Risk Assessment of Proximal Contact Loss Between Implant-supported Prostheses and Adjacent Teeth.

Inclusion Criteria: * (1) Patients over the age of 18, can fully understand the nature of the proposed and be able to sign a consent form. * (2) patients who underwent dental implant surgery and delivered prostheses for more than 3 months in Nanjing First Hospital. Exclusion Criteria: * (1) The implant site or adjacent teeth were severely injured and the adjacent teeth were extracted; * (2) the same quadrant orthodontic or splint treatment; * (3) the prostheses have been removed due to failure or need further treatment; * (4) implant-supported prostheses in both mesial and distal sites; * (5) the adjacent teeth were directly or indirectly fixed with the implant-supported prosthesis; * (6) patients with missing clinical records of PD, PCR and BOP. * (7) The prosthetic prosthesis with implant-supported prosthesis was delivered for less than 3 months in Nanjing First Hospital.