Comparison of titanium dioxide scaffold with commercial bone graft materials through micro-finite element modelling in flow perfusion

3D finite element analysis of stress distribution on the shape of resected root-end or with/without bone graft of a maxillary premolar during endodontic microsurgery

Background/purpose

Apical root resection pattern affects the stress distribution behavior in the apical region of the resected tooth. The purpose of the study was to compare the biomechanical responses of resected teeth between endodontic microsurgery (horizontal resection) and targeted endodontic microsurgery (round resection).

Materials and methods

Five different models were developed. The basic model without resection (NR) was regarded as the control model, and the others involved: horizontal resection without bone grafting (HN), horizontal resection with bone grafting (HG), round resection without bone grafting (RN), and round resection with bone grafting (RG) models. A static load of 100 N was applied to the buccal and palatal cusps of all the teeth in a 30° oblique direction. The maximum von-Mises stress and tooth displacement values were analyzed and compared.

Results

Both the HN and RN models exhibited lower stress distribution values on bone compared with the NR (control) model. Regarding maximum stress distribution at the root apex, the stress value of the RN model was slightly higher compared to the HN model, whereas the RG model displayed a slightly lower stress value in comparison with the HG model. For maximum tooth displacement value, there were no significant differences between the HN and RN models, as well as the HG and RG models.

Conclusion

The round resection pattern had comparable stress distribution behaviors at the root apex and tooth displacement values with the horizontal resection pattern. Targeted endodontic microsurgery might provide better biomechanical response of the resected tooth after root-end resection.

The response of human osteoblasts on bovine xenografts with and without hyaluronate used in bone augmentation

The aim of the in vitro study was to asses the effect of hyaluronate in conjunction with bovine derived xenografts on the viability, proliferation on day 4, 7 and 10, expression of early osteogenic differentiation marker Alkaline phosphatase on day 14 and 21, collagen, calcium deposition on day 14, 21 and 28 and cellular characteristics, as assessed through live cell image analysis, confocal laser scanning microscopy and scanning electron microscopy, in primary human osteoblasts compared to three bovine xenografts without hyaluronate. All experiments were performed in triplicates. Data were compared between groups and timepoints using one-way analysis of variance (ANOVA). Bonferroni post hoc test were further used for multiple comparison between groups (p < .05) An increase in cell viability (p < .05) and enhanced ALP activity was observed in all xenografts. Specimens containing hyaluronate showed a highest significant difference (23755 ± 29953, p < .0001). The highest levels of calcium (1.60 ± 0.30) and collagen (1.92 ± 0.09, p < .0001) deposition were also observed with hyaluronate loaded groups. The osteoblasts were well attached and spread on all xenograft groups. However, a higher number of cells were observed with hyaluronate functionalized xenograft (76.27 ± 15.11, (p < .0001) in live cell image analysis and they migrated towards the graft boundaries. The biofunctionalization of xenografts with hyaluronate improves their in vitro performance on human osteoblasts. This suggests that hyaluronate might be able to improve the bone regeneration when using such xenografts.

Perfusion in vivo bioreactor promotes regeneration of vascularized tissue-engineered bone

Aim: This study improved the in vivo bioreactor (IVB) for bone regeneration by enhancing stem cell survival and promoting vascularized tissue-engineered bone. Methods: 12 New Zealand rabbits received β-TCP scaffolds with rabbit bone mesenchymal stem cells (BMSCs) implanted. Perfusion IVB with a perfusion electronic pump was compared with the control group using micro-CT, Microfil perfusion, histological staining and RT-PCR for gene expression. Results: Perfusion IVB demonstrated good biocompatibility, increased neoplastic bone tissue, neovascularization and upregulated osteogenic and angiogenesis-related genes in rabbits (p < 0.05). Conclusion: Perfusion IVB holds promise for bone regeneration and tissue engineering in orthopedics and maxillofacial surgery.

Evaluating the cell migration potential of TiO2 nanorods incorporated in a Ti6Al4V scaffold: A multiscale approach

Improvement of cell migration by the nano-topographical modification of implant surface can directly or indirectly accelerate wound healing and osseointegration between bone and implant. Therefore, modification of the implant surface was done with TiO2 nanorod (NR) arrays to develop a more osseointegration-friendly implant in this study. Modulating the migration of a cell, adhered to a scaffold, by the variations of NR diameter, density and tip diameter in vitro is the primary objective of the study. The fluid structure interaction method was used, followed by the submodelling technique in this multiscale analysis. After completing a simulation over a global model, fluid structure interaction data was applied to the sub-scaffold finite element model to predict the mechanical response over cells at the cell-substrate interface. Special focus was given to strain energy density at the cell interface as a response parameter due to its direct correlation with the migration of an adherent cell. The results showed a huge rise in strain energy density after the addition of NRs on the scaffold surface. It also highlighted that variation in NR density plays a more effective role than the variation in NR diameter to control cell migration over a substrate. However, the effect of NR diameter becomes insignificant when the NR tip was considered. The findings of this study could be used to determine the best nanostructure parameters for better osseointegration.

