Assessments

Throughout the study, only radiographs consistent with standard implant procedures were taken. Bone level changes were assessed based on available and evaluable standardized periapical radiographs with a film-holder using parallel-technique or panoramic radiographs (depending on the standard in the study centers). Baseline was defined as the time of the first prosthetic installation (loading). Each investigator performed their own measurements on either digital or analog radiographs, as available. In order to achieve standardized measurements, all analog radiographs were digitized and measurements were performed on all radiographs with the free-available software ImageJ 1.50i by an experienced independent person and subsequently validated by the investigators. All periapical and panoramic radiographs were individually calibrated (distance of three threads) to account for the distortion of the pictures. The distance from the implant shoulder to the first visible bone contact at the mesial and distal aspect of the implants was measured. The measurements at the mesial and distal site were averaged to obtain the bone level per implant. The changes in the bone level were calculated over several intervals: from loading to 5 years post-loading and at yearly intervals starting from 1 year post-loading to evaluate the success criteria. Bone quality [26] was assessed during the surgery (D1 to D4). Clinical parameters to assess the soft tissue health, including Modified Plaque Index (MPI), Papilla Index, Sulcus Bleeding Index (SBI), and pocket probing depth (PPD) (if measured), were recorded during abutment placement, during placement of the definitive prosthesis, and at each subsequent follow-up visit. The MPI and SBI were measured according to the criteria described by Mombelli [27]. The presence of the mesial and the distal papilla was evaluated according to the Jemt papilla score [28]. PPD, if routinely measured, was evaluated as a change in probing depths at 1, 3, and 5 years, compared with baseline. MPI, SBI, and PPD were determined on the buccal, lingual, distal, and mesial sites on each implant; the mean value of the scores was taken to provide the assessment of the implant.