Homogenous demineralized dentin matrix and platelet-rich plasma for bone tissue engineering in cranioplasty of diabetic rabbits: biochemical, radiographic, and histological analysis

Demineralized dentin matrix for bone regeneration in dentistry: A critical update

Over the last few decades, several new materials and techniques have been developed for bone regeneration. Scaffolds based on demineralized dentin matrix (DDM) present an attractive option due to their availability and several animal and human studies have been conducted to ascertain their utility in regenerative dentistry. The aim of this review was to summarize the recent studies conducted on DDM and used for bone grafts. PubMed, Web of Science, and Scopus were used to search for studies published within the last 10 years. The keywords and terms used were: "demineralized dentine matrix", "bone grafting", "bone augmentation" and "guided tissue regeneration" in various combinations. Original studies (in vitro, animal and human) and systematic reviews were included in the literature search. The literature search initially identified 23 studies (16 animal studies and 7 clinical reports. Most studies included in this review indicate that DDM has demonstrated promising results in a variety of dental and regenerative medicine applications. Further studies are required to completely comprehend its characteristics and prospective applications. Future studies should also focus on optimizing the processing protocols for the production of DDM-based scaffolds.

Recent progress in bone-repair strategies in diabetic conditions

Bone regeneration following trauma, tumor resection, infection, or congenital disease is challenging. Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia. It can result in complications affecting multiple systems including the musculoskeletal system. The increased number of diabetes-related fractures poses a great challenge to clinical specialties, particularly orthopedics and dentistry. Various pathological factors underlying DM may directly impair the process of bone regeneration, leading to delayed or even non-union of fractures. This review summarizes the mechanisms by which DM hampers bone regeneration, including immune abnormalities, inflammation, reactive oxygen species (ROS) accumulation, vascular system damage, insulin/insulin-like growth factor (IGF) deficiency, hyperglycemia, and the production of advanced glycation end products (AGEs). Based on published data, it also summarizes bone repair strategies in diabetic conditions, which include immune regulation, inhibition of inflammation, reduction of oxidative stress, promotion of angiogenesis, restoration of stem cell mobilization, and promotion of osteogenic differentiation, in addition to the challenges and future prospects of such approaches.

Dynamics of CSBD Healing after Implementation of Dentin and Xenogeneic Bone Biomaterial

Autologous dentin is frequently used in guided bone regeneration due to its osteoinductive properties, which come from its similarity to native bone. On the other hand, the xenogeneic bone biomaterial Cerabone^® serves as a biocompatible, but hardly resorbed biomaterial. During bone healing, an inflammatory, vascular, and osteogenic response occurs in which cytokines such as tumor necrosis factor-alpha (TNF-α), vascular endothelial growth factor (VEGF), and osteopontin (OPN) are released locally and systemically. The aim was to follow up the dynamics (on days 3, 7, 15, 21, and 30) of critical-sized bone defect (CSBD) healing after the implantation of bovine devitalized dentin, rat dentin, and xenogeneic bone biomaterial. For this purpose, histological and histomorphometric methods were employed. Additionally, serum concentrations of TNF-α, VEGF, and OPN were monitored in parallel to better understand the biomaterial-dependent systemic response in rats. At the last time interval, the results showed that the bone defect was bridged over in all three groups of biomaterials. The rat dentin group had the highest percentage of bone volume (BV/TV) and the least percentage of residual biomaterial (RB), which makes it the most optimal biomaterial for bone regeneration. Serum concentrations of the TNF-α, VEGF, and OPN refer to systemic response, which could be linked to intense bone remodeling between days 15 and 21 of the bone healing.

Comparing the effect of demineralized versus hybrid dentin matrices on inducing bone regeneration in New Zealand white rabbits' Mandibular defect

OBJECTIVES

The aim of this study was to compare the effect of using demineralized dentin matrix (DDM) versus hybrid dentin matrices; Demineralized and undemineralized dentin particles (DDM +UDDM) on inducing bone regeneration in mandibular defects.

