SLA-3d printed building and characteristics of GelMA/HAP biomaterials with gradient porous structure.

Developing a gradient porous scaffold similar to bone structure is gaining increasing attention in bone tissue engineering. The GelMA/HAP hydrogel has demonstrated potential in bone repair. Although 3D printing can build GelMA/HAP with porous structure, fabricating porous GelMA/HAP with gradient porosity and pore size in one step remains challenging. In this paper, a gradient porous structure with controllable pore size, based on gelatin methacryloyl (GelMA) and hydxroxyapatite (HAP), was engineered and printed using stereolithography. Firstly, the GelMA and HAP were mixed to prepare a hydrogel with a solid content ranging from 10 wt% to 50 wt% for stereolithography. Taking advantage of the sol-gel characteristics of GelMA/HAP hydrogel, GelMA/HAP was fed on the workbench through a combination of extrusion and paving to form a thin layer. During the curing of each layer, the hydrogel exposed to the curing of a single UV beam immediately solidified, forming a highly interconnected porous structure. Additionally, the hydrogel outside the scanning range could be further polymerized to form a relatively dense structure due to the residual laser energy. Finally, without gradient structural design or changing printing parameters, the gradient porous structure of bone-like could be printed in a single-step process. By adjusting the curing parameters of the single UV beam and the concentration and size of ceramic in the hydrogel, the printed pore diameter of the spongy structure could be controlled within the range of 50-260 µm, while the thickness of the compact area could be adjusted within 130-670 µm.

Finite element analysis and clinical application of 3D-printed Ti alloy implant for the reconstruction of mandibular defects.

BACKGROUND: The reconstruction of segmental defect of the mandible has always been a challenge. The customized reconstruction plate without a bone graft is also considered a transitional means of rehabilitation and reconstruction in some cases. METHODS: This study evaluated the biomechanical behaviors of customized plates with different structural designs comparing with commercial plates using the finite element method in reconstrution of the lateral mandible defect. RESULTS: Simulations revealed the stress state in the plate bodies, bone tissues and screws were associated with the width, height, thickness of the plates as well as the distribution of screws. In all of the groups, the system of 16 mm-high, 2.8 mm-thick customized reconstruction plate with 10 screws was considered to be the most ideal design because of the most harmonious biomechanical state. What's more, the stress shielding effects were not obvious in this experiment. Based on the above findings, we conducted a clinical case analysis to verify the mechanical properties of customized reconstruction and obtained a satisfactory operation result. CONCLUSIONS: The results show that by adjusting the contour parameters of the reconstruction plates, an ideal and reliable customized plate can be manufactured. And the customized 3D-printed Ti alloy implant will be a new way to achieve mandibular reconstruction in patients unable to perform autologous bone graft surgery. TRIAL REGISTRATION: The present trial has been registered with ChiCTR, the registration number is ChiCTR 2,000,038,973 on 11/10/2020.

Finite element analysis of 3D-printed personalized titanium plates for mandibular angle fracture.

This paper discussed the size of 3 D-printed personalized titanium plates that can gain maximum stability of mandibular fracture and minimize stress shielding through finite element analysis. A 3 D virtual model of mandible with mandibular angle fracture was created from the CT data of patient. 3 D-printed personalized titanium plates varying in length and thickness were designed, and finite element analysis was performed under different loading conditions and fracture healing periods. After that, the stress distribution and deformation of the mandible with gonial fracture could be observed, and the stress shielding rate could be obtained. Finally, SPSS21.0 was used for statistical analysis. The results of finite element analysis indicated that as the thickness of titanium plates and the healing time decreased, the maximum displacement increased, under a certain condition in which the pore size, the width, the hole distance and the bridge spacing were 2.0 mm, 4.0 mm, 6.0 mm, 12.0 mm, respectively. What's more, in this condition, the thicker the titanium plate and the shorter the healing time were, the higher the stress shielding was at central occlusion. When the thickness of the personalized 3 D-printed titanium plate was 1.0 mm, the maximum displacement tended to be stable and the stress shielding was minimized. It can not only improve the bone stability after tension band fixation, but also minimize the stress shielding, which is expected to expand the indications of tension band fixation.

