Comparison of the antimicrobial activity of direct pulp-capping materials: Mineral trioxide aggregate-Angelus and Biodentine

Abstract

Purpose:

To compare the antimicrobial activity of the tricalcium silicate-based Biodentine (BD) and mineral trioxide aggregate (MTA)-Angelus cement with the aid of agar diffusion test.

Materials and Methods:

Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Enterococcus faecium were inoculated in the Brucella liquid medium and were incubated at 37°C for 24 h. Thereafter, 100 >μl of the liquid culture of bacteria inoculated in the Mueller-Hinton agar with spread plate technique. Petri plates were dried in room temperature. For every microorganism, 3 petri plates were prepared (12 in total). In the medium, in every petri plate, 2 holes with 5 mm diameter and 2 mm depth were made. Afterward, BD and MTA-Angelus were filled into these holes under aseptic conditions according to the instructions of the manufacturing company. Then, the plates were kept in the incubator at 37°C for 24 h, and the diameters of the inhibition zones were measured with a digital caliper.

Results:

Inhibition zones formed by BD against E. coli and S. aureus were significantly larger than the zones formed by MTA-Angelus (P < 0.05). However, the inhibition zones formed by MTA-Angelus against P. aureus and E. faecium were larger than the zones formed by BD (P < 0.05).

Conclusion:

Within the limits of the present study, tricalcium silicate-based MTA-Angelus and BD have antimicrobial activity against E. coli, S. aureus, P. aureus, and E. faecium.

INTRODUCTION

The purpose of the direct pulp capping is to cover the damaged pulp surface, ensure the vitality of the pulp together with its function and biological activity. Pulp damage may be caused by microorganisms, which survived in the dentin after the cavity preparation. To prevent this damage, direct pulp-capping materials placed directly over the pulp and localized under the permanent restoration must have good antimicrobial activity.[1] At the same time, direct pulp-capping materials have to ensure the formation of hard tissue through the stimulation of pulp cells.[2]

Mineral trioxide aggregate (MTA) was the first marketed biomaterial, launched as a root-end filling material in the endodontic surgical procedures and as a repair material for the perforations.[3] Nowadays, MTA is used confidently for conservative pulp treatment, treatment of the root resorptions, and apexification procedures.[4] It is shown that MTA is a bioactive material, which stimulates the formation of the hard tissue and tolerated by the contacted tissues due to its favorable biocompatibility.[5] However, as its setting time is long (4–6 h) and it is difficult to control its consistency, it is not an easy-to-use material in clinics. To eliminate such disadvantages of MTA, some tricalcium silicate-based materials were developed and marketed.[6] Biodentine (BD; Septodont, Saint-Maur-des-Fosses, France) is endodontic cement with a short setting time (12 min) and contains tricalcium silicate, dicalcium silicate, and calcium carbonate.[7] The manufacturing company suggests that BD can be used instead of dentine with restorative purposes and at the same time for the repair of the perforations in the endodontic treatment, instead of MTA in procedures such as root-end fillings and direct pulp capping.[8]

According to the literature search, only limited studies evaluating the antimicrobial activity of BD. The aim of this study was to compare the antimicrobial activity of the tricalcium silicate-based BD and MTA-Angelus cement (Angelus, Londrina, PR, Brazil) with the aid of agar diffusion test (ADT). The hypothesis of the present study was that the antimicrobial activity of different cement does not change regarding the microorganisms.

MATERIALS AND METHODS

To determine the antimicrobial activity of the BD and MTA-Angelus cement, we obtained standard species of Staphylococcus aureus ATCC 29213, Pseudomonas aeruginosa ATCC 27853, Escherichia coli ATCC 25922, and Enterococcus faecium ATCC from the Veterinary School of Ondokuz Mayıs University.

Bacteria were inoculated in the Brucella liquid medium and were incubated at 37°C for 24 h. At the end of the incubation time, liquid culture density was adjusted to 0.5 McFarland standard with the McFarland densitometry. Thereafter, 100 μl of the liquid culture of bacteria was inoculated in the Mueller-Hinton agar with spread plate technique. Petri plates were dried in room temperature. For every microorganism, 3 petri plates were prepared (12 in total). In the medium, in every petri plate, 2 holes with 5 mm diameter and 2 mm depth were made. Afterward, BD and MTA-Angelus were filled into these holes under aseptic conditions according to the instructions of the manufacturing company. Then, the plates were kept in the incubator at 37°C for 24 h, and the diameters of the inhibition zones were measured with a digital caliper. Three measurements were committed for every microorganism, and all measurement values were registered.

Statistical analysis

The normal distribution control of the data obtained in our study was done with Kolmogorov–Smirnov test, and the control of the homogeneity of the group variants was done with the Levene test. For the statistical analysis of the data, one-way analysis of variance, Student's t-test, and Duncan multiple comparison tests were used with SPSS 21 (IBM SPSS Inc., Chicago, IL, USA) software. The confidence interval is taken as 95% for the analysis (P < 0.05).

