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BACKGROUND: In oral implant repair, soft tissue level implants are different from bone level implants, which adopt non-embedded surgical methods. A good neck design can promote bone bonding or reduce marginal bone absorption and facilitate the formation of stable soft tissue sealing. Therefore, the neck structure design of implants is one of the key factors for the success of implant repair. OBJECTIVE: To simulate and analyze the stress distribution of implant components and implant-bone interface during the restoration of mandibular molars with four different smooth collar implants using three-dimensional modeling and finite element analysis software. METHODS: The cone-beam CT image data of a patient undergoing mandibular first molar implantation were selected, and the mandible model was established by Mimics 21.0 software. The mandible model was imported into Solidworks 2018 software. Smooth neck implant models were constructed as follows: the standard conventional cervical implant (2.8 mm in height, 4.8 mm in diameter), standard wide cervical implant (2.8 mm in height, 6.5 mm in diameter), aesthetic conventional neck implant (1.8 mm in height, 4.8 mm in diameter), and aesthetic wide neck implant (1.8 mm in height, 6.5 mm in diameter). The four models were repaired with pure titanium base table and zirconia full-crown screw fixation. The von-Mises stress distribution of implant components and the implant-bone interface in four groups of different smooth collar implants were compared and analyzed under vertical and oblique loadings. RESULTS AND CONCLUSION: (1) Whether it was vertical loading or oblique loading, the peak values of von-Mises stress were located in the neck region of the implant, and the peak values of von-Mises stress at the implant-bone interface were located in the cortical bone region of the neck region of the implant. (2) When using the same smooth collar implant, compared with the vertical loading group, the peak values of Von-Mises stress were greater in the four different smooth collar implants in the oblique loading group. (3) Under vertical or oblique loading, the maximum von-Mises stress of the standard implant group was greater than that of the standard implant group, and the maximum von-Mises stress of the aesthetic implant group was lower than that of the aesthetic implant group. (4) The maximum von-Mises stress on the implant-bone interface in the wide-neck standard implant group was lower than that in the other smooth cervical implant groups, regardless of vertical or oblique loading. (5) The results showed that the stress distribution of implant components and implant-bone interface was different with different smooth collar implants. [ABSTRACT FROM AUTHOR]

BACKGROUND: In oral implant restoration, patients with single missing maxillary anterior teeth often have alveolar bone absorption and defect due to different reasons. To avoid the risk of bone grafting, inclined implants are often used to avoid the alveolar bone absorption area. The angle abutment is used to restore the normal overcovering relationship of patients. The size and distribution of the influence of different abutment materials on the occlusal force transfer of the implant and the surrounding bone were studied. OBJECTIVE: To compare the influence of time on the peak value of bone stress around the implant with three abutment materials under simulated dynamic loading under three implantation conditions. METHODS: Cone beam CT data of a healthy adult undergoing implant restoration of maxillary central incisor were selected. Minics software was used to cut the jaw bone. Solidworks 2018 was used to establish the implant, jaw bone, and angle abutment (angle 0°, 15°, and 25°). Base stations materials included pure titanium, zirconium dioxide, and alumina), central screw, and zirconium dioxide full porcelain crown model. Assembly was complete, for embedded in the original maxillary fang root cutting direction 0° angle, then simulated palate to tilt 15° and 25°, no implanted implant thread exposure. According to different implant angles, they were divided into 0°, 15°, and 25° groups. Dynamic loading was performed for 0.2 seconds, to obtain the time-dependent relationship between the peak value of equivalent stress of bone around the implant prosthesis of each material abutment. RESULTS AND CONCLUSION: (1) All abutment implant restorations had the same peak distribution of surrounding bone stress when they were subjected to occlusal force, all of which were located in the bone cortex of the implant neck. The fastest time period for the increase of bone stress around abutment implant restorations of each material was within 0.025-0.05 seconds. The range of high stress value of cortical bone in the 15° group was larger than that in the 0° group. The initial stress value of cortical bone of implant in the 25° group was significantly higher than that of the other two groups. The residual stress value of cortical bone was higher after loading. After titanium abutment implantation, the bone stress around the prosthesis had the largest increase, and the range of high stress value was relatively concentrated. (2) In the 15° group, the peak value of bone stress around the implanted prosthesis on the abutment of the three materials was located in the neck of the implant. The increase in bone stress around the titanium abutment implanted prosthesis was relatively large but not obvious, and the distribution range of high stress was relatively consistent. Compared with the other two groups, the high stress value of the 25° group was more concentrated; the initial stress value was higher and the range of change was greater, among which the bone stress around the implanted prosthesis on the dialumina abutment increased the most within 0-0.1 seconds. At 0.2 seconds, the peak value of bone equivalent stress of zirconia abutment decreased to 0, and high residual stress remained in the bone around the implants of the other two abutments. (3) It is concluded that based on the analysis of the distribution of different influences of the implant angle and abutment material on the bone interface, the bone stress of the implants using zirconia abutment was relatively stable at all time points in the three groups. [ABSTRACT FROM AUTHOR]

