The planned study profile is to assess the peri-implant tissue outcome of abutment-supported restoration and direct implant-fixed restoration. Two treatments, Treatment A which is the abutment-fixed supra-structure and Treatment B, the direct implant-fixed restoration, are assessed within the scope of this clinical investigation.~Treatment A: The XiVE® CAD/CAM supra-structure is fixed on abutments. The effect of platform-switching which is discussed intensely in the scientific literature is used in order to shift away the connection between implant and supra-construction (interface) from the implant edge and peri-implant tissue and towards the implant centre. However, the implant-abutment-connection area is a potential entry port for micro-organisms which have direct influence on the state of the peri-implant hard and soft tissue and consequently on the long-term prosthetic and implant success [8]. By using an abutment as a connector between implant and supra-structure implies the generation of one more micro-gap (between supra-structure and abutment) and possible retention of microbial plaque though located above the hard tissue level.~Treatment B: The XiVE® CAD/CAM supra-structure is fixed directly on the implants. In contrary to treatment A, only one entry port (micro-gap) for micro-organisms exists: The interface between supra-construction and implant. So, there is one main point where the initial force has main influence on the implant and the peri-implant tissue [8-10]. Besides, this interface lies directly on the implant shoulder level and by that on the osseous level. There is no displacement of the transitional area to the implant centre.~This study has been designed in order to collect data with regards to the CAD/CAM system used on the DENTSPLY Friadent implant system XiVE®. In particular, the peri-implant tissue outcome of abutment-supported restoration and direct implant-fixed restoration will be evaluated. Therefore a small group of subjects with partly edentulous jaw is selected to show that both techniques are efficient and safe and to demonstrate the non-inferiority with regards to the peri-implant tissue outcome for any of both techniques.~Each subject will receive both treatments, treatment A on the one site of the maxilla and treatment B on the other. The randomization method which finally defines which subject receives one treatment on the left maxilla region and the other on the right maxilla area or vice versa is described in section 5.1.~In conclusion, both treatments might have pros and cons which may affect the peri-implant tissue outcome.
This study has been designed in order to collect data with regards to the peri-implant tissue outcome of abutment-supported restoration and direct implant-fixed restoration. Therefore a small group of subjects with partly edentulous maxilla is selected to show that both techniques are efficient and safe and to show comparable peri-implant tissue outcome for both methods. At the time of impression forming for each centre treatment A (= abutment-supported XiVE® CAD/CAM supra-structure) and B (= direct implant-fixed XiVE® CAD/CAM supra-structure) is assigned to the left and right side of the maxilla by being randomized at the time of impression forming.