Allogeneic Bone Blocks Research Articles

Experimental study of the bearing capacity of lyophilized allogeneic bone material

Was to conduct an experimental study of the bearing capacity and determination of the Young's modulus of lyophilized allogeneic bone material. The study used 5 prototypes of lyophilized allogeneic bone blocks, which were alternately subjected to static loading by compressive force. The experimental values of Young's modulus of all bone samples were determined. When applying the Student's probability distribution in statistical processing of experimental data, the average indicators of the forces of destruction of the samples were obtained and Young's modulus was determined. As a result of the study, the indices of the maximum loading (6012H) and Young's modulus (147.2±0.228 MPa) of lyophilized allogeneic bone material were obtained. The obtained Young's modulus of lyophilized allogeneic bone material is of great importance in scientific activity, providing the possibility of further investigation of the properties of lyophilized allogeneic bone tissue to form a preoperative forecast of the behavior of an osteoplastic material and a dental implant installed in it.

Assessment of clinical outcomes and histomorphometric findings in alveolar ridge augmentation procedures with allogeneic bone block grafts: A systematic review and meta-analysis.

Background This systematic literature review aimed to evaluate the efficacy of allogeneic bone blocks for ridge augmentation by assessing block survival rates and subsequent implant survival, including post-surgical complications and histomorphometric analysis. Material and Methods An electronic and manual search among references, was conducted up to April 2019 by two independent authors. Inclusion criteria were: human clinical trials in which the outcomes of allogeneic bone block grafts were evaluated by means of their survival rates and subsequent implant success rates. Results Seven articles fulfilled the inclusion criteria and were analyzed. A total of 323 allogeneic block grafts were monitored for a minimum of 12 months follow-up after surgery, of which thirteen (4.02%) failed. Regarding the cumulative implant survival rate, the weighted mean was 97.36%, computed from 501 implants. Histologic and histomorphometric analysis showed that allogeneic block grafts presented some clinical and microstructural differences in comparison with autologous block grafts. Conclusions Atrophic alveolar crest reconstruction with allogeneic bone block grafts would appear a feasible alternative to autologous bone block grafts, obtaining a low block graft failure rate, similar implant survival rate and fewer postoperative complications. Further investigations generating long term data are needed to confirm these findings. Key words:Allogeneic block, clinical outcome, ridge augmentation, dental implants.

Osseous ingrowth in allogeneic bone blocks applied for vertical bone augmentation: a preclinical randomised controlled study.

The aim of the present study was the qualitative and quantitative evaluation of osseous graft consolidation using allogeneic bone blocks for vertical bone augmentation in an animal model. Standardised allogeneic and autologous bone blocks were fixed on the frontal skull of 20 adult female pigs and covered with a resorbable collagen membrane. Animals were sacrificed after 2 and 6 months. Specimens were histologically and histomorphometrically analysed focusing on the amount of vital bone, residual bone substitute material and connective tissue. Furthermore, the amount of expression of bone matrix proteins (collagen type I and osteocalcin) and de novo vessel formation (von Willebrand factor) were quantified by immunohistochemistry. Significantly more allogeneic bone blocks failed for both evaluation time points (p < 0.05). Allogeneic blocks showed significantly less vital bone with more connective tissue formation compared to autologous bone blocks. Increased vessel formation could be detected for both evaluation time points in the contact area of autologous bone with local bone. The expression of collagen type I and osteocalcin was significantly lower in the allogeneic bone graft. Allogeneic cancellous bone blocks showed a significantly higher failure rate compared to autologous bone blocks. Allogeneic bone blocks seemed to negatively affect bone formation or negatively influence the host in the long term, and increased connective tissue formation and block loss should be anticipated. In order to maintain patient safety and treatment success clinicians should be persuaded to make a conscious choice of the applied biomaterials with regard to their components and structure.

Balancing Purification and Ultrastructure of Naturally Derived Bone Blocks for Bone Regeneration: Report of the Purification Effort of Two Bone Blocks.

