When a patient fulfilled all inclusion criteria and had no exclusion criteria, then he/she got implant surgery and checked the condition met first criteria for loading (loading criteria 1 (LC1)) (Table 2).

All patients received Ti grade IV Straumann Standard Plus Regular Neck (SP RN) implants, 4.1 mm in diameter and 8, 10, or 12 mm in length, with SLActive® surface (Institut Straumann AG, Basel, Switzerland).

Patients fulfilling the necessary criteria were randomized to the early loading arm (implant loading after 25 ± 3 days) or conventional loading arm (implant loading after 13 ± 1 weeks). The initial randomization sequence was created after implant surgery once the previously defined LC1 had been met, by means of variable block sizes in order to avoid disproportionate allocation within early loading or conventional loading groups [39]. Lists were prepared by an independent statistician and were centrally controlled by a third party who was not involved in the study. All patients who fulfilled LC1 were included in the full analysis set (FAS). If patients did not fulfill LC1, they received an alternative treatment, e.g., bridge, false teeth, or treatment by other implant, and were subsequently included and evaluated in the safety analysis set (SAS).

Loading criteria were evaluated once more (loading criteria 2 (LC2); Table 2) at the time of provisional restoration delivery at 25 ± 3 days after surgery in the early loading arm and at 13 ± 1 weeks after surgery in the conventional loading arm (Fig. 2). Patients fulfilling the LC2 criteria were included in the per protocol set (PPS). If patients did not fulfill LC2 (i.e., due to an unstable implant or moderate to severe pain), they received an alternative treatment and were included in the FAS. All patients receiving an implant were therefore included in the FAS irrespective of whether they fulfilled LC2.

There were six evaluation time points from recruitment to study completion with a variety of safety and efficacy data obtained at each time point, including primary and secondary endpoint data. The day of implant surgery (day 0) was the baseline time point; patient consent and screening procedures were performed between 8 weeks and 1 day before day 0. Implant surgery and placement were performed according to the manufacturer’s recommended guidelines. All implants were placed in the alveolar ridge that had healed for at least 16 weeks after tooth extraction. Sutures were removed 7–14 days after surgery. In both arms, ready-made abutments for cement retention were connected at 15 Ncm and implants were loaded through temporary crown. The occlusal contacts were equivalated as holding a 21-μm AccuFilm II (Parkell Inc, Edgewood, NY, USA) when patients bite heavily. Final crowns were placed 6 months after implant placement in both groups, with the same abutment for the temporary crown, and it was tightened at the torque of 35 Ncm. Patients were recalled for a follow-up evaluation 12 months after surgery.