Sample size
Using ISQ values as the objective variable of the study and assuming an overall standard deviation of all implants less than 7.5 units based on previous studies [A total of 108 were consecutively admitted in the study following a scheme of balanced randomization using a computer-generated randomization sequence. Each participant was randomized assigned (1:1 ratio) to one of the 3 treatment groups, so 36 implants were placed with the underpreparation technique (group 1), 36 implants with the expander technique (group 2), and 36 implants using conventional drilling (group 3).