In selecting graft materials for area with alveolar bone defect, considering the osteogenic potential of the graft, its resorbability, and the extent of the bone defect is crucial. For extensive defect equivalent to ≥ 3 teeth, pre-implant bone augmentation is typically necessary. In these cases, an autogenous bone graft with good osteogenic capacity should be used¹⁾.

Autogenous bone grafts have been widely used. The main advantages of these grafts include fast healing rate and high predictability in bone regeneration owing to the good osteogenic effect. However, its limitations include potential complications at the donor site, unpredictable graft resorption, limited bone volume, the necessity for additional surgical sites, and the technical complexity of harvesting procedures. When substantial graft volume is required, intraoral donor sites such as the mandibular symphysis, anterior nasal spine, mandibular ramus, palatal bone, maxillary tuberosity, and zygomatic alveolar ridge can be utilized²⁾. Extraorally, the iliac crest and tibia are viable options³⁾.

The tibia offers a simpler procedural advantage compared to other extraoral sites. The operation time is about 20∼30 minutes, and 10∼25 cm² of particulate autogenous cancellous bone can be achieved. Additionally, the donor site at the lower limb can immediately bear weight post-surgery, with patients typically experiencing minimal pain or functional impairment.

This study demonstrated two cases in which the medial aspect of the tibia was used as a donor site for obtaining cancellous bone. The bone was then grafted into extensive alveolar defects of ≥ 3 teeth, followed by subsequent dental implant placements.

The patella, tibial head, fibular head, Gerdy's tubercle, tibial tuberosity, and tibial ligament of the left lower extremity were marked prior to surgery. A medial approach was then initiated by making an incision approximately 3 cm in length, slanting downward from the tibial tuberosity, avoiding the joint surface.Subcutaneous tissue and the periosteum were dissected using instruments such as Bovie electrocautery and Metzenbaum scissors to expose the tibia. A 2 cm×2 cm bone window was then created using a fissure burr, and cancellous bone was harvested using a bone curette. The donor site was packed with five hemostatic agents(Surgicel, Ethicon, New Jersey, United states of America), followed by suturing the periosteum and subcutaneous layers using 2-0/3-0/4-0 Vicryl sutures, and the skin was closed using 5-0 Ethilon sutures (Fig. 1).

Figure 1. Medial approach technique of tibial bone graft. (A) Anatomy of the tibial region. (B) A 3-cm skin incision, angled medially from the tibial tuberosity. (C, D) The subcutaneous tissue and periosteum are dissected to expose the tibia. (E) A bone window approximately 2 cm×2 cm is created. (F) Cancellous bone is harvested using a bone curette. (G) The harvested cancellous bone. (H) Donor site after bone harvesting. (I) Surgical packing is performed. (J) The periosteum and subcutaneous tissues are sutured. (K) The skin is sutured.

1. Case 1

A 20-year-old male patient visited to the emergency department with facial trauma from an autobicycle traffic accident. The patient had no relevant medical history. Physical examination revealed avulsion of teeth #11,12,13,21, crown fractures of teeth #14,22, and a fracture of the maxillary anterior alveolar bone. Additionally, a fracture at the symphysis of the mandible was diagnosed (Fig. 2).

Figure 2. Post OP panoramic and computed tomography image reveal extraction of maxillary anterior region and bone grafting in the alveolar bone area. (A) Post OP panoramic image. (B, C) Post OP computed tomography image.

Accordingly, open reduction and internal fixation under general anesthesia were planned for the fracture in the mandible. A tibial bone graft was planned for the alveolar bone fracture in the anterior maxilla, and implant prosthetic treatment was planned for the tooth defect. Therefore, a tibial bone graft was performed in the maxillary anterior region (#13–21 area) for osteogenesis, and implants were placed in #11,13,14,21 at 5 months postoperatively.

The surgical procedure was as follows:

To minimize bleeding at the surgical site, 1:100,000 lidocaine with epinephrine was injected into the area. An incision line extending medially and superiorly from the tibial tubercle was planned, followed by a 2-cm incision using a #15 blade. Dissection was then performed using Bovie electrocautery and Metzenbaum scissors. Cortical bone was removed using a bone scoop, and approximately 10 cc of cancellous bone was harvested. Hemo-static agents were then placed in the donor site before suturing (Fig. 3, 4).

