Cementum regeneration using stem cells in the dog model: A systematic review

Cementum is key to periodontal tissue regeneration: A review on apatite microstructures for creation of novel cementum-based dental implants

The cementum is the outermost layer of hard tissue covering the dentin within the root portion of the teeth. It is the only hard tissue with a specialized structure and function that forms a part of both the teeth and periodontal tissue. As such, cementum is believed to be critical for periodontal tissue regeneration. In this review, we discuss the function and histological structure of the cementum to promote crystal engineering with a biochemical approach in cementum regenerative medicine. We review the microstructure of enamel and bone while discussing the mechanism underlying apatite crystal formation to infer the morphology of cementum apatite crystals and their complex structure with collagen fibers. Finally, the limitations of the current dental implant treatments in clinical practice are explored from the perspective of periodontal tissue regeneration. We anticipate the possibility of advancing periodontal tissue regenerative medicine via cementum regeneration using a combination of material science and biochemical methods.

Human Umbilical Cord Mesenchymal Stem Cells: Current Literature and Role in Periodontal Regeneration

Periodontal disease can cause irreversible damage to tooth-supporting tissues such as the root cementum, periodontal ligament, and alveolar bone, eventually leading to tooth loss. While standard periodontal treatments are usually helpful in reducing disease progression, they cannot repair or replace lost periodontal tissue. Periodontal regeneration has been demonstrated to be beneficial in treating intraosseous and furcation defects to varied degrees. Cell-based treatment for periodontal regeneration will become more efficient and predictable as tissue engineering and progenitor cell biology advance, surpassing the limitations of present therapeutic techniques. Stem cells are undifferentiated cells with the ability to self-renew and differentiate into several cell types when stimulated. Mesenchymal stem cells (MSCs) have been tested for periodontal regeneration in vitro and in humans, with promising results. Human umbilical cord mesenchymal stem cells (UC-MSCs) possess a great regenerative and therapeutic potential. Their added benefits comprise ease of collection, endless source of stem cells, less immunorejection, and affordability. Further, their collection does not include the concerns associated with human embryonic stem cells. The purpose of this review is to address the most recent findings about periodontal regenerative mechanisms, different stem cells accessible for periodontal regeneration, and UC-MSCs and their involvement in periodontal regeneration.

Stem Cell Transplantation and Cell-Free Treatment for Periodontal Regeneration

Increasing attention has been paid to cell-based medicines. Many in vivo and in vitro studies have demonstrated the efficacy of stem cell transplantation for the regeneration of periodontal tissues over the past 20 years. Although positive evidence has accumulated regarding periodontal regeneration using stem cells, the exact mechanism of tissue regeneration is still largely unknown. This review outlines the practicality and emerging problems of stem cell transplantation therapy for periodontal regeneration. In addition, possible solutions to these problems and cell-free treatment are discussed.

Stem cell therapies for periodontal tissue regeneration: a network meta-analysis of preclinical studies

Background

Periodontal tissue regeneration (PTR) is the ultimate goal of periodontal therapy. Currently, stem cell therapy is considered a promising strategy for achieving PTR. However, there is still no conclusive comparison that distinguishes clear hierarchies among different kinds of stem cells.

Methods

A systematic review and network meta-analysis (NMA) was performed using MEDLINE (via PubMed), EMBASE, and Web of Science up to February 2020. Preclinical studies assessing five types of stem cells for PTR were included; the five types of stem cells included periodontal ligament-derived stem cells (PDLSCs), bone marrow-derived stem cells (BMSCs), adipose tissue-derived stem cells (ADSCs), dental pulp-derived stem cells (DPSCs), and gingival-derived stem cells (GMSCs). The primary outcomes were three histological indicators with continuous variables: newly formed alveolar bone (NB), newly formed cementum (NC), and newly formed periodontal ligament (NPDL). We performed pairwise meta-analyses using a random-effects model and then performed a random-effects NMA using a multivariate meta-analysis model.

