Giornale Italiano di Endodonzia (2013) 27, 95—104
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CASE REPORT/CASO CLINICO
Cyst-like periapical lesion healing in an orthodontic
patient: a case report with five-year follow-up
Guarigione di una lesione periapicale simil-cistica in un paziente ortodontico:
case report con follow-up di 5 anni
Sergio Paduano 1,*, Roberto Uomo 2, Massimo Amato 3, Francesco Riccitiello 3,
Michele Simeone 3, Rosa Valletta 3
1
Department of Clinical and Experimental Medicine, University of Catanzaro Magna Graecia, Italy
Division of Dentistry, Department of Surgery, ‘‘Bambino Gesù’’ Children Hospital Rome, Italy
3
Department of Oral and Maxillo Facial Sciences, University of Naples Federico II, Italy
2
Received 31 July 2013; accepted 17 September 2013
Available online 11 October 2013
KEYWORDS
Cyst-like lesion;
Maxillary central
incisors;
Orthodontic treatment;
Root canal treatment;
Root resorption.
PAROLE CHIAVE
Lesione simil-cistica;
Incisivi centrali
superiori;
Abstract
Aim: To report the orthodontic movement of two central incisors through the healing site of a
maxillary cyst-like lesion of endodontic origin after nonsurgical treatment.
Case summary: This report shows the treatment of a 18-year old patient, male, with a Class II
division 2 malocclusion. He came to our attention seeking for orthodontic treatment.
Radiographic examinations revealed a large cyst-like lesion in the maxillary anterior area,
extending from the mesial surface of tooth 12 to the distal surface of tooth 21. The two upper
incisors were nonresponsive to pulp sensitivity tests. Endodontic treatment was performed first.
One week after root canal treatment had been completed with gutta-percha fillings, orthodontic
treatment was started while the bone lesion healing was still underway. At the end of the
orthodontic treatment, incisor retroclination was corrected, periapical lesion healing was
completed and there were no signs of root resorption. The five-year follow-up revealed that
* Corresponding author at: Department of the Health — University
‘‘Magna Graecia’’ Catanzaro, Viale Europa, I-88100 Loc. Germaneto
Catanzaro, Italy.
E-mail: paduano@unicz.it (S. Paduano).
Peer review under responsibility of Società Italiana di Endodonzia.
ELSEVIER
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http://dx.doi.org/10.1016/j.gien.2013.09.002
96
S. Paduano et al.
Trattamento
ortodontico;
Trattamento
endodontico;
Riassorbimento
radicolare.
occlusal relationship and dental alignment were kept stable and excellent radiographic resolution of the periapical lesion was obtained.
ß 2013 Società Italiana di Endodonzia. Production and hosting by Elsevier B.V. All rights reserved.
Riassunto
Scopo: Riportare il movimento ortodontico di due incisivi centrali attraverso il sito di guarigione
di una lesion simil-cistica di origine endodontica dopo trattamento non chirurgico.
Riassunto del caso clinico: Questo articolo riporta il trattamento di un paziente di 18 anni,
affetto da malocclusione di Classe II divisione 2, venuto alla nostra osservazione con la richiesta di
trattamento ortodontico.
Gli esami radiografici hanno messo in evidenza un larga lesione simil-cistica nella regione
mascellare anteriore, che si estendeva dalla superficie mesiale 12 alla superficie distale del 21. I
due incisivi centrali superiori rispondevano negativamente ai test di sensibilità pulpare. Una
settimana dopo il completamento del trattamento endodontico con otturazione canalare con
guttaperca, è stato iniziato il trattamento ortodontico mentre la guarigione della lesione ossea
era ancora in corso. Al completamento del trattamento ortodontico, la retroclinazione incisiva
risultava corretta e la guarigione della lesione periapicale era completa; inoltre, non erano
visibili segni di riassorbimento radicolare. Il follow-up a 5 anni, ha mostrato che i rapporti
occlusali e l’allineamento dentale erano stati mantenuti stabili; al controllo radiografico si era
evidenziata una restituito ad integrum della lesione ossea periapicale.
ß 2013 Società Italiana di Endodonzia. Production and hosting by Elsevier B.V. Tutti i diritti
riservati.
Introduction
Changes in pulp blood supply, mainly due to dental trauma,
may induce several pulp responses, leading to necrosis.
