Ct dental scan showed i had enough bone 17 mm for #12,#13 implant. do you still need to add bone crafting because of the bone curvature in that area?

Maybe: You may have enough height of bone, but if you don't have enough width a bone graft may be necessary. It is also important that the implant are placed where they need to be so that there is enough room between them, adjacent teeth and the opposing dentition.

Height & Width: You need enough height and width of bone to place an implant. If the CT scan shows you have enough bone in all directions, then you do not need bone grafting.

Not uncommon: CT scanning implant procedures can be planned in detail before any surgery takes place. Even so, CT scans,sometimes, do not provide 100% information relative to whether or not primary stability will be achieved without bone grafting.