OBJECTIVES: This study aims to analyze the biomechanics of three kinds of rigid internal fixation methods for condylar head fractures. METHODS: A three dimensional finite element model of the normal mandible was constructed. It was then used to prepare condylar head fracture finite element model and three kinds of rigid internal fixation finite element model (unilateral tension screw, bilateral tension screw, tension screw+titanium plate). The mechanical characteristics and changes of the mandible condyle under the same mechanical conditions were compared among the three different rigid internal fixation methods. RESULTS: The maximum equivalent stress and displacement of the non-free end of condyle under the rigid internal fixation method of unilateral tension screw were 71.03 MPa and 4.72 mm, respectively. The maximum equivalent stress and displacement of the free end of condyle were 78.45 MPa and 4.50 mm, respectively. The maximum stress of fracture suture was 3.27 MPa. The maximum equivalent stress and displacement of the non-free end of condyle under the rigid internal fixation method of bilateral tension screw were 70.52 MPa and 4.00 mm, respectively. The maximum equivalent stress and displacement of the free end of condyle were 72.49 MPa and 3.85 mm, respectively. The maximum stress of fracture suture was 2.33 MPa. The maximum equivalent stress and maximum displacement of the non-free end of condyle under the rigid internal fixation method of tension screw+titanium plate were 67.26 MPa and 2.66 mm, respectively. The maximum equivalent stress and maximum displacement of the free end of condyle were 69.66 MPa and 2.50 mm, respectively. The maximum stress of fracture suture was 2.18 MPa. CONCLUSIONS The tension screw+titanium plate rigid internal fixation method is the most conducive to biomechanical distribution for condylar head fractures.
Fracture Fixation, Internal/instrumentation* ; Mandibular Condyle/surgery* ; Biomechanical Phenomena ; Bone Screws ; Finite Element Analysis ; Humans ; Mandibular Fractures/surgery* ; Bone Plates ; Titanium ; Stress, Mechanical

Objective: To study the different expression of 4 microRNA (miRNA, miR) during the osteogenesis differentiation of bone marrow mesenchymal stem cell (BMSC) cultured in high-fat or normal environment and to explore the relationship of these miRNAs with disheveled 2 during osteogenesis differentiation. Methods: BMSC were cultured with 2 ml normal osteogenic induction (control group) and high-fat osteogenic induction (high-fat group) respectively. On the 3rd, 5th, 7th,14th, 21st day, quantitative real-time PCR (qPCR) was used to analyze expression levels of four miRNAs (miR-21-5p, miR-29c-3p, miR-138-5p and miR-351-5p), mRNA of disheveled 2, osteogenic related factors such as alkaline phosphatase (ALP), Runt-related transcription gene 2 (Runx2). And the protein was detected by Western blotting. After BMSC were transfected by 50 μl 50 nmol/L miRNA mimics/inhibitors/negative controls respectively, BMSC were put on osteogenic induction, on the 1st, 3rd, 5th, 7th day, ALP activity was detected. On the 7th day, ALP staining was to observe the degree of osteogenesis differentiation, and Western blotting was adopted to analyze the expression of dishevelled 2 and other osteogenic related factors, while qPCR was used to analyze the expression of disheveled 2 mRNA. After 293T cells were co-transfected with disheveled 2 wild-type/mutant firefly luciferase reporter plasmid with either negative control (NC) or a mimic of these four miRNAs respectively for 48 h, luciferase activities were measured. Results: On the 21th day, the expressions of miR-21-5p, miR-29c-3p, miR-138-5p and miR-351-5p in high-fat groups were higher by 20%, 60%, 340% and 4 420% respectively than those in control groups (P<0.05). The expression of ALP and Runx2 in BMSC decreased after BMSC transfected miR-21-5p and miR-29c-3p mimics, while increased after transfected miR-21-5p and miR-29c-3p inhibitors. The expression of disheveled 2 decreased by 35% after transfected by miR-29c-3p mimic, while it increased by 269% after transfected by miR-29c-3p inhibitor (P<0.05). Transfection of the miR-29c-3p mimics significantly decreased the luciferase activity of wild-type 3'-UTR compared with NC control (P<0.05). There were no statistical significances among other groups. Conclusions miRNAs had better expression during osteogenesis differentiation of BMSC in high-fat environment; miR-29c-3p could negatively regulate the osteogenesis differentiation of BMSC by targets on dishevelled 2.