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The theory of cancer stem cells (CSCs) provides a new perspective for the study of cancer. CSCs doctrine presumes that tumor cells are heterogeneity, and there are cancer stem-like cells in tumors, whose proliferation is uncon-trolled. The cancer stem-like cells could form tumors from only few cells, who only account for a very small part of all the tu-mor cells. These cells with stem cells characteristics could form different extend of differentiation of tumor cells and work as source of tumor growth, recurrence and metastasis. miRNAs are widely-existed non-coding small RNAs, which regulate 1/3 of all human genes and participate in a series of essential processes of life. More and more evidences indicate that miRNAs contribute significantly to cancer generation and development. They may exhibit oncogenic activity and act as tumor suppres-sors. As one of the post-transcriptional controlling factors, they regulate biological processes of tumor related genes exten-sively and specific miRNAs expression profiles were shown in different cancers. The research of miRNA about CSCs has be-come very hot. Some studies have confirmed that miRNAs play a very important role in a variety of CSCs, which act as a new target for tumor therapy. Researchers have found that some specific miRNAs express in plasma of cancer patients, which can be used as tumor markers to assist diagnosis and prognosis. This review focused on current progress of research in function of miRNAs in CSCs and its role as tumor markers.
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Objective To biomechanically study the fixation stability of different numbers and shapes of the titanium miniplates (L-shaped and straight four-hole miniplates) in the treatment of maxillary LeFortⅠ fracture by using three-dimensional finite element method so as to provide reference for clinical treatment of the fractures. Methods Three-dimensional finite element model of maxillary LeFortⅠ fracture was established with four kinds of rigid internal fixation (RIF) methods to calculate the stress of the maxilla and the RIF as well as the displacement of the fracture segment under three kinds of occlusion.Then, the fixation stability of different methods was compared. Results Under the same occlusion condition, the decreasing order of the displacement of the fracture segment was the L-shaped plate fixation at both buttress of the maxillary and nasal maxillary zygomatic, the straight four-hole miniplates fixation at both buttress of the maxillary and nasal maxillary zygomatic, the L-shaped plate fixation at the zygomatic maxillary buttress and the L-shaped plate fixation at naso-maxillary buttress. Under the same fixation method, the decreasing order of the displacement of the fracture segment was molar occlusion, premolar oeclusion and incisor occlusion. Conclusions The fixation stability of the L-shaped plate fixation is better than the straight four-hole miniplate fixation for the treatment of LeFortⅠ fracture. Fixation at the zygomaticmaxillary buttress is better than at the naso-maxillary buttress. Use of only two miniplates to fix the LeFort Ⅰ fracture may not be stable. Molar occlusion is not good for fracture healing.
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Objective To investigate the appropriate surgical approaches and microsurgical resection of communicative skull base chordoma. Methods Twenty two cases of communicative skull base chordomas were microsurgically treated from 1995 to 2005 and followed up. The tumors were removed with extended anterior skull base approach in eight cases, with modified Weber-Ferguson (transmaxillary) approach in eight cases, and with transmandibular approach in six cases. Some cases were resected with combined approaches including pterional approach in 3 eases, subtemporal-zygomatie approach in 1 case, and suboccipital-retromastoid approach in 2 cases. Results Total, subtotal and partial removal of the tumors were achieved in 10 cases, 7 and 5 cases respectively. No patients died and had severe nervous system dysfunction after surgery. However, one had CSF rhinorrhea, one with infection, three with cranial never dysfunction. Twenty patients were followed-up with average 3.4 years, 12 returned to normal or partial works, 5 took care by oneself, 1 needed help, 2 died from tumor recurrence. Conclusion The treatment of communicative skull base chordoma is a challenge to neurosurgeon. The key point is the total removal of the tumor with the microsurgical technique and the appropriate approach depend on the location of the tumor. Moreover, skull base reconstruction is also important to avoid the cerebrospinal fluid leak and infection.
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Objective:To study the stress distribution dur i ng clenching and rigid internal fixation(RIF)of mandibular symphysis fracture. Methods:ANSYS software was used to establish the models of mandi bular symphysis fracture and the fracture treatment treat with RIF.The stress di stribution of mandibular symphysis fracture under different conditions were then analysed during different period of bone healthing. The value of stress shieldi ng rate was used to represent the level of stress shielding effects.Resu lts:The stress shielding rate decreased with the progression of fracture healing.The stress shielding rate produced by double plates fixation was higher than that by single plate.Stress shielding rate in the mandible fixed with tita nium plate was lower than that with steel plate.Conclusion:Minip late rigid internal fixation system may produce stress shielding effects when it is used to treat mandibular symphysis fractures. Stress shielding effects are a ffected by the attribute, the shape and the position of the plate.
ABSTRACT
Objective: To study the mandibular bilateral sagittal split ramus osteotomy (BSSRO) with bicortical screws rigid internal fixation(RIF) with the three-dimensional finite element method, and supply directions for clinic practice.Methods:CT scanned technology and the finite element software (Ansys) were used to establish the three-dimensional finite element model of BSSRO with bicortical screws RIF. The stress distribution of the mandible and the RIF and the displacement of split mandible were calculated under three kind of occlusion situation.Results:Under the same kind of occlusion situation, the stress and displacement of the split mandible with single upper screws fixation was higher than that with the reverse "L" screws fixation, the stress and displacement of the split mandible with 2.0 mm diameter screws fixation was higher than that with 2.7 mm diameter screws fixation. With the same kind of fixation method, the stress and the displacemen of the mandible under the incisor occlusion was the highest.Conclusion:The fixation distance, position, distribution angle of the bicortical screws all have effects on the fixation stability. The patient should avoid the incisor occlusion after the surgery.