New insights into bioactivity of ceria-stabilized zirconia: Direct bonding to bone-like hydroxyapatite at nanoscale

Oral biosciences: The annual review 2024

BACKGROUND

The Journal of Oral Biosciences is committed to advancing and disseminating fundamental knowledge across all areas of oral biosciences. This editorial review features review articles covering diverse topics, including the "mandible," "tooth remineralization," "dental pulpitis," "dental implants," "mesenchymal stem cells," "microbiota," "facial pain," "stomatitis," "odontogenic tumors," "oral submucous fibrosis," "insights on orofacial pain," "tissue engineering," "melatonin," and "regenerative medicine."

HIGHLIGHT

This editorial review focuses on forensic anthropology, calcium sucrose phosphate, pulp biomarkers, zirconia, mesenchymal stem cells, microflora, stomatitis, ameloblastoma, areca nut, orofacial pain, collagen, melatonin, and tooth regeneration.

CONCLUSION

The review articles featured in the Journal of Oral Biosciences have significantly contributed to expanding readers' knowledge across various domains of oral biosciences. The current editorial review discusses the key findings and significance of these review articles.

Enhancement of differentiation and mineralization of human dental pulp stem cells via TGF-β signaling in low-level laser therapy using Er:YAG lasers

OBJECTIVES

Low-level laser therapy (LLLT) using an erbium-doped yttrium aluminum garnet (Er:YAG) laser provides a non-invasive approach applicable to various dental treatments. Here, we investigated the effects of Er:YAG laser irradiation on human dental pulp stem cells (hDPSCs) in an in vitro experiment.

METHODS

The hDPSCs were categorized into four groups: laser-irradiated with activators (VLT: activated vitamin D3, bone morphogenetic protein receptor inhibitor, and transforming growth factor-beta (TGF-β)) (LLLT(+)VLT), laser-irradiated without activators (LLLT(+)-only), non-irradiated with activators (LLLT(-)VLT), and non-irradiated without activators (control). Cell proliferation, hard tissue differentiation, TGF-β signaling pathway activity, mineralization induction, and gene expression levels were assessed using several approaches, including cell proliferation assays, ALP assays, western blotting, Alizarin Red S staining, X-ray diffraction, and quantitative polymerase chain reaction.

RESULTS

Cell proliferation was similar between the LLLT(+)-only and control groups. The ALP activity was significantly higher in LLLT(+)VLT group than in LLLT(-)VLT group (p < 0.05); however, it was suppressed by TGF-β signaling inhibitors. Western blotting showed enhanced SMAD3 phosphorylation in the LLLT(+)VLT group. The mineralization nodules and mRNA levels of matrix vesicle marker genes were significantly higher in LLLT(+)VLT group, and the nodules were partially composed of hydroxyapatite. The hard tissue formation marker gene expression in LLLT(+)VLT group was significantly higher (p < 0.05) than that in the LLLT(+)-only and control groups; however, it was unchanged or suppressed compared with that in LLLT(-)VLT group.

CONCLUSIONS

LLLT using an Er:YAG laser, combined with VLT, may promote the differentiation of hDPSCs into hard tissue-forming cells and enhance mineralization.

Nanoscale osseointegration of zirconia evaluated from the interfacial structure between ceria-stabilized tetragonal zirconia and cell-induced hydroxyapatite

BACKGROUND

The osseointegration of zirconia implants has been evaluated based on their implant fixture bonding with the alveolar bone at the optical microscopic level. Achieving nano-level bonding between zirconia and bone apatite is crucial for superior osseointegration; however, only a few studies have investigated nanoscale bonding. This review outlines zirconia osseointegration, including surface modification, and presents an evaluation of nanoscale zirconia-apatite bonding and its structure.

HIGHLIGHT

Assuming osseointegration, the cells produced calcium salts on a ceria-stabilized zirconia substrate. We analyzed the interface between calcium salts and zirconia substrates using transmission electron microscopy and found that 1) the cell-induced calcium salts were bone-like apatite and 2) direct nanoscale bonding was observed between the bone-like apatite and zirconia crystals without any special modifications of the zirconia surface.

CONCLUSION

Structural affinity exists between bone apatite and zirconia crystals. Apatite formation can be induced by the zirconia surface. Zirconia bonds directly with apatite, indicating superior osseointegration in vivo.

Synergistic effect of FGF-2 and TGF-β1 on the mineralization of human umbilical cord perivascular cells

OBJECTIVE

Human umbilical cord perivascular cells (HUCPVCs) are derived from the human umbilical cord perivascular tissue and are expected to replace mesenchymal stromal cells in the future. We investigated the synergistic effects of fibroblast growth factor 2 (FGF-2) and transforming growth factor-beta 1 (TGF-β1) on HUCPVC mineralization.

DESIGN

We prepared HUCPVCs with (FGF(+)HUCPVCs) or without FGF-2 (FGF(-)HUCPVCs) in the presence of activated vitamin D3, a bone morphogenic protein inhibitor, and TGF-β1. We examined the cell proliferative capacity, expression of various hard tissue-forming cell gene markers, and mineralization induction ability and identified the crystalline phases of the mineralized nodules.

RESULTS

FGF(+)HUCPVCs exhibited higher intracellular alkaline phosphatase (ALP) gene expression and ALP activity, and their cell proliferation rate was higher than that of FGF(-)HUCPVCs. The expression levels of osteoblast marker genes increased in FGF(+)HUCPVCs, whereas those of elastic fiber and muscle cell markers increased in FGF(-)HUCPVCs. The expression of genes related to matrix vesicle-mediated mineralization was increased in FGF(+)HUCPVCs. While FGF(-)HUCPVCs displayed myofibroblast-like properties and could not induce mineralization, FGF(+)HUCPVCs demonstrated the ability to produce mineralized nodules. The resulting mineralized nodules consisted of hydroxyapatite as the major phase and minor amounts of octacalcium phosphate. The mineralized nodules exhibited the morphological characteristics of bone hydroxyapatite, composed of fibrous hydroxyapatite nanorods and polycrystalline sheets.

CONCLUSION

We found that FGF-2 synergizes with TGF-β1 and is a key factor in the differentiation of HUCPVCs into osteoblast-like cells. Thus, HUCPVCs can potentially serve as a new stem cell source for future bone regeneration and dental treatments.

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.

Nanostructured Ceria: Biomolecular Templates and (Bio)applications

Ceria (CeO2) nanostructures are well-known in catalysis for energy and environmental preservation and remediation. Recently, they have also been gaining momentum for biological applications in virtue of their unique redox properties that make them antioxidant or pro-oxidant, depending on the experimental conditions and ceria nanomorphology. In particular, interest has grown in the use of biotemplates to exert control over ceria morphology and reactivity. However, only a handful of reports exist on the use of specific biomolecules to template ceria nucleation and growth into defined nanostructures. This review focusses on the latest advancements in the area of biomolecular templates for ceria nanostructures and existing opportunities for their (bio)applications.