## 2 Case Report  
This study was approved by the institutional review board of the Armed Forces Capital Hospital (AFCH-21-IRB-004) and conducted in accordance with the tenets of the Declaration of Helsinki for research involving humans. A 55-year-old male patient with a smoking habit (10 cigarettes/day over 20 years) and a history of sinus surgery for chronic sinusitis 20 years ago visited our hospital for dental implant treatment. Clinical examination revealed severe periodontitis and mobility of all maxillary teeth, except the left central incisor (#21) and left premolars (#24 and #25: mild chronic periodontitis and mobility). Radiography showed severe bony defects in the anterior and molar regions and sinus haziness (Figure 1A,B). Considering the possibility of an oroantral fistula formation, extraction of the hopeless teeth (severity grade IV; complexity grade IV; tooth mobility degree \(\geq\) 2 [8]) with simultaneous reconstruction surgery using an autogenous bone graft was performed. To prevent overpressure and wound dehiscence due to the provisional dentures, the authors attempted to simultaneously place the implants with early loading on the premolars and anterior tooth. Figure 1: (**A,B**) Pre-operative radiographs showing generalized severe periodontitis and residual bone loss in the maxilla, with both sinusitis and oroantral fistula. (**C,D**) Simultaneous surgery with the extraction of hopeless teeth; the autogenous bone was harvested from the lateral ramus. (**E**) The autogenous graft was crushed. After extraction of the teeth and preparation of both sinus floors, the implants (o 4.5 \(\times\) 10.0 mm on #11, #14, and #15; o 4.0 \(\times\) 10.0 mm on #13, #22, and #23, Oststem TS III SA, Oststem, Seoul, Korea) were placed in the desired position for prosthetic rehabilitation. The lateral cortical bone of the mandibular ramus was harvested without bone marrow invasion (Figure 1C). The harvesting involved sagittal, coronal, and axial osteectomies using a micro-saw within the cortical bone. The thickness was confirmed by the ditching holes made with a round burr. The cortical bone was harvested from the occlusal part using a chisel and crushed to a particle size of 300-800 um using a bone mill in order to increase the contact area (Figure 1D,E). The autogenous bone was grafted around the implants and both posterior oroantal fistula. Titanium meshes (Retro Ti-matrix, Seumedi, Bucheon, Korea; thickness 0.3 mm, hole size o 1.7 and 3.4 mm) were used to fix the grafts. Concerning primary stability for early loading, the values of the stable implants (\(\geq\)40 N initial torque and \(\geq\)65 implant stability quotient (ISQ)) were determined by an Oststell mentor (Integration Diagnostic AB, Goteborg, Sweden) using a non-submerged protocol with a healing abutment connection. Tension-free sutures were achieved after adequate flap management, including incision release. Post-operation care was delivered via antibiotics (Mesexin, 500 mg tid, Hanlim Pharm., Yongin, Korea) and naproxen (Naxen F, 500 mg bid, Chong Kun Dang Pharm., Seoul, Korea) as anti-inflammatory analgesics for 1 week and 0.2% chlororexidine gluconate (Alpha-hexidine, 100 mL twice per day, Firson, Cheonan, Korea) for 2 weeks. With verified soft tissue healing at 2 weeks after the surgery, the submerged implants were considered for a provisional prosthesis with the confirmation of soft tissue healing (Figure 2A). The provisional prostheses were fabricated with polymethyl methacrylate (PMMA) resin and delivered with \(\geq\)30 N of torque at 4 weeks postoperatively (Figure 2B-D). Five months postoperatively, the provisional prostheses were changed to final prostheses. After five months with the final prostheses, we planned to place one of each implant on the maxillary molar areas. However, the patient wanted the implants to be placed in the same spaces as his natural teeth before their loss.