Demineralization for inactivation of infectious retrovirus in systemically infected cortical bone: in vitro and in vivo experimental studies

Demineralized bone matrix for repair and regeneration of maxillofacial defects: A narrative review

OBJECTIVES

Demineralized bone matrix (DBM) is a well-established bone graft material widely accepted by dentists and the public for its favorable osteoconductivity and osteoinductive potential. This article aimed to provide a narrative review of the current therapeutic applications and limitations of DBM in maxillofacial bone defects.

STUDY SELECTION, DATA, AND SOURCES

Randomized controlled trials, prospective or retrospective clinical studies, case series and reports, and systematic reviews. MEDLINE, PubMed, and Google Scholar were searched using keywords.

CONCLUSIONS

Some evidence supported the therapeutic application of DBM in periodontal intrabony defects, maxillary sinus lifts, ridge preservation, ridge augmentation, alveolar cleft repair, orthognathic surgery, and other regional maxillofacial bone defects. However, the limitations of DBM should be considered when using it, including potential low immunogenicity, instability of osteoinductive potential, handling of the graft material, and patient acceptance.

CLINICAL SIGNIFICANCE

With the increasing demand for the treatment of maxillofacial bone defects, DBM is likely to play a greater role as a promising bone graft material. Safe and effective combination treatment strategies and how to maintain a stable osteoinductive potential will be the future challenges of DBM research.

Allogeneic Demineralized Dentin Matrix Graft for Guided Bone Regeneration in Dental Implants

Autogenous and allogeneic demineralized dentin matrices (Auto-DDM and Allo-DDM, respectively) are currently used for guided bone regeneration (GBR). Buccal marginal bone (BMB) resorption is critical for successful implant integration. This study analyzed BMB resorption around dental implants for GBR between the control group (Auto-DDM graft) and experimental group (Allo-DDM graft). From 2014 to 2019, we enrolled 96 patients (59 males, 37 females, average 57.13 years) who received GBR (52 and 44 using Allo-DDM and Auto-DDM, respectively,) without a barrier membrane and a simultaneous single dental implantation (54 in the maxilla and 42 in the mandible). BMB height was measured immediately after GBR, at prosthetic loading, and 12 months after loading. BMB resorption was classified as initial resorption (between GBR and prosthetic loading) and functional resorption (during 12 months after prosthetic loading). The differences in the BMB levels of Auto-DDM and Allo-DDM were analyzed between the initial and functional resorption stages by independent sample t-test. Auto-DDM and Allo-DDM showed similar BMB changes in initial resorption (0.73 ± 0.97 and 0.72 ± 0.77 mm, respectively) and functional resorption (0.69 ± 0.81 and 0.48 ± 0.58 mm, respectively) without a significant difference between the maxilla and mandible. For GBR, Allo-DDM is comparable to Auto-DDM in terms of BMB resorption.

Effects of gamma irradiation on the measurement of hepatitis B virus DNA in dentin harvested from chronically infected patients

Background

The manufacturing of the demineralized dentin matrix (DDM) has been proven to extensively reduce the presence of human hepatitis B viral DNA (HBV DNA). This study measured and compared HBV DNA in fresh dentin to that in gamma radiation (GR)-sterilized dentin extracted from HBV-infected patients. The application of GR as a means of terminal sterilization is hypothesized to inactivate or eliminate HBV within the dentin matrix.

Methods

Dentin from 18 HBV-infected patients was collected and divided into three fragments. The first fragment was unaltered and used as the control group; the remaining two fragments were sterilized with gamma radiation doses of 15 or 25 kGy. DNA was extracted and purified from each fresh (control), and the GR-sterilized (experimental) dentin specimen and HBV DNA copy numbers were evaluated on the basis of the real-time polymerase chain reaction. The copy numbers were used to assess GR efficacy as a means of terminal sterilization for HBV inactivation or elimination.

Results

HBV DNA was detected in 66.67% of the fresh dentin specimens. The differences in HBV DNA levels between the fresh dentin and the GR-sterilized dentin were confirmed by the Wilcoxon signed-rank test for the doses of 15 and 25 kGy with P value of 0.012 and 0.010, respectively. Among the twelve HBV-DNA-positive fresh dentin samples, HBV DNA persisted in eleven after GR sterilization, yet the copy number was reduced to <10 (except for a single sample within each experimental group).

