Removal of Resin-based Root Canal Filling Materials with K3 Rotary Instruments: Relative Efficacy for Different Combinations of Filling Materials

Article (PDF Available)inDental Materials Journal 27(1):75-80 · February 2008with84 Reads
DOI: 10.4012/dmj.27.75 · Source: PubMed
Abstract
Removal of resin-based root canal filling materials may cause serious problems during root canal retreatment. This study compared the working time and amount of canal enlargement when different resin-based root canal filling materials were removed with K3 rotary instruments with or without heat-softening using System B. Root canal sealer/filling point combinations tested were Epiphany/Resilon, SuperBond/Resilon, SuperBond/gutta-percha, and Canals N/gutta-percha. The materials were filled into simulated curved resin canals and removed with K3 instruments in a standardized crown-down procedure. In terms of working time, Epiphany/Resilon required a significantly longer working time than the others. However, heat application with System B significantly reduced the working time for the removal of Epiphany/Resilon. In terms of canal enlargement, there were no significant differences among the tested groups as determined with digital morphometry. It was thus concluded that Epiphany removal with K3 rotary instruments might result in extended working time, but which could be reduced with heat-softening using System B.
Dental Materials Journal 27(1)7580, 2008
Removal of Resin-based Root Canal Filling Materials with K3 Rotary Instruments:
Relative Efcacy for Different Combinations of Filling Materials
Naoyuki IIZUKA, Shoji TAKENAKA, Yoshimi SHIGETANI and Takashi OKIJI
Division of Cariology, Operative Dentistry and Endodontics, Department of Oral Health Sciences, Niigata University
Graduate School of Medical and Dental Sciences, 2-5274, Gakko-cho-dori, Chuo-ku, Niigata 951-8514, Japan
Corresponding author, Naoyuki IIZUKA; E-mail: iizuka@dent.niigata-u.ac.jp
Received July 4, 2007/Accepted August 16, 2007
                                                         
Removal of resin-based root canal lling materials may cause serious problems during root canal retreatment. This study
compared the working time and amount of canal enlargement when different resin-based root canal lling materials were
removed with K3 rotary instruments with or without heat-softening using System B. Root canal sealer/lling point com-
binations tested were Epiphany/Resilon, SuperBond/Resilon, SuperBond/gutta-percha, and Canals N/gutta-percha. The
materials were lled into simulated curved resin canals and removed with K3 instruments in a standardized crown-down
procedure. In terms of working time, Epiphany/Resilon required a signicantly longer working time than the others. How-
ever, heat application with System B signicantly reduced the working time for the removal of Epiphany/Resilon. In terms
of canal enlargement, there were no signicant differences among the tested groups as determined with digital morpho-
metry. It was thus concluded that Epiphany removal with K3 rotary instruments might result in extended working time,
but which could be reduced with heat-softening using System B.
Keywords: Resin-based root canal lling material, Ni-Ti rotary instrumentation, Root canal retreatment
                                                         
INTRODUCTION
A number of studies have assuredly shown that most
endodontic treatments yield a success rate of nearly
90
1)
. Nonetheless, failures still occur despite
meticulous treatment methods that meet high and
stringent standards
2)
. Besides iatrogenic factors
such as inadequate canal preparation/obturation and
procedural errors, other several causes are respon-
sible for these occasional failures. For example,
residual post-treatment root canal infection may
be inevitable in some cases due to the complexity
of root canal anatomy
2)
. Reinfection resulting from
coronal leakage is also regarded as a major contrib-
uting cause
3)
. In these cases, non-surgical root canal
retreatment may be required to re-disinfect the
canals and re-establish healthy periapical tissues
4)
.
The retreatment procedure requires the removal of
pre-existing root canal lling materials, followed by
chemomechanical reinstrumentation and relling of
canals.
  Presently, gutta-percha
in combination with
sealers
is the most commonly used material for
root canal lling. However, of late, various resin-
based root canal lling materials have been devel-
oped to establish a core-sealer-dentin continuum to
the end of preventing microleakage and improving
the fracture resistance of root-lled teeth
5,6)
. For
example, Resilon (Pentron, Wallingford, CT)
a
synthetic polymer-based core material
is used as
an alternative to gutta-percha. It has been claimed
that when Resilon was used in combination with
Epiphany sealer (a dual-curable resin composite
sealer; Pentron), a core-sealer-dentin continuum was
established due to the adhesive property of Epiph-
any sealer
5,6)
. Another newly developed resin-based
sealer is the SuperBond sealer (Sun Medical,
Moriyama, Japan). This is a modied preparation of
4-META MMA/TBB resin-based adhesive material,
which is reported to show high bond strength
7)
and
durable seal
8)
to root canal dentin.
