Mineral trioxide aggregate improves healing response of periodontal tissue to injury in mice

Synthetic materials in craniofacial regenerative medicine: A comprehensive overview

The state-of-the-art approach to regenerating different tissues and organs is tissue engineering which includes the three parts of stem cells (SCs), scaffolds, and growth factors. Cellular behaviors such as propagation, differentiation, and assembling the extracellular matrix (ECM) are influenced by the cell's microenvironment. Imitating the cell's natural environment, such as scaffolds, is vital to create appropriate tissue. Craniofacial tissue engineering refers to regenerating tissues found in the brain and the face parts such as bone, muscle, and artery. More biocompatible and biodegradable scaffolds are more commensurate with tissue remodeling and more appropriate for cell culture, signaling, and adhesion. Synthetic materials play significant roles and have become more prevalent in medical applications. They have also been used in different forms for producing a microenvironment as ECM for cells. Synthetic scaffolds may be comprised of polymers, bioceramics, or hybrids of natural/synthetic materials. Synthetic scaffolds have produced ECM-like materials that can properly mimic and regulate the tissue microenvironment's physical, mechanical, chemical, and biological properties, manage adherence of biomolecules and adjust the material's degradability. The present review article is focused on synthetic materials used in craniofacial tissue engineering in recent decades.

Use of scaffolds and regenerative materials for the treatment of immature necrotic permanent teeth with periapical lesion: Umbrella review

BACKGROUND

Current treatment of immature necrotic permanent teeth with a periapical lesion is regenerative endodontics, which is based on tissue engineering under the triade of stem cells, scaffolds and bioactive molecules.

OBJECTIVES

This Umbrella Review was aimed to evaluate the success of scaffold and regenerative materials used for the treatment of these teeth, in terms of apical closure, tooth length increase, widening of root canal walls, tissue vitality and periapical lesion repair.

METHODS

An extensive literature research was carried out in the Medline, ISI Web of Science, and Scopus databases for relevant systematic reviews matching the keyword search strategy. Based on inclusion and exclusion criteria, reviewers independently rated the quality of each study to determine their level of evidence. Methodological quality assessment of each article was obtained using A Measurement Tool to Assess Systematic Reviews (AMSTAR)-2 tool, and risk of bias was assessed with the Risk of Bias in Systematic Reviews (ROBIS) tool.

RESULTS

After removing duplicates, 155 articles were found; from which 133 were excluded for being non-relevant and 15 other due to exclusion criteria. One more was discarded after methodological quality evaluation, for a total of six articles remaining. The most common scaffold used was the blood clot, others used were poly lactic-co-glycolic acid and platelet-rich fibrin matrix. The most common regeneration material used was Mineral Trioxide Aggregate (MTA), followed by Biodentine. An increase in tooth length and widening of root canal walls were reported in all selected studies with different proportions, as well as periapical lesion repair. ROBIS analysis showed that only one article had low bias, two were classified as unclear bias, while the remaining three had high risk of bias.

DISCUSSION

An exhaustive literature search was carried out applying language filters, high-quality indexed journals, year of publication, which ensures the best quality articles were included. Blood clot was the most used scaffold as is the most easy to place inside the canal and does not require to extract blood from the patient. The use of MTA and Biodentine as sealing materials has been associated with thickening of canal walls, apical closure and reduced signs and symptoms of apical periodontitis. However, most of the included reviews assessed were case reports and only in a few of them were clinical trials included. There is also a lack of risk of bias analysis in most reviews.

CONCLUSION

The blood clot is the most common scaffold used for inducing regeneration during the treatment of immature necrotic teeth. Tooth length increase and widening of root canal walls are the most common criteria used in the studies as success indicators. MTA and Biodentine did not show differences in the results analysed. Quality assessment and bias risk evaluation showed that it is necessary to design better studies with rigorous methodology to recommend a trustable and predictable protocol for the treatment of immature necrotic permanent teeth with periapical lesions.

REGISTRATION

International Prospective Register of Systematic Reviews (PROSPERO) CRD42021248404.

An evaluation of a new high-sensitivity PrestoBlue assay for measuring cell viability and drug cytotoxicity using EA.hy926 endothelial cells

INTRODUCTION

Commercially-available resazurin-based reagents used for cell viability assessment contain varying amounts of resorufin; these may contribute to differences in autofluorescence, signal-to-background (S/B) ratio and the dynamic range of the assay.

OBJECTIVES

This in vitro study compares the sensitivity of a new, high-sensitivity PrestoBlue (hs-PB) assay with standard PrestoBlue (PB) in assessing the efficacy of valinomycin and antimycin A in human vascular endothelial EA.hy926 cells, as well as cell viability.

METHODS

The metabolic activity of EA.hy926 was evaluated based on resorufin fluorescence or formazan absorbance.

