Mechanical stress can regulate temporomandibular joint cavitation via signalling pathways.

The temporomandibular joint (TMJ), composed of temporal fossa, mandibular condyle and a fibrocartilage disc with upper and lower cavities, is the biggest synovial joint and biomechanical hinge of the craniomaxillofacial musculoskeletal system. The initial events that give rise to TMJ cavities across diverse species are not fully understood. Most studies focus on the pivotal role of molecules such as Indian hedgehog (Ihh) and hyaluronic acid (HA) in TMJ cavitation. Although biologists have observed that mechanical stress plays an irreplaceable role in the development of biological tissues and organs, few studies have been concerned with how mechanical stress regulates TMJ cavitation. Based on the evidence from human or other animal embryos today, it is implicated that mechanical stress plays an essential role in TMJ cavitation. In this review, we discuss the relationship between mechanical stress and TMJ cavitation from evo-devo perspectives and review the clinical features and potential pathogenesis of TMJ dysplasia.

Spatial Heterogeneity Directs Energy Dissipation in Condylar Fibrocartilage.

Condylar fibrocartilage with structural and compositional heterogeneity can efficiently orchestrate load-bearing and energy dissipation, making the temporomandibular joint (TMJ) survive high occlusion loads for a prolonged lifetime. How the thin condylar fibrocartilage can achieve efficient energy dissipation to cushion enormous stresses remains an open question in biology and tissue engineering. Here, three distinct zones in the condylar fibrocartilage are identified by analyzing the components and structure from the macro-and microscale to the nanoscale. Specific proteins are highly expressed in each zone related to its mechanics. The heterogeneity of condylar fibrocartilage can direct energy dissipation through the nano-micron-macro gradient spatial scale, by atomic force microscope (AFM), nanoindentation, dynamic mechanical analyzer assay (DMA), and the corresponding energy dissipation mechanisms are exclusive for each distinct zone. This study reveals the significance of the heterogeneity of condylar fibrocartilage in mechanical behavior and provides new insights into the research methods for cartilage biomechanics and the design of energy-dissipative materials.

Do Open Reduction and Internal Fixation With Articular Disc Anatomical Reduction and Rigid Anchorage Manifest a Promising Prospect in the Treatment of Intracapsular Fractures?

PURPOSE: In response to the increased attention to soft tissue reduction in the treatment of intracapsular condylar fractures (ICFs), a modified open reduction technique is proposed and its functional and radiographic outcomes were evaluated in this study. PATIENTS AND METHODS: This is a retrospective case series study of patients with all ICF types that were treated with open reduction and internal fixation (ORIF) with articular disc anatomic reduction and rigid anchorage. Inclusion and exclusion criteria were strictly applied. Preoperative and postoperative clinical examinations of malocclusion, maximum incisor opening (MIO), laterotrusion, and temporomandibular disorder symptoms were recorded and analyzed. Computed tomography (CT) and magnetic resonance imaging (MRI) were used to assess articular position and condylar morphology and position. RESULTS: Thirty-four patients with ICFs (47 sides) were treated with the modified ORIF technique. At 6 months of follow-up, no malocclusion was found and the MIO considerably expanded to 3.56 ± 0.13 cm. Only 4 patients (12%) had temporomandibular joint discomfort with mouth opening. Interestingly, for unilateral type B ICFs, the laterotrusion distance to the ORIF sides was notably longer than to the non-ORIF sides. Postoperative CT and MRI showed that all fragments were properly reduced and the condyles were in the normal position. Postoperative anterior disc displacement occurred in 4 sides and condylar morphologic abnormalities (slight surface roughening and articular cartilage absorption) occurred in 3 sides (6.4%). CONCLUSIONS: This modified ORIF technique, which achieved good outcomes after treatment of all ICF types, shows promise for the treatment of ICFs.

Effect of the magnitude of condylar head displacement on the TMJ function in skeletal class II patients undergoing different degrees of mandibular advancement: A retrospective comparative study.

