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Clinical Science and Techniques

Bone Graft Using Block Allograft as a Treatment of Failed Implant Sites: Clinical Case Reports

Jo, Ji-Ho DDS, MDS*; Kim, Su-Gwan DDS, PhD; Oh, Ji-Su DDS, MDS

Author Information
doi: 10.1097/ID.0b013e3182885f8e
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Abstract

To maximize the functionality and esthetics of implants, primary stability should be obtained at the appropriate sites. However, in patients with loss of alveolar bone caused by tooth extractions due to severe periodontal diseases, infection, trauma, dentofacial deformities, and removal of previous implants, surgeons are sometimes not able to place implants in ideal sites.1–3 In addition, 40% to 60% of alveolar bone generally undergoes resorption within 2 to 3 years after tooth extraction; thus, bone grafts, guided bone regeneration, or both are often performed when implants are placed.4,5 In areas with severe vertical or horizontal alveolar loss, the bone volume required for implant placement can only be obtained by augmenting the width and height of the alveolar bone through distraction osteogenesis, alveolar ridge augmentation, augmentation with autogenous block bone and block graft substitutes, or diverse other methods.6–8

Autologous bone is an ideal graft material for treating alveolar bone defect areas. Because it contains diverse osteocytes and growth factors, autologous bone has the capacity for osseoinduction and osseoconduction; thus, bone regeneration can be achieved without immune reactions.9 Autogenous bones can be obtained from donor sites, such as the mandibular symphysis, the mandibular ramus, the tibia, the ileum, and the cranium. The volume and quality of the bone differ according to the donor area. Garg10 has reported on the volume and quality of bone according to the donor site. The donor sites of block bone harvesting (volume) are as follows: the block bone grafting is possible at ascending ramus (5–10 mL) and anterior mandible (5 mL) intraorally, and posterior (70 mL) and anterior iliac crest (40 mL), cranium (40 mL) provide autogenous block bone. However, autogenous block bone grafting to severe bone defects may induce side effects, such as dysesthesia of the skin, infection, loss of tooth vitality, facial changes due to mentum alterations, gait disturbances, pain, and the formation of hematomas or seromas. In addition, the volume of bone that can be transplanted is often restricted.11–14 Therefore, block allogeneic bones, xenogeneic bones, and alloplastic materials may be use as alternatives to autologous bone in transplants.

Among the diverse bone augmentation procedures for placing implants in alveolar bone with severe defects, block allobones have recently been used. Compared with block autologous bone grafts, the volume of block allogeneic bone grafts is unlimited, it does not cause complications in a donor area, and its biocompatibility is excellent compared to that of allogeneic bones and synthetic bones. Therefore, block allogeneic bone grafts have been widely used.2

This study is a case report of 2 patients with severe alveolar bone loss caused by the removal of previous implants that had failed. Because of the destruction of implant abutments in both patients, we performed the alveolar bone grafts using block allogeneic bones in the bone defect areas where the previous implants have been removed using a trephine bur; good results were obtained. The cases are reported together with a review of the literature.

Case Report

Case 1

A 50-year-old female patient was transferred to the Chosun University Dental Hospital for removal and replacement of implants in the left mandibular molar area. The patient did not have systemic disease and visited our hospital with a chief complaint of hypoesthesia that developed 2 years earlier after an implant placement. Upon clinical examination, hypoesthesia and dysesthesia in the left lower labium, the mentum, and the anterior gingival area were observed. Invasion of the implants inferior to the alveolar canal was observed in computed tomography and panorama radiographs (Fig. 1). Removal of the implants was scheduled; the bone graft was performed simultaneously to allow implants to be replaced after the resolution of the dysesthesia symptoms. The patient refused an autologous bone graft; thus, allogeneic bones were chosen.

Fig. 1
Fig. 1:
A panorama radiograph (A) and computed tomography image (B) from the first visit. A fixture of left mandibular second molar was observed in the mandibular alveolar nerve.

Conduction anesthesia was induced in the inferior alveolar nerve, a flap was lifted, and the implant was removed using a trephine bur. After removing the implant, an absorbable collagen barrier membrane (COPIOS Pericardium membrane; TUTOGEN Medical GmbH, Neunkirchen am Brand, Germany) was placed in the upper area of the exposed inferior alveolar nerve, and several perforations were formed in the vicinity of the defect area. The shape of the block allogeneic bone (Ostis, Unicorticocancellous block bone; Ostis Tissue Bank, Suwon, Republic of Korea) was adjusted to fit the shape of the bone defect area, hydrated with saline, and transplanted into the bone defect area. The bone graft was performed in the space between the block allogeneic bond and the bone defect area using allogeneic bone Allomatrix (demineralized cancellous bone allograft; Wright Medical Technology, Inc, Arlington, Tennessee) (Fig. 2). During the postsurgical recovery period, the patient did not develop infection, dehiscence, or other complications. After removing the implant, the dysesthesia was resolved, although hypoesthesia was still present in the left inferior labial area.