The present publication reports the purification effort of two natural bone blocks, that is, an allogeneic bone block (maxgraft®, botiss biomaterials GmbH, Zossen, Germany) and a xenogeneic block (SMARTBONE®, IBI S.A., Mezzovico-Vira, Switzerland) in addition to previously published results based on histology. Furthermore, specialized scanning electron microscopy (SEM) and in vitro analyses (XTT, BrdU, LDH) for testing of the cytocompatibility based on ISO 10993-5/-12 have been conducted. The microscopic analyses showed that both bone blocks possess a trabecular structure with a lamellar subarrangement. In the case of the xenogeneic bone block, only minor remnants of collagenous structures were found, while in contrast high amounts of collagen were found associated with the allogeneic bone matrix. Furthermore, only island-like remnants of the polymer coating in case of the xenogeneic bone substitute seemed to be detectable. Finally, no remaining cells or cellular remnants were found in both bone blocks. The in vitro analyses showed that both bone blocks are biocompatible. Altogether, the purification level of both bone blocks seems to be favorable for bone tissue regeneration without the risk for inflammatory responses or graft rejection. Moreover, the analysis of the maxgraft® bone block showed that the underlying purification process allows for preserving not only the calcified bone matrix but also high amounts of the intertrabecular collagen matrix.

Horizontal Alveolar Ridge Augmentation with Allogeneic Bone Block Graft Compared with Autogenous Bone Block Graft: a Systematic Review.

ABSTRACTObjectivesThe objective of the present systematic review was to test the hypothesis of no difference in implant treatment outcome after horizontal ridge augmentation with allogeneic bone block compared with autogenous bone block.Material and MethodsA MEDLINE (PubMed), Embase and Cochrane Library search in combination with a hand-search of relevant journals was conducted including human studies published in English through March 13, 2019. Comparative and non-comparative studies evaluating horizontal ridge augmentation with allogeneic bone block were included. Cochrane risk of bias tool and Newcastle-Ottawa Scale were used to evaluate risk of bias.ResultsOne comparative study with high quality and 12 non-comparative studies fulfilled the inclusion criteria. Considerable heterogeneity prevented meta-analysis from being performed. The comparative retrospective short-term study demonstrated no significant difference in implant treatment outcome between the two treatment modalities. Non-comparative long-term studies revealed high implant survival, gain in alveolar ridge width and bone regeneration with allogeneic bone block. However, non-comparative studies disclosed high incidence of complications including dehiscence, exposure of allogeneic bone block and partial or total loss of the grafts.ConclusionsThere seemed to be no difference in implant treatment outcome after horizontal ridge augmentation with allogeneic bone block compared with autogenous bone block. However, increased risk of complications was frequently reported with allogeneic bone block.

Comparison of allogeneic and autogenous bone grafts for augmentation of alveolar ridge defects-A 12-month retrospective radiographic evaluation.

ObjectivesThe aim of this study was to compare three‐dimensional alterations following the use of autogenous versus allogeneic onlay grafts for augmentation at single tooth defects.Materials and methodsAlveolar bone width at specific implant sites were assessed using sagittal and cross‐sectional CBCT images prior grafting and at three subsequent time points. Twenty‐one patients received autogenous bone blocks harvested from the retromolar region and another 21 patients received freeze‐dried cancellous allogeneic bone blocks.ResultsThe vertical and horizontal dimensions did not significantly differ between autogenous and allogeneic bone grafts at any time point. In addition, there were no statistically significant differences in graft remodeling rates between autogenous (mean shrinkage rate after 12 months: 12.5% ± 7.8%) and allogeneic onlay grafts (mean shrinkage rate after 12 months: 14.4% ± 9.8%).ConclusionsFreeze‐dried cancellous allogeneic bone blocks showed equivalent volumetric shrinkage rates as autogenous bone blocks when used for treating circumscribed bone defects classified as Type‐II to Type‐IV according to the ITI‐treatment guide categories. Therefore, it is not necessary to over‐contour the alveolar ridge when using allogeneic blocks for treating single tooth defects, but to apply the same procedure as when using autogenous blocks.

Mandibular ridge reconstruction: A review of contemporary methods.

