Basic Research—Technology

Influence of Ultrasonic Activation of 4 Root Canal Sealerson the Filling QualityBruno Martini Guimar~aes, DDS, MSc, Pablo Andr�es Amoroso-Silva, DDS, MSc,Murilo Priori Alcalde, DDS, Marina Ang�elica Marciano, DDS, MSc,Flaviana Bombarda de Andrade, DDS, PhD, and Marco Antonio Hungaro Duarte, DDS, PhD

Abstract

Introduction: The purpose of this study was to evaluatethe effects of ultrasonic activation on the filling quality (in-tratubular sealer penetration, interfacial adaptation, andpresence of voids) of 4 epoxy resin–based sealers.Methods: Eighty-four extracted human canines weredivided into 4 groups (n = 20) according to the sealerused to obturate the root canals instrumented with F5 Pro-Taper instruments (50/05) (Dentsply Maillefer, Ballaigues,Switzerland). The canals were filled by the lateral compac-tion technique. Previously, the sealers were labeled withrhodamine B dye to allow analysis under a confocal micro-scope. At the time of obturation, the specimens weredivided again into 2 groups (n= 10) according to the ultra-sonic activation of the sealers: ultrasonically activated andnonultrasonically activated groups. All samples weresectionedat 2, 4, and6mmfrom theapex. Thepercentagesof voids, gaps, and dentinal sealer penetration segments ofthe canal were analyzed. Results: Regarding the sealerpenetration segments, there was a significant increasefor the AH Plus (Dentsply Maillefer), Acroseal (Specialit�esSeptodont, Saint Maur-des-Foss�es, France), and Sealer 26(Dentsply Maillefer) at the 4-mm level and the AH Plusand Sealer 26 at the 6-mm level with ultrasonic activation(P < .05). Concerning the gaps, the ultrasonic activationpromoted a smaller presence for all sealers at the 4- and6-mm levels (P < .05). No statistical significant differenceswere found for the percentages of voids (P < .05).Conclusions: The use of ultrasonic activation of anepoxy resin–based sealer promoted greater dentinalsealer penetration and less presence of gaps. (J Endod2014;40:964–968)

Key WordsConfocal microscopy, epoxy resin sealers, root canalfilling, ultrasound

From the Department of Operative Dentistry, Endodonticsand Dental Materials, Bauru School of Dentistry, University ofS~ao Paulo, Bauru, S~ao Paulo, Brazil.

Address requests for reprints to Dr Bruno MartiniGuimar~aes, Al Oct�avio Pinheiro Brisolla, 9-75-CEP 17012-901,Bauru School of Dentistry, University of S~ao Paulo, Bauru, SP,Brazil. E-mail address: brunomgui@usp.br0099-2399/$ - see front matter

Copyright ª 2014 American Association of Endodontists.http://dx.doi.org/10.1016/j.joen.2013.11.016

964 Guimar~aes et al.

The complete sealing of the root canal system after a biomechanical procedure candetermine the long-term success of an endodontic treatment by preventing oral path-

ogens from colonizing and reinfecting the root and periapical tissues (1, 2). Becausegutta-percha does not adhere to the dentinal walls, the sealer must fill the irregularitiesand the dentinal tubules of the root canal system.

Epoxy resin–based sealers were introduced in endodontics by Schroeder (3) andhave since been used because of their reduced solubility (4), apical seal (5), andmicroretention to the root dentin (6). One of these sealers is AH Plus (Dentsply Mail-lefer, Ballaigues, Switzerland), which has been extensively evaluated for its physico-chemical properties, biological response, and interfacial adaptation (7–9). TheAdseal (Meta Biomed, Cheongju, South Korea) is another epoxy resin sealer withreports in the literature about its radiopacity value and physical properties (9, 10).Acroseal (Specialit�es Septodont, Saint Maur-des-Foss�es, France) is a sealer thatcontains 28% calcium hydroxide in its composition. Previous studies have shown itssealing ability, antimicrobial activity against Enterococcus faecalis, and adaptationto the root canal walls (9, 11, 12). Sealer 26 (Dentsply Maillefer) is an epoxy resin–based material containing calcium hydroxide and has also shown good sealingability and antimicrobial activity (13, 14).

Ultrasound is an instrument that was first introduced to endodontics by Richmanin 1957. Currently, it has been widely used in different endodontic procedures, rangingfrom coronal opening to endodontic surgery (15). A greater agitation of irrigatingsolutions promoted by ultrasound intensifies the penetration in an area of anatomiccomplexity such as the dentinal tubules and consequently improves the cleaning ability(16). The activation of root canal sealers can possibly favor its penetration inside thedentinal tubules, providing an increase in sealability (17) and antimicrobial effects(18). The effects of ultrasonic activation of the sealer into the root canal and the fillingquality have not been explored sufficiently.

