Patient KR, a 45-year-old man. (a) The missing lower-right molars were replaced with 2 hollow-screw implants. (b) After 3 years, a bony defect developed around the most posterior implant. (c) Conservative measures (ultrasonic curettage and chlorhexidine irrigation) failed to arrest the lesion's development, which, in 3 months, progressed to the state as shown. At that time, an open-flap debridement and disinfection was performed. (d) Eventually, the lesion healed to about 80% of the original bone level