Objective: Preparation of Nb₂C/3D printed silicon nitride (Si₃N₄) composite tissue engineering scaffolds and investigation on biological characteristics in vitro of Nb₂C MXene nanocoating. Methods: Si₃N₄ scaffold was prepared by 3D printing technology, and Nb₂C nanosheet suspension was prepared by HCl-LiF hydrothermal in situ corrosion and stripping treatment,Nb₂C biocoating was obtained by soaking the Si₃N₄ scaffold in 1.5 mg/mL Nb₂C nanosolution; Nb₂C/Si₃N₄ scaffold extracts were prepared and filtered and divided into four groups with MC3T3 cell lines, including blank control, positive control with 2% DMSO, Si₃N₄ and Nb₂C/Si₃N₄ groups, and cell proliferation activity was measured by CCK-8. Results: Compared to blank group, the proliferation activity of MC3T3 cells was significantly increased for positive control group (P＜0.05); Compared to Si₃N₄ group, the proliferation activity of MC3T3 cells was significantly increased for Nb2C/Si3N4 scaffold group (P＜0.05). Conclusions: Nb₂C/Si₃N₄ composite scaffold biolating can promote the proliferation of MC3T3 cells. It is a material with potential application for bone tissue engineering.

[Key words] Nb₂C; MXene; silicon nitride; biological coating; osteoblasts; cell proliferation; bone tissue engineering

Objective: To investigate the expression pattern of cyclin-dependent kinase regulatory subunit 2 (CKS2) and its effects on cell biological behavior in patients with oral squamous cell carcinoma (OSCC). Methods: Bioinformatics analysis was conducted to explore the expression level of CKS2 mRNA in OSCC and normal mucosal tissues. We selected 91 OSCC and 20 healthy oral mucosa samples. Immunohistochemical (IHC) staining was used to detect the expression level of CKS2 in 91 specimens of OSCC patients and 20 normal oral epithelial mucosa, and to explore the predictive value of CKS2 expression in OSCC patients. Small interfering RNA (siRNA) was used to silence CKS2 of Cal27 cells and its knockdown efficiency was determined by western blot. The effects of CKS2 silencing on the proliferation, cycle and migration of Cal27 cells were detected by cell clone formation assay, cycle assay and wound healing assay. Results: Bioinformatics analysis and IHC results showed that the expression of CKS2 in OSCC tissues was significantly higher than that of normal oral mucosa (P＜0.05). The expression of CKS2 was correlated with tumor size, cervical lymph node metastasis and survival rate of patients (P＜0.05). CKS2 silencing inhibited the proliferation and migration of Cal27 cells and induced G₂ phase arrest (P＜0.05). Conclusions: Our findings revealed that CKS2 was overexpressed in OSCC, its high expression relating to the poor prognosis of OSCC patients, and involving in the positive regulation of OSCC cell proliferation, migration and cycle.

Objective: To observe and analyze the clinical effect of single-retainer cantilever resin-bonded bridge in replacing single anterior tooth missing. Methods: Twenty single-retainer cantilever resin-bonded bridges were fabricated for single anterior tooth missing，and they were evaluated 6，12，24 and 36 months after restoration using the clinical evaluation criteria set by the American Public Health Association (APHA). At the same time, the periodontal indexes of the abutment tooth and the adjacent teeth before and after restoration were recorded to analyze the influence of the restoration on periodontal condition of the abutment teeth, and the VAS of patient satisfaction was quantified. Results: In 20 cases of single retainer cantilever resin-bonded bridge, no debonding or fracture occurred during 36 months of repair period. 1 case was classified as grade B due to edge coloring and the rest were graded. A 24 months after repair; 36 months after the completion of the restoration, 3 cases were classified as grade B due to edge coloring, and the rest were grade A. The patients' satisfaction with the restoration effect was 100%, and there was a significant difference in patients' satisfaction with the status of missing tooth area before and after restoration (P＜0.05). And there was no significant difference in the periodontal indexes of the abutment tooth before and after restoration (P＞0.05). Conclusions: For patients with single anterior tooth missing, using a single retainer cantilever resin-bonded bridge for restoration can obtain a relatively stable restoration results.