The aim of this study was to evaluate the effect of ultrasonic activation on 4 epoxyresin–based sealers regarding their filling quality. The null hypothesis that was tested isthat ultrasonic activation improves the filling quality of epoxy resin–based sealers.

Materials and MethodsEighty-four maxillary human canines with a root curvature less than 5� were used

(19). The ethics committee approved the use of extracted teeth for the research (CEP079/2011). The crowns were removed at the cementoenamel junction using a 0.3-mmlow-speed diamond saw (Isomet, Buehler, Lake Bluff, IL), and the root canal length wasestablished at 15 mm. The working length was established by measuring the penetrationof a size 10 K-file (Dentsply Maillefer) until it reached the apical foramen and then sub-tracting 1 mm. Root canal shaping was performed using ProTaper rotary instruments(DentsplyMaillefer) at the working length until a F5 (50.05) instrument. After the use ofeach instrument, the canals were irrigated using 2 mL 2.5% sodium hypochlorite.Passive ultrasonic irrigation was performed at the end of the shaping as described byvan der Sluis et al (20). A final flush of 2 mL 17% EDTA (pH = 7.7) (Biodinamica,Ibipor~a, Paran�a, Brazil) was applied for 3 minutes to eliminate the smear layer.Then, the canals were washed with 5 mL saline solution and dried with paper points(Dentsply Maillefer).

JOE — Volume 40, Number 7, July 2014

Basic Research—Technology

The specimens were randomly divided into 4 groups (n = 20)

according to the sealer used to obturate the root canals:

Group 1: AH Plus (Dentsply Maillefer)Group 2: Acroseal (Septodont, Saint Maur des Fosses, France)Group 3: AdSeal (Meta, Biomed, Cheongju, South Korea)Group 4: Sealer 26 (Dentsply Maillefer)

The sealers were manipulated according to the manufacturer’s in-structions. To allow visualization under a confocal laser microscope(TCS-SPE; Leica Microsystems GmbH, Mannheim, Germany), thesealers were mixed with fluorescent rhodamine B dye (Sigma-Aldrich,St Louis, MO) to an approximate concentration of 0.1% (21). Thesealers were placed in each root canal by using a size 30 rotary lentulospiral (Dentsply Maillefer), maintaining the instrument 4 mm from theapex. Then, the specimens were divided into 2 groups (n= 10) accord-ing to the ultrasonic activation of the sealers: ultrasonically activated (A)and nonultrasonically activated (NA) groups. The activation in group Awas performed using a size A nickel-titanium finger spreader (DentsplyMaillefer) adapted into an ultrasonic device (Jet-Sonic Four Plus; Gna-tus, Ribeir~ao Preto, SP, Brazil) in ‘‘endo’’ mode (50% potency) using ano. A-120 insert (Gnatus) (Fig. 1). Because the ultrasonic oscillates in asingle plane, the spreader was activated for 20 seconds in the buccolin-gual direction and another 20 seconds in the mesiodistal direction ofthe root canal, 2 mm short of the working length as a standardizationprocedure. Next, a 50.02 gutta-percha cone (Dentsply Maillefer) wasinserted into the full working length, and the root canal obturationwas completed using the lateral compaction technique with a size Bfinger spreader (Dentsply Maillefer) inserted 2 mm short of the work-ing length and accessory gutta-percha points size 20.02 (Dentsply Mail-lefer). The cervical portion of the specimens was sealed using aprovisional filling material (Coltosol, Coltene, Switzerland). The speci-mens were stored in 100% humidity at 37�C for 1 week to allow thesealers to set.

Voids Area, Interfacial Adaptation (Gaps),and Segment of Sealer Penetration

The samples were sectioned using a 0.3-mm Isomet saw (Buehler,Lake Bluff, IL) at 200 rpm with continuous water cooling to prevent fric-tional heat. Horizontal sections were performed at the 2-, 4-, and 6-mmlevels from the apical foramen and polished with sandpaper (Politriz;

Figure 1. Finger spreader adapted into an ultrasonic device using a no. A-120insert.

JOE — Volume 40, Number 7, July 2014

Arotec, Cotia, SP, Brazil). To calculate the void area (mm2) percent-ages, a stereomicroscope (Stemi 2000C; Carl Zeiss, Jena, Germany)and the Axiovision software (Carl Zeiss) were used (Fig. 2A). First,the total area of each cross-section image of the canal and the visiblevoids were measured. With both values obtained, the percentage ofvoids in relation to the total area of each canal section was calculated.