RESULTS

The hs-PB assay demonstrated lower resorufin autofluorescence than the PB, resulting in a ≥ 1.4-fold increase in S/B ratio in hs-PB compared to PB. Valinomycin was more potent cytotoxic agent than antimycin A. The hs-PB, PB and MTT produced similar IC₅₀ values for valinomycin. Antimycin A demonstrated significantly higher potency in the MTT than in the resazurin-based assays. The EA.hy926 cells demonstrated higher metabolic activity in the presence of the antimycin A solvent - DMSO.

CONCLUSION

All the examined methods may be used interchangeably to analyze drug cytotoxicity. Any differences in drug cytotoxicity observed between the assays may be due to relatively low drug potency and/or the influence of solvent on metabolism of assay reagent. The hs-PB assay appears to more effectively detect cell viability and produce a stronger signal than its conventional counterpart.

Mineral trioxide aggregate immersed in sodium hypochlorite reduce the osteoblastic differentiation of human periodontal ligament stem cells

White mineral trioxide aggregate (WMTA) is a root canal treatment material, which is known to exhibit a dark brown color when in contact with sodium hypochlorite solution (NaOCl). This study aimed to investigate the effects of NaOCl on the surface properties of WMTA discs and WMTA-induced osteoblastic differentiation of periodontal ligament stem cells (PDLSCs). Mixed WMTA (ProRoot MTA) was filled into the molds to form WMTA discs. These discs were immersed in distilled water (D-WMTA) or 5% NaOCl (Na-WMTA). Their surface structures and Ca²⁺ release level was investigated. Moreover, they were cultured with a clonal human PDLSC line (line 1–17 cells). The main crystal structures of Na-WMTA were identical to the structures of D-WMTA. Globular aggregates with polygonal and needle-like crystals were found on D-WMTA and Na-WMTA, which included Ca, Si, Al, C and O. However, many amorphous structures were also identified on Na-WMTA. These structures consisted of Na and Cl, but did not include Ca. NaOCl immersion also reduced Ca²⁺ release level from whole WMTA discs. Line 1–17 cells cultured with D-WMTA formed many mineralized nodules and exhibited high expression levels of osteoblast-related genes. However, cells incubated with Na-WMTA generated a small number of nodules and showed low expression levels of osteoblast-related genes. These results indicated that NaOCl reduced Ca²⁺ release from WMTA by generating amorphous structures and changing its elemental distribution. NaOCl may also partially abolish the ability of WMTA to stimulate osteoblastic differentiation of PDLSCs.

In vitro biocompatibility and bioactivity of calcium silicate‑based bioceramics in endodontics (Review)

Calcium silicate-based bioceramics have been applied in endodontics as advantageous materials for years. In addition to excellent physical and chemical properties, the biocompatibility and bioactivity of calcium silicate-based bioceramics also serve an important role in endodontics according to previous research reports. Firstly, bioceramics affect cellular behavior of cells such as stem cells, osteoblasts, osteoclasts, fibroblasts and immune cells. On the other hand, cell reaction to bioceramics determines the effect of wound healing and tissue repair following bioceramics implantation. The aim of the present review was to provide an overview of calcium silicate-based bioceramics currently applied in endodontics, including mineral trioxide aggregate, Bioaggregate, Biodentine and iRoot, focusing on their in vitro biocompatibility and bioactivity. Understanding their underlying mechanism may help to ensure these materials are applied appropriately in endodontics.

In Vitro Effect of Putty Calcium Silicate Materials on Human Periodontal Ligament Stem Cells

New bioactive materials have been developed for retrograde root filling. These materials come into contact with vital tissues and facilitate biomineralization and apical repair. The objective of this study was to evaluate the cytocompatibility and bioactivity of two bioactive cements, Bio-C Repair (Angelus, Londrina, Pr, Brazil) and TotalFill BC RRM putty (FGK, Dentaire SA, La-Chaux-de-fonds, Switzerland). The biological properties in human periodontal ligament stem cells (hPDLSCs) that were exposed to Bio-C Repair and TotalFill BC RRM putty were studied. Cell viability, migration, and cell adhesion were analyzed. Moreover, qPCR and mineralization assay were performed to evaluate the bioactivity potential of these cements. The results were statistically analyzed using ANOVA and the Tukey test (p < 0.05). It was observed that cell viability and cell migration in Bio-C Repair and TotalFill BC RRM putty were similar to the control without statistically significant differences, except at 72 h when TotalFill BC RRM putty was slightly lower (p < 0.05). Excellent cell adhesion and morphology were observed with both Bio-C Repair and TotalFill BC RRM putty. Both cements promoted the osteo- and cementogenic differentiation of hPDLSCs. These results suggest that Bio-C Repair and TotalFill BC RRM putty are biologically appropriate materials to be used as retrograde obturation material.