BACKGROUND: Stroke has become one of the thorny diseases facing the world due to its high morbidity, high mortality, high disability rate, and high recurrence rate. However, traditional rehabilitation methods, characterized by slow effect, low efficiency, and dull training, elicit little effects in the treatment of stroke. With the development of science and technology, virtual reality technology which has the characteristics of simplicity, high efficiency, high security, strong interest, low price, and real-time feedback can solve the imbalance of doctor-patient ratio, promote the development of remote rehabilitation medicine, and has extremely important practical significance for the rehabilitation of stroke patients. OBJECTIVE: To study the research hotspots and progress of virtual reality technology in stroke treatment using Citespace V knowledge graph software, and to clarify the structural model of this field and predict the possible development trends of virtual reality technology worldwide in the future. METHODS: A total of 1 374 core articles addressing virtual reality technology published since 2007 were retrieved from Web of ScienceTM, CNKI, CSSCI, and CSCD database and used as data sources. Citespace V knowledge graph software was used to analyze the research status of virtual reality technology in stroke treatment. In addition, the domestic and foreign differences in disciplines, countries, authors, institutions, and research hotspots were compared. Then, the possible development trend in the future was predicted. RESULTS AND CONCLUSION: The foreign countries have formed a multi-disciplinary and multi-domain comprehensive group, focusing on neuroscience, computer science, and biomedical engineering. Domestic disciplines are relatively monotonous, and no obvious discipline group has formed. There is a network of close exchanges and cooperation that has formed between foreign countries/regions, authors, and institutions, forming a high school mentality of countries, authors, and institutions. The cooperation among domestic authors, groups and institutions is poor, with geographical restrictions, and there is a lack of influential academic groups and institutions. There are differences in research contents at home and abroad, and there have been four development stages of this technology in foreign countries. The possible trends of future research abroad are the research, development and evaluation of remote rehabilitation medicine, robot-assisted therapy, and virtual rehabilitation system, highlighting the screening of virtual rehabilitation therapy. The possible future research topics in China may be the effect and evaluation of the combined treatment of specific parts with virtual reality technology and other methods, and the introduction and development of advanced technology. [ABSTRACT FROM AUTHOR]

BACKGROUND: Despite three-dimensional (3D) finite element model is helpful for the analysis of the injury mechanism and mechanical characteristics of knee joint, there are few researches on dynamic movement simulation of knee joint. OBJECTIVE: A 3D finite element model of normal male knee joint was established to dynamically simulate the movement of knee joint and analyze the biomechanical characteristics and relative movement of the tibio-femoral joint under different flexion angles, so as to provide a 3D finite element model for the investigation of knee biomechanics, and provide basis for the design of personalized knee prosthesis and 3D printing. METHODS: The knee joint from a healthy male adult was scanned by CT. Then, a normal 3D finite element model of knee joint was constructed by Mimics, Hypermesh and Abaqus. Simulation and stress analysis of knee joint were carried out under different loads. RESULTS AND CONCLUSION: (1) The constructed finite element model of knee joint could accurately reflect the geometrical structure and biomechanical characteristics of the knee joint, and could simulate multiple movements of knee joint and was effective for biomechanical research of the knee joint. (2) In the process of simulating knee flexion at 0°-60°, the range of knee valgus angle was 3.34°-6.13°, and the range of internal rotation angle was 1.56°-29.17°. The femur had a significant posterior shift relative to tibia, and the shifted distance was from 4.36 mm to 7.23 mm. (3) At knee flexion 0°, the maximum contact stresses of femur cartilage, tibial cartilage and meniscus were 1.45, 1.03 and 2.59 MPa, respectively, and 6.41, 6.73 and 8.65 MPa, respectively at knee flexion 60°. (4) Our findings indicate that in the process of simulating knee flexion at 0°-60°, the range of knee valgus angle is relatively small, and stable, while the range of internal rotation angle is relatively large. In the process of simulating knee flexion at 0°-60°, the contact stress of femoral and tibial cartilage gradually increased with the varied flexion angle, while the changes of contact stress of medial and lateral menisci are different, the changes of medial meniscus are much great, and the contact stress of lateral meniscus is relatively stable. The contact stress of medial meniscus is greater than that of lateral menisci. [ABSTRACT FROM AUTHOR]