Tissue necrosis and anaerobic conditions are the ideal environment for root canal colonization on the part of opportunistic microorganisms. Inflammatory reactions, including
abscesses, granulomas and apical cysts, may develop in
the periodontal tissue in response to intracanal antigenic
content through immunopathological mechanisms.1
In order to differentiate radicular inflammatory periapical
lesions, an accurate histopathological analysis of lesions is
required.2 Nair et al.,3 after histological analysis, found that
Figure 1
15% of a sample of 256 periapical lesions were cysts, whilst
52% of the lesions were found to be epithelialized. Suspected
cystic periapical lesions may undergo asymptomatic evolution and can became quite large.4 Extensive periapical
lesions may heal after conventional endodontic therapy,
contrary to which periapical surgery may be necessary to
allow nonresponsive lesions to heal.5
Orthodontic treatment has been considered as a major
factor involved in root resorption.6 While a well cleaned
and shaped endodontically treated tooth is known to exhibit
less propensity for apical root resorption during orthodontic
tooth movement,7—10 less is known about the effects of orthodontic movement during the healing phase of periapical
lesions. Relevant literature has always suggested to wait for
Pre-treatment frontal (a) and profile (b) view of the 18-year-old patient.
Cyst-like periapical lesion healing in an orthodontic patient
97
the complete healing of the apical lesion before applying an
orthodontic force, because of the high risk of root resorption.11
This case report illustrates a combined endodontic—
orthodontic treatment in a patient with a severe deep bite
and traumatic necrosis of upper incisor and radiographic signs
of cyst-like lesion.
reached physiologically while a slight gummy smile was
observed (Fig. 1a and b). The intraoral examination
(Fig. 2a—f) revealed that oral hygiene was acceptable. First
molars and the right lower second molar had amalgam fillings. A complete permanent dentition was present (the four
third molars were asymptomatically included). Facial and
both arch midlines corresponded. Intraoral frontal and lateral views showed a severe deep bite. The incisor margin of
both central incisiors traumatized the vestibular lower incisor gingiva. The patient resulted having a bilateral Class I
molar relationship. The maxillary central incisor crowns were
displaced palatally to the arch, thus requiring considerable
apexes movement during orthodontic therapy.
Evaluation of the panoramic radiography revealed signs of
bony pathosis. A large radiolucent lesion extended from the
Case report
An 18-year-old male, with a non-contributory medical history, was brought to our attention for orthodontic treatment.
The patient’s main complaint was an unpleasant smile.
Profile and frontal photographs showed an increased lower
height. The facial profile was convex. Labial competence was
Figure 2 Pre-treatment intraoral views. (a) Frontal view shows the severe deep bite. (b) Overjet view. (c) Right and (d) left side
views show a bilateral class I molar relationship (e) Occlusal upper and (f) lower arch views, note the palatally displaced central
incisors.
98
Figure 3
S. Paduano et al.
Inizial panoramic radiograph (a) and preoperative intraoral radiograph (b) showing the large radiolucent lesion.
Figure 4 Two years post-treatment panoramic and intraoral radiograph showing the complete healing of the periapical lesions and
healthy root apexes.
Cyst-like periapical lesion healing in an orthodontic patient
99
Figure 5 Post-orthodontic treatment (a) frontal and (b) profile views. Note smile characteristic and profile improvements as
compared with Fig. 1.
Figure 6 Post-orthodontic treatment intraoral views. (a) Frontal and (b) overjet views indicate that overjet and overbite are in the
norm. (c) Right and (d) left side views show a good functional occlusion. (e) Occlusal upper and (f) lower arch views reveal the
correction of the incisor inclinations. A lower canine-to-canine fixed retainer has been applied for retention.
100
mesial surface of tooth 12 to the distal surface of tooth 21
measuring 27 mm in diameter (Fig. 3a and b). The patient
referred to have had whiplash in the past, and to present a
sporadic click in the right temporomandibular joint.
Before starting orthodontic treatment, an endodontic
consultation was required. The patient was also examined
according to the Research Diagnostic Criteria for Temporomandibular disorders (RDC/TMD)12 because of the higher
frequency of disc displacement in individuals suffering from
whiplash syndrome.13
The endodontic examination revealed that the upper
central incisors were nonresponsive to electronic and thermal pulp testing whilst adjacent teeth presented physiological responses. Pulp necrosis was diagnosed. Neither decay
nor periodontal pockets were present. It is possible that the
occlusal trauma derived from the severe anterior deep bite
which had most likely triggered off the incisor necrosis, or
from the trauma of the year before.
