Alveolar Bone Augmentation Using Octacalcium Phosphate and Collagen Composite with Custom-Made Titanium Mesh: A Case Report

Introdcution

Extensive bone augmentation is necessary for dental implant treatment in patients with bone loss due to traffic accidents, tumor resection, or congenital disorders [1–3]. Autologous bone grafts are usually used for such cases. Cortical-bone grafts from the mandibular ramus or chin are preferred for vertical augmentation of the alveolar bone because they can resist compression due to mechanical stress [4,5]. Similarly, bone-substitute materials used for vertical bone augmentation should have good osteogenic ability and mechanical strength to resist mechanical stress [6]. Therefore, vertical bone augmentation using artificial materials alone is difficult.

Octacalcium phosphate (OCP) is a precursor of biological crystals in the bones and teeth [7] and has been recognized as a good bone substitute because of its higher osteoconductivity and biodegradability compared to hydroxyapatite or beta-tricalcium phosphate [8,9]. Particularly, OCP and collagen composites (OCP/Col) facilitate bone regeneration better than OCP alone [10], and OCP granules in OCP/Col are completely converted to bone-like apatite within 6 months after implantation [11]. In clinical trials, OCP/Col has been applied for bone augmentation after sinus floor elevation, socket preservation for dental implant treatment, and for filling defects due to cystectomy and alveolar clefts [12,13]. In Japan, OCP/Col has been commercially available as a bone-substitute material since May 2022.

Titanium mesh has been used for jaw reconstruction with autologous bones because of its mechanical strength and ability to provide a specific bone shape, retaining the grafted bone [14]. Due to its shape retention and strength characteristics, it is also sometimes used in cases of fractures [15].

OCP/Col is a flexible material with low mechanical strength [16]. However, a previous animal study demonstrated that vertical bone augmentation using OCP/Col is possible by maintaining the graft in the defect area using a titanium mesh [17]. To prevent infection, bone augmentation using OCP/Col is considered advantageous due to its excellent biodegradability and bone regeneration ability and not causing a secondary invasion into the body by autologous bone harvesting. Herein, we report a case of bone augmentation for dental implant treatment using OCP/Col with titanium mesh in a maxillary anterior alveolar-bone defect caused by a traffic accident.

Case Report

An 18-year-old man with loss of the bilateral maxillary central incisors due to a traffic accident 8 years prior was followed up at a local dental clinic. After completion of jawbone growth, dental implant treatment was planned; however, it was expected to be difficult because of alveolar bone loss. Therefore, he was referred to our hospital. Clinical examination at the first visit revealed missing bilateral maxillary central incisors, and insufficient alveolar height and width (Figure 1A, 1B). Temporary resin teeth were placed in the edentulous region. The patient reported no relevant medical history. Orthopantomography (Veraviewepocs 2D, MORITA Corp., Tokyo, Japan) and cone beam computed tomography (CBCT; KaVo OP 3D Vision V17, KaVo Dental Systems Japan G.K., Tokyo, Japan) revealed alveolar-bone loss on the labial side and a slightly insufficient alveolar crest height (Figure 2A–2C). The alveolar-bone width was 3.5 mm. The mucosa in the edentulous region was normal, without scarring. The patient was informed that there was insufficient bone volume for dental implant placement, and consent was obtained for bone augmentation surgery followed by dental implant placement. A virtual surgical plan based on CBCT the data, prepared using Volume Extractor® (i-Plants Systems Corp., Iwate, Japan) and Geomagic Freeform® (3D Systems, Rock Hill, SC), revealed a lack of labial alveolar bone for ideal implant placement (Figure 3A). Image analysis revealed that approximately 2.0 cc of bone graft was required (Figure 3B). Therefore, bone augmentation using OCP/Col and a titanium mesh was planned prior to dental implant placement. A three-dimensional (3D) model of the ideal alveolar-bone morphology was prepared using a 3D printer (Straumann® CARES®P20+, Straumann, Basel, Switzerland), and a custom-made titanium mesh was prepared by adapting a preformed mesh sheet (Universal mesh, Stryker Japan, Tokyo, Japan) on the 3D model (Figure 3C, 3D). A disc-type OCP/Col (Bonarc®, Toyobo, Co. Ltd., Osaka, Japan) was purchased. Since OCP/Col discs are 1.5-mm-thick and 9 mm in diameter, and the volume of each disc is approximately 0.1 cc, 20 OCP/Col discs were prepared.

Surgery was performed under local anesthesia with intravenous sedation. The gingiva and periosteum were ablated up to the piriform apertures. First, the titanium mesh was positioned and fixed using 2 screws (MINI PLATING MODUL Screws, Stryker Japan, Tokyo, Japan). Next, the titanium mesh and screws were removed, and partial bone decortication was performed using a round bur (Figure 4A). Several OCP/Col discs were placed in the bone-deficient area, and the titanium mesh was repositioned using screws (Figure 4B). Subsequently, the remaining OCP/Col discs were inserted under the titanium mesh to fill the space (Figure 4C). The periosteum was incised to allow flap extension, and the wound was closed using VICRYL® Plus (Johnson & Johnson K.K., Tokyo, Japan) (Figure 4D). To prevent wound exposure, the patient was instructed to eat only soft food for 7 days, and the upper lip was bandaged with tape for 2 days after surgery. For postoperative pain, loxoprofen sodium hydrate (60 mg) was administered orally as needed. Cefmetazole sodium (2 g/day) was administered intravenously for 2 days, followed by amoxicillin hydrate (750 mg) administered orally for 3 days for infection prevention. No postoperative infection or wound exposure was observed, and the patient was discharged from the hospital on the second postoperative day. The wound remained stable when checked at 7, 14, and 30 days after surgery.

