Adaptation of injected thermoplasticized gutta-percha in the absence of smear layer

Abstract

The adaptation of thermoplasticized, injected gutta-percha to prepared dentine devoid of smear layer was examined with SEM. Findings indicate a penetration of gutta-percha into the patient dentinal tubules with or without root canal sealer. The clinical implications of these findings are discussed.

Full text

Internationa!
Endodontic
journal (i993)
26,
87-92
Adaptation of injected thermoplasticized gutta-percha in
the
ateence of the dentinal smear layer
J,
L.
GUTMANN
Department
of
Restorative Sciences, Baylor
College
of Dentistry. Dallas. Texas,
USA
Summary
The adaptation
of
thermoplasticized, injected gutta-
percha
to
prepared dentine devoid
of
smear layer
was
examined with SEM. Findings indicate
a
penetration
of
gutta-percha into
the
patent dentinal tubules with
or
without root canal sealer.
The
ctinical implicatioBS
of
these findings are discussed.
Keywords: gutta-percha, heat, scanning electron
microscopy, smear layer.
Introduction
The concept
of
root canal obturation with injectable
thermoplasticized gutta-percha was introduced by Yee
et
al.
(1977), Amajor impetus tor this development was the
need
to
ensure better adaptation of the root canal filling
material
to the
prepared canal wails. Further studies
by
Torebinejad
et
ai, (]978), Marlin etal (1981)
and
Budd
«
fl/,
(19 91) ha ve supported this achievement in that
the
thermoplasticized gutta-percha
was
shown
to
replicate
the intricacies
of the
root canal system
and
achieve
a
seal equal
to, if
not superior
to,
that produced
by
other
obturation methods (Michanowicz
&
Czonstkowsky
1984,
Czonstkowsky
ef
a],
1985, ElDeeb 1985, Evans&
Simon 1986. Mann
&
McWalter 1987),
Current methods
of
canal obturation using thermo-
plasticized gutta-percha
all
extol
the
virtues
of the
adaptation
of
the softened materials
to the
canal irregu-
larities. One technique has been shown
to
have dentinal
tubule penetration with
the
softened gutta-percha even
without
the use of
sealer (Michanowicz
et al.
1986).
When sealer
was
used,
no
penetration
was
evident.
Other plastic-type filling materials {pHEMA
and
silicone)
have also been shown
to
penetrate
the
dentinal tubuies
in
the
absence
of
root canal sealer (White
et
al. 1984),
However, this situation poses
a
dilemma,
as the use of
a
Correspondence: Professor ],
L,
Gutmann, Department
of
Restorative
Sciences, Baytor Coliege
of
Dentistry, 3302 Gaston Avenue, Dallas,
Texas 75246, USA,
Table 1, Suggested chemical methods
for
removing the dentinal smear
layer
Author
Goldman
etaf,
(1981)
Goldman ctai, (1982)
YamadartaA (19831
White
rt a/,
(1984)
Ciucchi eta/, (1989)
Gettlemeneta/, (1991)
Soiution
REDTA'
REDTA'
NaOCl
REDTA*
NaOCl
REDTA*
NaOCl
NaOCI
EDTAt
EDTAJ
NaOCl
17%
17%
5,25%
17%
5.25%
17%
5,25%
3%
15%
17%
5,25%
Amount
20 ml
10ml
10 ml
10ml
10ml
lOmi
10ml
1ml
2ml
—
*Roth Drug
Co,,
Chicago,
IL,
USA,
tLargal-Ultra: Septodont, Paris, France,
^Unknown source.
root canal sealer
has
been advocated
as
essential with
thermoplasticized gutta-percha
to
achieve
the
best
possible seal (ElDeeb
1985,
Evans
&
Simon
1986,
Skinner
&
ffimel 1987, Bradshaw et
d.
1989),
An additional dilemma
in
this issue is the ability of the
gutta-percha
to be
adapted intimately
to the
root canal
wall when
the
smear layer
is
present (Moodnik
et al.
1976,
White
et al.
1984).
The
presence
of the
smear
layer has been postulated
to be an
avenue
for
leakage of
microorganisms
and a
source
of
substrate
for
bactedai!
growth (Pashley
1984.
Pitt Ford
&
Roberts 1990).
A
further concern
is the
presence
of
viable bacteria which
may remain
in the
dentinal tubules
and use the
smear
for sustained growth
and
activity (Olgart
et al. 1974,
Brannstrom 1984).
Removal of varying degrees of dentinal smear layer
in
the root canal
has
been suggested
by
many authors
using combinations of solutions (Table 1), The effective-
ness
of
these solutions
has
been demonstrated
in the
exposure of ciean dentine
and
patent dentinal tubules.
87

