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Table of Contents   
ORIGINAL ARTICLE  
Year : 2014  |  Volume : 17  |  Issue : 6  |  Page : 566-570
Comparison of marginal adaptation of mineral trioxide aggregate, glass ionomer cement and intermediate restorative material as root-end filling materials, using scanning electron microscope: An in vitro study


1 Department of Conservative Dentistry and Endodontics, Narayana Dental College, Nellore, Andhra Pradesh, India
2 Department of Conservative Dentistry and Endodontics, Sri Sai College of Dental Surgery, Vikarabad, Telangana, India
3 Department of Conservative Dentistry and Endodontics, Sri Venkata Sai Institute of Dental Sciences, Mahabubnagar, Telangana, India

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Date of Submission24-Jun-2014
Date of Decision28-Aug-2014
Date of Acceptance18-Sep-2014
Date of Web Publication13-Nov-2014
 

   Abstract 

Aim: The present study compares the marginal adaption of Mineral Trioxide Aggregate (MTA), Glass Ionomer Cement (GIC) and Intermediate Restorative Material (IRM) as root-end filling materials in extracted human teeth using Scanning Electron Microscope (SEM).
Materials and Methods: Thirty single rooted human teeth were obturated with Gutta-percha after cleaning and shaping. Apical 3 mm of roots were resected and retrofilled with MTA, GIC and IRM. One millimeter transverse section of the retrofilled area was used to study the marginal adaptation of the restorative material with the dentin. Mounted specimens were examined using SEM at approximately 15 Kv and 10 -6 Torr under high vacuum condition. At 2000 X magnification, the gap size at the material-tooth interface was recorded at 2 points in microns.
Statistical Analysis: One way ANOVA Analysis of the data was carried out with gap size as the dependent variable, and material as independent variable.
Results: The lowest mean value of gap size was recorded in MTA group (0.722 ± 0.438 μm) and the largest mean gap in GIC group (1.778 ± 0.697 μm).
Conclusion: MTA showed least gap size when compared to IRM and GIC suggesting a better marginal adaptation.

Keywords: Glass ionomer cement; intermediate restorative material; mineral trioxide aggregate; root-end filling; scanning electron microscope

How to cite this article:
Gundam S, Patil J, Venigalla BS, Yadanaparti S, Maddu R, Gurram SR. Comparison of marginal adaptation of mineral trioxide aggregate, glass ionomer cement and intermediate restorative material as root-end filling materials, using scanning electron microscope: An in vitro study . J Conserv Dent 2014;17:566-70

How to cite this URL:
Gundam S, Patil J, Venigalla BS, Yadanaparti S, Maddu R, Gurram SR. Comparison of marginal adaptation of mineral trioxide aggregate, glass ionomer cement and intermediate restorative material as root-end filling materials, using scanning electron microscope: An in vitro study . J Conserv Dent [serial online] 2014 [cited 2019 Aug 22];17:566-70. Available from: http://www.jcd.org.in/text.asp?2014/17/6/566/144606

   Introduction Top


One of the key factors for a successful endodontic treatment apart from gaining a straight line access and thorough cleaning and shaping is the complete obliteration of root canal system so as to develop a fluid tight seal. [1] In an unsuccessful non-surgical treatment, surgical intervention to gain apical seal remains the next best option. [2] The surgical procedure involves the exposure of the root apex, periradicular curettage, resection and preparation of root-end followed by placement of a suitable filling. [3] A good quality root-end restorative provides an apical seal that prevents the movement of bacteria and their byproducts from the canal system both apically as well as laterally into the periapex there by enhancing the chances of healing of the periapical tissues. [4] To qualify as an ideal root-end restoration, any material should satisfy the following criteria. It should adhere to the preparation walls forming a tight seal in the root canal system, should be radiopaque, should be easy to manipulate, dimensionally stable, nonabsorbable, adhesive to dentin, non-toxic, promote healing, not be affected by presence of moisture and most importantly, be well-tolerated by the periradicular tissues. [5]

Glass Ionomer Cement (GIC) is favored as a root-end filling material because of its chemical adhesion to enamel and dentin but sealing ability was known to be adversely affected when the root-end cavities were contaminated with moisture at the time of placement of cement. [6] Biocompatibility studies have shown that GIC does not cause any adverse histological reaction in the periapical tissue.

