Clastic cells are absent around the root surface in pulp-exposed periapical periodontitis lesions in mice

Absence of tumor necrosis factor receptor 1 inhibits osteoclast activity in apical dental resorption caused by endodontic infection in mice

INTRODUCTION

To evaluate osteoclastogenesis and dental resorption resulting from endodontic infection in wild-type (WT) and tumor necrosis factor receptor 1 genetically deficient (TNFR1 KO) mice.

METHODS

After approval by the Ethics Committee on the use of Animals, 40 mice were distributed into two experimental groups based on periods: 14 days (n=10 WT mice; n=10 TNFR1 KO mice) and 42 days (n=10 WT mice; n=10 TNFR1 KO mice). After these periods, morphometrics analysis was done using bright field and fluorescence microscopy and tartrate-resistant acid phosphatase histoenzymology to identify osteoclasts. One-way analysis of variance followed by Tukey's post-hoc test was used for the statistical analysis (a=0.05).

RESULTS

WT mice in the 42-day period had a greater resorption in the apical region distal root of the first molar than TNFR1 KO mice (p<0.05). On the other hand, TNFR1 KO mice showed a smaller number of osteoclasts on the dental surface than WT mice (p<0.05).

CONCLUSION

WT mice had more extensive bone and apical dental resorptions and a larger number of osteoclasts on the tooth surface than TNFR1 KO mice.

Genetic, Cellular and Molecular Aspects involved in Apical Periodontitis

The development, establishment and repair of apical periodontitis (AP) is dependent of several factors, which include host susceptibility, microbial infection, immune response, quality of root canal treatment and organism's ability to repair. The understanding of genetic contributions to the risk of developing AP and presenting persistent AP has been extensively explored in modern Endodontics. Thus, this article aims to provide a review of the literature regarding the biochemical mediators involved in immune response signaling, osteoclastogenesis and bone neoformation, as the genetic components involved in the development and repair of AP. A narrative review of the literature was performed through a PUBMED/MEDLINE search and a hand search of the major AP textbooks. The knowledge regarding the cells, receptors and molecules involved in the host's immune-inflammatory response during the progression of AP added to the knowledge of bone biology allows the identification of factors inherent to the host that can interfere both in the progression and in the repair of these lesions. The main outcomes of studies evaluated in the review that investigated the correlation between genetic polymorphisms and AP in the last five years, demonstrate that genetic factors of the individual are involved in the success of root canal treatment. The discussion of this review gives subsides that may help to glimpse the development of new therapies based on the identification of therapeutic targets and the development of materials and techniques aimed at acting at the molecular level for clinical, radiographic and histological success of root canal treatment.

Phage therapy for refractory periapical periodontitis caused by Enterococcus faecalis in vitro and in vivo

A phage PEf771 that specifically infects and lyses pathogenic Enterococcus faecalis YN771 in patients with refractory periapical periodontitis was used to investigate resistance against E. faecalis infection in vitro and in vivo. PEf771 completely lysed YN771 within 3 h, with a multiplicity of infection of 1. Compared with ten routinely used clinical antibiotics, PEf771 demonstrated the highest bacteriostatic effect within 72 h. The antibacterial effect of PEf771 on extracted teeth within 72 h was better than that of conventional root canal disinfectants such as camphorated phenol, formaldehyde cresol solution, and Ca(OH)₂ (P < 0.05) within 72 h. Using E. faecalis, intraperitoneal and periapical infection models were established using Sprague Dawley (SD) rats. The results showed that all SD rats inoculated with 9.6 × 10¹¹ CFU/mL E. faecalis YN771 or 2.9 × 10¹¹ CFU/mL E. faecalis RYN771 died within 8 h. Additionally, all SD rats inoculated with YN771 and treated with antibiotics died within 72 h. Although SD rats inoculated with RYN771 and treated with antibiotics survived for 72 h, the pathological anatomy of these rats showed purulent discharge, numerous pus and blood-filled ascites, and extensive liver abscesses. Notably, YN771 rats treated with PEf771 and RYN771 rats treated with RPEf771 survived for 72 h, and their pathological anatomy showed that the liver, kidneys, intestine, and mesenteries were normal. Computed tomography analysis of SD rats infected with periapical periodontitis showed pathological changes in experimental teeth inoculated with YN771, despite undergoing a normal root canal treatment. Contrastingly, none of the experimental teeth exhibited root periapical inflammation following PEf771 treatment. Hematoxylin and eosin staining revealed a gap between the periodontal ligament and the cementum of experimental teeth, whereas PEf771-treated teeth exhibited normal results. These findings suggested that phage therapy using PEf771 might effectively prevent E. faecalis infection after root canal treatment.Key points• Compared with common clinical antibiotics, PEf771 showed the highest antibacterial.• The liver, kidney, intestine, and mesentery of SD rats treated with PEf771 were normal.• Phage therapy can effectively prevent E. faecalis YN771 and RYN771 infection.

