Removal of resin-based root canal filling materials with K3 rotary instruments: relative efficacy for different combinations of filling materials.
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.
- SourceAvailable from: Ki-Hyun Kim[Show abstract] [Hide abstract]
ABSTRACT: In this study, the emission characteristics of various pollutants (e.g., reduced sulfur compounds (RSCs), aldehydes, volatile organic compounds (VOCs), and organic acids) were investigated in relation to 3 food types (including cabbage, clam, and coffee seeds) and 2 cooking methods (between mild and harsh treatments). The results indicated the strongest emissions from the roasted coffee seeds out of all 6 sample types. Among the pollutant types, the maximum emissions generally came from RSCs followed by aldehydes and acids. Among VOCs, toluene and methyl ethyl ketone were emitted most prominently. As most of these pollutants also represent key odorants, their concentrations are compared through a conversion into odor intensity (OI); the results showed the RSC group as the key odorants along with aldehydes and organic acid compounds. If the sum of odor intensity (SOI) is derived for each sample, they were in the descending order: roasting coffee seeds (6.50), frying cabbage (4.52), brewing coffee (4.14), grilling clam (3.91), boiling clam (3.89), and steaming cabbage (3.21). Their concentration data were also evaluated against regulation guidelines for indoor air quality (IAQ). Comparison of these pollutant data confirms that some cooking approaches can contribute significantly to the build up of nuisance and hazardous pollution concurrently.Journal of hazardous materials 02/2011; 188(1-3):443-54. · 4.14 Impact Factor
- [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.Journal of dental research, dental clinics, dental prospects. 01/2013; 7(3):119-130.
- [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.AbstractAim 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.International Endodontic Journal 02/2010; 43(3):200 - 209. · 2.05 Impact Factor
Dental Materials Journal 27(1)：75－80, 2008
Removal of Resin-based Root Canal Filling Materials with K3 Rotary Instruments:
Relative Efficacy 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: email@example.com
Received July 4, 2007/Accepted August 16, 2007
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 com-
binations 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. How-
ever, 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 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 filling material, Ni-Ti rotary instrumentation, Root canal retreatment
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 standards2). 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 anatomy2). Reinfection resulting from
coronal leakage is also regarded as a major contrib-
uting cause3). In these cases, non-surgical root canal
retreatment may be required to re-disinfect the
canals and re-establish healthy periapical tissues4).
The retreatment procedure requires the removal of
pre-existing root canal filling materials, followed by
chemomechanical reinstrumentation and refilling of
Presently, gutta-percha ― in combination with
sealers ― is the most commonly used material for
root canal filling. However, of late, various resin-
based root canal filling 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-filled teeth5,6). 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 sealer5,6). Another newly developed resin-based
sealer is the SuperBond sealer (Sun Medical,
Moriyama, Japan). This is a modified preparation of
4-META MMA/TBB resin-based adhesive material,
which is reported to show high bond strength7) and
durable seal8) to root canal dentin.
Retreatment of roots filled with resin-based
materials may cause serious problems due to the
difficulty 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
Several studies have evaluated the efficacy of
different engine-driven nickel-titanium (Ni-Ti) file
systems in the removal of root canal filling materials,
whereby these systems promised reduced working
time9-13). Removal of Epiphany/Resilon with Ni-Ti
rotary files has also been investigated14-16), although
the efficacy 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 filling materials. Simulated
curved canals in resin blocks, which are widely used
to evaluate the root canal shaping ability of different
instruments17), were employed for the purpose of
Removal of resin-based materials with K3 files76
MATERIALS AND METHODS
Canal preparation and filling
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
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 files 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 filled 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 filling
materials used in the present study. The specimens
were stored at 37℃ in 100％ humidity for seven days
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
Orifice 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 final 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 five canals in
each group, approximately 0.1 ml of d-limonene-
based gutta-percha solvent (GP Solvent, Nishika,
Shimonoseki, Japan) was applied with every file
change. Files were discarded after usage in 10 canals.