The other commonly used and recommended root-end filling material, Intermediate Restorative Material (IRM) is Zinc Oxide Eugenol cement reinforced by addition of 20% Polymethacrylate by weight to the powder, performed quite well in leakage studies, animal studies, and retrospective human studies. [7]

Mineral Trioxide Aggregate (MTA) first described in the dental literature in 1993 by Torabinejad, [8] satisfies most of the above stated criteria as it possesses many favorable biologic and physical properties. It contains tricalcium silicate, tricalcium aluminate, tricalcium oxide, silicate oxide and other mineral oxides forming a hydrophilic powder which sets in presence of water or moisture. Several in vitro and in vivo studies have showed that MTA has potential in preventing microleakage, and has excellent biocompatibility. [9] The advantage of MTA over other root end filling materials is its ability to enhance the healing of the apical lesions and regeneration of periradicular tissues. [10]

Of the studies which are conducted to assess microleakage of these root end filling materials, assessment by degrees of dye penetration, bacterial penetration, electromechanical methods, fluid filtration technique are popular and reliable but the most effective method is the assessment of surface topography, porosity and marginal adaptation directly under higher magnification in a Scanning Electron Microscope (SEM). [3],[4],[11],[12],[13],[14],[15]

The main aim of the present in vitro study is to compare marginal adaptation of MTA, GIC and IRM as root-end filling materials in extracted human teeth using SEM.


   Materials and methods Top


Selection of teeth

Thirty single rooted, human maxillary central incisors with mature apices were randomly numbered and divided into three groups with ten teeth in each.

Root canal preparation

After decoronation, the length of each canal was determined where the size 15 K-file exited the apical foramen and working length (WL) was calculated 0.5 mm short of this position.

Biomechanical preparation of the root canals was done using Crown Down procedure to size F5 Protaper instrument (Denstply, Malliefer) in a gear reduction handpiece with 5% NaOCl (Vishal Dentocare Pvt Ltd) as irrigant. Root canals were obturated with Gutta-percha and Zinc Oxide Eugenol sealer.

Root-end preparation

Under continuous water spray, the apical 3 mm of each root was resected at 90° to the long axis of the root, with a size 701 tungsten carbide cross-cut fissure flat taper bur (SS White) using slow speed straight hand piece. Three millimeter deep root-end cavities were prepared with a 171 Tungsten Carbide tapered fissure bur in a high-speed hand piece with copious water spray. 17% EDTA was used after preparation to remove the smear layer. MTA, GIC and IRM are mixed according to manufacturer's instructions.

Placement of restorative materials began immediately following mixing, and the condensation process was complete within 1 min from the start of the mix. The restored roots were wrapped in moist gauze and stored in glass bottles for 48 hours.

Preparation of sections for SEM viewing

Transverse sections of the roots were cut with a low speed, water cooled diamond disc (Isomet, iBuehler Ltd, Germany). After discarding the initial 1 mm section, the second 1 mm transverse section of the root was used to study the marginal adaptation of the restorative material with the dentin. The sections were placed in wet gauze at 100% humidity for 12 hours prior to SEM viewing.

Scanning electron microscopy

Mounted specimens were examined using SEM (QUANTA 400, FEI, US) which was maintained at approximately 15 Kv and 10 -6 Torr under high vacuum condition. Specimen imaging was done by secondary electrons using a secondary electron detector. The surface of each specimen was viewed and photographically recorded with a charged couple device (CCD) at low magnification (50×) [Figure 1]: A1, B1, C1]. The magnification was then increased to 2000 X and for each specimen at the material-tooth inter-face, the gap size in microns was recorded at two points [Table 1]. All the samples were individually photographed at two points at 2000 X [Figure 1]: A2, A3, B2, B3, C2, C3].
Table 1: Gap width measurements in the experimental group (in micrometres)

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Figure 1: SEM images of transverse sections of GIC sample [A1: (50×), A2& A3: (2000×)], IRM sample B1: (50×), B2& B3: (2000×), and MTA samples [C1: (50×), C2& C3: (2000×)]. The gap size is measured at points 1 and 2 in the samples

Click here to view



   Results Top


Statistical analysis

One way ANOVA Analysis of the data from the experimental group was carried out with gap size as the dependent variable, and material as independent variable.

The lowest mean value of gap size was recorded in MTA group (0.722 ± 0.438 μm) followed by IRM group (0.802 ± 0.518 μm). The largest mean gap is recorded in GIC group (1.778 ± 0.697 μm) [Table 2].
Table 2: Distribution of mean of the gap size of the three materials

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Results according to one way ANOVA analysis showed that the marginal adaptation of MTA and IRM was comparable but not statistically significant. The gap size of GIC is significantly higher compared to MTA and IRM.


   Discussion Top


When non-adhesive materials are used for apical sealing, a microscopic space always exists between the restoration and the tooth which leads to microleakage. Assessment of marginal adaptation is an indirect method of determining the sealability of root-end filling materials. [13] Although in vitro tests cannot completely simulate in vivo conditions, a material that has excellent in vitro adaptation to dentine with zero gap width may achieve the best sealability. [16] SEM has been used in this study because it appears to be an efficient and acceptable method of examining features such as surface topography [4] , measuring the marginal gaps at the interface and the percentage in gap formation under higher image magnifications. [17]

In this study, we compared marginal adaptation of MTA, GIC, type II and IRM as root end filling materials in extracted human teeth using SEM.

