Antibacterial effectiveness of diluted preparations of intracanal medicaments used in regenerative endodontic treatment on dentin infected by bacterial biofilm: An ex vivo investigation

BACKGROUND

Conventional drug mixtures used in regenerative endodontic procedures have a toxic effect and no consensus has been reached about their best composition and concentration. Therefore, the aim of this study was to determine minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and minimum biofilm inhibitory concentration (MBIC) of the antimicrobial preparations and to compare their antimicrobial efficacy on bovine dentin infected by Enterococcus faecalis.

MATERIALS AND METHODS

For this original ex vivo investigation, prepared concentrations (MIC, MBC, and MBIC) of triple antibiotic paste (TAP), double antibiotic paste (DAP), modified triple antibiotic paste (MTAP)-1, MTAP2, co-amoxiclav, and calcium hydroxide (CH) were added to the prepared bovine dentin blocks (which incubated in E. faecalis suspension previously) and incubated for 3 days. The samples were subsequently prepared for culture and CFU counts. Statistical analysis of data was carried out using one-way analysis of variance and post hoc tests. The statistical power was set at P < 0.05.

RESULTS

All medicament groups significantly showed an antimicrobial efficacy compared with negative control (without antibiotic) (P < 0.001). TAP, DAP, co-amoxiclav, and CH (at its MBC value) were significantly capable of eliminating E. faecalis biofilm and showed no significant difference in comparison with positive control (complete biofilm removal) (P < 0.05).

CONCLUSION

TAP, DAP, co-amoxiclav, and CH (at its MBC value) could effectively eliminate biofilm bacteria on the dentin surface. Antimicrobial efficacy of other medicaments containing cefaclor or clindamycin was limited.

Cytotoxicity Evaluation of Minimum Antibacterial Values of Different Medicaments Used in Endodontic Regenerative Procedures

OBJECTIVES

 This study aimed to evaluate the cytotoxicity of minimum antibacterial values of medicaments used in endodontic regeneration on stem cells.

MATERIALS AND METHODS

 "Minimum inhibitory concentration," "minimum bactericidal concentration," and "minimum biofilm inhibitory concentration" of triple and double antibiotic paste, a modified triple antibiotic paste (minocycline replaced by clindamycin), Augmentin, and calcium hydroxide were determined using Enterococcus faecalis (ATCC 29212) by microtiter plate method. Direct cytotoxic effects of drugs were evaluated by lactate dehydrogenase and water-soluble tetrazolium salt-1 assays using stem cells of apical papilla obtained from immature third molars via enzymatic digestion.

STATISTICAL ANALYSIS

 Data were analyzed using IBM SPSS Statistics 24, one-way analysis of variance and post hoc comparisons. The statistical power was set at p < 0.05.

RESULTS

 All medicaments caused similar cytotoxicity and cell proliferation at "minimum inhibitory concentration" (p > 0.05) except Augmentin which was significantly more toxic than others (p < 0.05). At "minimum bactericidal concentration," calcium hydroxide was more toxic than other drugs (p < 0.001), but its adverse effect on cell proliferation was the same as Augmentin (p > 0.05). Triple and double antibiotic paste revealed similar favorable effects in terms of toxicity and proliferation rate at most of the tested concentrations (p > 0.05). At "minimum biofilm inhibitory concentration" both the modified paste and Augmentin caused less proliferation rate than triple and double antibiotic paste (p < 0.001and p < 0.05, respectively) and Augmentin induced more cytotoxicity (p < 0.05).

CONCLUSIONS

 Considering the antimicrobial potency, triple antibiotic paste seems to be the safest drug for the stem cells of apical papilla, while Augmentin may have some adverse effects.

Evaluation of the Effect of MTAD on Expression of Enterococcus faecalis Virulence Factors Considering the Role of Different Obturating Materials

OBJECTIVES

The aim of this study was to determine the effect of MTAD on the expression of virulence factors of Enterococcus faecalis (E.faecalis) considering the role of Guttapercha/AH26 or Resilon/RealSeal SE as root canal obturating materials.

MATERIALS AND METHODS

One-hundred and forty-four single-rooted human teeth were instrumented to a standardized apical size. Root canals were infected by E.faecalis (ATCC 29212). Ninety teeth were irrigated with MTAD and randomly divided into three groups. In two groups, root canals were obturated by either Gutta-percha/AH26 or Resilon/RealSeal SE. Root canals were kept unobturated in the third group. The remaining 54 teeth received no final irrigation. All groups were then subdivided into three timepoint subgroups in which dentin powder was obtained from each sample to determine the expression of specific virulence factors of E.faecalis (efa, esp, gel, fsr) using real-time reverse transcription polymerase chain reaction (RT-PCR). Statistical analysis was performed by one-way analysis of variance (ANOVA) and Tukey's post-hoc test. The statistical power was set at P-value ≤0.05.

RESULTS

MTAD was effective against the expression of most of the tested virulence factors, and Gutta-percha/AH26 increased the antibacterial efficacy of MTAD.

CONCLUSIONS

MTAD could inhibit the expression of some known virulence factors of E.faecalis at the majority of tested timepoints. This may partly explain some of the mechanisms of antimicrobial efficacy of MTAD against this resistant microorganism which is known as one of the main causes of failure of root canal treatment.

Comparison of Antimicrobial Effects of Triple Antibiotic Paste and Calcium Hydroxide Mixed with 2% Chlorhexidine as Intracanal Medicaments Against Enterococcus faecalis Biofilm

OBJECTIVES

The purpose of this in-vitro study was to determine and compare the shortest period needed for a triple antibiotic paste (TAP) and calcium hydroxide (Ca(OH)₂) plus 2% chlorhexidine (CHX) to eradicate the biofilm of Enterococcus faecalis (EF) from the root canal system.

MATERIALS AND METHODS

Sixty-five extracted single-rooted human teeth with straight root canals were selected. The crowns were cut from the cementoenamel junction (CEJ), and canal preparations were done by step-back technique. The smear layer was removed by 17% ethylenediaminetetraacetic acid (EDTA) and 5.25% sodium hypochlorite (NaOCl). Afterwards, the samples were sterilized with gamma ray and were placed inside microtubes for one week. During this week, the teeth were infected with EF. Then, a TAP and Ca(OH)₂ mixed with 2% CHX were inserted into the canals. The roots were cut longitudinally, and dentin chips were collected from the apical part of the roots by a round bur to the depth of 400 μm. The vital bacterial load was assessed by counting the numbers of colony-forming units (CFUs).

RESULTS

The paste of Ca(OH)₂ mixed with 2% CHX was able to eradicate the EF biofilm in three days. The TAP was able to eradicate the biofilm of EF in seven days.

CONCLUSIONS

It seems that Ca(OH)₂ mixed with 2% CHX is more potent than the TAP against EF biofilm.