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BACKGROUND:Three-dimensional finite element has been widely used in the oral cavity field, but little is reported on the three-dimensional finite element reconstruction of the mandibular body using titanium plate. OBJECTIVE:To study the biomechanical characteristics of reconstructing the mandibular body using titanium plate. METHODS:We established a three-dimensional finite element model of mandibular body defect undergoing reconstruction using bicortical titanium screws and titanium plate. Under the simulated normal occlusion state, a 200 N vertical load was added to the central fossa of the occlusal surface of the right mandible first molar. Then, stress distribution and maximum displacement of the mandible, titanium screw, and titanium plate were analyzed. RESULTS AND CONCLUSION:Under the simulated normal occlusion state, mandible stress was concentrated in the mandibular body and mandibular branch, especial y in the anterior and posterior edges of the mandibular branch and the lower edge of the mandible. The stress in the posterior edge of the mandible was lower than that in the anterior edge of the mandible, and moreover, the contact site between the titanium plate and the mandible also presented a concentration of stress. The maximum stress of the bicortical titanium screws appeared near the screw cap, and the stress was also concentrated at the contact site between the titanium screw and the titanium plate. The maximum stress of the titanium screw at the ascending branch of the mandible was higher than that of the titanium screw at the anterior end of the defect. For the titanium plate, the stress was mainly concentrated at the fixed site of the titanium screws;the peak stress of the anterior and posterior edges of the titanium plate was found at the contact site between the anterior end of mandibular defect and the titanium stress as wel as between the ascending branch of the mandible and the titanium screw. After mandibular body reconstruction using the titanium plate, a displacement was likely to occur at the contact site between the anterior end of mandibular defect and the titanium plate. In conclusion, these findings indicate that mandibular body reconstruction using bicortical titanium screws and titanium plate is relatively stable, but the titanium plate fixed at the anterior part of the mandibular angle is prone to breakage.
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BACKGROUND:The nervous reconstruction and repair after spinal cord injury have become a research hotspot. OBJECTIVE:To investigate the change rule of neurogliocyte reactive hyperplasia after spinal cord injury. METHODS:Forty-two adult male Sprague-Dawley rats were selected and equivalently randomized into seven groups:normal control group (no intervention), sham operation group (lamina decompression) and operation groups (postoperative 1, 7, 14, 21 and 28 days). After the establishment of spinal cord injury models, the rats were sacrificed at each corresponding time point. The functional recovery of the rat hind limbs was evaluated by Basso, Beattie and Bresnahan scores, and complete spinal cord tissue was removed to undergo hematoxylin-eosin staining, immunohistochemistry staining and immunofluorescence staining. RESULTS AND CONCLUSION:(1) Basso, Beattie and Bresnahan scores showed that rats in the normal control and sham operation groups had normal neurologic function. Rats at 1 day after spinal cord injury paralyzed completely, the neurologic function of hind limbs began to recover gradual y at the 7th day, and the recovery became most obvious at the 14th day, which had no significant differences compared with the 21st and 28th days. (2) Hematoxylin-eosin staining found that the diffuse hemorrhage and neuronal necrosis were observed in the injured area at 1 day after operation;inflammatory cel infiltration and some vacuoles appeared at the 7th day, and the hemorrhage was absorbed gradual y;the hemorrhage disappeared completely and capsule cavity formed at the 14th day;up to the 28th day, spinal cord structure was completely destroyed and that was replaced by cicatricial tissue accompanying with a large cavity. (3) Immunohistochemistry staining showed that the astrocyte in damaged area proliferated with the cel synapse increasing, which was most overt at the14th day;the axon clearance widened and the structure was in disorder at the 7th day, and the myelin sheath in the damaged area was destroyed at the 21st day. (4) Immunofluorescence staining showed that there were numerous visible glial fibril ary acidic protein+/nestin+cel s in the injured area at 14 days after operation. (5) These results suggest that glial cel hyperplasia and hypertrophy, the up-regulated expressions of glial fibril ary acidic protein and nest protein are advantageous to the early repair of spinal cord injury.