One of the root-end filling material used in the present study, GIC bonds physico-chemically to dentine, with adequate bond strength, compressive strength and good marginal adaptation. But its sensitivity to moisture would restrict their use to cases in which thorough root-end isolation is achieved. [6]

The second root-end filling material used in the present study, IRM is routinely used as root-end filling material because its properties are not affected by powder/liquid ratio and its manipulation is easy. [18] In a histological assessment, Super-EBA and IRM were found superior to Composite resin, Glass Ionomer, and Amalgam when used as root-end filling materials. [19] In a prospective clinical study by Chong et al., IRM had 87% success rate, whereas MTA had 92% success rate when used as root-end filling materials. [20] Lindeboom et al., evaluated MTA and IRM as retrograde sealers in surgical endodontics, the difference was not statistically significant between the two filling materials. [21] Several studies have shown that MTA has better marginal adaptation than GIC, Super EBA, IRM and Amalgam. [22],[23]

MTA has been selected for this SEM study, because of its biocompatibility, superior sealing ability, good marginal adaptation and is considered as gold standard in root end filling materials. [24],[25] Studies have proved that its adaptation and physical properties are not affected by moisture.

From the biological perspective, Carr suggested that most appropriate angle of root-end resection is perpendicular to the long axis of the tooth. In this study, a resection angle of 90° to the long axis of the root was used to minimize the number of cut dentinal tubules. [26] In all the teeth used in the study, the root-end cavity, with a depth of 3 mm was prepared using a 171 tungsten carbide bur in a high speed hand piece with copious water spray. Burs were used in this study, as the crack formation, in the thinnest walls surrounding the root-end preparation was observed more with ultrasonic tips compared to burs. [27] One millimeter cross sections of the retrofilled teeth were cut using a slow speed diamond disc and the marginal adaptation of MTA, IRM and GIC with dentin was compared under High Vacuum Dry Conditions (HVDC), SEM conditions.

Statistical analysis of the present study showed that the marginal adaptation of MTA and IRM is comparable but is not statistically significant, whereas, the gap size of GIC is larger and statistically significant compared to MTA and IRM. Though GIC has showed good dentinal wall adherence, it is technique sensitive. Freshly mixed GIC shows difficulty in handling and is also sensitive to moisture. GIC may exhibit shrinkage upon setting with more voids. [28] This could be the probable reason for increased mean gap size in GIC.

In the present study, least gap was noted in MTA that is 0.722 ± 0. 43 μm followed by IRM that is, 0.81 ± 0.16 μm, with maximum gap in GIC that is, 1.77 ± 0. 69 μm. These results were comparable to the ones found by Xavier et al., which showed that the mean gap of 0.812 ± 0.550 μm between MTA Angelus and dentin. [29]

While examining the samples under SEM, to make the sample conducive, they are dried, coated with silica gel and placed in a desiccator. Later they are gold sputtered and examined. The environmental SEM used in our study, Quanta 400, features three operating modes- high vacuum dry condition (HVDC), low vacuum and environmental mode. It allows characterization of samples in their natural states without any pretreatment (fixation, drying, coating), giving a picture of true structure and composition. This ensures that samples sensitive to desiccation may be imaged without critical point drying or metal coat. Results of our study exhibited a smaller mean gap size compared to the study conducted by Shipper in which MTA showed mean gap of 1.19 ± 1.42 μm probably due to the difference in the preparation of the specimen section. Shipper carried out desiccation of the specimens to view under HVDC conditions, but in the current study, desiccation was not carried out because it doesn't simulate the clinical conditions. The desiccation also causes shrinkage of the material and thus, increasing the mean gap size. The increased sealing ability of MTA is attributable to its hydrophilic nature and expansion when cured in a moist environment. [30]

Various studies reported that MTA presented excellent apical sealing in comparison to other commonly used root-end materials. MTA showed superior marginal adaptation compared to Amalgam, Super-EBA and IRM under HDVC. [15] MTA Angelus showed better adaptation with least gap size compared to Super-EBA and Vitremer. [29] In a comparative SEM study of the marginal adaptation of Grey MTA, White MTA and Portland cement, least gap area was found in grey MTA followed by White MTA and Portland cement respectively. [31]

One way ANOVA analysis of the present study showed that MTA had better marginal adaptation to the root-end cavity wall than IRM and GIC. The mean gap of MTA was 0.722 ± 0. 43 μm followed by IRM that is, 0.81 ± 0.16 μm, with maximum gap noted in GIC as 1.77 ± 0. 69 μm. Results of this study have given a good understanding of the capability of the three root-end filling materials used, which paves a way for future clinical studies which would simulate the clinical conditions.


   Conclusion Top


Within the limitations of the present study, we can conclude that MTA showed least gap size when compared to IRM and GIC suggesting a better marginal adaptation. The marginal adaptation of MTA and IRM was comparable but the difference was not statistically significant. Varying degree of gap formation is noted at dentin filling interface in all the samples with significantly higher gap size in GIC compared to MTA and IRM. However, further long term clinical studies may be required to find the best root-end filling material.

 
   References Top

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[PUBMED]  Medknow Journal  
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[PUBMED]  Medknow Journal  
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DOI: 10.4103/0972-0707.144606

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