To evaluate the comparative effects of air-turbine and electric handpieces on dental preparation, 60 premolars were categorized into four groups, each comprising 15 specimens, based on the preparation method employed: air-turbine handpiece (Group A), and electric handpiece set at rotational speeds of 200,000[Formula: see text]rpm (Group B), 50,000[Formula: see text]rpm (Group C), and 20,000[Formula: see text]rpm (Group D). Analysis revealed no statistically significant difference in the surface roughness of the preparations across the four groups ([Formula: see text]). Similarly, no significant variance was observed in fracture resistance among the groups ([Formula: see text]). However, a notable distinction was detected in the degree of microleakage following the aging test ([Formula: see text]), with veneers prepared using the electric handpiece at 200,000[Formula: see text]rpm demonstrating the lowest average microleakage. It is noteworthy that the surface roughness of the preparations and the veneers’ fracture resistance remained unaffected by the variations in preparation method.