Hard Tissue Preservation and Recovery in Minimally Invasive Alveolar Surgery Using Three-Dimensional Printing Guide Plate.

BACKGROUND: For completely impacted teeth, it is of great significance to locate teeth accurately, preserve hard tissue and recovering the height of alveolar ridge. This can be effectively solved by the digital three-dimensional printing guide technology. METHODS: Ten patients with completely impacted tooth were selected in this experiment. After cone-beam computed tomography scan, the dicom formal computed tomography data was analyzed for threedimensional reconstruction by mimics 17.0 software. Then determining the surgical plan and making surgical guide plate. Threedimensional printing guide plate assisted piezosurgery was used to remove bone and extract impacted teeth. After that, the removed bone cap was back to the original position. Cone-beam computed tomography was used for each operated patients after 1 week and 6 months. RESULT: The surgical guide plates can locate teeth accurately and the surgery time was reduced for all patients. A week later, all patients healed well and removed the stitches on time. Cone-beam computed tomography showed that the retention of bone caps was good and there was no displacement. All patients showed a normal parameter of pain. Six months later, cone-beam computed tomography showed good bone formation in the extraction area, which filled with new bones completely. The recovery of bone outline and height of alveolar crest at the surgical site were basically consistent with those before the operation. CONCLUSIONS: Three-dimensional printing guide plates combining with fenestration and bone-cap restoration can locate impacted teeth accurately, reduce the extraction volume of bone, shorten surgery time, and alleviate complications. This was conducive to preserve and restore hard tissue and had great prospective.

Transit amplifying cells coordinate mouse incisor mesenchymal stem cell activation.

Stem cells (SCs) receive inductive cues from the surrounding microenvironment and cells. Limited molecular evidence has connected tissue-specific mesenchymal stem cells (MSCs) with mesenchymal transit amplifying cells (MTACs). Using mouse incisor as the model, we discover a population of MSCs neibouring to the MTACs and epithelial SCs. With Notch signaling as the key regulator, we disclose molecular proof and lineage tracing evidence showing the distinct MSCs contribute to incisor MTACs and the other mesenchymal cell lineages. MTACs can feedback and regulate the homeostasis and activation of CL-MSCs through Delta-like 1 homolog (Dlk1), which balances MSCs-MTACs number and the lineage differentiation. Dlk1's function on SCs priming and self-renewal depends on its biological forms and its gene expression is under dynamic epigenetic control. Our findings can be validated in clinical samples and applied to accelerate tooth wound healing, providing an intriguing insight of how to direct SCs towards tissue regeneration.

A study on biosafety of HAP ceramic prepared by SLA-3D printing technology directly.

Hydroxyapatite powder was mixed into photosensitive resin to form complex shape scaffold using SLA-3D printing technology, and then the final entity was obtained successively by debinding and sintering. It is crucial to confirm whether the prepared hydroxyapatite scaffold have the toxic effects after our designed printing, debinding, and sintering processes because the photosensitive resin in the starting printing paste is poisonous to cells. To investigate these issues in details, thermogravimetric analysis (TG), differential scanning calorimetry (DSC), in vitro cytotoxicity test, and implantation pre-experiment in the rabbit parietal were performed, aiming to develop the SLA-3D prepared hydroxyapatite scaffold. Through thermal analysis, it was proved that photosensitive resin would be completely pyrolyzed at temperature ranging from 350 °C to 580 °C, corresponding to a secondary chemical reaction mechanism. Combined with cytotoxicity test results, it is unquestionable that the toxic substances would be totally decomposed after debinding process and a good biocompatible HAP samples could be obtained. The finally prepared HAP samples with micro-holes showed good biosafety in pre-experiment of the rabbit parietal implantation.

Application of Three-Dimensional Printing Technology for Improved Orbital-Maxillary-Zygomatic Reconstruction.

