The primary endpoint was a change of crestal bone level between implant surgery (baseline) and final restoration (6 months), assessed by measuring the distance from the implant shoulder to the first bone-to-implant contact both mesially and distally to the implant.

Bone level was measured by a single reader on standardized periapical radiographs taken at baseline (day 0), suture removal (7–14 days after surgery), provisional restoration, final restoration, and at the 12-month follow-up. Radiographs were standardized by using customized film holders. A commercially available film holder was employed (e.g., System (Dentsply Rinn, Elgin, IL, USA)), RWT® window x-ray system (Kentzler-Kaschner Dental, Ellwangen, Germany) or similar). The film was placed almost parallel to the implants. Indentations of the incisal edge of the implant and of the neighboring teeth (where possible) were taken with impression material to improve reproducibility. The customized radiographic holder was fabricated by putting autopolymerizing resin to the biting plate of the film holder and adapted its shape to the patient dentition in order to standardize the position of the X-ray film. The radiograph was exposed once the resin had polymerized, and the stent removed and stored for future use.

Secondary endpoints included implant survival and success rates, changes in crestal bone level between baseline and 12 months, and patient satisfaction. Implant success and survival were assessed at suture removal, provisional restoration, final restoration, and at the 12-month follow-up. Implant survival was defined as remaining of implant, and implant success was defined according the criteria by Buser et al. [40], i.e., absence of pain, foreign body discomfort or dysesthesia, absence of recurrent peri-implant infection with suppuration, absence of implant mobility, and absence of continuous peri-implant radiolucency.

Patient satisfaction was evaluated at the final restoration and 12-month follow-up visits by asking the patients to rate their assessment of six parameters: prosthesis comfort, appearance, ability to chew, ability to taste, general satisfaction, and patients substantial feeling for adaptation. Patients rated their assessment on a five-point scale (highly satisfied, satisfied, no opinion, dissatisfied, highly dissatisfied).