In the present retrospective study, bone level implants (C-Tech Esthetic Line implants) were investigated clinically and radiologically. The bone level implant system has a Morse-locking conical implant-abutment connection with platform switching and an indexing hex that allows subcrestal implant placement and aims to prevent peri-implant bone loss. The surface of the implant system is manufactured by grit-blasting and acid-etching. The macrostructure of the implant consists of a beveled shoulder and three different threading profiles changing along the length of the implant.

Figure 1 gives a representation of the technical characteristics of the investigated C-Tech Esthetic Line implant system.

After a mean period of 3 years after loading, the implants were investigated clinically and radiologically according to previously published methods [14, 15]. To determine the stability of the peri-implant hard and soft tissue, the following parameters were analyzed: implant survival, that is, the implants being in situ; the width and thickness of the peri-implant keratinized gingiva (in millimeters); the probing depth (in millimeters); BOP; peri-implant bone loss (in millimeters); and the presence of peri-implant osteolysis. The probing depth was measured with a blunt periodontal probe at four sites (mesio-buccal, distal-buccal, mesio-oral, and disto-oral). Simultaneously to the measurement of the probing depths, the implant was checked to see if probing provoked bleeding (BOP).

To analyze the esthetic appearance of the implant-retained prosthetics, the PES was determined. Digital photographs including the neighboring and opposite teeth were recorded and evaluated by two independent experienced blinded investigators familiar with the PES scoring method. The PES score is generated using seven items (mesial papilla, distal papilla, soft-tissue level, soft-tissue contour, alveolar process deficiency, soft-tissue color, and texture) and an evaluation with a point score from 0 = very bad to 2 = excellent. Thus, a maximum score of 14 can be achieved. For determination of peri-implant bone loss, digitally recorded panoramic radiographies taken routinely after implant insertion and upon reexamination were analyzed with appropriate radiological software. Bone loss was measured mesially and distally, and a mean bone loss value was calculated.