The segments of the root canal in which the sealer penetrated intothe dentinal tubules, and the interfacial adaptation (gaps) were analyzedon an inverted Leica TCS-SPE confocal laser scanning microscope(Leica Microsystems GmbH) by the similar method described byMoon et al (22). For the correct visualization of all images, the sectionswere analyzed 10mmbelow the surface using the 10� lens. The respec-tive absorption and emission wavelengths for the rhodamine B were setto 540 and 590 nm, respectively. Then, the images were recorded at100� magnification using the fluorescent mode to a size of 1024 �1024 pixels and a scale set to 100 mm (Fig. 2B). Analysis of all imageswas performed with the Image J V1.46r software (National Institutes ofHealth, Bethesda, MD). The total circumference of the canal was ob-tained first. Then, segments of sealer penetration into the dentinal tu-bules and interfacial adaptation (gaps) of the total circumferencewere measured, and the values were converted into percentages(Fig. 2C and D).

Statistical AnalysisBecause of the absence of normal distribution, which was

observed using the Shapiro-Wilk test. Statistical analysis was performedby using the nonparametric Kruskal-Wallis and Dunn tests (P < .05).The nonparametric Mann-Whitney test was used to analyze the influenceof ultrasonic activation individually in each sealer (P < .05).

ResultsMedian and range of voids, interfacial adaptation (gaps), and

dentinal sealer penetration segments of the canal can be found inTable 1. With regard to the sealer penetration segments, there was a sig-nificant increase for the AH Plus (Fig. 2E and F), Acroseal, and Sealer 26at the 4-mm level, and the AH Plus and Sealer 26 at the 6-mm level whenthe ultrasonic activation was performed (P < .05). Regarding the gaps,the ultrasonic activation promoted a smaller presence for the AH Plus atthe 2-mm level and for all sealers at the 4- and 6-mm levels (P< .05). Thevoids percentage revealed no significant differences between the A or NAgroups at all levels (P < .05).

DiscussionThe null hypothesis tested was confirmed because the ultrasonic

activation improved the filling quality of the 4 epoxy resin–basedsealers. The transmission of acoustic microstreaming energy from anoscillating file by the use of ultrasonic activation can promote the pene-tration of irrigants in an area of anatomic complexity and the dentinaltubules, resulting in a greater cleaning ability (16). With regard to theintracanal medication, Duarte et al (23) analyzed the influence of ultra-sonic activation of calcium hydroxide pastes on the pH and calciumrelease in simulated external root resorptions. The authors showedthat the ultrasonic activation favored a higher pH level and calciumrelease describing that ultrasonic activation could promote a greatertubular penetration of the calcium hydroxide pastes. In accordancewith the results mentioned previously, the present study showed thatthe ultrasonic activation also favored a greater dentinal sealer penetra-tion and improved the interfacial adaptation between the sealer and theroot canal walls, which can promote a higher contact and confinementof microorganisms present in the dentinal tubules (22).

Ultrasonic Activation of 4 Root Canal Sealers 965

Figure 2. (A and B) Representative correlative stereomicroscopic/confocal pictures of canal filled with Acroseal sealer and lateral compaction technique. A thinlayer of sealer is evident just in the confocal picture, which promotes a clear visualization of adaptation without evidence of voids and gaps. (C and D) Segments ofthe root canal in which the sealer penetrated into the dentinal tubules (white dots) and an evident gap (arrows) at the interfacial adaptation, respectively. (E and F)Representative picture at 4-mm sections of canal filled with AH Plus ultrasonically and nonultrasonically activated, respectively. A remarkable dentinal sealer pene-tration is evident when the ultrasonic activation was promoted.

Basic Research—Technology

The percentage of segments in which the sealer penetrated into thedentinal tubules may be more meaningful and clinically relevantcompared with the maximum depth of sealer penetration (24), and itcan be considered beneficial for preventing reinfection because ofthe sealer’s antibacterial activity and by locking the residual microor-ganisms into the dentinal tubules (22, 25). Additionally, it has beensuggested that the sealer inside the tubules promotes a mechanicalinterlocking, improving the material retention (22, 26). Meanwhile,De-Deus et al (27) reported that there was no significant correlationbetween the intratubular sealer penetration and the sealing ability. Inthis study, the sealers were placed by a rotary lentulo spiral for stan-

966 Guimar~aes et al.

dardization procedures. A previous study showed that the distributionof sealer in the canal walls is not affected by the sealer placementmethod (28), which support the hypothesis that the ultrasonic activa-tion of the sealer could enhance the root filling quality.

AH Plus, Acroseal, and Sealer 26 presented a significant increaseof segments of sealer penetration at the 4-mm level. AH Plus and Sealer26 also had a significance difference at the 6-mm level when ultrasonicactivation was performed. No significant differences were found at the2-mm level. These findings are similar to other studies (24, 29, 30),which showed that the sealer penetration in the dentinal tubules wassignificantly greater in the coronal and middle levels of the root canal

JOE — Volume 40, Number 7, July 2014

TABLE1.