Cone beam computed tomography (CBCT) performed at 3 months postoperatively showed low radiopacity under the titanium mesh. However, at 6 months postoperatively, the radiopacity increased to a level similar to that of the surrounding alveolar bone. No abnormality was observed in the operative region (Figure 5A–5C), and the alveolar-bone width was 7.0 mm. Subsequently, the titanium mesh was removed under local anesthesia, and the alveolar bone morphology was confirmed to replicate that in the simulation. Two dental implants (Straumann® BLT NC SLActive® 3.3×10 mm, Straumann, Basel, Switzerland) were placed using a dynamic computer-assisted system (X-Guide, Nobel Biocare Services AG., Zurich, Switzerland), cover screws were inserted, and the wound was closed (Figure 6A, 6B). After 6 months, a second surgery was performed, and the cover screws were replaced with healing abutments. The final prosthesis was inserted 3 months later. The area of the maxillary anterior teeth was restored in terms of both occlusion and aesthetics (Figure 6C).

Discussion

Bone augmentation is sometimes necessary for dental implant placement. If the bone deficiency is small, artificial bone substitutes can be used; however, if the bone deficiency is large, autologous bone augmentation is preferred because of its excellent bone regeneration ability [18]. However, autologous bone grafting has disadvantages such as limitations on the amount of bone that can be harvested and need for a second operative site [18]. Various techniques have been attempted for bone augmentation with autologous bone in patients with large alveolar bone defects. Bone augmentation is frequently performed by harvesting bone from secondary sites, such as the mental region or the ramus of the mandible [19]. Instead of harvesting bone from a secondary site, a modified shell technique in which bone is harvested from the apical area of the same surgical field has been reported [20]. In both cases, the procedure involves the additional invasive step of bone harvesting. Artificial bone substitute materials have no limitations in terms of the amount that can be used. OCP/Col has good bone regeneration ability compared with other artificial bone substitutes [21,22]. Furthermore, OCP/Col and autologous bone have equal affinities for dental implant bodies [23]. Therefore, OCP/Col was selected instead of autologous bone in this patient with an extensive alveolar-bone defect, and the ideal alveolar-bone shape was restored 6 months after surgery. The radiopacity of the newly formed bone by OCP/Col was almost the same as that of the surrounding bone at 6 months after surgery. The conversion of OCP/Col to mature bone was confirmed almost 6 months after implantation in animal and clinical studies [11,24]. The conversion of OCP to biological apatite was also confirmed 6 months after implantation by Fourier transform infrared spectroscopy in animal and clinical studies [11,25]. Since there is no residual foreign matter that could cause infection, the same affinity as that of autogenous bone can be expected.

Extensive vertical bone augmentation is difficult because of the possibility of a lack of mucosal coverage and graft resorption due to mechanical stress [26]. In our patient, the mucosa was expected to expand because of the periosteal incision; however, graft resorption owing to compression by the covering mucosa was also expected. A titanium mesh is used to maintain the created space or prevent resorption when using particulate autologous bone or artificial substitutes [14]. Extensive bone augmentation using OCP/Col and a titanium mesh has been reported in a previous animal study [17]; therefore, we believed that this method could be applied in this case. The procedure was successful because a certain amount of alveolar bone height remained; however, if the height and thickness are insufficient, achieving coverage by expanding the periosteal incision may not be possible. Furthermore, since titanium mesh is a foreign body, infection can easily occur if the closure is insufficient.

Preoperative simulation is important in dental implant treatment to restore the ideal occlusion, check the surrounding anatomy, and determine the extent of bone augmentation in patients with bone deficiency [27]. The simulation confirmed the amount of bone augmentation required, and the required number of OCP/Col discs were prepared based on this evaluation. The 3D model was also useful for pre-shaping the titanium mesh [15]. These preoperative preparations likely led to more satisfactory patient outcomes. In this case, the patient was very satisfied with both the cosmetic and functional improvements. Recently, there have been research reports on using artificial intelligence for esthetic evaluation [28], which may further improve patient satisfaction.

OCP/Col exhibits minimal radiopacity on plain radiographs [10]. Moreover, because of the properties of collagen, OCP/Col can adhere to the surgical field by adsorbing blood and has a hemostatic effect [11]. In this case, OCP/Col could be easily grasped with tweezers and placed in the defect and did not migrate to the surrounding area. This led to a reduction in surgical time and burden on the surgeon.

However, applying the same technique in other cases may be difficult. If more bone augmentation is required than in the present case, complete mucosal coverage would be difficult, and infection might occur owing to wound dehiscence. Therefore, case selection considering the risk of infection and condition of the surrounding tissues is advisable.

Conclusions

In this patient, an extensive alveolar bone defect was reconstructed using OCP/Col and a titanium mesh to achieve an ideal alveolar shape. Subsequently, the occlusion and esthetics were restored using implant-supported restorations, and the patient’s quality of life significantly improved. The findings in this case suggest that a combination of OCP/Col with a titanium mesh is effective even for extensive bone augmentation. However, further observation is required regarding the survival of implants in bone-augmented areas using OCP/Col.