Chemical Properties of Human Dentin Blocks and Vertical Augmentation by Ultrasonically Demineralized Dentin Matrix Blocks on Scratched Skull without Periosteum of Adult-Aged Rats

Vertical augmentation is one of the most challenging techniques in bone engineering. Several parameters, such mechano-chemical characteristics, are important to optimize vertical bone regeneration using biomaterials. The aims of this study were to chemically characterize human dentin blocks (calcified demineralized dentin matrix: CDM, partially demineralized dentin matrix: PDDM and completely demineralized dentin matrix: CDDM) (2 × 2 × 1 mm3) chemically and evaluate the behavior of PDDM blocks on non-scratched or scratched skulls without periosteum of adult rats (10–12 months old, female) as a vertical augmentation model. The dissolved efficiency of CDM showed 32.3% after ultrasonic demineralization in 1.0 L of 2% HNO3 for 30 min. The 30 min-demineralized dentin was named PDDM. The SEM images of PDDM showed the opening of dentinal tubes, nano-microcracks and the smooth surface. In the collagenase digestion test, the weight-decreasing rates of CDM, PDDM and CDDM were 9.2%, 25.5% and 78.3% at 12 weeks, respectively. CDM inhibited the collagenase digestion, compared with PDDM and CDDM. In the PDDM onlay graft on an ultrasonically scratched skull, the bone marrow-space opening from original bone was found in the bony bridge formation between the human PDDM block and dense skull of adult senior rats at 4 and 8 weeks. On the other hand, in the cases of the marrow-space closing in both non-scratched skulls and scratched skulls, the bony bridge was not formed. The results indicated that the ultrasonic scratching into the compact parietal bone might contribute greatly to the marrow-space opening from skull and the supply of marrow cells, and then bony bridge formation could occur in the vertical augmentation model without a periosteum.

Bone regeneration of demineralized dentin matrix with platelet-rich fibrin and recombinant human bone morphogenetic protein-2 on the bone defects in rabbit calvaria

Background This study was to evaluate the bone formation ability of demineralized dentin matrix (DDM) combined with platelet-rich fibrinogen (PRF) and DDM combined with recombinant human bone morphogenetic protein-2 (rhBMP-2) to improve the osteoinductive ability of DDM. Methods After four bone defects with a diameter of 8mm were created in the calvarium of each rabbit, DDM was grafted into the first defect (experimental groups 1), a combination of DDM and PRF was grafted into the second defect (experimental groups 2), and DDM with absorbed rhBMP-2 was grafted into the third defect (experimental groups 3). The fourth defect was used as the control group. Twelve healthy male rabbits (New Zealand, white rabbits) weighing around 3.0–4.0 kg were used. Among 12 rabbits, 3 rabbits were sacrificed immediately after surgery and at 2, 4, and 8 weeks after surgery, respectively. Histopathologic analysis and histomorphometric analysis were conducted to evaluate bone formation in each group. Results The PRF/DDM group did not show a significantly higher degree of new bone formation in calvarial bone defects than the DDM group at 2, 4, and 8 weeks postoperatively in histopathological findings and histomorphometric results. On the other side, the rhBMP-2/DDM group showed higher degrees of new bone formation and calcification, and the lamellae of bone matrix, which are observed in mature bone tissue, were more distinctly visible in the rhBMP-2/DDM group. Moreover, the rhBMP-2/DDM group showed a significantly higher amount of new bone formation, compared to the DDM group at 4 and 8 weeks postoperatively (P<0.05) in histomorphometric results. Conclusion The DDM has great potential as a carrier for the maintenance and sustained release of rhBMP-2, which has been recently receiving wide attention as a type of signaling molecules to promote bone formation.

Dentin-Derived-Barrier Membrane in Guided Bone Regeneration: A Case Report

An autogenous, demineralized, dentin matrix is a well-known osteo-inductive bone substitute that is mostly composed of type I collagen and is widely used in implant dentistry. This single case report describes a successful outcome in guided bone regeneration and dental implantation with a novel human-derived collagen membrane. The authors fabricated a dentin-derived-barrier membrane from a block-type autogenous demineralized dentin matrix to overcome the mechanical instability of the collagen membrane. The dentin-derived-barrier acted as an osteo-inductive collagen membrane with mechanical and clot stabilities, and it replaced the osteo-genetic function of the periosteum. Further research involving large numbers of patients should be conducted to evaluate bone forming capacity in comparison with other collagen membranes.