Conclusions

The results suggest that 15 and 25 kGy of GR significantly reduced the HBV DNA levels in the fresh dentin matrix. Expansion of the possible clinical applications of allogenic grafts with the irradiated DDM will require additional studies, including validation of viral load inactivation to prevent infectious transmission and examination of GR exposure effects on the osteoinductivity of the matrix.

Measurement of hepatitis B virus DNA in fresh versus processed dentin from chronically infected patients

BACKGROUND

Demineralized dentin matrix (DDM) is commonly used as a bone-graft substitute. This study measured and compared human hepatitis B viruses (HBV) DNA in fresh dentin to that of dentin processed into DDM extracted during dental treatment from HBV-infected patients. The hypothesis was that the processing procedure for DDM would inactivate or eliminate HBV in the dentin matrix obtained from infected patients.

METHODS

Dentin from eighteen HBV-infected patients was collected and each dentin specimen was divided into two fragments. One fragment was used before processing as fresh dentin (control group) and the other was processed into DDM (experimental group). DNA was extracted and purified from each fresh and processed dentin specimen and the HBV DNA copy number quantitated by real time polymerase chain reaction. The HBV DNA copy number in the fresh dentin specimens were compared relative to serologic test results. The second parameter was to evaluate the effectiveness of the processing procedure (defatting, demineralization, freeze-drying, and sterilization) to inactivate or eliminate HBV by comparing the DNA copy number in the processed DDM with that in the matched fresh dentin specimens. All results were analyzed using Mann-Whitney U test to compare numerical measurements between groups and differences were considered statistically significant at P-values less than 0.05.

RESULTS

The presence of HBV DNA was detected in 55.56% (10/18) of the fresh dentin specimens. For the ten HBV DNA-positive fresh dentin specimens, HBV DNA was detected in two (20%) of the matched processed dentin specimens. The copy number of HBV DNA in the two positive processed dentin specimens was 1.79 and 4.03, which were statistically lower than that of the fresh dentin specimens (P = 0.0167).

CONCLUSIONS

The results from this study suggested that fresh dentin may be a carrier of HBV and that the procedure used to generate DDM extensively reduced the levels of HBV DNA. Further studies are needed to evaluate the infectivity of HBV in processed dentin.

A review of the clinical implications of anti-infective biomaterials and infection-resistant surfaces

Infection is currently regarded as the most severe and devastating complication associated to the use of biomaterials. The important social, clinical and economic impacts of implant-related infections are promoting the efforts to obviate these severe diseases. In this context, the development of anti-infective biomaterials and of infection-resistant surfaces is being regarded as the main strategy to prevent the establishment of implant colonisation and biofilm formation by bacteria. In this review, the attention is focused on the biomaterial-associated infections, from which the need for anti-infective biomaterials originates. Biomaterial-associated infections differ markedly for epidemiology, aetiology and severity, depending mainly on the anatomic site, on the time of biomaterial application, and on the depth of the tissues harbouring the prosthesis. Here, the diversity and complexity of the different scenarios where medical devices are currently utilised are explored, providing an overview of the emblematic applicative fields and of the requirements for anti-infective biomaterials.

Infectious feline herpesvirus detected in distant bone and tendon following mucosal inoculation of specific pathogen-free cats

Emerging evidence suggests that cats infected with feline herpesvirus-1 (FHV-1) may experience a brief viremic phase. The objective of this study was to determine whether natural routes of FHV-1 inoculation could result in viremic transmission of infectious virus to connective tissues (cortical bone, tendon). Three specific pathogen-free cats were experimentally inoculated with FHV-1 via a combined mucosal (oronasal, ocular) route. Cats were euthanized at the peak of clinical signs to aseptically harvest tissues (cortical bone, tendon, trachea/tongue) for co-culture with a susceptible cell line to promote spread of infectious virus. Viral infection of Crandall-Rees feline kidney cells was microscopically visualized by cytopathic effect (CPE). Additionally, co-culture DNA was extracted either at the point of CPE or 16 days of culture without evidence of CPE, to amplify FHV-1 glycoprotein B gene using real-time PCR. Infectious virus was detected in distant cortical bone (two cats, moderate to severe clinical signs) and tendon (one cat, severe clinical signs). Direct infection of mucosal (trachea, tongue) tissues also was confirmed in these two cats. In contrast, all co-cultured tissues from the third cat (mild clinical signs) were negative for FHV-1 by CPE and PCR. Results of this study demonstrated that early primary FHV-1 viremia may be distributed to distant connective tissues.

