| Abstract|| |
Background: An ideal root canal obturation requires a complete dentinal wall adaptation of sealer and Gutta-percha combinations without any gap formations.
Aims: The aim of the study was to evaluate the dentinal wall adaptation ability of MTA Fillapex root canal sealer using stereo electron microscope (SEM).
Methods: Twenty-four, single-rooted, human maxillary incisor teeth were used. All canals were prepared with a rotary nickel-titanium (Ni-Ti) instrument to a size F3 file. Teeth divided into two equal groups and one of the experimental groups was filled with AH Plus, and the other group was filled with MTA Fillapex using Gutta-percha single cone as a core material. The roots were prepared for SEM evaluation, and serial scanning electron photomicrographs were taken at ×50, ×100, ×500, and ×1000 magnifications. The gaps between the root canal sealer and canal walls were detected and measured in coronal, middle, and apical thirds. For each section, the highest value among the detected gap formations was recorded.
Statistical Analysis: Mann-Whitney U-test, Freidman, and Wilcoxon tests were used.
Results: The statistical analysis showed no significant difference between two sealers in terms of gap formation (P > 0.05).
Conclusions: MTA Fillapex has a similar dentinal wall adaptation ability as AH Plus does.
Keywords: Adaptation; dentinal wall; gap formation; MTA Fillapex; stereo electron microscope
|How to cite this article:|
Demiriz L, Koçak MM, Koçak S, Sağlam BC, Türker SA. Evaluation of the dentinal wall adaptation ability of MTA Fillapex using stereo electron microscope. J Conserv Dent 2016;19:220-4
|How to cite this URL:|
Demiriz L, Koçak MM, Koçak S, Sağlam BC, Türker SA. Evaluation of the dentinal wall adaptation ability of MTA Fillapex using stereo electron microscope. J Conserv Dent [serial online] 2016 [cited 2019 Jul 17];19:220-4. Available from: http://www.jcd.org.in/text.asp?2016/19/3/220/181936
| Introduction|| |
Successful root canal treatment requires a complete obturation of the root canal system and the use of Gutta-percha with a sealer for root canal filling is generally accepted in endodontics.  However, it was emphasized that Gutta-percha does not adhere to the dentinal walls  and could not prevent leakage by itself.  Thus, the role of the sealer is critical for the sealing ability of obturation material, and many root canal sealers have been developed to fill residual gaps between the Gutta-percha and the canal wall. 
Epoxy resin-based root canal sealers associated to Gutta-percha have been used for many years with clinical success and they afford acceptable physical properties with adequate biological performance.  Used with Gutta-percha core materials, the AH series is the most widely used resin-based sealer system with AH Plus (Dentsply, Konstanz, Germany) being the latest of the series. AH Plus demonstrated good sealing and adaptation properties. , However, several studies ,, showed that sealing ability of this sealer was not at the ideal levels and Gutta-percha/AH Plus system could not provide complete sealing of the root canal system.
Mineral trioxide aggregate (MTA) was introduced as a root repair material in 1993.  Further studies revealed a successful sealing ability of MTA ,, and it was gradually advised for various clinical applications such as root-end filling, apexification, repair of root resorption, coronal barrier, and even as a canal filling material.  MTA Fillapex (Angelus, Londrina-Parana, Brazil) is a new MTA-based root canal sealer. MTA Fillapex contains salicylate resin, diluting resin, natural resin, bismuth trioxide, nanoparticulated silica, MTA, and pigments. According to the manufacturer, MTA Fillapex provides long-term sealing capacity and promotes the deposition of hard tissue at the root apex because of including MTA. A short survey in literature demonstrated that limited data are available about dentinal wall adaptation property of MTA Fillapex.
Stereo electron microscope (SEM) device is used in endodontics for ultrastructural analysis of the root dentin subjected to interface filling material/dentin wall and this method enables the evaluation of the presence of gaps.  The purpose of this study was to evaluate the dentinal wall adaptation ability of MTA Fillapex under SEM evaluation.