Demineralized Dentin Matrix Particle-Based Bio-Ink for Patient-Specific Shaped 3D Dental Tissue Regeneration

Demineralized dentin matrix (DDM)-based materials have been actively developed and are well-known for their excellent performance in dental tissue regeneration. However, DDM-based bio-ink suitable for fabrication of engineered dental tissues that are patient-specific in terms of shape and size, has not yet been developed. In this study, we developed a DDM particle-based bio-ink (DDMp bio-ink) with enhanced three-dimensional (3D) printability. The bio-ink was prepared by mixing DDM particles and a fibrinogen–gelatin mixture homogeneously. The effects of DDMp concentration on the 3D printability of the bio-ink and dental cell compatibility were investigated. As the DDMp concentration increased, the viscosity and shear thinning behavior of the bio-ink improved gradually, which led to the improvement of the ink’s 3D printability. The higher the DDMp content, the better were the printing resolution and stacking ability of the 3D printing. The printable minimum line width of 10% w/v DDMp bio-ink was approximately 252 μm, whereas the fibrinogen–gelatin mixture was approximately 363 μm. The ink’s cytocompatibility test with dental pulp stem cells (DPSCs) exhibited greater than 95% cell viability. In addition, as the DDMp concentration increased, odontogenic differentiation of DPSCs was significantly enhanced. Finally, we demonstrated that cellular constructs with 3D patient-specific shapes and clinically relevant sizes could be fabricated through co-printing of polycaprolactone and DPSC-laden DDMp bio-ink.

Reconciling Inherent Interfacial Compatibility Conflict Enhances Adhesive Infiltration and Resolves Dentin Bonding Durability

Wet bonding is a basic technique used daily in clinics for tooth-restoration fixation. However, only 50% of the bonding lasts more than 5 years and thus patients must visit the dentists repeatedly. This is attributed to the limited infiltration of adhesives into the demineralized dentin (DD) matrix during wet-bonding. Herein, we show that reconciling interfacial compatibility conflict between the DD matrix and the critical hydrophobic adhesive molecules via hydrophobizing the DD matrix enables the adhesives to thoroughly infiltrate and uniformly distribute within the DD matrix. Thus, the bonding of the hydrophobic DD matrix using commercial dentin adhesives achieves the bonding strength 2-6 times higher than that of the non-treated DD matrix. When a hydrophobic adhesive is applied on the hydrophobic DD matrix, a flawless hybrid layer is produced as observed by nanoleakage investigation. A long-term bonding strength comes up to 7.3 fold that of the control group and very importantly, with no attenuation after 12 months. This study clarifies the basic cause of poor wet-bonding durability and demonstrates a paradigm in adhesive dentistry to overcome the long-existing bonding durability problem associated with inadequate adhesive infiltration into the DD matrix. This provides a new angle of view to resolve clinical dentin bonding durability problem and will significantly promote adhesive dentistry.HighlightsInherent interfacial compatibility conflict between demineralized dentin matrix and hydrophobic molecules of dentin adhesives is the basic cause for the dentin bonding durability problem.Reconciling the interfacial compatibility conflict markedly facilitates adhesive infiltration in the demineralized dentin matrix and greatly enhances bonding effectiveness.High interfacial compatibility produces a flawless hybrid layer and ideal bonding effectiveness and durability.Graphical AbstractFor wet bonding, poor infiltration of adhesives within the DD matrix inevitably produces numerous defects throughout the hybrid layer, which always leads to the failure of restoration. Via hydrophobizing the DD matrix, reconciling interfacial compatibility conflict between the DD matrix and the hydrophobic adhesive monomers overcomes durability problems associated with the infiltration of adhesives into the DD matrix producing a flawless hybrid layer and providing ideal bonding effectiveness and durability.