Yes Dental Implants Have Risk and side effects
When placing the implants it is theoretically possible to injure neighbouring structures like the inferior dental nerve, the sinus cavity and neighbouring roots. With the right technique and planning these risks are reduced to minimal.
Most of the implants are placed in local anaesthesia, thus with a decent medical history most of the adverse reactions, regarding local anaesthetics can be avoided.
In optimal circumstances, dental implants can work against the bone resorption of the edentulous jaws.