[Effect of Er,Cr:YSGG laser combined with guided bone regeneration technique on osteogenesis at the extraction site of periodontitis rats and its regulatory mechanism via the Wnt/β-catenin pathway].

Abstract

Purpose: To investigate the synergistic effect of Erbium, Chromium: Yttrium-Scandium-Gallium-Garnet (Er,Cr:YSGG) laser combined with guided bone regeneration (GBR) on osteogenesis at the extraction site in rats with severe periodontitis, as well as its regulatory mechanism on the Wnt/β-catenin signaling pathway.

Methods: A total of 60 SD rats were used to establish a severe periodontitis model, and 50 rats were successfully modeled. They were randomly divided into 5 groups (n=10 in each group), group A (blank control, simple teeth extraction), group B (teeth extraction+Er,Cr:YSGG laser irradiation), group C (teeth extraction+bone powder+barrier membrane), group D (teeth extraction+Er,Cr:YSGG laser irradiation +bone powder), and group E (teeth extraction+Er,Cr:YSGG laser irradiation+GBR). At 4 and 8 weeks postoperatively, 5 animals from each group were sacrificed for subsequent experiments. CBCT was performed to detect bone mineral density (BMD) and bone volume/total volume (BV/TV). Histological observation was conducted. Enzyme-linked immunosorbent assay (ELISA) and quantitative real-time polymerase chain reaction (qPCR) were used to detect β-catenin, Runx2 and other related factors. Meso scale discovery (MSD) technology was employed to determine the nuclear translocation of β-catenin and the phosphorylation level of GSK-3β.

Results: CBCT results showed that at 4 weeks postoperatively, the extraction sockets in groups A and B presented with a large area of low-density shadow, a small amount of fibrous callus was observed in group C and D, while group E had higher density of fibrous callus and local high-density shadow. At 8 weeks postoperatively, the bone defect still accounted for 60%-70% of the extraction socket in group A and B; new bone increased but bone powder was not fully degraded in group C and D; in group E, bone powder was basically degraded and new bone fused well with the surrounding bone. In terms of bone parameters, BMD and BV/TV in all groups increased with time. The BMD and BV/TV in group E were 0.51 g/cm³ and 36.14% at 4 weeks postoperatively and 0.57 g/cm³ and 43.23% at 8 weeks postoperatively, which were significantly higher than those in other groups at all time points(P＜0.05). The nuclear translocation rate of β-catenin in group E reached 58.7% at 8 weeks postoperatively, with high expression of osteogenic factors, while the levels of Dickkopf-related protein 1(DKK-1, 45.32 pg/mL) and phosphorylated GSK-3β/GSK-3β (0.21) were the lowest (P＜0.05). Histological results showed that group E had dense new bone and less inflammation, and the intergroup difference in osteogenic effect was group E ＞ groups C/D ＞ group B ＞ group A.

Conclusions: Er,Cr:YSGG laser combined with GBR can down-regulate DKK-1 expression, inhibit GSK-3β activity, relieve the inhibition of the Wnt/β-catenin pathway and promote osteogenesis. This study can provide experimental evidences for the clinical treatment of periodontal bone defects.