Reconstruction can be very problematic in the case of mandibular alveolar bone loss, which can also hinder the implant restorative treatment. The aim of the study was to present current views on reconstructing the alveolar part of mandibular bone, which allows the insertion of implants and then the placement of denture. Based on the available literature, the efficacy of various techniques of filling of mandibular bone losses was described and compared. Reconstruction with autogenous bone block graft had been used as a gold standard. Recently, other techniques have appeared that offer better functional and esthetics results. They include reconstruction with allogeneic bone block graft, osteotomy allowing immediate insertion of implants, bone distraction, guided bone regeneration using titanium mesh (Ti-mesh), new techniques using scaffolds (biphasic calcium phosphate, poly-lactide-co-glycolide/tricalcium phosphate, bioresorbable polycaprolactone), Sonic Weld Technique® (Tuttlingen, Germany) using resorbable membrane and pins with polymer lactide acid (PLA), and the tent technique. These abovementioned techniques allow solving the problem of insufficient amount of bone for prosthetic treatment.

Treatment of a bilaterally severely resorbed posterior mandible due to early tooth loss by Guided Bone Regeneration using customized allogeneic bone blocks: A case report with 24 months follow‐up data

The use of allogeneic bone grafts for alveolar ridge reconstruction has become an often-discussed alternative to augmentation procedures using autografts. Nevertheless, there still is a lack of literature concerning long-time experiences of allografts for alveolar ridge reconstruction. Especially the results of the use of allogeneic bone blocks for mandible reconstructions need to be further investigated. In this case report, we present the use of customized allogenic bone blocks in Guided Bone Regeneration (GBR) procedures for severely deficient mandibulary bones, the implantation after a healing period of 5 month and the 24-month follow-up data. Customized allogeneic bone blocks seem to be a successful alternative to augmentations with autologous bone blocks reconstructing highly resorbed mandibulary alveolar ridges, showing highest volume stability and no signs of bone resorption after implant loading. The application of customized allogeneic bone blocks has shown to be a successful augmentation technique even compared with with autologous bone blocks reconstructing highly resorbed mandibulary alveolar ridges demonstrating no compromises regarding clinical outcome, functionality and esthetics.

Allogeneic Bone Block Volume Preservation in Ridge Augmentation for Implants.

Allogeneic bone blocks are commonly used for bone augmentation in implant dentistry. Allogeneic bone blocks have the advantage of containing growth factors and the original human scaffold. A major disadvantage is the risk of substantial graft volume decrease due to resorption. The purpose of this study was to evaluate whether corticocancellous allogeneic bone blocks can predictably maintain graft volume to allow implant placement and esthetic restoration. A total of 141 allogeneic bone blocks were placed in 117 patients, allowing for 183 implants. The implant success rate was 96.7% after 6 to 96 months of follow-up.

Detection of major histocompatibility complex molecules in processed allogeneic bone blocks for use in alveolar ridge reconstruction

Because processed allogenic bone blocks contain remnants of cells and other organic material, the present study examined the putative presence of major histocompatibility complex (MHC) molecules in protein extracts derived from processed allogeneic bone blocks. Protein content and the immunogenic potential of 3 different processed allografts (Osteograft, DIZG, Berlin, Germany; Caput femoris, DIZG, Berlin, Germany; Human Spongiosa, Charité Tissue Bank, Berlin, Germany) were assessed by protein extraction and analysis of the presence of MHC class 1 and 2 molecules prior to grafting. MHC concentration was measured by using enzyme-linked immunosorbent assay. Protein content in the allograft materials varied between 0.87 and 1.61 µg protein/mg. In the allograft Human Spongiosa, no MHC was detected, whereas in the allogeneic bone blocks Osteograft and Caput femoris MHC 1 (0.04-0.037 ng/mg graft material) and in Osteograft MHC class 2 molecules were detectable. The results of the present study suggest that despite thorough processing, a potential antigenicity of allografts is not eliminated. MHC molecules in allografts may sensitize the immune system.

Evaluation of the Safety and Clinical Efficacy of Allogeneic Bone Grafts in the Reconstruction of the Maxilla and Mandible

