Clinical study on survival rate of short implants placed in the posterior mandibular region: resonance frequency analysis

ObjectiveShort implants are increasingly used, but there is doubt about their performance being similar to that of regular implants. The aim of this study was to compare the mechanical stability of short implants vs. regular implants placed in the edentulous posterior mandible. Material and methodsTwenty-three patients received a total of 48 short implants (5x5.5mm and 5x7mm) and 42 regular implants (4x10mm and 4x11.5mm) in the posterior mandible. Patients who received short implants had <10mm of bone height measured from the bone crest to the outer wall of the mandibular canal. Resonance frequency analysis (RFA) was performed at time intervals T0 (immediately after implant placement), T1 (after 15days), T2 (after 30days), T3 (after 60days), and T4 (after 90days). ResultsThe survival rate after 90days was 87.5% for the short implants and 100% for regular implants (P<0.05). There was no significant difference between the implants in time intervals T1, T2, T3, and T4. In T0, the RFA values of 5x5.5 implants were higher than values of 5x7 and 4x11.5 implants (P<0.05). A total of six short implants that were placed in four patients were lost (three of 5x5.5mm and three of 5x7mm). Three lost implants started with high ISQ values, which progressively decreased. The other three lost implants started with a slightly lower ISQ value, which rose and then began to fall. ConclusionsSurvival rate of short implants after 90days was lower than that of regular implants. However, short implants may be considered a reasonable alternative for rehabilitation of severely resorbed mandibles with reduced height, to avoid performing bone reconstruction before implant placement. Patients need to be aware of the reduced survival rate compared with regular implants before implant placement to avoid disappointments.