6,

and

9 mm from the apexusing a l

ow-speed saw. C

olor photo-

graphs at 2 magn

ifications(25! and 40!) were ob

tained.

Three blinded ex

aminersregistere

d the presence of

micro-

cracks (yes/no), e

xtension(incomp

lete/complete), d

irection

(buccolingual/me

siodistal), and location.

Data were

analyzedwith chi-

square tests at P

< .05. Results: Micro-

cracks were foun

d in 50%(CG and GT)

and 66%(WO) of

teeth at 3 mm, 16.6% (CG) and

33.3% (GT andWO) at

6 mm, and 16.6% in all 3 groups at 9 mm from the

apex. There were no significa

nt differences in the inci-

dence ofmicrocra

cks between all g

roups at3 (P = .8), 6

(P= .8), or 9mm (P= 1). All m

icrocracks were in

complete,

started at the pulpal wa

ll, and had a buccolingual dire

c-

tion. Conclusion

s: Within the limitations of this

pilot

study, arelations

hip betweenthe shaping

techniques

(GT handand WaveOne)

and theincidenc

e of microcracks

could not be sho

wn compared w

ith uninstrumente

d con-

trols. (J Endod 20

14;-:1–4)

Key Words

Cadavermandibl

e, GT hand, micr

ocracks,WaveOne

A frequentreason f

or toothloss afte

r root canal treat

ment isvertical r

oot fracture

(VRF) (1, 2). VR

Fs havebeen des

cribed innonendo

dontically treated

as well as

in teethafter roo

t canal preparatio

n (3, 4). Howeve

r, thereseems to

be disagreement

about the causes

of root fracture.

Historically, pulp

less teethwere co

nsideredto be

more brittle (5),

whereasmore re

cent studies repo

rted nosignifican

t differences in

moisturecontent (

6), strength and

stiffnessof dentin

(7, 8), nanomech

anical changes

to radicular intert

ubular dentin (9)

, or brittleness of

endodontically tre

ated teeth (10).

There isan incre

asing awareness

among clinicians

and patients abo

ut VRF that

calls forthe iden

tificationof the fa

ctors responsible

for fractures of

endodontically

treated teeth in or

der tomaximize t

ooth survival time

(11). Some studi

es have suggested

that factors direct

ly relatedto cleani

ng (12),shaping

(13), and filling (

14) procedures,

per se, could deb

ilitate root canal–

treated teeth.

The instrumenta

tion of root cana

ls alonesignifica

ntly reduced the

resistance of

teeth to fracturein in vitro studies

(13, 15). More

over, different p

reparation

techniques and file desi

gns havebeen identified

as beingresponsi

ble for different

degreesof dentin

al damage and th

e induction of m

icrocracks (16–

20). More recen

t

data suggested a

relationship betw

een thepresence

of dentinal defect

s and different

shapingmotions.

Althoughhand instrume

ntation techniques produ

ced significantly

less dentinal def

ects (20, 21), re

ciprocating files

that operate und

er the concept of

single-file prepar

ation were shown to create si

gnificantly more

incomplete dent

inal

cracks than full-s

equencerotary sy

stems (22).

It couldbe specu

lated that the use

of a single instru

ment, rather than

a seriesof

files, to perform the entir

e canal preparatio

n will generate m

ore stress (22). H

owever,

these experimen

ts usedextracted

teeth (15, 17–20, 22,

23) thatlacked bone an

d

periodontal ligam

ent (PDL) support

aroundthe teeth, th

us possiblyaltering

the

generated forces

(24).

In somestudies,

extractedteeth wer

e mounted in res

in blocks with sim

ulated PDL

in orderto mimic

bony sockets that

in turn may influe

nce theforces ap

plied during

endodontic proce

dures (18, 19, 2

1, 25).However

, no artificial ma

terial was found

to completely rep

roduce viscoelast

ic properties of t

he PDL,whereas

the PDLacts to

absorb much of th

e forcesintroduc

ed into teeth clin

ically (24).

A majorshortcom

ing of studies in

extractedteeth is t

hat specimens ca

n be sub-

jected toundue fo

rces during the e

xtractionprocedu

re and may displa

y microfractures

before being used

as samples in cra

ck studies. In add

ition, time since e

xtractionand the

lack of knowledge of

the previous circ

umstances of the

patient’sdentition

such as

occlusaldysfunct

ions or trauma c

ould alsoinfluenc

e the results (23)

. Therefore, the

aim of this study was

to compare the a

bility of 2different

shapingtechniqu

es in thein-

ductionof dentin

al microcracks in

an in situ cadave

r model.

Materialand Methods

Six adulthuman c

adaver skulls wit

h at least 3 lowe

r incisors were o

btained;the

final sample num

ber in each of the

3 groupswas n =

6. The time of de

mise was less

than 9 months pr

evious tothe comp

letion ofthe study

. The mean age o

f the tissue do-

nors was82.8 ("14.6) ye

ars. Twodigital ra

diographs with di

fferent angulation

s were

From the Department

of Endodontics, U

niversityof the P

a-

cific, Arthur A. Dugo

ni School of Dentistr

y, SanFrancisc

o,

California.

Addressrequests

for reprints to D

r Ana Arias, Univ

ersity of

the Pacific, Arth

ur A. Dugoni Sch

ool of Dentistry,

2155 Webster

St, San Francisco

, CA 94115. E-ma

il address: aa@ana-aria

s.com

0099-2399/$ - s

ee frontmatter

Copyright ª 2014 Am

erican Associatio

n of Endodontist

s.

http://dx.doi.org/

10.1016/j.joen.2

013.12.003

Basic Research—Technolo

gy

JOE — Volume-, Numbe

r -, - 2014

Microcracks in C

adaver Teeth

1

§ Microcracks are...! -!difficult to detect - associated with various events over the life of a tooth

Unshaped Control

Arias et al J Endod in press

Shaping

§ “More of the same” - refined instruments that are more efficient and safer - easier market penetration but limited innovation

§ Minimal invasive - limited enlargement and retained structural integrity - specific set of challenges

§ Not at all - specific non-instrumental techniques - alternatively, vital pulp therapy or regeneration

Preparation Possibilitiesn What is new?

n NiTi properties

n Metallurgy

n Discussion

n

Shaping

n What is new?

n NiTi properties

n Metallurgy

n Discussion

Questions so far?