Harnessing 3D printed highly porous Ti-6Al-4V scaffolds coated with graphene oxide to promote osteogenesis.

Bone tissue engineering (BTE) strategies have been developed to address challenges in orthopedic and dental therapy by expediting osseointegration and new bone formation. In this study, we developed irregular porous Ti-6Al-4V scaffolds coated with reduced graphene oxide (rGO), specifically rGO-pTi, and investigated their ability to stimulate osseointegration in vivo. The rGO-pTi scaffolds exhibited unique irregular micropores and high hydrophilicity, facilitating protein adsorption and cell growth. In vitro assays revealed that the rGO-pTi scaffolds increased alkaline phosphatase (ALP) activity, mineralization nodule formation, and osteogenic gene upregulation in MC3T3-E1 preosteoblasts. Moreover, in vivo transplantation of rGO-pTi scaffolds in rabbit calvarial bone defects showed improved bone matrix formation and osseointegration without hemorrhage. These findings highlight the potential of combining rGO with irregular micropores as a promising BTE scaffold for bone regeneration.

Efficacy of closed cell self expandable metallic stent for peripheral arterial disease in the porcine iliac artery.

This study aimed to investigate the efficacy of a closed-cell self-expandable metallic stent (SEMS) with or without expanded-polytetrafluoroethylene (e-PTFE)-covering membrane in a porcine iliac artery model. Twelve Yorkshire domestic pigs were divided into a bare closed-cell SEMS (B-SEMS) group (n = 6) and covered closed-cell SEMS (C-SEMS) group (n = 6). Both closed-cell SEMSs were placed in the right or left iliac artery. Thrombogenicity score in the C-SEMS group was significantly higher than that in the B-SEMS group (p = 0.004) after 4 weeks. Angiographic findings of mean luminal diameters at 4 weeks follow-up did not differ significantly between B-SEMS and C-SEMS groups. Neointimal hyperplasia thickness as well as degree of inflammatory cell infiltration and collagen deposition in the C-SEMS group was significantly greater than that in the B-SEMS group (p < 0.001). Closed-cell SEMSs successfully maintained patency for 4 weeks without stent-related complications in the porcine iliac artery. Although mild thrombus with neointimal hyperplasia was observed in the C-SEMS group, subsequent occlusion, and in-stent stenosis did not occur in any of the pigs until the end of the study. Closed-cell SEMS with or without the e-PTFE covering membrane is effective and safe for the porcine iliac artery.

Efficacy of thermoplastic polyurethane and gelatin blended nanofibers covered stent graft in the porcine iliac artery.

Stent-grafts composed of expanded polytetrafluoroethylene (e-PTFE), polyethylene terephthalate (PET) and polyurethane (PU) are characterized by poor endothelialization, high modulus, and low compliance, leading to thrombosis and intimal hyperplasia. A composite synthetic/natural matrix is considered a promising alternative to conventional synthetic stent-grafts. This study aimed to investigate the efficacy of thermoplastic polyurethane (TPU) and gelatin (GL) blended nanofibers (NFs) covered stent-graft in the porcine iliac artery. Twelve pigs were randomly sacrificed 7 days (n = 6) and 28 days (n = 6) after stent-graft placement. The thrombogenicity score at 28 days was significantly increased compared at 7 days (p < 0.001). The thickness of neointimal hyperplasia, degree of inflammatory cell infiltration, and degree of collagen deposition were significantly higher at 28 days than at 7 days (all p < 0.001). The TPU and GL blended NFs-covered stent-grafts successfully maintained the patency for 28 days in the porcine iliac artery. Although thrombosis with neointimal tissue were observed, no subsequent occlusion of the stent-graft was noted until the end of the study. Composite synthetic/natural matrix-covered stent-grafts may be promising for prolonging stent-graft patency.

Enhanced osseointegration through direct energy deposition porous coating for cementless orthopedic implant fixation.

