Abstract: Objective: To investigate the effect of zirconia crowns and cobalt-chromium alloy crown restoration on abutment periodontal index and pathogens. Methods: One hundred and forty-two cases of total crown restoration patients were randomly divided into Zirconia group (n=75) and Cobalt-chromium alloy group, respectively (n=67). At different time points: before restoration (T₀), 6 months after restoration (T₁), 12 months after restoration (T₂) and 24 months after restoration (T₃), the gingival color, gingival bleeding index (BI), probing depth (PD) and plaque index (PLI) were recorded. H.actinomycetemcomitans (Ha), Fusobacterium (Fn), Porphyromonas gingivalis aeromonas (Pg), Prevotella intermedia (Pi), Tannerella forsythensis (Tf) and Treponema denticola (Td) in subgingival plaque samples were detected using polymerase chain reaction (PCR) method. Results: Compared with T0, BI and PD were increased at T1~3 in both groups, BI and PD in Zirconia group were significantly less than those in Cobalt-chromium alloy group at T1~3 (P<0.05). Twelve months after restoration, the detection rates of Aa, Fn, Pg, Tf and Td in subgingival plaque samples in Zirconia group were significantly lower than those in Cobalt-chromium alloy group (P<0.05). Conclusion: Compared with cobalt-chromium alloy restoration, zirconia crown restoration is beneficial to abutment periodontal index and pathogens.