Relationship between interincisal angles and TMJ morphology/position and trabecular structure: a retrospective study.

BACKGROUND: TMJ morphology/position and trabecular structure are influenced by various factors. The role of the interincisal angle, an indicator of the anterior occlusal relationship, on TMJ remains unclear. This study aims to investigate the morphology, trabecular bone structure, and position of the condyle, as well as the glenoid fossa's morphology in skeletal class II populations with different interincisal angles. MATERIALS AND METHODS: A total of 150 adult patients with normodivergent facial types and skeletal class II malocclusions were selected and divided into three groups based on their interincisal angles: normal, small, and large angle groups. The indexes of TMJ were measured using cone-beam computed tomography (CBCT) data and analyzed using Dolphin Imaging, Mimics, and ImageJ. RESULTS: The small angle group had the smallest anteroposterior diameter (APD), while the large angle group had a greater mediolateral diameter (MLD). The large angle group exhibited significantly the largest maximum axial area, bone surface area, and bone volume (P < 0.05). Small and large angle groups exhibited greater bone trabeculae (Tb. N) and thinner trabecular thickness (Tb. Th). Compared to the normal angle group, the small angle group exhibited a larger horizontal condylar angle and smaller bilateral condylar angles on the axial plane, while the large angle group showed the opposite trend. Small and large angle groups showed a reduced vertical condyle angle on the coronal plane, with the largest reduction observed in the large angle group (P < 0.05). Small and large angle groups had higher heights of the glenoid fossa (GFH). The large angle group exhibited the greatest GFH and width of the glenoid fossa (GFW) (P < 0.05). CONCLUSION: The large angle group had elongated oval and large condyles, and deeper glenoid fossae, while a flattened-oval and smaller condyle, and wider and shallower glenoid fossae were observed in the small angle group. Small and large interincisal angle affects the structure of condylar trabeculae, resulting in thinner Tb. Th and greater Th. N. In the condylar position, small and large angle groups exhibit condylar rotation in the axial and coronal planes. Therefore, the interincisal angle affects the morphology, position, and trabecular structure of the TMJ. This implies that we must pay attention to the impact of the interincisal angle on TMJ, and it is crucial to restore the normal interincisal angle during orthodontic treatment.

Chronic intermittent hypobaric hypoxia ameliorates osteoporosis after spinal cord injury through balancing osteoblast and osteoclast activities in rats.

Introduction: As a common complication of spinal cord injury (SCI), most SCI patients suffer from osteoporosis. In our previous study, chronic intermittent hypobaric hypoxia (CIHH) could promote bone fracture healing. We speculated that it may act a role in the progression of osteoporosis. The current study purposed to explore the role of CIHH in the osteoporosis triggered by SCI in rats. Methods: A SCI-induced SCI model was established by completed transection at T9-T10 spinal cord of Wistar rats. One week after SCI, the rats were conducted to CIHH treatment (PB = 404 mmHg, Po2 = 84 mmHg) 6 hours a day for continuously 7 weeks. Results: The results of X-radiography and Micro-CT assessment demonstrated that compared with sham rats, the areal bone mineral density (BMD), bone volume to tissue volume, volumetric BMD, trabecular thickness, trabecular number, and trabecular connectivity were decreased. Trabecular bone pattern factor, trabecular separation, as well as structure model index were increased at the distal femur and proximal tibia of SCI rats, which were effectively reversed by CIHH treatment. Histomorphometry showed that CIHH treatment increased bone formation of SCI rats, as evidenced by the increased osteoid formation, the decreased number and surface of TRAP-positive osteoclasts. Furthermore, ELISA and real time PCR results showed that the osteoblastogenesis-related biomarkers, such as procollagen type 1 N-terminal propeptide, osteocalcin in serum, as well as ALP and OPG mRNAs in bone tissue were decreased, while the osteoclastogenesis-related biomarkers, including scleorostin in serum and RANKL and TRAP mRNAs in bone tissue were increased in SCI rats. Importantly, the deviations of aforementioned biomarkers were improved by CIHH treatment. Mechanically, the protective effects of CIHH might be at least partly mediated by hypoxia-inducible factor-1 alpha (HIF-1α) signaling pathway. Conclusion: The present study testified that CIHH treatment ameliorates osteoporosis after SCI by balancing osteoblast and osteoclast activities in rats.

