Bone, Periodontal and Dental Pulp Regeneration in Dentistry: A Systematic Scoping Review

Application of Biocompatible Scaffolds in Stem-Cell-Based Dental Tissue Engineering

Tissue engineering as an important field in regenerative medicine is a promising therapeutic approach to replace or regenerate injured tissues. It consists of three vital steps including the selection of suitable cells, formation of 3d scaffolds, and adding growth factors. Mesenchymal stem cells (MSCs) and embryonic stem cells (ESCs) are mentioned as two main sources for this approach that have been used for the treatment of various types of disorders. However, the main focus of literature in the field of dental tissue engineering is on utilizing MSCs. On the other hand, biocompatible scaffolds play a notable role in this regenerative process which is mentioned to be harmless with acceptable osteoinductivity. Their ability in inhibiting inflammatory responses also makes them powerful tools. Indeed, stem cell functions should be supported by biomaterials acting as scaffolds incorporated with biological signals. Naturally derived polymeric scaffolds and synthetically engineered polymeric/ceramic scaffolds are two main types of scaffolds regarding their materials that are defined further in this review. Various strategies of tissue bioengineering can affect the regeneration of dentin-pulp complex, periodontium regeneration, and whole teeth bioengineering. In this regard, in vivo/ex vivo experimental models have been developed recently in order to perform preclinical studies of dental tissue engineering which make it more transferable to be used for clinic uses. This review summarizes dental tissue engineering through its different components. Also, strategies of tissue bioengineering and experimental models are introduced in order to provide a perspective of the potential roles of dental tissue engineering to be used for clinical aims.

Fabrication of Low-Molecular-Weight Hyaluronic Acid-Carboxymethyl Cellulose Hybrid to Promote Bone Growth in Guided Bone Regeneration Surgery: An Animal Study

Guided bone regeneration surgery is an important dental operation used to regenerate enough bone to successfully heal dental implants. When this technique is performed on maxilla sinuses, hyaluronic acid (HLA) can be used as an auxiliary material to improve the graft material handling properties. Recent studies have indicated that low-molecular hyaluronic acid (L-HLA) provides a better regeneration ability than high-molecular-weight (H-HLA) analogues. The aim of this study was to fabricate an L-HLA-carboxymethyl cellulose (CMC) hybrid to promote bone regeneration while maintaining viscosity. The proliferation effect of fabricated L-HLA was tested using dental pulp stem cells (DPSCs). The mitogen-activated protein kinase (MAPK) pathway was examined using cells cultured with L-HLA combined with extracellular-signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38 inhibitors. The bone growth promotion of fabricated L-HLA/CMC hybrids was tested using an animal model. Micro-computer tomography (Micro-CT) and histological images were evaluated quantitatively to compare the differences in the osteogenesis between the H-HLA and L-HLA. Our results show that the fabricated L-HLA can bind to CD44 on the DPSC cell membranes and affect MAPK pathways, resulting in a prompt proliferation rate increase. Micro CT images show that new bone formation in rabbit calvaria defects treated with L-HLA/CMC was almost two times higher than in defects filled with H-HLA/CMC (p < 0.05) at 4 weeks, a trend that remained at 8 weeks and was confirmed by HE-stained images. According to these findings, it is reasonable to conclude that L-HLA provides better bone healing than H-HLA, and that the L-HLA/CMC fabricated in this study is a potential candidate for improving bone healing efficiency when a guided bone regeneration surgery was performed.

Cells and material-based strategies for regenerative endodontics

The carious process leads to inflammation of pulp tissue. Current care options include root canal treatment or apexification. These procedures, however, result in the loss of tooth vitality, sensitivity, and healing. Pulp capping and dental pulp regeneration are continually evolving techniques to regenerate pulp tissue, avoiding necrosis and loss of vitality. Many studies have successfully employed stem/progenitor cell populations, revascularization approaches, scaffolds or material-based strategies for pulp regeneration. Here we outline advantages and disadvantages of different methods and techniques which are currently being used in the field of regenerative endodontics. We also summarize recent findings on efficacious peptide-based materials which target the dental niche.

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Advanced platelet-rich fibrin (A-PRF) has an impact on the initial healing of gingival regeneration after tooth extraction

OBJECTIVES

Platelet-rich fibrin (PRF) is widely used in wound healing because it contains several growth factors, including vascular endothelial growth factor (VEGF). In this study, we investigated the effects of advanced PRF (A-PRF) in early-stage gingival regeneration after tooth extraction.

