Actually, it is easy. I do this often & vice versa. First find out if your implants were placed on angles (despite having bone, some doctors don't put them in straight; not a fan since I place them in straight). Second, find out if the implant brand can have Zest attachments placed into them. You will then need a new set of teeth. I have several examples. Good luck justbeckyg
It depends on the placement and position of the implants. The abutments which connect the implants to the bridge would have to be changed. Also, the bridge would likely have to be converted to an overdenture. The All-on-Four bridge is the most ideal option.