The efficacy of dynamic irrigation using a commercially available system (RinsEndo) determined by removal of a collagen 'bio-molecular film' from an ex vivo model.

Abstract

To compare the efficacy of three irrigation protocols using an established ex vivo bio-molecular film model.
Thirty human teeth with single straight canals were randomly allocated to three groups [static, manual-dynamic, automated-dynamic (RinsEndo]; each with a sub-group (n = 5) for needle position at 4 or 10 mm short of the working length (WL). The root canals were prepared to apical size 40, taper 0.08. The teeth were split longitudinally into two halves and a standard coat of stained-collagen was applied to the canal surfaces. The re-assembled teeth were irrigated using one of the protocols with the irrigation needle at one of two positions. Digital images of the canal surfaces, before and after irrigation with 18 mL of 2.5% NaOCl, were used to score surface coverage with stained-collagen using image-analyses (ipWin4). The data were analysed using linear regression models.
The canal area covered with stained-collagen was significantly (P < 0.001) less after dynamic irrigation (manual/automated) compared with static irrigation; but automated-dynamic irrigation was significantly (P = 0.037) less effective than manual-dynamic irrigation. The 'orientation of needle port', 'corono-apical level of canal' and 'apical extent of needle placement' were significant (P < 0.001) factors influencing efficacy of irrigation. Residual collagen was most evident in the coronal third. Deeper penetration of the needle tip resulted in significantly (P < 0.001) more effective collagen removal.
Automated-dynamic irrigation was significantly more effective (16%) than static irrigation but significantly less effective (5%) than manual-dynamic irrigation. Irrigation was more effective (7%) when the needle was placed closer to WL.

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The efficacy of dynamic irrigation using
a commercially available system (RinsEndo? ?)
determined by removal of a collagen ‘bio-molecular
film’ from an ex vivo model
S. McGill, K. Gulabivala, N. Mordan & Y.-L. Ng
Unit of Endodontology, UCL Eastman Dental Institute, University College London, London, UK
Abstract
McGill S, Gulabivala K, Mordan N, Ng Y-L. The efficacy of
dynamic irrigation using a commercially available system
(RinsEndo?) determined by removal of a collagen ‘bio-molec-
ular film’ from an ex vivo model. International Endodontic
Journal.
Aim To compare the efficacy of three irrigation
protocols using an established ex vivo bio-molecular
film model.
Methodology Thirtyhuman
straight canals were randomly allocated to three
groups [static, manual-dynamic, automated-dynamic
(RinsEndo?)]; each with a sub-group (n = 5) for needle
position at 4 or 10 mm short of the working length
(WL). The root canals were prepared to apical size 40,
taper 0.08. The teeth were split longitudinally into two
halves and a standard coat of stained-collagen was
applied to the canal surfaces. The re-assembled teeth
were irrigated using one of the protocols with the
irrigation needle at one of two positions. Digital images
of the canal surfaces, before and after irrigation with
18 mL of 2.5% NaOCl, were used to score surface
teeth withsingle
coverage with stained-collagen using image-analyses
(ipWin4?). The data were analysed using linear
regression models.
Results The canal area covered with stained-collagen
was significantly (P < 0.001) less after dynamic
irrigation (manual/automated) compared with static
irrigation; but automated-dynamic irrigation was sig-
nificantly (P = 0.037) less effective than manual-
dynamic irrigation. The ‘orientation of needle port’,
‘corono-apical level of canal’ and ‘apical extent of
needle placement’ were significant (P < 0.001) factors
influencing efficacy of irrigation. Residual collagen was
most evident in the coronal third. Deeper penetration of
the needle tip resulted in significantly (P < 0.001)
more effective collagen removal.
Conclusions Automated-dynamic
significantly more effective (16%) than static irrigation
but significantly less effective (5%) than manual-
dynamic irrigation. Irrigation was more effective (7%)
when the needle was placed closer to WL.
irrigationwas
Keywords: bio-molecular film, irrigation, RinsEndo,
root canal.