  Retreatment of roots lled with resin-based
materials may cause serious problems due to the
difculty in removing the materials. Resilon can be
softened with chloroform. However, there are many
reservations and cytotoxicity concerns associated
with the use of this chemical owing to its carcinoge-
nicity and mutagenicity. As for Epiphany and Super-
Bond sealers, no effective and safe solvents have yet
been reported.
  Several studies have evaluated the efcacy of
different engine-driven nickel-titanium (Ni-Ti) le
systems in the removal of root canal lling materials,
whereby these systems promised reduced working
time
9-13)
. Removal of Epiphany/Resilon with Ni-Ti
rotary les has also been investigated
14-16)
, although
the efcacy of this method has not yet been fully
established. Against this background, this study
aimed to further investigate the applicability of Ni-
Ti rotary instruments in the removal of different
resin-based root canal lling materials. Simulated
curved canals in resin blocks, which are widely used
to evaluate the root canal shaping ability of different
instruments
17)
, were employed for the purpose of
standardization.
Removal of resin-based materials with K3 les76
MATERIALS AND METHODS
Canal preparation and lling
Simulated canals with a 30-degree curvature in resin
blocks (Zipperer, Munich, Germany; canal length
19
mm) were prepared with Ni-Ti instruments to a size
30/.06 taper by a single operator. Working length
was set at 18.5 mm and the canals were instru-
mented with ProTaper instruments (Dentsply
Maillefer, Ballaigues, Switzerland) to a 20/.07 taper
(SX to 9.0 mm followed by S1, S2, and F1 to the
working length), and then with K3 instruments
(SybronEndo, Orange, CA, USA; 25/.06 followed by
30/.06 to the working length). The les were rotated
at 300 rpm using a 20:1 reduction contra-angle
handpiece (Anthogyr. Sallanches, France) set in a
torque-controlled electric motor (ATR Tecnika,
Advanced Technology Research, Pistoia, Italy).
  After preparation, the canals were rinsed with
distilled water and desiccated with paper points.
They were then lled with a taper-matching, single-
cone technique using either Resilon or gutta-percha
points (Zipperer) of 30/.06 taper. Sealers used were
Epiphany sealer, SuperBond sealer, or Canals N (a
zinc oxide non-eugenol sealer; Showa Yakuhin Kako,
Tokyo, Japan). Table 1 shows the root canal lling
materials used in the present study. The specimens
were stored at 37 in 100 humidity for seven days
before removal.
Retreatment technique
Experimental groups consisted of Epiphany/Resilon,
SuperBond/Resilon, SuperBond/gutta-percha, and
Canals N/gutta-percha groups (n
10 each). Retreat-
ment was performed using K3 instruments until a
30/.06 instrument reached the working length. K3
Orice Openers (25/.12, 25/.10 and 25/.08) and
35/.06, 30/.06, and 25/.06 instruments, rotated at
300 rpm with an ATR Tecnika Endo motor, were
used sequentially to reach 13.5, 14.5, 15.5, 16.5, 17.5,
and 18.5 mm (working length) respectively. Finally,
30/.06 was used again for the nal shaping at the
full working length. A single operator performed
all the removal attempts in a blinded manner: each
canal was masked with an aluminum foil and ran-
domly assigned to each removal attempt. Canals
were constantly irrigated with distilled water using
a syringe with a 25-gage needle. For ve canals in
each group, approximately 0.1 ml of d-limonene-
based gutta-percha solvent (GP Solvent, Nishika,
Shimonoseki, Japan) was applied with every le
change. Files were discarded after usage in 10 canals.
