Traditionally, bone graft materials such as autografts, allografts, xenografts, and synthetic grafts have been widely used. Autografts are considered the 'gold standard' for bone grafting but have limitations such as the need for additional surgery to harvest donor tissue and the limited quantity available¹⁾. On the other hand, allografts and xenografts can overcome some drawbacks of autografts but carry risks of disease transmission and immune response²⁾. To address these limitations, various bone graft materials have been developed, including tooth-derived grafts.

Dentin and bone have similar compositions, and some non-collagenous proteins in dentin function similarly to bone morphogenetic proteins. Autogenous demineralized dentin matrix (DDM) contains intrinsic growth factors such as bone morphogenetic proteins (BMP), transforming growth factor-β (TGF-β), platelet-derived growth factor (PDGF), fibroblast growth factor (FGF), and insulin-like growth factor (IGF), making it a recognized osteoinductive bone graft material^3-5). The first use of autogenous tooth-derived bone graft material was reported in South Korea in 2008⁶⁾. Subsequent clinical cases have shown that tooth-derived grafts exhibit excellent bone remodeling and formation capabilities, comparable to those of autografts^7,8). However, because tooth-derived grafts are made from extracted teeth, the quantity that can be produced is limited, and immediate preparation may not always be feasible. Consequently, third molars may be extracted in advance, and the tooth-derived graft material may be stored for future use.

Long-term storage of bone graft materials can lead to protein denaturation and a decrease in osteoinductive potential. Additionally, further sterilization may be required to prevent infection, which could potentially degrade internal proteins or compromise structural stability^9,10). However, dentin has a higher collagen density than bone, making it more resistant to external stimuli such as heat or gamma radiation, suggesting that tooth-derived grafts may retain their function after long-term storage¹¹⁾. Despite this, few studies have examined the efficacy and safety of long-term stored tooth-derived grafts. his case report evaluates the clinical outcome of using a decade-old autogenous DDM for bone grafting and assesses its effectiveness and safety as a bone graft material.

In 2013, a 53-year-old female patient had teeth #47 and #48 extracted, and autogenous tooth-derived bone graft material (Auto BT, Autogenous Demineralized Dentin Matrix, Korea Tooth Bank, Seoul, Republic of Korea) was prepared. The graft material from tooth #48 was used during the implant surgery for tooth #47, while the graft material from tooth #47 was stored in a vacuum-sealed package at room temperature without exposure to direct sunlight. After 10 years, in 2023, the patient presented with bone loss around the root of tooth #17 and secondary caries. Immediate implant placement was planned after extracting tooth #17 (Fig. 1A).

Figure 1. Images at the first surgery. (A) Preoperative panoramic view; (B) Osteotomy of the surgical site; (C) Extraction socket; (D) Fixture placement; (E) Sterilized autoge-nous demineralized dentin; (F) Grafting of the extraction socket with autogenous demineralized den-tin; (G) Primary closure of surgical site; (H) Postoperative panoramic view at 3-months.

The patient presented with a missing crown. Following local anesthesia, osteotomy was performed to prevent drill slippage at the implant site (Fig. 1B). A fixture (4.2 mm width, 10 mm length; Dentis Implant, Daegu, Republic of Korea) was placed (Fig. 1D). The previously prepared autogenous DDM, re-sterilized using EO gas, was grafted to the bone defect around the fixture (Fig. 1E, F). The flap was advanced using a periosteal releasing incision, and primary closure was achieved without a barrier membrane (Fig. 1G).

Radiographic evaluation three months after the first surgery showed that the volume of the grafted material was maintained, but the corticocancellous complex was not fully formed (Fig. 1H). Thus, a second surgery was planned after an additional two-month healing period. At the second surgery, five months after the first, successful bone regeneration was observed around the implant (Fig. 2B). A healing abutment (4.5 mm diameter, 4.5 mm height) was placed and secured with 30 Ncm torque, followed by primary closure (Fig. 2E, F). Postoperative radiographs showed more defined cortical lines, indicating the formation of a dense bone matrix (Fig. 2G).