Frontiers of Hydroxyapatite Composites in Bionic Bone Tissue Engineering

Bone defects caused by various factors may cause morphological and functional disorders that can seriously affect patient's quality of life. Autologous bone grafting is morbid, involves numerous complications, and provides limited volume at donor site. Hence, tissue-engineered bone is a better alternative for repair of bone defects and for promoting a patient's functional recovery. Besides good biocompatibility, scaffolding materials represented by hydroxyapatite (HA) composites in tissue-engineered bone also have strong ability to guide bone regeneration. The development of manufacturing technology and advances in material science have made HA composite scaffolding more closely related to the composition and mechanical properties of natural bone. The surface morphology and pore diameter of the scaffold material are more important for cell proliferation, differentiation, and nutrient exchange. The degradation rate of the composite scaffold should match the rate of osteogenesis, and the loading of cells/cytokine is beneficial to promote the formation of new bone. In conclusion, there is no doubt that a breakthrough has been made in composition, mechanical properties, and degradation of HA composites. Biomimetic tissue-engineered bone based on vascularization and innervation show a promising future.

An automated 3D-printed perfusion bioreactor combinable with pulsed electromagnetic field stimulators for bone tissue investigations

In bone tissue engineering research, bioreactors designed for replicating the main features of the complex native environment represent powerful investigation tools. Moreover, when equipped with automation, their use allows reducing user intervention and dependence, increasing reproducibility and the overall quality of the culture process. In this study, an automated uni-/bi-directional perfusion bioreactor combinable with pulsed electromagnetic field (PEMF) stimulation for culturing 3D bone tissue models is proposed. A user-friendly control unit automates the perfusion, minimizing the user dependency. Computational fluid dynamics simulations supported the culture chamber design and allowed the estimation of the shear stress values within the construct. Electromagnetic field simulations demonstrated that, in case of combination with a PEMF stimulator, the construct can be exposed to uniform magnetic fields. Preliminary biological tests on 3D bone tissue models showed that perfusion promotes the release of the early differentiation marker alkaline phosphatase. The histological analysis confirmed that perfusion favors cells to deposit more extracellular matrix (ECM) with respect to the static culture and revealed that bi-directional perfusion better promotes ECM deposition across the construct with respect to uni-directional perfusion. Lastly, the Real-time PCR results of 3D bone tissue models cultured under bi-directional perfusion without and with PEMF stimulation revealed that the only perfusion induced a ~ 40-fold up-regulation of the expression of the osteogenic gene collagen type I with respect to the static control, while a ~ 80-fold up-regulation was measured when perfusion was combined with PEMF stimulation, indicating a positive synergic pro-osteogenic effect of combined physical stimulations.

Osteoblasts in a Perfusion Flow Bioreactor—Tissue Engineered Constructs of TiO2 Scaffolds and Cells for Improved Clinical Performance

Combining biomaterial scaffolds with cells serves as a promising strategy for engineering critical size defects; however, homogenous cellular growth within large scaffolds is challenging. Mechanical stimuli can enhance bone regeneration by modulating cellular growth and differentiation. Here, we compare dynamic seeding in a perfusion flow bioreactor with static seeding for a synthetic bone scaffold for up to 21 days using the cell line MC3T3-E1 and primary human osteoblast, confocal laser scanning microscopy, and real-time reverse transcriptase-polymerase chain reaction. The secretion of bone-related proteins was quantified using multiplex immunoassays. Dynamic culture improved cellular distribution through the TiO₂ scaffold and induced a five-fold increase in cell number after 21 days. The relative mRNA expression of osteopontin of MC3T3-E1 was 40-fold enhanced after 7 and 21 days at a flow rate of 0.08 mL/min, and that of collagen type I alpha I expression was 18-fold after 21 days. A flow rate of 0.16 mL/min was 10-fold less effective. Dynamic culture increased the levels of dickkopf-related protein 1 (60-fold), osteoprotegrin (29-fold), interleukin-6 (23-fold), interleukin-8 (36-fold), monocyte chemoattractant protein 1 (28-fold) and vascular endothelial growth factor (6-fold) in the medium of primary human osteoblasts after 21 days compared to static seeding. The proposed method may have clinical potential for bone tissue engineering.

