This case report describes the effect of complete denture abstention and subsequent rehabilitation with mandibular implant-supported overdentures (IOD) on masseter muscle thickness (MMT) in a 97-year-old patient. MMT was measured bilaterally using an ultrasound scanner during 1 year of wearing a conventional denture, after 101 days of voluntary denture abstention, and 3, 6, and 12 months after delivery of the IOD. MMT decreased by 17% during denture abstention following repeated implant surgery, and returned to 100% during the 12 months with the mandibular IOD. This case suggests that muscle bulk may be related to denture function.