DESIGN

The study was conducted on fifty adult New Zealand rabbits, twenty for preparation of experimental materials and thirty for surgical procedures. They were randomly assigned into 3 equal groups as follow one control group: no treatment and two experimental groups including demineralized group: treated with DDM only; and hybrid group: treated with a hybrid of (50% DDM+50% UDD). A rounded critical size defect (10 mm in diameter- 5 mm in depth) was created in the body of mandible. After 3- and 6-weeks post-surgery, the bone regeneration was evaluated by light microscope, scanning electron microscope and histomorphometry.

RESULTS

Histological, histomorphometrical observation and SEM revealed that both dentin matrices had largely resorbed and induced new bone formation at both experimental groups compared to the control group, with statistically higher percentage of new bone formation in the hybrid group.

CONCLUSION

We concluded that although both dentin matrices induced new bone formation; however, hybrid dentin matrix yielded better results compared to DDM group.

Demineralized Dentin Matrix for Dental and Alveolar Bone Tissues Regeneration: An Innovative Scope Review

Background:

Dentin is a permeable tubular composite and complex structure, and in weight, it is composed of 20% organic matrix, 10% water, and 70% hydroxyapatite crystalline matrix. Demineralization of dentin with gradient concentrations of ethylene diamine tetraacetic acid, 0.6 N hydrochloric acid, or 2% nitric acid removes a major part of the crystalline apatite and maintains a majority of collagen type I and non-collagenous proteins, which creates an osteoinductive scaffold containing numerous matrix elements and growth factors. Therefore, demineralized dentin should be considered as an excellent naturally-derived bioactive material to enhance dental and alveolar bone tissues regeneration.

Method:

The PubMed and Midline databases were searched in October 2021 for the relevant articles on treated dentin matrix (TDM)/demineralized dentin matrix (DDM) and their potential roles in tissue regeneration.

Results:

Several studies with different study designs evaluating the effect of TDM/DDM on dental and bone tissues regeneration were found. TDM/DDM was obtained from human or animal sources and processed in different forms (particles, liquid extract, hydrogel, and paste) and different shapes (sheets, slices, disc-shaped, root-shaped, and barrier membranes), with variable sizes measured in micrometers or millimeters, demineralized with different protocols regarding the concentration of demineralizing agents and exposure time, and then sterilized and preserved with different techniques. In the act of biomimetic acellular material, TDM/DDM was used for the regeneration of the dentin-pulp complex through direct pulp capping technique, and it was found to possess the ability to activate the odontogenic differentiation of stem cells resident in the pulp tissues and induce reparative dentin formation. TDM/DDM was also considered for alveolar ridge and maxillary sinus floor augmentations, socket preservation, furcation perforation repair, guided bone, and bioroot regenerations as well as bone and cartilage healing.

Conclusion:

To our knowledge, there are no standard procedures to adopt a specific form for a specific purpose; therefore, future studies are required to come up with a well-characterized TDM/DDM for each specific application. Likely as decellularized dermal matrix and prospectively, if the TDM/DDM is supplied in proper consistency, forms, and in different sizes with good biological properties, it can be used efficiently instead of some widely-used regenerative biomaterials.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13770-022-00438-4.

Allogeneic Dentin Graft: A Review on Its Osteoinductivity and Antigenicity

Studies on allogeneic demineralized dentin matrix (Allo-DDM) implantation in the 1960s and 1970s provided the most reliable preclinical evidence of bone formation and antigenicity in an extraosseous site. Recently, applications of Allo-DDM at skeletal sites were studied, and have provided reliable evidence of bone-forming capacity and negligible antigenicity. However, the osteoinductivity and antigenicity properties of Allo-DDM in extraskeletal sites have not yet been investigated due to the lack of follow-up studies after the initial research. The clinical applications of autogenous DDM (Auto-DDM) have been standardized in some countries. Long-term clinical studies have reported the development of several shapes of Auto-DDM, such as powders, blocks, moldable forms, and composites, with recombinant human bone morphogenetic protein-2. For the development of Allo-DDM as a reliable bone graft substitute next to Auto-DDM, we reviewed preclinical studies on the bone induction capacity of allogeneic dentin at extraskeletal as well as skeletal sites. Electronic databases were screened for this review in January 2020 and searched from 1960 to 2019. This review aims to provide a foundation on the preclinical studies of Allo-DDM, which could enable future researches on its osteogenic capability and antigenicity. In conclusion, Allo-DDM showed great potential for osteoinductivity in extraskeletal sites with low antigenicity, which neither adversely affected osteogenic capability nor provoked immunologic reactions. However, the risk of viral disease transmission should be researched before the clinical application of Allo-DDM.