Direct energy deposition (DED) is a newly developed 3D metal printing technique that can be utilized on a porous surface coating of joint implants, however there is still a lack of studies on what advantages DED has over conventional techniques. We conducted a systematic mechanical and biological comparative study of porous coatings prepared using the DED method and other commercially available technologies including titanium plasma spray (TPS), and powder bed fusion (PBF). DED showed higher porosity surface (48.54%) than TPS (21.4%) and PBF (35.91%) with comparable fatigue cycle. At initial cell adhesion, cells on DED and PBF surface appeared to spread well with distinct actin stress fibers through immunofluorescence study. It means that the osteoblasts bind more strongly to the DED and PBF surface. Also, DED surface showed higher cell proliferation (1.27 times higher than TPS and PBF) and osteoblast cell activity (1.28 times higher than PBF) for 2 weeks culture in vitro test. In addition, DED surface showed better bone to implant contact and new bone formation than TPS in in vivo study. DED surface also showed consistently good osseointegration performance throughout the early and late period of osseointegration. Collectively, these results show that the DED coating method is an innovative technology that can be utilized to make cementless joint implants.

Optimal Position of Attachment for Removable Thermoplastic Aligner on the Lower Canine Using Finite Element Analysis.

Malocclusion is considered as a developmental disorder rather than a disease, and it may be affected by the composition and proportions of masseter muscle fibers. Orthodontics is a specialty of dentistry that deals with diagnosis and care of various irregular bite and/or malocclusion. Recent developments of 3D scanner and 3D printing technology has led to the use of a removable thermoplastic aligner (RTA), which is widely used due to its aesthetic excellence, comfortableness, and time efficiency. However, orthodontics using only an RTA has lower treatment efficacy and accuracy due to the differing movement of teeth from the plan. In order to improve these disadvantages, attachments were used, and biomechanical analyses were performed with and without them. However, there is insufficient research on the movement of teeth and the transfer of load according to the attachment position and shape. Therefore, in our study, we aimed to identify the optimal shape and position of attachments by analyzing various shapes and positions of attachments. Through 3D finite element analysis (FEA), simple tooth shape and mandibular canine shape were extracted in order to construct the orthodontics model which took into account the various shapes and positions of attachments. The optimal shape of a cylinder was derived through the FEA of simple tooth shape and analyzing various positions of attachments on teeth revealed that fixing the attachments at the lingual side of the tooth rather than the buccal side allowed for torque control and an effective movement of the teeth. Therefore, we suggest fixing the attachments at the lingual side rather than the buccal side of the tooth to induce effective movement of teeth in orthodontic treatment with the RTA in case of canine teeth.

Mechanical Assessment of Fatigue Characteristics between Single- and Multi-Directional Cyclic Loading Modes on a Dental Implant System.

Mechanical testing based on ISO 14801 standard is generally used to evaluate the performance of the dental implant system according to material and design changes. However, the test method is difficult to reflect on the clinical environment because the ISO 14801 standard does not take into account the various loads from different directions during chewing motion. In addition, the fracture pattern of the implant system can occur both in the horizontal and the vertical directions. Therefore, the purpose of this study was to compare fatigue characteristics and fracture patterns between single directional loading conditions based on the ISO 14801 standard and multi-directional loading condition. Firstly, the static test was performed on five specimens to derive the fatigue load, and the fatigue load was chosen as 40% of the maximum load measured in the static test. Subsequently, the fatigue test was performed considering the single axial/occlusal (AO), AO with facial/lingual (AOFL) and AO with mesial/distal (AOMD) directions, and five specimens were used for each fatigue loading modes. In order to analyze the fatigue characteristics, the fatigue cycle at the time of specimen fracture and displacement change of the specimen every 500 cycles were measured. Field emission scanning electron microscopy (FE-SEM) was used to analyze the fracture patterns and the fracture surface. Compared to the AO group, the fatigue cycle of the AOFL and AOMD groups showed lower about five times, while the displacement gradually increased with every 500 cycles. From FE-SEM results, there were no different surface morphology characteristics among three groups. However, the AOMD group showed a vertical slip band. Therefore, our results suggest that the multi-directional loading mode under the worst-case environment can reproduce the vertical fracture pattern in the clinical situation and may be essential to reflect on the dental implant design including connection types and surface treatments.

