## 2 Materials and Methods
### Socket Preservation Procedure  
Patients who met the inclusion/exclusion criteria (Figure 1) were thoroughly clinically examined for the assessment of dental caries and periodontal health. Prior to the socket preservation procedure, patients underwent a preoperative CBCT scan to quantify bone volume. Once eligibility was confirmed and informed consent was obtained, a comprehensive oral examination was conducted to evaluate overall oral health and identify any pathologies requiring treatment prior to socket preservation and implant rehabilitation. Approximately 10 days before socket preservation and implant placement, all patients received professionally delivered oral hygiene, including debridement, as necessary. Prophylactic antibiotic administration included 2 g of amoxicillin one hour before surgery, or 600 mg of clindamycin in cases of penicillin allergy. Patients also rinsed with 0.2% chlorhexidine mouthwash for one minute before any surgical procedure. All surgical interventions were performed under local anesthesia with articaine and adrenaline (1:100,000). Intravenous sedation was optional. Atraumatic tooth extraction without flap elevation was performed, followed by curettage of the alveolus, assessment of alveolar integrity, and socket preservation (Figure 2). Post-extraction sockets were filled with heterologous bone substitute using natural equine bone granules (Bioactiva, Arcugnano, Italy) and covered with XC Collagen Xenomatrix (Bioteck S.P.A, Vicenza, Italy). The vacuum plasma surface treatment was performed using the ACTILINK reborn machine (Activelink reborn, Plasmapp Co., Ltd., Daejeon, Republic of Korea) with a customized holder (Figure 3), according to a published protocol [12]. The cycle time of the vacuum plasma surface treatment, named Vortex Plasma mode, was 30 s.  
Figure 1: Hopeless tooth after crown removal.  
Figure 2: Atraumatic tooth extraction, without flap.  
The surgical sites were then closed with Vicryl 4.0 simple sutures (Revello S.p.A, Verona, Italy) (Figure 4). After a healing period of three months, implant placement (Oss stem Implant, Seoul, Republic of Korea) was performed according to the manufacturer's instructions. Histological tissue samples were collected immediately before implant site preparation (see Sections 2.3 and 2.4). The implant sites were prepared freehand, without a surgical template, using drills of increasing diameter. Bone quality was subjectively categorized as hard, medium, or soft. The motor torque was set to 35 Ncm during implant insertion. Implants were placed 1.5 mm below the intact buccal bone, and an immediate loading protocol was adopted with a minimum insertion torque of 35 Ncm. Post-surgical analgesic treatment with ibuprofen 600 mg was prescribed as needed. All patients were strictly followed to evaluate complete healing. Three to four months after immediate loading, definitive impressions were taken, and within one month, a screw-retained, implant-supported, single metal-free crown was delivered. Periapical radiographs were obtained at the time of implant placement (Figure 5).  
Figure 4: Post-extractive socket filled with xenograft, covered with collagen xenomatrix.  
Figure 5: Periodical radiography before the treatment (**A**), after socket preservation (**B**), at crown delivery (**D**), and CBCT scan before implant placement (**C**).  
Figure 3: Heterologous bone substitute treated with plasma.