Dental Implant Maintenance

Dan, a dentist, asks:

I am having a hard time getting my dental implant patients to return for regularly scheduled routine maintenance of their implants.

Most of my dental implant patients are wearing a complete maxillary denture
and a mandibular implant retained overdenture. I charge them the same
fee that I charge for a routine prophy. I schedule a recall every 4
months. What are you doing? Are you bringing them back in every 4
months for routine implant maintenance? How are you getting them back in for maintenance? Thanks for your suggestions.