Microcracks on the Rat Root Surface Induced by Orthodontic Force, Crack Extension Simulation, and Proteomics Study

Root resorption is a common complication during orthodontic treatment. Microcracks occur on the root surface after an orthodontic force is applied and may be related to the root resorption caused by the orthodontic process. However, the mechanisms underlying root resorption induced by microcracks remain unclear. In this study, a rat orthodontic model was used to investigate the biological mechanisms of root resorption caused by microcracks. First, the first molar was loaded with 0.5-N orthodontic force for 7 days, and microcracks were observed on the root apex surface using a scanning electron microscope. Second, to describe the mechanical principle resulting in microcracks, a finite element model of rat orthodontics was established, which showed that a maximum stress on the root apex can cause microcrack extension. Third, after 7 days of loading in vivo, histological observation revealed that root resorption occurred in the stress concentration area and cementoclasts appeared in the resorption cavity. Finally, proteomics analysis of the root apex area, excluding the periodontal ligament, revealed that the NOX2, Aifm1, and MAPK signaling pathways were involved in the root resorption process. Microcrack extension on the root surface increases calcium ion concentrations, alters the proteins related to root resorption, and promotes cementoclast formation.

Nano-graphene oxide with antisense walR RNA inhibits the pathogenicity of Enterococcus faecalis in periapical periodontitis

Background/purpose

Enterococcus faecalis (E. faecalis) is considered a predominant pathogen for persistent periapical infections. Antisense walR (ASwalR) RNA was reported to inhibit the biofilm formation and sensitized E. faecalis to calcium hydroxide medication. The aims of this study were to investigate whether the graphene oxide (GO) nanosheets could be used to enhance antibacterial activity of ASwalR RNA for E. faecalis in periapical periodontitis.

Materials and methods

We developed a graphene-based plasmid transformation system by loading antisense walR plasmid with GO-polyethylenimine (PEI) complexes (GO-PEI-ASwalR). The particle size distributions and zeta-potential of the GO-PEI-ASwalR were evaluated. Then, ASwalR plasmids were labeled with gene encoding enhanced green fluorescent protein (ASwalR-eGFP). The transformation efficiencies and the bacterial viability of E. faecalis were evaluated by confocal laser scanning microscopy. Quantitative real-time PCR assays were used to investigate the expressions of E. faecalis virulent genes after transformed by GO-PEI-ASwalR. Also, the antibacterial properties of the GO-PEI-ASwalR were validated in the rat periapical periodontitis model.

Results

We showed that GO-PEI could efficiently deliver the ASwalR plasmid into E. faecalis cell. GO-PEI-ASwalR significantly reduced virulent-associated gene expressions. Furthermore, GO-PEI-ASwalR suppressed biofilm aggregation and improved bactericidal effects using infected canal models in vitro. In four-weeks periapical infective rat models, the GO-PEI-ASwalR strains remarkably reduced the periapical lesion size.

Conclusion

Transformation efficiency and antibacterial prosperity of ASwalR can be marked improved by GO-PEI based delivery system for E. faecalis infections.

The potential effect of Bruton's tyrosine kinase in refractory periapical periodontitis

To determine the expression of Bruton's tyrosine kinase (BTK) in refractory periapical periodontitis and analyze the relationship between BTK and bone resorption in refractory periapical periodontitis. The mechanism of bone resorption is also discussed. The OneArray Plus expression microarray was used to screen for genes related to refractory periapical periodontitis. Real-time PCR was used to detect the expression of BTK in refractory periapical periodontitis tissues. A model of periapical periodontitis was established by sealing E.faecalis into the pulp of rats. To establish a model of E.faecalis LTA infection of osteoclasts, the relationship between BTK and bone destruction during refractory periapical periodontitis was analyzed. OneArray Plus expression microarray results showed that we found that the expression of 1787 genes in the two samples was different. After validating these samples, we found that BTK was closely related to refractory periapical periodontitis. The results showed that the expression of BTK in refractory periapical periodontitis tissues was higher than that in normal tissues. Immunohistochemistry, enzyme histochemistry and real-time PCR showed that the BTK expression curve in the experimental model resembled a reverse V shape from week 1 to week 4. Osteoclasts were cultured in vitro and treated with E. faecalis LTA. The expression of BTK in the E. faecalis model was greater than that in the control group. BTK played an important role in the progression of refractory periapical periodontitis.