METHODS

Blood sample was collected from females beagle dogs (age: 12 months) before tooth extraction for A-PRF preparation. All animals were sacrificed by perfusion-fixation on postoperative days 1, 3, and 7. The upper jaws were prepared for hematoxylin and eosin staining and immunostaining (for CD34 and VEGF). The lower jaw samples were prepared for scanning electron microscope observations. Blood flow in the gingiva before and after surgery was measured using laser Doppler flowmetry.

RESULTS

In the A-PRF group, a large number of microvessels were observed in the gingival tissue on postoperative day 1. The microvessels in the control group were fewer and sparse. Regarding the vascular resin cast, a large number of new blood vessels were observed on postoperative day 1 in the A-PRF group. A stronger CD34-positive signal was obtained around the blood vessels in the A-PRF group than in the control group. Further, a strong VEGF-positive signal was observed in the perivascular tissue in the A-PRF group. Gingival blood flow was significantly higher in the A-PRF group after surgery.

CONCLUSION

A-PRF had a positive impact on angiogenesis in the gingiva through the induction of VEGF expression. Thus, A-PRF may be beneficial for gingival tissue regeneration.

Regenerative benefits of using growth factors in treatment of periodontal defects: A systematic review and meta-analysis with Trial Sequential Analysis on preclinical studies

The ultimate goal in periodontal treatments is to achieve a functional and anatomical regeneration of the lost tissues. Numerous studies have in some way illustrated the beneficial effects of biologic modifiers in this process, yet they are subject to a rather large degree of diversity in their results. Thanks to the promising outcomes of bioengineering techniques in the field of periodontal regeneration, this systematic review aims to evaluate the effect of various biologic modifiers used in periodontal defects of animal models. Electronic databases (Medline, Scopus, Embase, Web of Science, and Google Scholar) were searched (March 2010-December 2020) for every study that used biomolecules for regeneration of periodontal osseous defects in animal models. Regenerated bone height or area, new cementum, new connective tissues, new regenerated periodontal ligament and the dimensions of epithelial attachment (either in mm/mm² or percentage) were the investigated outcomes. The risk of bias of the included studies was assessed using the SYRCLE tool. In closing, there was a meta-analysis carried out on the outcomes of interest. Trial Sequential Analysis was also carried out to figure out the power of meta-analytic outcomes. From 1995 studies which were found in the initial search, 34 studies were included in this review, and 20 of them were selected for the meta-analysis. The eligible studies were categorized according to the morphology of the experimental periodontal defects as one-, two-, and three-wall intrabony defects; furcation defects, and recession-type defects. The most studied biomolecules were rhFGF-2, rhGDF-5, platelet-derived growth factor, bone morphogenetic protein-2, and enamel matrix derivative (EMD). Based on the meta-analysis findings, combined application of biomolecules with regenerative treatments could improve new bone and cementum formation near 1 mm when compared to the control groups in one, two and three-wall intrabony defect models (p < 0.001). In furcation grade II defect, the addition of biomolecules was observed to enhance bone area gain and cementum height regeneration up to almost 2 mm (p < 0.001). Trial Sequential Analysis results confirmed the significant effect in the aforementioned meta-analyses. In cases of the buccal recession model, the application of rhFGF-2 and rhGDF-5 decreased the dimension of epithelial attachments besides regenerative advantages on bone and cementum formation, but EMD deposition exerted no inhibitory effect on epithelial down-growth. Application of biologic modifiers especially FGF-2 and GDF-5, could positively improve the regeneration of periodontal tissues, particularly cementum and bone in animal models. Trial Sequential Analysis confirmed the results but the power of the evidences was high just in some subgroup meta-analyses, like bone and cementum regeneration in furcation grade II model and cementum regeneration in one-wall intrabony defects. The outcomes of this study can potentially endow clinicians with guidelines for the appropriate application of growth factors in periodontal regenerative therapies.

