RESUMO
BACKGROUND: Biological responses to different loading protocols during the bone healing phase in subjects with long time since edentulism, rehabilitated with narrow diameter implants (NDIs) to retain mandibular overdentures (MOs), are still unavailable. OBJECTIVE: This randomized clinical trial compared the peri-implant health, implant stability, and concentrations of pro- and anti-inflammatory cytokines in the peri-implant crevicular fluid (PICF) in mandibular edentulous patients under conventional (CL) and immediate loading (IML) during healing. METHODOLOGY: Twenty totally edentulous patients received two NDIs (2.9 × 10 mm, Facility NeoPoros) placed in mandible anterior region and were randomly assigned to two loading protocols: CL (n = 10) and IML (n = 10). The following clinical outcomes were evaluated 1, 2, 4, 8, and 12 weeks after surgery: (a) peri-implant tissue health (gingival index-GI, plaque index-PI, calculus-presence CP, probing depth-PD, and bleeding on probing-BOP); (b) implant stability quotient (ISQ); and (c) IL-1ß, IL-6, IL-10, and TNF-α levels in the PICF analyzed by ELISA. RESULTS: The CL group showed significantly higher CP scores at weeks 8 and 12. The IML group showed significantly higher GI from the first week onwards. The IML group presented significantly lower PD at all follow-up times, and higher BOP rates than CL at week 12. The ISQ values of the CL group were higher than those of the IML group, except at week 4. The IML group released significantly more TNF-α between weeks 1 and 4 and more IL-1ß during week 4-12, while releasing less IL-6 until week 8, mainly at week 2 (-47.6%). The release of IL-10 was similar for both groups and increased progressively over time. At week 12, the IML group released 45.74% more IL-10 than the CL group. The survival rates were 95% and 90% for CL and IML, respectively. CONCLUSION: The IML group presented more favorable PD at all evaluation times; the differences between the other clinical parameters were less systematic. The implant stability and the inflammatory marker concentrations were more stable in the CL group.