In vivo experimental model of orthotopic dental pulp regeneration under the influence of photobiomodulation therapy

The effect of photobiomodulation therapy in common maxillofacial injuries: Current status

The use of photobiomodulation therapy (PBMT) may be used for treating trauma to the maxillofacial region. The effects of PBMT on maxillofacial injuries were discussed in this review article. The electronic databases Pubmed, Scopus, and Web of Science were thoroughly searched. This review included in vitro, in vivo, and clinical studies describing how PBMT can be used in maxillofacial tissue engineering and regenerative medicine. Some studies suggest that PBMT may offer a promising therapy for traumatic maxillofacial injuries because it can stimulate the differentiation and proliferation of various cells, including dental pulp cells and mesenchymal stem cells, enhancing bone regeneration and osseointegration. PBMT reduces pain and swelling after oral surgery and tooth extraction in human and animal models of maxillofacial injuries. Patients with temporomandibular disorders also benefit from PBMT in terms of reduced inflammation and symptoms. PBMT still has some limitations, such as the need for standardizing parameters. PBMT must also be evaluated further in randomized controlled trials in various maxillofacial injuries. As a result, PBMT offers a safe and noninvasive treatment option for patients suffering from traumatic maxillofacial injuries. PBMT still requires further research to establish its efficacy in clinical practice and determine the optimal parameters.

The Effects of Antimicrobial Photodynamic Therapy Used to Sterilize Carious Dentin on Rat Dental Pulp Tissue

Antimicrobial photodynamic therapy (aPDT) used to sterilize carious dentin may irritate pulp tissues because of tissue-penetrating laser and singlet oxygen generation. This study aimed to assess the effects of aPDT on rat pulp tissues. A cavity formed in a rat maxillary first molar was treated with aPDT. The combined photosensitizer and laser irradiation conditions in the aPDT groups were as follows: methylene blue and 100 mW for 60 s, brilliant blue (BB) and 100 mW for 60 s, BB and 50 mW for 120 s, and BB and 200 mW for 30 s. Each cavity was treated with an all-in-one adhesive and filled with flowable resin. aPDT was not applied for the control. In each group, the rats were sacrificed on postoperative days 1 and 14, and thin sections of the treated teeth were prepared. Pulp tissue disorganization (PTD), inflammatory cell infiltration (ICI), and tertiary dentin formation (TDF) were evaluated. At 1-day evaluation, there were significant differences between the aPDT group and controls with respect to PTD and ICI (p < 0.01); 14 days later, almost all specimens showed tertiary dentin formation. The application of aPDT caused reversible damage to the rat pulp, while in the long term, healing occurred with the formation of tertiary dentin.

In vitro, ex vivo, and in vivo models for dental pulp regeneration

Based on the concept of tissue engineering (Cells-Scaffold-Bioactive molecules), regenerative endodontics appeared as a new notion for dental endodontic treatment. Its approaches aim to preserve dental pulp vitality (pulp capping) or to regenerate a vascularized pulp-like tissue inside necrotic root canals by cell homing. To improve the methods of tissue engineering for pulp regeneration, numerous studies using in vitro, ex vivo, and in vivo models have been performed. This review explores the evolution of laboratory models used in such studies and classifies them according to different criteria. It starts from the initial two-dimensional in vitro models that allowed characterization of stem cell behavior, through 3D culture matrices combined with dental tissue and finally arrives at the more challenging ex vivo and in vivo models. The travel which follows the elaboration of such models reveals the difficulty in establishing reproducible laboratory models for dental pulp regeneration. The development of well-established protocols and new laboratory ex vivo and in vivo models in the field of pulp regeneration would lead to consistent results, reduction of animal experimentation, and facilitation of the translation to clinical practice.

