“…In this study, a total of 24 drills in zirconia (Dental Tech snc Misinto, Milan, Italy) and 24 steel drills were used (Dental Tech snc Misinto, Milan, Italy), 6 drills for each group (Figures 1 and 2). The sample size was calculated by using a free software (6.0 ClinCalc LLC, North Chicago, IL, USA) available on the site http://clincalc.com/stats/samplesize.aspx considering a power of 0.80, an alpha error of 5% and an effect size of 0.84, based on a previous study [19]: a total of 20 implant osteotomies on bovine ribs for each study group (total 160 sites, 5 osteotomies for each rib) were necessary to achieve statistical significance for quantitative analyses of drill surface damage. All the drills, with the exception of Group 1 and 5 that were controls, were immersed in high protein concentration solutions (10% of fetal bovine serum) (Sigma Aldrich, Milan, Italy) phosphatebuffered saline for 10 min then they were rinsed in running water and scrubbed with a toothbrush made of nylon bristles in order to remove gross foreign material and were then subjected to the different treatments as follows and then analyzed.…”