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Pediatric Dental Journal

journal homepage: www.elsevier .com/locate /pdj

Original Article

Apical sealing and marginal adaptation of MTAapical plug subjected to obturation after differenttime intervals

Mosa A. Torky, Lecturer of Pedodontics, Assistant Professora,b,Sukumaran Anil BDS, MDS, PhD, FDS RCPS (Glas), FICD, FPFA, Professorand Consultantc,*

a Faculty of Dental Medicine, Al-Azhar University, Egyptb College of Dentistry, Taiba University, Madina Munawara, Saudi Arabiac Department of Periodontics and Community Dentistry, College of Dentistry, King Saud University, Post Box: 60169,

Riyadh 11545, Saudi Arabia

a r t i c l e i n f o

Article history:

Received 9 January 2014

Received in revised form

3 August 2014

Accepted 11 September 2014

Available online 28 October 2014

Keywords:

Sealing ability

Marginal adaptation

Mineral trioxide aggregate

Root-end filling materials

Apexification

Obturation

* Corresponding author. College of DentistryE-mail addresses: drsanil@gmail.com, KsURL: http://www.perio.in

http://dx.doi.org/10.1016/j.pdj.2014.09.0040917-2394/Copyright © 2014 The Japanese So

a b s t r a c t

Objective: This study compares the apical seal and marginal adaptation of an MTA apical

plug in incisors obturated at three time intervals.

Method: Forty extracted central incisors were prepared with wide apex and divided into 4

groups. The first group was obturated with gutta-percha and AH26 sealer, which served as

the positive control. The second group received an MTA apical plug and obturation

immediately. In the third and fourth group, obturation was delayed for 48 h and one week,

respectively. The apical seal was assessed by the dye penetration method and quantified

using image analysis software. The marginal adaptation was studied using SEM.

Results: A significantly better apical seal was observed in the groups obturated after 48 h

and one week after MTA placement. The dye penetration did not show any significant

changes between the 48 h and one week groups. The marginal adaptation also showed a

minimal gap in the control and in samples with delayed obturation.

Conclusion: Based on this in vitro study, delaying obturation for 48 h after setting the MTA is

recommended for maximum apical sealing and marginal adaptation.

Copyright © 2014 The Japanese Society of Pediatric Dentistry. Published by Elsevier Ltd. All

rights reserved.

1. Introduction

Dental injuries in immature permanent teeth often result in

endodontic complications. The absence of an apical

, King Saud University, Pucod@gmail.com (S. Anil)

ciety of Pediatric Dentist

constriction and the divergent apical architecture of the root

canal hamper complete debridement, canal disinfection and

obturation [1,2]. The apexification technique using calcium

hydroxide is still the most widely accepted technique for

ost Box: 60169, Riyadh 11545, Saudi Arabia. Fax: þ966 1 467 9017..

ry. Published by Elsevier Ltd. All rights reserved.

p e d i a t r i c d e n t a l j o u r n a l 2 4 ( 2 0 1 4 ) 1 6 7e1 7 2168

managing such conditions. However, drawbacks such as cor-

onal micro-leakage, tooth susceptibility to fracture, and mul-

tiple session treatment necessitate the development of an

alternative method for managing the situation [3].

Mineral trioxide aggregate (MTA) has been proposed as an

alternative material for apexification by combining biocom-

patibility and a bacteriostatic action with favorable sealing

ability when used to repair pulp chamber perforations or as a

root-end filling material [2,4,5]. MTA is non-resorbable, has

good biocompatibility and low cytotoxicity, and promotes

dental pulp and periradicular tissue regeneration. MTA has a

pH of 12.5 after setting, which is similar to the pH of calcium

hydroxide and this characteristic may impart some antimi-

crobial properties [6]. Studies have shown that MTA stimu-

lates natural dentin repair at pulpal exposure sites during

direct pulp capping [6]. Furthermore, MTA has relatively less

micro-leakage and can stimulate tissue regeneration, when it

is in direct contact with pulp and periradicular tissues [7].

