Preservation of all alveolar socket walls via longitudinal extraction after periotomy avoiding oro-vestibular luxation.

Meticulous cleaning of the extraction site.

Placement of rather long implants that allow for a high level of primary stability.

Implant dimensions were as follows: implant length 8.5 mm, 24 implants; 10 mm, 6 implants; 11.5 mm, 64 implants; 13 mm, 80 implants; 15 mm, 31 implants; and 18 mm, 2 implants. Implant diameters were as follows: 3.0 mm, 25 implants; 3.5 mm, 84 implants; 4.3 mm, 90 implants; and 5 mm, 8 implants.

If required, simultaneous reconstruction of the facial bony lamella via autologous bone chips harvested at the mandibular ramus.

Immediate restoration by temporary crown or bridgework either by individual chairside contouring and adjustment of acrylic resin denture teeth or by lab-fabricated restorations (in case of multiple teeth); all provisional restorations were delivered on the day of implant placement and adjusted to clear all contacts in centric occlusion and during eccentric movements.

Final restoration was delivered after 3 to 6 months.

Patients were examined clinically and radiographically at the time of implant placement and at least 12 months after implant placement. The primary outcome variable was the implant survival rate.

The secondary outcome parameter was the marginal bone level, which was determined using digital sequential periapical radiographs (XIOS XG Supreme, Dentsply Sirona, Bensheim). To ensure reproducibility between the examinations, radiographs were taken with paralleling technique using commercially available film holders (Dentsply/Rinn, Elgin, IL, USA). Specifically, the vertical distance between the implant shoulder and the bone level (mesial and distal) at the implant was measured. The distance was recorded to the nearest 0.1 mm using × 7 magnification. Attachment levels apical to the implant shoulder were designated as negative values.

Survival probabilities were estimated by the Kaplan-Meier method on a “per implant” basis [14]. The endpoint of interest was implant failure. To compare the survival distribution of two samples (no RF, local RF, systemic RF, local and systemic RF; maxilla vs. mandible; different implant diameters and lengths; immediate vs. delayed placement; immediate restoration and immediate provisionalization vs. other treatment concepts; with or without bone grafting), the log-rank test was used.