Guided bone regeneration technique (GBR) is regarded as one of the most important methods to increase the bone amount of alveolar ridge, which is often recommended to be applied in the dental implantation surgery. Barrier membrane is utilized in GBR technique to cover the bone defect and create a secluded space, which prevents the connective tissue from growing into the space and facilitates the growth priority of bone tissue. In recent years, along with the emerging of different kinds of barrier membranes and bone grafting materials, the scope of clinical application of this technology is continuously expanded. This article reviews the classification and property of the membranes and the application situation of guided bone regeneration technology in the field of dental implantation.

At present,the AIDS epidemic situation in college students is becoming more and more serious.In view of the particularity of colleges students and the lack of professional team for AIDS prevention and control in colleges and universities,there exists ethical issues when carry out the prevention and control for AIDS in colleges and universities such as the ethical issue in publicity and education,the ethical issue in AIDS behavioral intervention,the ethical issue in the consultation and detection for AIDS.This paper suggests that it should confront the current situation of AIDS prevention and control,improve the professional level of carrying out AIDS prevention and control,adhere to the necessary principles of AIDS prevention and control,and explore a new mode to construct AIDS prevention and control in colleges and universities.

BACKGROUND:Autologous bone marrow aspirate concentrate is often applied in patients from Department of Orthopedics and those with severe limb ischemia, but rarely applied in Department of Oral and Maxil ofacial Surgery, especial y in Department of Oral Implantology. The effect of autologous bone marrow aspirate concentrate on promoting peri-implant bone regeneration deserves further studies.
OBJECTIVE:To evaluate the effect of bone marrow aspirate concentrate in the repair of peri-implant bone defect.
METHODS:Bone marrow 5 mL was extracted from posterior superior iliac spine of experimental dogs and bone marrow cel s were counted before and after concentration. Bone defect (4 mm × 4 mm × 4 mm) was prepared in the middle of bilateral mandibular premolar, which was randomly implanted with gelatin sponge plus bone marrow aspirate concentrate, autologous bone and gelatin sponge. At 4 and 12 weeks after surgery, bone defect specimens were histological y observed. The new bone formation rate and new bone mineral density were calculated.
RESULTS AND CONCLUSION:After centrifugation, the concentrations of nucleated cel s in bone marrow aspirate concentrate were increased by (2.78±0.22) times. More colony-forming units were found after cel culture. Histological analysis showed that, significantly higher new bone formation rate and new bone mineral density occurred in gelatin sponge plus bone marrow aspirate concentrate group, compared with autologous bone group and gelatin sponge group at 4 weeks (P<0.05). The new bone formation rate in gelatin sponge plus bone marrow aspirate concentrate group was significantly lower than that of autologous bone group, and higher than that of gelatin sponge group at 12 weeks (P<0.05). However, the difference of new bone mineral density in the three groups was not significant (P>0.05). Autologous bone marrow aspirate concentrate can significantly improve new bone mineral density and quantity in the pre-implant bone defect.

In order to adapt to the development of society,an innovative talent cultivation system has been explored to train stomatological specialists with active innovation spirit and strong ability to practise.

Objective To assess the feasibility and clinical value of high-resolution magnetic resonance imaging (HRMRI) in patients with symptomatic severe intracranial stenosis (SSIS).Methods HRMRl wasperformed with a 3.0 T MR scanner on 5 patients with symptomatic middle cerebral(n=3) or basilar (n=2) arterial stenosis of≥70% confirmed bv DSA.Image diagnosis Was made on the basis of HRMRI findings of vessel wall at the stenotic segment by 2 neuroradiologists blinded t0 patient's status.Results Three of the five patients were diagnosed to have advanced intracranial atherosclerosis based on the presence of a complex eccentric atherosclerotic plaque containing a large lipid-rich necrotic core with a heterogeneous post-contrast enhancement and with signs of ruptured fibrous cap.Two other patients were likely to suffer from non-atherosclerotic lesion.HRMRI revealed an iso-signal septum in the arterial lumen attaching to the slighfly thickened arterial wall that was iso-signal with a homogeneous post-contrast enhancement in one patient and an obviously concentrically thickened arterial wall with hypo-intense signal on T1 WI and slightly high signal on T2 WI and PDWI and without any post-contrast enhancement in the remaining patient.Conclusions In vivo HRMRI in patients with SSIS is technically feasible.It provides detailed information of intracranial arterial wall at the stenotic segment.

