Disc displacement (DD) appears in the majority of temporomandibular disorder (TMD) patients. The correlation between craniofacial morphology and different disc positions has been underlined, while the craniofacial morphological differences based on sex and sagittal skeletal pattern stratification have been insufficiently studied. In this study, 304 patients with TMD complaints were included and classified into normal position, disc displacement with reduction (DDwR) and disc displacement without reduction (DDwoR) groups according to magnetic resonance imaging. A total of 24 cephalometric measurements, covering the cranial base, vertical relationship, sagittal relationship, mandible position and morphology, and dental relationship, were assessed using lateral cephalograms. A stratified analysis was performed based on the sex and sagittal skeletal pattern. Overall, DD patients had distinctive craniofacial morphological features. The posterior cranial base length and mandibular arc angle were statistically different only in females, while the Y-axis angle, occlusal plane angle and sella nasion point A angle (SNA) might be unique features in males. Skeletal class II had the most statistically different measurements compared to the others. Differences in the Frankfort mandibular incisor angle (FMIA) and saddle angle were especially displayed in skeletal class III patients. The sex and skeletal sagittal pattern could affect the morphological differences in TMD patients with different disc positions.

Src homology-2 containing protein tyrosine phosphatase (SHP2), encoded by PTPN11, has been proven to participate in bone-related diseases, such as Noonan syndrome (NS), metachondromatosis and osteoarthritis. However, the mechanisms of SHP2 in bone remodeling and homeostasis maintenance are complex and undemonstrated. The abnormal expression of SHP2 can influence the differentiation and maturation of osteoblasts, osteoclasts and chondrocytes. Meanwhile, SHP2 mutations can act on the immune system, vasculature and nervous system, which in turn affect bone development and remodeling. Signaling pathways regulated by SHP2, such as mitogen-activated protein kinase (MAPK), Indian hedgehog (IHH) and phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K)/protein kinase B (AKT), are also involved in the proliferation, differentiation and migration of bone functioning cells. This review summarizes the recent advances of SHP2 on osteogenesis-related cells and niche cells in the bone marrow microenvironment. The phenotypic features of SHP2 conditional knockout mice and underlying mechanisms are discussed. The prospective applications of the current agonists or inhibitors that target SHP2 in bone-related diseases are also described. Full clarification of the role of SHP2 in bone remodeling will shed new light on potential treatment for bone related diseases.

Objectives Premolar extraction is a common therapeutic strategy in orthodontic treatment, which helps to achieve an aesthetic profile by adjusting the positional relationship between nose, lip and chin. This retrospective study aimed to examine the chin changes in response to premolar extraction and develop predictive models. Materials and Methods A total of 135 adults requiring orthodontic treatments with four premolars extraction were included in the study and the cephalometric indications for their chin changes, as well as other skeletal, dental and soft tissue changes were measured with lateral cephalograms. Morphometric analysis, Pearson’s correlation analysis and multivariate regression analysis were conducted to recognize the potential factors contributing to chin changes. Results Soft tissue pogonion (sPog) point advancement relative to both subnasale (Sn) vert plane and nasion-B (NB) plane was observed. The soft tissue thickness of boney gnathion-soft tissue gnathion (Gn-sGn), Z angle and mentolabial sulcus’s angle increased. Patients with larger ANB angle, longer and thicker upper lips showed less forward movement of chin. Patients with more protruded incisors may have greater changes in chin position and morphology. Additionally, changes of sella nasion point B angle (SNB), occlusion plane and the incisor position by premolar extraction can also influence the post-orthodontic chin position and morphology. Conclusions The position and morphology of chin changed in response to orthodontic extraction. Orthodontists should pay attention to sagittal skeletal pattern, occlusion plane, incisor position, soft tissue morphology and age before and during treatment, which were proved to be related to the chin changes. Clinical Relevance Clarifying and predicting the chin change caused by orthodontic extraction will facilitate treatment planning and physician-patient communication.