MTA has been successfully used as an apical barrier in the

treatment of teeth with necrotic pulps and open apexes

[2,8e11].

Several studies have shown that MTA can be used for one

visit apexification [12]. MTA provides scaffolding for the for-

mation of hard tissue and has the potential to provide a better

biological seal. MTA apexification is a viable option for treat-

ing immature teeth with necrotic pulps and should be

considered as an effective alternative to calcium hydroxide

[8,13].

Although MTA has several advantages, one of the main

drawbacks is the long setting time, which could jeopardize the

sealing ability and marginal leakage [14]. So far, only limited

studies have been conducted to evaluate the setting ofMTA on

the quality of themarginal adaptation and sealing. Hence, the

present study evaluates the apical sealing and adaptation of

open apexes that were obturated immediately, 48 h and 1

week after placing an MTA apical plug in an in vitro model.

2. Materials and methods

The study was approved by the Institutional Review board of

the Al-Azhar University, College of Dentistry, Egypt. A total of

40 freshly extracted permanent maxillary central and lateral

incisor teeth were used in this study. Teeth with a single non-

calcified canal, as confirmed by radiographs taken from

bucco-lingual and mesio-distal views, were selected. Any

tooth with abnormalities, such as internal resorption, oblit-

eration, pulp stones, cracks and fractures, were excluded and

replaced. The selected teeth were stored in normal 0.9% saline

solution during the experiment. Then, they were examined

with a magnifying glass to discard the specimens with any

cracks or fractures.

2.1. Tooth preparation and open apex simulation

Preparation of the access cavities were done using a water-

cooled round bur in a high-speed handpiece (NSK, Japan).

The working length was determined by placing a size 30 K-file

(Dentsply-Maillefer Instruments SA, Ballaigues, Switzerland)

in the canal until it was visible at the apical foramen and

subtracting 1 mm from this measurement. The canals were

prepared with Gates Glidden Burs (Dentsply-Maillefer In-

struments SA, Ballaigues, Switzerland) sizes 4, 3, and 2 for the

coronal third. The glide path was established by hand filling

with K-files sizes 15, 20, and 25 to a full working length.

Instrumentation was completed with a high torque motor at

300 rpm and 0.06 Taper Profile nickeletitanium rotary in-

struments (Dentsply Tulsa Dental, Tulsa, Oklahoma, USA).

The apical third of the canals were instrumented up to size

120 to simulate open apex teeth. To simulate immature teeth,

the canals were further enlarged using peeso reamers (No.

1e6, Mani, Japan) with gentle pressure and under copious

water spray until the No. 6 peeso could be passed beyond the

apex [15]. Irrigation was carried out using 2 ml of 2.5% sodium

hypochlorite (NaOCl). After preparation, each canal was irri-

gated with 5 ml of 17% EDTA (Calcinase EDTA, lege artis,

Dettenhausen, Germany) for 3 min to remove the smear layer,

followed by 2 ml of 2.5% sodium hypochlorite solution. The

final irrigationwas performedwith 5ml of distilled water. The

canals were then dried with paper points.

The 40 prepared teeth were divided randomly into 4

groups.

Group 1: Obturated with gutta-percha and AH26 sealer.

Group 2: An MTA apical plug (ProRoot; Tulsa Dental, Tulsa,

OK, USA) of approximately 5 mm thickness was placed.

The canal was sealed with gutta-percha and AH26 sealer

immediately after the initial setting of white MTA apical

plugs as per manufacturer recommendations.

Group 3: An MTA apical plug (ProRoot; Tulsa Dental, Tulsa,

OK, USA) of approximately 5 mm thickness was placed.

The canal was sealed with gutta-percha and AH26 sealer

after 48 h of MTA setting.

Group 4: An MTA apical plug (ProRoot; Tulsa Dental, Tulsa,

OK, USA) of approximately 5 mm thickness was placed.

The canal was sealed with gutta-percha and AH26 sealer

after 1 week.

