Microtissue engineering root canal dentine with crosslinked biopolymeric nanoparticles for mechanical stabilization

Deciphering 3D periodontal fibroblast-macrophage crosstalk in bioactive nanoparticle-guided immunomodulation for treating traumatic dental avulsion

Prolonged extra-oral period in dental avulsion is often associated with loss of viability of Periodontal fibroblasts (PDLF) and increased risk of ankylosis. Root surface treatment with bioactive agents to reduce the risk of ankylosis can be a potential strategy. The objective of the study was to investigate the impact of an engineered chitosan nanoparticles (CSNP), photosensitizer Rose Bengal (RB) functionalized CSNP (CSRB) and sustained dexamethasone (CSDEX) releasing CSNP for application in management of delayed replantation of avulsed teeth. The 3D PDLF-macrophage (Mϕ) collagen model was developed and exposed to LPS, MCSF, RANKL with and without CSDEX/CSNP. Immunofluorescence and cytokine analysis was done at 2 and 7 days to assess cellular interactions. Maxillary right incisors in male Wistar rats were extracted, exposed to extraoral dry or LPS for 1 h and treated with or without CSDEX/CSRB for 1 min before replantation. Rats were euthanized after 21 days for micro-CT, TRAP, and immunofluorescence analysis. CSDEX/CSNP treatment in 3D model significantly reduced CD80, NFATc1, STAT6 and increased CD206 and periostin expression (p < 0.05). TNFα, MMP9 was downregulated and IL10, TGFβ1, MMP2 upregulated with CSDEX/CSNP (p < 0.05). CSDEX/CSRB in animal study significantly reduced resorption, ankylosis, TRAP activity and osteocalcin expression and increased periostin (p<0.05). CSDEX demonstrated higher anti-inflammatory activity by downregulating TNFα, while CSNP upregulated TGFβ1, periostin, and downregulated MMP9. The combination of matrix stabilization with CSRB with periostin upregulation and sustained releasing CSDEX showed potential for hampering root resorption and ankylosis in dental avulsion.

Vertical root fractures in root treated teeth-current status and future trends

Vertical root fracture (VRF) is a common reason for the extraction of root filled teeth. The accurate diagnosis of VRF may be challenging due to the absence of clinical signs, whilst conventional radiographic assessment is often inconclusive. However, an understanding of the aetiology of VRFs, and more importantly, the key predisposing factors, is crucial in identifying teeth that may be susceptible. Thorough clinical examination with magnification and co-axial lighting is essential in identifying VRFs, and although CBCT is unable to reliably detect VRFs per se, the pattern of bone loss typically associated with VRF can be fully appreciated, and therefore, increases the probability of correct diagnosis and management. The prevalence of VRFs in root filled teeth is significantly greater than in teeth with vital pulps, demonstrating that the combination of loss of structural integrity, presence of pre-existing fractures and biochemical effects of loss of vitality, are highly relevant. Careful assessment of the occlusal scheme, presence of deflective contacts and identification of parafunctional habits is imperative in both preventing and managing VRFs. Furthermore, anatomical factors such as root canal morphology, may predispose certain teeth to VRF. The influence of access cavity design and root canal instrumentation protocols should be considered although the impact of these on the fracture resistance of root filled teeth is not clearly validated. The post-endodontic restoration of root filled teeth should be expedient and considerate to the residual tooth structure. Posts should be placed 'passively' and excessive 'post-space' preparation should be avoided. This narrative review aims to present the aetiology, potential predisposing factors, histopathology, diagnosis and management of VRF and present perspectives for future research. Currently, there are limited options other than extraction for the management of VRF, although root resection may be considered in multi-rooted teeth. Innovative techniques to 'repair' VRFs using both orthograde and surgical approaches require further research and validation. The prevention of VRFs is critical; identifying susceptible teeth, utilizing conservative endodontic procedures, together with expedient and appropriate post-endodontic restorative procedures is paramount to reducing the incidence of terminal VRFs.

