CATEGORY 92 AUSTRALASIAN DENTIST CLINICAL for ridge preparation was then seated in place and pressed firmly against the bone surface (Fig. 2A). The slots in the alveolar crest for the housing of the abutments were prepared using a cylindrical diamond bur (B&B Dental) with a diameter corresponding to the width of the slot. During the ridge preparation phases, especially if the IAN is very superficial, the patient may feel pain making it necessary to block the IAN. Supplementary material related to this article can be found online at doi:10.1016/j.ijom.2024.01.003. Once the housings for the implants had been made (Fig. 2B), the subperiosteal implant was inserted. The insetting of implants that run above the mental nerve is simpler and does not require complete isolation of the mental nerve. Otherwise, implant insertion is a bit more complex: the anterior arm is inserted vertically below the nerve and gently pulled forward with forceps. Once the nerve has been passed, the implant can be placed horizontally and moved forward to its final position. The correct fitting of the implant was then meticulously checked. Any poor fittings are generally related to inaccurate preparation of the housings for the abutments. The housings were finished in these cases before fixing the implant. Once a satisfactory fit was achieved, the implant was pressed firmly into place. Rigid fixation was performed with 2-mm diameter grade V titanium osteosynthesis screws (B&B Dental). In order to avoid damage to the IAN, the length of the screw was decided on the basis of the underlying bone thickness, which was evaluated during the surgical planning; this could vary from 4 mm to 10 mm. The 1.7-mm surgical bur used for the preparation of the holes could be equipped with a stop at a pre-calibrated height. If the screw did not reach sufficient tightening torque, a safety screw with a diameter of 2.3 mm was used. Each implant was fixed with at least four osteosynthesis screws (Fig. 2C). Following completion of the fixation, the mucosa was sutured after releasing the periosteum (Fig. 2D). All patients were prescribed postoperative antibiotic therapy (amoxicillin + clavulanic acid 1 g twice daily for 6 days) and analgesics. Delivery of the provisional prosthesis took place 10 days after surgery, after the sutures had been removed. The provisional prosthesis was fabricated based on a conventional precision impression and readapted as necessary during the following months to facilitate the conditioning and healing of the soft tissues. The final prosthesis was delivered 6 months after the surgery, once the soft tissues had been conditioned (Fig. 3). Evaluation protocol All patients underwent clinical and radiological follow-up, and any complications were recorded. The health of the soft tissues around the abutments was evaluated 6 months after the surgery, at delivery of the final prosthesis, and then every 6 months. Peri-implant bleeding on probing (BOP) was measured at six sites per abutment (mesiobuccal, mid-buccal, distobuccal, mesiolingual, mid-lingual, and distolingual) and classified into four grades as described by Mombelli24, from 0 (no bleeding) to 3 (heavy and profuse bleeding upon periodontal probing). The degree of exposure of the implant structure was also assessed, and classified as follows (score range 0–5): no exposure of the structure (score 0), exposure of the vertical arm of the abutment (score 1), exposure of the horizontal arm of the implant (score 2), exposure of the horizontal arm and A C B D Fig. 2. Case 11 (female, age 54 years): (A) placement of the surgical guide for the preparation of the alveolar ridge; (B) housings for abutments milled into the alveolar bone; (C) subperiosteal implant placed and fixed; (D) surgical access sutured. Fig. 3. Case 9 (female, age 64 years): (A) and (B) show intraoperative views; (C) and (D) show the final prosthesis delivered. A C B D
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