Photobiomodulation Therapy and Pulp-Regenerative Endodontics: A Narrative Review

Regenerative endodontic procedures (REPs) were used to recover the dental pulp’s vitality in order to avoid the undesirable outcomes of conventional endodontic treatment and to promote dentinal formation, especially for immature permanent teeth. Photobiomodulation therapy (PBMT) exhibits photobiological and photochemical effects for improving the root canal’s environmental conditions by compensating for oxidative stress and increasing the blood supply to implanted stem cells and improving their survival. Basic research has revealed that PBMT can modulate human dental pulp stem cells’ (hDPSCs) differentiation, proliferation, and activity, and subsequent tissue activation. However, many unclear points still remain regarding the mechanisms of action induced by PBMT in REPs. Therefore, in this review, we present the applications of laser and PBMT irradiation to the procedures of REPs and in endodontics. In addition, the effects of PBMT on the regenerative processes of hDPSCs are reviewed from biochemical and cytological perspectives on the basis of the available literature. Furthermore, we consider the feasibility of treatment in which PBMT irradiation is applied to stem cells, including dental pulp stem cells, and we discuss research that has reported on its effect.

Tissue Characteristics in Endodontic Regeneration: A Systematic Review

The regenerative endodontic procedure (REP) represents a treatment option for immature necrotic teeth with a periapical lesion. Currently, this therapy has a wide field of pre-clinical and clinical applications, but no standardization exists regarding successful criteria. Thus, by analysis of animal and human studies, the aim of this systematic review was to highlight the main characteristics of the tissue generated by REP. A customized search of PubMed, EMBASE, Scopus, and Web of Science databases from January 2000 to January 2022 was conducted. Seventy-five human and forty-nine animal studies were selected. In humans, the evaluation criteria were clinical 2D and 3D radiographic examinations. Most of the studies identified a successful REP with an asymptomatic tooth, apical lesion healing, and increased root thickness and length. In animals, histological and radiological criteria were considered. Newly formed tissues in the canals were fibrous, cementum, or bone-like tissues along the dentine walls depending on the area of the root. REP assured tooth development and viability. However, further studies are needed to identify procedures to successfully reproduce the physiological structure and function of the dentin–pulp complex.

Pro-angiogenic potential of a functionalized hydrogel scaffold as a secretome delivery platform: An innovative strategy for cell homing-based dental pulp tissue engineering

Angiogenesis is a key process that provides a suitable environment for successful tissue engineering and is even more crucial in regenerative endodontic procedures, since the root canal anatomy limits the development of a vascular network supply. Thus, sustainable and accelerated vascularization of tissue-engineered dental pulp constructs remains a major challenge in cell homing approaches. This study aimed to functionalize a chitosan hydrogel scaffold (CS) as a platform loaded with secretomes of stem cells from human exfoliated deciduous teeth (SHEDs) and evaluate its bioactive function and pro-angiogenic properties. Initially, the CS was loaded with SHED secretomes (CS-S), and the release kinetics of several trophic factors were assessed. Proliferation and chemotaxis assays were performed to analyze the effect of functionalized scaffold on stem cells from apical papilla (SCAPs) and the angiogenic potential was analyzed through the Matrigel tube formation assay with co-cultured of human umbilical vein endothelial cells and SCAPs. SHEDs and SCAPs expressed typical levels of mesenchymal stem cell surface markers. CS-S was able to release the trophic factors in a sustained manner, but each factor has its own release kinetics. The CS-S group showed a significantly higher proliferation rate, accelerated the chemotaxis, and higher capacity to form vascular-like structures. CS-S provided a sustained and controlled release of trophic factors, which, in turn, improved proliferation, chemotaxis and all angiogenesis parameters in the co-culture. Thus, the functionalization of chitosan scaffolds loaded with secretomes is a promising platform for cell homing-based tissue engineering.

