Forty-eight patients were screened for eligibility, but six subjects were not included for the following reasons: five patients (10.4%) were hesitant to receive implant treatment, and one patient (2.1%) was treated with intravenous amino-bisphosphonates. Forty-two patients were then considered eligible and were consecutively enrolled in the study. All patients were treated according to the allocated intervention, no dropout occurred up to 1 year after loading, and the data of all patients were evaluated in the statistical analysis.

Patients were recruited and operated from October 2014 to January 2016.

Implants and subjects features

The follow-up focused on the time between implant placement and 1 year after loading. One hundred and twenty-four narrow-diameter implants (2.75 and 3.25 mm) inserted in a total of 42 subjects were included. The main baseline patient features are reported in Table 1.Patients were generally healthy, though 19 patients (45.2%) had medication-controlled hypertension and 11 (26.2%) patients had controlled type 2 diabetes. The mean age of the patients at the time of surgery was 61.3 years old (range 49–73). Seating torque values and the dimensions (diameter and length) of the inserted implants are listed in Table 2.Measurements of insertion torque were averaged at patient level and then group level. Average insertion torque was 46.6 Ncm (SD 11.8). Pain and discomfort from the surgical procedure appeared to be within the limits of a flapped implant placement. No incidences of abnormal bleeding or ecchymosis were observed.

Complications

Three patients (7.1%) had an episode of peri-implant mucositis, and they were treated with non-surgical debridement of the affected implants. All permanent bridges remained stable during the 12 months follow-up period.

Marginal bone level changes

The radiographic data are summarized in Tables 3 and 4. The group lost statistically significant marginal peri-implant bone at 6 months (−0.20; 95% C −0.14: −0.26, p < 0.0001) and 1-year post-loading (−0.47; 95% CI −0.29: −0.65, p < 0.0001), respectively. The marginal bone level changes were not different between the different implant diameters used, 2.75 and 3.25 mm (p = 0.786) (Table 4).