[A prospective study on the application of 6-mm-long implants in the upper and lower posterior edentulous regions]

Objective: To assess clinical and radiographic outcomes of short implants (length six mm) in the posterior region and early-loading with splinted fixed dental prostheses. Methods: Forty-five patients were recruited at 3 centers and 2-3 implants (diameter 4 mm, length 6 mm) were implanted in each case. Totally, ninty-five implants were placed, using one-stage surgery protocol and loaded with a screw-retained splinted fixed prosthesis 6 weeks later. Clinical and radiographic examinations were performed preoperatively, post-surgery, at loading, and 6, 12 and 24 months after prosthesis placement. Results: Four implants were removed before loading. A total of 36 patients with 76 implants completed the whole treatment and 2 year follow-up according to the research design. No implant was lost after loading, and the 2-year survival rate of the implant was 100%(76/76). In all cases, the response of swelling and pain after operation was mild, and the bone resorption around the implants was not obvious at 6 months [(0.04±0.29) mm], 1 year [(-0.11±0.44) mm], and 2 years [(0.00±0.53) mm] after loading. Bone loss less than 1.00 mm was found only in 26% (18/69) implants after 2 years of loading, and the height of the alveolar bone around 17% (12/69) of the implant increased. During 2-year follow-up, the probing depth of the implants increased by nearly 0.50 mm, but there was no clinical significance (P>0.05). Conclusions: The 2-year results of this study showed that the 6-mm-long implants can be a predictable procedure, especially in situations with limited bone height in posterior edentulous regions.