Received 30 November 2007; accepted 29 January 2008
Introduction
One of the principal roles of root canal irrigation is to
assist in the removal of the bacterial biofilm from
uninstrumented surfaces (30–50% of the root canal
wall) (Peters et al. 2001, Gulabivala et al. 2005). The
variable nature of such bacterial biofilms (Nair 1987,
Richardson et al. 2005, Rojekar et al. 2006) and even
those generated artificially in extracted teeth (Patel
et al. 2007), renders such models ineffective for the
purposes of evaluating the factors influencing irrigation
efficacy without prohibitive sample sizes. For this
reason, a predictable ex vivo bio-molecular film model
was proposed as a standardized and simple screening
tool, its purpose was to mimic the hydrodynamic
Correspondence: Y-L. Ng, Unit of Endodontology, UCL East-
man Dental Institute, University College London, 256 Grays
Inn Road, London WC1X 8LD, UK (Tel.: 020 7915 1233; fax:
020 7915 2371; e-mail: p.ng@eastman.ucl.ac.uk).
doi:10.1111/j.1365-2591.2008.01408.x
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behaviour of a bacterial biofilm (Huang et al. 2007).
This model was able to reveal a significant relationship
between apical canal enlargement, canal taper and
irrigant agitation. In the previous study, the irrigant
was manually agitated with a well-fitting gutta-percha
cone (manual-dynamic irrigation); the effect of number
of cycles (per unit volume of irrigant) was investigated.
The maximum number of strokes was 100; some
clinicians balk at the laborious nature of such a
procedure, whilst others applaud its utter simplicity
and cost-effectiveness. The former group may therefore
wish to adopt commercially available devices for
automating agitation of the irrigant.
A number of automated systems specifically designed
for agitation of the irrigant in the root canal system are
available on the market and include: sonic (Sabins et al.
2003); ultrasonic (Cunningham et al. 1982a,b, Sabins
et al. 2003) or pressure alternation systems. Examples
of the latter group include RinsEndo?(Braun et al.
2005, Muselmani et al. 2005), Endo-Vac?or like
(Fukumoto et al. 2006, Nielsen & Baumgartner 2007)
and other variations (Lussi et al. 1993, Walters et al.
2002). Sonically or ultrasonically activated smooth or
fluted stainless steel instruments bear the potential risks
of instrument separation, ledge formation or irrigant
extrusion beyond the apical foramen. The RinsEndo?
system (Du ¨rr Dental GmbH & Co. KG, Bietigheim–
Bissingen, Germany) (Fig. 1) uses pressure-suction
technology to deliver
(6.2 mL min)1) and activates (1.6 Hz) it automatically
(Du ¨rr Dental). It has been shown in an extracted tooth
model to be superior to conventional static irrigation in
removal of pulp tissue (Braun et al. 2005) and killing of
Enterococcus faecalis (Muselmani et al. 2005). Its effi-
cacy has not been compared with manual dynamic
irrigation (Huang et al. 2007). The aim of this study
theirrigant solution
was to evaluate the efficacy of three irrigation protocols
(static, manual-dynamic, automated-dynamic using
RinsEndo?) for removal of a standard stained-collagen
film coating the root canal walls of extracted teeth
(Huang et al. 2007).
Materials and methods
Collection and preparation of extracted teeth
Thirty extracted human permanent teeth (maxillary or
mandibular anterior teeth, mandibular premolars) with
single canals, straight mature roots and with no caries
or resorption, were collected and stored in 4% formal
saline. They were randomly assigned to three experi-
mental groups (group A for static irrigation, group B for
manual-dynamic irrigation, group C for automated-
dynamic irrigation). The 10 teeth in each group were
randomly divided into two further equal subgroups
(Table 1).
After accessing, the tooth length was determined by
placing a size 10 stainless-steel K flex file (Kerr UK Ltd,
Peterborough, UK) in the canal and extending it until
visible at the apical foramen. All the teeth were
decoronatedtogivea
18.0 mm; the working length was set at 18.0 mm; at
the apical terminus.
