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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: 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]

Based on the low-concentration fine tailings obtained from the classification of certain gold ores in Shandong Province, the effective thickening of the tailings was carried out by flocculation and sedimentation process. The effect of flocculant dosage on the sedimentation characteristics of the fine tailings was investigated. At the same time, the pipeline transportation properties of cemented slurry of fine tailings with different concentrations were studied with the help of the Buckingham equation. Test results showed that the addition of flocculant significantly promoted the sedimentation of fine tailings. When the dosage of the flocculant was 60 g/t, the sedimentation rate of fine tailings reached 8.80 cm/min. The measurement of rheological parameters of cemented slurry and the calculation of pipeline transportation resistance provided an important basis for the concentration control of cemented slurry and its smooth transportation in the filling pipeline. [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]

Objective To investigate the effect of active vitamin D on bone metabolism and disease activity in ankylosing spondylitis ( AS) patients with low bone mineral density ( BMD) ． Methods Sixty AS patients with low BMD and 20 healthy controls were selected． Bone specific alkaline phosphatase ( BALP) ，tartrate resistant acid phosphatase-5b ( TＲACP-5b) ，and 25-( OH) D3 were compared between the two groups． The 60 AS patients were randomly divided into the control group ( 30 cases) and the treatment group ( 30 cases) ． The patients in the control group received meloxicam，sulfasalazine，and calcium carbonate． The patients in the treatment group received additional calcitriol． The serum levels of BALP，TＲACP-5b，and 25-( 0H) D3，BMD，erythrocyte sedimentation rate ( ESＲ)，and C reactive protein ( CＲP) were compared between the two groups． Ｒesults The serum levels of BALP and TＲACP-5b in AS group were significant higher than those in healthy control group (P ＜ 0.05) ，and the serum level of 25-( 0H) D3 was significant lower than that in healthy control group (P ＜ 0.05)． The serum levels of BALP and 25-( OH) D3 increased significantly bone in the control group and the treatment group (P ＜ 0.05) ，while the serums levels of TＲACP-5b decreased ( P ＜ 0.05)． The differences of BALP and 25-( OH) D3 before and after the treatment in treatment group were higher than those in the control group (P ＜ 0.05)． BMD of the lumbar spine，great trochanter，and intertrochanteric increased more significantly in treatment group than those in the control group after 6 months (P ＜ 0.05)，and BMD recovered to normal in 5 cases． The change of BMD in the control group was not obvious after the treatment (P ＜ 0.05)． The levels of ESＲ，CＲP，and BASDAI scores decreased in both groups ( P ＜ 0. 05) ． The decreased level of ESＲ score in the treatment group was more obvious than that in the control group ( P ＜ 0. 05) ． Conclusion Active vitamin D improves the bone metabolism and reduce the disease activities in AS patients with low bone mineral density． [ABSTRACT FROM AUTHOR]