Basic Research—Technology
In Vitro Canal and Isthmus Debris Removal
of the Self-Adjusting File, K3, and WaveOne Files
in the Mesial Root of Human Mandibular Molars
Matthew A. Dietrich, DDS, Timothy C. Kirkpatrick, DDS, and John M. Yaccino, DDS
Abstract
Introduction: The purpose of this study was to
compare the effectiveness of debris removal between
the Self-Adjusting File (SAF), WaveOne, and K3 file
systems in the mesial roots of mandibular molars. In
addition, the SAF was tested as a potential adjunct after
instrumentation with other systems. Methods: The
mesial roots of 30 extracted mandibular molars were
mounted in resin by using the K-Kube, sectioned at
2 and 4 mm from working length, and randomly placed
into 3 groups: K3 group, sequential preparation with
K3 files to an apical size of 35/.04; WaveOne group,
preparation with WaveOne primary file; and SAF group,
preparation with SAF. Images were taken before instrumentation, after instrumentation, after final irrigation, and after SAF adjunct irrigation. A cleanliness
percentage was calculated by using interactive software. Comparisons between groups were analyzed
with repeated-measures analysis of variance and post
hoc tests (P < .05). Results: There was no significant
difference in canal cleanliness among the groups, but
the WaveOne was significantly worse for isthmus cleanliness. Use of the SAF as an adjunct only significantly
improved canal cleanliness in the K3 group at the
2-mm level by an average of 1.7%. Conclusions: There
was no difference in canal cleanliness between the 3 file
systems; however, the SAF and K3 files performed
significantly better than the WaveOne with respect to
isthmus cleanliness. When used as a final irrigation
adjunct device after instrumentation, the SAF provided
a significant improvement only in a subset of the K3
group. (J Endod 2012;38:1140–1144)
Key Words
K-Kube, K3, SAF, Self-Adjusting File, WaveOne
From the Department of Endodontics, Wilford Hall Ambulatory Surgical Center, Lackland Air Force Base, Texas.
Address requests for reprints to Dr Timothy C. Kirkpatrick,
Program Director, Endodontics Residency, Wilford Hall Ambulatory Surgical Center, 59th Dental Training Squadron/SGDTN,
2450 Pepperrell Street, Lackland AFB, TX 78236. E-mail
address: [email protected]
0099-2399/$ - see front matter
Copyright ª 2012 American Association of Endodontists.
http://dx.doi.org/10.1016/j.joen.2012.05.007
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Dietrich et al.
T
reatment and prevention of apical periodontitis is the goal of endodontic therapy
(1). This is accomplished with thorough chemomechanical debridement of the
root canal system, followed by complete obturation and adequate restoration (2, 3).
Root canal anatomy can be complex, with isthmuses, fins, and accessory canals that
can harbor residual debris, pulp tissue, bacteria, and their by-products (4–6).
Recent advances in instrumentation and irrigation have improved our ability to
debride canals, but it is still not possible to remove all debris. Inadequate canal
debridement can lead to a decrease in endodontic success (7).
Instrumentation of the canal is an essential part of chemomechanical canal preparation. It facilitates removal of pulp tissue and debris and enhances bacterial elimination through apical delivery of irrigant (8–11). Many instrumentation systems are
available to achieve these goals, with several using nickel-titanium (NiTi) rotary files.
Despite variations in file design, fabrication, and technique, significant portions of
the canal are untouched, and some debris remains (12–15). Studies have shown
less debris remains with larger apical preparation sizes or tapers, although this can
be at the expense of dentinal wall thickness (16, 17). Many systems use a rotational
motion, but a reciprocating motion is another option. Grande et al (18) showed reciprocating files enlarged oval canal configurations better in the middle and coronal thirds
of roots than ProTaper files, but no difference was seen in the apical third. This correlates with the findings of Wu et al (19) that oval canals become more round as they
approach the apical foramen.
A recently introduced file system is the WaveOne (Dentsply-Tulsa Dental, Tulsa,
OK). It shapes the canal by using a single file in a reciprocating motion. The file is manufactured with M-Wire NiTi and uses a dedicated handpiece and motor to accomplish
the reciprocating mechanics (20). The Self-Adjusting File (SAF) (ReDent Nova, Ra’anana, Israel) is an endodontic file with a unique design. It is a thin-walled, hollow
file made of a NiTi lattice that is compressible in a canal that has been previously shaped
to a #20 hand file (21). The file conforms to the canal shape and permits irrigant flow
through the file. In a vibrating motion, the SAF circumferentially removes dentin from
the walls of the canal, simultaneously enlarging and irrigating, while maintaining the
original canal configuration (21). Oval canals offer unique debridement challenges,
and the SAF has been shown to instrument these canals more effectively than traditional
rotary files (22–24).
