## 2 Materials and Methods
All legible radiographs were uploaded in jpeg format to an image analysis software package (Imagej; National Institutes of Health, [[http://imagej.nih.gov/ij](http://imagej.nih.gov/ij)]([http://imagej.nih.gov/ij](http://imagej.nih.gov/ij)), accessed on 27 August 2021) that was calibrated using the known length or diameter of the dental implants and displayed on a 24 in LCD screen (iMac, Apple, Cupperto, CA, USA) and evaluated under standardized conditions (ISO 12646:2004). The marginal bone levels were determined from linear measurements performed by two independent (semi-blinded) trained examiners on each periapical radiograph, from the mesial and distal margin of the implant neck to the most coronal point where the bone appeared to be in contact with the implant. Quality of life was assessed by the Oral Health Impact Profile (OHIP-19; [PERSON] and [PERSON] 2002) questionnaire, which was completed by the participants. The questionnaire consisted of seven subscales FL = Functional limitation, P1 = Physical pain, P2 = Psychological discomfort, D1 = Physical disability, D2 = Psychological disability, D3 = Social disability, H = Handicap, with two to three questions each. Participants chose from five possible responses for each question as follows: 4 = very often; 3 = fairly often; 2 = occasionally; 1 = hardly ever; 0 = never/do not know. Lower OHIP total scores were suggestive of improvement in oral health-related quality of life. The questionnaire was administered before treatment and one month and one year after definitive prosthesis delivery by a blinded examiner. Bleeding index and plaque index were evaluated at four sites around each implant-abutment interface at baseline and at the one-year after loading examination with a dedicate periodontal probe. Statistical AnalysisStatistical analysis was developed in order to find differences between groups. A priori sample size calculation was performed on-line ([[https://clincalc.com/stats/samplesize.aspx](https://clincalc.com/stats/samplesize.aspx)]([https://clincalc.com/stats/samplesize.aspx](https://clincalc.com/stats/samplesize.aspx)), accessed on accessed on 27 August 2021) basing of a preliminary report [6], given: alpha 0.05 beta 0.2; and power 0.80. The total sample size was 44 patients for each group. Twenty centers were involved with six patients each. Of these, three patients to be treated with two implants, and same number of patients to be treated with three implants. Data was planned to be collected at 1, 3, and 5 years after loading. Data were recorded in a spreadsheet (Numbers for Mac OS X). A statistician with expertise in dentistry analyzed the data using the same software. Descriptive analysis was performed for numeric parameters using mean \(\pm\) standard deviation with confidence interval (95% CI). Differences in the proportion for dichotomous outcomes (patients with implant failures, prosthesis failures, and complications) were compared using the Fisher's exact. Differences of means at patient level for continuous outcomes (OHIP, marginal bone loss, BoP. and PI) were compared by independent sample t tests. All statistical analyses were performed at patient level and conducted at a 0.05 level of significance.