88 /. L Gulmann
Ideally then, thorough canal cleaniog and shaping,
followed by removal of the smear layer, and subsequent
intimate adaptation of gutta-percha and sealer to the
dentinal wall would appear to be the goal of all iatra-
canal procedures. Realistically, however, the routine
achievement of this goal can be questioned, especially
with lateral condensation (Baumgardner
&
Krell 1990).
The purpose of this preliminary investigation was to
determine the ability of one of the newer thermoplastic
injection obturation techniques to enhance adaptation
of the softened gutta-percha to dentine, in the absence of
smear layer debris.
Materials and methods
Four recently extracted maxillarj' canines were accessed,
measured and prepared to a size 50 Master apical fUe
(Brasseler, Savannah, Georgia, USA), Each canal was
flared with Hedstrom
flies
(Brasseler) to enhance the taper
according to previously published guidelines (Gutmann
&
Dumsha 1987),
No
rotarj'
instruments were used.
All
four
teeth were copiously irrigated with 10-15 ml of 5,25%
sodium hypochlorite (NaOCl) during preparation, using a
Monoject endodontic syringe with a 2
3
gauge x 1,2
5
inch
ED needle (Sherwood Medical, St Louis, MO, USA),
Immediately prior to obturation, the teeth were flushed
with 3 mi of
a
17% solution of REDTA (disodium ethylene
dinitrilotetraacetatic acid buffered with 5
N
sodium
hydroxide; Roth Drug Co., Chicago, IL, USA) for 1 min,
foUoived by irrigation with 10 ml of NaOCl, Canals were
dried with paper points and two to three short blasts of
air, directed perpendicular to the canal orifice,
Sealapex (Kerr Manufacturing Co,, Romulus, MI,
USA) root canal sealer was placed in the canals in two
teeth using a plugger prefit loosely to the junction of the
apical and middle third of the canal. The teeth were
obturated ivi th injectable thermoplasticizedgutta-percha
(Obtura; Texceed Corp., Cosa
Mesa,
CA,
USA)
and vertical
condensation using size 8.5 and 9 Schilder pluggers
(Hu-Friedy, Chicago, IL, USA), The remaining two teeth
were obturated with thermoplasticized gutta-percha,
vertical condensation and no sealer.
After 24 h the teeth were placed in
5%
nitric acid until
a no, 11 scalpel blade could easily penetrate the dentine
to the core gutta-percha filling material (approximately
72 h). Each tooth was cut longitudinally with the
scalpel, split apart with a cotton forceps, and the segment
retaining the gutta-percha fill was dried and sputter
coated with gold (Denton DV-502 Sputter Coater;
Denton Vacuum, Cherry Hills, NJ, USA) for SEM
evaluation
(JEOL
JSM-35CF,
JEOL,
Peabody, MA, USA),
Fig, 1, Discrete penetration of softened gutta-percha into the patent
tubules in the form of
plugs.
Note the separation of the plugs suggesting
a decreased number of dentinal tubules in the apical portion of the
canal. No sealer used. siiM original magnification x
1
500.
Results
A number of observations concerning the morphology of
the root canal fillings can be made. Separate evaluations
were made for the apical, middle and coronal thirds of the
gutta-percha fill.
Apical third
(i) The softened gutta-percha, with or without sealer,
reproduced the intricacies of the canal walls in the
apical third. Greater irregularities were seen on the
gutta-percha surface when sealer was used, due to
the apparent streaking and discrete aggregation of
pooled sealer over the surface of the gutta-percha,
(ii)
A
few select areas (more coronally) exhibited discrete
penetration of gutta-percha into widely spaced,
patent dentinal tubules (Fig, 1),
Middle third
(i) The junction of the apical and middle thirds and
the bulk of the middle third of the gutta-percha
presented a wide variety of appearances, from con-
densation voids (Fig, 2), to voids due to junctional
weldsof gutta-percha
(Fig.
3),
to
fields
of gutta-percha
tubular plugs interlaced with smooth gutta-percha
surfaces (Fig. 4),
(ii) Gutta-percha penetration into the tubules, with
and without sealer, m'as abundantly evident (Figs 5
and 6),