RESULTS

The means and the standard deviation values of the measurements (in mm) of the inhibition zones formed by the tested direct pulp-capping materials against E. coli, S. aureus, P. aureus, and E. faecium within 24 h are shown in Table 1.

Table 1.

The means and standard deviations of inhibition zones after 24 h (in mm)

Inhibition zones formed by BD against E. coli and S. aureus were significantly larger than the zones formed by MTA-Angelus (P < 0.05). However, the inhibition zones formed by MTA-Angelus against P. aureus and E. faecium were larger than the zones formed by BD (P < 0.05).

DISCUSSION

The exposure of the pulp and consequently arousing infection might cause pulp inflammation and necrosis. In such cases, root canal treatment may become necessary. The direct pulp-capping materials should act like a barrier, preserve the vitality of the damaged pulp, and eliminate the need of a root canal treatment. At the same time, the direct pulp-capping materials should have a good compatibility with the contacted pulp tissue and should not cause inflammation, irritation, allergic, or toxic reaction in the pulp. The microbial activity of the direct pulp-capping materials is one of the most important features influencing the success of the therapy. Because of material's activity, the material would eliminate the microorganisms around the pulp.[9] ADT method is a method used frequently for the evaluation of the antimicrobial activity of the dental materials.[10] The most important advantage of ADT is that it enables the comparison of the reactions emerged after the direct contact of the tested materials with microorganisms. However, its disadvantage is that while using ADT, it could not be distinguished whether the microbial activity is bacteriostatic or bactericidal.[11] In the present study, ADT was preferred because it enables to compare freshly mixed materials.[12,13]

Currently, as a direct pulp-capping material, MTA used often because of its superior biological features.[14,15,16] MTA not only causes less inflammation compared to calcium hydroxide but also it enables a better-mineralized barrier as a result of the differentiation and proliferation of the pulp cells. Because of these characteristics, MTA is as a comparable material among the direct pulp-capping materials. For this purpose, in the present study, MTA-Angelus was used because it could be used as a direct pulp-capping material because of its short setting time (15 min).

BD is one of the recently developed tricalcium silicate-based materials and could be used for deep and wide coronal tooth decay, restoration of the deep cervical and root lesions, in direct pulp capping, repair of the root perforations, and as a root-end filling material.[17,18] The most important advantages of BD over MTA are it could be easily manipulated as a result of its higher viscosity and its much shorter setting time. These features make BD a suitable direct pulp-capping material.[14,15,16] However, there is only limited information in the literature on the antimicrobial activity of the tricalcium silicate-based materials. Therefore, the aim of the present study was to compare the antimicrobial activity of the tricalcium silicate-based BD and MTA-Angelus with the aid of ADT. Even though aerobic and facultative bacteria are not mostly the major constituents of primary infections in the selection of test bacteria for this study, they have been observed more frequently in the failed treatment cases.[19,20]

Bhavana et al. compared in their in vitro study (2015) the antimicrobial activity of BD and MTA and reported that BD's antimicrobial activity is higher than MTA.[21] The present study results confirmed this finding and showed that the antimicrobial activity of BD against E. coli and S. aureus is significantly higher than MTA. In another in vitro study, it is reported that BD has no antimicrobial activity against S. mutans, but MTA-Angelus is antimicrobially active against S. mutans beside other tested microorganisms.[22]

Regarding the results of the present study, MTA-Angelus has a significantly better antimicrobial activity against P. aureus and E. faecium compared to BD. Furthermore, in other studies, similar to the present study, it is reported that MTA has antimicrobial activity against P. aureus.[23,24] Torabinejad et al. reported in their study, MTA has no antimicrobial activity against E. coli. However, contrarily, in the present study, it was observed that MTA has antimicrobial activity against E. coli.[25] These contradictory findings might be depend on the MTA concentrations and differences in preparation methods that influence the antimicrobial activity.[24,25,26] It is shown that MTA produces calcium hydroxide when hydrated. Therefore, it could be suggested that MTA and calcium hydroxide have the same antimicrobial activity mechanism.[3] The antimicrobial activity of the calcium hydroxide-based materials depends on the pH increase caused by the released hydroxyl ions as a result of ionization. The cellular enzymes of microorganisms are inactivated reversibly and irreversibly by the pH.[27] It could be suggested that the antimicrobial activity of MTA results from its high pH and the substances released to the environment. It should be kept in mind that the present study is conducted under in vitro planktonic cell culture media conditions and microorganisms may act differently in vivo. Therefore, in vivo studies are needed for the better understanding of their antimicrobial activity.

CONCLUSION

Within the limits of the present study, it was observed that tricalcium silicate-based MTA-Angelus and BD have antimicrobial activity against E. coli, S. aureus, P. aureus, and E. faecium. Furthermore, BD was found to be effective against E. coli and S. aureus while MTA- Angelus had higher antimicrobial activity against P. aureus and E. faecium.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.