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.

Combining autologous particulate dentin, L-PRF, and fibrinogen to create a matrix for predictable ridge preservation: a pilot clinical study

OBJECTIVES

The aim of this study was to describe the histological and clinical outcome of "dentin block" (a mixture of autologous particulate dentin, leukocyte- and platelet-rich fibrin (L-PRF), and liquid fibrinogen) in alveolar ridge preservation.

MATERIAL AND METHODS

Ten extraction sockets were grafted with "dentin block," a mixture of particulate autologous dentin with chopped leukocyte-platelet-rich fibrin (L-PRF) membranes at a 1:1 ratio, and liquid fibrinogen as a binder. Two grafted sites were followed at 4 and 5 months, and 6 sites at 6 months. Biopsies were taken from the core of the grafted site for histologic and histo-morphometric analysis.

RESULTS

All patients completed the study without any adverse event. The vertical and horizontal dimensions of the alveolar ridge were preserved or even increased after 4, 5, or 6 months and remained stable after 6 months of the implant placement. The histological examination revealed a median relative percentage of bone, dentin, and connective tissue of 57.0, 0.9, and 39.3%, respectively. A comparison of samples at different time points (4, 5, and 6 months) showed a progressive increase in the proportion of bone with a decrease in the proportion of dentin. The bone was compact with normal osteocytes and moderate osteoblastic activity. In 4 out of 10 samples, no dentin was observed; in the other samples, it represented 1-5% (with geometric fragments).

CONCLUSIONS

Dentin block showed to be a suitable bone substitute in an alveolar ridges preservation model.

CLINICAL RELEVANCE

The promising results of dentin block as a bone substitute in alveolar ridge preservation could have an important clinical impact considering this biomaterial brings together the regenerative potential of three autologous products with excellent biological and clinical behavior, low risk of adverse effects, and feasible acquisition.

Leukocyte- and platelet-rich fibrin as graft material improves microRNA-21 expression and decreases oxidative stress in the calvarial defects of diabetic rabbits

OBJECTIVE

Leukocyte- and platelet-rich fibrin (L-PRF) represents a natural, low-cost product which may promote tissue healing by mechanisms not fully elucidated. Diabetes mellitus (DM) disrupts bone healing by inducing inflammation and oxidative stress (OS), mechanisms regulated by microRNAs (miRs). The aim of the present study was to investigate the microRNA-21 (miR-21) involvement in diabetic bone regeneration using L-PRF alone or in combination with a standard grafting material.

DESIGN

After the induction of diabetes (alloxan 100 mg/kg), four cranial osteotomies were made in diabetic (n = 12) and non-diabetic (n = 12) rabbits: one was left empty and the remaining three were grafted with L-PRF, bovine hydroxyapatite (Bio-Oss^®) and L-PRF + Bio-Oss®. Two and eight weeks postoperatively, the samples were harvested for miR-21 expression (Real-time RT-PCR) and enzyme-linked immunosorbent assay analyses.

RESULTS

Diabetic rabbits showed decreased miR-21 and matrix metalloproteinase-9 (MMP-9) protein expression while increased malondialdehyde (MDA) levels two weeks postoperatively; however, there were no significant differences in miR-21 and MMP-9 levels between diabetic and non-diabetic rabbits in samples taken eight weeks postoperatively. Application of L-PRF and L-PRF + Bio-Oss^® improved miR-21 and MMP-9 and decreased MDA levels while Bio-Oss® alone enhanced superoxide dismutase (SOD) activity levels in diabetic rabbits.

