Four mm-long versus longer implants in augmented bone in posterior atrophic jaws – Three-year RCT results

Background

Dental implants are used to replace missing teeth. In many patients, it is not possible to place ì standard lengthî implants because of inadequate vertical bone heights. Clinicians are faced with the dilemma whether to attempt an augmentation procedure or to place short implants. Results of RCTs suggest that 5.0 to 8.0 mm-long implants can be a good alternative, but the question remains what will happen if the atrophy is advanced to an extent to allow only the placement of 4.0 mm-short implants.

Aim/Hypothesis

To evaluate whether 4 mm-short dental implants could be an alternative to augmentation procedures with xenografts and placement of at least 10 mm-long implants in posterior atrophic jaws.

Material and Methods

Forty patients with atrophic posterior mandibles having 5 to 6 mm bone height above the mandibular canal and 40 patients with atrophic maxillae having 4 to 5 mm below the maxillary sinus, were randomised according to a parallel group design to receive one to three 4.0 mm-short implants or one to three at least 10 mm-long implants in augmented bone. All implants had a diameter consisting of 4.0 or 4.5 mm. Mandibles were vertically augmented with interpositional equine bone blocks and implants were placed 4 months after the interpositional grafting. Maxillary sinuses were augmented with particulated porcine bone via a lateral window and implants were placed simultaneously. Implants were loaded after 4 months with provisional prostheses, replaced after 4 months by definitive ones. Outcome measures were- prosthesis and implant failures, any complication and peri-implant marginal bone level changes.

Results

In mandibles, one implant from the augmented group failed versus two 4.0 mm-short implants. In maxillae, three short implants failed versus seven long implants. Two prostheses on short implants were placed at a later stage because of implant failures versus six prostheses at augmented sites. There were no statistically significant differences in implant failures (P = 0.693) or prosthesis failures (P = 0.126). At mandibular sites nine augmented patients were affected by complications versus two patients treated with short implants (P = 0.01), the difference being statistically significant. No significant differences were found for maxillae- nine sinus lifted patients versus four short implant patients were affected by complications (P = 0.091). In mandibles average peri-implant bone loss was 0.26 lower in 4 mm-short implants, and 0.09 mm lower at short maxillary implants. The difference was statistically significant in mandibles (P < 0.001), but not in maxillae (P = 0.196).

Conclusion and Clinical Implications

4.0 mm-short implants achieved similar results, if not better, than longer implants in augmented jaws, but were affected by less complications. Short implants might be a preferable choice to bone augmentation, especially in mandibles, since the treatment is less invasive, faster, cheaper, and associated with less morbidity, however 5 to 10 years post-loading data are necessary before making reliable recommendations.