Application of deproteinized bovine bone mineral as proangiogenic scaffold for alveolar bone formation in beagle dogs

Alveolar bone repair after tooth extraction is essential after oral surgeries. Various grafting materials are used to promote the regeneration of lost alveolar bone. This study analysed the morphological features of the tissue regeneration process using deproteinized bovine bone mineral (DBBM). DBBM was used to densely fill the extraction sockets in beagle dogs. Following resin casting of the vasculature, stereomicroscopy and scanning electron microscopy were used to observe blood vessels and hard tissues in haematoxylin and eosin-stained sections on postoperative days 14, 30 and 90 in conjunction with vascular endothelial growth factor (VEGF) immunostaining to evaluate alveolar bone vascularization. On day 14 post-operation, the DBBM granules tightly filled the extraction sockets, maintained alveolar margin height and formed a scaffold for aiding angiogenesis and new bone formation. On day 30, new bone formation was observed around the DBBM granules. By day 90, bone tissue regeneration progressed in both groups but was more pronounced in the DBBM group. Alveolar margin height was maintained in the DBBM group throughout the study. Furthermore, VEGF expression in the DBBM group was detected around newly formed bone. We conclude that DBBM acts as a suitable scaffold for new bone generation, as well as angiogenesis around healing alveolar bone, and that it has the potential to play a key role in vascularization and bone formation.

The Emerging Role of Stem Cells in Regenerative Dentistry

Progress of modern dentistry is accelerating at a spectacular speed in the scientific, technological and clinical areas. Practical examples are the advancement in the digital field, which has guaranteed an average level of prosthetic practices for all patients, as well as other scientific developments, including research on stem cell biology. Given their plasticity, defined as the ability to differentiate into specific cell lineages with a capacity of almost unlimited self-renewal and release of trophic/immunomodulatory factors, stem cells have gained significant scientific and commercial interest in the last 15 years. Stem cells that can be isolated from various tissues of the oral cavity have emerged as attractive sources for bone and dental regeneration, mainly due to their ease of accessibility. This review will present the current understanding of emerging conceptual and technological issues of the use of stem cells to treat bone and dental loss defects. In particular, we will focus on the clinical application of stem cells, either directly isolated from oral sources or in vitro reprogrammed from somatic cells (induced pluripotent stem cells). Research aimed at further unraveling stem cell plasticity will allow to identify optimal stem cell sources and characteristics, to develop novel regenerative tools in dentistry.

Functional roles of fish collagen peptides on bone regeneration

Fish collagen peptides (FCP) derived from the skin, bones and scales are commercially used as a functional food or dietary supplement for hypertension and diabetes. However, there is limited evidence on the effects of FCP on the osteoblast function in contrast to evidence of the effects on wound healing, diabetes and bone regeneration, which have been obtained from animal studies. In this narrative review, we expound on the availability of FCP by basic research using osteoblasts. Low-concentration FCP upregulates the expression of osteoblast proliferation, differentiation and collagen modifying enzyme-related genes. Furthermore, it could accelerate matrix mineralization. FCP may have potential utility as a biomaterial to improve collagen quality and promote mineralization through the mitogen-activated protein kinase and Smad cascades. However, there are few clinical studies on bone regeneration in human subjects. It is desirable to be applied clinically through clinical study as soon as possible, based on the results from basic research.

Effects of various thicknesses and levels of mineral trioxide aggregate coronal plugs on nanoleakage and fracture resistance in revascularization: An in vitro study

The aim of this study was to evaluate the effects of mineral trioxide aggregate (MTA) applied at varying levels and thickness in the cervical region of the root on the leakage and fracture resistance of the simulated immature teeth. 3 study groups (n = 16) (Group 1: 2 mm MTA, Group 2: 4 mm MTA, Group 3: 2 mm MTA+2 mm RMGIC below cementoenamel junction) and 2 control groups (Group 4: Complete canal obturation, Group 5: No coronal plug) were used for the study. Nanoleakage was measured using a micro-computed tomography system. For the fracture resistance test, a universal testing machine was used. The amount of silver nitrate penetration decreased while MTA thicknesses increased (P < 0.001). However, the placement of MTA as a thicker layer did not make any additional contribution on the fracture resistance (P > 0.05). The 4-mm coronal MTA plug can be suggested in RETs for its superior sealing and reinforcement abilities.