A diagnosis of pulp necrosis of traumatic origin with
extensive apical periodontitis was established and root canal
treatment on both incisors was performed. Upon access to
the pulp chamber, a yellow serous exudate was evident in the
canals. They were debrided with K-type files and irrigated
with 5% sodium hypochlorite solution. The working length
was assessed by apex locator and periapical radiographic
analysis. Five days later, when active drainage ceased, we
were able to perform the step back technique of canal
preparation under rubber dam isolation: canals were instrumented using Ni-Ti rotary files accompanied by irrigation
with 5% sodium hypochlorite.43 To avoid possible fractures,
a single patient use of a set of rotary file was preferred.14 A
temporary dressing of calcium hydroxide was then applied
and changed every 3 weeks for 2 months. After removal of the
dressing using K-type file and irrigation with 5% NaOCl, root
canals were filled with gutta-percha cones and Sealapex
cement (Kerr/Sybron Dental Specialities Inc., Glendora,
CA, USA) using cold lateral condensation technique.
One week later, orthodontic treatment was started. The
patient’s upper arch was bonded from tooth 16 to tooth 26
using straightwire self-ligating appliance to reduce initial
orthodontic forces and chairside time.15 Two months later
the lower arch was completely bonded, thanks to correction
of the incisor inclinations. The use of heat activated archwires was preferred to reduce initial orthodontic forces and
patient pain complaint.16 Torque of maxillary incisors was
controlled using translation arch.17 Two years after completion of the endodontic treatment, no radiographic signs of
bony defect nor root resorption were observed in the maxillary incisor area (Fig. 4a and b). After 26 months of active
orthodontic therapy, profile improved (Fig. 5a and b), correct
molar and canine relationships were achieved, overjet and
overbite were within the norm and maxillary and mandibular
arches were coordinated (Fig. 6a—f).
Comparison between pre- and post-orthodontic treatment lateral cephalograms showed evident correction of
incisor inclination and torque, demonstrating the wide movememnt of incisor roots (Fig. 7a and b).
The patient was most satisfied with the final result. The
five-year follow-up demonstrates that facial profile and smile
characteristic improvements have been maintained (Fig. 8a
and b) and the teeth have settled into a good functional
occlusion with excellent facial aesthetics (Fig. 9a—f). The
S. Paduano et al.
Figure 7 Pre- (a) and post- (b) orthodontic treatment lateral
cephalograms. Note the correction of upper incisor inclination
and torque, thanks to wide movement of incisor root.
panoramic radiograph revealed no signs of pathologic root
resorption and periapical tissues were healthy (Fig. 10).
Discussion
Dental trauma, when associated with the disruption of pulp
blood supply, can lead to necrosis. Circulatory breakdown
causes tissue necrosis and anaerobic conditions for opportunistic microorganisms growth, favouring the development of
inflammatory periapical lesions.1,18 When the inflammatory
periapical process involves the epithelial islands of Malassez,
these cells can proliferate and lead to the development of
periapical cysts.3 Cysts are reported to be more frequent in
males than females19,20 and the maxillary anterior teeth are
more vulnerable than mandibular teeth.21 Traditionally, periapical lesions larger than 10 mm were considered as apical
cysts whilst smaller ones were considered as granulomas.22,23
The reported incidence of cysts among periapical lesions
varies from 6 to 55%. However, an accurate histopathological
analysis of the lesions removed in toto is necessary in order to
Cyst-like periapical lesion healing in an orthodontic patient
101
Figure 8 Follow-up five years after completion of orthodontic treatment. (a) Frontal and (b) profile views show that good facial
aesthetics is maintained.