BACKGROUND: The edge load contact caused by joint separation causes great stress concentration and then produces a large amount of wear. The edge contact caused by hip joint separation is a dynamic process of femoral head touching the rim of the acetabulum and sliding into the acetabulum quickly, so a dynamic contact mechanical model is needed. OBJECTIVE: To obtain the dynamic mechanical simulation model of ceramic acetabulum under the edge load contact, so as to provide the contact mechanics foundation for the wear analysis of hip joint under the condition of edge load, and provide theoretical basis for prosthesis design and surgeon operation. METHODS: By using 3D modeling software SolidWorks and dynamic simulation software ADAMS, edge load contact dynamics simulation model of ceramic femoral head and acetabular cup was established to verify the edge load contact deformation by numerical method. The effects of acetabular abduction angle and initial separation distance on edge load contact were analyzed. RESULTS AND CONCLUSION: (1) The contact stiffness coefficient used in the model is reasonable and effective. This model can be used to study the parameters that influence the edge load contact of hip joints. (2) The excessive cup inclination angle and initial separation distance will increase the severity of the edge load. (3) Acetabular cup inclination angle and initial separation distance are two important factors that affect the edge load contact. [ABSTRACT FROM AUTHOR]

BACKGROUND: Unicompartmental knee arthroplasty is an effective treatment for end-stage knee osteoarthritis, and its surgical procedures are relatively standard and uniform. The trauma caused by surgery in different patients is quite similar, but its postoperative recovery rate and degree are not the same. Perioperative sleep disorders have a high incidence in knee arthroplasty; however, there is still a lack of studies on the correlation between preoperative sleep quality and early rehabilitation after unicompartmental knee arthroplasty in China. OBJECTIVE: To investigate the effect of preoperative sleep quality on early rehabilitation after unicompartmental knee arthroplasty. METHODS: A total of 218 patients with knee osteoarthritis who underwent unicompartmental knee arthroplasty in The First Affiliated Hospital of Anhui Medical University from July 2018 to July 2022 were enrolled. Pittsburgh Sleep Quality Index was used to evaluate sleep quality before operation. The study subjects were divided into a high preoperative sleep quality group (Pittsburgh Sleep Quality Index score ≤ 5, n=102) and a low preoperative sleep quality group (Pittsburgh Sleep Quality Index score > 5, n=116) according to the results. The visual analog scale score of pain at 12, 24, 48 and 72 hours after operation, the number of days required for 90° of knee flexion after operation (knee flexed at least 90° without applying external force and without unbearable pain) and the length of postoperative hospital stay were compared between the two groups. The postoperative opioid analgesic use (converted to oral morphine equivalent) was also recorded between the two groups. RESULTS AND CONCLUSION: (1) There was no significant difference in age, height, body mass index, joint side, preoperative knee range of motion, preoperative visual analog scale score, preoperative Hospital for Special Surgery score and preoperative hemoglobin concentration, and albumin concentration between the two groups (P > 0.05). (2) Compared with the low preoperative sleep quality group, the high preoperative sleep quality group had significantly lower postoperative visual analog scale scores at 12, 24, 48, and 72 hours, opioid analgesic use, hemoglobin difference and albumin difference before and after operation, the number of days required for 90° of knee flexion, the length of postoperative hospital stay, and the differences were statistically significant (P < 0.05). (3) The results show that improving preoperative sleep quality is of great significance in improving prognosis, reducing the use of analgesics, improving patient satisfaction, and reducing social burden, and can directly or indirectly accelerate early rehabilitation after unicompartmental knee arthroplasty from multiple aspects and dimensions. [ABSTRACT FROM AUTHOR]

BACKGROUND: The dynamic computational model of artificial hip joints can effectively simulate the dynamic separation of femoral head and acetabular cup and explore edge contact between the head and cup. OBJECTIVE: To study the effect of the femoral head diameter on the edge load under dynamic micro-separation of hip joints, to provide a basis for biomechanical analysis of ceramic hip joints corresponding to early high wear problems caused by edge loading, and provide theoretical analyses for hip prosthesis design and clinical application. METHODS: Using the previously validated method, the dynamic model of artificial hip joint for edge contact based on Adams dynamic simulation software was used to predict dynamic micro-separation and edge contact force in the gait cycle of the hip joint. RESULTS AND CONCLUSION: (1) The maximum contact force of the edge loading under micro-separation of the cup and femoral head slightly reduced as the femoral head size increased. (2) The severity of edge contact was computed as the product of the edge contact force and its acting time. The severity parameter of φ36 mm head was 0.6% larger than that of φ28 mm one. The parameter of diameter 55 mm hip was 2.7% larger than that of φ28 mm and φ36 mm heads. (3) The change of the ceramic hip femoral head size has negligible effect on the edge loading. [ABSTRACT FROM AUTHOR]