Figure 2. Images at the secondary surgery including vestibuloplasty. (A) The surgical site showing insu-fficient vestibular depth 5-months after the primary surgery; (B) Favorable bone healing observed at the grafted site; (C) Connection of the healing abutment and suturing; (D) Mucosal incision and muscle dissection for vestibul-oplasty; (E, F) Primary closure of the surgical site; (G) Postoperative panoramic view.

To compensate for the loss of vestibular depth caused by the advanced flap during the bone grafting, vestibuloplasty was performed during the second surgery (Fig. 2D). Mucosal incision and muscle dissection were performed, and the vestibular fornix was sutured to the periosteum of the alveolar ridge (Fig. 2E). The sutures were removed after ten days, and the final prosthesis was delivered six weeks later. During the one-year follow-up after prosthesis loading, the bone and gingiva around the implant remained stable without any complications (Fig. 3).

Figure 3. 1 year after prosthesis loading. Intraoral images at buccal (A), distal (B), and palatal side (C); (D) panoramic view.

The recommended storage period and conditions for bone graft materials vary by product, however, the denaturation of internal proteins and loss of function can increase the risk of infection and decrease biocompatibility, especially with prolonged storage over time^12-14). However, tooth-derived graft materials, compared to bone grafts, have a higher collagen density, which may make them more resistant to denaturation and infection during sterilization and storage¹⁵⁾. In this case report, the grafted DDM, stored for ten years and re-sterilized using EO gas, successfully maintained its function as a bone graft material, showing corticocancellous bone formation five months after the first surgery. The high collagen density of dentin likely prevented excessive denaturation during the long storage period, and the DDM withstood the re-sterilization process¹¹⁾. Therefore, preparing autogenous tooth-derived bone grafts in advance during third molar extractions should be considered.

Re-sterilization is necessary to mitigate infection risk when using long-stored bone graft materials. However, re-sterilization, particularly using high-temperature autoclave methods, may denature proteins such as BMPs, potentially impairing the graft material's osteogenic capacity. Jin et al. reported superior results when using EO gas for re-sterilization rather than high-temperature methods for autogenous tooth grafts in implant placement¹⁶⁾. Moreover, several studies have reported that EO gas sterilization minimally reduces the osteogenic and osteoconductive properties of demineralized bone graft materials^17-19). This suggests that EO gas sterilization is more favorable for maintaining the biocompatibility and safety of bone graft materials²⁰⁾. In this case as well, excellent clinical outcomes were achieved using long-term stored autogenous tooth-derived bone graft material that was re-sterilized with EO gas. Therefore, when re-sterilizing long-term stored autogenous tooth-derived bone graft materials, it is advisable to choose EO gas over high-temperature sterilization to minimize protein denaturation.

One limitation of this case report is that the implant placement and bone grafting were performed immediately after tooth extraction. Due to the regional acceleratory phenomenon and the spontaneous bone healing process that follows extraction, the precise osteogenic potential of the autogenous demineralized dentin matrix (DDM) could not be accurately assessed²¹⁾. Consequently, the ten-year-old autogenous bone-derived tooth (AutoBT) graft formed functional bone within five months, suggesting that it could maintain long-term functionality. However, since this study is based on a single case, randomized controlled trials with a larger sample size should be done subsequently in order to secure the safety and efficacy. Despite these limitations, this case is significant as the first to report the successful use of autogenous DDM stored for ten years in bone grafting. The results suggest that autogenous tooth-derived bone grafts can be effectively used even after long-term storage. Although prolonged storage is generally not ideal, tooth-derived grafts may offer extended storage capabilities not typically associated with other bone graft materials. Future research should focus on evaluating the biological activity of growth factors like BMPs in long-stored autogenous DDM and assessing the impact of EO gas re-sterilization on these factors. It is crucial to determine the clinically effective storage period for autogenous tooth-derived grafts and establish guidelines for their clinical use.

This study demonstrated that using autogenous tooth-derived bone graft material stored for ten years and re-sterilized with EO gas resulted in successful clinical and radiographic outcomes after one year of follow-up. Although subsequent research is required to strengthen the grounds, the results of this study suggest that preparing and storing autogenous tooth-derived bone graft materials in advance may be beneficial for future bone graft procedures.