Ninety-eight patients with 207 implants complied with the treatment protocol attended the follow-up.

During the follow-up period, 15 implants failed in 12 patients. Age and gender were not correlated with a lower implant survival. The implant losses occurred in a time range between 0.5 and 39 months following implant placement (mean 7.3 ± 11.1 months). The reasons for implant failure were loss of osseointegration (n = 11), peri-implantitis (n = 2), occlusal trauma (n = 1), and mechanical complication (n = 1). From these 15 failures, 6 implants failed after delivery of the final prosthetic restoration while 9 implants failed without being prosthetically restored. The majority of failures (n = 13) occurred during the first year after placement (Table 2).

Cumulative survival rates (SRs) were 91.5% for all implants (Fig. 1). The remaining 194 implants in 88 patients were evaluated 12 to 77 months (mean 33.9 ± 14.7 months) following implant placement. Two more implants in 2 patients failed in this period.

The survival rate for 93 implants in 45 patients with no RFs was 94.8% whereas it was 94% for 83 implants in 48 patients with only local RFs (log rank, p = 0.618), 81.3% for 14 implants in 6 patients with only systemic RFs (p = 0,173), and 76.5% for 17 implants in 6 patients with both local and systemic risk factors (p = 0.006) (Fig. 2). The survival rate of implants in patients with no RFs compared to those with local and systemic RFs displayed a significant difference.

The implant survival was 91.3% in maxilla (n = 188) while it was 94.7% in mandible (n = 19) (log rank, p = 0.788). One hundred twenty-two implants were placed in the anterior region, 65 in the premolar region, and 20 in the molar region. From the total of 15 implant removals (SR 92.7%), 11 (SR 90.98%) occurred in the anterior region, 3 (SR 95.38%) in the premolar region, and 1 (SR 95.0%) in the molar region, so no significant difference was found regarding implant survival rate between the regions (log rank, p = 0.478). The implant diameter and length did not show any difference in survival rate. Delayed implant placement (n = 153, 91.9%) did not reveal a significant higher survival rate than implants placed immediately into extraction sites (n = 54, 90%) (p = 0.603). Delayed loaded implants (n = 142, 93%) did not show a significant higher survival rate than immediately provisionalized implants (n = 65, 89.3%) (p = 0.935). The treatment concept of immediate implant placement and immediate provisionalization (IPP, n = 30) did not have a negative impact on implant survival (IPP 92.1%, all other implants (n = 177) 91.4%, p = 0.809). Although the implant survival was lower in the group of implants with simultaneous bone grafting (n = 113, 88.1%) compared to those without (n = 94, 95.7%), the difference did not reach the level of significance (p = 0.151).