Fig. 2
Fig. 2:
The implant removal and block bone allograft.A, After the elevation of a trapezoidal mucoperiosteal flap with two releasing incisions. B, With the implant removed. C, The removed implant and crown. D, An absorbable collagen membrane was placed on the upper region of exposed mandibular alveolar nerve canal. E, The form of block allograft was modified to make it suitable for the bone defect. F, Many perforations were formed on the cortical bone, and after hydration of the block allograft, it was grafted onto the bone defect area. G, A tension-free primary wound closure was performed.

After a 5.5-month healing period, an implant was placed in position. The implant was a Haptite implant (Dentis Co., Ltd., Daegu, Korea) that was 4.3 mm in diameter and 8 mm in length (Fig. 3). Immediately after placement, the implant stability quotient (ISQ), as measured by the Osstell device (Integration Diagnostics, Gothenburg, Sweden), was 77. The periotest value (PTV), as measured by the Periotest device (Siemens AG, Bensheim, Germany), was −6. After 3 months, a second surgery was performed (Fig. 4); 3.5 months after the implant placement, a single-crown prosthesis treatment was performed. The implant was well maintained during the 34-month follow-up period.

Fig. 3
Fig. 3:
The re-implantation surgery.A, B, After a 5.5-month healing period, the re-implantation surgery was performed. The bone formation was so successful that the difference between the natural bone and block allograft was not clear.
Fig. 4
Fig. 4:
Panoramic view (A) and standard view (B) after re-implantation. The implant was osseointegrated and showed almost no marginal bone loss.

Case 2

A 72-year-old male patient visited the Chosun University Dental Hospital with a chief complaint of a destroyed implant abutment in the area of the left maxillary first and second molars caused by the removal and replacement of implants. The patient had a history of hypertension and diabetes. At the time of the visit, his blood pressure was 130/90 mm Hg and blood glucose was 114 mg/dL; these parameters were well controlled. In the clinical examination and radiological tests, the implants were well fused with the alveolar bone without inflammation or symptoms of infection, and 2 destroyed implants were detected in the left maxillary molar area (Fig. 5). Removal of the destroyed implants and positioning replacement implants in the appropriate 3-dimensional sites were scheduled. The bone graft was performed in the bone defect area using block allogeneic bone.

Fig. 5
Fig. 5:
An intraoral photograph and panorama from the first visit.A, Fractured implants are observed, and infectious signs are absent. B, Fractured implants on the left maxillary first and second molar are observed.

Conduction anesthesia was induced in the posterosuperior alveolar nerve and the greater palatine nerve; a flap was lifted and the implants were removed using a trephine bur. Of the bone defect areas that were formed after removing the implants, the autologous bone graft was performed in the first molar bone defect area. In the second molar bone defect area, the bone graft was performed using block allogeneic bone (Ostis, Unicorticocancellous block bone; Ostis Tissue Bank, Suwon, Republic of Korea) (Fig. 6). Infection, wound dehiscence and other complications did not develop during the postsurgical recovery period. Good bone formation was observed 4 months after the block allogeneic bone graft (Fig. 7).

Fig. 6
Fig. 6:
The implant removal and block allograft.A, Implants in the first and second maxillary molar regions were placed in inaccurate 3-dimensional positions. B, The implants were removed. C, The removed implants. D, The form of the block allograft was modified to be suitable for the bone defect. E, An autograft was obtained from the region where implants were removed and grafted into the first molar region, and a block allograft was performed on the second molar area. F, A tension-free primary wound closure was performed.
Fig. 7
Fig. 7:
Sufficient new bone was formed to allow implant placement.

After a 4.5-month healing period, the implants were placed (Fig. 8). A Haptite implant (Dentis Co., Ltd., Daegu, Republic of Korea) that was 4.3 mm in diameter and 11 mm in length was placed. The ISQ of the first molar measured immediately after the placement was 62 and that of the second molar was 75. The PTV of the first molar was 1 and that of the second molar was −3. After 6 months, a second surgery was performed. At the time of the second surgery, the ISQ value of the first molar was 79 and that of the second molar was 81. The PTV was measured at −5 in both cases (Fig. 9). One month after the second surgery, the final prosthesis restoration was performed, and clinical stability was observed (Fig. 10).

