Objective:To investigate the effect of probiotic regulation combined with photodynamic therapy in peri-implantitis and its influence on microbial ecological reconstruction.Methods:A total of 106 patients with peri-implantitis were divided into Group A(n=36),Group B(n=35),and Group C(n=35)according to different treatment methods.Group C received conventional treat-ment,Group B received photodynamic therapy based on conventional treatment,and Group A received probiotic regulation combined with photodynamic therapy.Periodontal status indicators[probing depth(PD),sulcus bleeding index(SBI),plaque index(PLI)],marginal bone loss(MBL)measurements,peri-implant bacterial load,gingival crevicular fluid bone metabolism indicators[alkaline phosphatase(ALP),osteocalcin(BGP),osteoprotegerin(OPG)],gingival crevicular fluid inflammatory indicators[interleukin-1β(IL-1β),tumor necrosis factor-α(TNF-α),interleukin-6(IL-6),high-sensitivity C-reactive protein(hs-CRP)],as well as adverse reactions and recurrence rates at 6-month follow-up were compared among the three groups.Results:The levels of periodontal status in-dicators PD,PLI,and SBI in Group A at 4 weeks,3 months,and 6 months after treatment were lower than those in Group B,which were lower than those in Group C(P<0.05).The MBL measurements in Group A at 3 months and 6 months after treatment were lower than those in Group B,which were lower than those in Group C(P<0.05).The loads of Fusobacterium nucleatum,Aggregatibacter actino-mycetemcomitans,Treponema denticola,Porphyromonas gingivalis,Ekenella corrodens,and Prevotella intermedia in Group A at 4 weeks and 6 months after treatment were lower than those in Group B,which were lower than those in Group C(P<0.05).The levels of bone metabolism indicators ALP,BGP,and OPG in Group A at 4 weeks,3 months,and 6 months after treatment were higher than those in Group B,which were higher than those in Group C(P<0.05).The levels of gingival crevicular fluid inflammatory indicators IL-6,IL-1β,TNF-α,and hs-CRP in Group A at 4 weeks,3 months,and 6 months after treatment were lower than those in Group B,which were lower than those in Group C(P<0.05).There were no statistically significant differences in the incidence of adverse reactions during treatment and the recurrence rate at 6-month follow-up among the three groups(P>0.05).Conclusion:Probiotic regulation combined with photodynamic therapy for the treatment of peri-implantitis can exert synergistic antibacterial effects,improve periodontal indicators,reduce pathogen load,alleviate inflammatory response,and regulate bone metabolism balance.