A comparison of the sealing abilities between Biodentine and MTA as root-end filling materials and their effects on bone healing in dogs after periradicular surgery

Objectives:

To compare the sealing ability and biocompatibility of Biodentine with mineral trioxide aggregate (MTA) when used as root-end filling materials.

Methodology:

The Cell Counting Kit-8 (CCK-8) assay was used to compare the cytotoxicity of MTA and Biodentine. Twenty-one extracted teeth with a single canal were immersed in an acidic silver nitrate solution after root-end filling. Then, the volume and depth of silver nitrate that infiltrated the apical portion of the teeth were analyzed using micro-computed tomography (micro-CT). Seventy-two roots from 3 female beagle dogs were randomly distributed into 3 groups and apical surgery was performed. After six months, the volume of the bone defect surrounding these roots was analyzed using micro-CT.

Results:

Based on the results of the CCK-8 assay, MTA and Biodentine did not show statistically significant differences in cytotoxicity (P>0.05). The volume and the depth of the infiltrated nitrate solution were greater in the MTA group than in the Biodentine group (P<0.05). The volume of the bone defect was larger in the MTA group than in the Biodentine group. However, the difference was not significant (P>0.05). The volumes of the bone defects in the MTA and Biodentine groups were smaller than the group without any filling materials (P<0.05).

Conclusions:

MTA and Biodentine exhibited comparable cellular biocompatibility. Biodentine showed a superior sealing ability to MTA in root-end filling. Both Biodentine and MTA promoted periradicular bone healing in beagle dog periradicular surgery models.

Histopathological, histoenzymological, immunohistochemical and immunofluorescence analysis of tissue response to sealing materials after furcation perforation

AIM

To evaluate in vivo tissue responses after sealing furcation perforations in dog's teeth with either Biodentine™, mineral trioxide aggregate (MTA) or gutta-percha, by means of histopathological, histoenzymological, immunohistochemical and immunofluorescence analysis.

METHODOLOGY

After root canal treatment, perforations were created in the central region of the pulp chamber floor using a round diamond bur and filled with one or other of the materials. The animals were euthanized after 120 days, and the teeth (n = 30) were processed for histopathological analysis of new mineralized tissue formation and collagen fibre reinsertion, immunohistochemical analysis of osteopontin (OPN) and alkaline phosphatase (ALP) and immunofluorescence analysis for bone morphogenetic protein (BMP-2), cementum attachment protein (CAP), bone sialoprotein (BSP), osteocalcin (OCN) and cementum protein1 (CEMP1). Histoenzymology was performed for TRAP activity and osteoclast count. Data were analysed statistically (α = 0.05) using chi-square and Kruskal-Wallis tests.

RESULTS

Gutta-percha did not induce mineralized tissue formation. MTA and Biodentine^TM formed mineralized tissue in 88% and 92% of specimens, respectively, with no significant difference (P > 0.05). Gutta-percha was associated with scattered collagen fibres parallel to the perforations. Groups treated with MTA or Biodentine^TM had partial fibre reinsertion perpendicular to the newly formed mineralized tissue. All materials induced OPN and ALP expression, weakest for gutta-percha and strongest for MTA (P < 0.05). Only MTA induced BMP-2, BSP, OCN, CAP and CEMP1 expression. Osteoclast counts were similar in all groups (P = 0.97).

CONCLUSIONS

Mineral trioxide aggregate and Biodentine^TM were biocompatible, with formation of mineralized tissue and partial reinsertion of collagen fibres. In addition, the participation of several molecules by which calcium silicate-based materials induce the formation of mineralized tissue were noted, with expression of ALP and OPN mineralization markers, without interference in the number of osteoclasts. Only MTA stimulated the expression of proteins associated with the formation of a cementum-like mineralized tissue.

Hyperglycemic condition influence on mineral trioxide aggregate biocompatibility and biomineralization

This study aimed to investigate in vitro and in vivo the influence of hyperglycemic condition on biocompatibility and biomineralization of gray mineral trioxide aggregate (GMTA) and white mineral trioxide aggregate (WMTA). For the in vitro study, fibroblast-like cells L929 were cultured under high or normal glucose concentration to investigate the effects of both MTA's on cell proliferation and inflammatory cytokines production IL-1β, IL-6, and TNF-α. For the in vivo study, polyethylene tubes containing MTA materials and empty tubes were implanted into dorsal connective tissues of Wistar rats previously assigned normal and hyperglycemic. After 7 and 30 days, the tubes with surrounding tissues were removed and subjected to histological, fluorescence and immunohistochemical analyzes of IL-1β, IL-6, and TNF-α. In vitro study showed that, under high glucose condition, GMTA reduced cell proliferation and IL-6 production compared with WMTA. Moreover, in vivo study revealed that hyperglycemic condition did not modify the inflammatory response and cytokines production in the tissue close to both materials. Independently of hyperglycemic status, mineralized areas were observed with both materials, but the fluorescence intensity of WMTA was diminished on 14 days in hyperglycemic animals. It is possible to conclude that GMTA was able to inhibit the proliferation rate and IL-6 production under high glucose concentration in vitro. Furthermore, cytokines production and inflammatory response were not upregulated in hyperglycemic animals; however, a decrease in the calcium deposition was observed in presence of WMTA, suggesting a delay in the mineralization process.

