This study aimed to investigate the effect of cAMP-responsive-element-binding protein (CREB) overexpression on the differentiation of human stem cells from the apical papilla (hSCAPs), stimulated by transforming growth factor- beta (TGF-β1).

Cells were isolated from human immature third molars via enzymatic digestion. Four experimental groups were set up: ①a control group, receiving normal mineralization inducer (α-MEM, 10% FBS, 10 mmol/L β - sodium glycerophosphate, 50 μg/mL vitamin C, 10 nmol/L dexamethasone); ② a TGF- β1 group, receiving normal mineralization inducer and 5 μg/mL TGF-β1; ③ a TGF-β1+LV-empty group, receiving normal mineralization inducer and the transfected empty virus vector with 5 μg/mL TGF-β1; and ④ a TGF-β1+ov-CREB group, receiving normal mineralization inducer and the transfected CREB-overexpressing viral vector, with 5 μg/mL TGF-β1. The transfected cells were cultured in odontogenic medium in the presence or absence of TGF-β1 for 2 weeks. Alizarin red staining was used to detect mineralized nodules, and the mRNA expression of the mineralization genes runtrelated transcription factor 2 (RUNX2), dentin sialophosphoprotein (DSPP) and alkaline phosphatase (ALP) was measured by qPCR.

Compared with the control group (1.12 ± 0.11), TGF-β1 inhibited the deposition of calcium minerals (0.67 ± 0.12) (P < 0.05) via hSCAPs and inhibited the mRNA expression of RUNX2 (0.60 ± 0.03), DSPP (0.43 ± 0.12) and ALP (0.69 ± 0.05) (P < 0.05). In contrast, overexpression of CREB attenuated the effect of TGF-β1 on hSCAPs, resulting in the development of a high number of mineralized nodules (1.27 ± 0.10) (P < 0.01) and increased RNA levels of RUNX2 (1.33 ± 0.07), DSPP (1.32 ± 0.11) and ALP (1.26 ± 0.03) (P＜0.05) compared with those in the TGF-β1 group.

Overexpressed CREB promotes odontogenic differentiation of hSCAPs by interfering with TGF-β1.

This ex vivo study evaluated the effect of ultrasound and Er:YAG laser irrigation activation techniques on the penetration of sodium hypochlorite solution into infected human root canal dentin, providing a reference for clinical infection control of infected root canals.

Thirty-six cases of infected root canals were collected and randomly divided into three groups according to the irrigation technique: 12 cases in the conventional syringe irrigation (CSI) group, 12 cases in the passive ultrasonic irrigation (PUI) group, 12 cases in the Er:YAG laser and photon-induced photoacoustic streaming (PIPS) group and 36 cases of clean root canals (12 cases in the CSI group, 12 cases in the PUI group, 12 cases in the PIPS group). All of the selected root canals were straight root canals of posterior teeth. After standardizing the root length, all canals were subjected to instrumentation and dynamic irrigation. 2% methylene blue solution was used to visualize the penetration of the irrigant. EXAKT cutting and grinding equipment was used to take transverse sections of 100-150 μm at the coronal, middle and apical thirds of the root canals. The data (maximum penetration depth, average penetration depth, and penetration percentage) were observed under a light microscope to evaluate the effect of dye penetration.

With the three irrigation techniques, the maximum penetration depth, average penetration depth and penetration percentage of the infected root canals were significantly lower than those of clean root canals in the full length of the root canal (P ＜ 0.05). The penetration percentage, average penetration depth and maximum penetration depth of the PIPS group were significantly higher than those of the CSI group in the coronal, middle and apical thirds of the infected root canal, respectively (P ＜ 0.05). There was no significant difference in the maximum penetration depth, average penetration depth or penetration percentage between the PUI and CSI groups (P ＞ 0.05). There was also no significant difference in the maximum penetration depth, average penetration depth or penetration percentage between the PIPS and PUI groups (P ＞ 0.05).

The dentine permeability of infected root canals was weaker than that of clean root canals. Er:YAG laser-assisted irrigation activation technology could significantly improve the penetration of sodium hypochlorite solution into infected dentin, but passive ultrasonic irrigation did not significantly improve the penetration.