Injected thermoplastidzed::'i^:ii-i -''.^h 89
I-
i;:fe....N'•
Fig, 2. Condensation void due to incomplete vertical movement of Fig, 4, Smooth surfaces of gutta-percha surrounded by fields of gutta-
gutta-percha. Note gutta-percha penetration of the dentinal tubules percha plugs, Sealer used,
SEM
original magnification x 66.
below the void, iower left. No sealer used,
."iEM
original magniiication
X
240.
Fig, J, Junctiona! void created during the folding and condensing of
gutta-percha. Depending 00 the thoroughness of condensation, these
areas will vary In size. No sealer used, SEM original magnification
X
200.
^v V;-'; ^^ ••
that sealer approximated the dentine surface and
penetrated the tubules (Fig, 9),
Coronal third
(i) This portion also exhibited fields of gutta-percha
plugs interspersed with the smooth surfaces of the
filling material, similar to that seen in the middle
third,
(ii) Gutta-percha without sealer evidenced deep pen-
etration of distinct individual plugs into the tubules
(Fig, 7). When sealer was used the plugs had more
of a matted effect, as seen in an older floor carpet
(Fig. 8), EveD with this appearance, it was evident
Discussion
Even though a complete apical and coronal seal of the
root canal is highly improbable with present materials
and techniques, close adaptation of the root canal core
material and sealer to the clean root canal wails
is
essen-
tial to achieve the best possible seal. Studies have shown
reduced levels of leakage when the smear layer has been
removed (Kennedy et al. 1986, Cergneux et al. 1987),
The intimate association of gutta-percha, sealer, dentin
and dentinal tubules shown in these specimens, reflects

90 J. L. Gutmann
»-'^'?^v.;rr••' •:' ..•.^' •,•.•.•• " :-r-^-J-t^-^^^^-
Fig. 6. Gutta-percha plugs showing discrete penetration into the Fig. 8. Entanglement of gutta-percha plugs and sealer,
SEM
original
tubules without the use of sealer,
SEM
original magnification x 940. magnification x 720.
Fig. 7. Discrete, lengthy gutta-percha plugs penetrating the coronal
tubules.
SEM
original magnification x 660.
e\'idence of this ideal when injected thermoplasticized
gutta-percha is condensed in the root canal system. The
ability to attain this degree of
filling
and approximation is
also highly dependent on the canal shape, absence of
smear layer and operator skill and expertise.
The variations in adaptation seen between the apical
portion and the remainder of the canal reflects the nature
of the softened gutta-percha and its response to the force
applied during condensation. The movement of gutta-
percha into the dentinal tubules would be primarily due
to a lateral condensation force, whereas areas of linear
irregularities would be more reflective of the vertical
movement of gutta-percha, coupled with a minimum, if
any, of lateral condensation force. In this respect then.
Fig. 9. Deep penetration of sealer inui tl;e
IU:>U[L'S
nn the oiul of ilk-
gutta-percha plugs.SKMoriginal tiii.gnili;aiiot! xAi:'.V>
the appearance at or near the apical third of dentinal
plugs would indicate the depth, degree and direction of
v'ertical condenser placement during obturation. On the
other hand, the minimization of tubule penetration in
the apical third may be due to lack of tubule patency in
various areas, as evidenced by the increase in sclerosis
(Kennedy et fli. 1986).
It is also highly possible that some areas devoid of
dentinal plugs were not completely free of a dentinal
smear layer, either due to ineffective irrigation methods
or the possibility of dentinal tubule orientation, which
would account for the dispersed smooth areas of
gutta-percha adaptation. The packing of the smear layer
into the tubules by the endodontic instruments and

