As described by Hirsch et al., Aparicio et al., and Farzad et al., this criteria was assessed by periapical radiographs obtained by the parallelism technique combined with panoramic radiographs for conventional implants and CT scans for zygomatic implants. The bone loss was defined as a vertical change of bone level measured from the most inferior line of implant exposure. All previous studies have demonstrated satisfactory sustained levels over a period of 60 months of the load application.

One aspect to be considered is that our research is a retrospective cohort study, making it difficult to find a standardization of radiographs that could accurately determine the annual bone loss as described by Farzad et al., especially for conventional implants. Sometimes when the conventional implant is slightly tilted to the palate in cases of anterior maxillary atrophy, it is difficult to obtain adequate periapical radiographs by the parallelism technique. Therefore, the methodology suggested by Lang and Lindhe was used with reference to the implant bone level that should not be less than two thirds of its total length in order to have a satisfactory osseointegration. Additionally, the radiographic criteria recommended by Buser were used to analyze the presence/absence of persistent radiolucency around the implant.

For greater accuracy to assess implant osseointegration, percussion and immobility tests are described in the literature. Performing these tests requires the removal of fixed prosthesis, which in our view, would be justified only in cases of necessity for prosthesis replacement or when mismatches or gaps was observed in the rehabilitation and/or implants, since the osseointegration loss can also be verified by signs indicating decreased bone volume around the implant, periimplant radiolucency, the presence of spontaneous pain on palpation, local redness, and the presence of purulent secretion. According to Von Krammer, periimplantar mobility is generally associated with periimplant radiolucency and this monitoring method has the advantage of not requiring removal of the prosthesis during the evaluation.