IntroductionLoss of teeth caused by inflammatory processes or trauma is one of the causes of bone atrophy of the maxilla alveolar process and the alveolar part of the mandible. Often, restoring these deficiencies with dental implants requires additional reconstructive procedures. Methods using autogenous, allogeneic, xenogeneic, or synthetic bone grafts are commonly used. Materials and MethodsPatients who had bone atrophy of the maxilla or mandible were qualified for deep-frozen transplantation, radiation-sterilized allogeneic bone from the Bank of Tissues in the form of cortico-spongy bone blocks and spongy bone granules. Bone blocks were stabilized with titanium screws, and the free spaces were additionally supplemented with chips from autogenous bone and covered with allogeneic pericardial transplants and platelet-rich fibrin (PRF). Four months after the bone reconstruction, titanium implants were placed, and then after the osseointegration period prosthetic restoration was performed. Clinical safety and efficacy were determined by analyzing the quantity and quality of the reconstructed bone tissue and the degree of resorption was assessed. ResultsThe surgical procedures performed confirmed the safety and efficacy of biological material in the reconstruction of the jaw. In two cases, the treatment was not effective and the transplant was removed. In the remaining cases, titanium implants were successfully placed and loaded with prosthetic works. DiscussionImplanting deeply frozen, radiation-sterilized bone is a safe and effective surgical procedure. As an appropriate technique for fixing the allogeneic bone block, additional use of autogenous bone chips and PRF allows one to obtain a good, long-lasting clinical result.

Allogeneic bone block for challenging augmentation-a clinical, histological, and histomorphometrical investigation of tissue reaction and new bone formation.

The aim of the present study was the histological investigation of an allogeneic spongious bone block for horizontal and vertical ridge augmentation in humans. The amount of new bone, soft tissue, and residual bone substitute were histomorphometrically assessed after a mean healing period of 6months. Fourteen patients received augmentation with an allogeneic spongious bone block (Tutobone®, Tutogen Medical, Neunkirchen, Germany). After 6months of healing, 28 implants were placed with simultaneous harvesting of bone biopsies for histological and histomorphometrical analysis. Moreover, samples from the bone blocks were collected as blanks and analyzed histologically. The formation of new bone, connective tissue, and remaining bone substitute material as well as vascularization and formation of multinucleated giant cells (MNCGs) within the augmentation bed were analyzed. New bone formation could be observed primarily in close proximity to the bone block. Histomorphometrical analyses showed 18.65 ± 12.20% newly formed bone, 25.93 ± 12.36% allogeneic spongious bone block, and 53.45 ± 10.34% connective tissue. MNCGs were observed on the biomaterial surface. Furthermore, organic residues were evident, as donor-related cellular remnants within the osteocyte lacunae were found in the blank bone blocks and in the analyzed biopsies. Despite the presence of donor-related organic remnants, the bone block shows the ability to serve as a scaffold for new bone formation. Within the limits of the present study, the detect organic remnants seemed not to affect the bone formation or influence the host in the long term. Clinicians have to make a conscious choice of the applied biomaterials with regard to their components and structure to support tissue regeneration and maintain patient safety.

Proof-of-concept study of vertical augmentation using block-type allogenic bone grafts: A preclinical experimental study on rabbit calvaria.

This study aimed to quantify the healing following vertical augmentation of allogenic bone blocks with/without recombinant human bone morphogenetic protein-2 (rhBMP-2) on rabbit calvaria. Experiments were performed using allogenic bone blocks which were grafted bilaterally with or without rhBMP-2 on 20 rabbit calvaria, and these animals were divided to four groups according to the use of rhBMP-2 and healing periods (2 and 8 weeks; n = 10 in each group). Onlay-type bone blocks (8 mm in diameter and 5 mm high) were fixed with a self-tapping screw after removing the cortex in the control group, and the same protocol was applied with the addition of soaking the bone blocks with rhBMP-2 for 15 min in the test group. Radiographic and histologic analyses were performed after 2 or 8 weeks to evaluate the volumetric stability and bone regeneration within the grafted area. The radiographic analysis revealed that the height of the allogenic bone block decreased but its volume was maintained from 2 to 8 weeks in both the control and test groups. The histologic results demonstrated a statistically significant increase in new bone area in the test group, especially in the lower region adjacent to the preexisting calvarial floor. The amount of newly formed bone in all regions of the augmented bone blocks in both the control and test groups was greater at 8 weeks than at 2 weeks. In conclusion, the vertically grafted allogenic bone block maintained its volume with new bone formation, and this was accelerated by the addition of rhBMP-2. These findings indicate that allogenic bone block soaked with rhBMP-2 could be a useful candidate biomaterial for vertical augmentation. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2700-2707, 2018.

Bone Augmentation Using Allogeneic Bone Blocks With Recombinant Bone Morphogenetic Protein-2.