GuttaFlow Bioseal promotes spontaneous differentiation of human periodontal ligament stem cells into cementoblast-like cells

OBJECTIVES

To evaluate in vitro the cementogenic potential and the biological effects of GuttaFlow Bioseal, GuttaFlow 2, MTA Fillapex and AH Plus on human periodontal ligament stem cells (hPDLSCs).

METHODS

Cell viability, cell migration and cell morphology assays were performed using eluates of each material. To evaluate cell attachment, hPDLSCs were directly seeded onto the material surfaces and analyzed by scanning electron microscopy (SEM). The effects of endodontic sealers on cementum protein 1 (CEMP1), cementum-derived attachment protein (CAP), bone sialoprotein (BSP), ameloblastin (AMBN), amelogenin (AMELX) and alkaline phosphatase (ALP) gene expression on hPDLSCs were investigated by qPCR and immunofluorescence (IF). Statistical analysis was performed with analysis of variance and Bonferroni or Tukey post-test (α<0.05).

RESULTS

More than 90% of viable cells were obtained using extracts of GuttaFlow Bioseal and GuttaFlow2 after 72h of culture. By contrast, AH Plus and MTA Fillapex induced significantly lower levels of cell viability. GuttaFlow2 and GuttaFlow Bioseal promoted wound closure in a concentration-dependent manner, comparable to that observed with control extracts (*p<0.05). However, with AH Plus and MTA Fillapex, cell migration was significantly lower than in the control (***p<0.0001). SEM analysis pointed to an organized stress fiber assembly and high degree of cell adhesion on GuttaFlow Bioseal disks but low rates on GuttaFlow2, MTA Fillapex and AH Plus. When hPDLSCs were cultured with GuttaFlow Bioseal-conditioned media, qPCR assays and IF showed a higher level of AMELX, AMBN, CEMP1 and CAP expression than the control (*p<0.05)), whereas no such expression was observed in the other sealers.

SIGNIFICANCE

Our results showed that GuttaFlow sealers were more cytocompatible than AH Plus and MTA Fillapex, while GuttaFlow Bioseal favored cementoblast differentiation of hPDLSCs in the absence of any growth factors.

Enhanced tendon-to-bone repair through adhesive films

Tendon-to-bone surgical repairs have unacceptably high failure rates, possibly due to their inability to recreate the load transfer mechanisms of the native enthesis. Instead of distributing load across a wide attachment footprint area, surgical repairs concentrate shear stress on a small number of suture anchor points. This motivates development of technologies that distribute shear stresses away from suture anchors and across the enthesis footprint. Here, we present predictions and proof-of-concept experiments showing that mechanically-optimized adhesive films can mimic the natural load transfer mechanisms of the healthy attachment and increase the load tolerance of a repair. Mechanical optimization, based upon a shear lag model corroborated by a finite element analysis, revealed that adhesives with relatively high strength and low stiffness can, theoretically, strengthen tendon-to-bone repairs by over 10-fold. Lap shear testing using tendon and bone planks validated the mechanical models for a range of adhesive stiffnesses and strengths. Ex vivo human supraspinatus repairs of cadaveric tissues using multipartite adhesives showed substantial increase in strength. Results suggest that adhesive-enhanced repair can improve repair strength, and motivate a search for optimal adhesives.

STATEMENT OF SIGNIFICANCE

Current surgical techniques for tendon-to-bone repair have unacceptably high failure rates, indicating that the initial repair strength is insufficient to prevent gapping or rupture. In the rotator cuff, repair techniques apply compression over the repair interface to achieve contact healing between tendon and bone, but transfer almost all force in shear across only a few points where sutures puncture the tendon. Therefore, we evaluated the ability of an adhesive film, implanted between tendon and bone, to enhance repair strength and minimize the likelihood of rupture. Mechanical models demonstrated that optimally designed adhesives would improve repair strength by over 10-fold. Experiments using idealized and clinically-relevant repairs validated these models. This work demonstrates an opportunity to dramatically improve tendon-to-bone repair strength using adhesive films with appropriate material properties.