BACKGROUND: As a classic surgical method for the treatment of femoral head necrosis and femoral neck fracture, total hip arthroplasty has some problems, such as poor placement of prosthesis, postoperative dislocation and so on. OrthoPilot navigation assisted total hip arthroplasty can theoretically improve the accuracy and safety of prosthesis placement. At present, there are few studies on its application in total hip arthroplasty in China. OBJECTIVE: To explore the feasibility and short-term clinical effect of OrthoPilot navigation assisted total hip arthroplasty. METHODS: A retrospective analysis was performed in 23 patients who received OrthoPilot navigation assisted total hip arthroplasty in the Department of Joint surgery of the First Affiliated Hospital of Anhui Medical University from June 2019 to April 2022. A total of 23 patients with freehand total hip arthroplasty were matched at 1:1 according to sex, age, body mass index and preoperative Harris score. The anteversion and inclination angles during and after operation were measured and counted. The operation time, total blood loss, postoperative drainage, average hemoglobin loss and postoperative Harris scores were calculated. RESULTS AND CONCLUSION: (1) The operation time in the navigation group was (152.4±39.9) minutes and in the non-navigation group was (115.3±35.4) minutes, with statistically significant (P=0.02). (2) In terms of angle measurement, the anteversion angle of acetabular cup was (42.3±3.5)° during operation and (42.6±5.5)° after operation, with no significant difference (P=0.574) in the navigation group. The inclination angle of acetabular cup was (18.5±3.4)° during operation and (19.3±3.9)° after operation, with no significant difference (P=0.567) in the navigation group. (3) According to “Lewinnek safe zone”, 22 hips were in the safety zone and 1 hip outside the safety zone after operation in the navigation group, while 17 hips were in the safety zone and 6 hips outside the safety zone after operation in the non-navigation group, showing a significant difference (χ ² =4.212, P=0.04). (4) In terms of surgical treatment, there was no significant difference in total blood loss, postoperative drainage, average hemoglobin loss, Harris score, and the incidence of postoperative lower extremity deep venous thrombosis between the two groups. (5) The average follow-up was 3 months after operation, and there were no patients with early infection or dislocation in the two groups. (6) These results verify that OrthoPilot navigation assisted total hip arthroplasty can improve the accuracy and safety of acetabular cup placement, and its short-term clinical effect is not significantly different from that of freehand total hip arthroplasty. [ABSTRACT FROM AUTHOR]

BACKGROUND: Intervertebral disc degeneration is one of the most common causes of low back pain. The decrease in the number and dysfunction of endogenous nucleus pulposus-derived mesenchymal stem cells may be an important cause of intervertebral disc degeneration. Icariin within a certain range may reduce the apoptosis of mesenchymal stem cells through the PI3K/Akt signaling pathway. OBJECTIVE: To investigate the mechanisms underlying the effects of icariin on apoptosis of nucleus pulposus-derived mesenchymal stem cells. METHODS: The nucleus pulposus-derived mesenchymal stem cells were isolated from degenerated disc of Sprague-Dawley rats. Nucleus pulposus-derived mesenchymal stem cells of passage 3 were treated with different concentrations of icariin. CCK-8 assay was used to detect cell viability and proliferation. Nucleus pulposus-derived mesenchymal stem cells of passage 3 were divided into control, icariin, and LY294002 groups. The apoptosis was detected by flow cytometry and TUNEL staining at 1 week after treatment. The mRNA and protein expression of Caspase-3, Bcl-2, Bax and PI3K/Akt signaling pathway-related proteins p-Akt and p53 was detected by real-time polymerase chain reaction and western blotting. Sixteen Sprague-Dawley rat intervertebral disc degeneration models were equally divided into icariin (icariin 50 mg/kg per day intragastrically) and control groups (equivalent normal saline intragastrically). X-ray, MRI and hematoxylin-eosin staining were performed to evaluate disc degeneration before, 2 and 4 weeks after treatment. RESULTS AND CONCLUSION: (1) Icariin promoted the proliferation of nucleus pulposus-derived mesenchymal stem cells at a certain concentration range, and the best concentration was 0.1 μmol/L (P < 0.05). (2) The apoptosis rate, the number of TUNEL-positive cells, mRNA and protein expression of Caspase-3, Bax and p53 in the icariin group were significantly decreased compared with the control group, while the expression levels of p-Akt and Bcl-2 were significantly increased (P < 0.05). LY294002 (PI3K/Akt signaling pathway inhibitor) reversed the protective effect of icariin on nucleus pulposus-derived mesenchymal stem cells (P < 0.05). (3) The disc degeneration was delayed after icariin treatment in the animal models. There were significant differences in the Disk Height Index, MRI scores, and hematoxylin and eosin staining scores between the icariin and control groups at 4 weeks (P < 0.05). (4) The results show that icariin can promote the proliferation of nucleus pulposus-derived mesenchymal stem cells in a concentration-dependent manner within a certain concentration range. Furthermore, icariin can inhibit nucleus pulposus-derived mesenchymal stem cell apoptosis by activating PI3K/Akt signaling pathway to delay disc degeneration. [ABSTRACT FROM AUTHOR]

