Figure 2. Complication incidence in the two implant systems Figure 2. Complication incidence in the two implant systems. Soft tissue complications, belonging to the category of biological complications, occurred more often in the ECSs, while loosening or fracture of the abutment or screw was more frequent in the ICS-BLs. PD: periodontal debridement, ECS: external connection implant system, ICS-BL: bone-level internal connection implant system. **P<0.01. ***P<0.001. J Periodontal Implant Sci. 2015 Feb;45(1):23-29. http://dx.doi.org/10.5051/jpis.2015.45.1.23