Presently there are few studies comparing the ability of the SAF and WaveOne to
remove debris in complex canal systems with isthmus connections. Therefore, the
purpose of this study was to compare the effectiveness of debris removal between
the SAF, WaveOne, and a conventional NiTi rotary file system in the mesial root of
mandibular molars. A secondary aim assessed the ability of the SAF to work as a potential
irrigation adjunct after instrumentation with other systems.
Materials and Methods
Specimen Preparation
Specimen preparation closely followed that used by Howard et al (25). Thirty
extracted human mandibular molars stored in 0.5% chloramine-T solution were
selected for this study. All of the teeth had an isthmus in the apical third of the mesial
root that was confirmed with a three-dimensional scan (Accuitomo; J. Morita, Irvine,
CA). After flattening cusps to provide reproducible reference points, a standard access
JOE — Volume 38, Number 8, August 2012
Basic Research—Technology
was prepared, and the mesial canals were negotiated to length with #10
K-flex file. Sterile water was used for all irrigation before experimental
instrumentation. The coronal third was flared by using Gates Glidden
drills (Miltex Inc, York, PA) sizes #2–3. The #10 K-file was reinserted
until the tip was just visible at the apical foramen, and working length
(WL) was determined by subtracting 1 mm. Size 15 and 20 hand files
were used to create a #20/.02 glide path. Teeth were then randomly
assigned to 3 groups of 10. Group 1 was treated with K3 files (SybronEndo, Orange, CA), group 2 with the WaveOne Primary file, and group
3 with the SAF. Specimens in group 3 had a 20/.04 rotary file placed to
WL per manufacturer’s recommendation to facilitate SAF use. After
canal preparation, the access opening was sealed with a moist cotton
pellet and Cavit (3M ESPE, St Paul, MN). The distal root was amputated,
and Triad clear gel (Dentsply/Trubyte) was used to seal the apical
foramina on the mesial root and the opening of the amputated root
to prevent mounting resin from obstructing the canal system.
All specimens were mounted into a custom-made metal cube (KKube) (26) and sectioned at 2 and 4 mm from WL using the technique
described by Howard et al (25). This produced 2 sections for evaluation, at the 2-mm and 4-mm levels.
manufacturer’s recommendation for the WaveOne technique, followed
by a final flush of 0.5 mL NaOCl/canal. All canals were dried, disassembled, and photographed as before.
Method of Evaluation
Each specimen was evaluated for canal cleanliness while disassembled as described by Howard et al (25). The magnification and
aspect viewed (coronal or apical) remained constant for each specimen section for all assessment points. A cleanliness percentage was
calculated before experimental instrumentation, after instrumentation,
after final irrigation, and after SAF adjunct irrigation (if applicable) for
each level.
The average volume of NaOCl used during instrumentation and
final irrigation per canal was K3 group, 3.5 mL; WaveOne group, 2.5
mL; and SAF group, 21 mL. No statistically significant differences
were found between 2-mm and 4-mm levels for canals or isthmuses
after postinstrumentation irrigation; thus data from both levels were
combined for statistical analysis. There was no difference in canal cleanliness between the 3 file systems tested; however, the SAF and K3 files
performed significantly better than the WaveOne with respect to isthmus
cleanliness (P < .012) (Fig. 1). Significant differences were only reported at the postinstrumentation irrigation evaluation point because
that was considered the end point for all groups’ treatment protocols,
and clinically the teeth would be ready for obturation. Other evaluation
points are included for completeness.
The results of using the SAF as an adjunct irrigation device are
shown in Figure 2. The only statistically significant improvement was
seen in the K3 group at the 2-mm canal level (P < .021).
Experimental Canal Preparation
After preinstrumentation images were made, the tooth was reassembled in the K-Kube, and a #20 file was taken to WL to verify proper
reassembly. The WL was shortened 0.5 mm to compensate for kerf loss.