Engineering a novel stem cells from apical papilla - macrophages organoid for regenerative endodontics

INTRODUCTION

Three-dimension (3D) tissue-construct with a heterogeneous cell population is critical to understand the interactions between immune cells and stem cells from apical papilla (SCAP) in the periapical region for developing treatment strategies in regenerative endodontics. This study aims to develop and characterize a 3D tissue-construct with binary cell system for studying the interactions between SCAP and macrophages in presence of lipopolysaccharide (LPS - pro-inflammatory) and interleukin-4 (IL-4 - anti-inflammatory) environments.

METHODS

SCAP and macrophages were seeded in the 3D printed dumbbell-shaped molds to generate tissue-constructs with binary cell population. Two experimental (LPS and IL-4) and control (non-stimulation) conditions were applied to the tissue-constructs to determine the characteristics of the tissue-construct, volume of viable cells and their morphology using a confocal laser scanning microscopy from 0 to 7 days period. Experiments were conducted in triplicates and data were analyzed with trend analysis and two-way analysis of variance at the significance of p < 0.05.

RESULTS

The tissue-constructs revealed distinct SCAP-macrophage interaction in pro-/anti-inflammatory environments. SCAP displayed characteristic self-organization as a cap-shaped structure in the tissue-construct. The growth of cells and cell-to-cell as well as cell-to-matrix interactions resulted in 70% and 30% decreased dimension of the tissue graft on the SCAP side and macrophage side respectively at day 7 (p < 0.0001). The tissue environments influenced macrophages-SCAP interactions, resulting in altered viable cell volume (p < 0.05), morphology and structural organization.

CONCLUSIONS

This study developed and characterized an apical papilla organoid in a 3D collagen based tissue-construct for studying SCAP-macrophage crosstalk in tissue regeneration as well as repair.

Local immunomodulatory effects of intracanal medications in apical periodontitis

The immune system is an extremely complex biological network that plays a crucial role in the hemostasis of periapical tissue, pathogenesis of apical periodontitis (AP) as well as periapical tissue healing. The successful elimination of microbial infections remains a significant challenge, mostly due to the ever-growing development of antimicrobial-resistant pathogens. The bacterial endurance in the root canal system contributes to features ranging from altered post-treatment healing to exacerbation of chronic periradicular immune response, that compromise the outcome of endodontic treatment. A highly effective strategy for combating infectious diseases and the associated inflammation-mediated tissue damage is to modulate the host immune response in conjunction with antimicrobial therapy. There are several medications currently used in endodontic treatment, however, they suffer various levels of microbial resistance and do not deliver all the required characteristics to simultaneously address both intracanal bacteria and periapical inflammation. Interaction of antimicrobial agents with the immune system can impact its function, leading to immune-suppressive or immune-stimulatory effects. The group of non-conventional antimicrobial medications, such as antimicrobial peptides, propolis, and nanomaterials, are agents that provide strong antimicrobial effectiveness and concomitant immunomodulatory and/or reparative effect, without any host tissue damages. Herein, we provide an overview of local immune modulation in AP and a comprehensive review of the immunomodulatory effect of antimicrobials intracanal medications applied in endodontics with specific emphasis on the antimicrobial nanomaterial-based approaches that provide immunomodulatory potential for successful clinical deployment in endodontics.

Proteomic profiling reveals engineered chitosan nanoparticles mediated cellular crosstalk and immunomodulation for therapeutic application in apical periodontitis