MedianandRange

ofVoids,InterfacialAdaptation(gaps),andDentinalSealerPenetrationSegm

entsoftheCanal(PS)

Voids2mm

(%)

Voids4mm

(%)

Voids6mm

(%)

Gap

2mm

(%)

Gap

4mm

(%)

Gap

6mm

(%)

PS2mm

(%)

PS4mm

(%)

PS6mm

(%)

AHPlus

A0.71(0–1

3.3)a

0.0

(0–4

.57)a

0.69(0–2

4.3)a

0.0

(0–1

6.3)a

0.0

(0–1

4.5)a

0.0

(0–2

4.1)a

0.0

(0–2

1.7)a

36.5

(25.0–6

7.9)a

55.4

(39.3–1

00)a

NA

0.0

(0–9

.54)a

0.35(0–2

.15)a

0.39(0–5

.97)a

7.96(0–3

7.1)b

6.45(0–3

5.1)b

10.9

(0–3

6.3)b

0.0

(0–6

3.0)a

28.6

(0–5

5.9)b

36.5

(0–7

1.3)b

Acroseal

A0.0

(0–1

.35)a

0.86(0–5

.88)a

0.26(0–1

.65)a

5.59(0–1

8.1)a

0.0

(0–4

.62)a

0.0

(0–7

.31)a

14.2

(0–4

6.8)a

36.7

(0–7

7.7)a

53.3

(27.1–8

7.8)a

NA

0.46(0–2

.27)a

0.37(0–2

.25)a

0.27(0–1

4.8)a

11.5

(0–3

8.7)a

12.8

(0–3

5.3)b

3.79(0–2

3.2)b

0.0

(0–1

2.7)a

3.50(0–4

2.5)b

40.9

(18.1–1

00)a

ADSe

al

A0.69(0–1

2.2)a

0.26(0–0

.96)a

0.29(0–8

.88)a

2.83(0–2

7.2)a

0.0

(0–5

.78)a

0.0

(0–7

.72)a

0.0

(0–0

)a41.8

(0–7

7.8)a

30.0

(3.86–9

7.4)a

NA

0.68(0–1

5.7)a

0.14(0–0

.70)a

0.16(0–1

3.4)a

5.25(0–3

3.5)a

3.86(0–5

0.8)b

10.4

(0–3

0.7)b

0.0

(0–0

)a0.0

(0–1

5.4)a

23.6

(0–7

7.3)a

Sealer26

A0.0

(0–1

3.6)a

0.0

(0–1

.41)a

0.30(0–2

.19)a

0.0

(0–9

.61)a

0.0

(0–8

.39)a

0.0

(0–8

.53)a

0.0

(0–3

5.5)a

39.0

(12.2–1

00)a

76.0

(0–1

00)a

NA

0.83(0–1

7.1)a

0.53(0–3

.90)a

0.0

(0–1

.66)a

1.37(0–1

9.9)a

7.37(0–2

4.3)b

7.80(0–2

8.0)b

0.0

(0–1

2.2)a

20.8

(0–5

1)b

49.7

(0–1

00)b

Adifferentletterineach

columnrepresentsstatisticaldifferences

betweentheultrasonicallyactivated

(A)andnonultrasonicallyactivated

(NA)

groups

foreach

sealer

(P<.05).

Basic Research—Technology

JOE — Volume 40, Number 7, July 2014

than the apical (31). This could be because of the fact that a superiorremoval of the smear layer in the coronal andmiddle levels and the inef-fective delivery of irrigant to the apical region of the canal occurs (32).Another factor may be that the apical level contains less tubules, andwhen present, the diameter is smaller or they are more frequentlyclosed (33).

In relation to the interfacial adaptation (gaps), none of the groupsshowed a total adaptation to the root canal walls. However, the ultra-sonic activation promoted a smaller presence of gaps for the AH Plusat the 2-mm level and for all sealers at the 4- and 6-mm levels with astatistical significance (P < .05). The present results are relevantbecause the gap regions can increase potential microbial leakage(34). Epoxy resin–based sealers like AH Plus are correlated with ahigher adhesion to dentin and gutta-percha, and this might explainthe appropriate interfacial adaptation of the tested sealers (35). Theseresults are in agreement with previous studies (9, 34).

The stereomicroscope analysis revealed voids at all groups (A andNA) and levels, presenting no significant difference between them (P <.05). The ultrasonic activation of the sealer did not seem to influence thepresence of voids, which probably is more related to the inability of thelateral compaction technique to allow a homogeneous layer of sealer onthe entire root canal wall (36).

ConclusionsThe use of ultrasonic activation of an epoxy resin–based sealer

promoted greater dentinal sealer penetration and less presence of gaps.

AcknowledgmentsSupported by the State of S~ao Paulo Research Foundation

FAPESP (2011/03973-4).The authors deny any conflicts of interest related to this study.

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