| Methods|| |
Specimen selection and root canal preparation
A total of 24, single-rooted, human maxillary incisor teeth, which were extracted because of caries or periodontal lesion, were used for this study. Soft tissue remnants and calculus were mechanically removed by using periodontal curettes and all specimens were stored in a 0.1% thymol solution. The crowns of specimens were removed by using water cooled diamond discs to obtain a standard root length of 12 mm. Two longitudinal grooves were created on the buccal and lingual surfaces of each root with a diamond bur used with a high speed, water-cooled handpiece to facilitate vertical splitting with a chisel after canal preparation. Teeth showing evidence that the groove had penetrated into the root canal or exhibiting an irregular cleavage were discarded and changed with a new specimen. The root canal length was visually established by inserting a size #15 K-type file (Dentsply-Maillefer Instruments SA, Ballaigues, Switzerland) into each canal until the tip of the file was visible at the tip of the apical foramen. The working length was established by subtracting 1 mm from the initially recorded root canal length. The canal was prepared with rotary Ni-Ti instrument (Dentsply-Maillefer Instruments SA, Ballaigues, Switzerland) to a size F3 file. The root canal was irrigated with 10 ml of 5.25% sodium hypochlorite (NaOCl) after the use of each file. The final irrigation was completed with 10 ml of 17% ethylenediaminetetraacetic acid (EDTA), 10 ml of 5.25% NaOCl, and 5 ml of saline solution, respectively. Then, the canal was dried with paper points.
The specimens were randomly divided into two equal groups (n = 12) as follows:
1. Group 1: The root canals were obturated with matched Gutta-percha cone (Dentsply Protaper Universal Gutta Percha Points, Konstanz, Germany), and MTA Fillapex sealer by using the single-cone technique
2. Group 2: The root canals were obturated with matched Gutta-percha cone and AH plus sealer by using the single-cone technique.
The excessive cones were removed at the orifice level by using a heated ball burnisher. The canal orifice was completely coated with glass ionomer-based cement (3M, Espe, Seefeld, Germany). The specimens were stored in saline solution at 37°C for 48 h.
Stereo electron microscope evaluation
The roots were split longitudinally and prepared for SEM evaluation. Each specimen was numbered and mounted on an aluminum stub, coated with gold-palladium, and examined under SEM (Quanta™ 450 FEG, FEI, Oregon, USA). Serial scanning electron photomicrographs were taken at ×50, ×100, ×500, and ×1000 magnifications. The gaps between the root canal sealer and canal walls were detected and measured in coronal, middle, and apical thirds. For each section, the highest value among the detected gap formations was taken into account and recorded. The gap sizes were recorded in millimicron (μm). The obtained results of experimental groups were compared by using Mann-Whitney U-test. In every group, three root sections were compared with each other by using Freidman and Wilcoxon tests.
| Results|| |
The statistical analysis showed no significant difference between two sealers in terms of gap formation (P > 0.05). The maximum and minimum gap size values in each section, mean values, and standard deviations for both groups are shown in [Table 1]. In Group 1, no difference was found between apical, middle, and coronal thirds of the root canals (P > 0.05). In Group 2, apical thirds demonstrated a high amount of gap formation when compared to coronal thirds, albeit significance (P = 0.028). The middle thirds did not show any significant difference when compared to coronal and apical thirds. Regardless of experimental groups, example images which were considered as well adaptation [Figure 1]a and b and gap formations [Figure 2]a and b] were shown.
|Figure 1: (a) Apical third section of a sample. An example image of well adaptation, ×100. (b) 1000× magnification of the same sample|
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|Figure 2: Middle third section of a sample. Longitudinally occurred gap formation (showed with black arrows), 100× (a) 1000× magnification of the same sample (b)|
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|Table 1: The minimum and maximum gap size values, mean values, and standard deviations for Groups 1 and 2 |
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| Discussion|| |
MTA Fillapex is a double-paste sealer containing a base and a catalyst and can be used as root canal sealer in combination with Gutta-percha according to the manufacturer. Although the manufacturer claims that MTA Fillapex has good sealing ability and biocompatibility, limited studies ,,, are available about the sealing and dentinal tubule penetration ability of MTA Fillapex. To our knowledge, dentinal wall adaptation and gap formation of MTA Fillapex were not previously evaluated under SEM magnification. On the other hand, limited studies reported comparable results about the sealing and penetrating ability of MTA Fillapex when compared to commonly used resin-based sealers. Camilleri et al.  evaluated the sealing ability of MTA Fillapex and Pulp Canal sealer using fluid filtration technique and reported that the sealing ability of both sealers was comparable. Kuçi et al.  evaluated MTA Fillapex sealer's penetration ability and stated that MTA Fillapex, compared to AH26, was associated with greater sealer penetration when used with cold lateral compaction technique. Razavian et al.  reported that MTA Fillapex and AH 26 sealers demonstrated bacterial leakage, and the sealing ability of AH26 was significantly higher than MTA Fillapex. On the other side, Ehsani et al.  compared the apical microleakage of MTA Fillapex with AH 26 and reported that MTA Fillapex provided acceptable apical seal. When the previously mentioned results were considered further in vitro and in vivo investigations are required to evaluate this newly developed root canal sealer.