The obturation of all specimens was performed through

active lateral condensation technique. In this technique, the

main gutta-percha point was advocated as the endodontic

sealer and introduced into the root canal. Following that,

secondary points were added up for the complete filling of the

root canals.

2.2. Micro leakage

Following obturation, the coronal cavity was sealed with glass

ionomer cement (GC Fujirock EP; GC Europe NV, Leuven,

Belgium). The root segments from all groups were double-

coated with nail varnish except at the apical 3 mm. The

coated roots were suspended in 2% methylene blue dye in a

petridish and incubated at 37 �C with 100% humidity for 48 h.

The teeth were then sectioned longitudinally along the

long axis in the bucco-lingual direction through the center of

the root. To prevent any damage to the inside of the canal, the

sectioning was done with water cooled diamond disc along

the root, short of reaching the obturation material, thereby

creating a stress canal. A chisel was used to wedge and split

the teeth.

Table 1e The apical dye penetration of incisors obturatedwith an MTA apical plug and gutta-percha immediately,after 48 h and after one week.

Materials Micro leakage (mm)

(n ¼ 10) Mean ± SD

GP þ AH26 3.18 ± 0.82

MTA (immediate) 1.06 ± 0.27

MTA (48 h) 0.4 ± 0.11

MTA (1 week) 0.34 ± 0.1

Fig. 2 e Maxillary central incisor obturated with gutta-

percha and AH24 sealer showing apical dye penetration.

p e d i a t r i c d e n t a l j o u r n a l 2 4 ( 2 0 1 4 ) 1 6 7e1 7 2 169

Linear dye penetration was determined using a stereo-

microscope (Carl Zeiss, Oberkochen, Germany). The dye

leakage was measured with a millimeter scale from the apical

constriction to the longest point of dye penetration along the

canal walls and obturation material itself. Measurements

were performed twice each by two independent examiners

and repeated jointly only if disagreement occurred in reaching

consensus.

2.3. Marginal adaptation

The marginal adaptation was evaluated in the 30 segments.

These segments were gold-sputtered and analyzed with SEM.

For evaluation of the marginal adaptation of the root canal

filling, photographs were taken at �2000 magnifications and

analyzed with an image analysis software (The imageJ soft-

ware, National Institutes of Health, Bethesda, Maryland). The

Fig. 1 e The apical dye penetration of incisors obturated

with an MTA apical plug and gutta-percha immediately,

after 48 h and after one week.

extent of the gap between the MTA apical plug and� radiculardentin was observed, and the gap-free and gap-containing

area along the filling-dentin interface was evaluated.

2.4. Statistical analysis

Statistical analysis of the data was performed using the

GraphPad InStat® software (InStat, GraphPad InStat, Inc. San

Diego, CA). Differences between the three study groups for all

variables were determinedwith One-wayAnalysis of Variance

(ANOVA). When an overall ANOVA showed statistical signifi-

cance, post hoc testing (TukeyeKramerMultiple Comparisons

Test) was performed to explore the differences between any

two groups. p-values <0.05 were considered significant.

3. Results

The highest mean value of apical dye penetration was recor-

ded with teeth obturated with gutta-percha and AH24 sealer

without an apical plug, and the lowest value was recorded

with teeth obturated with an MTA apical plug, gutta-percha

Fig. 3 e Maxillary central incisor with an MTA apical plug

that was obturated after 48 h showing minimal dye

penetration.

p e d i a t r i c d e n t a l j o u r n a l 2 4 ( 2 0 1 4 ) 1 6 7e1 7 2170

and AH24 sealer after one week. One way analysis of variance

(ANOVA) revealed that the difference was statistically signif-

icant (p � 0.01).Tukey's post hoc test revealed that the differ-

ence between the MTA apical plug groups at 48 h and 1 week

was statistically non-significant at p > 0.01 (Table 1, Fig. 1).

Comparing the apical dye penetration of theMTA groups at

different periods showed that the greatest mean value of dye

penetration was recorded in the immediate group, while the

lowest valuewas recorded in the group obturated after 1week.