BACKGROUND: A large number of studies focus on the effect of inflammatory factors on human periodontal ligament stem cells; however, there are few reports on the expression of chemokine macrophage inflammatory protein-1α in human periodontal ligament stem cells at home and abroad. OBJECTIVE: To investigate the effects of different mass concentrations of macrophage inflammatory protein 1α on the proliferation, apoptosis, and migration of human periodontal ligament stem cells and the correlation of Notch signaling pathway. METHODS: Healthy orthodontic reduced premolars were extracted from patients aged 12-25 years (all signed informed consent), and human periodontal ligament stem cells were isolated and cultured by tissue block method combined with enzymatic digestion. Passage 3 human periodontal ligament stem cells at logarithmic growth stage were divided into control group, 1, 10, 100 mg/L macrophage inflammatory protein-1α groups. Cell proliferation was detected by CCK8 assay at 1, 3, 5, and 7 days. At 48 hours, the apoptotic ability of each group was detected by flow cytometry. Cell migration ability of each group was detected by Transwell chamber test. ELISA was used to detect the level of secreted tumor necrosis factor α. qRT-PCR and western blot assay were used to detect the mRNA and protein expression levels of Notch1 and Hes1. RESULTS AND CONCLUSION: (1) 1 mg/L macrophage inflammatory protein-1α had no significant effect on the biological behavior of human periodontal ligament stem cells. 10 mg/L macrophage inflammatory protein-1α significantly promoted the proliferation and migration of human periodontal ligament stem cells, and 100 mg/L macrophage inflammatory protein-1α significantly promoted the apoptosis of human periodontal ligament stem cells, inhibited the proliferation and migration of human periodontal ligament stem cells. (2) 1 mg/L macrophage inflammatory protein-1α had no significant effect on the expression of Notch1 and Hes1 proteins in human periodontal ligament stem cells. 10 mg/L macrophage inflammatory protein-1α had no significant effect on the expression of Notch1 protein in human periodontal ligament stem cells, but could down-regulate the expression level of Hes1 protein in the cells. 100 mg/L macrophage inflammatory protein-1α could up-regulate the expression of Notch1 and Hes1 protein in cells. (3) The level of tumor necrosis factor α secreted by human periodontal ligament stem cells of the 1 mg/L macrophage inflammatory protein-1α group was not significantly different from that of the control group. 10 mg/L macrophage inflammatory protein-1α promoted the secretion of tumor necrosis factor α; 100 mg/L macrophage inflammatory protein-1α inhibited the secretion of tumor necrosis factor α. (4) These results exhibited that 10 mg/L macrophage inflammatory protein-1α promoted the proliferation, migration and tumor necrosis factor α secretion of human periodontal ligament stem cells, and the mechanism might be related to the down-regulation of Notch signaling pathway. 100 mg/L macrophage inflammatory protein-1α inhibited the proliferation and migration of human periodontal ligament stem cells and the secretion of tumor necrosis factor α, and promoted the apoptosis of human periodontal ligament stem cells. The mechanism may be related to the upregulation of Notch signaling pathway. [ABSTRACT FROM AUTHOR]

