[Analysis of human mandible and temporomandibular joint using three-dimensional finite element method under different mechanical models].

OBJECTIVE: Analysis the result of human mandible and temporomandibular joint using two different three-dimensional finite element method under different mechanical models. METHODS: The 3-dimensional model including cortical and cancellous bone for human mandible was obtained through computed tomography (CT) scan. Then the model was meshed in the software ICEM CFD. The passive and active muscle-force loadings were separately applied on the FE model to simulate the anterior clenching. Stress distributions in two models were compared. RESULTS: The stress distributions of two models were apparently different. In the passive muscle-force model, high stress was mainly distributed in mandibular angle, retromolar trigone, notch and bite point on crown. In the active muscle-force model, high stress was mainly distributed in condylar vertex and neck, mandibular angle, retromolar trigone and bite point on crown. There were some similarities between passive and active muscle loadings. However, large difference existed in condylar region due to the vertices reaction force disparity. CONCLUSION: Closer to actual stressing state of human mandible and temporomandibular joint, the active muscle-force model is a proper biomechanical model for human mandible under anterior clenching.

[Effect of human silicotic alveolar macrophages on expression of matrix metalloproteinase, tissue inhibitor of metalloproteinase and collagen in human lung fibroblasts].

OBJECTIVE: To study the effect of culture supernatant of alveolar macrophage alveolar macrophages (AM) stimulated by SiO2 on the expression of matrix metalloproteinases (MMP-1), tissue inhibitor of metalloproteinase-1 (TIMP-1) and collagen of fibroblast human embryonic lung fibroblasts (HELF) in the development of silicosis fibrosis. METHODS: AMs were collected from a silicotic patient by bronchoalveolar lavage and exposed to SiO2, cultured human embryo lung fibroblast were allocated into a treated group, a control group, a positive group, and a blank group. HELF was incubated with the cultured supernatant of AMs for 6, 12, 18, 24, 36, 48 h. Immunocytochemical and Western blot technology were used to detect MMP-1 and TIMP-1 expressions in HELF and collagen expression in supernatant of HELF respectively. RESULTS: The supernatant of AM exposed to SiO2 significantly decreased the expressions of MMP-1 (0.0605 +/- 0.0201, 0.0519 +/- 0.0117, 0.0412 +/- 0.0105 and 0.0213 +/- 0.0106 in the treated group at 18, 24, 36 and 48 h) compared with the control group and the blank group (P < 0.05, P < 0.01) but stimulated expressions of TIMP-1 and collagen (P < 0.05, P < 0.01). The ratio of TIMP-1 to MMP-1 increased. The ratio of TIMP-1 to MMP-1 was positively correlated with the expression of collagen III (r = 0.88, P < 0.01). CONCLUSION: Through AM mediation SiO2 can accelerate the expression of TIMP-1 and collagen, and inhibit the expression of MMP-1. The imbalance between the expression of TIMP-1 and that of MMP-1 is related with the abnormal increase in collagen III.

Low-magnitude high-frequency loading, by whole-body vibration, accelerates early implant osseointegration in ovariectomized rats.

Osteoporosis deteriorates jaw bone quality and may compromise early implant osseointegration and early implant loading. The influence of low­magnitude, high­frequency (LMHF) vibration on peri­implant bone healing and implant integration in osteoporotic bones remains poorly understood. LMHF loading via whole­body vibration (WBV) for 8 weeks has previously been demonstrated to significantly enhance bone­to­implant contact, peri­implant bone fraction and implant mechanical properties in osteoporotic rats. In the present study, LMHF loading by WBV was performed in osteoporotic rats, with a loading duration of 4 weeks during the early stages of bone healing. The results indicated that 4­week LMHF loading by WBV partly reversed the negative effects of osteoporosis and accelerated early peri­implant osseointegration in ovariectomized rats.

[Expression and clinic pathological significance of survivin mRNA and protein in salivary gland tumors].

PURPOSE: The study is aimed to determine the expression of survivin mRNA in salivary gland tumors and its significance in the development and progress of salivary gland tumors. METHODS: The expression of survivin mRNA both in benign and malignant salivary gland tumor tissues and in peripheral tissues was identified by in situ hybridizations assay with the prepared tissue chips. The data were analyzed by Chi-square test and rank sum test using SPSS10.0 software package. RESULTS: The difference in the expression of survivin mRNA was significant between benign and malignant salivary gland tumors (P<0.05). But not significant between the gland tissues around the tumors and malignant tumors (P>0.05). The difference in the expression of survivin mRNA in malignant salivary gland tumor was significant in the pathological grade, lymph node status and relapse of the tumor (P<0.05), but not significant in gender, age of the patients and size of the tumors (P>0.05). CONCLUSIONS: The expression of survivin mRNA is associated with clinic pathological characteristics of the malignant salivary gland tumors. Survivin mRNA may play a crucial role in earlier diagnosis and prognosis of the malignant salivary gland tumors.

[Clinical experience of treatment of 275 mandible fractures].

OBJECTIVE: To evaluate the treatment effect of mandible fractures. METHODS: Clinical data of 275 mandibular fracture patients of Tongchuan people's hospital were analysed. RESULTS: (1) The systemic health of 27 non-surgery cases were influenced during the intermaxillary ligation and 3 cases of them had deformity of maxillofacial region. (2) In the surgery group, 5 of 73 cases fixed by steel wire had disorder of occlusion, 6 of 169 cases fixed by titanium mini plate accepted secondary operation of removing the plates, and 6 cases fixed by bioabsorbable mini plate had better effect. CONCLUSION: The internal rigid fixation is an appropriate and effective method for the mandible fractures.