Injected thermoplasticized gutta-percha
91
preparation technique
may
also have prevented
a
thorough cleaning and removal ofthe deep smear layer
(Maderetal. 1984). However, when examined, the other
half of the segmented teeth revealed the absence of smear
layer
debris.
Also Gettlemen
et a/.
(1991) have shown the
use
of
17% EDTA to be effective in smear layer removal
along the root canal
walls.
Likewise, Cengiz etal. {1990)
have shown that tubule orientation had
no
detectable
effect
on
the formation
or
removal
of
the smear layer
when
a
chelating agent was used with sodium hypo-
chlorite
as
irdgants. Finally. Mader et al. (1984) indi-
cated that the smear layer on the root canal walls was
friable and easily removed, even when packed against
the dentine and into the tubules.
It is also possible that the movement of sealer during
condensation assisted the flow of gutta-percha apically,
but prevented or moderated the movement ofthe softened
material into
the
dentinal tubules. This rationale was
expressed
by
Michanowicz
et al.
(1986).
as it was
thought that the backflow of sealer may have prevented
tubule penetration by the gutta-percha.
In
the present
study, minimal
(2
drops) sealer was used
to
coat
the
walls
in the
coronal two-thirds
of
the canal prior
to
injection of gutta-percha.
The use of only two samples per experimental group
should not detract from the anatomical findings
or
the
potential implications
of
these observations,
as
these
preliminary findings strongly suggest that further evalu-
ation is necessary. The movement of both gutta-percha
and sealer into the dentinal tubules
in
this study
is in
direct contrast
to the
findings
of
Michanowicz
et al.
(1986),
in
which gutta-percha
did not
penetrate
the
dentinal tubules
in
the presence
of
sealer. However,
a
different thermoplasticized injection system
was
used
and condensation was not performed.
In
addition,
the
nature
of
the sealer was different
as
was the operator
technique.
There
is no
attempt
in
this paper
to
imply that
the
adaptation seen in these few specimens will result in no
canal microleakage, as various authors have shown an
effective,
but not impervious seal, under similar exper-
imental conditions (ElDeeb 1985, Evans
&
Simon 1986,
Skinner & Himel 1987). However, what
is
implied
in
these findings is the need to clean and shape the canal
system properly, and that enhanced adaptation of root
canai fillings can
be
achieved with the removal of the
smear layer
and
obturation with injectable thermo-
plasticized gutta-percha. Further studies are warranted
to assess the capability of this achievement with newer
thermoplasticized techniques
and to
correlate these
findings with microleakage.
Conclusions
(1) Injectable thermoplasticized gutta-percha can repli-
cate the anatomy of the prepared dentine root canal
wall.
(2) Injectable thermoplasticized gutta-percha
can be
condensed into patent dentinal tubules with
or
without the presence of root canal sealer.
(3)
In the
samples evaluated, there
was a
higher
incidence of tubule penetration with gutta-percha in
the middle and coronal thirds ofthe canal.
References
BAUMGARUNER
KR.
KREU, KV
(1990) Ultrasonic condensation of gutta-
percha: an in vitro dye penetration and scanning microscopic study.
Journal
of
Endodontics
16, 25 3—9.
BRADSHAW
GG.
HALL
A,
EDMUNDS
DH (1989)
The
sealing ability
of injection-moulded thermoplasticized gutta-percha. International
Endodontic
journal 22, 17-20.
BRANNSTROM
M
(1984) Smear layer: pathological
and
treatment
considerations. Operfl£jVfftnti5(ri/|Supp!. 3). 35-42.
BuDD CS.
WELLER
RN.
KUULD
]C (1991)
A
comparison
ot
thermo-
plasticized injectable gutta-percha obturation techniques.
Journal
of
Endodontics
17. 260-4.
CENGIZ
T.
AKTENER
BO,
PISKIN
B
(19901 The effect
of
dentinal tubule
orientation on the removal of smear layer by root canal irrigants.
A
scanning electron microscopic study.
International
Endodontic jownal
23.163-71.
CERGNELX
M.
CIOCCHI
B.
DIETSCHI
JM. HOLZ
J (198
7)
The influence of the
smear layer on the sealing ability of canal obturation. International
Endodontic Journal
20, 228-32.
QuccHi
B.
KHETTABI
M,
HOLZ
j
(1986) The effectiveness
of
different
endodontic irrigation procedures on the removal of the smear layer:
a scanning electron microscopic study. International Endodontii:
Journal
22,
21-S.
CzoNSTKOwsKY M. MicHANOuicz A.
VAZQUEZ
fA (1985) Evaluation of an
injection of thermopiasticized low-temperature gutta-percha using
radioactive isotopes.
Journal
of
Endodontics
11, 71-4.
ELDEEB
ME (1985)
The
sealing ability
of
injection-molded thermo-
piasticized gutta-percha.
Journal ofEndodont!i:s
11, 84-6.
EVANS
JT.
SMON JHS
(1986) Evaluation of the apical seal produced by
injected thermoplasticized gutta-percha
in the
absence
of
smear
layer and root canal sealer.
Journal
of
Endodontics
12,101-7.
GETTLEMEN
BH.
MESSER
HH.
ELDEEB
ME
(1991) Adhesion
of
sealer
cements
to
dentin with
and
without
the
smear layer, journal of
Endodontics
17, IS-H).
GOLDMAN
M.
GOLDMAN
LB.
CAVALERI
R.
BOGIS
J.
SIIN
LIN
P (1982) The
efficacy
of
several endodontic irrigating solutions:
a
scanning
electron microscopic study: part 2. journal
oJ
Endodontics
8,487-92.
GOLDMAN
LB. GOLDMAN M.
KRDNMAN
JH.
SUN LIN
P (1981) The efficacy of
several irrigating solutions
for
endodontics:
a
scanning electron
microscopic study. Oral Surgery Oral Medicine Oral Pathology
52,
197-204.
GuTMANN JL.
DHMSHA
T
(1987) Cleaning and shaping the root canal
system. In: Cohen S. Bums
RC.
eds. Pathways
o/ihf
Pulp.
4th edn. St
Louis: CV Mosby. pp. 156-82.
KENNEDY WA. WALKER WA. GODGH
RW (1986) Smear layer removal
effects on apical leakage.
Journal
of
Endodontics
12,21-7.
MADER
CL.
BAUMGARTNEB
JC.
PETERS
DD
(1984) Scanning electron
microscopic investigation
of
the smear layer
on
root canal walls.
Joumsl of
Endodontics
10,477-83.