Smear layer is a combination of organic and inorganic debris on the root canal wall which is formed by cutting root canal dentine with hand and rotary instruments for preparation.  Since the smear layer can act as a barrier between filling materials and the canal wall and prevents complete seal, especially for adhesive root canal sealers, the removal of smear layer remains controversial. EDTA is used for removing the smear layer and irrigation of root canals with 17% EDTA solution is adequate for a complete removal of smear layer. , Kuçi et al.  evaluated the effect of the smear layer on MTA Fillapex sealer's penetration ability and their results showed that smear layer removal was a critical factor for increasing the penetration ability of MTA Fillapex. According to this information, smear layer removal was carried out by using 17% EDTA solution in the present study.
In the present study, Ni-Ti rotary instruments were used to prepare the root canals in conjunction with Gutta-percha cones that matched the taper of the canals. Cold lateral condensation technique is still one of the most preferred root canal obturation techniques.  However, manufacturers have produced Gutta-percha cones that match the taper of canals prepared with Ni-Ti systems because of the widespread use of these systems. These matched Gutta-percha cones can be used as a single cone for filling the prepared root canal system and may provide a complete obturation in a short time. , The use of single cone or cold lateral condensation techniques are comparable  owing to these techniques' obturation abilities. Peak et al.  reported that obturated teeth with lateral condensation had better treatment results than single cone obturated teeth. On the other hand, there are several researches ,,,, which reported that single cone technique had a similar obturation ability with cold lateral condensation technique.
The properties such as hermetic obturation, dimensional stability, and effective adaptation to the canal walls, its irregularities and the entire length of the canal are expected from an ideal root canal sealer. , The aim of a resin-based root canal sealer is sealing all dentinal walls of the canal by adhesion and penetrating within the tubules, and providing a complete filling to prevent gap formations which allow the transition of bacteria and their toxins. ,
The obtained results showed that gap formations occurred in similar rates for each experimental group regardless of cement. Although MTA Fillapex sealer is an MTA-based sealer, the other component of this material is resin, so these results may be related to the lack of complete polymerization of both sealers were compared. On the other hand, the viscosity of the sealer increases during the polymerization and thus the movement capacity of molecules and reaction rate decrease.  This situation may prevent the cement move into the irregular regions of the root canal. In addition, complex morphology and geometry of the root canal may cause an extra disadvantage and may increase the restriction on the infiltration of the sealer. ,, More importantly than these factors, the polymerization shrinkage may be the main factor of occurrence these gaps. Thus, Tay et al.  stated that emerging stresses reduce the adhesion ability of root canal sealers on dentinal walls during the polymerization shrinkage and the sealer leave the canal wall, so gap formations are detected. Moreover, the length of the luting line is greater than its thickness in the root canal and that means greater polymerization shrinkage in the axial direction than in the transversal direction.  Hence, the higher longitudinal shrinkage probably contributed to the formation of gaps.
MTA Fillapex + Gutta-percha showed similar gap formation in the root sections, whereas AH Plus + Gutta-percha showed higher gap formation in the apical third when three sections were compared with each other in this experimental group. The obtained results in AH Plus group could be related to two factors. First, the high unfavorable cavity configuration factor (C-factor) inside the root canal and second the differences between base materials of evaluated sealers. According to the previous reports, ,, C-factor was highlighted because of its role in maximizing the polymerization stress of adhesive resin-based materials along the root canal walls. There is extremely high C-factor encountered in long and narrow root canals.  When the resinous components of the sealer and the narrow anatomical morphology of the apical third section of the root canal was considered, C-factor could be a reason of the high amount of gap formations in apical thirds of the root canal in AH Plus group. MTA is an advised root-end filling material because of its great sealing and marginal adaptation ability.  Hence, including MTA as a base material may have created an advantage for MTA Fillapex while the sealer was adapting on root canal walls in apical thirds.
| Conclusion|| |
MTA Fillapex showed a similar amount of gap formation when compared to AH Plus in all sections of the root canal. According to this result, MTA Fillapex has a similar dentinal wall adaptation ability as AH Plus does.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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Department of Pediatric Dentistry, Faculty of Dentistry, Bülent Ecevit University, 67600 Kozlu, Zonguldak
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2]