Extra short dental implants supporting an overdenture in the edentulous maxilla: a proof of concept

Objectives: This study investigates the outcome of short implants additionally placed with longer implants to support a maxillary overdenture. Materials and methods: Twelve patients received six implants to support a maxillary overdenture. Only one patient still had two molars in the maxilla, while the others had no remaining teeth. The status of the opposing arch was diverse. The distal implant in each quadrant was 6mm in height (S) and the middle implants ranged between 10 and 14mm (L). All implants were placed following a one-stage procedure and early loaded (6 weeks). Clinical and radiological parameters were assessed 6, 12 and 24 months after loading. Results: One short implant failed 2 weeks after surgery, probably due to early mobilization by the provisional prosthesis. The mean bone loss on the rough part of the implant was 0.7 mm (S) vs. 1.3mm (L) during the first year and 0.3mm (S) vs. 0.2mm (L) during the second year after loading. The mean implant stability quotient values were 67 (S) vs. 70 (L) at placement and 75 (S) vs. 78 (L) after 1 year. At the 2-year follow-up, all prostheses were still stable and comfortable. Conclusion: An overdenture on six implants, of which two have a reduced length, might represent a successful treatment option. No significant difference could be found between both implant lengths at 2 years' follow-up. However, bone loss with short implants may increase the likelihood of failure.