If the pocket dissection is precise
you can probably get away without drains. But logically, drains make sense when trying to keep the tissue in contact with the surface of your implant and drains will do this but they introduce a risk of infection as well. When pockets are adjusted down to fit the shaped implant, I would think its imperative a drain be used in that situation or your implant will be at considerable risk for rotation and malposition. But you can ask your clinic's surgeon why drains are not used when they were recommended when the implants first introduced.