Macrophages (MQ) are major constituents of chronically inflamed periapical tissues in apical periodontitis. This study aimed to investigate the immunomodulatory effect of engineered bioactive chitosan-based nanoparticles (CSnp) antibiofilm medication on MQ cocultured with periodontal ligament fibroblasts (PdLF). Cells viability, spreading, PdLF migration, and intracellular CSnp uptake were characterized. Tandem Mass Tag-based proteomics was applied to analyze MQ global protein expression profiles after interaction with Enterococcus faecalis biofilm, CSnp-treated biofilm, and CSnp. Secreted inflammatory mediators were analyzed. Following bioinformatics analyses, candidate proteins were validated via targeted proteomics. CSnp maintained cells viability, increased MQ spreading, and PdLF migration (p < 0.05). Transmission electron micrographs demonstrated CSnp internalization via macropinocytosis, clathrin-mediated endocytosis, and phagocytosis. Proteomic analysis revealed that CSnp-treated biofilm upregulated proteins (>1.5-folds, p < 0.05) showed functional enrichment in the pathway of metal sequestration by antimicrobial proteins, while downregulated proteins showed enrichment in ferroptosis. CSnp upregulated proteins exhibiting antioxidant and immunoregulatory properties. Upregulation of SERPINB1 by CSnp (>1.5-folds, p < 0.05) was validated. CSnp-treated biofilm reduced pro-inflammatory IL-1β and nitric oxide but enhanced anti-inflammatory IL-10 and TGF-β1 (p < 0.05). Internalized engineered bioactive CSnp reprogrammed MQ proteomic and cytokine profiles to modulate biofilm-mediated inflammation, and prompted PdLF migration, emphasizing its potential to regulate healing process in the treatment of apical periodontitis.

•

CSnp internalized via macropinocytosis, clathrin-mediated endocytosis, and phagocytosis.

•

Enterococcus faecalis biofilm altered macrophage proteomic profile.

•

Macrophage proteome upon CSnp-treated biofilm interaction was distinct from biofilm.

•

CSnp upregulated proteins with immunoregulatory and antioxidant activities.

•

CSnp reduced proinflammatory but increased anti-inflammatory mediators.

Vertical root fractures: A time-dependent clinical condition. A case-control study in two colombian populations

Background

This nested case-control study can be viewed as an efficient way to sample subjects from a large cohort study case-control study aimed to analyze the effect of different clinical factors on the appearance of vertical root fractures in endodontically-treated teeth (ETT) over time.

Material and Methods

By matching 90 cases and 270 controls nested in a cohort of 450 patients. Incident “cases” included those ETT in which a confirmed VRF. The “controls” were ETT with clinical and radiographic evidence of normality. When an “incident case” was detected, three random “controls” according to the evaluation time registered in years were selected. Time interval corresponded to the exposure time from the end of the endodontic treatment until the tooth was included in the study. Demographic and clinical parameters included: age, gender, type, and location of the tooth, type of endodontic treatment, number of appointments necessary to complete the endodontic treatment, use of intra-canal medication, the apical extension of the filling, type of coronal restoration, the role of the tooth in the rehabilitation treatment, presence of intra-radicular posts, and presence of an adjacent implant, were analyzed over time. Statistical analysis: univariate descriptive analysis, Pearson’s χ2 test, and a logistic regression model adjusted for the most significant variables with a 95% confidence interval.

Results

The prevalence of vertical root fractures was 16.42%. The multivariate analysis confirmed that re-treatment (OR:12.19; OR:4.28;P<0.05) lasting five to ten years and intra-canal medication (OR:6.16;P=0.004) for more than eleven years significantly more associated with the risk of vertical root fracture. For teeth with intra-canal post or direct coronal restorations, the risk of vertical root fracture was three times lower.

Conclusions

Endodontic re-treatment and the use of intracanal medication such as calcium hydroxide should be considered primary and secondary risk factors, respectively, according to the appearance of VRF over time.

Key words:Apical surgery, endodontic re-treatment, endodontically-treated teeth, risk factors, vertical root fracture.

Engineered Chitosan-based Nanoparticles Modulate Macrophage-Periodontal Ligament Fibroblast Interactions in Biofilm-mediated Inflammation

INTRODUCTION

Crosstalk between immune cells and tissue-resident cells regulates the pathophysiology and posttreatment healing of apical periodontitis. This investigation aimed to understand the influence of residual root canal biofilm on macrophage (MQ)-periodontal ligament fibroblast (PdLF) interaction and evaluate the effect of engineered chitosan-based nanoparticles (CSnp) on MQ-PdLF interactions in residual biofilm-mediated inflammation.