Characterization of the inflammatory response to four commercial bone graft substitutes using a murine biocompatibility model

Bone grafting is utilized in nearly all orthopedic subspecialties and in most anatomic regions. Bone graft substitutes have the potential to offer similar efficacy as autogenous grafts without the morbidity of harvest. Several studies have noted the efficacy of new-generation bone substitute products, but few studies have evaluated their safety. This study characterizes and quantifies the inflammatory reaction to four different commercially available bone graft substitutes, which were examined using the in vivo murine air pouch biocompatibility model. One coralline hydroxyapatite product was chosen as an example of a purely osteoconductive material. Three demineralized bone matrix products were chosen to represent products that are both osteoconductive and osteoinductive. Samples were implanted in a murine air pouch and harvested after 14 days in situ. Pouch fluid was extracted, mRNA isolated, and reverse transcription polymerase chain reactions carried out to detect interleukin-1 gene expression as a marker for inflammation. In addition, multiple histological characteristics were examined to quantify cellular responses to the implanted materials. All bone graft substitutes induced a significant inflammatory response compared with negative controls. Histology and polymerase chain reaction data indicated that the level of inflammatory reaction was elevated in materials with a higher demineralized bone matrix to carrier proportion. The hydroxyapatite product generated a low inflammatory reaction. In conclusion, this study used an in vivo model of biocompatibility to demonstrate that a significant inflammatory reaction occurs when using implanted bone graft substitutes. When choosing a bone grafting method, surgeons should consider both the efficacy and safety of methods and materials used. Further studies are necessary to determine the ideal bone graft material to maximize efficacy while minimizing morbidity.

Safety and efficacy of use of demineralised bone matrix in orthopaedic and trauma surgery

Demineralised bone matrix (DBM) acts as an osteoconductive, and possibly as an osteoinductive, material. It is widely used in orthopaedic, neurosurgical, plastic and dental areas. More than 500,000 bone grafting procedures with DBM are performed annually in the US. It does not offer structural support, but it is well suited for filling bone defects and cavities. The osteoinductive nature of DBM is presumably attributed to the presence of matrix-associated bone morphogenetic proteins (BMPs) and growth factors, which are made available to the host environment by the demineralisation process. Clinical results have not been uniformly favourable; however, a variable clinical response is attributed partly to nonuniform processing methods found among numerous bone banks and commercial suppliers. DBMs remain reasonably safe and effective products. The ultimate safe bone-graft substitute, one that is osteoconductive, osteoinductive, osteogenic and mechanically strong, remains elusive.

Allograft and alloplastic bone substitutes: a review of science and technology for the craniomaxillofacial surgeon

Bone healing is a complex and multifactorial process. As such, there are numerous steps in the process to which intervention can be directed. This has given rise to many bone graft technologies that have been used to regenerate bone, creating, perhaps, a bewildering array of options. The options that surgeons have the most familiarity with are the ones that have been available the longest (i.e., autograft and allograft). Although useful for the widest spectrum of clinical applications, limitations of these grafts has prompted the development of new materials. Demineralized bone matrix formulations and synthetic ceramic materials are now being used with greater frequency. These biomaterials have demonstrated their usefulness in facial plastic and reconstructive surgery with their ability to augment and replace portions of the craniofacial skeleton. The purpose of this article is to describe and discuss the allograft and alloplastic bone grafting technologies so that the reader can consider each in the context of the others and gain a better appreciation for how each fits into the universe of existing and emerging treatments for bone regeneration.

