Radiographic evaluation of crestal bone levels of delayed implants at medium-term follow-up.

Purpose: The aim of this study was to evaluate the radiographic bone level changes after delayed implant placement at medium-term follow-up, with three elements kept constant: keratinized gingiva thickness, implant axes perpendicular to the opposing occlusal surface, and implants with a collar of 2 mm.
Materials and Methods: Patients treated in a private practice setting were retrospectively enrolled in the study. They underwent delayed placement (4 to 8 weeks after extraction) of dental implants in edentulous premolar or molar regions. Implants followed a delayed loading protocol. Crestal bone levels were measured at baseline; at provisional prosthesis placement; at 1, 3, and 5 years; and at medium-term follow-up of healing from implant placement.
Results: One hundred twenty patients received 135 implants (one or two implants per patient); 3 implants were lost. After a mean follow-up period of 9.71 ± 4.88 years, a survival rate of 97.76% was reported. At 1 year after implant placement, mean bone loss of -1.5 ± 0.62 mm was found. At almost 3 years post-implant placement, a mean bone gain of +1.20 ± 0.49 mm was seen, which was statistically significantly different compared with 1 year. After this point, the bone levels remained stable; similar values were reported over time, with no significant differences.
Conclusions: The mean vertical bone gain of +1.20 ± 0.49 mm seen at almost 3 years after implant placement in this study may be supported by both clinical parameters as presence of sufficiently thick keratinized gingiva (3 mm), implants with a 2-mm collar, and the axis of implant insertion perpendicular to the opposing occlusal surface.