Fig. 8
Fig. 8:
After a 4.5-month healing period, secondary surgery was performed.A, The soft tissue was well healed. B, After the elevation of a trapezoidal mucoperiosteal flap with two releasing incisions. C, After replantation of the implants in the correct 3-dimensional position. D, A tension-free primary wound closure was performed. E, A panorama radiograph after the primary implant surgery.
Fig. 9
Fig. 9:
A panorama and standard radiograph after the secondary surgery.A, Stable osseointegration and marginal bone are observed in the panorama radiograph. B, A standard radiograph.
Fig. 10
Fig. 10:
Panorama and intraoral photographs after the prosthodontics.A, In a panorama radiograph, stable osseointegration, and marginal bone are observed. B and C, Intraoral photographs.

Discussion

Using implants as prostheses in the edentulous area is a common clinical approach, and the volume and quality of alveolar bone are important for the success of the implant. Due to the resorption of alveolar bone, placing implants in ideal functional and esthetic areas occasionally becomes difficult. To overcome this difficulty, clinicians place implants using diverse methods, such as bone grafts after augmentation of the alveolar bone. Autogenous bones have an excellent capacity to form new bone and have been used as ideal graft materials for quite some time.9 Nevertheless, additional surgery on the donor site (whether within the oral cavity or not) is required. Because of the consequent discomfort of patients, the possibility of side effects, and the necessity of general anesthesia, autogenous bones are not considered to be the best graft materials.15,16 Recently, diverse allogeneic bones, xenogeneic bones, and synthetic bones have been used.

Our study examined the clinical efficacy of block allogeneic bones (the use of which is on the rise). In both the cases in our study, failed implants were removed using a trephine bur, block allogeneic bones were grafted in the bone defect areas generated, and the implants were replaced. In both the cases, the block allogeneic bones that were transplanted into the maxilla and mandible showed good bone fusion. In both the cases, the implants were placed 4 to 5 months after the bone graft. Tolman17 compared the survival rate of block bones in cases where the patients received the block bone transplant and implant placement simultaneously (92%) to the rate in cases where the placement was delayed (84%) and reported that the survival rate of the block bone in the simultaneous placement cases was higher. Most of these cases used on-lay grafts; the implants were beneficial to the stability of the block bones, and the stability of the transplanted block bones was important. Our cases involved removing a 5-walled bone defect area using a trephine bur. Screws were not required for the implant placement or fixation of the block bones, and the transplanted block bones remained stable. In our 5-walled bone defect cases, the endothelial cells and osteoblasts in the bone marrow cavity could emerge from 5 directions; thus, new bone formation was more likely to occur.

Ostis block allogeneic bones, which are manufactured in Korea, were used in our study. Allogeneic bones are human tissue from donors. The gender, age, and disease history of the donors can be assessed, and antigens were almost always absent. The volume of bone that can be used in the donor area is unlimited. Disease contamination has not been reported in dental applications.18,19 The cortical bone area of block allogeneic bones is 0.5 to 1.0 mm, and the cancellous bone area is 5 to 5.5 mm. This unicortical cancellous structure is advantageous for maintaining stability using screws and allows for close attachment to the recipient site. In a short-term retrospective study of 73 patients who underwent alveolar bone augmentation using block allogeneic bones and implant placement, Keith et al20 found that 12 months after the bone transplant, the survival rate of the block allogeneic bones was 93% and that resorption of the transplanted bones was either absent (69%) or slight (0–2 mm, 31%). These results support the clinical efficacy of block allogeneic bone.

Recently, implant placement has become more frequent; implant failures due to invasion of the neural canal or destruction of the implant due to placement in inappropriate sites have also become frequent. Removing failed implants using a trephine bur and treating the bone defect areas that are generated represent additional challenges for clinicians. In our cases, the bone defects caused by removing the implants were 5-walled. Because the shape of the bone defect is advantageous to the formation of bone and because of the discomfort caused by harvesting autologous bone, the alternative of block allogeneic bone was considered.

Conclusions

This report is meaningful as suggesting alternative in treatment of failed implants. The block allograft was effective as a treatment of failed implants. Further study is needed to various treatments using the block allogeneic bones.

Disclosure

The authors claim to have no financial interest, directly or indirectly, in any entity that is commercially related to the products mentioned in this article.

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Keywords:

allograft; block bone; implant removal

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