Figure 3. Pre OP panoramic and computed tomography image reveal alveolar bone fracture, tooth loss, and tooth fractures in the anterior maxilla. (A) Pre OP panoramic image. (B, C) Pre OP computed tomography image.

Figure 4. Surgical photograph of case 1. (A) Elevation of a flap in the anterior maxilla. (B) Bone graft performed. (C) Wound closure.

At 5 months after bone graft, sufficient bone formation for implant placement was confirmed (Fig. 5). Four implants were then placed in the #11,13,14,21 regions, following standard procedures. A 4-mm diameter, 13-mm long implant was placed in the #11, while 4.5-mm diameter, 13-mm long implants were placed in the #13,14,21. The patient underwent prosthetic treatment approximately 4 months after the implant placement. Panoramic and periapical radiographs taken 21 months after tibial bone graft, shows stable bone levels (Fig. 6).

Figure 5. Panoramic and computed tomography image at five months post OP reveal sufficient bone formation for implant placement in the maxillary anterior region. Thus, implant placement was planned. (A) Panoramic image at 5 months after OP. (B) Computed tomography image at 5 months after OP.

Figure 6. Panoramic and periapical images taken 12 months after bone graft. The images taken after implant placement confirm that the implants are well-maintained. (A) Panoramic image at 12 months after OP. (B, C) Periapical image at 12 months after OP.

2. Case 2

A 59-year-old male patient was referred from a local clinic to our outpatient department for treatment of cystic lesion in the mandibular anterior region. The patient had a history of taking antidepressants and anxiolytics. Clinical examination revealed cystic fluid discharge from the gingival sulcus of tooth #33. Panoramic radiograph showed a displaced #32 tooth and a well-defined circular radiolucent area approximately 3 cm in diameter from #33 to 43 (Fig. 7). Thus, cyst enucleation under general anesthesia was planned, followed by a tibial bone graft at the enucleated site. Subsequently, prosthetic implant treatment was planned for the tooth defect area (Fig. 8, 9).

Figure 7. Pre OP panoramic, periapical and computed tomography images. (A, B) A cystic lesion was observed below the roots in the mandibular anterior region. (C) In computed tomography image, approximately 22 mm×15 mm radiolucent lesion was observed.

Figure 8. Panoramic and periapical images taken 2 months after bone graft. The bone defect area is filled with harvested tibial bone following cyst enucleation. (A) Panoramic image at 2 months after OP. (B) Periapical image at 2 months after OP.

Figure 9. Surgical photograph of case 2. (A) Incision line marking. (B) Flap elevation. (C) Removed cystic lesion. (D) Bone defect after cyst enucleation. (E) Tibial bone graft was performed. (F) Wound closure.

The surgical procedure was as follows:

To minimize bleeding at the surgical site, 1:100,000 lidocaine with epinephrine was injected into the area. An incision line extending medially and superiorly from the tibial tubercle was planned, followed by a 2-cm incision using a #15 blade. Dissection was then performed using Bovie electrocautery and Metzenbaum scissors. Cortical bone was removed using a bone scoop, and approximately 10 cc of cancellous bone was harvested. The mandibular anterior incisors #33–43 were then accessed, and an alveolar crest incision and intrasulcular incision were performed to elevate the flap to expose the dehisced cortical bone and the cystic mass. Cyst enucleation was then performed and specimen was sent for a biopsy. After peripheral ostectomy, the cancellous bone harvested from the tibia was grafted into the site of the cyst removal, and the wound was closed (Fig. 10). A subsequent incisional biopsy confirmed an odontogenic keratocyst.

Figure 10. Post OP computed tomography images. (A) 1 month after surgery. (B) 3 months after surgery. Ossification is observed after bone grafting.

At 4 months after the cyst enulceation, three implants were placed at sites of teeth #31,33,41. Implant placement was conducted according to standard procedures. A 3.5-mm diameter, 13-mm long implant was placed for the #41, while 4.0-mm diameter, 13-mm long implants were placed for the #31,33. The patient underwent prosthetic treatment at 6 months after the implant placement (Fig. 11).

Figure 11. Panoramic and periapical images taken after bone graft and implant placement. (A) Panoramic image at 12 months after bone graft and 8 months after implant placement shows bone formation in the defect area and the stability of the implant. (B) Periapical image at 18 months after bone graft shows sufficient bone levels to sustain the implant.

