Objective This study aims to investigate the effect of the marginal position of porcelain-fused-to-metal(PFM) crown on periodontal health. Methods Sixty patients who needed PFM crown for the mandibular first molar were randomly divided into two groups of 30 patients each according to the difference in the marginal position of the crown. Group A comprised patients with crown margins under the gingival level, whereas Group B was composed of patients with crown margin at the gingival level. Gingival crevicular fluid(GCF) were collected at four time points, namely, before crown cementation and at 1, 3, and 6 months after crown cementation. GCF volume, endotoxin levels, and aspartate transaminase(AST) were detected using an automated chemical analyzer. The differences among the variations between pre- and post-crown cementation and between the two groups were analyzed. Results GCF volume, endotoxin levels, and AST in Group A increased at 1, 3, and 6 months after cementation compared with that before crown cementation(P0.05). Significant statistical differences were found between the means of variation of Groups A and B at 1, 3, and 6 months after cementation(P
