Stem Cells, Scaffolds and Gene Therapy for Periodontal Engineering

Exosomes and exosome composite scaffolds in periodontal tissue engineering

Promoting complete periodontal regeneration of damaged periodontal tissues, including dental cementum, periodontal ligament, and alveolar bone, is one of the challenges in the treatment of periodontitis. Therefore, it is urgent to explore new treatment strategies for periodontitis. Exosomes generated from stem cells are now a promising alternative to stem cell therapy, with therapeutic results comparable to those of their blast cells. It has great potential in regulating immune function, inflammation, microbiota, and tissue regeneration and has shown good effects in periodontal tissue regeneration. In addition, periodontal tissue engineering combines exosomes with biomaterial scaffolds to maximize the therapeutic advantages of exosomes. Therefore, this article reviews the progress, challenges, and prospects of exosome and exosome-loaded composite scaffolds in periodontal regeneration.

Variations in Soft and Hard Tissues following Immediate Implant Placement versus Delayed Implant Placement following Socket Preservation in the Maxillary Esthetic Region: A Randomized Controlled Clinical Trial

INTRODUCTION

Although retrospective analysis has shown immediate placement of implants (IIP) in the maxillary esthetic zone showing promising outcomes compared to delayed placement of implants following socket preservation (DIP), a direct comparison in a prospective, well-designed randomized fashion with adequate power analysis between the two implant placement protocols is still lacking. This study is aimed at radiographically evaluating the effect of IIP after extraction as compared to implant placed in preserved sockets 4 months following extraction (DIP) in terms of changes in buccal plate thickness(CBT) after 6 months of healing and evaluation of pink esthetic score (PES) for assessment of soft tissue changes and patient-related outcome measures (PROMs) using visual analogue scale (VAS).

MATERIALS AND METHODS

25 implants were placed immediately following extraction in the IIP group, and 25 implants were placed four months following socket preservation with demineralized bovine bone mineral (DBBM) and advanced platelet-rich fibrin (A-PRF) in the DIP group, control group, in the maxillary esthetic region. CBCT was taken preoperatively and 6 months postoperatively to assess the dimensional changes in the buccal bone plates(CBT). PES and PROMs for pain threshold and patient satisfaction using VAS were evaluated at the time of implant placement and 6 months postoperatively.

RESULTS

Significant differences in mean reduction in buccal plate thickness (CBT) were found in the test group (IIP) 0.2 ± 0.02 compared to the control group (DIP) which showed a mean reduction in CBT of 0.4 ± 0.1 (p < 0.001) at the end of 6 months. Although there was no statistically significant difference in PES between the groups, there was a significant difference between the groups when individual values of PES were compared at p < 0.001.

CONCLUSION

The IIP group showed lesser reduction in CBT and a better PES which is an important clinical information which could be translated clinically in situations where implant placement is planned in the maxillary esthetic region. This trial is registered with CTRI/2019/06/019723.

Advanced platelet-rich fibrin and freeze-dried bone allograft for ridge preservation: A randomized controlled clinical trial

BACKGROUND

Advanced platelet-rich fibrin (A-PRF) is an autogenous blood product with applications in dento-alveolar surgery. However, there is minimal information regarding its optimal clinical application or efficacy. The aim of this multi-arm parallel randomized controlled clinical trial was to evaluate the efficacy of A-PRF alone or with freeze-dried bone allograft (FDBA) in improving vital bone formation and alveolar dimensional stability during ridge preservation.

METHODS

Forty patients requiring extraction of non-molar teeth and replacement with dental implants were randomized into one of four ridge preservation approaches: A-PRF, A-PRF+FDBA, FDBA, or blood clot. A-PRF was prepared at 1,300 rpm for 8 minutes. Non-traumatic extractions and ridge preservation was performed. After an average of 15 weeks healing, bone core samples were harvested at the time of implant placement for micro-CT and histomorphometric analysis. Ridge dimensions were measured immediately after extraction and before implant placement.

RESULTS

Significantly greater loss of ridge height was noted in the blood clot group (3.8 ± 2.0 mm) compared to A-PRF (1.8 ± 2.1 mm) and A-PRF+FDBA (1.0 ± 2.3 mm) groups (P < 0.05). No significant differences in ridge width reduction were noted between groups. Significantly more vital bone was present in the A-PRF group (46% ± 18%) compared to the FDBA group (29% ± 14%) (P < 0.05). Bone mineral density was significantly greater in the FDBA group (551 ± 58 mg/cm³ ) compared to blood clot (487 ± 64 mg/cm³ ) (P < 0.05).

CONCLUSIONS

This study demonstrates A-PRF alone or augmented with FDBA is a suitable biomaterial for ridge preservation. This study represents the first randomized controlled clinical trial comparing A-PRF with and without FDBA to FDBA alone for ridge preservation.

Treatment of Periodontal Bone Defects with Stem Cells from Inflammatory Dental Pulp Tissues in Miniature Swine

Background

Containing a certain proportion of mesenchymal stem cells, inflammatory dental tissue showed great tissue regeneration potential in recent years. However, whether it is applicable to promote tissue regeneration in vivo remains to be elucidated. Therefore, we evaluated the feasibility of stem cells from inflammatory dental pulp tissues (DPSCs-IPs) to reconstruct periodontal defects in miniature pigs.

Methods

The autologous pig DPSCs-IPs were first cultured, appraised and loaded onto β-tricalcium phosphate (β-TCP). The compounds were then engrafted into an artificially-created periodontal defect. Three months later, the extent of periodontal regeneration was evaluated. Clinical examination, radiological examination and immunohistochemical staining were used to assess periodontal regeneration.