Nestin and NG2 transgenes reveal two populations of perivascular cells stimulated by photobiomodulation

Pericytes and glial cells are known to collaborate in dental pulp tissue repair. Cell-based therapies that stimulate these stromal components may be of therapeutic relevance for partially vital dental pulp conditions. This study aimed to examine the early effect of photobiomodulation (PBM) in pericytes from experimentally injured pulp tissue. To accomplish this, we used the Nestin-GFP/NG2-DsRed mice, which could allow the identification of distinct pericyte phenotypes. We discovered the presence of two pericytes subsets within the dental pulp, the Nestin ⁺ NG2⁺ (type-2) and Nestin^- NG2⁺ (type-1). Upon injury, PBM treatment led to a significant increase in Nestin⁺ cells and pericytes. This boost was mainly conferred by the more committed pericyte subset (NestinNG2⁺ ). PBM also stimulated terminal blood vessels sprouting adjacent to the injury site while maintaining signs of pulp vitality. In vitro, PBM induced VEGF upregulation, improved dental pulp cells proliferation and migration, and favored their mineralization potential. Herein, different subsets of perivascular cells were unveiled in the pulp tissue. PBM enhanced not only NG2⁺ cells but nestin-expressing progenitors in the injured dental pulp.

Development and characterization of a new chitosan-based scaffold associated with gelatin, microparticulate dentin and genipin for endodontic regeneration

OBJECTIVE

An ideal scaffold for endodontic regeneration should allow the predictableness of the new tissue organization and limit the negative impact of residual bacteria. Therefore, composition and functionalization of the scaffold play an important role in tissue bioengineering. The objective of this study was to assess the morphological, physicochemical, biological and antimicrobial properties of a new solid chitosan-based scaffold associated with gelatin, microparticulate dentin and genipin.

METHODS

Scaffolds based on chitosan (Ch); chitosan associated with gelatin and genipin (ChGG); and chitosan associated with gelatin, microparticulate dentin and genipin (ChGDG) were prepared by using the freeze-drying method. The morphology of the scaffolds was analyzed by scanning electron microscopy (SEM). The physicochemical properties were assessed for biodegradation, swelling and total released proteins. The biological aspects of the scaffolds were assessed using human cells from the apical papilla (hCAPs). Cell morphology and adhesion to the scaffolds were evaluated by SEM, cytotoxicity and cell proliferation by MTT reduction-assay. Cell differentiation in scaffolds was assessed by using alizarin red assay. The antimicrobial effect of the scaffolds was evaluated by using the bacterial culture method, and bacterial adhesion to the scaffolds was observed by SEM.

RESULTS

All the scaffolds presented porous structures. The ChCDG had more protein release, adhesion, proliferation and differentiation of hCAPs, and bacteriostatic effect on Enterococcus faecalis than Ch and ChGG (p < 0.05).

SIGNIFICANCE

The chitosan associated with gelatin, microparticulate dentin and genipin has morphological, physicochemical, biological and antibacterial characteristics suitable for their potential use as scaffold in regenerative endodontics.

Recovering the osteoblastic differentiation potential of mesenchymal stem cells derived from diabetic rats by photobiomodulation therapy

Autologous cell-based therapy for bone regeneration might be impaired by diabetes mellitus (DM) due to the negative effects on mesenchymal stem cells (MSCs) differentiation. Strategies to recover their osteogenic potential could optimize the results. We aimed to evaluate the effect of photobiomodulation (PBM) therapy on osteoblast differentiation of rats with induced DM. Bone marrow MSCs of healthy and diabetic rats were isolated and differentiated into osteoblasts (OB and dOB, respectively). dOB were treated with PBM therapy every 72 hour (660 nm; 0.14 J; 20 mW; 0.714 W/cm² , and 5 J/cm² ). Cell morphology, viability, gene and protein expression of osteoblastic markers, alkaline phosphatase (ALP) activity, and the mineralized matrix production of dOB-PBM were compared to dOB. PBM therapy improved viability of dOB, increased the gene and protein expression of bone markers, the ALP activity and the mineralized matrix production. PBM therapy represents an innovative therapeutic approach to optimize the treatment of bone defects in diabetic patients.

