February 2019

Scientific articles

Clinical Effectiveness of 6.5-mm-Long Implants to Support Two-Implant Fixed Prostheses in Premolar-Molar Region: The Influence of Immediate Loading and the Length of Splinting Implant

Research team

Javier Flores
Carlos Flores
Eduardo Anitua
Mohammad Hamdan Alkhraisat


The purpose of this retrospective clinical study was to assess the influence of immediate loading and lengths of splinted implants on the clinical effectiveness of 6.5-mm-long implants supporting two-implant fixed prostheses in the premolar-molar regions.

Materials and methods

A clinical database was reviewed in a private dental center to select those patients who had 6.5-mm-long implants placed to support two-implant fixed partial prostheses in the premolar-molar regions of the maxilla and the mandible. All implants were immediately loaded. The study groups were defined according to the lengths of the implants. Two groups were identified: the short-short splinted group, when both implants had 6.5 mm lengths, and the short-long splinted group, when one implant was longer than 6.5 mm. A total of 48 dental implants were placed in 16 patients to support 24 two-implant fixed prostheses. The mean follow-up time was 14 ± 5 months. The short-short splinted group included 8 patients with 16 implants; the short-long splinted group included 16 patients with 32 implants.

The main variable was implant survival, and secondary outcomes were marginal bone stability and prosthesis survival.


The statistical analyses indicated an absence of significant differences between the two groups in terms of implant and prosthesis survival (100% for both groups and both variables); however, distal bone loss around the splinted implants was significantly higher in the short-long splinted group. Bone loss was 0.37 ± 0.55 mm in the short-short splinted group and 0.94 ± 0.66 mm in the short-long splinted group.


Immediate loading of short (6.5-mm-long) implants in the premolar-molar regions did not jeopardize their survival. Two-implant supported prostheses had the same clinical effectiveness, whether extra-short implants were splinted to another extra-short implant or to a longer one.

© 2018 by the American College of Prosthodontists.

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