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 Table of Contents  
ORIGINAL ARTICLE
Year : 2017  |  Volume : 9  |  Issue : 1  |  Page : 8-11

Comparative evaluation of fracture resistance of endodontically treated teeth with epoxy resin-based sealers AH plus and mineral trioxide aggregate fillapex: An in vitro study


Department of Conservative Dentistry and Endodontics, Inderprastha Dental College, Ghaziabad, Uttar Pradesh, India

Date of Web Publication6-Mar-2017

Correspondence Address:
Paridhi Garg
Inderprastha Dental College, Sahibabad, Ghaziabad, Uttar Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/IJDS.IJDS_83_16

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  Abstract 

Aim: This study aims to evaluate and compare the fracture resistance of endodontically treated teeth obturated with gutta-percha using two sealers, AH Plus, and mineral trioxide aggregate (MTA) Fillapex. Materials and Methods: Twenty single-rooted mandibular premolars, decoronated at cementoenamel junction, were divided into two groups (n = 10 each). Cleaning and shaping of root canals were done using ProTaper rotary files and 3% sodium hypochlorite irrigation. Obturation was done using sealers, AH Plus (Dentsply, Germany) in Group 1 and MTA Fillapex (Angeles, Brazil) in Group 2 and gutta-percha. The teeth were subjected to vertical loading using a universal testing machine, and the readings were recorded at the point at which fracture of the roots occurred. The data were subjected to statistical analysis followed by pairwise comparison using Tukey's post hoc test. Results: According to the study, it was found that AH Plus showed better fracture resistance than MTA Fillapex. Statistically, no significant difference was found between the two groups. Conclusion: AH Plus and MTA Fillapex gave comparable results as root canal sealers.

Keywords: Endodontic monoblocks, mineral trioxide aggregate, root canal sealers, universal testing machine, vertical root fracture


How to cite this article:
Mittal A, Dadu S, Garg P, Yendrembam B, Abraham A, Singh K. Comparative evaluation of fracture resistance of endodontically treated teeth with epoxy resin-based sealers AH plus and mineral trioxide aggregate fillapex: An in vitro study. Indian J Dent Sci 2017;9:8-11

How to cite this URL:
Mittal A, Dadu S, Garg P, Yendrembam B, Abraham A, Singh K. Comparative evaluation of fracture resistance of endodontically treated teeth with epoxy resin-based sealers AH plus and mineral trioxide aggregate fillapex: An in vitro study. Indian J Dent Sci [serial online] 2017 [cited 2019 Mar 25];9:8-11. Available from: http://www.ijds.in/text.asp?2017/9/1/8/201640


  Introduction Top


It has been postulated that endodontic treatment results in a reduction of fracture resistance of teeth.[1] It is generally accepted that the strength of an endodontically treated tooth is directly related to the amount of remaining sound tooth structure.[2] Vertical root fractures are often associated with poor prognosis, resulting in the extraction of the involved tooth. Apart from predisposing factors such as caries with extensive tissue loss, trauma, root canal configuration and anatomy, dehydration, craze lines, loss of bone support; iatrogenic factors such as over instrumentation, prolonged use of calcium hydroxide, effect of irrigation solutions, condensation pressure exerted during obturation, and intracanal postplacement are also among the etiological factors causing vertical root fractures in endodontically treated teeth.[2],[3],[4],[5],[6],[7],[8],[9] One of the aims of root canal filling is to reinforce the dentin and increase the fracture resistance.[10]

Some authors have suggested that the use of glass ionomer cement or composite resin as bonded restorative materials, could reinforce the endodontically compromised teeth.[11],[12],[13],[14] These bonding materials have also been examined for use as root canal filling materials but were disregarded due to problems in working properties and lack of hermetic seal resulting in leakage.[15]

Root canal sealers should strongly adhere to dentine. Increased adhesiveness to dentine may lead to greater strength of the restored teeth, which may provide greater resistance to tooth fracture and clinical longevity of an endodontically treated tooth and therefore, decreasing the chances of endodontic failure.[15] Bondable root canal sealers create monoblocks within the root canal space with their sealing ability to wet and infiltrate dentin.[16],[17] The concept of sealing and tooth strengthening using adhesive root canal obturating materials is known as monoblock effect.[17],[18]