Results

The data collectively showed that DPSCs-IPs from miniature pigs expressed moderate to high levels of STRO-1 and CD146 as well as low levels of CD34 and CD45. DPSCs-IPs have osteogentic, adipogenic and chondrogenic differentiation abilities. DPSCs-IPs were engrafted onto β-TCP and regenerated bone to repair periodontal defects by 3 months' post-surgical reconstruction.

Conclusion

Autologous DPSCs-IPs may be a feasible means of periodontal regeneration in miniature pigs.

Bioprinting-Based PDLSC-ECM Screening for in Vivo Repair of Alveolar Bone Defect Using Cell-Laden, Injectable and Photocrosslinkable Hydrogels

Periodontitis is an inflammatory disease worldwide that may result in periodontal defect (especially alveolar bone defect) and even tooth loss. Stem-cell-based approach combined with injectable hydrogels has been proposed as a promising strategy in periodontal treatments. Stem cells fate closely depends on their extracellular matrix (ECM) characteristics. Hence, it is necessary to engineer an appropriate injectable hydrogel to deliver stem cells into the defect while serving as the ECM during healing. Therefore, stem cell-ECM interaction should be studied for better stem cell transplantation. In this study, we developed a bioprinting-based strategy to study stem cell-ECM interaction and thus screen an appropriate ECM for in vivo repair of alveolar bone defect. Periodontal ligament stem cells (PDLSCs) were encapsulated in injectable, photocrosslinkable composite hydrogels composed of gelatin methacrylate (GelMA) and poly(ethylene glycol) dimethacrylate (PEGDA). PDLSC-laden GelMA/PEGDA hydrogels with varying composition were efficiently fabricated via a 3D bioprinting platform by controlling the volume ratio of GelMA-to-PEGDA. PDLSC behavior and fate were found to be closely related to the engineered ECM composition. The 4/1 GelMA/PEGDA composite hydrogel was selected since the best performance in osteogenic differentiation in vitro. Finally, in vivo study indicated a maximal and robust new bone formation in the defects treated with the PDLSC-laden hydrogel with optimized composition as compared to the hydrogel alone and the saline ones. The developed approach would be useful for studying cell-ECM interaction in 3D and paving the way for regeneration of functional tissue.

Biologic Agents for Periodontal Regeneration and Implant Site Development

The advancement of molecular mediators or biologic agents has increased tremendously during the last decade in periodontology and dental implantology. Implant site development and reconstruction of the lost periodontium represent main fields in which these molecular mediators have been employed and investigated. Different growth factors trigger different reactions in the tissues of the periodontium at various cellular levels. Proliferation, migration, and differentiation constitute the main target areas of these molecular mediators. It was the purpose of this comprehensive review to describe the origin and rationale, evidence, and the most current understanding of the following biologic agents: Recombinant Human Platelet-Derived Growth Factor-BB (rhPDGF-BB), Enamel Matrix Derivate (EMD), Platelet-Rich Plasma (PRP) and Platelet-Rich Fibrin (PRF), Recombinant Human Fibroblast Growth Factor-2 (rhFGF-2), Bone Morphogenic Proteins (BMPs, BMP-2 and BMP-7), Teriparatide PTH, and Growth Differential Factor-5 (GDF-5).

Bone Regeneration from PLGA Micro-Nanoparticles

Poly-lactic-co-glycolic acid (PLGA) is one of the most widely used synthetic polymers for development of delivery systems for drugs and therapeutic biomolecules and as component of tissue engineering applications. Its properties and versatility allow it to be a reference polymer in manufacturing of nano- and microparticles to encapsulate and deliver a wide variety of hydrophobic and hydrophilic molecules. It additionally facilitates and extends its use to encapsulate biomolecules such as proteins or nucleic acids that can be released in a controlled way. This review focuses on the use of nano/microparticles of PLGA as a delivery system of one of the most commonly used growth factors in bone tissue engineering, the bone morphogenetic protein 2 (BMP2). Thus, all the needed requirements to reach a controlled delivery of BMP2 using PLGA particles as a main component have been examined. The problems and solutions for the adequate development of this system with a great potential in cell differentiation and proliferation processes under a bone regenerative point of view are discussed.

Clinical Application of Mesenchymal Stem Cells and Novel Supportive Therapies for Oral Bone Regeneration

Bone regeneration is often needed prior to dental implant treatment due to the lack of adequate quantity and quality of the bone after infectious diseases, trauma, tumor, or congenital conditions. In these situations, cell transplantation technologies may help to overcome the limitations of autografts, xenografts, allografts, and alloplastic materials. A database search was conducted to include human clinical trials (randomized or controlled) and case reports/series describing the clinical use of mesenchymal stem cells (MSCs) in the oral cavity for bone regeneration only specifically excluding periodontal regeneration. Additionally, novel advances in related technologies are also described. 190 records were identified. 51 articles were selected for full-text assessment, and only 28 met the inclusion criteria: 9 case series, 10 case reports, and 9 randomized controlled clinical trials. Collectively, they evaluate the use of MSCs in a total of 290 patients in 342 interventions. The current published literature is very diverse in methodology and measurement of outcomes. Moreover, the clinical significance is limited. Therefore, the use of these techniques should be further studied in more challenging clinical scenarios with well-designed and standardized RCTs, potentially in combination with new scaffolding techniques and bioactive molecules to improve the final outcomes.