The univariate analyses showed a significantly higher risk for peri-implantitis in GAP subjects (OR = 3.294 with p = 0.027) and at implants with bone quality grade 3 (OR = 21.200 with p = 0.000). However, these differences were not significant in multivariate analyses.

Both the uni- and multivariate patient-related analyses were non-significant.

The implant success rate was 77.9% for GCP implants and 38.5% for GAP implants. Twenty-two implants (21.2%) failed in 10 GCP subjects (41.7%), and 16 implants (61.5%) failed in (all) GAP subjects (100.0%).

In the multivariate implant-related analyses, implants placed in the maxilla (OR = 3.241 with p = 0.022), and in GAP subjects (OR = 4.218 with p = 0.006), had a significantly higher risk of failure.

The multivariate patient-related analyses showed a higher risk of implant failure in GAP subjects (OR = 3.032 with p = 0.004) (Table 5).

The mean mesial and distal marginal bone loss after 5 years was 2.19 mm (SD 1.85) in both patient groups. Peri-implant bone loss in GAP subjects was 2.89 mm (SD 1.90) and that in GCP subjects 1.38 mm (SD 1.05).

Mechanical complications were observed in two implants in two GAP subjects and in six implants in five GCP subjects. One abutment screw fractured, as well as the veneers of four ceramic crowns, and three abutments loosened and unscrewed. Surgical complications were not seen.