BACKGROUND: As a blood concentrate rich in growth factors and fibrin, platelet-rich fibrin (PRF) is able to significantly promote bone regeneration. PRF mixed with bone substitutes is commonly used to repair bone defects in oral maxillofacial region. But it remains controversial whether PRF as a sole material in sinus floor elevation can produce enough new bone tissues.OBJECTIVE: To evaluate the osteogenic potential of PRF as a sole grafting material in sinus floor elevation by means of an animal model.METHODS: Twelve healthy adult mongrel dogs aged 12-18 months were selected and randomized into three groups (groups A, B and C), with four dogs in each group. Upper first molars on both side of each dog were extracted 12 weeks prior to sinus floor elevation and simultaneous implants placement. Different materials were used to fill in the space between the sinus membrane and implant. Groups A, B and C were filled with PRF, autologus bone particles and autologus blood clot respectively. After 12 weeks, specimens were harvested to analyze the new bone formation by gross observation, X-ray examination and histological evaluation.RESULTS AND CONCLUSION: New bone formation was found to embrace all the implants close to the bony sinus floor, and the tips of all implants were free from bone coverage. The new bone height of groups A, B and C were (3.135±0.288),(3.218±0.345), and (1.898±0.157) mm, respectively. The new bone density of groups A, B and C were (65.06±5.88),(75.34±8.18), and (56.92±4.95) g/cm3, respectively. There were significant differences between the new bone height in groups A and C as well as in groups B and C (P < 0.05). Also, significant differences were found between the new bone density in groups A and B, B and C, A and C (P < 0.05). Within the confine of this experiment, it is feasible to use PRF as a sole grafting material in the sinus floor elevation to generate new bone, but the new bone volume is limited.

Objective To observe the changes of the brain function during reading recovery by using functional MRI (fMRI),and to provide the experimental data in elucidating the mechanism on the recovery of reading and language function.Methods fMRI was performed in a native Chinese patient with pure alexia on the 45 th and 130 th day after the onset,respectively.Three kinds of Chinese characters were presented during the scan and the patient was asked to make the judgement weather he could recognize the characters or not.The brain activation maps were acquired after postprocessing,and the activated location and volume were compared between the first and second experiments.Results In both experiments,Broca area,Wernicke area,and the right extrastriate were significantly activated,while the left extrastriate around the lesion was markedly activated only in the second experiment,and the volume of activation in the right extrastriate in the second experiment was about 3 times as large as that in the first experiment.Conclusion The left extrastriate cortex is one of the key areas responsible for reading function in the brain.The recovery of reading function can be compensated in contralateral corresponding cortical area,or it can be the result of reorganization in ipsilateral peri-lesion cortex.Both mechanisms may simultaneously play important roles in reading recovery.

BACKGROUND:Three-dimensional visualization technique has been widely used in clinical treatment. Preoperative visualization technique al ows safe demonstration on the complex spine fracture models, and also prepare screw placement scheme according to three-dimensional model of patients.
OBJECTIVE:To discuss the clinical result of treating short-segment lumbar vertebrae fracture with pedicle screw visualization.
METHODS:A total of 32 patients with lumbar vertebrae fracture were treated with 182 pedicle screws. Before the screw implantation, the structure of bilateral pedicle was observed using Mimics software and the implantation parameters were measured. The operation methods and related complications were told to the patients through the reconstructed three-dimensional images. The satisfaction of the patients, operation time, and the position of pedicle screws by postoperative CT scan were assessed. The percentages of anterior vertebral height and Cobb’s angle were measured before operation, 2 weeks after operation and 8 months after operation.
RESULTS AND CONCLUSION:The excellent satisfaction rate of the patients was 100%, the mean operation time was 185 minutes, and 173 pedicle screws (95.1%) were total y inserted within the pedicle. Al patients were fol owed up for 7-22 months. The results showed that the fracture healed wel . The percent of anterior vertebral height and Cobb’s angle at 2 weeks after operation were significantly decreased compared with them before operation (P<0.05). There were no significant difference about the percent of anterior vertebral height and Cobb’s angle between 2 weeks and 8 months fol ow-up (P>0.05). Single-segment lumbar vertebrae fracture was wel treated by the pedicle screw visualization technique. This method assists to make up preoperation plan, increase the rate of patients’ satisfaction, shorten operation time, and increase the accuracy of pedicle screw insertion.