differentially diagnose either radicular cysts or apical granulomas.2
A study, based on meticulous serial sectioning of periapical lesions, has shown that the incidence of radicular cysts is
approximately 15% of all periapical lesions.3 The same
author, according to a previous study,24 differentiates ‘‘apical true cysts’’ from ‘‘apical pocket cysts’’ on the basis of
their histological characteristics and connection to the tooth
apex. The latter type, also known as ‘‘bay cysts’’, is not
completely enclosed in the epithelial lining, but is open to
the root canals.2 From a clinical and radiographic standpoint,
it is impossible to differentiate granulomas and cysts or
‘‘apical cysts’’ and ‘‘bay cysts’’.25 As concern our specific
patient, a clinical diagnosis of periapical cyst, based on
epidemiological data, clinical and radiographic results,
was possible, as previously reported by Çalişkan.26 While a
‘‘pocket’’ or ‘‘bay’’ cyst is likely to heal after conventional
nonsurgical therapy due to the removal of antigen intra-canal
source, true cysts are less likely to respond successfully to
conventional root canal therapy.27 Root canal treatment
using calcium hydroxide has resulted in more than 70%
complete healing of large periapical lesions28,29 and many
authors have previously supported the conservative nonsurgical approach to treatment.30,31
In this case report, the endodontic treatment was performed according to the nonsurgical root canal treatment
using calcium hydroxide proposed by Çalişkan.26 The decompression of the cyst, demonstrated by the conspicuous drainage through the canals, associated with the accurate
removal of intracanal irritants and with the renewal of
calcium hydroxide dressing, led to significant periapical
lesion resolution. The use of calcium hydroxide is effective
in improving histological responses thanks to its anti-inflammatory action, neutralization of acids products, activation of
alkaline phosphatase, and anti-bacterial action.32,33 These
effects seem to depend on the release of calcium and
hydroxyl ions involved in several cellular and molecular
mechanisms leading to the regeneration of periapical connective tissue.4 Endodontically treated teeth are reported to
move as readily and for the same distances as teeth with vital
pulps.34—37 Even if orthodontic movement is the main cause
of external apical root resorption,6 some authors report that
teeth with previous successful root canal treatment are less
inclined to apical root resorption.10 Although this outcome
cannot be considered conclusive,11 it has been suggested
that, owing to pulp removal, there may be loss in release of
neuropeptides which are usually triggered off by orthodontic
treatment.7—9
Baranowskyj38 investigated the healing rate of periradicular tissues in dogs after early application of an orthodontic
intrusive force on teeth that had undergone periradicular
surgery and retrograde root fillings. After comparison with
non-orthodontically-treated group, the author concluded
that the early application of orthodontic forces after surgical
endodontic treatment greatly delayed the healing process
and the specific cause was identified in tooth mobility.
Whatever the case, no comparison could be made with this
study, because of different species and protocol design, and,
to our knowledge, no previous article deals with orthodontic
movement performed during the healing phase of a cystic like
lesion after conventional endodontic treatment in humans.
Nonetheless, it has been reported that if endodontic treatment is needed, orthodontic treatment should be postponed
until completion of endodontic treatment and clinical and
radiographic evidence of healing.39
In this case report, two months and two weeks after
incisor pulp chambers were opened, and one week after
the endodontic treatment with gutta-percha canals filling
was completed, the upper arch was bonded and the active
orthodontic treatment commenced. Moreover, in order to
102
S. Paduano et al.
Figure 9 Five-year follow-up intraoral views. (a) Frontal, (b) overjet, and (c, d) lateral photographs display that post-treatment
results have been maintained. (e) Occlusal upper and (f) lower views show good teeth alignment.
complete lower arch bonding, impeded by the severe deep
bite, the first active orthodontic movements were performed
on the maxillary incisors. A 0.016 inches NiTi heat activated
wire was used to obtain the vestibular inclination of incisor
crowns that corresponded to palatal movement of root
apexes. Light forces, like those exerted by a thin NiTi heat
activated wire, with its peculiar surface characteristics,40
are necessary to avoid the risk of root resorption.41,42
Conclusions
This article presented a combined endodontic—orthodontic
treatment performed in an adult patient with Class II divison
2 malocclusion and a large periapical lesion in the maxilla
anterior region. A large periapical cyst-like lesion may
respond to nonsurgical root canal treatment. In this case
report, the orthodontic movement of incisor roots was successfully performed during the healing phase and through the
healing site of the cyst-like lesion.
Clinical relevance
Figure 10 Follow-up five years after completion of orthodontic treatment. Panoramic radiograph revealing healthy periapical tissues.