Results

Sixty preclinical studies assessing five different stem cell-based therapies were identified. The NMA showed that in terms of NB, PDLSCs (standardized mean difference 1.87, 95% credible interval 1.24 to 2.51), BMSCs (1.88, 1.17 to 2.59), and DPSCs (1.69, 0.64 to 2.75) were statistically more efficacious than cell carriers (CCs). In addition, PDLSCs were superior to GMSCs (1.49, 0.04 to 2.94). For NC, PDLSCs (2.18, 1.48 to 2.87), BMSCs (2.11, 1.28 to 2.94), and ADSCs (1.55, 0.18 to 2.91) were superior to CCs. For NPDL, PDLSCs (1.69, 0.92 to 2.47) and BMSCs (1.41, 0.56 to 2.26) were more efficacious than CCs, and PDLSCs (1.26, 0.11 to 2.42) were superior to GMSCs. The results of treatment hierarchies also demonstrated that the two highest-ranked interventions were PDLSCs and BMSCs.

Conclusion

PDLSCs and BMSCs were the most effective and well-documented stem cells for PTR among the five kinds of stem cells evaluated in this study, and there was no statistical significance between them. To translate the stem cell therapies for PTR successfully in the clinic, future studies should utilize robust experimental designs and reports.

External apical root resorption and vectors of orthodontic tooth movement

INTRODUCTION

External apical root resorption is nearly ubiquitous in people treated orthodontically. This study predicted the extent of external apical root resorption by the vector of the incisor movement.

METHODS

Cone-beam computed tomography scans of 93 white American adolescents (45 boys, 48 girls) with a Class I malocclusion who received comprehensive orthodontics were analyzed. Half were treated with 4 first-premolar extractions, and the others were treated without extractions. An x, y, z coordinate system was registered on the maxillae, superimposing on foramina, to quantify vectors of maxillary incisor movements. Multiple linear regression identified significant predictors of resorption for each incisor.

RESULTS

Strongly predictive models (R² = 77%-86%) were obtained. All directions of incisor movement tested (anteroposterior, mediolateral, craniocaudal, torquing) increased the risk of resorption in a dose-response fashion. Intrusion was most damaging. The patient's sex, age, and duration of treatment were not predictive.

CONCLUSIONS

Root resorption is a very frequent consequence of tooth movement, especially intrusion and torquing, though no direction is harmless, and most corrections occur in combination. Incisor apical resorption was significantly greater in the extraction sample (ca 0.5 mm).

Natural protein bioinspired materials for regeneration of hard tissues

This review describes the protein bioinspired materials for the repair of hard tissues such as enamel, dentin and bone.

Periodontal Bone-Ligament-Cementum Regeneration via Scaffolds and Stem Cells

Periodontitis is a prevalent infectious disease worldwide, causing the damage of periodontal support tissues, which can eventually lead to tooth loss. The goal of periodontal treatment is to control the infections and reconstruct the structure and function of periodontal tissues including cementum, periodontal ligament (PDL) fibers, and bone. The regeneration of these three types of tissues, including the re-formation of the oriented PDL fibers to be attached firmly to the new cementum and alveolar bone, remains a major challenge. This article represents the first systematic review on the cutting-edge researches on the regeneration of all three types of periodontal tissues and the simultaneous regeneration of the entire bone-PDL-cementum complex, via stem cells, bio-printing, gene therapy, and layered bio-mimetic technologies. This article primarily includes bone regeneration; PDL regeneration; cementum regeneration; endogenous cell-homing and host-mobilized stem cells; 3D bio-printing and generation of the oriented PDL fibers; gene therapy-based approaches for periodontal regeneration; regenerating the bone-PDL-cementum complex via layered materials and cells. These novel developments in stem cell technology and bioactive and bio-mimetic scaffolds are highly promising to substantially enhance the periodontal regeneration including both hard and soft tissues, with applicability to other therapies in the oral and maxillofacial region.