The aim of the review was to assess the influence of various local risk factors on the outcome of implant therapy.

• Limited data (two prospective clinical trials) exist evaluating the available interdental space as a risk factor for implant survival.
• Two clinical studies (both prospective clinical trials) show that as the proximity of the implant to the neighboring tooth decreases (< 3 mm), the proximal bone loss on adjacent teeth could increase following implant placement.
• There is evidence examining the placement of dental implants into infected sites exhibiting apical pathology. Two clinical trials (one randomized clinical trial, one prospective randomized trial) have shown survival rates greater than 92% after 1 year when the implants were placed in debrided sockets and with primary stability.
• There is no evidence supporting soft tissue thickness as a risk factor in implant survival. While the secondary outcome of gingival recession is important, there was no significant correlation with tissue thickness and recession around dental implants (one retrospective clinical study).

In a recent systematic review, methods of bone density and implant stability assessment were not validated and therefore cannot be linked with implant survival.

With respect to local risk factors, the following recommendation can be made:

• Special care should be taken in selection of implant diameter and design in areas with limited interdental space.