Determination of E-modulus of cancellous bone derived from human humeri and validation of plotted single trabeculae: Development of a standardized humerus bone model.

Background: Evaluation of the mechanical behavior of the microstructure of cancellous bone seems important for the understanding of the mechanical behavior of bone. Prevention and treatment of fragility fractures due to osteoporosis is a major challenge according to ageing population. A bone model might help to assess fracture risk. Measurement of single trabeculae of bone should give further information compared with bone densitometry alone. This study measures the mechanical properties of single cancellous trabeculae derived from human proximal humerus. Methods: 34 single trabeculae dissected from human humeral heads were measured and evaluated mechanically. Trabeculae were fixed on microscope slides and geometrical data were reported during axial rotation of the specimens to measure the transverse section using computer aided design (CAD). The samples were subjected to a two-point bending test and were loaded with a measure-stamp at a defined distance. Force and deflection were measured by high-resolution sensors. The E-modulus was then calculated in combination with finite elements method simulation (FEM), using the previously obtained CAD-Data. Results: The average E-modulus from 34 valid measurements of human humeral trabeculae was 1678 MPa with a range from 829 to 3396 MPa, which is consistent with existing literature. The planned additional validation of the measurement method using manufactured three-dimensional synthetic trabeculae with known mechanical properties showed an average elastic modulus of single trabeculae of 51.5 MPa, being two dimensions lower than the value reported in the datasheet of the plastic. Conclusion: This newly developed, time and cost-efficient procedure allows the measurement of E-modulus in single trabeculae. Measurement of mechanic parameters of single trabeculae might give insights on mechanic behavior of bone and be relevant for the research of systemic bone diseases, complementing the existing data on bone-mineral-density. Further examination of single trabeculae of human cancellous bone should give an insight on the mechanical behavior of bone also considering systemic bone diseases.

Parameterized design and fabrication of porous bone scaffolds for the repair of cranial defects.

In bone tissue engineering, the structure of a scaffold is very important for cell growth and bone regeneration. It is better to make the scaffold resemble the native cancellous bone because natural cancellous bone can promote scaffold revascularization, which then accelerates cell proliferation. This study presents a parameterized design and fabrication method for cranial scaffold construction. A native human cranial sample was first scanned using micro computed tomography (CT), followed by 3D reconstruction, after which the internal structure of the bone trabecula was created. Based on an extracted negative bone trabecula model, the design components of "cavity", "connecting pipe" and "spatial framework" were proposed to describe the scaffold model. Then, by using the parameterized component model and an assembly and deformation algorithm, the bionic scaffold was designed. Its porous distribution, connection, porosity and area size were easily controlled. Finally, a biomaterial scaffold case was fabricated using a gelcasting process, and cell culture testing was performed in vitro to verify the scaffold's biocompatibility. The results show that the scaffold can promote cell growth and that cells accumulate in the form of a mass within three days.

Local influence of high molecular polyethylene particles on heterotopic ossification.

We studied the effect of molecular polyethylene particles on local heterotopic ossification. A total of 36 healthy Sprague-Dawley rats were randomly divided into the control group (n=18) and the observation group (n=18). High molecular polyethylene particles were injected to rupture Achilles tendon position in the observation group, and normal saline was injected in the control group. X-ray examinations were conducted on Achilles tendon in the 4th, 8th and 12th week after operation. The incidence rate of heterotopic ossification was evaluated, and bone trabecula morphological structure was studied under optical microscope after hematoxylin and eosin staining. Bone morphogenetic protein 2 (BMP-2), transforming growth factor-ß (TGF-ß), interleukin-1 (IL-1), tumor necrosis factor-α (TNF-α), runt-related transcription factor 2 (Runx2) and matrix metalloproteinase-9 (MMP-9) expression levels were also measured. Our results showed that heterotopic ossification incidence in the observation group was significantly lower than that in the control group. Achilles tendon structure in the control group increased in volume, and its texture was harder and cartilage-like. In the observation group, trabecular bone volume, thickness and quantity were more than those observed in the control group. BMP-2, TGF-ß, IL-1, TNF-α, Runx2 and MMP-9 levels in the observation group were significantly lower than those in the control group. We concluded that, high molecular polyethylene particles had a significant inhibiting effect on local heterotopic ossification.