Evaluation
The working time that elapsed until the last
instrument (30/.06) reached the working length,
Material Batch no. Main components Manufacturer
Core materials
Resilon (polyester-based lling
material)
07120484 polycaprolactone, glass llers,
bismuth oxychloride, barium
sulphate
Pentron Clinical Technologies,
Wallingford, USA
Gutta-percha points (gutta-
percha-based lling material)
  17696 gutta-percha, zinc oxide,
metal sulphates
Zipperer, Munich, Germany
Sealers
Epiphany sealer (dual curable
composite resin sealer)
BisGMA, ethoxylated Bis-
GMA, UDMA, hydrophilic
difunctional methacrylates,
calcium hydroxide, barium
sulphate, barium glass, bis-
muth oxychloride, silica
Pentron Clinical Technologies,
Wallingford, USA
SuperBond sealer (4-META
MMA/TBB resin sealer)
Monomer
Catalyst
Powder
KG6
KE52
4117
4-META, MMA
TBB
PMMA, zirconium oxide
Sun Medical Co., Moriyama,
Japan
Canals N (Zinc oxide non-
eugenol sealer)
Liquid
Powder
6054MT
6056RA
higher fatty acids
zinc oxide, rosin, barium sul-
phate, bismuth subcarbonate
Showa Yakuhin Kako Co.,
Tokyo, Japan
Table 1 Root canal lling materials used in the present study
IIZUKA et al. 77
not including the time for instrument changes and
irrigation, was measured with a stopwatch.
  The amount of canal area removed during
retreatment was assessed by digital morphometry.
Following initial root canal preparation and retreat-
ment, a red dye was injected into each canal and
digital images were taken using a digital camera
(Fine Pix S602, Fuji, Tokyo, Japan). Pre- and post-
retreatment images were then superimposed. The
number of pixels representing the area of canal walls
removed was thereby computed with an image
analysis software (WinROOF, Mitani, Fukui, Japan).
  Statistical analysis was performed with one-
way analysis of variance (ANOVA) with multiple
comparisons using Scheffes test.
  The frequency of procedural errors (le separa-
tion and ledge formation) was also recorded.
Use of System B
Heat was applied using a System B Heat Source
(Analytic Technology, Redmond, WA, USA), a device
used for warm vertical compaction of gutta-percha
18)
and also applied for removing gutta-percha and
Epiohany/Resilon
15)
. The effect of heat application
on working time was evaluated for Resilon-lled
canals. Epiphany/Resilon and SuperBond/Resilon
groups (n
14 each) were then subdivided into
System B/K3 and K3 (control) groups (n
7 each). In
K3 (control) group, retreatment was carried out with
K3 instruments as described above. In System B/K3
group, System B Heat Source with a Fine Buchanan
Plugger was activated at 150 and a power setting
of 10, and inserted into the canal to 13.5 mm. The
last four K3 instruments (35/.06, 30/.06, 25/.06,
and again 30/.06) were used as described above.
Working time durations for the coronal portion (by
means of Orice Openers or System B to reach 13.5
mm) and apical portion (by means of last four K3
instruments to reach the full working length) were
separately measured.
RESULTS
The use of GP Solvent did not signicantly
inuence the outcome in terms of both working
time (119.3±18.0 and 132.8±20.9 seconds for GP
Solvent-used and non-used groups respectively;
mean±SD) and canal morphology (6497.5±1391.9
and 7115.3±1780.3 pixels for GP Solvent-used and
non-used groups respectively; mean±SD). In light of
these data, pooled data were analyzed.
  As shown in Fig. 1, the Epiphany/Resilon
group required a signicantly longer working time
compared with the other groups. No signicant
differences were detected among SuperBond/Resilon,
SuperBond/gutta-percha, and Canals N/gutta-
percha groups.
  Morphometric analysis revealed that the canal
area was increased during removal. However, no
signicant inter-group differences were detected
when the areas were compared (Table 2).
  System B reduced the working time for the
coronal portion by 55.1 (34.0±8.76 vs. 15.3±3.28
seconds; mean±SD) and 60.0 (30.8±4.02 vs.
12.3±1.03 seconds; mean±SD) for Epiphany/Resilon
and SuperBond/Resilon groups respectively (p<0.05).
In the Epiphany/Resilon group, the working time
for the apical portion was also reduced signicantly
(p<0.05) following the use of System B (Fig. 2).
  In the 68 canals examined in this study, le
separation and ledge formation occurred in one and
three canals respectively. A 30/.06 instrument
separated in a canal of the Epiphany/Resilon group
when it reached the working length. As for ledge
formation, it occurred in Epiphany/Resilon (two
canals) and SuperBond/Resilon (one canal) groups.
Fig. 1 Working time for the removal of different root
canal lling materials using K3 instruments
(mean and SD; n
10 each). *: p<0.05.