Because of limitations of the absorbable collagen sponge (ACS), recombinant bone morphogenetic protein (rhBMP-2) requires a scaffolding device for ridge augmentation. Twenty-one patients were treated with 37 allogeneic block grafts and rhBMP-2/ACS. Cone-beam computed tomography (CBCT) was used to measure the ridge at 2 points preoperatively, postoperatively, and after graft healing. Dental implants were placed after 6 months of healing. The CBCT scan measurements revealed variable graft resorption at 2.0 mm and 5.0 mm above the crest (point A: 0%-33.82%; point B: 0%-31.51%). The graft resorption at point A averaged 14.7 ± 11.59% and at point B averaged 6.67 ± 8.25%. There was no statistically significant difference between these 2 points. All 37 bone blocks were found well incorporated. The range of horizontal augmentation gain at the crest (point A) was 2.8 mm to 7.7 mm (average horizontal gain 4.61 ± 0.82 mm). Sixty dental implants were inserted into the blocks in all planned sites. One implant failed during prosthetic treatment for an implant survival of 98.3%. Follow-up at 3 to 34 months found no additional failures. This case series suggests that allogeneic bone blocks may be a suitable replacement for titanium mesh as a resorbable scaffold with rhBMP-2/ACS. The growth factor may also improve allogeneic block graft incorporation.

Variant Purification of an Allogeneic Bone Block.

ObjectiveThis short communication reports on a histological analysis of the composition of the commercially available Maxgraft® allogeneic bone block.Materials and MethodsBased on previously published, easily applicable histological methods, blanc samples of the Maxgraft® allogeneic bone block have been decalcified, dehydrated and embedded in paraffin before histological and histochemical staining. Afterwards, the slides were evaluated for their material characteristics, such as the bone matrix structure and other components, including collagen or cells/cell remnants.ResultsThe results show that this bone block exhibits a trabecular structure with lamellar sub-organization. Additionally, cellular remnants within the osteocyte lacunae and at the outer trabecular surfaces reside together with remnants of the former inter-trabecular fatty and connective tissue, i.e., collagenous structures and connective tissue cells or cell remnants.ConclusionConsistent with a previous study on this topic, the data presented here demonstrate that some of the certified purification techniques might not allow for the production of allogeneic materials free of organic cell and tissue components.

Complications with allogeneic, cancellous bone blocks in vertical alveolar ridge augmentation: prospective clinical case study and review of the literature

Vertical bone augmentation in dental implantology is an indication for cancellous allogeneic bone blocks (ABB). However, these materials may lead to adverse reactions, which are known well in orthopedics but rarely published. Therefore, in this study, we performed an evaluation of the use of ABB in vertical bone augmentation in clinical dental implantology. The prospective clinical study included 20 cases with vertical augmentation using ABB and subsequent or simultaneous placement of implants in the lateral maxilla and mandible. Follow-up included panoramic radiography, tissue healing, and peri-implantitis. Because of the limited number of patients, the report was planned to be descriptive only. Loss of ABB or peri-implantitis of more than 30% of the intraosseous implant length was deemed to indicate failure. The study was cancelled after six cases because of an unexpectedly high number of complications (5 of 6; 83%). The average surveillance time was 1460 days. Three types of unsatisfying outcome were observed: type I, early complete loss of the augmentation with soft tissue defects after 3 to 8 weeks (n= 2); type II, early soft tissue maceration (up to 8 weeks) without loss of coverage and complete early bone healing with later peri-implantitis and bone loss after prosthetic loading (6 months or later; n= 2); and type III, complication-free bone healing with subsequent peri-implantitis after prosthetic loading (6 months or later; n= 1). Complications were observed in vertical augmentation with ABB and implant placement. After careful consideration, literature data were found to support these results and also suggest that tissue level implants may be advantageous in vertical bone augmentation with ABB.

Success rate of implants placed in autogenous bone blocks versus allogenic bone blocks: A systematic literature review.

The aim of this study is to review and compare survival/success rate of dental implants inserted in autogenous and allogenic bone blocks (ALBs). A PubMed search was performed from January 1990 to June 2014 limited to English language and human studies. Studies that reported treatment outcome of implants inserted in augmented alveolar ridges with autogenous or ALBs were included. Primary search identified 470 studies. For autogenous bone block (ABB) 36 articles and for ALB 23 articles met the inclusion criteria. Evidence on implant survival/success rate of both techniques was limited to observational studies with relatively small sample sizes. Study design, treatment methods, follow-ups, defect location, and morphology varied among studies. The range of implant survival and success rates in ABB was from 73.8% to 100% and 72.8% to 100%, respectively. The corresponding numbers for ALB were 95.3–100% and 93.7–100%, respectively. A definite conclusion could not be reached. Future studies with long-term follow-ups are required to further elucidate this issue.

