Sleeping vs. loaded implants, long-term observations via a retrospective analysis.

OBJECTIVE Several theories have been presented to explain initial and secondary marginal bone loss around dental implants (e.g. microbial load, adverse loading, microbial leakage, compromised healing/adaptation of host-implant interface). MATERIAL AND METHODS This study compared the long-term outcome (up to 12 years) of sleeping with loaded implants in the mandible via a split-mouth concept. Fourteen patients with overdentures were enrolled (10 women, mean age at implant insertion: 56 years [range: 33-71]). They presented with 28 loaded (position 33/43) and 14 sleeping implants (mostly position 31/41). At several follow-up visits, intra-oral radiographs (long-cone principle) were taken to observe marginal bone level changes. RESULTS At each observation, compared with abutment connection, the submerged non-loaded implants showed less bone loss (P-values: 1st year 0.007, 3 years 0.000, 5 years 0.002, 8 years 0.007, 12 years 0.000) than their neighbouring functional implants. This difference was primarily due to a more significant bone loss during the first year of loading (0.8 vs. 0.1 mm respectively), since afterwards, the bone level changes remained quite similar for both implant types. CONCLUSIONS Our data suggest that the first months of loading have a significant impact on the bone level (initial difference sleeping vs. loaded implants), followed by a more physiological bone level change afterwards. This initial difference might be explained by the adaptation of the surrounding bone to the loaded implant.