Objective To investigate the therapeutic effects and mechanism of quercetin in the treatment of periodontitis.Methods The rat periodontitis model was induced using ligation combined with lipopolysaccharide(LPS)injection method.Fifty successfully modeled periodontitis rats were randomly divided into 5 groups:the model group,the quercetin group(100 mg/kg quercetin by oral gavage),the quercetin+fibroblast growth factor receptor 1(FGFR1)overexpression plasmid(AV-FGFR1)group[100 mg/kg quercetin by oral gavage+10 nmol AV-FGFR1 via tail vein injection],the AV-FGFR1 group(10 nmol FGFR1 overexpression plasmids via tail vein injection),and the AV-NC group(10 nmol empty plasmids via tail vein injection),with 10 rats in each group.The normal group(10 rats)received the same volume of saline by oral gavage.After treatment completion,alveolar bone loss was observed by Micro-CT,periodontal tissue damage was observed by hematoxylin-eosin(HE)staining,serum levels of tumor necrosis factor(TNF)-α,interleukin(IL)-1β,and IL-18 were measured by enzyme-linked immunosorbent assay(ELISA),the proportion of FGFR1-positive cells in periodontal tissues was detected by immunohistochemistry,and protein expression levels of the FGFR1/Toll-like receptor 4(TLR4)/NLRP3 inflammasome pathway were analyzed by Western Blot.Results Compared with the normal group,the model group and AV-FGFR1 group showed significantly decreased bone mineral density(BMD)and bone volume/tissue volume(BV/TV),while serum TNF-α,IL-1β,IL-18 levels,the proportion levels of FGFR1-positive cells,and protein expression levels of FGFR1,TLR4,NF-κB p65,NLRP3,apoptosis-associated speck-like protein(ASC),and cleaved cysteinyl aspartate specific proteinase caspase-1(C-caspase-1)were increased,with statistical significance(P＜0.05).The AV-FGFR1 group exhibited more obvious decrease or increase effects.Administration of quercetin significantly improved these indexes in the model group.However,the therapeutic effects of quercetin were weakened after FGFR1 overexpression.Conclusion Quercetin can repair alveolar bone loss,ameliorate histopathological damage,and alleviate inflammatory injury in periodontitis rats,which may be mediated through inhibition of the FGFR1/TLR4/NLRP3 inflammasome pathway.