Each specimen in group 1 was prepared with K3 0.04 rotary files by
using a crown-down technique to a master apical file size #35/.04 taper.
One-half milliliter of 6% sodium hypochlorite (NaOCl) was used
between each file to irrigate the canal with a 30-gauge Max-i-Probe
(Dentsply, York, PA). Canals were dried, and teeth were disassembled
for viewing. The total volume of NaOCl per canal was recorded.
Each specimen in group 2 was prepared with the WaveOne
Primary file (25/.08) according to the manufacturer’s recommendations. One-half milliliter of 6% NaOCl was placed with a 30-gauge
Max-i-Probe into each canal before initial insertion and each time the
file was removed from the canal until the file reached WL per manufacturer’s recommendations. Canals were dried, and teeth were disassembled for viewing. The total volume of NaOCl per canal was recorded.
In group 3, canals were cleaned and shaped with a new 1.5-mm
diameter SAF per manufacturer’s instructions for 4 minutes per canal
by using 6% NaOCl at a rate of 5 mL/min. The total volume of NaOCl
delivered was 20 mL/canal. Canals were dried, and teeth were disassembled for viewing.
Postinstrumentation Irrigation Treatment
All specimens were reassembled as before and subjected to
a passive irrigation rinse of 2 mL 17% ethylenediaminetetraacetic
acid for 1 minute. Specimens in groups 1 and 3 were then flushed
with 1 mL 6% NaOCl/canal within 1 mm of WL via a 30-gauge Maxi-Probe. Specimens in group 2 were filled with 0.5 mL of 6% NaOCl
in each canal and sonically activated for 45 seconds by using the
EndoActivator (Dentsply Tulsa Dental) #15/.02 tip following the
JOE — Volume 38, Number 8, August 2012
Post SAF Adjunct Irrigation
To test the SAF as a possible irrigation adjunct, specimens in
groups 1 and 2 were subjected to a supplemental irrigation protocol
by using the SAF. An SAF was placed to WL and activated in each canal
for 1 minute with 6% NaOCl at 5 mL/min. After a final flush of 0.5 mL
NaOCl per tooth, the canals were dried, and teeth were disassembled for
viewing.
Data Analysis
The amount of canal and isthmus cleanliness in each group level at
each evaluation point was calculated by using ImageJ software (National
Institutes of Health, Bethesda, MD). The cleanliness between groups
was compared by using repeated-measures analysis of variance and
post hoc tests (P < .05).
Results
Discussion
This study used the K-Kube model. The advantages of its unique
design have been discussed previously (25, 26); the main advantage
is the ability to allow each tooth to serve as its own control. Sections
were made at 2 and 4 mm from the WL because of the increased
likelihood of fins or isthmuses being present and the increased
difficulty in debriding these areas (Fig. 3). Overall, canals were cleaner
than isthmuses, and standard deviations were higher for isthmuses
versus canals. This is likely due to variations in isthmus width and
length. The volumes of irrigation were not standardized to represent
what is more clinically realistic. Adherence to the manufacturer’s recommended treatment protocol for the SAF resulted in much more irrigant being used relative to the other groups.
No statistically significant differences were seen between levels in
any group. This is in agreement with Howard et al (25) but differs from
Klyn et al (26). This could be due to the level of the sections evaluated.
Klyn et al evaluated sections at 1 and 3 mm from the WL, whereas the
present study used the same levels as Howard et al. The K3 group represented the control in our study. It was meant to reflect a conventional
technique by using multiple rotary NiTi files in a sequential manner to
obtain a desired apical prep size and taper. In our study, the K3 group
had 97% canal cleanliness after final irrigation, which is in agreement
with the Max-i-Probe control groups of Klyn et al and Howard et al.
Average isthmus cleanliness for the K3 group after final irrigation was
Effectiveness of Debris Removal
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Basic Research—Technology
Figure 1. Cleanliness percentage of canals and isthmuses. *Significant difference (P < .012) within each location. Differences are shown for postirrigation cleanliness only, because this was considered the end point for all 3 groups’ treatment protocols. Stdev, standard deviation.
78% in our study, which is between the percentages found by Klyn et al
and Howard et al.
