Dental implant technology is well acknowledged as an ideal prosthetic treatment for edentulous or partially edentulous individuals. However, alveolar resorption occurs following tooth loss [9], hindering the placement of implant in an ideal position. It should be noted that, in this case, the width of alveolar ridge was reduced severely at the implant site, and the embedded tooth in the maxillary region hindered the placement of implant. Therefore, the initial treatment plan for this patient comprised alveolar ridge augmentation as well as extraction of the embedded tooth to create a favorable alveolar bone condition. During the second surgical procedure, GBR was planned to prepare for implant placement [10].

Bone grafting is an effective method to address insufficient bone volume. However, its use depends on the defect morphology, location of the recipient site, the available bone, and the locations of vital structures [11]. Autologous bone block grafting may be the best choice for thickening an atrophied residual alveolar ridge [12], which is usually harvested from the hip, maxillary tuberosity, mandibular symphysis, external oblique ridge of the mandible, or the ribs [2,7,13,14]. However, autografting procedures are associated with donor site morbidities [15] and require additional surgical intervention [6]. For small- to medium-sized alveolar defects, an intraoral donor site would be more easily accepted by doctors and patients, as their use is said to be less invasive and to reduce surgical and anesthetic time. In addition, procedures using intraoral donor sites can be carried out in the outpatient operating theater [5,7]. The external oblique ridge of the mandible was designated the donor site for alveolar ridge augmentation in the initial treatment plan in this case.

Analysis of the CBCT image indicated that the buccal bone wall of embedded tooth was approximately 2 cm×1 cm×2 mm in size. We thus decided to utilize the buccal bone plate of the embedded tooth as a source of autologous bone graft for alveolar ridge augmentation. This allowed us to avoid additional surgical intervention and new donor site morbidity. This decision was in conformity with the principle of surgery [16] (Figure 2), and the patient consented to the treatment plan. Even if the plan had failed, we could use the external oblique ridge of the mandible as the alternative donor site.

Previous report indicates that bone grafts require 6 months to 1 year of reconstruction before the implants can be placed [17]. Bone graft resorption may range from 20% to 50% after 6 months [18]. However, when we re-opened the mucosal flap, we found the generated newborn and solid bone tissues at the graft sites of the #11 and #12 teeth, where the width had increased by 3-4 mm (Figure 3B). Six months later, the alloplastic particulate bone had been reconstructed completely and was difficult to separate from the graft bed. After alveolar augmentation for 18 months, a continuous white line of dense bone was found in radiographic images, suggesting that the cortical bone had been regenerated during alveolar augmentation (Figure 4).

In this case, alveolar bone reconstruction might benefit from the use of an adjacent donor site, which could facilitate the recruitment of osteoblasts, vascular cells, and various growth factors required for bone remodeling [19]. Theoretically, even without the presence of embedded tooth, we could also harvest a bone block of the same size at the apical zone of anterior maxillary for alveolar ridge augmentation. Nevertheless, this approach requires validation in future animal studies and clinical randomized controlled trials.