92
/. L
Gutmann
MANN SR, MCWALTGK
GM (19 8 7) Evaluation of apical seal aad placement
conOol in straight and curved canals obturated by laterally con-
densed and tbennopiastlcized gutta-j)«rcha, journal of
Erahdontics
13.10-17,
MAWJN
],
KRAKOW
AA,
DESILETS
RP,
GRON
P (1981) Clinical use of
iniection-molded tbermopiasticized gutta-percha
for
obturation of
the root canal ssratem:
a
preliminaiy report, loumal ofEndodontks
7,
277-81,
MiCHANOWicz A,
CHJNSTKOWSKY
M
(1984) Sealing properties
of an
injection-tfaernuqjtasticized tow-temperature (70°C) gutta-percha:
a
preliminary study,/oumaJo/Endotontics 10, 563-6,
MiCHANOWFCzAE,
CZONSTKOWSKYM,
PiESCoNP(1986)Low-tenq)erature
(70°C) injection gutta-percha:
a
scanning electron microscopic
investigation, journal of
Endodontics
12,64-7.
MooDNiK RM, DoRN
SO, FELDMAN MJ,
lEVEi].
BtMOSK
BG
(1976) Efficacy
of biomechanical instrumentation:
a
scanning microscopic study,
journal
<^
Endodontics
2,261-6,
OLGART
L,
&1ANNSTR0M
M,
JOHNSON
G
(1974) Invasitm
of
bacteria into
dentinal
tubules:
experiments in-vivo
and
in-vitro,
Ada
Odontologica
Scandanavica
32, 61-70,
FASHLEY OH
(1984) Smear
layer:
physiological considerations. Operative
Dtntetry (Supp!, 3), 13-29,
Pnr
FORD
TR,
ROBERTS
GJ (1990) Tissue response
to
glass ionomer
retrograde root
BlUngs.
International Bndodontic
/oumaf 23,233-8,
SKDwa RL, HiHEE, VT (1987) The sealing ability of iajecUon-molded
thennopiasticized gutta-percha with and without the use of sealers,
journal ofEr^odontics 13,315-7,
ToRABiNSAD M,
SKOBE Z, TROMBIY
PL,
KKAKOW
AA,
GRTO
P,
MARUN
J
(1978) Scanning electron microscoinc study of root canal obturation
using thennoplasticized gutta-percha, journal
of
Endodontics
4,
245-50.
WHITE RR, GOLDMAN M, SUN LBJ
P (1984) The influence ofthe smeared
layer upon dentinal tubule penetration by plastic Ming materials,
journal
of
EnMkmtks
10.
558-62,
YAMADA
RS,
ARMAS
A,
GOLDMAN
M,
SUN IJN
P (1983) A scanning
election microscopic comparison of a high volume final fiush with
severed Irrigating
solutions:
part 3, jourral of
Endodontics
9,13 7-42,
YEE
FS.
MARLIN
I,
KiiAKOW
AA.
GRON
P
(1977) Three-dimensional
obturation ofthe root canal using injection-molded, thermoplastlcized
dental gutta-percha, /ourraJ ofEndodontks 3,168-74.