An important step for the success of endodontically treated teeth is obturation of the root canal system. Gutta-percha for its properties such as biological compatibility, lack of toxicity or allergic effects, and easy removal from the root canal, has been the most frequently used root canal filling material for years. Resin-based sealers have been used for several years to take advantage of adhesion to the dentinal walls which result in less microleakage and is considered to provide some strengthening effect to the teeth.[19]

Numerous studies have shown that the bond strength of epoxy resin-based sealer, AH Plus, was significantly higher than zinc oxide eugenol, calcium hydroxide, and glass ionomer-based sealers.[20],[21] Recently, introduced MTA sealer, MTA Fillapex, is biocompatible, seals the canal better and has good mechanical properties like having the modulus of elasticity similar to that of dentin.[22]

The purpose of this in vitro study was to compare the fracture resistance of endodontically treated teeth obturated with conventional gutta-percha using a different sealers epoxy resin based, AH Plus (Dentsply, Germany), and MTA Fillapex (Angeles, Brazil) sealer.


  Materials and Methods Top


Twenty extracted single-rooted mandibular human incisor teeth were used in the study. During their selection, care was taken to ensure that the teeth had similar buccolingual and mesiodistal dimensions. Then, all the collected teeth were immersed in 5% sodium hypochlorite (NaOCl) solution for 2 h for surface disinfection and dissolution of the superficial soft tissue. Preoperative radiographs were taken to ensure that the collected teeth did not have open apices, multiple canals, calcifications, fractures, or craze lines. All teeth were decoronated using a flexible diamond disk (Novo dental products, India) in a slow speed handpiece under copious amount of water coolant to standardized length of 12 mm as measured from the apex to the facial cementoenamel junction (CEJ).

The teeth were divided into two experimental groups. Coronal access was made to check the canal patency. To standardize the working length, a size 10 k file was inserted into the canal till the tip of the instrument was first visualized at the apical foramen. The working length was determined by subtracting 1 mm from this length.

Cleaning and shaping of the root canals were completed with ProTaper rotary NiTi files (Dentsply Maillefer, Switzerland) using an Xmart endodomotor (Dentsply) at a speed of 300 rpm. The canals were irrigated with 2 ml of 3% NaOCl after each instrumentation. Then, F1 master cone gutta-percha (Dentsply, Maillefer) was placed into the canal, and the fit was confirmed radiographically. Before obturation, the root canals in group 1 and 2 were irrigated with 17% ethylene diamine tetraacetic acid (EDTA) (Canalarge, Ammdent) and 3% NaOCl to remove the smear layer followed by a final flush of 5 ml of normal saline in all the test samples.

Grouping method

  • Group 1: Obturation with gutta-percha and sealer as AH Plus
  • Group 2: Obturation with gutta-percha and sealer as MTA Fillapex.


Sealers were mixed according to the manufacturer instructions. Root canals were coated with sealers using lentulospirals at 300 rpm and obturated using F1 ProTaper gutta-percha points.

Postobturation radiographs were taken for all the experimental root samples, in both labiolingual and mesiodistal directions to ensure homogeneous adequate root filling without voids. The filled roots were stored in an incubator for 7 days at 37°C and 100% relative humidity to allow the sealer to set completely.

For all specimens, the root surface was covered with a paste of silicon-based impression material (Aquasil) up to 2 mm apical to the CEJ to simulate a periodontal ligament and kept in 100% humidity for 24 h. Each tooth was then mounted vertically to a depth of 2 mm below the CEJ in polystyrene resin block using ice cube holder molds.

The resistance offered was tested using the universal testing machine for root samples of all groups against vertical fracture. A cylindrical hardened steel rod (2.2 mm diameter) with a sharpened conical tip was attached to the upper part of the universal testing machine (Asian Universal Testing Machine) to apply force to the root causing vertical root fracture. A vertical load was applied at a crosshead speed of 0.5 mm/min until the root fractured. The fracture was defined as the point at which a sharp and instantaneous drop >25% of the applied force was observed. For most specimens, an audible crack also was heard, and the amount of force required for fracture was recorded in Newtons.

The load of fracture in Newtons was converted to megapascal using the following formula:



  • π = 3.14 (constant value)
  • Area of cross-section of plunger = 2.2 (uniform for all specimens).