One way analysis of variance test revealed that the difference

was statistically significant (p < 0.01). Tukey's post hoc test

revealed that the difference between the MTA group at 48 h

and 1 weekwas not statistically significant (Table 1, Figs. 1e3).

3.1. Scanning electron microscopic observations

SEM was used to qualitatively assess the mechanisms

responsible for the leakage, by evaluating the adaptation of

the MTA apical plug to the dentinal walls. The present study

found that delayed MTA apical plug and gutta-percha filling

had better sealing ability than the control and immediate

obturation. The results were also confirmed by the SEM. Ex-

amination of the photomicrographs of the samples demon-

strated variable gaps at the dentin-MTA interfaces. Delayed

obturation presented much smaller gaps at the dentin-MTA

apical plug interface than the immediate MTA apical plug

(Figs. 4e6).

4. Discussion

Endodontic treatment of traumatized immature teeth with

periapical lesions is performed by inducing apical closure by

apexification and then forming an adequate seal in the root

Fig. 4 e Scanning electron microscope (SEM) of the apical

third of the incisor showing a gap area between the MTA

apical plug and the radicular dentin with immediate

obturation.

apex. Although calcium hydroxide is the first choice for an

intra-canal dressing in apexification; some drawbacks such as

coronal micro-leakage, tooth susceptibility to fracture, and

multisession treatments have led to the exploration of

appropriate alternatives [6,16,17]. MTA-based sealers have

been reported to be biocompatible and can stimulate miner-

alization and encourage apatitelike crystalline deposits along

the apical thirds of canal walls [18].

Several methods are used to determine the sealing ability

of apical plugs, such as polymicrobial leakage, linear dye

leakage, diaphanization, fluid filtration, radioisotope labeling,

and the electrochemical method [19]. In this study the meth-

ylene blue dye solution method was selected because of its

advantages over the other tracing materials, including its

solubility in water, ability to easily penetrate into the water

compartment of the tooth, non-absorbability into the dentinal

matrix or apatite crystals and ability to penetrate further than

any isotope traces.

The apical sealing ability of MTA has been shown to exhibit

good sealing ability [20e22]. Because the setting time ofMTA is

longer in the current study, the sealing ability was tested

against the delayed obturation of the root canal. The obtura-

tion of the root canal after 48 h showed maximal sealing

ability and adaptation compared to immediate obturation.

Obturation of the root canal after 1 week did not show any

significant improvement in the apical sealing of MTA

compared to obturation after 48 h. The assumption is that

obturation after 48 h showed better sealing ability of the MTA

plug compared to immediate obturation.

MTA has been shown to prevent micro-leakage and to

stimulate tissue regenerationwhen in direct contactwith pulp

and periradicular tissues [23]. Clinical studies of open apex

teeth obturated with MTA in one appointment demonstrated

healing rates that ranged from 81 to 100% [24,25], with 94.1%

Fig. 5 e SEM of the apical third of incisor showing a

minimal gap between the MTA apical plug and radicular

dentin that was obturated after 48 h.

Fig. 6 e SEM of the apical third of incisor showing a

minimal gap between the MTA apical plug and the

radicular dentin that was obturated after one week.

p e d i a t r i c d e n t a l j o u r n a l 2 4 ( 2 0 1 4 ) 1 6 7e1 7 2 171

clinical success and 76.5% radiographical success when used

as an apical plug in permanent incisors [26,27]. The hydro-

philic nature of the particles from MTA powder allows its use

even in the presence of moisture contamination, specifically

from blood, and does not affect its sealing ability, which is

often a problem with other materials typically used in apex-

ification [28].

The setting time of MTA has been reported to range from

75min to 72 h for an initial set and 21 days for complete curing

[29,30]. Hence, a two-visit procedure is advocated to obtain

good apical sealing of the material [31].

5. Conclusion

Within the limitations of this in vitro study it can be assumed

that the two-visit protocol is ideal for obtaining maximum

apical sealing and marginal adaptation for MTA. Further

studies in a clinical setting are essential to reinforce the cur-

rent observations in the in vitro model.

Conflict of interest

None.

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