Physical and Biological Properties of a Chitosan Hydrogel Scaffold Associated to Photobiomodulation Therapy for Dental Pulp Regeneration: An In Vitro and In Vivo Study

Background

The regeneration of dental pulp, especially in cases of pulp death of immature teeth, is the goal of the regenerative endodontic procedures (REPs) that are based on tissue engineering principles, consisting of stem cells, growth factors, and scaffolds. Photobiomodulation therapy (PBMT) showed to improve dental pulp regeneration through cell homing approaches in preclinical studies and has been proposed as the fourth element of tissue engineering. However, when a blood clot was used as a scaffold in one of these previous studies, only 30% of success was achieved. The authors pointed out the instability of the blood clot as the regeneration shortcoming. Then, to circumvent this problem, a new scaffold was developed to be applied with the blood clot. The hypothesis of the present study was that an experimental injectable chitosan hydrogel would facilitate the three-dimensional spatial organization of endogenous stem cells in dental pulp regeneration with no interference on the positive influence of PBMT.

Methods

For the in vitro analysis, stem cells from the apical papilla (SCAPs) were characterized by flow cytometry and applied in the chitosan scaffold for evaluating adhesion, migration, and proliferation. For the in vivo analysis, the chitosan scaffold was applied in a rodent orthotopic dental pulp regeneration model under the influence of PBMT (660 nm; power output of 20 mW, beam area of 0.028 cm², and energy density of 5 J/cm²).

Results

The scaffold tested in this study allowed significantly higher viability, proliferation, and migration of SCAPs in vitro when PBMT was applied, especially with the energy density of 5 J/cm². These results were in consonance to those of the in vivo data, where pulp-like tissue formation was observed inside the root canal.

Conclusion

Chitosan hydrogel when applied with a blood clot and PBMT could in the future improve previous results of dental pulp regeneration through cell homing approaches.

Photobiomodulation as adjunctive therapy for guided bone regeneration. A microCT study in osteoporotic rat model

Regeneration of diseased bone is challenging. Guided bone regeneration (GBR) has been applied to favor the bone repair. Photobiomodulation (PBM) is also a recognized therapy able to improve bone repair in healthy and diseased individuals. Thus, with the hypothesis that PBM therapy could improve the GBR of diseased bone, this study evaluated the effect of PBM as adjunctive therapy to GBR in osteoporotic rats. Osteoporosis was induced in rats using the oophorectomy model. Then, 5-mm calvaria bone defects were created and treated according to the experimental groups, as follows: with no further treatment (Control); conventional GBR (Membrane), GBR and PBM applied with 3 s, 4 J/cm² and 0.12 J per point (PBM-1) and GBR and PBM applied with 10s, 14 J/cm², 0.4 J per point (PBM-2). PBM therapy (808 nm, 40 mW, 1.42 W/cm²) was applied immediately, 48 and 96 h postoperatively. Four and eight weeks later, the samples were harvested and processed for micro-computerized tomography (Micro CT). Data were statistically compared (p < 0.05). From 4 to 8 weeks mostly significant changes were observed in the PBM groups. The bone volume fraction and number of trabeculae of the PBM groups, especially the PBM-1, were significantly higher than those of Control (p < 0.0001). The values of thickness and separation of the trabeculae and structural model index of the PBM groups were significantly smaller than Control (p < 0.0001). The connectivity density was significantly higher on Membrane and PBM groups than Control (p < 0.0004). The application of PBM as adjunctive therapy to GBR results in enhanced bone formation and maturation in comparison to the conventional GBR in the regeneration of lesions of osteoporotic bone in rats. Overviewing the challenges that face bone regeneration in patients with osteoporosis, our findings open new perspectives on the treatment of bone defects under osteoporotic conditions.

Cytotoxic, Migration, and Angiogenic Effects of Photodynamic Therapy and Photobiomodulation Associated with a Revascularization Protocol

INTRODUCTION

This study evaluated photodynamic therapy (PDT) and photobiomodulation therapy (PBM) as adjuncts to pulp revascularization using cultures of apical papilla cells (APCs) and endothelial cells (HUVECs).

