## 2 Materials and Methods  
### Study Design  
This research protocol was reviewed and approved by the Institutional Review Board of Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea (KC23 RASI0246, approved 24 March 2023). This was a retrospective, non-randomized observational study. This study included seven participants (six males and one female) with a mean age of 52.3 \(\pm\) 8.0 years. All participants were treated at Seoul St. Mary's Hospital for the rehabilitation of sites with implant failure.  
Participants were allocated into three groups based on the clinical treatment they had already received, determined by the treating clinician's judgment at the time of care. Decisions regarding bone grafting and its timing were made individually, considering clinical factors such as bone loss extent, infection status, and patient-specific anatomical conditions. The participants were categorized into three groups based on the treatment approach following implant removal. In Group 1, no bone grafting was performed after implant removal (\(n=3\)). In Group 2, bone grafting was performed after implant removal, allowing for an adequate healing period before implant placement (\(n=2\)). In Group 3, bone grafting was performed simultaneously with implant removal (\(n=2\)).  
Implants were removed using forceps or an implant removal kit, followed by thorough debridement of the site (Figure 1A). In Group 1, after a sufficient healing period, a new implant was placed without bone grafting. In Group 2, bone grafting was performed after a sufficient healing period following implant removal. The defect was filled with deproteinized bovine bone graft material (Bio-Oss\({}^{\circledR}\), Geistlich Pharma, Wolhusen, Switzerland), ensuring its secure placement. If necessary, additional graft material was applied to both the buccal and palatal aspects to expand the ridge width. A resorbable collagen membrane (BioGide\({}^{\circledR}\), Geistlich Pharma, or Ossix, Dentsply Sirona, Charlotte, NC, USA) was carefully positioned over the augmented site to protect and stabilize the graft material, promoting optimal healing. In Group 3, bone grafting was performed simultaneously with implant removal (Figure 1B,C). The site was subsequently restored with dental implants (Osstem Implant Co., Ltd.) (Figure 1D,E).  
All study participants underwent cone-beam computed tomography (CBCT) imaging using InVivoDental software (Version 6.0.5, Anatomage, San Jose, CA, USA) (Figure 2). CBCT images were acquired and exported as DICOM files, which were then analyzed using InVivo software (Version 6.0.5) for precise measurements. The imaging parameters were configured as follows: a voxel size of 0.2 mm and a slice thickness of 0.2 mm. The field of view measured 16 \(\times\) 14.5 cm, with exposure settings of 85 kVp and 8 mA. CBCT imaging protocol was as follows. In Group 1, CBCT imaging was performed before implant removal (T0), after implant removal (T1), and after implant reinstallation (T2). In Group 2, CBCT imaging was performed before implant removal (T0), after bone grafting (T1), and after implant reinstallation (T2). In Group 3, CBCT imaging was performed before implant removal (T0), after implant removal and bone grafting (T1), and after implant reinstallation (T2).