ObjectiveTo investigate its dynamic characteristics and pathological mechanism on magnatic resonance diffusion weighted imaging (DWI) after chemoembolization in rabbit liver VX-2 tumor model.MethodsForty New Zealand rabbits were included in the study and forty-seven rabbit VX-2 tumor models were raised by implanting directly and intrahepatically after abdominal cavity was opened.Forty VX-2 tumor models from them were divided into four groups.DWI was performed periodically and respectively for each group after chemoembolization.All VX-2 tumor samples of each group were studied by pathology.The distinction of VX-2 tumors on DWI was assessed by their apparent diffusion coefficient (ADC) values.The statistical significance between different time groups,different area groups,or different b-value groups was calculated using SPSS 12.0 software.ResultsWhen b-value was 100 s/mm2,ADC values in the area of VX-2 tumor periphery,VX-2 tumor central,or normal liver parenchyma around tumor became gradually low in sixteen hours after chemoembolization,and were the lowest at sixteenth hour,and then they increased gradually from sixteenth hour to fourty-eighth hour after chemoembolization.The distinction of ADC between different time groups was significant,respectively ( F =7.325,P ＜ 0.01 ; F =2.496,P ＜ 0.05 ; F =6.856,P ＜0.01 ).Cellular edema in the area of VX-2 tumor periphery or normal liver parenchyma around tumor increased quickly in sixteen hours after chemoembolization; however,from sixteenth hour to forty-eighth hour,cellular edema in the area of normal liver parenchyma around tumor decreased gradually and that in the area of VX-2 tumor periphery decreased lightly at first and then increased continually.Cellular necrosis in the area of VX-2 tumor periphery after chemoembolization was more significant than that before chemoembolization.The areas of dead cells in VX-2 tumors manifested low signal and high ADC value while the areas of viable cells manifested high signal and low ADC value.ConclusionsDWI is able to detect and discriminate tumor necrotic areas from viable cellular areas before and after chemoembolization.ADC of normal liver parenchyma and VX-2 tumor are influenced by intracellular edema,tissue cellular death,and microcirculation disturbance after chemoembolization.

Objective To investigate dynamically characteristics of apparent diffusion coefficient (ADC) of MR diffusion-weighted imaging (DWI) in the rabbit VX-2 tumor model.Methods Forty New Zealand rabbits were included in the study and forty-seven rabbit VX-2 tumor models were raised by implanting directly and intrahepatically after abdominal cavity was opened.DWI was carried out periodically and respectively on seventh,fourteenth,and twenty-first day after implantation.Part samples of VX-2 tumors were studied by pathology.The distinction of VX-2 tumors on DWI was assessed by their ADC values.The statistical significance between different time groups,different area groups,or different b-value groups was calculated using SPSS12.0 software,respectively.Results ADC values of 47 VX-2 tumors in the area of tumor periphery,tumor center,and normal parenchyma around tumor were greater when b-value was 100 s/mm2 than those when b-value was 300 s/mm2 and the distinction of VX-2 tumor ADC in the area of tumor periphery,tumor center,and normal parenchyma around tumor between different b-value groups was significant,respectively( F =17.964,P ＜0.01 ; F =13.986,P ＜0.01 ; F =128.681,P ＜0.01 ).The ADC values in the area of normal liver parenchyma around tumor were greater than those in the area of VX-2 tumor periphery and tumor center when the b-value was 100 or 300 s/mm2.When b-value was the same( 100 or 300 s/mm2),the distinction of VX-2 tumor ADC between different areas was significant( F =176.586,P ＜0.01 ; F =55.089,P ＜0.01 ).The ADC of VX-2 tumor in the area of tumor periphery and tumor center became gradually low from seventh to fourteenth or twenty-first day after implantation and the distinction of ADC between different time groups but the area same (?) was significant( b =100 s/mm2,F =48.211,P ＜0.01 ;b =300 s/mm2,F =20.955,P ＜0.01 ).There were not obvious cellular necrosis in VX-2 tumors on seventh and fourteenth day after implantation but ADC of VX-2 tumor decreased unobviously because of cellular edemata in or around tumors.There were obvious cellular necrotic areas in VX-2 tumors on the twenty-first day after implantation.ADC of viable tumor cells in VX-2 tumors were lower on DWI than that in the area of normal liver parenchyma around tumor and ADC of dead tumor cells in VX-2 tumors were unequal,including high values,equal values,and low values but they were higher than that in the area of normal liver parenchyma around tumor after dead tumor cells had been liquified or had become cystic.Conclusions ADC is able to reflect objectively the diffusion of water molecules in the tumor and to reflect indirectly the degree of the growth and liquified necrosis of a tumor.ADC has an important and potential value in monitoring dynamical tumor growth and in evaluating malignant degree and therapeutic effect.