The canals were prepared using SystemGT?instru-
ments (Dentsply Maillefer, Ballaigues, Switzerland) in a
70 : 1 controlled-torque, low speed rotary handpiece at
300 rpm, to apical size 40 with a 0.08 taper following
the manufacturer’s protocol (Dentsply Maillefer). Dur-
ing instrumentation, each tooth was irrigated with
50 mL of 2.5% sodium hypochlorite (NaOCl) (Teepol?
bleach; Teepol products, Egham, UK), delivered with a
3 mL Monoject?Luer lock syringe with a 27 gauge
needle (Sherwood Medical, St Louis, MO, USA).
standardizedlengthof
Figure 1 RinsEndo?system.
Table 1 Allocation of tooth samples
Groups
(mode of irrigation) Subgroups
No. of
teeth
Level of
irrigation
needle tip
penetration
(mm from
apical foramen)
A (static irrigation) A1
A2
B1
B2
C1
C2
5
5
5
5
5
5
4
10
4
10
4
10
B (manual-dynamic
irrigation)
C (automated-dynamic
irrigation)
Dynamic root canal irrigation McGill et al.
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Each tooth was partly embedded in silicone putty
(President Putty Colte `ne?, Altsta ¨tten, Switzerland) to
create a set matrix which allowed reassembly of the
tooth for irrigation tests after splitting. The tooth was
then grooved on the buccal and palatal surfaces along
its entire length using a diamond disc (Abrasive
Technology Inc., Westerville, OH, USA) and cushioned
on another silicone matrix to split into two halves
using an osteotome and mallet. The two halves of the
canal were randomly assigned as side facing (F) or
opposing (O).
Four layers of collagen solution (type I rat tail
collagen in 0.6% acetic acid solution, First Link Ltd.,
Birmingham, UK) mixed with Chinese calligraphic ink
(Kai-Ming, Tainan, Taiwan), in a ratio of 5 : 1, were
applied to the canal surfaces using a small brush and
the solvent allowed to evaporate from the acid solution
at room temperature for 48 h to enable the collagen to
form a gel.
Each split half of the root was equally divided into
coronal, middle and apical sections and marked with a
sharp pencil. The split tooth was reassembled for
irrigation tests and disassembled for examination.
Digital images were taken before and after irrigation
with 18 mL of NaOCl using a digital camera (Cool-
SNAP-Procf, MediaCybernetics?, Silver Springs, MD,
USA) (Huang et al. 2007).
Irrigation experiments
The irrigation protocols for canals in group A (static
irrigation) and B (manual-dynamic irrigation) were
adopted from Huang et al. (2007) whilst the protocol
for canals in group C (automated-dynamic irrigation)
was adopted from the manufacturer’s instructions for
RinsEndo (Du ¨rr Dental).
The reassembled canals in group A (subgroups 1 and
2) were irrigated with 2.5% NaOCl, delivered with a
Monoject?endodontic 3 mL syringe through a Luer-
lock 30 gauge Max-I-ProbeTMneedle (Maillefer, Ballai-
gues, Switzerland) at a rate of 6 mL min)1. The
irrigating needle was inserted to 4 mm (subgroup A1)
or 10 mm (subgroup A2) short of the working length
and a total of 18 mL of solution was delivered in six
3 mL boli. The open side-port of the needle always
faced the canal side designated ‘A’, in a fixed orienta-
tion.
For the canals in group B (subgroups B1 and B2), the
protocol for irrigation was the same as for group A with
the addition of intra-canal push–pull manipulation of a
size 40/0.08 taper gutta-percha point (SybronEndo,
Orange, CA, USA). One hundred push–pull strokes
(each with a 5 mm amplitude and reaching the
working length) were performed after introducing
the first 3 mL of the irrigant, followed by delivery of
the next 6 mL in two 3 mL boli. Therefore, 100 push–
pull strokes were used for each 9 mL of irrigation. This
pattern was repeated twice until the entire 18 mL was
delivered with a total of 200 push–pull strokes.
For the canals in group C (subgroups C1 and C2), the
protocol for irrigation was similar to that for group A.
The irrigant was delivered and agitated by activation of
the RinsEndo?handpiece (Du ¨rr Dental) using the
needle provided. The supplied 6-mL syringe was filled
with 3 mL of NaOCl and delivered by the handpiece at
a manufacturer’s set rate of 6.2 mL min)1. Six cycles
with 3 mL each were completed, with a 30-s pause
between, until 18 mL of irrigant had been delivered.