Bone healing mechanisms involve three processes. First is osteogenesis, where new bone formation occurs directly through osteoblasts derived not only from the graft, but also from the recipient site, observed only with autografts. Second is osteoinduction, where bone formation proteins such as bone morphogenic proteins (BMP) stimulate undifferentiated mesenchymal cells in the recipient site to differentiate into chondroblasts or osteoblasts, evident in autografts and allografts. The third is osteoconduction, where the graft is absorbed while new blood vessels and osteoblasts from the surrounding bone migrate into the graft, transforming it gradually into new bone, observed in xenografts and synthetic grafts⁴⁾. In general, bone tissue is healed by osteoconduction, which is described by a phenomenon called creeping substitution or creeping formation. New bone formation primarily originates from osteoblasts derived from the recipient's host bone or part of its periosteum rather than the graft. The grafted bone serves as a scaffold where this new bone can deposit. This process is known as osteoconduction, where the grafted bone gradually integrates with the host bone, starting from the areas in contact. This gradual replacement process is referred to as creeping substitution⁵⁾. Newly formed bone is evident radiographically and functionally as new bone stock once completely integrated. This ongoing replacement, through bone resorption and deposition, continues until the grafted bone is completely replaced by new bone⁵⁾.

Bone graft materials are classified into autografts, allografts, xenografts, and synthetic grafts. The prognosis of bone grafting, even when used to fill bone defects, can vary depending on the characteristics of the materials used and the local and systemic condition of the patient⁶⁾. Among bone graft materials, autografts are considered the best option due to their ability to actively form bone through the direct osteogenic action of living osteoblasts and the osteoinductive activity of BMPs, in addition to facilitating passive bone formation through osteocon-duction. Further, they do not elicit an immunorejection response and heal rapidly, making them the gold standard in bone grafting³⁾. These mechanisms were evident in our case, as cortico-cancellous complex formation was observed several months postoperatively (Fig. 12).

Figure 12. Newly formed cortico-can-cellous complex on postoperative computed tomography images. (A, B) Computed tomography images at 5 months after OP (Case 1).

The iliac crest cancellous bone has been a preferred autograft source for many oral surgeons. While iliac crest allows the harvesting of a substantial amount of bone, it may also be associated with complications such as donor site pain, scarring, potential for nerve or joint damage, and risks of growth disturbances⁷⁾. A more complication-spared donor site is the tibia. According to Hughes et al.⁸⁾, tibial bone grafting has several advantages. First, it is a relatively simple surgical procedure that can be performed under local anesthesia, allowing fast discharge, possibly without the need for hospital admission. Second, the operation time is usually 20∼30 minutes. Third, a sufficient amount of cancellous bone can be harvested (10∼25 cm²) for reconstructing intraoral bony defects. Fourth, the donor site in the leg can bear weight immediately after surgery, with patients seldom complaining of pain or functional impairment. Finally, serious complications of tibial grafting are reported to be between 1.3% and 3.8%, which is lower compared to approximately 10% for iliac crest grafts⁹⁾. Although the risk is low, there remains a possibility of fracture at the donor site due to weight-bearing. To prevent such complications, patients should be advised to avoid weight-bearing for at least 6 weeks and refrain from engaging in sports for at least 3 months. Additionally, meticulous hygiene care of both the recipient site and the donor site is essential for prevention of infection⁸⁾. Furthermore, since a separate donor site is required, the procedure may takes longer than when using other bone graft materials, and there is a potential for scarring at the donor site. Therefore, these limitations should be considered when choosing the surgical method.

Two approaches can be used for these tibial grafts: medial and lateral. Traditionally, the lateral approach has been used for harvesting bone from the tibia. However, this approach places the surgical site in close proximity to various anatomical structures, including the peroneal (fibular) nerve, lateral inferior genicular artery, lateral superior genicular artery, anterior tibial artery, and patellar tendon, which increases the risk of damaging these structures. In contrast, the medial approach is relatively farther from these critical anatomical structures and positions the bone closer to the skin surface, reducing the risk of structural damage¹⁰⁾.

The tibia can be a preferable option over the ilium for extensive autogenous bone grafting. Particularly, the medial approach carries a lower risk of damaging anatomical structures and allows for easy harvesting of a comparable amount of bone¹¹⁾. The clinical cases described in this case series involve tibial bone graft for extensive bone defects of ≥ 3 teeth or larger areas resulting from trauma or benign lesions. They confirm that sufficient bone volume was obtained after surgery, aiding in subsequent implant prosthodontic treatments.