Objective:To explore the chain mediating effect of core self-evaluation and social withdrawal on the relationship between peer relationship and depression symptoms of adolescents.Methods:From September 2020 to October 2020, a sample of 1 936 students from grade 4 to grade 9 of different schools completed a cross-section questionnaire survey including the inventory of parent and peer attachment, core self-evaluation scale, child social preference scale-R and depression self-rating scale for children.SPSS 21.0 and SPSS PROCESS macro program were used for data statistics.The statistical methods included analysis of variance, correlation analysis and intermediary effect test.Results:(1) Peer relationship (94.78±17.27) was positively correlated with core self-evaluation (34.14±7.52) ( r=0.50, P<0.01), and negatively correlated with depression (12.21±6.02) and social withdrawal (32.34±11.45) ( r=-0.55, -0.58, both P<0.01). Core self-evaluation was negatively associated with social withdrawal and depression symptoms ( r=-0.48, -0.67, both P<0.01), while social withdrawal and depression was positively correlated ( r=0.54, P<0.01). (2) Peer relationship had a significant direct effect on depression symptoms (the effect value=-0.205, P<0.01). Core self-evaluation and social withdrawal respectively separate mediated the effect of peer relationship on depression symptoms (the effect value=-0.231, -0.088, 95% CI=-0.261--0.202, -0.110--0.068), while the chain mediating effect of the two was significant, and the effect value was -0.025(95% CI=-0.033--0.019). Conclusion:Good peer relationship can lead to higher core self-evaluation and less social withdrawal behaviors in adolescents that serves as buffer from depression.

Orthodontic treatment is more complicated when both soft and hard tissues must be considered because an impacted maxillary canine has important effects on function and esthetics. Compared with extraction of impacted maxillary canines, exposure followed by orthodontic traction can improve esthetics and better protect the patient's teeth and alveolar bone. Therefore, in order to achieve desirable tooth movement with minimal unexpected complications, a precise diagnosis is indispensable to establish an effective and efficient force system. In this report, we describe the case of a 31-year-old patient who had a labio-palatal horizontally impacted maxillary left canine with a severe occlusal alveolar bone defect and a missing maxillary left first premolar. Herein, with the aid of three-dimensional imaging, sequential traction was performed with a three-directional force device that finally achieved acceptable occlusion by bringing the horizontally impacted maxillary left canine into alignment. The maxillary left canine had normal gingival contours and was surrounded by a substantial amount of regenerated alveolar bone. The 1-year follow-up stability assessment demonstrated that the esthetic and functional outcomes were successful.

Vibration represents a micro reciprocating motion of a particle or object along a line or arc relative to a reference position, while the effect of low-magnitude high-frequency vibration (LMHFV) on skeletal system cells is similar to the mechanical stimulation of muscle movement. Bone mesenchymal stem cells (BMSCs), which have been identified as force-sensitive cells, exist in the bone marrows and have the potential of multi-lineage differentiation. Their biological characteristics can change functionally according to the appropriate stimulation in vitro, in order to reach the optimal demand of the stimulation. LMHFV can promote the osteogenic differentiation of BMSCs, therefore, the research on its mechanism can contribute to the application of vibration in the treatment of diseases such as osteoporosis, fracture, osteogenesis imperfecta, obesity as well as the promotion of orthodontic tooth movement. This paper summarizes the recent progress about the effects of vibration on BMSCs stem cells in osteogenesis and the possible mechanisms, so as to provide research ideas and methods for studying the mechanical as well as biological changes of BMSCs under vibration stimulation.