1. The use of frozen, radiation-sterilised allografts in complications of alveolar ridge reconstruction performed with other bone-replacement materials INTRODUCTION The key for stable, aesthetic, and durable implant – based prosthetic restoration in patients with atrophied alveolar ridge is its prior reconstruction. A dentist may use a variety of synthetic, human or animal-origin materials, which allow successful restoration of the optimal ridge dimensions. Augmentation carries some failure risk; therefore following a failed procedure a number of patients show even more severe atrophy of the hard tissue than before treatment instead of a wide alveolar ridge. This situation is caused by chronic inflammation leading to increased resorption of the bone tissue within the alveolar ridge. Allogeneic materials are often chosen by doctors as the size and shape of a graft are not limited (Wallace 2013, Eastlund 2006). However, they are believed to be highly resorbable during restructuring and change their mechanical parameters. This opinion is undermined by numerous studies indicating considerable influence of graft preparation in tissue banks on resorption and stability of the graft (Schwartz-Arad 2005, Krasny 2013, Cornu 2000). MATERIAL & METHODS The material comprised 8 patients who underwent surgical procedure of alveolar ridge augmentation for the second time due to unsuccessful first attempt to widen the ridge with other bone-replacement materials. After cleaning the surgical site of the residue, unresorbed granulate as well as inflamed tissue a macroscopically normal bone was revealed. If the width of the ridge was slightly reduced and the bone showed pitting, which resulted from chronic inflammation, allogeneic granulate was used. If the defect was much greater than optimal width of the alveolar ridge required for implantation (6 mm), the reconstruction was performed with frozen, radiation-sterilised, cortico-spongious bone blocks. The grafted material was obtained from a Polish tissue bank. Demineralised bone matrix and allogeneic bone blocks were prepared in class C clean rooms in the Department of Transplantology and Central Tissue Bank. Both types of bone grafts were processed from bone tissue retrieved from deceased donors after donor screening (medical and social history, medical examination and autopsy results) and negative results of serologic testing obtained. Frozen cortico-spongious bone blocks were prepared from the iliac ala. After being defatted in alcohol solution and rinsed bone blocks were subsequently radiation-sterilised with a dose of 35 kGy. Whereas, the frozen demineralised bone matrix was prepared from the compact bone of diaphysis. Bone grafts after grounding and defatting were decalcified in 0,6M HCl and rinsed. The dose of 25 kGy was used for radiation-sterilisation. For both graft types the radiation sterilisation was performed with the accelerated electron beam in the Institute of Nuclear Chemistry and Technology in Warsaw (Dziedzic- Goclawska 2005, Kamiński 2010). Artur Kamiński 1, Kornel Krasny 2, Marta Krasny 3, Małgorzata Zadurska 3 1. Department of Transplantology and Central Tissue Bank, Warsaw Medical University artur.kaminski@wum.edu.pl 2. Medicare Dental Practice, Warsaw kornel.krasny@op.pl 3. Department of Orthodontics, Warsaw Medical University, mkrasny@op.pl, malgorzatazadurska@wp.pl OBJECTIVE Evaluation of efficacy of demineralised bone matrix (Fig. 1) as well as frozen, radiation sterilised bone blocks (Fig. 2) for reconstruction of an atrophied alveolar ridge following unsuccessful attempt of augmentation with other bone- replacement material. Overall, three procedures were performed with the use of blocks and five with the use of granulate. In all the presented cases the second augmentation was successful in spite of more difficult clinical situation resulting from more advanced atrophy of the alveolar ridge. In each patient widening of the alveolar ridge was obtained, which allowed embedment of the implant, that united with the bone after 6 months in case of the maxilla and 3 months in case of the mandible. Following the osteointegration period all the dental defects were restored with intraosseous implant-supported, porcelain crowns. During a one-year follow-up after the treatment was completed none of the implants or grafts were lost. CONCLUSION Frozen, radiation-sterilised allogeneic bone material both, in the form of a block as well as granulate, seems to be an adequate alternative for other materials used in order to widen the bone of the alveolar ridge, particularly in difficult, complicated cases, where the first regeneration procedure was not successful. REFERENCES Wallace SC, Snyder MB, Prasad H (2013) Postextraction ridge preservation and augmentation with mineralized allograft with or without recombinant human platelet-derived growth factor BB (rhPDGF-BB): a consecutive case series. Int J Periodontics Restorative Dent. Sep-Oct;33(5):599-609. Eastlund T (2006) Bacterial infection transmitted by human tissue allograft transplantation. Cell Tissue Bank 7:147– 166. Schwartz-Arad D, Levin L, Sigal L (2005) Surgical Success of Intraoral Autogenous Block Onlay Bone Grafting for Alveolar Ridge Augmentation. Impl Dent 14(2):131-138. Krasny M, Krasny K, Kamiński A, Zadurska M, Piekarczyk P, Fiedor P (2013) Evaluation of safety and efficacy of radiation-sterilized bone allografts in reconstructive oral surgery. Cell Tissue Bank. Sep;14(3):367-74. Cornu O, Banse X, Docquier PL, Luyckx S, Delloye C (2000) Effect of freeze-drying and gamma irradiation on the mechanical properties of human cancellous bone. J Orthop Res 18:426-431. Fig. 1 Demineralised bone matrix Fig. 2 Cortico-spongious bone block Fig.3 Xenogeneic material, not integrated with the bone within the area of distal root of tooth 46. Fig.4 Bone replacement material filling the alveolus. Fig.5 Condition after 3 years of grafting. Fig. 3 Fig. 4Fig. 5 Fig. 6 Fig. 7 Fig. 8Fig. 9 Fig. 6 Mucosa inflammation Fig.7 Funnel-shaped defect of the outer bone lamella in the alveolar ridge. Fig.8 Fixed bone block; view from the vestibule and from the occlusion plane. Fig.9 Implant embedded in the bone block, integrated with the process bone.