[Influence of bilateral coronoidectomy on temporomandibular joint stress distribution after costochondral graft reconstruction: a finite element analysis].

PURPOSE: To explore the effect of bilateral coronoidectomy on stress distribution after reconstruction of temporomandibular joint (TMJ) by costochondral graft. METHODS: Ten groups of models were established to simulate costochondral graft reconstruction with simultaneously different distances (0, 2, 4, 6, 8 mm) of mandibular advancement, with or without coronoidectomy. Force and stress distribution in the rib-cartilage area were analyzed by finite element analysis. RESULTS: In the process of bilateral joint reconstruction with simultaneously mandible advancement ranging from 0 mm to 8 mm, when the coronoid processes were retained, the forward deformation of the cartilage occurred and the shear force decreased in turn, from 113.2 N to 26.7 N on the left side and from 133.7 N to 1.9 N on the right side. When the coronoid processes were removed, the cartilage deformed backward and the shear force increased successively, from 94.6 N to 188.5 N on the left and 70.1 N to 157.7 N on the right. The stress in the neck was obviously concentrated when mandible advanced 8 mm. CONCLUSIONS: Coronoidectomy has an important impact on stress distribution in the TMJ area, and keeping the coronoid process is beneficial to maintain the mechanical balance. Bilateral CCG reconstruction with coronoidectomy for lengthy mandible advancement (≥ 8 mm) may lead to prominent increase in shear force beyond CCG resistance, resulting in a costal-cartilage junction fracture.

Overcoming chemotherapy resistance using pH-sensitive hollow MnO2 nanoshells that target the hypoxic tumor microenvironment of metastasized oral squamous cell carcinoma.

BACKGROUND: Smart nanoscale drug delivery systems that target acidic tumor microenvironments (TME) could offer controlled release of drugs and modulate the hypoxic TME to enhance cancer therapy. The majority of previously reported MnO2 nanostructures are nanoparticles, nanosheets, or nanocomposites incorporated with other types of nanoparticles, which may not offer the most effective method for drug loading or for the controlled release of therapeutic payloads. Previous studies have designed MnO2 nanoshells that achieve tumor-specific and enhanced combination therapy for localized advanced cancer. However, the therapeutic effect of MnO2 nanoshells on metastatic cancer is still uncertain. RESULT: Here, intelligent "theranostic" platforms were synthesized based on hollow mesoporous MnO2 (H-MnO2) nanoshells that were loaded with chemotherapy agents docetaxel and cisplatin (TP) to form H-MnO2-PEG/TP nanoshells, which were designed to alleviate tumor hypoxia, attenuate angiogenesis, trigger the dissolution of Mn2+, and synergize the efficacy of first-class anticancer chemotherapy. The obtained H-MnO2-PEG/TP nanoshells decomposed in the acidic TME, releasing the loaded drugs (TP) and simultaneously attenuated tumor hypoxia and hypoxia-inducible factor-1α (HIF-1α) expression by inducing endogenous tumor hydrogen peroxide (H2O2) decomposition. In vitro experiments showed that compared with the control group, the proliferation, colony formation and migration ability of CAL27 and SCC7 cells were significantly reduced in H-MnO2-PEG/TP group, while cell apoptosis was enhanced, and the expression of hypoxia-inducible factor-1α(HIF-1α) was down-regulated. In vivo experiments showed that tumor to normal organ uptake ratio (T/N ratio) of mice in H-MnO2-PEG/TP group was significantly higher than that in TP group alone (without the nanoparticle), and tumor growth was partially delayed. In the H-MnO2-PEG/TP treatment group, HE staining showed that most of the tumor cells were severely damaged, and TUNEL assay showed cell apoptosis was up-regulated. He staining of renal and liver sections showed no obvious fibrosis, necrosis or hypertrophy, indicating good biosafety. Fluorescence staining showed that HIF-1α expression was decreased, suggesting that the accumulation of MnO2 in the tumor caused the decomposition of H2O2 into O2 and alleviated the hypoxia of the tumor. CONCLUSION: In conclusion, a remarkable in vivo and in vitro synergistic therapeutic effect is achieved through the combination of TP chemotherapy, which simultaneously triggered a series of antiangiogenic and oxidative antitumor reactions.

Changes of the condylar position after modified disk repositioning: A retrospective study based on magnetic resonance imaging.

OBJECTIVE: This study aimed to explain the malocclusion resulting from the changes in condylar position after unilateral open disk repositioning surgery. STUDY DESIGN: Patients treated with unilaterally modified temporomandibular joint disk repositioning were reviewed. All patients underwent magnetic resonance imaging (MRI) before and immediately after surgery. Occlusion was checked, and the changes in the joint space and condylar position were measured by using MRI. The paired t test was used for analysis. RESULTS: Thirty-two patients were included in the final analysis. The incidence rates of the posterior open bite in the affected side were 100%, 87.5%, 71.9%, 9.4%, 3.1%, and 3.1% at 0, 3, and 7 days and 3 and 6 months, and at the last follow-up after surgery, respectively. Mean distances of the condylar movements were 2.67 and 0.32 mm in the affected joints and normal joints, respectively. There were significant differences for the anterior (P = .03), superior (P < .001), and posterior (P < .001) joint spaces of the affected joints as demonstrated by MRI. CONCLUSIONS: The joint spaces significantly increased postoperatively, in addition to the changes in condylar position in anterior and inferior movements, leading to posterior open bite; however, the position returns to normal 3 months after surgery. We concluded that disk repositioning, when done unilaterally, results in stable occlusion over time.