BACKGROUND: The use of vancomycin in total knee arthroplasty is a controversial strategy for the prevention of incisional infection. At present, there is little evidence to evaluate the efficacy of this preventive measure in China. OBJECTIVE: To evaluate the efficacy of local vancomycin in the prevention of early postoperative incision infection during total knee arthroplasty. METHODS: 120 patients with osteoarthritis of the knee who received unilateral total knee arthroplasty for the first time at Department of Joint Surgery of First Affiliated Hospital of Anhui Medical University from March to June 2022 were included in this study. They were randomly divided into the observation group and the control group, with 60 cases in each group. All patients gave informed consent to the treatment plan. In the observation group, 1 g of vancomycin was applied intraoperatively; in the control group, no vancomycin was applied intraoperatively. Erythrocyte sedimentation rate, C-reactive protein, fever rate on seven consecutive days after surgery, degree of knee joint swelling, cumulative drainage volume, and incidence of periprosthetic joint infection were recorded in two groups of patients on days 1, 3, and 5 after surgery so as to evaluate the efficacy of topical vancomycin in total knee arthroplasty for the prevention of incision infection in the early postoperative period. RESULTS AND CONCLUSION: (1) The differences in erythrocyte sedimentation rate and C-reactive protein between the two groups on days 1, 3, and 5 after surgery were not significant (P > 0.05). (2) The difference in fever rate between the two groups for 7 consecutive days after surgery was not significant (P > 0.05). (3) There was no significant difference in the degree of postoperative knee swelling and cumulative drainage flow between the two groups (P > 0.05). (4) The difference in the incidence of periprosthetic joint infection one year after surgery was not significant between the two groups (P > 0.05). (5) The results suggest that the local use of vancomycin in total knee arthroplasty has not shown significant efficacy in preventing incision infection in the early postoperative period. [ABSTRACT FROM AUTHOR]

BACKGROUND: In the treatment of oral implant repair, different occlusal contact methods affect the internal structure of the implant and the stress distribution in the bone tissue. Whether the stress distribution is balanced or not determines the long-term life of the implant and the stability of the surrounding bone level. OBJECTIVE: To explore the effects of different occlusal contact modes on the internal stress distribution of restoration, implant, abutment, retention screw, bone tissue, binder and restoration in three kinds of occlusal relationship of maxillary central incisor implant. METHODS: The cone beam CT image data of one volunteer undergoing implant restoration of the maxillary central incisor were extracted from the database. Mimics 19.0 software was utilized to build the maxillary model, and the maxillary model was imported into Solidworks 2017 software to build the maxillary central incisor crown restoration model. Using ANSYS Workbench 17.0 software, three occlusal contact modes of end-to-end occlusion, normal occlusion, and deep overbite occlusion were loaded by simulating the distal middle edge of the crown, the midpoint of the implant diameter and the midpoint of the joint crown. The stress distribution of each structure and bone tissue in the implant restoration was analyzed under the influence of three kinds of occlusal relationship and three loading modes. RESULTS AND CONCLUSION: (1) In the end-to-end occlusion group, when the contact mode changed from the distal margin to the midpoint of the implant diameter and the midpoint of the crown, the stress of the internal structure, bone tissue and binder of the implant decreased accordingly. (2) In the normal group, when the contact mode changed from the distal margin to the midpoint of the implant diameter and the midpoint of the joint crown, the stress of the internal structure, bone tissue and binder of the implant decreased accordingly. (3) In the deep overbite group, when the contact mode changed from the distal margin to the midpoint of the implant diameter and the midpoint of the crown, the stress of the internal structure and bone tissue of the implant increased accordingly, while the stress of the binder gradually increased. (4) The results show that different occlusal contact modes and occlusal relationship affect the distribution of stress in each structure, bone tissue and binder of implant restoration. This conclusion may provide a reference basis for the adjustment of occlusal contact of implant restoration. [ABSTRACT FROM AUTHOR]

BACKGROUND: There are many studies on the marginal integrity of all ceramic crowns with different resin adhesives, or different shoulder, different polymerization angles, but there is no research on whether different methods of redundant bonding will affect the marginal integrity of all ceramic crowns. OBJECTIVE: To analyze the effect of removing excess resin adhesive on the marginal integrity of all ceramic crowns with different marginal gaps. METHODS: Totally 40 extracted third molars were prepared with all ceramic crowns and randomly divided into groups A, B, C, and D (10 teeth in each group). After the model scanning was completed, the edges of restoration in groups A, B and C were lifted at 30, 60 and 90 µm respectively by computer control, while those in group D were not raised. Procera alumina CAD-CAM all ceramic crowns were made. Then, the four groups of groups A, B, C and D were randomly divided into two subgroups. In one subgroup, a large amount of excess resin adhesive was removed with a small brush, and then the light was illuminated for 40 seconds after the full crown bonding. Subsequently, a small amount of resin adhesive was scraped off with sickle scalpel (small brush group). The sample in the other subgroup was exposed to light for 2 seconds, scraped off with sickle scalpel, and then illuminated for 40 seconds (sickle group). The marginal integrity and surface quality of the adhesive were observed by scanning electron microscope. RESULTS AND CONCLUSION: (1) Scanning electron microscope showed that the continuity of the bonding interface was better in the small brush group. Different degrees of adhesive defects were found in the sickle group. Under the same marginal gap, the defect rate of cement in the small brush group was lower than that in the sickle group (P < 0.05). Under the same adhesive removal method, there was no significant difference in the defect rate of cement between groups A, B, C, and D (P > 0.05). (2) Results indicate that the method of using small brush to remove excess adhesive, then lighting for 40 seconds, and finally using sickle scalpel to remove the remaining small amount of adhesive is more suitable for clinical practice. [ABSTRACT FROM AUTHOR]