The fracture load data were subjected to statistical analysis using SPSS/PC software. Comparisons among the two groups were performed by Levene's Test for equality of variances and t-test for equality of means. The statistical analysis was performed at 95% confidence level [Figure 1] and [Figure 2].
Figure 1: Tracings obtained from Ah Plus group showing a gradual increase in fracture force (N) plotted against penetration depth in millimeters.

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Figure 2: Comparison of fracture resistance of the two sealers.

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  Results Top


The resin sealer AH Plus (171.95) showed higher fracture resistance than MTA Fillapex (144.66), although the results were not statistically significant (P = 0.05) [Table 1] and [Table 2].
Table 1: Group statistics - mean standard deviation and coefficient of variation of fracture resistance values in megapascals for the experimental groups

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Table 2: Comparison of two groups with respect to fracture resistance in mega-pascal's-Levene's test for equality of variances and t-test for equality of means

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  Discussion Top


Endodontic procedures such as access preparation, instrumentation, use of calcium hydroxide as intracanal medicament and even irrigation with NaOCl and EDTA leads to a reduction in the fracture resistance of endodontically treated teeth. A study concluded that enlarged but unfilled roots are significantly weaker than filled roots and are thus more susceptible to fracture.[23]

Finite element analysis study has found that circular canals have lower and more uniform stress distribution than oval canals in which greater stresses are present at the labial and lingual canal extensions and the cervical and middle thirds.[24] The main goal of three-dimensional obturation is to provide a fluid tight seal within the entire root canal system to prevent reinfection and to create a favorable biological environment for tissue healing.[25]

Some studies report an increased risk for craze lines and dentin cracks and reduced root fracture resistance with rotary instrumentation as compared to hand files.[26] Apical cracks are more likely to appear when the cleaning and shaping are done up to the root canal length, rather than confining it 1.0 mm short of the root apex.[27] Apical enlargement was done with ProTaper F1 in this study. A standard irrigation regimen, using EDTA and sodium hypochloride, was used to remove the smear layer as this combination has been shown to enhance bonding of the materials tested to the dentinal surface of the roots.[28]

Stable adhesion to root canal dentin walls and an elastic modulus similar to dentin are the two key factors to improve the fracture resistance of an endodontically treated teeth.[29]

AH Plus is an epoxy-based endodontic sealer that is used with gutta-percha. It comes as a two paste system unlike the liquid powder system of AH 26.[30] It has a working time of 4 h and setting time of 8 h; has good adhesion to dentin and gutta-percha.

MTA Fillapex is a sealer that is composed of MTA, salicylate resin, natural resin, bismuth oxide, and silica. It has suitable physicochemical properties such as good radiopacity, flow, and alkaline pH. It has a working time of 35 min.[25],[31] The MTA Fillapex paste formula contains biologically compatible salicylate resin (1,3 butileneglycol disalicylate resin) which is tissue-friendly, thus proving to be a better choice over epoxy-based resins, which have mutagenic and more cytotoxic effects.

It is essential to simulate the alveolar bone that can absorb the masticatory load and resist the compressive and tangential forces applied in fracture resistance in vitro tests. Periodontal ligament simulation prevents stress concentration in one particular region and transfers the stresses produced by load application all along the root surface.[32] Silicone paste and polystyrene resin blocks were used to simulate the periodontal ligament and alveolar bone, to test the root fracture resistance in the study.

A study showed that the bond strength at the coronal third of the root canal had no significant difference between MTA Fillapex, iRoot SP, and AH Plus, whereas, in the middle and apical thirds, iRoot SP, and AH Plus have equivalent bond strengths superior to MTA Fillapex.[33] In the present study, there was no statistically significant difference between AH Plus and MTA Fillapex in the fracture resistance of endodontically treated teeth.

On the basis of the present and previous studies, MTA Fillapex can take advantage of its biological and sealing characteristics, but further investigations are needed to study the bond strength and other physical properties of the material.


  Conclusion Top


The bonding of endodontic sealers to intraradicular dentin after obturation might possibly enhance the resistance to fracture of endodontically treated teeth. Within the limitations of the present study, it can be concluded that AH Plus showed higher fracture resistance than MTA Fillapex although the results were not statistically significant (P = 0.05). MTA Fillapex has lower bond strength compared to AH Plus, but it presented acceptable fracture resistance and thus can be used as an alternative.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

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    Figures

  [Figure 1], [Figure 2]
 
 
    Tables

  [Table 1], [Table 2]



 

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