The SAF in our study proved not to be statistically different from the
K3 or WaveOne files in canal cleanliness or the K3 file in isthmus cleanliness. These results differ from other studies by Siqueira et al (23) and
De-Deus et al (24) that showed SAF superior to conventional rotary NiTi
files. Conversely, a recent bacteriologic study showed a poorer result of
the SAF versus ProTaper (27). These studies used different models, but
a similarity was the ability of the SAF to instrument oval canals. Our study
looked at roots with more round canals that have narrow fins or isthmus
connections. These types of canals present distinct debridement challenges versus oval canals. Another recent study showed the SAF instrumented a significantly higher percentage of walls than rotary NiTi files in
C-shaped canals (28). This is a closer model to our study in that narrow
canal connections were assessed, but it differed in evaluation method
(micro–computed tomography).
The WaveOne is marketed as a single file system with 3 file size
options. The primary file is marketed for most canals and is what we
used in this study. There is little published research on the WaveOne
file and only 1 study evaluating canal cleanliness (29). Although it
used a different design and evaluation method than our study, it
reported that the WaveOne left significantly more debris in the apical
third, but there was no difference in the middle/coronal thirds. In
this study, it performed similarly to the K3 and SAF groups in canal
cleanliness but was significantly worse for isthmus cleanliness. Although
not a primary focus of the study, we tracked the time needed for the
WaveOne file to reach WL, and it averaged 86 seconds/tooth. This is
similar to the 82 seconds reported by Burklein et al (29). The minimal
time of instrumentation may not have permitted enough contact time for
the NaOCl to aid in debriding canal irregularities untouched by the file.
A secondary aspect of the study was to assess the ability of the SAF
to act as a final irrigation adjunct device. An application time of 1
minute was chosen because it is in the range of what manufacturers
of other irrigation adjunct devices such as EndoVac, PiezoFlow, and EndoActivator recommend. Using the SAF as an adjunct irrigation device
statistically improved cleanliness only in the K3 group at the 2-mm
canal level from 97.8% to 99.5% (P < .021); this may not have clinical
significance.
Conclusions
There was no difference in canal cleanliness between the 3 file
systems tested; however, the SAF and K3 files performed significantly
better than the WaveOne with respect to isthmus cleanliness. Using
the SAF as an adjunct irrigation device resulted in a slight but
Figure 2. K3 and WaveOne cleanliness data for postirrigation and post SAF adjunct irrigation at canal and isthmus levels. *Significant differences between the 2
treatment evaluation points within each location and level. Stdev, standard deviation.
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Dietrich et al.
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Figure 3. Sections of teeth at 4-mm level showing cleanliness before experimental instrumentation (1), postinstrumentation (2), postirrigation (3), and, if applicable, post SAF adjunct irrigation (4) in the K3 (A), WaveOne (B), and SAF (C) treatment groups.
significant improvement in cleanliness at the 2-mm canal level in the
K3 group only.
Acknowledgments
The authors thank Dr Anneke Bush for her statistical support.
This article is the work of the United States government and may be
reprinted without permission. Opinions expressed herein, unless
otherwise specifically indicated, are those of the authors. They do
not represent the views of the Department of the Air Force or any
other department or agency of the United States government.
The authors deny any conflicts of interest related to this study.
References
1. Ørstavik D, Pitt Ford TR. Essential endodontology: prevention and treatment of
apical periodontitis. Oxford: Blackwell Munksgaard; 2008.
2. Schilder H. Cleaning and shaping the root canal. Dent Clin North Am 1974;18:
269–96.
3. Gillen B, Looney S, Gu L, et al. Impact of the quality of coronal restoration versus the
quality of root canal fillings on success of root canal treatment: a systematic review
and meta-analysis. J Endod 2011;37:895–902.
4. Vertucci FJ. Root canal anatomy of the human permanent teeth. Oral Surg Oral Med
Oral Pathol 1984;58:589–99.
5. Peters OA. Current challenges and concepts in the preparation of root canal systems:
a review. J Endod 2004;30:559–67.
6. Ricucci D, Siqueira JF Jr. Fate of the tissue in lateral canals and apical ramifications in
response to pathologic conditions and treatment procedures. J Endod 2010;36:1–15.
7. Siqueira JF Jr. Aetiology of root canal treatment failure: why well treated teeth can
fail. Int Endod J 2001;34:1–10.
8. Young GR, Parashos P, Messer HH. The principles of techniques for cleaning root
canals. Aust Dent J 2007;52(Supplement):S52–63.
