On the day of surgery, patients were treated under local anesthesia.

Full-thickness crestal flaps were elevated with a minimal extension to reduce patient discomfort. The implant sites were prepared according to the procedure recommended by the implant manufacturer (JDentalCare, Modena, Italy).

Tapered narrow-diameter implants titanium grade 5 (2.75 and 3.25 mm diameter, respectively, JDIcon Ultra S and JDEvolution S, JDentalCare) with internal connection and sandblasted and acid-etched treated surface were used (Fig. 1a,b). No bone flattening was performed. The implants were inserted in the bone without any fenestration/dehiscence. The implant neck was positioned at the coronal marginal crest level. The operator was free to choose implant lengths (8, 10, 11.5, and 13 mm) and diameter (2.75 and 3.25 mm) according to clinical indications. One implant for each missing tooth was requested to be inserted. Healing abutments were attached, and implants were left to a nonsubmerged healing. Interrupted sutures were placed using a synthetic monofilament thread (Vycril, Ethicon, Johnson & Johnson, Somerville, New Jersey) and were removed after 10 days. After 3 months, all the implants underwent the standard prosthetic protocol and were loaded directly with definitive screw-retained or cemented multiple splinted crowns.

Primary outcome measures were as follows:

• Implant failure: evaluated as implant mobility and removal of stable implants dictated by progressive marginal bone loss or infection. The stability of each implant was measured manually by tightening the abutment screw with a wrench delivering a torque of 20 Ncm. Implant stability assessment was performed at delivery of definitive crowns (3 months after implant placement). After insertion of the definitive restorations, prostheses were not removed to assess clinical mobility of individual implants.

• Complications: any biological and prosthetic complication occurred at the implant site during the entire follow-up time were recorded and reported.