The reconstruction of orbital-maxillary-zygomatic complex (OMZC) on patients suffering from trauma and space-occupying lesions is challenging due to the irregularity of craniomaxillofacial bones. To overcome the challenge in precise OMZC reconstruction, individual three-dimensional (3D) disease models and mirror-imaged 3D reconstruction models were printed on the basis of the computer tomography. Preoperative planning by rehearsing surgical procedures was made on the 3D disease models and the scaffolds including titanium and absorbable meshes or plates were anatomically premolded using the mirror-imaged 3D models as guide. Many benefits were achieved including more precise OMZC reconstruction, fluent and smooth procedures of surgeries, shorter operation time, less blood loss, and improved cosmetic outcomes of craniomaxillofacial shapes. There were no complications such as diplopia, infection, foreign body reaction, exophthalmos, enophthalmos, disordered occlusal relationship, and hematoma. And patients were satisfied with the functional and esthetic outcome during the following-up time. Therefore, OMZC reconstruction can be optimized and successful through preoperative planning and premolded scaffolds with 3D printing bone model by computer-aid design and manufacturing.

Endoscope-assisted resection of nonneoplastic space-occupying lesion in oral and maxillofacial areas.

Endoscope-assisted oral and maxillofacial surgeries have been applied to the resection of tumors with minimal invasion and good cosmetic outcomes. However, with regard to endoscope-assisted resection of nonneoplastic space-occupying lesion (NSOL) in oral and maxillofacial areas which differ from tumors in treatment, there are no systematic reports. Therefore the advantages and limitations of the endoscopy-assisted approach (EAA) in resection of NSOL remain unclear. In this novel study we describe endoscope technique for resection of NSOL in face and submandibular areas and compare the feasibility and effectiveness of EAA with external approach (EA). Eleven patients underwent EAA and 20 patients underwent EA procedures. The perioperative and postoperative outcomes of the patients were evaluated. The resection of NSOL with EAA was completed successfully with a shorter hospitalization duration, less bleeding, a smaller incison and better satisfaction with appearance than with the EA procedure (P < 0.01). Our study showed that endoscope-assisted resection of NSOL is technically safe, feasible and practicable. Good cosmetic results with minimal invasion can be achieved with this new technique and therefore this may be a promising new standard procedure in oral and maxillofacial areas.

Acidic pH environment induces autophagy in osteoblasts.

Osteoblasts (OBs) play an important role in bone fracture healing, yet the extreme adverse microenvironment in fracture sites has a negative impact on the survival of OBs. Therefore, it is important to study how OBs behave in the complex fracture microenvironment. Studies have shown that autophagy plays a pivotal role in maintaining cellular homeostasis and defending the cell against adverse microenvironments. In this study we found the induction of autophagy in OBs at femoral bone fracture sites, which may be a result of ischemia, oxidative stress and hypoxia within the local area. At fracture sites a low pH environment also developed. Until now it has been unclear whether the induction of autophagy in osteoblasts is triggered by the acidic pH environment. Therefore, we cultured OBs in vitro in media of different pH values, and found both autophagy and apoptosis increased in OBs in acidic conditions. However, when autophagy inhibitor chloroquine (CQ) was used, apoptosis increased significantly compared with that without CQ. Thus indicating that inhibition of autophagy may promote apoptosis in OBs in an acidic environment, which may provide a new therapeutic strategy to decrease cell apoptosis in OBs through the use of drugs that modulate the autophagic state.

Magnetic Resonance Imaging (MRI) Evaluation for Anterior Disc Displacement of the Temporomandibular Joint.