The compressed air pressure supplying the hand-piece
was adjusted to 4 bars to ensure it was within the
recommended range (2.3–4.2 bar).
Image and statistical analyses
The digital images were analysed using ipwin4?
(MediaCybernetics?, Silver Spring, MD, USA) software
to quantify residual canal coverage by the stained
collagen. In total, 360 images (12 images per tooth)
were taken and digitized. The means and standard
deviations of the percentage of canal surface coverage
with residual stained collagen after irrigation were
calculated for each corono-apical section, on each side
of the canal. The generalized estimating equation (GEE)
approach (STATA 9; STATA Corporation: College
Station, TX, USA, 2005) was used to investigate the
influence of the mode of irrigation as well as other
predictive factors (corono-apical level of canal, apical
extent of needle placement, orientation of irrigation
needle port) on the efficacy of irrigation using ‘per-
centage of canal coverage with residual collagen’ as the
independent variable. The ‘clustering’ effect of the
measurements taken from different levels of the same
canal surface was accounted for in the GEE linear
regression model.
Results
The mean percentages of canal surface coverage with
residual stained collagen after static, manual-dynamic
or automated-dynamic irrigation are summarized in
Figs 2 and 3; some obvious trends were evident. There
was less canal coverage with residual stained collagen
McGill et al. Dynamic root canal irrigation
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after manual- or automated-dynamic irrigation com-
pared with static irrigation. The canal surface facing
the open side-port of the needle had less residual
collagen after irrigation than the opposing surface. The
level of the canal had an influence on residual collagen.
The least residual collagen was found in the ‘apical
levels’ for subgroups A1–C1 (needle at 4 mm) and
‘middle levels’ for subgroups A2–C2 (needle at 10 mm).
The efficacy of irrigation measured as ‘percentage of
canal coverage with residual stained collagen’ was
significantly (P < 0.05) influenced by all four explan-
atory variables. In descending order of effect (according
to the absolute Z-values in Table 2), the relative ranking
was: orientation of port of needle, mode of irrigation,
apical extent of needle placement and corono-apical
level of the canal (Table 2). Both automated-dynamic
irrigation (RinsEndo?) (16%) and manual-dynamic
irrigation (21%) were significantly (P < 0.001) more
effective in removing stained collagen from the root
canal than static irrigation. RinsEndo?was signifi-
cantly (P = 0.037) less effective (21–16 = 5%) than
manual-dynamic irrigation. Irrigation was significantly
(P < 0.001) more effective when the needle was placed
closer to the apical foramen (7%) and on the canal
surface facing the port of the needle (4%) than the
contrary. After irrigation, the coronal third had signif-
icantly (P < 0.001) more area (14%) covered with
residual stained collagen than the apical third, whist
there was no significant (P = 0.289) difference between
the apical and middle thirds.
Discussion
The test model adopted (Huang et al. 2007) allowed
quantification and comparison of the efficacy of
removal of a bio-molecular film from the root canal
Apical F
Middle F
Coronal F
Apical O
Middle O
Coronal O
Manual-dynamic
RinsEndo
Static
0
10
20
30
40
50
60
70
80
90
100
%
Figure 2 Mean percentage of canal
surface coverage with residual collagen
by different levels (apical, middle, coro-
nal) after irrigation with the needle
placed at 10 mm from the apical termi-
nus (F: surface facing the open side-port
of needle; O: surface opposing the open
side-port) for groups A2 – C2.
Apical F
Middle F
Coronal F
Apical O
Middle O
Coronal O
Manual-dynamic
RinsEndo
Static
0
10
20
30
40
50
60
70
80
90
100
%
Figure 3 Mean percentage of canal
surface coverage with residual collagen
by different levels (apical, middle, coro-
nal) after irrigation with the needle
placed at 4 mm from the apical terminus
(F: surface facing the open side-port of
needle; O: surface opposing the open
side-port) for groups A1 – C1.