Group Mean
SD
Epiphany/Resilon 7507.8 3023.2
SuperBond/Resilon 7195.0 3490.6
SuperBond/gutta-percha 4729.8 2875.9
Canals N/gutta-percha 9023.6 1442.8
Values are expressed as the number of pixels. N
10
each.
No signicant differences between groups; p<0.05, one-way
ANOVA.
Table 2 Canal areas removed during lling material
removal
Removal of resin-based materials with K3 les78
DISCUSSION
In this study, we aimed to examine the efcacy
of Ni-Ti rotary instruments in the retreatment of
canals lled with resin-based lling materials. To
this end, we evaluated the working time required for
negotiation (reinstrumentation to the original canal
size), the amount of canal walls removed during
retreatment, and the effect of heat application using
a System B Heat Source.
  Simulated curved canals in resin blocks were
used under strictly controlled laboratory conditions
in order to make a reliable comparison by
eliminating variables arising from variations in root
canal morphology. The taper-matching, single-cone
method was employed for root canal lling, which
might have created a homogeneous lling with a
relatively thin layer of sealer
19)
. Moreover, resin-
based sealers most likely adhered more strongly
to resin canal walls as compared with the dentin
surface of root canal wall. Taken together, the
present experimental conditions represented a highly
challenging situation where anearly ideal canal
wall-sealer-core monoblockshould be removed from
a curved canal. Under such challenging conditions,
undesirable instrument effects (le separation,
ledging, extended working time, etc.) could have
been exacerbated in the removal of resin-based
materials. However, we believed that with safety
issues as our utmost priority and concern, this
conservative approach of perhaps obtaining a below-
par efcacy of K3 instruments would be far more
expedient.
  The present results demonstrated that the
Epiphany/Resilon group required a signicantly
longer working time compared with all the other
groups (Fig. 1). Conversely, no differences were
detected among SuperBond/Resilon, SuperBond/
gutta-percha, and Canals N/gutta-percha groups.
Based on the results obtained, it might be interpreted
that Epiphany sealer required a longer working time
compared with SuperBond sealer and Canals N, and
that the removability of Resilon was comparable
to that of gutta-percha. Therefore, it seemed that
the physical strength of sealers was an important
factor inuencing these results. In particular,
Epiphany being a resin composite material most
probably exhibited higher surface hardness and
compressive strength compared with all the other
sealers tested. Consequently, it required a longer
working time for removal from the canal wall.
  On the other hand, less-than-ideal resin-dentin
adhesion may occur under clinical situations, which
may favor the removal of resin-based root canal
lling materials. There are several causes that
impair resin-dentin adhesion in the root canal
system, such as ineffective EDTA conditioning
in the deeper part of the canal wall
20)
, the use of
sodium hypochlorite that may adversely affect bond
strength
21,22)
, and the presence of uninstrumented
areas
23)
that may be unfavorable to adhesion. These
could explain, at least in part, why it has been
reported that Epiphany/Resilon showed lower
adhesive strength to dentin
24,25)
and was easier
to remove compared with gutta-percha and a
conventional epoxy resin sealer (AH Plus)
14-16)
.
  The present results might support the view
that K3 instruments were efcient in the removal
of gutta-percha
13)
and Resilon
14)
. Under the present
experimental conditions, it was nearly impossible to
remove Epiphany/Resilon and SuperBond/Resilon
using hand les (data not shown), therefore further
supporting the efciency of K3. Several studies
have demonstrated that different Ni-Ti rotary
systems required less working time compared with
hand instruments for removing gutta-percha
9-13)
and
Resilon
15)
, although opposite results have also been
presented
16,26)
. Rotary instruments may be efcient
in disintegrating core materials, since they may
effectively auger the materials following softening
with frictional heat. On the other hand, removal
with hand les may be dependent on the
practitioners ability to remove existing core
materials and is hence more technique-sensitive.
Fig. 2 Effect of heat application with System B on the
working time for the removal of the apical portion
of resin-based root canal lling materials using K3
instruments (mean and SD; n=7 each). *: p<0.05.
IIZUKA et al. 79
  This study showed that GP Solvent, which
is less effective than chloroform in dissolving
gutta-percha
27)
, was ineffective for the resin-based
materials tested. The effect of GP Solvent was not
evident even on gutta-percha, most probably because
removal was carried out quickly and thus the
working time was not sufcient for the solvent.