BACKGROUND Magnetic resonance imaging (MRI) is the criterion standard imaging technique for visualization of the temporomandibular joint (TMJ) region, and is currently considered the optimum modality for comprehensive evaluation in patients with temporomandibular joint disorder (TMD). This study was aimed at finding the value of MRI in pre-clinical diagnosis of TMJ disc displacement. MATERIAL AND METHODS Patients primarily diagnosed as having anterior disc displacement by clinical symptoms and X-ray were selected in the present study. MRI was used to evaluate surrounding anatomical structures and position, as well as morphological and signal intensity change between patients and normal controls. RESULTS Posterior band position was significantly different between the patient group and control group. At the maximum opened-mouth position, the location of disc intermediate zone returned to normal. At closed-mouth position, the thickness of anterior and middle, but not posterior, band increased. The motion range of the condyle in the anterior disc displacement without reduction (ADDWR) patient group was significantly less than the value in the anterior disc displacement with reduction (ADDR) patient group and the control group. Whether at closed-mouth position or maximum opened-mouth position, the exudate volume in the patient group was greater than in the normal group. CONCLUSIONS MRI can be successfully used to evaluate multiple morphological changes at different mouth positions of normal volunteers and patients. The disc-condyle relationship can serve as an important indicator in assessing anterior disc displacement, and can be used to distinguish disc displacement with or without reduction.

Study on angle of immediate loading of immediate implant placement.

OBJECTIVE: To investigate the clinical immediate load at an angle after immediate placement of the implant. METHODS: Select 4 adult dogs; through establishing the angle loading animal experiment model, perform lateral loading on 32 implants respectively at vertical and 0°, 10°, and 20°, with which as a basis for grouping, determine the osseointegration index and new bone growth rate; and observe the peri-implant bone remodeling conditions. RESULTS: The 20° group is found with the most obvious bone absorption, and compared with other groups, its osseointegration index and new bone growth rate are statistically significant (P < 0.01); bone remodeling under 0° load stress is the best, with the formation of new bone and the highest bone contact ratio, which is the most reasonable under this the stress distribution compared with other angles. CONCLUSIONS: The implant stress distribution at 0° against the occlusal force direction is closer to physiologic optimum stress on the implant bone interface, and it is permitted for the long axis of the immediately implanted and immediately loaded implant to be tilted within about 10° against the load angle.

Adipose-derived stem cells transfected with pEGFP-OSX enhance bone formation during distraction osteogenesis.

This study was designed to investigate the effects of local delivery of adipose-derived stem cells (ADSCs) transfected with transcription factor osterix (OSX) on bone formation during distraction osteogenesis. New Zealand white rabbits (n=54) were randomly divided into three groups (18 rabbits per group). A directed cloning technique was used for the construction of recombinant plasmid pEGFP-OSX, where EGFP is the enhanced green fluorescence protein. After osteodistraction of the right mandible of all experimental rabbits, rabbits in group A were treated with ADSCs transfected with pEGFP-OSX, group B with ADSCs transfected with pEGFP-N1, and group C with physiological saline. Radiographic and histological examinations were processed after half of the animals within each group were humanely killed by injection of sodium pentothal at Week 2 or 6 after surgery. The distraction bone density was measured as its projectional bone mineral density (BMD). Three parameters were measured, namely, the thickness of new trabeculae (TNT), and the volumes of the newly generated cortical bone (NBV1) and the cancellous bone (NBV2) of the distracted regions. Good bone generation in the distraction areas was found in group A, which had the highest BMD, TNT, and NBV in the distraction zones among the groups. There was no significant difference in bone generation in the distraction areas between groups B and C. The results indicate that the transplantation of ADSCs transfected with pEGFP-OSX can effectively promote bone generation during distraction in vivo.

Transcription factor osterix modified bone marrow mesenchymal stem cells enhance callus formation during distraction osteogenesis.