9. Haapasalo M, Endal U, Zandi H, Coil JM. Eradication of endodontic infection by instrumentation and irrigation solution in root canals. Endod Topics 2005;10:77–102.
10. Gulabivala K, Patel B, Evans G, Ng YL. Effects of mechanical and chemical procedures on root canal surfaces. Endod Topics 2005;10:103–22.
JOE — Volume 38, Number 8, August 2012
11. H€ulsmann M, Peters OA, Dummer PMH. Mechanical preparation of root canals:
shaping goals, techniques, and means. Endod Topics 2005;10:30–76.
12. Peters OA, Paque F. Current developments in rotary root canal instrument technology and clinical use: a review. Quintessence Int 2010;41:479–88.
13. Paque F, Ganahl D, Peters OA. Effects of root canal preparation on apical geometry
assessed by micro-computed tomography. J Endod 2009;35:1056–9.
14. Peters OA, Sch€onenberger K, Laib A. Effects of four Ni-Ti preparation techniques on
root canal geometry assessed by micro computed tomography. Int Endod J 2001;34:
221–30.
15. Wu M-K, Wesselink PR. A primary observation on the preparation and obturation in
oval canals. Int Endod J 2001;34:137–41.
16. Elayouti A, Chu AL, Kimionis I, Klein C, Weiger R, L€ost C. Efficacy of rotary instruments with greater taper in preparing oval root canals. Int Endod J 2008;41:
1088–92.
17. Card SJ, Sigurdsson A, Ørstavik D, Trope M. The effectiveness of increased apical
enlargement in reducing intracanal bacteria. J Endod 2002;28:779–83.
18. Grande NM, Plotino G, Butti A, Messina F, Pameijer CH, Somma F. Cross-sectional
analysis of root canals prepared with NiTi rotary instruments and stainless hand
files. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2007;103:120–6.
19. Wu M-K, R’oris A, Barkis D, Wesselink PR. Prevalence and extent of long oval canals
in the apical third. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2000;89:
739–43.
20. Dentsply Tulsa Dental Specialties Wave One homepage. Wave One brochure. Available at: https://store.tulsadental.com/catalog/. Accessed September 30, 2011.
21. Metzger Z, Teperovich E, Zary R, Cohen R, Hof R. The Self-Adjusting file (SAF): part
1—respecting the root canal anatomy: a new concept of endodontic files and its
implementation. J Endod 2010;36:679–90.
22. Metzger Z, Zary R, Cohen R, Teperovich E, Paque F. The quality of root canal preparation and root canal obturation in canals treated with rotary versus self-adjusting
files: a three-dimensional micro-computed tomographic study. J Endod 2010;36:
1569–73.
23. Siqueira JF Jr, Alves FRF, Almeida BM, Machado de Oliveira JC, R^oças IN. Ability of
chemomechanical preparation with either rotary instruments or self-adjusting file to
disinfect oval-shaped root canals. J Endod 2010;36:1860–5.
24. De-Deus G, Souza EM, Barino B, et al. The self-adjusting file optimizes debridement
quality in oval-shaped root canals. J Endod 2011;37:701–5.
25. Howard R, Kirkpatrick T, Rutledge R, Yaccino J. Comparison of debris removal with
three different irrigation techniques. J Endod 2011;37:1301–5.
Effectiveness of Debris Removal
1143
Basic Research—Technology
26. Klyn S, Kirkpatrick TC, Rutledge RE. In vitro comparisons of debris removal of the
EndoActivator System, the F File, ultrasonic irrigation and NaOCl irrigation alone
following hand-rotary instrumentation in human mandibular molars. J Endod
2010;36:1367–71.
27. Paranjpe A, de Gregorio C, Gonzalez A, et al. Efficacy of the self-adjusting file system
on cleaning and shaping oval canals: a microbiological and microscopic evaluation.
J Endod 2012;38:226–31.
1144
Dietrich et al.
28. Solomonov M, Paque F, Fan B, Eilat Y, Berman LH. The challenge of C-shaped canal
systems: a comparative study of the self-adjusting file and ProTaper. J Endod 2011;38:
209–14.
29. B€urklein S, Hinschitza K, Dammaschke T, Sch€afer E. Shaping ability and cleaning
effectiveness of two single-file systems in severely curved root canals of extracted
teeth: Reciproc and WaveOne versus Mtwo and ProTaper. Int Endod J 2012;45:
449–61.
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