The benefit of culture-independent methods to detect bacteria and fungi in re-infected root filled teeth: a pilot study

Periapical bacterial disinfection is critical for dental pulp regenerative cell therapy in apical periodontitis in dogs

BACKGROUND

Application of pulp regenerative cell therapy for mature teeth with periapical lesions is a critical clinical challenge. The bacterial infection in inaccessible location within the root canal system and in the periapical lesions could cause resistance and impediment, leading to limitations in successful therapy. Thus, the aim of this study was to examine the effect of residual bacteria on the outcome of pulp regeneration in mature teeth with apical periodontitis in dogs.

METHODS

Periapical lesions were induced in 32 root canals of 4 dogs in two different models in severities, model A and model B. Model A (moderate infection): the canal exposed to the oral cavity for 2 weeks and then closed for 2 weeks. Model B (severe infection): the canal exposed to the oral cavity for 2 months and then closed for 5 months. All root canals were irrigated with 6% sodium hypochlorite, and 3% EDTA and further with 0.015% levofloxacin-containing nanobubbles, which was also used as an intracanal medicament. The aseptic conditions were examined by bacterial anaerobic culture and/or PCR analyses. The root canal treatment was repeated several times, and allogeneic dental pulp stem cells were transplanted into the root canals. The radiographic evaluation of periapical lesions was performed by cone-beam computed tomography before the first treatment, just after cell transplantation, and after 2 months and 6 months in both model A, model B, respectively. The animals were then sacrificed and the jaw blocks were harvested for histological and histobacteriological evaluations of pulp regeneration and periapical tissue healing. Furthermore, the DiI-labelled DPSCs were transplanted into the root canals after complete disinfection (n = 4) or without root canal treatment (n = 4) in the apical periodontitis model (model A) in one dog, and cell localization was compared 72 h after transplantation.

RESULTS

In 8 out of 12 canals from model A, and 10 out of 15 canals from model B, pulp regeneration with good vascularization, innervation, and a significant reduction in the radiolucent area of the periapical lesions were observed. However, in the other 4 canals and 5 canals from model A and model B, respectively, no pulp tissue was regenerated, and inflammation in the periapical tissue, and external resorption or healed external resorption were detected. The presence of residual bacteria in the periapical tissues and severe inflammation were significantly associated with inhibition of regenerated pulp tissue in these 9 unsuccessful canals (P < 0.05, each) (OR = 0.075, each) analyzed by multiple logistic regression analysis. For cellular kinetics, transplanted cells remained in the disinfected root canals, while they were not detected in the infected root canals, suggesting their migration through the apical foramen under the influence of inflammation.

CONCLUSIONS

A true pulp-dentin complex was regenerated in the root canal by the pulp regenerative therapy in mature teeth with apical lesions. The successful pulp regeneration was negatively associated both with residual bacteria and inflammation in the periapical tissue.

Bacterial diversity in primary infected root canals of a Chinese cohort: analysis of 16 S rDNA sequencing

PURPOSE

To characterize the bacterial community in the primarily infected root canals.

METHODS

A total of 13 samples were collected from the primarily infected root canals. 16 S rDNA sequencing was performed to define bacterial community. Taxonomic annotation, bacterial hierarchical structures, community richness and diversity, and inter-subject variability of the bacterial community in the root canal samples were analyzed. Gender, age, and duration of the toothache-specific bacterial community associated with the patient groups were analyzed.

RESULTS

A total of 359 Species were annotated and identified in the whole study cohort. The Alpha diversity analysis showed that the species diversity and detection rate of the 13 samples were high, which reflected the authenticity of sequencing results. The Beta diversity analysis was used to compare the degree of difference between different root canal samples. The 13 samples were divided into two groups according to the results, group A was samples I1-I12, and group B was samples I13. The bacterial species of group A samples were analyzed with the clinical characteristics of patients, and it was found that gender, and duration specific differences in bacterial species, and there was no significant difference in species types among different ages of patients.

CONCLUSION

There were a wide diversity and inter-subject variability in the bacterial community in the primary infected root canals. While Porphyromonas gingivalis was the most abundant species, Fusobacterium nucleatum was the most variable species in the bacterial community of the root canal. The bacterial community at different taxonomic levels varied from sample to sample, despite consistent disease diagnoses. There was gender, duration-specific differences in the bacterial species in the primary infected root canals.

Microbiome Changes During Regenerative Endodontic Treatment Using Different Methods of Disinfection

INTRODUCTION

The purpose of this study was to characterize qualitatively and quantitatively the changes in the endodontic microbiome, in teeth with necrotic pulp, open apexes and apical periodontitis, with three antimicrobial protocols, undertaken in a multicenter clinical trial.

