One hundred and thirty-three patients receiving 174 implants were selected: 87 immediate implants (IM) and as a matched group 87 implants that were inserted in healed bone (control group (CG)).

The mean age of the patients in this study was 42 years, the youngest patient being 15 years old and the oldest 75 years at the time they received their implant. A gender and age distribution of all inserted implants is outlined in Table 1. Figure 2 shows a distribution of the prosthodontic indication. The prosthodontic indication was no matching criteria, and therefore, Fig. 2 shows an overview over all the implants and their prosthodontic indications in this study.

In total, 133 patients received 174 implants. This number equally consists of immediate and non-immediate implants. For every immediate implant, a control implant from the non-immediate group was needed. For an ideal comparison, this control implant had to match some criteria. In a 2000 published thesis with a great number of implants, it was shown that the crucial criteria for comparing the survival of implants are the diameter and the location of the implant as well as the gender of the patient [9]. Figure 3 gives an overview of the implants and their locations while Table 2 shows the number of implants in regard to the diameters and lengths.

Conventional radiographs were taken right after implant insertion, the day patients received their prosthetic restoration and further on in irregular intervals whenever indicated or necessary for other treatments. A total of 974 radiographic images of implants were assessed in this study, 408 were panoramic radiographs and 566 were intraoral radiographs.

The radiographs where digitalized using a transmitted light scanner (Intelli Scan 1600, QUATOGRAPHIC Technology GmbH, 38112 Braunschweig, Germany) using the Silverfast AI scanprogam (Version 6.4 LaserSoft Imaging AG, 24105 Kiel, Germany) and imported into the Sidexis XG program (Sirona, 64625 Bensheim, Germany). For an ideal result of the scanned images, they were imported with a resolution of 300 dpi and a 16-bit grayscale. The resulting digital images had to be converted from .tiff files to .bmp files before importing them into the Sidexis program.