The long-term successful outcome of the present study
suggests that clinicians could perform an orthodontic tooth
Cyst-like periapical lesion healing in an orthodontic patient
103
movement without awaiting the complete healing of periapical cyst-like lesions, if appropriate root canal treatment
has been previously completed. Further studies are needed
to demonstrate the clinical suggestions of this report on large
scale.
17. Martina R, Paduano S. The translation arch. J Clin Orthod
1997;31:750—3.
18. Soares JA, Santos S, Silveira F, Nunes E. Nonsurgical treatment of
extensive cyst-like periapical lesion of endodontic origin. Int
Endod J 2006;39:566—75.
19. Bhaskar SN. Periapical lesion — types, incidence and clinical
features. Oral Surg Oral Med Oral Pathol 1966;21:657—71.
20. Shear M. Cysts of the oral regions, 3rd ed. Oxford, UK: Wright;
1992: 136—70.
21. Borg G, Persson G, Thilander H. A study of odontogenic cysts with
special reference to comparisons between keratinizing and
nonkeratinizing cysts. Swed Dent J 1974;67:311—25.
22. Lalonde ER. A new rationale for the management of the periapical granulomas and cysts. An evaluation of histopathological
and radiographic findings. J Am Dent Assoc 1970;80:1056—9.
23. Morse DR, Patnik IW, Schacterlie GR. Electroforetic differentiation of radicular cysts and granulomas. Oral Surg Oral Med Oral
Pathol 1973;35:239—42.
24. Simon JHS. Incidence of periapical cysts in relation to the root
canal. J Endod 1980;6:845—7.
25. Wood NK. Periapical lesions. Dent Clin N Am 1984;28:725—66.
26. Çalişkan MK. Prognosis of large periapical lesions following nonsurgical root canal treatment: a clinical review. Int Endod J
2004;37:408—16.
27. Nair PNR, Sjögren U, Schumacher E, Sundqvist G. Radicular cysts
affecting a root-filled human tooth: a long-term post-treatment
follow-up. Int Endod J 1993;26:225—33.
28. Sjögren U, Hagglund B, Sundqvist G, Wing G. Factors affecting
the long-term results of endodontic treatment. J Endod
1990;16:31—7.
29. Çalişkan MK, Şen BH. Endodontic treatment of teeth with apical
periodontitis using calcium hydroxide: a long-term study. Endod
Dent Traumatol 1996;12:215—21.
30. Lalonde ER, Luebke RG. The frequency and distribution of
periapical cysts and granulomas. Oral Surg Oral Med Oral Pathol
1968;25:861—8.
31. Bhaskar SN. Nonsurgical resolution of radicular cysts. Oral Surg
Oral Med Oral Pathol 1972;34:458—68.
32. Seux D, Couble ML, Hartmann DJ, Gauthier JP, Magloire H.
Odontoblast-like cytodifferentiation of human dental pulp cells
in vitro in the presence of calcium hydroxide-containing cement.
Arch Oral Biol 1991;36:117—28.
33. Siqueira Jr JF, Lopes HP. Mechanisms of antimicrobial activity
of calcium hydroxide: a critical review. Int Endod J
1999;32:361—9.
34. Huettner RJ, Young RW. The movability of vital and devitalized
teeth in the macaca rhesus monkey. Oral Surg Oral Med Oral
Pathol 1955;8:189—97.
35. Wickwire NA, McNeil MH, Norton LA, Duell RC. The effects of
tooth movement upon endodontically treated teeth. Angle
Orthod 1974;44:235—42.
36. Remington DN, Joondeph DR, Årtun J, Riedel RA, Chapko MK.
Long-term evaluation of root resorption occurring during orthodontic treatment. Am J Orthod Dentofac Orthop 1989;96:43—6.
37. Mah R, Holland GR, Pehowich E. Periapical changes after orthodontic movement of root-filled ferret canines. J Endod
1996;22:298—303.
38. Baranowskyj GR. A histological investigation of tissue response
to an orthodontic intrusive force on a dog maxillary incisor with
endodontic treatment and root resection. Am J Orthod
1969;56:623—4.
39. Tsurumachi T, Kuno T. Endodontic and orthodontic treatment of a
cross-bite fused maxillary lateral incisor. Int Endod J
2003;36:135—42.