PURPOSE: This study aimed to compare the condylar head displacement (CHD) after bilateral sagittal split ramus osteotomy (BSSO) between different degrees of mandibular advancement in skeletal class II patients and to evaluate whether the temporomandibular joint (TMJ) function would be affected. PATIENTS AND METHODS: Fifty-nine patients (118 condyles) were included in this retrospective study and were divided into three groups based on the distance of mandibular advancement. The CHD in three directions, x (sagittal direction), y (coronal direction), and z (axial direction), was measured before operation (T0), immediately after operation (T1), and at least 6 months after operation (T2), and the TMJ function of patients was followed up and scored using the Helkimo index system. All the abovementioned data were statistically analyzed, and p < 0.05 was considered the statistical difference standard. RESULT: During the BSSO surgery, the condyle was predominantly displaced in a lateral, posterior, and superior direction whenever in T1 and T2, even though the degree of CHD was different. Regarding the amount of CHD, the large advancement group was higher than the other two groups in T1 and T2 (p＜0.01). The Helkimo index scores of the three groups were evaluated, and there was no significant statistical difference between the Ai and Di index of the three groups. CONCLUSION: In our center, CHD occurred in lateral, posterior, and superior directions following mandibular advancement in skeletal class II patients, with a positive correlation between the CHD and the mandibular advancement; however, the TMJ function of the three groups did not show significant differences.

Interspecies comparison of temporomandibular joint condylar cartilage extracellular matrix from macro to microscopy.

Interspecies comparisons of the extracellular matrix of temporomandibular joint (TMJ) condylar cartilage are necessary to elucidate the mechanisms underlying its superior mechanical properties, to guide the construction of animal models of TMJ-related diseases, and to establish standards for the engineering of TMJ condylar cartilage. Here we characterize and compare TMJ condylar cartilage from six different species from a materials science perspective, including structure, composition and mechanical properties from the macroscopic to the microscopic level. The gross morphology showed obvious interspecies differences in size and shape, which may be related to the different joint motion patterns. Although the condylar cartilage of all species can be divided histologically into a superficial fibrous layer and a deep hyaline layer, there are significant interspecies differences in the microstructure of the fibrils in the two layers, mainly in the diameter of the fibrils. Compositionally, there were no significant differences in collagen composition between species, but the content of glycosaminoglycans (GAGs) decreased progressively with increasing body size, with the same results obtained by Safranin O staining and biochemical analysis. Mechanically, the elastic modulus of mouse condylar cartilage was significantly higher than that of the other species and tended to decrease with increasing body size. This study shows that the TMJ condylar cartilage of different species has its own specific structure-composition-mechanics matching characteristics for their unique masticatory stress dissipation, and differences in fibril diameter and GAGs content may be the two ultimate factors influencing the differences in cartilage mechanical properties between species, while the condylar cartilage of pigs is most similar to that of humans, suggesting that pigs may be a suitable animal model for TMJ studies.

Mesoporous Doxorubicin-Loaded Polydopamine Nanoparticles Coated with a Platelet Membrane Suppress Tumor Growth in a Murine Model of Human Breast Cancer.

Bringing together photothermal therapy and chemotherapy (photothermal-chemotherapy, PT-CT) is a highly promising clinical approach but requires the development of intelligent multifunctional delivery vectors. In this work, we prepared mesoporous polydopamine nanoparticles (MPDA NPs) loaded with the chemotherapeutic drug doxorubicin (DOX). These NPs were then coated with the platelet membrane (PLTM). The coated MPDA NPs are spherical and clearly mesoporous in structure. They have a particle size of approximately 184 nm and pore size of ca. 45 nm. The NPs are potent photothermal agents and efficient DOX carriers, with increased rates of drug release observed in vitro in conditions representative of the tumor microenvironment. The NPs are preferentially taken up by cancer cells but not by macrophage cells, and while cytocompatible with healthy cells are highly toxic to cancer cells. An in vivo murine model of human breast cancer revealed that the NPs can markedly slow the growth of a tumor (ca. 9-fold smaller after 14 days' treatment), have extended pharmacokinetics compared to free DOX (with DOX still detectable in the bloodstream after 24 h when the NPs are applied), and are highly targeted with minimal off-site effects on the heart, liver, spleen, kidney, and lungs.

[Preparation and in vitro and in vivo study on tinidazole in situ forming sustained-release injection].