Dentoalveolar reconstruction: modern approaches.

A variety of bone grafting materials is available to facilitate the augmentation of defective alveolar ridges. This review evaluates current literature regarding bone grafting materials with emphasis on autologous and allogeneic bone block augmentation. Autogenous bone is a reliable grafting material providing predictable long-term results with high implant survival/success rates and low morbidity rates. The resorption properties of the iliac crest are well known and are compared with calvarial grafts more prominent. Recent studies demonstrated surgical techniques to prevent graft resorption after iliac crest grafting. Allogeneic block graft and implant survival rates appear promising in short-term clinical studies. At this stage, iliac crest remains the gold standard in large alveolar bone defects. Autogenous material is not a panacea; however, none of the available materials can currently surpass it. Rather, each material has its specific advantage for certain indications. Evident long-term studies of allogeneic bone grafting are lacking. Detected cells in allogeneic bone substitute material are positive for major histocompatibility complex classes I and II. Despite the promising clinical results achieved with allogeneic bone grafts, the current literature lacks sufficient data on antigenicity.

Repair of segmental load-bearing bone defect by autologous mesenchymal stem cells and plasma-derived fibrin impregnated ceramic block results in early recovery of limb function.

Calcium phosphate-based bone substitutes have not been used to repair load-bearing bone defects due to their weak mechanical property. In this study, we reevaluated the functional outcomes of combining ceramic block with osteogenic-induced mesenchymal stem cells and platelet-rich plasma (TEB) to repair critical-sized segmental tibial defect. Comparisons were made with fresh marrow-impregnated ceramic block (MIC) and partially demineralized allogeneic bone block (ALLO). Six New Zealand White female rabbits were used in each study group and three rabbits with no implants were used as negative controls. By Day 90, 4/6 rabbits in TEB group and 2/6 in ALLO and MIC groups resumed normal gait pattern. Union was achieved significantly faster in TEB group with a radiological score of 4.50 ± 0.78 versus ALLO (1.06 ± 0.32), MIC (1.28 ± 0.24), and negative controls (0). Histologically, TEB group scored the highest percentage of new bone (82% ± 5.1%) compared to ALLO (5% ± 2.5%) and MIC (26% ± 5.2%). Biomechanically, TEB-treated tibiae achieved the highest compressive strength (43.50 ± 12.72 MPa) compared to those treated with ALLO (15.15 ± 3.57 MPa) and MIC (23.28 ± 6.14 MPa). In conclusion, TEB can repair critical-sized segmental load-bearing bone defects and restore limb function.

On the feasibility of utilizing allogeneic bone blocks for atrophic maxillary augmentation.

Purpose. This systematic review was aimed at assessing the feasibility by means of survival rate, histologic analysis, and causes of failure of allogeneic block grafts for augmenting the atrophic maxilla. Material and Methods. A literature search was conducted by one reviewer in several databases. Articles were included in this systematic review if they were human clinical trials in which outcomes of allogeneic bone block grafts were studied by means of survival rate. In addition other factors were extracted in order to assess their influence upon graft failure. Results. Fifteen articles fulfilled the inclusion criteria and subsequently were analyzed in this systematic review. A total of 361 block grafts could be followed 4 to 9 months after the surgery, of which 9 (2.4%) failed within 1 month to 2 months after the surgery. Additionally, a weighed mean 4.79 mm (95% CI: 4.51–5.08) horizontal bone gain was computed from 119 grafted sites in 5 studies. Regarding implant cumulative survival rate, the weighed mean was 96.9% (95% CI: 92.8–98.7%), computed from 228 implants over a mean follow-up period of 23.9 months. Histologic analysis showed that allogeneic block grafts behave differently in the early stages of healing when compared to autogenous block grafts. Conclusion. Atrophied maxillary reconstruction with allogeneic bone block grafts represents a reliable option as shown by low block graft failure rate, minimal resorption, and high implant survival rate.