Optimized Dental Implant Fixture Design for the Desirable Stress Distribution in the Surrounding Bone Region: A Biomechanical Analysis.

The initial stability of a dental implant is known to be an indicator of osseointegration at immediate loading upon insertion. Implant designs have a fundamental role in the initial stability. Although new designs with advanced surface technology have been suggested for the initial stability of implant systems, verification is not simple because of various assessment factors. Our study focused on comparing the initial stability between two different implant systems via design aspects. A simulated model corresponding to the first molar derived from the mandibular bone was constructed. Biomechanical characteristics between the two models were compared by finite element analysis (FEA). Mechanical testing was also performed to derive the maximum loads for the two implant systems. CMI IS-III active (IS-III) had a more desirable stress distribution than CMI IS-II active (IS-II) in the surrounding bone region. Moreover, IS-III decreased the stress transfer to the nerve under the axial loading direction more than IS-II. Changes of implant design did not affect the maximum load. Our analyses suggest that the optimized design (IS-III), which has a bigger bone volume without loss of initial fixation, may minimize the bone damage during fixture insertion and we expect greater effectiveness in older patients.

Finite Element Analysis of Novel Separable Fixture for Easy Retrievement in Case with Peri-Implantitis.

Peri-implantitis is a common complication following dental implant placement, which may lead to bone loss and fixation failure. With the conventional fixture, it is difficult to perfectly clear-up the infection. To solve this, we have designed a separable fixture of which the top part is replaceable. This study aimed to compare the structural and biomechanical stability of the separable and conventional fixture. A single surgical model corresponding to the first molar in a virtual mandible model and conventional/separable implants were reproduced to compare the biomechanical characteristics of the implants using finite element analysis (FEA). The loading condition was 200N preload in the first step, and 100N (Axial), 100N (15°), and 30N (45°) in the second step. The stress distribution on the cortical bone in the separable implant was lower than the conventional implant. In particular, the Peak von Mises Stress (PVMS) values of the separable implant under lateral load was found to be about twice as low as that of the conventional implant. In this study, we suggest that the separable implant has an equivalent biomechanical stability compared to the conventional implant, is easy to retrieve in the case of peri-implantitis, and has an excellent initial stability after the surgery when used in stage 2.

Hyaluronic Acid/PLGA Core/Shell Fiber Matrices Loaded with EGCG Beneficial to Diabetic Wound Healing.

During the last few decades, considerable research on diabetic wound healing strategies has been performed, but complete diabetic wound healing remains an unsolved problem, which constitutes an enormous biomedical burden. Herein, hyaluronic acid (HA)/poly(lactic-co-glycolic acid, PLGA) core/shell fiber matrices loaded with epigallocatechin-3-O-gallate (EGCG) (HA/PLGA-E) are fabricated by coaxial electrospinning. HA/PLGA-E core/shell fiber matrices are composed of randomly-oriented sub-micrometer fibers and have a 3D porous network structure. EGCG is uniformly dispersed in the shell and sustainedly released from the matrices in a stepwise manner by controlled diffusion and PLGA degradation over four weeks. EGCG does not adversely affect the thermomechanical properties of HA/PLGA-E matrices. The number of human dermal fibroblasts attached on HA/PLGA-E matrices is appreciably higher than that on HA/PLGA counterparts, while their proliferation is steadily retained on HA/PLGA-E matrices. The wound healing activity of HA/PLGA-E matrices is evaluated in streptozotocin-induced diabetic rats. After two weeks of surgical treatment, the wound areas are significantly reduced by the coverage with HA/PLGA-E matrices resulting from enhanced re-epithelialization/neovascularization and increased collagen deposition, compared with no treatment or HA/PLGA. In conclusion, the HA/PLGA-E matrices can be potentially exploited to craft strategies for the acceleration of diabetic wound healing and skin regeneration.