Thus, our data were not necessarily against the
use of solvents for gutta-percha removal, although
it seemed necessary to nd alternatives that are
applicable for resin-based root canal lling materials.
  The results of the present morphometric analy-
sis were in agreement with the nding that the canal
area increased after retreatment
28)
. The type of
lling material did not inuence the mean canal
area removed, suggesting that no particular material
led to overzealous root canal enlargement. However,
the occurrence of ledge formation suggested that
the canal centering ability of K3 instruments
was impaired due to obstruction by canal lling
materials. This agreed with the suggestion that
pre-existing gutta-percha may cause and/or
aggravate canal transportation
28,29)
.
  The present results seemed to support the
view that System B Heat Source was useful for the
gross removal of Resilon from the coronal portion
of the canal
15)
. It should be noted that the working
time for the negotiation of the remaining apical
segment also decreased signicantly following heat
application (Fig. 2). This was most likely due to
heat transmission to deeper parts, which might
have softened Resilon to a certain depth and thereby
contributed to quicker negotiation. In addition,
the lower melting point of Resilon compared with
gutta-percha might have also favored removal using
heat. Although the optimal temperature for Resilon
removal is not known, we set it at 150 as recom-
mended by the manufacturer for thermoplasticizing
Resilon during warm vertical compaction. It has
been reported that System B set at 200 caused
a root surface temperature rise of less than 10
during gutta-percha compaction
30)
, suggesting
that the heating procedure was not harmful to the
periodontal ligament.
  Although this study suggested the efcacy of
K3 instruments in removing resin-based root canal
lling materials, several issues remained to be fully
evaluated before routine usage can be recommended.
In particular, le separation remained a matter
of concern as indicated by previous studies
9,11,31)
.
This study also showed the occurrence of ledge
formation and le separation only in Resilon-
lled canals, although relatively low in frequency.
Preparation of aglide pathusing small hand
instruments in conjunction with heat and/or
appropriate solvents prior to the use of Ni-Ti
instruments may improve safety. Further, it seemed
apparent that rotary instruments alone were not
sufcient for the complete removal of root canal
lling materials, since a number of studies have
demonstrated the remnants of gutta-percha
9-15,26,31)
and Resilon
14-16)
on the canal wall. Subsequent hand
instrumentation after rotary instrumentation might
thus facilitate the thorough removal of residual
materials.
CONCLUSIONS
It was concluded that Epiphany removal with K3
rotary instruments might result in extended working
time, but which could be reduced with heat-softening
using System B. K3 rotary instrumentation might
be an efcient method for the removal of resin-based
root canal lling materials, although safety issues
remained to be fully evaluated before routine usage
for this purpose can be recommended.
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33: 361-366.
    • "In another study, Desadresanfar et al. [17] showed that the ProTaper system removes RS more efficiently than the Mtwo R system. In an evaluation of RS removal using K3 system with and without System B (physical technique-heat), Iizuka et al. [28] observed that the procedure time was longer with the standalone K3 system. In addition, they observed that the technique was more efficient when used in combination with System B. Therefore, this technique is indicated for removing RS from the obturated canals. "
    [Show abstract] [Hide abstract] ABSTRACT: Introduction: Retreatment of endodontically treated teeth is a challenge that requires complete removal of the previous filling material. Several techniques are indicated for this procedure. The present review tries to identify the most efficient method for extirpation of Resilon (RS) root fillings and to compare the speed and efficacy of RS and gutta-percha (GP) root filling removal. Methods and materials: Three trained evaluators conducted a search through three major databases (PubMed, Cochrane Library and Lilacs) over the articles published in the period from 2001 to 2014. The search keywords were Epiphany Sealer, Resilon, Retreatment and Removal Procedure. Results: Twelve articles were included in the final sample (three in vitro studies and nine randomized trials). Conclusion: The ProTaper (manual or rotatory) system in combination with chemical solvents is the most efficient method for removing Resilon root filling. Retreatment of Resilon is more rapid and associated with less remnants of debris.
