## 2 Material and Methods  
Seventy-eight patients were consecutively treated between 2009 and 2017 at the Dental Clinic, Department of Medicine and Surgery, University of Milan, Italy. The fundamental principles of the Declaration of Helsinki were followed in the conduction of the study. Before participating in the study, all patients signed a specifically designed consent form. No ethical committee document was provided as the reported treatments and the follow-up procedures only consisted of standard treatments and control visits.  
Inclusion criteria were as follows: partial or complete edentulism; residual ridge volume of at least 3.3 mm in diameter and 8 mm in length as evaluated both clinically and radiographically; a favorable relationship with respect to the opposing dental arches; each dental implant included in the measurements needed a minimum 5 year follow-up. Only one type of implant-supported restoration for each patient was included in the present study. There was a yearly follow-up visit, in which oral hygiene control was carefully checked.  
The following exclusion criteria were considered: active periodontal disease, heart disease, coagulation or leukocyte diseases, metabolic disorders, radiotherapy in the head and neck area, parafunctions such as clenching or bruxism, a smoking habit (more than 10 cigarettes per day), alcohol or drug abuse.  
Patients were restored with implants with an internal-conical-connection (Astra Tech, Molndal, Sweden), which supported fixed prostheses.  
Peri-implant tissues were evaluated for concerns regarding probing pocket depth, bleeding on probing (bleeding index score of 0 to 3), and plaque index scores (on a scale of 0 to 3) [5].  
Intraoral radiographs were taken using the paralleling technique to control projection geometry, with exposure parameters of 65 to 90 kV, 7.5 to 10 mA, and 0.22 to 0.25 seconds [5]. They were subsequently stored on a personal computer and analyzed using the program ImageJ (US National Institute of Mental Health, Bethesda, MD, USA) to determine bone level changes. Peri-implant bone resorption was assessed both mesially and distally, taking the implant head as a reference point. Radiographs were taken at baseline (loading time) and at the 5 year follow-up visit, which were analyzed and compared to verify any change in the peri-implant marginal bone level (Figure 1). A radiographic control was performed during the yearly follow-up visits as well.  
Several reference measurements were also considered: (i) implant neck diameter; (ii) implant length as the distance between the implant neck and the most apical point of each implant, along an ideal line running parallel to the implant axis. All measurements were performed by a single calibrated operator (A.P.). Calibration consisted of three-time measurements at three different time points by assessing fifteen radiographs with another author (D.L.) acting as reference examiner. Subsequently, intra-examiner and inter-examiner reliability were calculated (k = 0.90 and k = 0.85, respectively).  
After a 3 month submerged healing, transmucosal healing abutments were connected at surgical re-entry. Hence, pre-prosthetic evaluation was performed 3 months after implant placement. Two weeks after surgical re-entry, an implant impression was taken, and a provisional restoration was screwed into position. Therefore, after maturation of the peri-implant soft tissues (2-3 months after provisional delivery), a second implant impression was taken for the final implant-supported restoration. Definitive abutments were screwed into position using 35 Ncm of torque. For all the fixed prostheses, a platform switching connection between fixture and abutment was provided. Cemented prostheses were fixed with zinc oxyphosphate cement or zinc-eugenol oxide cement, while screw-retained prostheses were secured by applying a 15 Ncm torque to the abutment framework screw using a manual torque driver.  
Figure 1: Radiographs performed after implant placement, at baseline (time of loading) and at the 5 year follow-up visit.