40. D’Antò V, Rongo R, Ametrano G, Spagnuolo G, Manzo P, Martina R,
et al. Evaluation of surface roughness of orthodontic wires by
means of atomic force microscopy. Angle Orthod Sep
2012;82(5):922—8.
Conflict of interest
The authors declare no conflict of interest.
References
1. Soares JA, Queiroz CES. Patogenesia Periapical — Aspectos clı̀nicos, radiogràficos e trattamento de readsorção óssea e radicular
de originem endodôntica. J Brasil Endod 2001;2:124—35.
2. Nair PNR. New perspective on radicular cysts: do they heal? Int
Endod J 1998;31:155—60.
3. Nair PNR, Pajarola G, Schroeder HE. Types and incidence of
human periapical lesions obtained with extracted teeth. Oral
Surg Oral Med Oral Pathol Oral Radiol Endod 1996;81:93—102.
4. Soares JA, Brito-Júnior M, Silveira FF, Nunes E, Santos SMC.
Favorable response of an extensive periapical lesion to root
canal treatment. J Oral Sci 2008;50:107—11.
5. Sjögren U, Fidgor D, Persson S, Sundqvist G. Influence of infection at the time of root filling on the outcome of endodontic
treatment of teeth with apical periodontitis. Int Endod J
1997;30:297—306.
6. Woods MA, Robinson QC, Harris EF. The population distribution of
cases with root resorption. J Dental Res 1992;71A:214.
7. Bender IB, Byers MR, Mori K. Periapical replacement resorption
of permanent, vital, endodontically treated incisors after orthodontic movement: report of two cases. J Endod 1997;23:768—
73.
8. Parlange LM, Sims MR. A T. E.M. stereological analysis of blood
vessels and nerves in marmoset periodontal ligament following
endodontics and magnetic incisor extrusion. Eur J Orthod
1993;15:33—44.
9. Savino R, Paduano S, Preianò M, Terracciano R. The proteomics
big challenge for biomarkers and new drug-targets discovery. Int
J Mol Sci 2012;13:13926—48.
10. Mirabella AD, Årtun J. Prevalence and severity of apical root
resorption of maxillary anterior teeth in adult orthodontic
patients. Eur J Orthod 1995;17:93—9.
11. Hamilton RS, Gutmann JL. Endodontic—orthodontic relationship: a review of integrated treatment planning challenges.
Int Endod J 1999;32:343—60.
12. Iodice G, Danzi G, Cimino R, Paduano S, Michelotti A. Association
between posterior crossbite, masticatory muscle pain, and disc
displacement: a systematic review. Eur J Orthod 2013, April 18.
13. Marini I, Paduano S, Bartolucci ML, Bortolotti F, Bonetti GA. The
prevalence of temporomandibular disorders in patients with late
whiplash syndrome who experience orofacial pain: a case-control series study. J Am Dent Assoc 2013;144:486—90.
14. Spagnuolo G, Ametrano G, D’Antò V, Rengo C, Simeone M,
Riccitiello F, et al. Effect of autoclaving on the surfaces of
TiN-coated and conventional nickel-titanium rotary instruments. Int Endod J 2012;45:1148—55.
15. Paduano S, Cioffi I, Iodice G, Rapuano A, Silva R. Time efficiency
of self-ligating vs conventional brackets in orthodontics: effect
of appliances and ligating systems. Prog Orthod 2008;9:74—80.
16. Cioffi I, Piccolo A, Tagliaferri R, Paduano S, Galeotti A, Martina R.
Pain perception following first orthodontic archwire placement–
—thermoelastic vs superelastic alloys: a randomized controlled
trial. Quintessence Int 2012;43:61—9.
104
41. Kaley J, Phillips C. Factors related to root resorption in edgewise
practice. Angle Orthod 1991;61:125—32.
42. Vardimon AD, Graber TM, Voss LR, Lenke J. Determinants controlling iatrogenic external root resorption and repair during and
after palatal expansion. Angle Orthod 1991;61:113—22.
S. Paduano et al.
43. Ametrano G, D’Antò V, Di Caprio MP, Simeone M, Rengo S,
Spagnuolo G. Effect of sodium hypochlorite and ethylenediaminetetraacetic acid on rotary nickel-titanium instruments evaluated using atomic force microscopy. Int Endod J 2011;44:
203—9.