    Full-text · Article · Nov 2015
    • "But one study showed that there were no significant differences between gutta-percha and Resilon regarding the time needed for removal.112,121 In relation to the instruments used for the removal of filling materials, it has been shown that rotary files with chloroform are more effective than rotary files with heat,110 K3 than Liberator files, 111 Gates-Glidden than system B116 and heat than K3.122 There were no significant differences between Mtwo, Twisted files, Protaper and R-Endo115 and Hedestrome files in terms of Resilon removal.118 "
    [Show abstract] [Hide abstract] ABSTRACT: Background and aims. An ideal root canal filling material should completely seal the entire root canal space and block communication between the root canal system and its surrounding tissues; it should also be nontoxic, noncarcinogenic, non-genotoxic, biocompatible, insoluble in tissue fluids and dimensionally stable. Bonding to dentin is a promising property, which can prevent leakage and improve the sealing ability of root canal filling materials. Resilon was developed and rec-ommended initially because the existing rootcanal filling materials did not bond to root canal dentin. Since its introduction in 2004, numerous reports have been published regarding various aspects of this material. The aim of this literature review is to present investigations regarding Resilon’s physical and chemical properties and leakage studies. Materials and methods. A review of the literature was performed by using electronic and hand searching methods for Resilon from May 2004 to April 2012. Results. There are many published reports regarding Resilon. The searchshowed that Resilon is composed of a parent polymer, polycaprolactone or Tone, which is a biodegradable aliphatic polyester, with filler particles consisting of bioactive glass, bismuth oxychloride and barium sulfate. It possesses some antibacterial and antifungal properties. It is a promising material for root canal filling. Despite the presence of numerous case reports and case series regarding these applications, there are few designed research studies on clinical applications of this material. Resilon has some drawbacks such as high cost. Conclusion. Resilon seals well and is a biocompatible material. However, more clinical studies are needed to confirm its efficacy compared with other materials.
    Full-text · Article · Aug 2013
    • "Commonly used sealers include zinc oxide–eugenol-based cements, glass-ionomer cements, resins and silicones. To remove the root filling materials, hand, rotary and ultrasonic instruments can be used (Friedman et al. 1992, 1993, Moshonov et al. 1994, Wolcott et al. 1999, Bramante & Betti 2000, Imura et al. 2000, Sae-Lim et al. 2000, Ferreira et al. 2001, Ezzie et al. 2006, Schirrmeister et al. 2006 a–d, Zmener et al. 2006, Barletta et al. 2007, Hassanloo et al. 2007, Hammad et al. 2008, Iizuka et al. 2008, Somma et al. 2008, Tasdemir et al. 2008a,b) with or without solvents or heat to facilitate the procedure (Tamse et al. 1986, Wilcox et al. 1987, Wolcott et al. 1999). Regardless of the retreatment technique and the materials removed, studies have invariably reported the presence of root filling residue on the canal walls (Wilcox et al. 1987, Friedman et al. 1992, 1993, Moshonov et al. 1994, Masiero & Barletta 2005, Hassanloo et al. 2007). "
    [Show abstract] [Hide abstract] ABSTRACT: Roggendorf MJ, Legner M, Ebert J, Fillery E, Frankenberger R, Friedman S. Micro-CT evaluation of residual material in canals filled with Activ GP or GuttaFlow following removal with NiTi instruments. International Endodontic Journal, 43, 200–209, 2010. Aim To assess the efficacy of removing Activ GP or GuttaFlow from canals using NiTi instruments. Methodology Root canals in 55 extracted pre-molars were prepared to apical size 40, 0.04 taper. The teeth were imaged with micro-CT, and 30 teeth selected that had consistent apical size and taper of the shaped canals. They were randomly assigned to root filling with either the glass-ionomer-based ActivGP system (n = 15) or the polyvinylsiloxane-based GuttaFlow system (n = 15). After 2 weeks, canals were retreated stepwise with size 40–50 EndoSequence 0.04 taper instruments. Micro-CT scans (8 μm) were taken after use of each instrument to detect root filling residue in the coronal, middle and apical segment, and the retreatment time recorded. Residue, expressed as percentage of canal surface area, was compared between groups with t-tests, and within groups with repeated measures anova and Bonferroni-adjusted pairwise comparisons. Retreatment time was analysed with one-way anova. Results The percentage of sealer residue-coated canal surface was consistently highest (P < 0.001) in the apical third of canals, and it did not differ significantly between the two root filling groups. Stepwise enlargement from size 40 to 50 significantly decreased the amount of sealer residue in both groups (P < 0.001). Retreatment time did not differ significantly between groups. Conclusions Both root fillings with ActivGP and GuttaFlow were removed with nickel-titanium rotary instruments. Enlargement of canals up to two sizes beyond the pre-retreatment size was necessary to minimize the amount of sealer remaining.
    Full-text · Article · Mar 2010
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