It is extremely rare

Usually nipple sensation after breast augmentation is maintained. The procedure, however, does have the risk of temporary or permanent sensory changes. This can occur due to anatomical differences in the breast, surgical approach, or surgical technique. Normal nipple sensation,however, is the norm.

While most patients do NOT lose all sensation, some do experience changes in sensation (hypo or hypersensitivity) for 6 weeks to 6 months after breast augmentation.

Not necessarily, but it can happen. You diminish the risk by having experienced doctors do the operation.

That is very unusual unless your surgeons places the implants through a peri-areolar approach. Implants are most frequently placed through an inframammary approach (an incision along the underside of the breast) or in some cases through a transaxillary approach (armpit incision), and through these approaches, it is not a frequent occurrence (unless very large implants are placed).