The working time that elapsed until the last
instrument (30/.06) reached the working length,
Resilon (polyester-based filling
Batch no.Main componentsManufacturer
07120484polycaprolactone, glass fillers,
bismuth oxychloride, barium
Pentron Clinical Technologies,
Gutta-percha points (gutta-
percha-based filling material)
zinc oxide, Zipperer, Munich, Germany
Epiphany sealer (dual curable
composite resin sealer)
calcium hydroxide, barium
sulphate, barium glass, bis-
muth oxychloride, silica
Pentron Clinical Technologies,
SuperBond sealer (4-META
MMA/TBB resin sealer)
PMMA, zirconium oxide
Sun Medical Co., Moriyama,
Canals N (Zinc oxide non-
higher fatty acids
zinc oxide, rosin, barium sul-
phate, bismuth subcarbonate
Showa Yakuhin Kako Co.,
Table 1 Root canal filling 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 Scheffe’ s test.
The frequency of procedural errors (file 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-percha18)
and also applied for removing gutta-percha and
Epiohany/Resilon15). The effect of heat application
on working time was evaluated for Resilon-filled
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 Orifice 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
The use of GP Solvent did not significantly
influence 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 significantly longer working time
compared with the other groups. No significant
differences were detected among SuperBond/Resilon,
and Canals N/gutta-
Morphometric analysis revealed that the canal
area was increased during removal. However, no
significant 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 significantly
(p<0.05) following the use of System B (Fig. 2).
In the 68 canals examined in this study, file
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 filling materials using K3 instruments
(mean and SD; n＝10 each). *: p<0.05.
†Values are expressed as the number of pixels. N＝10
No significant differences between groups; p<0.05, one-way
Table 2 Canal areas removed during filling material
Removal of resin-based materials with K3 files78
In this study, we aimed to examine the efficacy
of Ni-Ti rotary instruments in the retreatment of
canals filled with resin-based filling 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 filling, which
might have created a homogeneous filling with a
relatively thin layer of sealer19). 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 a“nearly ideal canal
wall-sealer-core monoblock”should be removed from
a curved canal. Under such challenging conditions,
undesirable instrument effects (file 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 efficacy of K3 instruments would be far more
The present results demonstrated that the
Epiphany/Resilon group required a significantly
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 influencing 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
filling 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 wall20), the use of
sodium hypochlorite that may adversely affect bond
strength21,22), and the presence of uninstrumented
areas23) 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 dentin24,25) 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 efficient in the removal
of gutta-percha13) and Resilon14). Under the present
experimental conditions, it was nearly impossible to
remove Epiphany/Resilon and SuperBond/Resilon
using hand files (data not shown), therefore further
supporting the efficiency of K3. Several studies
have demonstrated that different Ni-Ti rotary
systems required less working time compared with
hand instruments for removing gutta-percha9-13) and
Resilon15), although opposite results have also been
presented16,26). Rotary instruments may be efficient
in disintegrating core materials, since they may
effectively auger the materials following softening
with frictional heat. On the other hand, removal
with hand files may be dependent on the
practitioner’ s ability to
materials and is hence more technique-sensitive.
remove existing core
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 filling 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-percha27), 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 sufficient for the solvent.
Thus, our data were not necessarily against the
use of solvents for gutta-percha removal, although
it seemed necessary to find alternatives that are
applicable for resin-based root canal filling materials.
The results of the present morphometric analy-
sis were in agreement with the finding that the canal
area increased after retreatment28). The type of
filling material did not influence 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 filling
materials. This agreed with the suggestion that
aggravate canal transportation28,29).
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 canal15). It should be noted that the working
time for the negotiation of the remaining apical
segment also decreased significantly 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 compaction30),
that the heating procedure was not harmful to the
Although this study suggested the efficacy of
K3 instruments in removing resin-based root canal
filling materials, several issues remained to be fully
evaluated before routine usage can be recommended.
In particular, file separation remained a matter
of concern as indicated by previous studies9,11,31).
This study also showed the occurrence of ledge
formation and file separation only in Resilon-
filled canals, although relatively low in frequency.
Preparation of a“glide path”using 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
may cause and/or
apparent that rotary instruments alone were not
sufficient for the complete removal of root canal
filling materials, since a number of studies have
demonstrated the remnants of gutta-percha9-15,26,31)
and Resilon14-16) on the canal wall. Subsequent hand
instrumentation after rotary instrumentation might
thus facilitate the thorough removal of residual
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 efficient method for the removal of resin-based
root canal filling materials, although safety issues
remained to be fully evaluated before routine usage
for this purpose can be recommended.
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