This study was designed to investigate the effects of local delivery of bone marrow mesenchymal stem cells (BMMSCs) with or without osterix (OSX) gene transfected on bone regeneration in the distracted zone using a rabbit model of mandibular lengthening. Fifty-four New Zealand white rabbits underwent osteodistraction of the left mandible and were then randomly divided into group A, group B, and group C (n = 18 for each group). At the end of distraction BMMSCs transfected with OSX, autologous BMMSCs and physiological saline were injected into the distraction gaps in groups A, B, and C, respectively. Nine animals from each group were humanely killed at 2 and 6 weeks after completion of distraction. The distracted mandibles were harvested and processed for radiographic, histological, and immunohistochemical examination. Excellent bone formation in the distracted callus was observed in group A and group B; the former showed better bone formation and highest bone mineral density (BMD), thickness of new trabeculae (TNT, mm) and volumes of the newly formed bone area (NBV) in the distraction zones. Group C animals showed poor bone formation in the distracted callus when compared with groups A and B. Positive immunostaining of bone sialoprotein (BSP) was observed in the distracted callus in all groups; however, BSP expression was much stronger in group A than in groups B and C. The results of this study suggest transplantation of BMMSCs can promote bone formation in DO; OSX-mediated ex vivo gene therapy was more effective during bone deposition and callus formation in distraction osteogenesis.

[An experimental study of intra-articular injection of NG-methyl-L-arginine for the treatment of indirect temporomandibular joint trauma in goats].

PURPOSE: To investigate the efficacy of NG-methyl-L-arginine(L-NMMA) for treatment of indirect temporomandibular joint trauma in goats. METHODS: Trauma to TMJ in 9 goats were exerted under an impact to the right and left mandibular angle with self-made device, L-NMMA (0.5 mL) were injected into the right TMJs after 3 hours, 7 days, 14 days, 21 days; the left TMJs were injected with normal saline and used as a control. The goats were killed after 3 months. The TMJs of goats were examined with scanning electron microscopy and light microscopy when sacrificed and scored in a subjective manner following the standard criteria which was a modification of the method by Mankin et al and Yoshimi et al. GLM model of SAS 9.0 software package was used to evaluate the scores of the treatment sides and control sides. RESULTS: Under light microscopy and scanning electron microscopy, the left TMJ tissues showed severe osteoarthrotic changes in the temporal surface,disk and condyle, the right TMJ tissues showed significant improvement (P<0.05). CONCLUSIONS: Repeated intra-articular injection of L-NMMA may reduce the destruction of indirect trauma on goat TMJs.

Transarterial embolization of a high-flow maxillary arteriovenous malformation fed by multiple arteries.

A high-flow maxillary arteriovenous malformation fed by multiple arteries, including bilateral internal maxillary arteries and ophthalmic artery, is reported. A combination of polyvinyl alcohol particles and N-butyl-cyanoacrylate mixed with lipiodol was progressively deposited within the distal vascular bed by transarterial superselective embolization of the branches of bilateral internal maxillary arteries, resulting in complete anatomic and clinical cure. The authors feel that this approach is more secure and effective compared with transfemoral venous embolization and direct transosseous puncture. It also avoids mutilating surgery.

[Association of transforming growth factor-alpha gene polymorphism and environment factors with nonsyndromic cleft lip with or without cleft palate in Han nationality].

OBJECTIVE: To study the association of transforming growth factor-alpha (TGF-alpha gene polymorphism and environment factors with nonsyndromic cleft lip with or without cleft palate (NSCLP) in Han nationality. METHODS: Data related to infection, drug intake and folic acid supplement during pregnancy were gained through investigation of mothers. Polymerase chain reaction combined with restrict enzyme digestion was used to detect the target gene variation in 199 patients with NSCL/P and 203 healthy controls. Analysis was carried on the genotype and infection,drug intake and folic acid supplement. RESULTS: The C2 allele frequency in patients with NSCL/P was significantly higher than that in healthy controls. There was a significant increase of patients with NSCL/P in pregnant women exposed to infection, drug intake and folic acid deficiency. There was an interaction between C1C2 genetype and infection, drug intake and folic acid supplement. CONCLUSION: TGF-alpha gene polymorphism is associated with NSCL/P. Infection, drug intake and folic acid supplement during pregnancy were associated with the occurrence of NSCL/P. Individuals containing C2 allele were more sensitive to infection, drug intake and folic acid deficiency.

[Relationship between transforming growth factor-alpha gene polymorphism and non-syndromic cleft lip with cleft palate].

