Analysis of the porosity of endodontic sealers through micro-computed tomography: A systematic review.

Endodontic treatments have as their objective the appropriate sealing of the space caused by the root canal, providing a complete seal of the canal in all dimensions, creating an airtight seal against fluids. Thus, endodontic cements must possess physical properties such as solubility and long-term dimensional stability. An electronic search in the main endodontic magazines using appropriate keywords to identify studies that investigated the porosity of endodontic materials using micro-computed tomography. Of the 125 studies researched, 16 fulfilled the criteria for inclusion. Four studies analyzed the porosity of endodontic cements specifically. Twelve studies investigated and compared different techniques of root canal obturation and the repercussions from the lowering of porosity in the interior of the endodontic cement. The presence of porosity inside the endodontic cement is a constant in the treatments of root canals, even now when there is a great variety of endodontic cements.

INTRODUCTION

Among the principle key to the success of endodontic treatment is the sealing in an appropriate manner the root canal.[1] The sealing of a root canal has historically been achieved with gutta-percha and a sealer, the goal being to completely seal the canal in all dimensions, creating an airtight seal against fluids and avoiding the entrance of bacteria, toxins, and their flow toward the periapical tissues.[2] Therefore, it is important that sealing and repairing cements possess certain physical properties, such as solubility and long-term dimensional stability.[3] There are studies that have analyzed that the solubility of a duct-sealing material is in permanent relationship with the porosity that this material may have.[4] The porosity and other defects of the microstructure of the endodontic sealant can produce foci of structural weakness and tensile strength of the material, producing microcracks.[5]

Microcracks are defined as a decrease in the partial or total strength of a sealant, which can cause leakage within the endodontic cement in the root canal.[6] Therefore, when we use the term pores when we speak of an endodontic material, we refer to the interaction between its physical properties and the type of mixture that was used to produce the material. Sealing or duct repair materials that are mixed manually according to the studies that have been made are more prone to subjective factors induced by the operator, thus producing more structural defects.[78]

Micro-computed tomography (micro-CT) creates nondestructive three-dimensional (3D) images utilized to evaluate the microstructure, morphology, density of the mineralized tissues, and the internal structure.[9]

In endodontics, micro-CT has been used to evaluate the anatomy of root canals, their geometry, or shape to estimate the morphology of the dental root in addition to the spatial details after the instrumentation of the root canal.[10] Another use of micro-CT in endodontics is to analyze the volume of pores inside endodontic cements[3111213] and for the comparison of various obturation techniques that help to reduce the amount of pores in endodontic cements inside of the root canal.[71415161718192021222324]

METHODOLOGY OF PUBLICATION SEARCH

An electronic search was made of the database PubMed (https://www.ncbi.nlm.nih.gov/pubmed/), Scopus (https://www.scopus.com) to identify the studies related to the evaluation of the porosity of different endodontic cements using micro-CT images. The following keywords were used: “Micro-CT” and “porosity” and “root canal filling materials” or “root canal obturation” or “endodontic sealer” and “obturation techniques.” The search was limited to publications written in English. A manual electronic search was also carried out for the following main endodontic magazines: Journal of Dental Research; Dental Materials; Journal of Dentistry; Journal of Endodontics; International Endodontic Journal; The Journal of the American Dental Association; European Journal of Oral Sciences; and Australian Endodontic Journal. The following keywords were used for this search: “Micro-CT” and “endodontic sealer” and “porosity.” The search included articles from the start of each publication up to November 30, 2017. After the elimination of duplicate articles and reviewing the titles and summaries, full-text articles were used to verify that the content of the article was relevant.

RESULTS

Following the elimination of duplicate articles, the electronic search strategy produced 125 publications. The initial selection of the studies was done using the titles and summaries. However, when the suitability of an article was not clear, then the entire text was read. The writers evaluated the studies independently and discussed the results. Of the 125 studies found, 16 fit the criteria [Figure 1].

Figure 1

A flow diagram of records

DISCUSSION

Using microcomputed tomography to evaluate porosity

In the characterization of dental materials, micro-CT has gained much popularity due to its 3D nature and that it is not destructive, leaving the material intact following the analysis. Although micro-CT is widely used for the characterization of porous materials, the accuracy and reliability of this method still require more quantifying.[25]

Analysis of the porosity of endodontic cements

Research and scientific publications that study only the porosity of endodontic obturation materials by means of micro-CT analysis present a reduced number of articles on this specific topic. We find references to Mokeem-Saleh and Mokeem et al.[311] and their research that has analyzed the porosity of endodontic cements, which find that endodontic sealers produce a level of porosity depending on the composition of the endodontic cement and some cements present a higher volume of porosity than others. In addition, all of the researchers who analyzed the porosity of specific endodontic cements in vitro affirm that there is no material that is 100% free of porosity.[3111213]

A study performed with ProRoot® MTA y MTA Angelus®, in which the porosity of those endodontic materials was analyzed in vitro, found that there is no statistically significant difference between the two materials.[12]

When comparing the following endodontic cements in a study in vitro, iRoot BP Plus®, Biodentine®, Ceramicrete-D, ProRoot® MTA, the researchers found that iRoot BP Plus® has the highest porosity and Ceramicrete-D is the endodontic cement with the least porosity.[13] [Table 1].

Table 1

Studies that reviewed the porosity of endodontic materials using micro-computed tomography analysis

Analysis of the porosity of endodontic cements according to the obturation technique

In reference to the obturation technique applied at the moment of sealing a root canal, there are various in vitro studies that evaluate the porosity of the root canal through micro-CT, reporting similar findings among all of the analyzed studies in that of all the obturation materials and techniques used, there is not a single result that presents the absence of pores in the interior of the canal.[714151617181920212223242627]

The endodontic cement most analyzed, applying diverse obturation techniques according to the different studies analyzed in this systematic review, is AH Plus®[1415171820222327] In the study by Gandolfi et al.,[22] MTA Flow™ was compared with AH Plus® using Thermafil® as the obturation technique and the study concluded that MTA Flow™ produced less porosity at the time of sealing the root canal. However, in another study that analyzed the porosity of the material when using the lateral condensation technique with BioRoot™ RCS and AH Plus®, the results showed that BioRoot™ RCS produced greater porosity than AH Plus®.[17]

An in vitro study compared MTA Angelus® and ProRoot® MTA using different mixing techniques and condensation, showing that MTA Angelus® presents a higher quantity of pores than ProRoot® MTA and also that the mechanical mixing technique and indirect ultrasonic activation were the methods that produced the lowest amount of pores in root canals.[7]

Among the various techniques available to seal the root canal, the lateral condensation technique, use of a single cone, and vertical compaction are the ones that obtain the best results when the porosity is measured using micro-CT, depending on the obturation material being applied.[16182023] There are other techniques that cannot be compared with the aforementioned since there is no in vitro scientific study to compare them. However, based on the results of the recently mentioned studies, we can say that the techniques BeeFill®, Thermafil®, and ReaSeal 1™ contribute to a reduction of porosity.[19222427] In addition, there are other materials such as RoekoSeal® y Tubli-Seal™ Ewt that show a reduced volume of pores in the interior of said endodontic cements[1924] [Table 2].

Table 2

Studies that investigate the porosity of endodontic materials according to the obturation technique employed using micro-computed tomography

CONCLUSIONS

The use of different obturation techniques and the wide variety of endodontic cements with varied compositions available currently allow us to lower substantially the presence of porosity in the interior of the root canal, but there does not exist any technique nor any endodontic material that eliminates porosity completely when performing an endodontic treatment.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.