METHODS

Six-week-old Enterococcus faecalis biofilms in root canal models were disinfected conventionally using sodium hypochlorite alone or followed by calcium hydroxide medication or CSnp dispersed in carboxymethylated chitosan (CMCS). The effect of the treated biofilms (n = 25/group) on the inflammatory response of THP-1-differentiated MQ monoculture versus coculture with PdLF was evaluated for cell viability, MQ morphometric characterization, inflammatory mediators (nitric oxide, tumor necrosis factor alpha, interleukin [IL]-1 beta, IL-1RA, IL-6, transforming growth factor beta 1 [TGF-β1], and IL-10), and the expression of transcription factors (pSTAT1/pSTAT6)/cluster of differentiation markers (CD80/206) after 24, 48, and 72 hours of interaction. PdLF transwell migration was evaluated after 8 and 24 hours. Unstimulated cells served as the negative control, whereas untreated biofilm was the positive control.

RESULTS

Biofilm increased nitric oxide and IL-1β but suppressed IL-10, IL-1RA, and PdLF migration with significant cytotoxic effects. CSnp/CMCS reduced nitric oxide and IL-1β (P < .01) while maintaining ≥90% cell survival up to 72 hours with evident M2-like MQ phenotypic changes in coculture. CSnp/CMCS also increased the IL-1RA/IL-1β ratio and enhanced TGF-β1 production over time (P < .05, 72 hours). In coculture, CSnp/CMCS showed the highest IL-10 level at 72 hours (P < .01), reduced the pSTAT1/pSTAT6 ratio, and enhanced PdLF migration (P < .01, 24 hours).

CONCLUSIONS

CSnp/CMCS medication facilitated MQ switch toward M2 (regulatory/anti-inflammatory) phenotype and PdLF migration via paracrine signaling.

A Novel Self-Mineralizing Antibacterial Tissue Repair Varnish to Condition Root-end Dentin in Endodontic Microsurgery

INTRODUCTION

A novel 2-part varnish system containing chitosan nanoparticles (part 1) and chitosan-grafted hydroxyapatite precursor nanocomplex (part 2) was developed to condition the root-end dentin using the principle of biomineralization while rendering both antimicrobial efficacy and bioactivity. This in vitro study aimed to characterize and assess the effectiveness of the chitosan nanoparticles and chitosan-grafted hydroxyapatite precursor nanocomplex containing self-mineralizing antibacterial tissue repair varnish to condition as well as seal root-end dentin during endodontic microsurgery.

METHODS

In phase 1, the antibacterial properties and cellular response of the varnish were characterized. The antibacterial activity and cellular responses were evaluated using Enterococcus faecalis and periodontal ligament (PDL) fibroblasts, respectively. In phase 2, a resected root-end model was used to apply the 2-part varnish and examine the dentin-varnish interface using transmission electron microscopy. The percentage of root end sealed with time was determined using scanning electron microscopy (n = 6/time point). Statistical analysis was performed using 1-way analysis of variance where applicable.

RESULTS

The part 1 and 2 of the varnish displayed significant antibacterial activity and reduced bacterial adherence/survival (P < .01). The attachment and spreading of PDL fibroblasts on the varnish-conditioned dentin was enhanced compared with unconditioned dentin (P < .01). In the resected root-end model, the 2-part varnish displayed a biomineralized varnish layer with close interaction with the subsurface dentin. Root-end coverage with the biomineralized layer increased with incubation time (P < .01), reaching approximately 95% coverage after 24 hours.

CONCLUSIONS

The 2-part varnish system effectively conditioned/sealed the root end with a biomineralized layer while reducing bacterial load and promoting PDL fibroblast attachment. This therapeutic modification of root-end dentin could provide optimal conditions to enhance healing and improve prognosis in teeth with root-end cracks after endodontic microsurgery.