BACKGROUND: Hydroxyapatite coating prepared by plasma spraying on titanium alloy surface has many advantages, such as high flame temperature, fast flight speed, little thermal effect of deposited body, good smoothness, mature technology and high automation, but there are also many problems, such as poor mechanical properties, low crystallinity and large residual stress. OBJECTIVE: To investigate the effects of hydrothermal treatment on the characteristics and mechanical properties of hydroxyapatite coatings. METHODS: Hydroxyapatite coatings were prepared on titanium alloys by plasma spraying. The coatings were hydrothermally treated for 2, 4, 6 and 8 hours respectively. The material characteristics of the coatings before and after hydrothermal treatment were analyzed by scanning electron microscopy, X-ray diffraction and energy dispersive spectrometry. The microhardness and elastic modulus of the coatings were also measured. RESULTS AND DISCUSSION: Hydroxyapatite decomposition and amorphous phenomena occurred during spraying process, resulting in crystalline phases such as TCP, TTCP, CaO and a large number of amorphous phases. Hydrothermal treatment can promote the transformation of crystalline and amorphous phases into crystalline hydroxyapatite. After hydrothermal holding at 150 °C for 8 hours, the crystallinity of the coating increased from 6.9% to 93.76%. More voids and cracks were observed after spraying, which increased the specific surface area of the coating and accelerated the dissolution and recrystallization process of hydroxyapatite. Hydrothermal treatment promoted the formation and aggregation of nano-hydroxyapatite microcrystals on the crack surface, which was the fundamental cause for the phenomenon of "self-healing" of some cracks. The Young’s modulus and micro-hardness of the coating after hydrothermal treatment were better than those after spraying. The results indicate that hydrothermal treatment can effectively improve the crystallinity, elastic modulus and microhardness of hydroxyapatite coatings. [ABSTRACT FROM AUTHOR]

BACKGROUND: Geometric parameter of knee prosthesis makes important effect on sport performance and contact force, and decides the service life of knee prosthesis. OBJECTIVE: To analyze the effects of anterior sagittal radius, the posterior sagittal radius and the coronal radius of curvature of the tibial liner of knee prosthesis on the contact mechanics and kinematics of the knee joint. METHODS: The standard model based on the product of total knee arthroplasty DePuy PFC CR posterior cruciate ligament retained prosthesis from Johnson & Johnson’s Orthopaedic Company was applied. The three-dimensional solid model of tibia coronal radius enlargement prosthesis, tibia sagittal radius enlargement prosthesis and tibia coronal posterior radius enlargement prosthesis were established by changing the sagittal anterior radius, sagittal posterior radius and coronal curvature radius of tibial liner of the knee prosthesis. The force-controlled display dynamic gait cycle finite element was built to simulate the gait periodic motion after knee arthroplasty. The results of the maximum contact pressure, contact area, anterior and posterior displacement of tibial and internal and external rotation angle of the tibial pad during one gait cycle were obtained. RESULTS AND CONCLUSION: (1) Compared with the standard model, the contact pressure of the tibial liner was increased significantly and the contact area was decreased obviously. But decreased sagittal conformity would not lead to significant increase in maximum contact pressure and contact area. (2) Compared with the standard model, a distinct tibial backward movement was observed when the anterior curvature radius of the tibial liner increased. A slight tibial backward movement was observed when the sagittal posterior curvature radius increased. The increased anterior and posterior curvature radii of tibial liner led to a significant internal rotation, especially for the standing stage when the maximum rotation angle reached to 10° from 8°. The increase in coronal curvature of the tibial liner showed an unnoticeable impact on the kinematic performance of the prosthesis. (3) These results showed that the conformity of femoral condyle of the knee joint prosthesis and tibial liner in coronal plane is the main geometric parameter affecting the contact area and contact pressure of the tibial liner. Decreasing the coronal conformity properly will not cause a significant impact on the stability of knee joint motion. The consistency of the sagittal curvature radius of the prosthesis is the main geometric parameter affecting knee joint motion. [ABSTRACT FROM AUTHOR]