This study is to prepare the in situ forming sustained-release injection which can perform sustained release behavior at the periodontal site for 7 days and to evaluate its in vitro and in vivo properties. After preparation of in situ forming sustained-release injection the in situ time was studied. And the surface of the solid injection was characterized by SEM. The rheological curve at 0 degrees C, 25 degrees C, 37 degrees C was determined and the impact of the temperature on the viscosity was examined. The in vitro release behavior was investigated. At last, rabbit periodontitis model was established to study its pharmacokinetics. The injection was stable, hard to stratify and decompose. The in situ forming time was about 6 seconds. It can easily adhere into periodontal pockets. There were lots of holes on the surface of the solid injection for the drug to diffuse. The drug releasing curves could be fit by Korsmeyer-Peppas equation. The drug smoothly released for 7 days at pH 7.4 PBS buffer with a very slight burst release and maintained a certain concentration. In vivo pharmacokinetics results indicated that after administration with the in situ forming injection, achievement of tinidazole (TNZ) concentration in gingival crevicular fluid (GCF) was more comparable and long-lasting than usual solution of TNZ management and relatively constant TNZ levels were attained until 168 h. All these results supported the prospect of tinidazole in situ forming sustained-release injection in clinical applications.

Comparison of temporomandibular joint function and morphology after surgical and non-surgical treatment in adult condylar head fractures.

PURPOSE: The aim of this study was to evaluate whether surgical treatment can distinctly improve temporomandibular joint (TMJ) function and morphology in adult patients with condylar head fractures (CHFs) when compared with conservative treatment. PATIENTS AND METHODS: A retrospective study was performed to evaluate surgical and conservative outcomes in all patients who had suffered CHFs. In this study, all patients were divided into a surgical group and a conservative group. In the surgical group patients were treated by open reduction and internal fixation (ORIF) combined disc anchorage, while in the conservative group patients were treated by a removable splint combined with intermaxillary elastics. Clinical and radiological outcomes were evaluated and functional outcomes were assessed using the Helkimo index score. Paired t-tests, Wilcoxon signed rank tests, independent t-tests and χ2 tests were used to assess inter-group differences. RESULTS: 75 TMJs in 56 patients were included in this study and were divided into a surgical group (56 TMJs in 40 patients) and a conservative group (19 TMJs in 16 patients). The results showed that the Helkimo index score for TMJ in the surgical group was better than in the conservative group (pAi = 0.032, pDi = 0.001, respectively). Ramus height in the surgical group (61.08 ± 4.04 mm) recovered more than in the conservative group (54.82 ± 3.06 mm) (p = 0.012). Discs became shorter, moved further forward, and became severely distorted in the conservative group (disc length = 7.32 ± 1.35 mm). In contrast, discs became longer, retained a normal disc-condyle relationship, and formed a normal shape in the surgical group (disc length = 11.05 ± 2.07 mm) (p = 0.003). According to the MRI images, joint effusion, retrodiscal tear, and lateral capsular tear were better cured in the surgical group (p = 0.001, p < 0.001, p = 0.012, respectively). CONCLUSION: Based on these results, it seems that surgical treatment of condylar head fractures should be the preferred approach if there are no contraindications for general anesthesia.

Changes of disc status in adult patients with condylar head fracture who did or did not undergo disc anchoring operation.

PURPOSE: Views on treatment procedures for condylar head fractures (CHFs) are far from reaching a consensus. The aim of this study was to evaluate the changes in disc status for anteromedial disc displacement with anchorage (AMDDwA) and without anchorage (AMDDwoA - just suturing to the adjacent TMJ soft tissue) in adult CHFs, to get a better understanding of this very complex process and to show that rigid disc anchorage is an essential technique for the treatment of CHF during the open reduction and internal fixation (ORIF). PATIENTS AND METHODS: 144 temporomandibular joints (TMJ) in 95 patients were included in this retrospective study, and were divided into an AMDDwA group (50 TMJs in 38 patients) and an AMDDwoA group (94 TMJs in 57 patients) based on the different surgical procedures. The joints were quantitatively and qualitatively assessed for disc length and disc morphology preoperatively and at follow-up visits. Other variables, such as disc position, joint effusion, retrodiscal tear and lateral capsular tear, were also evaluated. Paired t-tests, Wilcoxon signed rank tests, independent t-tests and χ2 tests were used to assess intragroup and intergroup differences. RESULTS: The results showed that discs became shorter, moved further forward and distorted more seriously in the AMDDwoA group. In contrast, discs became longer, maintained a normal disc-condyle relationship in the AMDDwA group. Joint effusion, retrodiscal tear, and lateral capsular tear healed well in both groups. CONCLUSION: Taking these findings together suggests that the rigid disc anchorage is an alternative technique for the treatment of CHF.