The influence of processes for the purification of human bone allografts on the matrix surface and cytocompatibility

Different industrial processes exist to purify allogenic bone, providing safe and cleaned blocks for bone allografting. However, they often make use of chemical reagents that can be aggressive for the bone matrix. Bone samples were processed with several soaking techniques used in industry: NaHCO3, H2O2, NaOH and H2O2+NaOH combined; the consequences on the bone matrix and cytocompoatibility were evaluated on femoral heads from osteoarthritic patients. Alterations of matrix were searched by histochemistry, atomic force microscopy (AFM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Cytocompatibility was evaluated by coculturing human osteoblast-like cells (SaOS-2) on bone slices. Collagen fibers were dramatically altered at the surface of bone treated with H2O2, NaOH (and their association), but not with NaHCO3. A marked reduction in the number of hydroxyapatite crystals was observed on the trabecular surfaces by TEM and morphological changes were evidenced in SEM and AFM. Argyrophilic proteins of the bone matrix were removed by H2O2 and NaOH (and their association), but not by NaHCO3. As a consequence, attachment, spreading, proliferation and alkaline phosphatase activity of SaOS-2 were reduced by H2O2 and NaOH treatments. Strong oxidizing reagents altered matrix integrity by modifying collagenous and non-collagenous proteins. Whether these changes have clinical consequences on the bone bonding and osseointegration in human necessitate further investigations.

Antiretroviral efficacy of a 98% solution of glycerol or ethylene oxide for inactivation of feline leukemia virus in bone

OBJECTIVE

To determine whether infectious retrovirus was inactivated in bones from FeLV-infected cats after ethylene oxide (ETO) sterilization or preservation in a 98% solution of glycerol in an in vitro cell culture system.

SAMPLE POPULATION

Metatarsal bones obtained from 5 FeLV-infected cats and cultured with feline fibroblast cells.

PROCEDURE

Metatarsal bones were treated with 100% ETO, a 98% solution of glycerol, or left untreated. Twenty-five flasks of feline fibroblast cells were assigned to 5 groups: negative control, positive control, ETO-treated bone, glycerol-treated bone, and untreated bone with 5 replicates/group for 4 passages. Media and cell samples were harvested from every flask at each passage to measure FeLV p27 antigen and the number of copies of provirus per 100 ng of DNA, respectively.

RESULTS

All negative control and ETO-treated group replicates were negative for FeLV p27 antigen and provirus throughout the study. All positive control group replicates were positive for FeLV p27 antigen and provirus at passages 1 to 4. Untreated bone group replicates were positive for FeLV p27 antigen at passages 3 and 4 and provirus beginning at passage 2. Glycerol-treated group replicates had delayed cell replication and were negative for FeLV p27 antigen and provirus at passages 1 to 4 and 2 to 4, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

Ethylene oxide sterilization of bone from FeLV-infected cats appeared to abrogate transmission of infectious retrovirus and effectively sterilized bone allografts. Impact for Human Medicine-Additional studies to confirm effectiveness of ETO treatment of allograft tissues for prevention of pathogen transmission via transplantation are warranted.

Lyophilization does not inactivate infectious retrovirus in systemically infected bone and tendon allografts

BACKGROUND

A review of multiple transplantations of human immunodeficiency virus-infected musculoskeletal allografts found that recipients of lyophilized (freeze-dried) bone or tendon from an infected donor all tested negative for human immunodeficiency virus. The finding that 75% of the recipients of fresh-frozen bone from the same donor contracted human immunodeficiency virus has led to speculation that freeze-drying may render retroviral-infected musculoskeletal allografts noninfectious.

HYPOTHESIS

Lyophilization does not inactivate retrovirus in systemically infected bone and tendon.

STUDY DESIGN

Controlled laboratory study.

METHODS

Tendons and cortical bone segments from cats systemically infected with feline leukemia virus were used in this study. Feline embryonic fibroblast cells were cultured in the presence of fresh-frozen or freeze-dried cortical bone or tendon segments. At each passage, feline leukemia virus p27 antigen was measured in media by enzyme-linked immunosorbent assay, and feline leukemia virus (pro)viral nucleic acids were quantified by real-time quantitative polymerase chain reaction in the DNA extracted from cells.

RESULTS

Enzyme-linked immunosorbent assay results and quantitative polymerase chain reaction results demonstrated retroviral antigen and proviral DNA in all cultured cell replicates after exposure to fresh-frozen or freeze-dried bones or tendons.

CONCLUSION

Freeze-drying (lyophilization) of retroviral-infected cortical bone and tendon does not inactivate retrovirus.

CLINICAL RELEVANCE

These results conclusively demonstrate that freeze-drying should not be relied on to inactivate infectious retrovirus in systemically infected musculoskeletal allografts.