The plasma rich in growth factors (PRGF) was prepared using the Endoret® system following the manufacturer instructions (BTI Biotechnology Institute, Vitoria, Spain). The technique for transalveolar sinus floor elevation is explained elsewhere [15]. Briefly, conventional drills working at low speed (150 rpm) without irrigation was used to prepare the implant site. A frontal cutting drill was then introduced to prepare the last 1 mm of the implant alveolus. When a window (half of the sinus floor) was created, a well-retracted fibrin plug was introduced. The sinus floor could be opened further, if it was needed. A blunt hand instrument was introduced to push apically the fibrin membrane and to elevate the Schneiderian membrane, simultaneously. The area below the Schneiderian membrane was grafted by PRGF clot. Before implant insertion, the implant socket was irrigated with PRGF. The implants were inserted by a surgical motor at a torque value of 25 N cm. Then, the implant was completed seated with a calibrated torque wrench.

After completing the surgical and prosthetic phases, the patient was reviewed at 6 and 12 months during the observation period of the study.

Data collection and analysis were performed by an independent examiner (other than restorative dentist and surgeon). A descriptive analysis of the implant location, length, diameter, bone grafting, and marginal bone loss was performed by considering the implant as the statistical unit of analysis. Shapiro-Wilk test was selected as normality test. Mann-Whitney test was applied to compare the follow-up time, insertion torque, and proximal bone loss between the study groups. Patients’ age, sex, and medical history were also analyzed. The bone type was compared with Fischer’s exact test and the number of implant failures by χ² test.

The statistical significance level was 5% (p < 0.05). SPSS v15.0 for Windows statistical software package (SPSS Inc., Chicago, IL, USA) was used.