Long-term results after subcrestal or crestal placement of delayed loaded implants

Prevention of peri-implant bone loss is essential for achieving long-term implant success, but few studies have evaluated the impact of placement depth on long-term bone loss. The aim of this retrospective study was to evaluate outcomes for platform-shifted implants placed at different depths relative to the bone crest.

The mesial and distal shoulders of 228 delayed-loaded Ankylos® (Dentsply Implants Manufacturing GmbH, Mannheim, Germany) implants placed in 85 patients were divided retrospectively into two groups based on the implant shoulder position on the day of placement surgery as follows: subcrestal group A (n = 197; 0.5 mm or more below the crestal bone level) or crestal group B (n = 65; within 0.5 mm or less of the crestal bone level). The remaining sites (n = 194; more than 0.5 mm above the crestal bone level) were supracrestal and were excluded from this analysis. Mesial and distal bone loss was evaluated under 5× magnification and analyzed, along with Periotest values.

Mean Periotest values were -1.77 (±3.57) for Group A and -1.77 (±3.26) for Group B. For Group A, mean mesial (m) bone loss was 1.84 (±1.49 mm) and mean distal (d) bone loss was 1.73 (±1.31 mm). For Group B, the bone loss values were m: 1.41 (±1.65 mm) and d: 1.34 (±1.60 mm). No statistically significant differences were found for the Periotest values (p = .521) or bone level values for the two groups (m: p = .130; d: p = .153).

Within the limitations of this study, subcrestal or crestal implant placement in combination with delayed loading was associated with similar initial implant stability and subsequent crestal bone loss.