CONCLUSION

L-PRF alone or in combination with bovine hydroxyapatite as bone graft could be beneficial in DM since it seems to improve inflammation-modulatory miR-21 expression and decreases oxidative stress.

Pulsed electromagnetic fields preserve bone architecture and mechanical properties and stimulate porous implant osseointegration by promoting bone anabolism in type 1 diabetic rabbits

The effects of exogenous pulsed electromagnetic field (PEMF) stimulation on T1DM-associated osteopathy were investigated in alloxan-treated rabbits. We found that PEMF improved bone architecture, mechanical properties, and porous titanium (pTi) osseointegration by promoting bone anabolism through a canonical Wnt/β-catenin signaling-associated mechanism, and revealed the clinical potential of PEMF stimulation for the treatment of T1DM-associated bone complications.

INTRODUCTION

Type 1 diabetes mellitus (T1DM) is associated with deteriorated bone architecture and impaired osseous healing potential; nonetheless, effective methods for resisting T1DM-associated osteopenia/osteoporosis and promoting bone defect/fracture healing are still lacking. PEMF, as a safe and noninvasive method, have proven to be effective for promoting osteogenesis, whereas the potential effects of PEMF on T1DM osteopathy remain poorly understood.

METHODS

We herein investigated the effects of PEMF stimulation on bone architecture, mechanical properties, bone turnover, and its potential molecular mechanisms in alloxan-treated diabetic rabbits. We also developed novel nontoxic Ti2448 pTi implants with closer elastic modulus with natural bone and investigated the impacts of PEMF on pTi osseointegration for T1DM bone-defect repair.

RESULTS

The deteriorations of cancellous and cortical bone architecture and tissue-level mechanical strength were attenuated by 8-week PEMF stimulation. PEMF also promoted osseointegration and stimulated more adequate bone ingrowths into the pore spaces of pTi in T1DM long-bone defects. Moreover, T1DM-associated reduction of bone formation was significantly attenuated by PEMF, whereas PEMF exerted no impacts on bone resorption. We also found PEMF-induced activation of osteoblastogenesis-related Wnt/β-catenin signaling in T1DM skeletons, but PEMF did not alter osteoclastogenesis-associated RANKL/RANK signaling gene expression.

CONCLUSION

We reveal that PEMF improved bone architecture, mechanical properties, and pTi osseointegration by promoting bone anabolism through a canonical Wnt/β-catenin signaling-associated mechanism. This study enriches our basic knowledge for understanding skeletal sensitivity in response to external electromagnetic signals, and also opens new treatment alternatives for T1DM-associated osteopenia/osteoporosis and osseous defects in an easy and highly efficient manner.

Strategies for delivering bone morphogenetic protein for bone healing

Bone morphogenetic proteins (BMPs) are the most significant growth factors that belong to the Transforming Growth Factor Beta (TGF-β) super-family. Though more than twenty members of this family have been identified so far in humans, Food and Drug Administration (FDA) approved two growth factors: BMP-2 and BMP-7 for treatments of spinal fusion and long-bone fractures with collagen carriers. Currently BMPs are clinically used in spinal fusion, oral and maxillofacial surgery and also in the repair of long bone defects. The efficiency of BMPs depends a lot on the selection of suitable carriers. At present, different types of carrier materials are used: natural and synthetic polymers, calcium phosphate and ceramic-polymer composite materials. Number of research articles has been published on the minute intricacies of the loading process and release kinetics of BMPs. Despite the significant evidence of its potential for bone healing demonstrated in animal models, future clinical investigations are needed to define dose, scaffold and route of administration. The efficacy and application of BMPs in various levels with a proper carrier and dose is yet to be established. The present article collates various aspects of success and limitation and identifies the prospects and challenges associated with the use of BMPs in orthopaedic surgery.