Sampling calculation was obtained by the G -Power 3.1 program considering a Beta error 0.8, and an alpha error 0.05, meaning a sample calculation of 25 patients per group per center, considering the drop-out reported in other published work ( 5%) was decided to increase to 30 the n sample size for each group per center. Coincident with the Odds Ratio of all clinical work whitening the past 10 years.