Current status and future of delivery systems for prevention and treatment of infections in the oral cavity

Oral health reflects the general health, and it is fundamental to well-being and quality of life. An infection in the oral cavity can be associated with serious complications in human health. Local therapy of these infections offers many advantages over systemic drug administration, targeting directly to the diseased area while minimizing systemic side effects. Specialized drug delivery systems into the oral cavity have to be designed in such a fashion that they resist to the aqueous environment that is constantly bathed in saliva and subject to mechanical forces. Additionally, a prolonged release of drug should also be provided, which would enhance the efficacy and also decrease the repeated dosing. This review is aimed to summarize the current most relevant findings related to local drug delivery of various drug groups for prevention and treatment of infections (viral, bacterial, fungal) and infection-related manifestations in the oral cavity. Current therapeutic challenges in regard to effective local drug delivery systems will be discussed, and the recent approaches to overcome these obstacles will be reviewed. Finally, future prospects will be overviewed to promote novel strategies that can be implemented in clinical management for prevention and treatment of oral infections.

Effects of Root Maturation and Thickness Variation in Coronal Mineral Trioxide Aggregate Plugs Under Traumatic Load on Stress Distribution in Regenerative Endodontic Procedures: A 3-dimensional Finite Element Analysis Study

INTRODUCTION

Regenerative endodontic procedures (REPs) are the best biological-based treatment choice for managing necrotic immature permanent teeth. This study aimed to evaluate the stress distribution of immature maxillary permanent incisors and periodontal tissues under a traumatic load after root maturation achieved by REP with thickness variation in coronal mineral trioxide aggregate (MTA) plugs.

METHODS

Five different mathematical 3-dimensional finite element analysis models of an immature permanent maxillary incisor were created. These involved immediate postoperative models after REP with varying coronal MTA plug thickness (model 1: 3-mm MTA and model 2: 5-mm MTA), postoperative models after REP with varying coronal MTA plug thickness with 15% volumetric root maturation (model 3: 3-mm MTA and model 4: 5-mm MTA), and a control model (model 5: a mature, healthy maxillary incisor). After the modeling procedures, a traumatic horizontal force load of 400 N was applied, and 3-dimensional finite element analysis was performed. The minimum principal, maximum principal, and von Mises stress criteria were calculated for evaluation.

RESULTS

Regardless of the coronal MTA plug thickness, tensile stress in cervical root surfaces decreased with root maturation after REP. Using the 5-mm MTA plug reduced all types of stress in the middle third of the root. In bone tissue, the difference in MTA thickness did not affect stress values. However, stress decreased in most of the bony surfaces with root maturation after REP.

CONCLUSIONS

Using the 5-mm coronal MTA plug may help in providing biomechanical advantages regarding stress transmission. Also, because root maturation after REP provided a more favorable stress distribution as mentioned, regenerative treatments can be recommended for immature permanent maxillary incisors for a good prognosis.

Interventions to reduce bruxism in children and adolescents: a systematic scoping review and critical reflection

The aim of the present study was to perform a critical reflection about intervention options for bruxism reduction in children and adolescents. Search was conducted based on the PICO-structured question: "What are the intervention options to reduce bruxism in children/adolescents?". No language, year, or study design restrictions were imposed. Studies reporting interventions to reduce bruxism in children (< 10) and adolescents (10 to 19 years old) were included. Reviews and letters to editors were not included. From 2723 records, 17 papers were included. Included studies were primarily randomized clinical trials performed in Brazil (35.3%) and using different criteria for the diagnosis of bruxism. Reduction in self-reported bruxism and headaches associated with bruxism were observed in studies that used medications (hydroxyzine/trazodone/flurazepam), occlusal splints, orthodontic interventions, and psychological and physical therapy interventions. Reduction in Rhythmic Masticatory Muscle Activity was observed with the use of the occlusal splint and in orthodontic interventions. Alternative treatments (medicinal extracts such as Melissa officinalis-L) have shown inconclusive results.Conclusions: Several intervention options are available to inhibit or reduce bruxism activity. The respective indication, contraindications, and side effects of each treatment option must be assessed individually and carefully, taking into account that bruxism is not considered a disorder in otherwise healthy individuals.What is known• Biological and psychological factors have been strongly correlated to the development of bruxism• Bruxism prevalence ranging from 6 to 50% in childrenWhat is new• Reduction in self-reported bruxism and headaches associated with bruxism were observed in studies that used medication (Hydroxyzine/ Trazodone/ Flurazepam), occlusal splints, orthodontic interventions, psychological, and physical therapy interventions• A reduction in Rhythmic Masticatory Muscle Activity was observed with the use of the occlusal splint and orthodontic interventions. Alternative treatments (medicinal extracts such as Melissa officinalis L) show inconclusive results in respect of the reduction in bruxism.