METHODS

The root canal and apical foramen of 2 mandibular first premolars were enlarged to simulate immature teeth. The canal of 1 tooth was filled with 1 mL 0.005% methylene blue (MB). After that, the canals of both teeth were irrigated with 20 mL 1.5% sodium hypochlorite (NaOCl) and 20 mL 17% EDTA. The resulting solutions were diluted in cell culture media at a concentration of 0.5% (0.5% MB + NaOCl + EDTA and 0.5% NaOCl + EDTA). After PDT (0.5% MB + NaOCl + EDTA + PDT) and PBM (0.5% NaOCl + EDTA + PBM) applications, the effects were evaluated to determine cytotoxicity, polarity index, APC migration, and HUVEC sprouting, and results were compared with those of their controls (solutions without laser application). Cell culture media (CT) was also used as a control. Data were analyzed using 1-way analysis of variance and the Tukey post hoc test (P ≤ .05).

RESULTS

PDT and PBM promoted greater APC viability than their controls, and PDT had greater cell viability than CT (P < .05). All protocols reduced APC migration when compared with CT (P < .05). HUVEC sprouts grown out of spheroids in PBM had a greater ratio area than their control (P ≤ .01), and the PDT ratio of the spheroid area was similar to that of its control (P > .05).

CONCLUSIONS

PBM and PDT seem to be potentially effective adjuncts to revascularization in nonvital immature teeth.

Influence of photobiomodulation therapy on root development of rat molars with open apex and pulp necrosis

This study aimed to evaluate the role of photobiomodulation (PBM) in apexification and apexogenesis of necrotic rat molars with an open apex. Rat molars were exposed to the oral environment for 3 weeks. Canals were rinsed with 2.5% NaOCl and 17% EDTA, filled with antibiotic paste and sealed. After 7 days, canals were rinsed and divided into six groups (n=6): mineral trioxide aggregate (MTA); blood clot (BC); human dental pulp stem cells (hDPSC); MTA+PBM; BC+PBM; and hDPSC+PBM. In hDPSC groups, a 1% agarose gel scaffold was used. Two groups were not exposed: healthy tooth+PBM (n = 6), healthy tooth (n = 3); and one was exposed throughout the experiment: necrotic tooth (n = 3). In PBM groups, irradiation was performed with aluminum gallium indium phosphide (InGaAlP) diode laser for 30 days within 24-h intervals. After that, the specimens were processed for histological and immunohistochemical analyses. Necrotic tooth showed greater neutrophil infiltrate (p < 0.05). Necrotic tooth, healthy tooth, and healthy tooth+PBM groups showed absence of a thin layer of fibrous condensation in the periapical area. All the other groups stimulated the formation of a thicker layer of fibers (p < 0.05). All groups formed more mineralized tissue than necrotic tooth (p < 0.05). PBM associated with MTA, BC, or hDPSC formed more mineralized tissue (p < 0.05). MTA+PBM induced apexification (p < 0.05). Rabbit polyclonal anti-bone sialoprotein (BSP) antibody confirmed the histological findings of mineralized tissue formation, and hDPSC groups exhibited higher percentage of BSP-positive cells. It can be concluded that PBM improved apexification and favored apexogenesis in necrotic rat molars with an open apex.

Angiogenic properties of dental pulp stem cells conditioned medium on endothelial cells in vitro and in rodent orthotopic dental pulp regeneration

Objectives

To evaluate the effect of SHED-CM on the proliferation, differentiation, migration ability, cell death, gene expression and production of VEGF of HUVEC in vitro and in a rodent orthotopic dental pulp regeneration.

Methods

Three culture media [M199, DMEM/Ham's F12 and DMEM/Ham's F12 conditioned by SHEDs] were used as experimental groups. SHED-CM was prepared maintaining confluent cells in culture without serum for 3 days. The proliferation and cell death marker of HUVECs were assessed using flow cytometry. The capacity of formation of vascular-like structures was analyzed in cells grown over Matrigel^® in hypoxic condition. HUVECs migration was followed using the scratch test. VEGF-A expression in HUVECs was assessed using real time RT-qPCR; and VEGF synthesis with ELISA test. SHED-CM was also applied in rodent ortotopic model of dental pulp regeneration in rats. The formed tissue was submitted to histological and immunohistochemical analyses.