BACKGROUND: The biomechanical properties of the hip bone are complex in vivo that requires a more efficient and accurate method for the finite element analysis. OBJECTIVE: To develop a musculoskeletal multi-body dynamic model of the patient-specific hip joint after surgery and simulate gait, and to explore the biomechanics of the hip joint. METHODS: CT data of the patient's hip joint postoperatively were collected, three-dimension reconstruction underwent in MIMICS, and materialization and position matched on Geomagic Studio and meshed on Hypermesh. A musculoskeletal multi-body dynamic model of the patient-specific hip joint was established using AnyBody software and simulated the normal movements during walking, then export the muscle force, oint forces, joint moment as the Boundary conditions in finite element analysis. Then, the muscle forces, joint forces and torque were obtained and imported to be the boundary conditions for finite element analysis. The stress and strain values and concentration parts were measured on Abauqus during walking. RESULTS AND CONCLUSION: (1) The maximum value of the joint force in the three directions of the hip joint was 600, 2 000, 100 N at 2.1 seconds. (2) The ilium force was almost only in the Y direction, and the maximum value was 1 000 N. (3) The maximum stress on the hip joint was about 12 MPa at 30% of the gait cycle and the maximum relative displacement was 0.5 mm. (4) To conclude, the stress of the hip after surgery is mainly concentrated on the vicinity of the sacroiliac joint, postersuperior of the acetabulum, middle region of iliac bone, and upper zone of pubic bone; the stress of the hip is higher than that of the normal hip, and the activity intensity should be paid attention during rehabilitation. [ABSTRACT FROM AUTHOR]

BACKGROUND: Vertebroplasty (PVP) and kyphoplasty (PKP) are important methods for the treatment of osteoporotic vertebral compression fractures in the elderly. Although bone cement has certain liquidity and vertebral fractures are often in different situations, bone cement leakage rate is still high. OBJECTIVE: Based on the theoretical discussion and clinical analysis, to study the theoretical causes of bone cement leakage and effective prevention methods. METHODS: A total of 162 cases (186 vertebrae) were treated with three methods of vertebroplasty. Group A: 64 cases with 78 vertebrae were treated with conventional cemented vertebroplasty; Group B: 57 cases with 65 vertebrae were treated with cemented vertebroplasty using cement pump; Group C: 41 cases with 43 vertebrae were treated with balloon kyphoplasty. The leakage of bone cement was observed in three groups. RESULTS AND CONCLUSION: Of the 186 vertebrae, postoperative bone cement leakage occurred in 25 vertebrae, with the leakage rate of 13% (25/186). Group A had bone cement leakage in 11 vertebrae, and the leakage rate was 14% (11/78). Group B had bone cement leakage in 8 vertebrae, and the leakage rate was 12% (8/65). Group C had bone cement leakage in 6 vertebrae, and the leakage rate was 14% (6/43). There was no significant difference among the three groups in the leakage rate of bone cement (P > 0.05). That is to say, the causes of bone cement leakage are not completely controllable, and the leakage position has some randomness. Strict and careful imaging monitoring is an intuitive method to prevent bone cement leakage. [ABSTRACT FROM AUTHOR]

BACKGROUND: A large number of preclinical experimental data have shown that stem cells can regulate the immune function, and serve the function of cell replacement. OBJECTIVE: To summarize the anti-inflammatory effects of stem cells in the treatment of ischemic stroke, based on which, we further discuss the specific mechanisms. METHODS: We conducted a systematic and comprehensive search in PubMed, Elsevier, Springer, Wiley, Ovid, EBSCO databases. The range of retrieval time was from 2012 to 2017. The keywords were “stem cells, stroke, inflammation, immune”. Totally 110 articles were retrieved initially, and 47 articles were included in result analysis. RESULTS AND CONCLUSION: By reading extensive literature, we analyzed and summarized the research status quo of the anti-inflammatory effects of neural stem cells, mesenchymal stem cells and endothelial cells in the treatment of ischemic stroke. The mechanisms mainly include reducing focal inflammation, immune regulation, promoting the secretion of various neurotrophic factors, reducing secondary cell death, protecting neurons and promoting cell function recovery and further promoting the recovery of nerve function. The mechanisms underlying local immune regulation and anti-inflammatory effects of stem cells are mainly described as the shift from M1 to M2 macrophages under the intervention of stem cell factors, to intervene secreted immune cytokine profiles and exert effects on inhibition and polarization of glial cells. Further investigation is required on the anti-inflammatory effects and immune regulation of stem cell therapy for stroke. [ABSTRACT FROM AUTHOR]