Dynamic root canal irrigation McGill et al.
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walls by different irrigation regimens. The model is,
however, limited to single-rooted teeth with simple
straight canals as teeth with curved canals are less
predictably split. The thickness of four layers of stained-
collagen applied by the author (SM) ranged between
9–37 lm, which was greater than in the previous
study (Huang et al. 2007), which reported a range of
5–15 lm. Both these ranges were nevertheless near
the reported range of thickness of bacterial biofilms at
21–30 lm (Distel 2002). Previous pilot studies had
confirmed that the stained collagen could neither be
decolourized by 2.5% sodium hypochlorite solution
even after soaking for 12 h nor be flushed out by
irrigation with water alone, but it could be gradually
flushed out by sodium hypochlorite solution (Huang
et al. 2007).
All the canal preparations were standardized to the
larger dimensions (apical size 40/taper 0.08) previously
tested (Huang et al. 2007) to facilitate the optimal
efficacy of both static and dynamic irrigation. Most
other irrigation parameters, such as position of place-
ment of the irrigation needle, rate of irrigant delivery
and orientation of port of needle, were adopted from the
previous work (Huang et al. 2007) to facilitate com-
parison of results. In the present study, an extra
irrigation parameter, apical extent of needle placement
was tested by including appropriate sub-groups. The
reason for introducing this variable, given that its effect
in static irrigation was already known (Sedgley et al.
2005), is that the RinsEndo?manufacturer’s instruc-
tions (Du ¨rr Dental) suggest that the apical third of the
canal may be effectively rinsed with the cannula
restricted to the coronal third of the root canal because
of the pulsating nature of the fluid flow. The RinsEndo?
handpiece had a pre-set irrigant delivery rate of
6.2 mL min)1
which was
6 mL min)1used for static and manual-dynamic irri-
gation groups but the difference was negligible.
The results of this study showed that all four
explanatory variables: orientation of port of needle,
mode of irrigation, corono-apical level of the canal and
apical extent of needle placement had significant
influence on the efficacy of irrigation. The former three
significant influencing factors were consistent with the
previous report (Huang et al. 2007). In contrast to their
findings, the present study found no significant differ-
ence in the efficacy of stained collagen removal from
the apical and the middle thirds. This difference may be
attributable to the two different levels of needle
placement (4 or 10 mm from apical terminus) used in
this study in contrast to the 4 mm position adopted by
Huang et al. (2007). The corono-apical level of canal
with the least area covered with residual stained
collagen corresponded to the apical extent of needle
placement and site of deposition of the irrigant bolus
(Figs 2 and 3). This finding would appear to contradict
the suggestion by the manufacturer that needle
position need not influence apical irrigation with
RinsEndo?.
This study found that both approaches of dynamic
(manual and automated) irrigation resulted in signif-
icantly less residual stained collagen than with static
irrigation, consistent with previous findings (Huang
et al. 2007) and of those who agitated the irrigant
with hand files, irrigation needles (Cecic et al. 1984,
Druttman & Stock 1989), or ultrasonic activation
slightly higherthan
Table 2 Linear regression model incorporating three significant explanatory variables simultaneously using ‘percentage of surface
coverage with residual stained collagen as the dependent variable
Explanatory variableCoefficient 95% CI for coefficient P-value Z-value
Constant
Mode of irrigation
Static irrigation
Manual-dynamic irrigation
Automated-dynamic irrigation
Corono-apical level of canal (apical third)
Apical
Middle third
Coronal third
Level of needle penetration
Needle tip at 4 mm from apical foramen
Needle tip at 10 mm from apical foramen
Canal surface
Port of needle facing side
Port of needle opposing side
43.1 39.4, 46.9 <0.001
1–
)24.2, )17.2
)19.3, )12.7
–
<0.001
<0.001
)20.7
)16.0
)11.5
)9.6
1––
)1.8
13.8
)7.6. 4.0
7.9, 19.7
0.289
<0.001
)0.6
4.6
1
7.4
––
<0.0014.9, 10.05.7
1
4.4
––
<0.001 3.7, 5.111.9
McGill et al. Dynamic root canal irrigation
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