METHODS

Microbiological samples were collected from 116 RET teeth, and 97 qualified for inclusion. The teeth were randomly divided into three treatment groups: apexification (APEX), regeneration (REGEN) and revascularization (REVASC), all in two appointments. The group variables in the first appointment irrigants, and second appointment irrigants and medicaments were as follows: APEX: 5.25-6% NaOCl, 5.25-6% NaOCl + 17% EDTA and calcium hydroxide; REGEN: 1.25% NaOCl, 17% EDTA and 0.1 mg/mL triple antibiotic paste (TAP); and REVASC 5.25% NaOCl, saline and 1g/mL TAP, respectively. Sampling was done upon access (S0), after irrigation in the first appointment (S1), and after using medication and irrigation in the second appointment (S2).

RESULTS

Quantitative PCR analysis of the 16S rRNA gene showed significant reduction in bacterial load from S0 to S2 in all groups; however, the APEX and REVASC groups had significantly less residual DNA than the REGEN group (p=0.0045). The relative abundance of Bacteroidetes, Fusobacteria, Spirochaetes and Synergistetes were reduced with the treatment rendered. However, relative abundance of Firmicutes and Actinobacteria was not changed, and that of Proteobacteria increased. LEfSe analysis showed that reduction in bacterial taxa was more in REVASC than APEX which in turn was more than in REGEN.

CONCLUSION

Enhanced antimicrobial protocols lead to better reduction in quantitative and qualitative parameters of the endodontic microflora.

Effect of Enterococcus faecalis OG1RF on human calvarial osteoblast apoptosis

Background

Enterococcus faecalis is a dominant pathogen in the root canals of teeth with persistent apical periodontitis (PAP), and osteoblast apoptosis contributes to imbalanced bone remodelling in PAP. Here, we investigated the effect of E. faecalis OG1RF on apoptosis in primary human calvarial osteoblasts. Specifically, the expression of apoptosis-related genes and the role of anti-apoptotic and pro-apoptotic members of the BCL-2 family were examined.

Methods

Primary human calvarial osteoblasts were incubated with E. faecalis OG1RF at multiplicities of infection corresponding to infection time points. Flow cytometry, terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) assay, caspase-3/-8/-9 activity assay, polymerase chain reaction (PCR) array, and quantitative real-time PCR were used to assess osteoblast apoptosis.

Results

E. faecalis infection increased the number of early- and late-phase apoptotic cells and TUNEL-positive cells, decreased the mitochondrial membrane potential (ΔΨm), and activated the caspase-3/-8/-9 pathway. Moreover, of all 84 apoptosis-related genes in the PCR array, the expression of 16 genes was upregulated and that of four genes was downregulated in the infected osteoblasts. Notably, the mRNA expression of anti-apoptotic BCL2 was downregulated, whereas that of the pro-apoptotic BCL2L11, HRK, BIK, BMF, NOXA, and BECN1 and anti-apoptotic BCL2A1 was upregulated.

Conclusions

E. faecalis OG1RF infection triggered apoptosis in human calvarial osteoblasts, and BCL-2 family members acted as regulators of osteoblast apoptosis. Therefore, BCL-2 family members may act as potential therapeutic targets for persistent apical periodontitis.

Fungal species in endodontic infections: A systematic review and meta-analysis

Fungal infections are common on oral mucosae, but their role in other oral sites is ill defined. Over the last few decades, numerous studies have reported the presence of fungi, particularly Candida species in endodontic infections, albeit in relatively small numbers in comparison to its predominant anaerobic bacteriome. Here, we review the fungal biome of primary and secondary endodontic infections, with particular reference to the prevalence and behavior of Candida species. Meta-analysis of the available data from a total of 39 studies fitting the inclusion criteria, indicate the overall weighted mean prevalence (WMP) of fungal species in endodontic infections to be 9.11% (from a cumulative total of 2003 samples), with 9.0% in primary (n = 1341), and 9.3% in secondary infections (n = 662). Nevertheless, WMP for fungi in primary and secondary infections which were 6.3% and 7.5% for culture-based studies, increased to 12.5% and 16.0% in molecular studies, respectively. The most prevalent fungal species was Candida spp. The high heterogeneity in the reported fungal prevalence suggests the need for standardized sampling, and speciation methods. The advent of the new molecular biological analytical platforms, such as the next generation sequencing (NGS), and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF), that enables identification and quantitation of a broad spectrum of hitherto unknown organisms in endodontic infections should radically alter our understanding of the endodontic mycobiome in the future. Candida spp. appear to be co-pathogens with bacteria in approximately one in ten patients with endodontic infections. Hence, clinicians should comprehend the importance and the role of fungi in endodontic infections and be cognizant of the need to eradicate both bacteria and fungi for successful therapy.