After a mean loading period of 5 years (range 2–7 years), the implants were clinically and radiologically analyzed to determine the overall implant success, mean survival and suitability for prosthetic rehabilitation, peri-implant hard and soft tissue health, and patient acceptance. Furthermore, peri-implant hard and soft tissue indices, such as bleeding on probing (BoP), probing pocket depth (PPD), marginal bone loss (MBL), and presence of peri-implant osteolysis, were analyzed.

Table 1 gives an overview of the patient information, implant localization, and implant data for the retrospectively investigated implants.

In the present retrospective study, Conelog® Screw-line implants (Camlog Biotechnologies, Basle, Suisse) of 7-mm length and of diameters of 3.8 mm, 4.3 mm, and 5.0 mm were used to replace missing teeth in the molar region of the maxilla. The implant system has a Morse-locking conical implant-abutment connection with platform switching and 3-point indexing. The Promote® surface of the implant system is manufactured by grit blasting and acid etching that support osseointegration.

After a mean period of 5 years (range 2–7 years), the patients were clinically and radiologically investigated at the Department for Oral, Cranio-Maxillofacial, and Facial Plastic Surgery of the Medical Center of Goethe University Frankfurt according to previously published methods [1, 3, 10].

The following parameters were investigated to determine the clinical suitability of the short-length implants and the peri-implant hard and soft tissue stability: implant survival, i.e., implants being in situ and suitable for prosthetic restoration; the width and thickness of the peri-implant keratinized gingiva (in mm); PPD (in mm); BoP; radiologically calculated MBL; and presence of peri-implant osteolysis. The PPD was measured at 4 sites (mesio-buccal, distal-buccal, mesio-oral, and disto-oral) with a blunt periodontal probe. Simultaneously, to the measurement of the probing pocket depths, the peri-implant soft tissue was checked to see if the probing provoked bleeding (BoP). The peri-implant MBL was calculated at digitally recorded perpendicular single-tooth images taken routinely after implant insertion and for the regular follow-up checks. The distance between the peri-implant marginal bone level and the implant shoulder serving as reference point was measured. Bone loss was measured mesially and distally, and a mean bone loss value from these measurements was calculated.