Purpose: To evaluate whether short (5 mm) dental implants could be a suitable alternative to augmentation
and placement of longer implants (10 mm) in posterior atrophic jaws.
Materials and methods: Thirty partially edentulous patients with bilateral posterior edentulism were
included: 15 patients having 5 to 7 mm of residual crestal height above the mandibular canal, and
15 patients having 4 to 6 mm of residual crestal height below the maxillary sinus and bone thickness
of at least 8 mm measured on a CT scan. The patients were randomised either to receive one to three
submerged 5-mm-long Rescue implants (Megagen) or 10-mm-long implants placed in augmented
bone according to a split-mouth design. Mandibles were augmented with interpositional anorganic
bovine bone blocks (Bio-Oss) and maxillae with granular Bio-Oss placed through a lateral window
under the lifted sinus membrane. Resorbable barriers were used to cover the grafted sites. Grafts were
left to heal for 4 months before placing the implants using a submerged technique. Four months after
implant placement, provisional reinforced acrylic prostheses were delivered and replaced 4 months later
by definitive screw-retained metal-ceramic prostheses. Outcome measures were: prosthesis and
implant failures, any complications, time needed to fully recover mental nerve function (only for
mandibular implants) and patient preference assessed 1 month after loading. All patients were followed
up to delivery of the final restorations (4 months after loading).
Results: A systematic deviation from the research protocol occurred: the operator used another
implant system (EZ Plus, Megagen) for implants 10 mm or longer with a diameter of 4 mm at the augmented
sites. No patients dropped out. In 5 patients of the augmented group (all mandibles), there
was not enough height to place 10-mm-long implants as planned and shorter implants (7 and 8.5 mm)
were used instead. In each group, one prosthesis could not be placed when planned because an implant
was found to be mobile at abutment connection: one 5 mm maxillary implant and one 8.5 mm
mandibular implant in the augmented group. Five complications occurred: two in the augmented
group (one maxillary sinus perforation and one mandibular wound dehiscence after implant placement
possibly associated with the failure of one implant) versus three maxillary sinus perforations in
the 5-mm-long implant group. The difference was not statistically significant. No patient suffered from
permanent disruption of alveolar inferior nerve function, however, significantly more patients had
paraesthesia for up to 3 days in the augmented group. There was no statistically significant difference
in patient preference with the majority of patients expressing no preference for which treatment they
received, finding both of them acceptable.