Results

SHED-CM promoted significantly lower expression of 7AAD in HUVECs; whereas the expression of the Ki67 was similar in all groups. The vascular-like structures were observed in all groups. Migration of SHED-CM group was faster than DMEM/Ham's F12. SHED-CM induced similar expression of VEGF-A than M199, and higher than DMEM/Ham's F12. SHED-CM induced significantly higher VEGF synthesis than other media. SHED-CM induced formation of a vascularized connective tissue inside the root canal.

Conclusion

The study showed that SHEDs release angiogenic and cytoprotective factors, which are of great importance for tissue engineering.

Clinical significance

SHED-CM could be an option to the use of stem cells in tissue engineering.

Screening of hydrogel-based scaffolds for dental pulp regeneration-A systematic review

OBJECTIVE

The aim of this systematic review was to evaluate the most appropriate hydrogel scaffold type (natural, synthetic or hybrid) to be applied with stem cells for dental pulp regeneration. The findings should help clinicians make an informed choice about the appropriate scaffold to be applied for this approach.

DESIGN

Three electronic databases were searched (Medline, Web of Science and Scopus). The review was conducted based on the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA).

RESULTS

From 4990 potentially relevant studies initially identified, 18 papers fulfilled the eligibility criteria and were considered for this review. Natural scaffolds were applied in most studies. Collagen was the most studied scaffold. In 5 of 10 studies, only growth factors were added to the constructs. Even without growth factors, these scaffolds containing stem cells were able to support the formation of dentin. The synthetic scaffolds were the least studied. Only 4 studies were selected, and in 3 of them, the same scaffold (Puramatrix) was evaluated. Puramatrix by itself was unable to form dental pulp when dental pulp stem cells were not present. Synthetic and hybrid hydrogels were unable to attract stem cells from the host. The presence of growth factors in these constructs seems to be of relevance since dental pulp tissue formation was achieved only when the hybrid scaffold was applied with growth factors.

CONCLUSION

All types of hydrogel-based scaffolds, when containing mesenchymal stem cells, are able to form connective tissue with different degrees of similarity to dental pulp. However, current data is too heterogeneous to compare and identify the advantages of any specific scaffold.

Pulp Regeneration Concepts for Nonvital Teeth: From Tissue Engineering to Clinical Approaches

Following the basis of tissue engineering (Cells-Scaffold-Bioactive molecules), regenerative endodontic has emerged as a new concept of dental treatment. Clinical procedures have been proposed by endodontic practitioners willing to promote regenerative therapy. Preserving pulp vitality was a first approach. Later procedures aimed to regenerate a vascularized pulp in necrotic root canals. However, there is still no protocol allowing an effective regeneration of necrotic pulp tissue either in immature or mature teeth. This review explores in vitro and preclinical concepts developed during the last decade, especially the potential use of stem cells, bioactive molecules, and scaffolds, and makes a comparison with the goals achieved so far in clinical practice. Regeneration of pulp-like tissue has been shown in various experimental conditions. However, the appropriate techniques are currently in a developmental stage. The ideal combination of scaffolds and growth factors to obtain a complete regeneration of the pulp-dentin complex is still unknown. The use of stem cells, especially from pulp origin, sounds promising for pulp regeneration therapy, but it has not been applied so far for clinical endodontics, in case of necrotic teeth. The gap observed between the hope raised from in vitro experiments and the reality of endodontic treatments suggests that clinical success may be achieved without external stem cell application. Therefore, procedures using the concept of cell homing, through evoked bleeding that permit to recreate a living tissue that mimics the original pulp has been proposed. Perspectives for pulp tissue engineering in the near future include a better control of clinical parameters and pragmatic approach of the experimental results (autologous stem cells from cell homing, controlled release of growth factors). In the coming years, this therapeutic strategy will probably become a clinical reality, even for mature necrotic teeth.

Immunohistological study of the effect of vascular Endothelial Growth Factor on the angiogenesis of mature root canals in rat molars

Tissue bioengineering has been applied to Endodontics to seek a more biological treatment. The presence of blood vessels is crucial for cell nutrition during tissue formation.