Internal flow field analysis of heterogeneous porous scaffold for bone tissue engineering

The internal pore structure of the porous scaffold for bone tissue engineering and the pressure and velocity distributions of its flow field affect the attachment, proliferation and differentiation of osteoblasts. The permeability of the porous scaffold determines its ability to transport cellular nutrients and metabolites. Therefore, studying the fluid flow characteristics of the porous scaffold plays a vital role in its biological applications. Heterogeneous porous scaffolds (HPS) with irregular internal pore structure have more bionic characteristics of natural structure than uniform porous scaffolds with regular internal pore structure. In order to comprehensively grasp the biological properties of HPS, this article designed HPS with different porosities based on the Voronoi generation method and random theory, and then used computational fluid dynamics (CFD)software to conduct fluid flow simulations. The velocity and pressure distribution rules of the internal flow field of HPS with different porosities were obtained by CFD simulation analysis, and the relationship between the porosity and the distribution rules was studied. Furthermore, the permeabilities of HPS with different porosities were calculated based on Darcy's law, and the influence rule of porosity on the permeability was obtained.

Sol-Gel-Derived Fibers Based on Amorphous α-Hydroxy-Carboxylate-Modified Titanium(IV) Oxide as a 3-Dimensional Scaffold

The development of novel fibrous biomaterials and further processing of medical devices is still challenging. For instance, titanium(IV) oxide is a well-established biocompatible material, and the synthesis of TiO_x particles and coatings via the sol-gel process has frequently been published. However, synthesis protocols of sol-gel-derived TiO_x fibers are hardly known. In this publication, the authors present a synthesis and fabrication of purely sol-gel-derived TiO_x fiber fleeces starting from the liquid sol-gel precursor titanium ethylate (TEOT). Here, the α-hydroxy-carboxylic acid lactic acid (LA) was used as a chelating ligand to reduce the reactivity towards hydrolysis of TEOT enabling a spinnable sol. The resulting fibers were processed into a non-woven fleece, characterized with FTIR, ¹³C-MAS-NMR, XRD, and screened with regard to their stability in physiological solution. They revealed an unexpected dependency between the LA content and the dissolution behavior. Finally, in vitro cell culture experiments proved their potential suitability as an open-mesh structured scaffold material, even for challenging applications such as therapeutic medicinal products (ATMPs).

Challenges in computational fluid dynamics applications for bone tissue engineering

Bone injuries or defects that require invasive surgical treatment are a serious clinical issue, particularly when it comes to treatment success and effectiveness. Accordingly, bone tissue engineering (BTE) has been researching the use of computational fluid dynamics (CFD) analysis tools to assist in designing optimal scaffolds that better promote bone growth and repair. This paper aims to offer a comprehensive review of recent studies that use CFD analysis in BTE. The mechanical and fluidic properties of a given scaffold are coupled to each other via the scaffold architecture, meaning an optimization of one may negatively affect the other. For example, designs that improve scaffold permeability normally result in a decreased average wall shear stress. Linked with these findings, it appears there are very few studies in this area that state a specific application for their scaffolds and those that do are focused on in vitro bioreactor environments. Finally, this review also demonstrates a scarcity of studies that combine CFD with optimization methods to improve scaffold design. This highlights an important direction of research for the development of the next generation of BTE scaffolds.

Surgical reconstructive treatment for infraosseous peri-implantitis defects with a submerged healing approach: A prospective controlled study

BACKGROUND

The aim of this study was to assess the reconstructive potential of a submerged healing approach for the treatment of infraosseous peri-implantitis defects.

METHODS

Patients with a diagnosis of peri-implantitis were recruited. Implant suprastructures were removed before the surgical treatment, which included implant surface and defect detoxification using implantoplasty, air-power driven devices, and locally delivered antibiotics. The augmentation procedure included a composite bone graft and a non-resorbable membrane followed by primary wound coverage and a submerged healing of 8 months, at which point membranes were removed, and peri-implant defect measurements were obtained as the primary outcome. Secondary endpoints included assessment of cone-beam computed tomography (CBCT) and probing depth (PD) reductions.

RESULTS

Thirty implants in 22 patients were treated. A significant clinical bone gain of 3.22 ± 0.41 mm was observed at 8 months. Radiographic analysis also showed an average gain of 3.47 ± 0.41 mm. Three months after installment of new crowns, final PD measures showed a significant reduction compared to initial examinations and a significant reduction in bleeding on probing compared to examinations at the pre-surgical visit.

CONCLUSIONS

Reconstruction of infraosseous peri-implantitis defects is feasible with thorough detoxification of implant sites, and a submerged regenerative healing approach.