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BACKGROUND: In clinic,the mechanical study about fibula reconstruction for the repair of mandibular bone defect is unrealistic; the finite element analysis, however, provides a new approach for the biomechanical study of mandibular reconstruction. OBJECTIVE: To establish the three-dimensional finite element model of mandibular body defect under fibula reconstruction and smal titanium plate fixation, and to analyze the biomechanical features. METHODS:The three-dimensional model of mandibular body defect under fibula reconstruction and internal fixation was established. 100 N bite force was loaded on the anterior teeth, contralateral first molar and contralateral second molar, respectively. The maximum stress and maximum displacement before and after model reconstruction, the stress of bone tissues around the titanium plate and titanium screw holes under anterior and posterior loading, and the maximum displacement of the front and rear ends of the fibula under anterior and posterior loading were observed. RESULTS AND CONCLUSION:The maximum stress of the normal mandible concentrated in the condylar neck. In the reconstructed models, the maximum stress concentrated in the contralateral condylar neck. Under the same bite force, the maximum stress value of the reconstructed mandibular model was greater than that of the normal mandible. The maximum stress value of the anterior teeth was greater than that of the posterior teeth. The stress value was maximal between two screw holes inside each titanium plate and almost concentrated in the mandibular angle. The maximum stress of the residual titanium screw of the mandible concentrated in the first titanium screw over the mandibular defect under loading, while the maximum stress of the titanium screw of the fibular end concentrated in the titanium screw below the mesial segment of the fibula. The cortical bone around the screw holes located at the residual end of the mandible near the defect area and the upper plate of the mesial segment of the fibula was the maximum stress concentrated site, and the maximum stress of anterior tooth loading was greater than that of the posterior tooth loading. The displacement values of the fibula gradualy reduced from the upper edge to the lower edge in the X-axis, from the anterior and posterior ends to the middle part in the Y-axis, as wel as from the anterior end to the posterior end in the Z-axis. The maximum displacement values of the anterior and posterior ends of the fibula were at the Z-axis and Y-axis, respectively. The maximum displacement value under anterior tooth loading was greater than that under posterior tooth loading. These results show that the titanium plate over the mandibular angle that is most easy to break should be reinforced. If the stress of titanium screw tip and neck is relatively large, double cortical titanium screw is preferred; if the stress of titanium screw and titanium plate at the fibula end and residual end of the mandible is relatively large, we should pay attention to their stability and fixation; if the stress of anterior tooth occlusion is greater than that of posterior tooth occlusion, anterior tooth occlusion should be avoided after repair.
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The nasal deformity secondary to cleft lip of 1 0 patients was repaired with lateral segment of partial costal cartilage harvested by a self-made special knife.6 to 30-month follow-up showed that nasal alar morphology of all patients was improved.No any complications happened at donor site.
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Objective: To develop a Chinese version of the Schedule for the Deficit Syndrome(SDS) and examine its reliability and validity. Methods: 123 schizophrenic patients finished the Chinese version of SDS and were subtyped into deficit (n=30) and nondeficit(n=93) groups. In addition, all patients completed BPRS, SANS and SAPS. The reliability analysis of SDS included Cronbach's ?琢 coefficients and mean inter-item correlations and the inter-rater reliability; while the validity analysis included construct validity and criteria validity. Results: The Cronbach's ?琢 coefficient and the mean interitem correlation coefficients of the negative symptoms severity subscale of SDS were 0.8441 and 0.4818, respectively. The inter-rater reliability for categorization was 0.8777. The correlation coefficients of the six negative symptom items with the total score ranged from 0.685 to 0.875,and that among the six negative symptom items ranged from 0.437 to 0.794. The negative symptom items and the total score of SDS were significantly correlated with the anergia factor score from the BPRS and the total score and several subscale scores of SANS, while none of them was correlated with subscale scores and total score of SAPS. Conclusion: The Chinese version of SDS was a reliable and valid measure for the diagnostic classification of deficit and nondeficit schizophrenia.