OBJECTIVE: To study the association of TGF-alpha gene polymorphism and non-syndromic cleft lip with cleft palate in Shandong province. METHODS: Polymerase chain reaction combined with restrict enzyme digestion was used to detect the target gene variation in 98 patients with non-syndromic cleft lip with cleft palate and 101 healthy controls. RESULTS: The C2 allele frequency in patients with non-syndromic cleft lip with cleft palate was significantly higher than that in healthy controls. The genotype frequency in patients with positive family history was significantly higher than that without positive family history. CONCLUSION: TGF-alpha gene polymorphism is closely associated with non-syndromic cleft lip with cleft palate in Shandong, especially in patients with positive family history.

[Application of low intensity ultrasound in the extraction of totally impacted mandibular third molars].

PURPOSE: To observe the clinical effects of low intensity ultrasound in extraction of totally impacted third molars. METHODS: 40 patients with totally impacted third molars on both sides of the mandible verified by X-ray were selected. After extraction of the teeth, the socket on one side was treated with low intensity ultrasound while the other side underwent no treatment. Statistical analysis was performed with SPSS 10.0 on all patients in form of pain, swelling, dry socket and bone healing. RESULTS: In the experimental group, 4 patients complained of severe pain while 16 patients in the control group (P < 0.05). Moderate or severe swelling were not uncommon in both experimental and control groups (P > 0.05); No patients suffered from dry socket in the experimental group and 4 patients suffered from dry socket in the control group (P < 0.05); There were 35 patients with complete bone healing in the experimental group while 21 patients with complete bone healing in the control group (P < 0.01). CONCLUSIONS: The use of low intensity ultrasound in extraction of totally impacted mandibular third molars reduced the severity of post-operative pain and the incidence dry socket, and it also stimulated bone healing, but it showed no effect on relieving post-operative swelling.

[Histopathological study of the effects of intra-articular injection of triamcinolone acetonide on temporomandibular joint osteoarthrosis in goats].

PURPOSE: The aim of this study was to investigate the histopathological changes of human temporomandibular joint osteoarthrosis following intra-articular injection of triamcinolone acetonide, and compare the results to these of control group. METHODS: The upper compartments of both joints of 10 goats were injected with 0.8 ml collagenase I to induce osteoarthrosis. The 10 goats were then equally divided into control group and experimental group. The first and second treatment were carried out 30 and 60 days after injection of collagenase I, respectively. The animals were sacrificed 90 days after the first treatment. The specimens of the animal TMJ were harvested, histologically examined under light microscopy and scanning electron microscopy, and scored in a subjective manner following the criteria which was a modification of the method of Mankin et al and Yoshimi et al. GLM model in SAS software package was adopted to compare the differences between the control group and experimental group. RESULTS: Under light microscopy and scanning electron microscopy, the condyle, meniscus and glenoid fossa of the control group demonstrated distinct osteoarthrosis; the histopathologic changes in the experimental group was more serious than the control group, and the differences of the histologic scores were significant between the two groups (P<0.01). CONCLUSION: Intra-articular injection of triamcinolone acetonide as a lytic agent will worsen for articular cartilage reparation.

[Clinical study of bioglass for repairing alveolar cleft.].

PURPOSE: To analyse the results of using Bioglass to repair alveolar cleft. METHODS: Thirty-nine cases with alveolar cleft were divided into two groups. In group A, autogenous iliac cancellous bone were transplanted into the cleft to repair alveolar defect in 25 cases, while artificial bone-Bioglass was used in group B of 14 cases. The results of two groups were compared with a follow up of 12 months. RESULTS: New bone formation was perfect in grafted area and canines can emerge from the bone grafted areas observed from the X-ray films both in group A and group B. Statistical analysis showed no significant difference between group A and group B in the clinical success rate of alveolar cleft repair. However, there was significant difference between complete alveolar cleft and incomplete alveolar cleft in group A and group B. CONCLUSION: Bioglass can result in new bone formation and eruption of canines from the bone grafted areas. The application of Bioglass in repairing of alveolar cleft provides a new therapy for alveolar cleft patients.