Comparison of osteoconductive properties of three different β-tricalcium phosphate graft materials: a pilot histomorphometric study in a pig model

Assessment of the Osseointegration of Pure-Phase β-Tricalcium Phosphate (β-TCP) Ceramic Cylinder Implants in Critical Segmental Radial Bone Defects in Rabbits

Autografts, allografts, and synthetic bone substitutes are essential in reconstructive orthopedic surgery. Although autografts and allografts provide excellent skeletal integration, their use is limited by host morbidity and graft acquisition challenges. Synthetic materials like β-tricalcium phosphate (β-TCP) offer promising osseoconductive properties as a potential substitute. This study evaluated the osseointegration of β-TCP ceramic cylinder implants in bone defects in rabbits. Eighteen New Zealand rabbits underwent radial diaphysis ostectomy to create a critical segmental defect and were divided into three groups: Group A received β-TCP blocks, Group B received allogenous cortical bone grafts, and Group C underwent ostectomy without defect filling. Postoperative assessments included clinical evaluations, radiographs, micro-computed tomography, and histology at various time points to assess osseointegration and implant resorption. At the 120th postoperative day, Group B showed successful bone integration without infection. In contrast, Group A showed no osseointegration or resorption of the β-TCP implants, and Group C exhibited bone non-union. While β-TCP demonstrated biocompatibility, it lacked osseoconductivity, likely due to low porosity. β-TCP implants did not promote bone consolidation, suggesting that further research on porosity and shape is needed to improve their suitability for veterinary orthopedic reconstructive surgery.

Evaluation of Osseointegration and Bone Healing Using Pure-Phase β - TCP Ceramic Implant in Bone Critical Defects. A Systematic Review

Background

The gold standard for osseointegration remains the autogenous bone graft, but biomaterials such as Beta - tricalcium phosphate (β - TCP) in its pure-phase showed promising results to be practical bone substitutes. This kind of implants are optimal candidates for bone integration due to their osseoconductive, biocompatibility, bioactivity, and absorptive properties.

Methods

A systematic review was conducted using 5 databases (Cochrane Library, PubMed, Scielo, Medline-Bireme and Google Scholar) for searching published studies between January 1st 2011 and June 15th 2021. Only clinical and experimental studies, and case reports were included in this research. Human and animal studies published only in Portuguese or English with clinical, radiologic, and histologic evidence of new bone formation, osseoconduction, and osseointegration were included. This systematic review was reported according to PRISMA guidelines.

Results

Approximately 14.554 articles were initially found, but after advanced searching using specific including and excluding keywords, matching Boolean operators “AND,” “OR” and “NOT,” and after excluding duplicates, a total of 12 articles were included for this systematic review, including experimental works, a retrospective study, a randomized controlled clinical study, a randomized prospective study, a prospective observational study, and a case report. All articles showed 100% effectiveness in bone integration after β - TCP implantation by clinical, image and/or histologic assessment. Implant shape and porosity seem to have influence in osseointegration process. β - TCP can give predictable, sustainable, and adequate new bone formation with the least infection rates in implant placement cases and patient morbidity, which is the current goals for bone integration, augmentation and replacement.

Conclusion

β - TCP in its pure-phase is widely used in dentistry and maxillofacial surgery, but there is a lack of information about the use of this biomaterial for filling critical segmental defects of long bones in veterinary medicine. In this area, only experimental studies in small defects were carried out, with no clinical cases performed in animals with a longer observation time. β - TCP can produce predictable, sustainable, and adequate bone formation, with minimal infection rates and low patient morbidity. But more clinical studies in the future, demonstrating specific metric measurements in relation to bone consolidation, as well as showing results using other shapes of this implant are needed to evaluate further in depth osseoconductive and osseointegrative characteristics of this biomaterial, in order to develop new comparisons and quantitative analyses for its use in veterinary medicine as a bone replacement.

Magnesium Modified β-Tricalcium Phosphate Induces Cell Osteogenic Differentiation In Vitro and Bone Regeneration In Vivo

In vitro, in vivo, and clinical studies have shown how the physicochemical and biological properties of β-tricalcium phosphate (β-TCP) work in bone regeneration. This study aimed to improve the properties of β-TCP by achieving optimum surface and bulk β-TCP chemical/physical properties through the hydrothermal addition of magnesium (Mg) and to later establish the biocompatibility of β-TCP/Mg for bone grafting and tissue engineering treatments. Multiple in vitro and in vivo analyses were used to complete β-TCP/Mg physicochemical and biological characterization. The addition of MgO brought about a modest rise in the number of β-TCP surface particles, indicating improvements in alkaline phosphatase (ALP) activity on day 21 (p < 0.05) and in the WST-1assay on all days (p < 0.05), with a corresponding increase in the upregulation of ALP and bone sialoprotein. SEM analyses stated that the surfaces of the β-TCP particles were not altered after the addition of Mg. Micro-CT and histomorphometric analysis from rabbit calvaria critical defects resulted in β-TCP/Mg managing to reform more new bone than the control defects and β-TCP control at 2, 6, and 8 weeks (* p ≤ 0.05, ** p ≤ 0.01, *** p ≤ 0.001, and **** p ≤ 0.0001). The hydrothermal addition of MgO to the β-TCP surfaces ameliorated its biocompatibility without altering its surface roughness resulting from the elemental composition while enhancing cell viability and proliferation, inducing more bone regeneration by osteoconduction in vivo and osteoblastic differentiation in vitro.

Guided bone regeneration with osteoconductive grafts and PDGF: A tissue engineering option for segmental bone defect reconstruction

Regeneration and reconstruction of segmental bone defects (SBD) is a clinical challenge in maxillofacial surgery and orthopedics. The present study evaluated efficacy of guided bone-regeneration (GBR) of rat femoral SBD using osteoconductive equine-bone (EB) and beta-tricalcium phosphate (beta-TCP) grafts, either with or without platelet-derived growth-factor (PDGF). Following ethical-approval, 50 male Wistar-Albino rats (aged ~12-15 months and weighing ~450-500 g) were included. A 5 mm femoral critical-size SBD was created and animals were divided into five groups depending on the graft material used for GBR (EB, EB + PDGF, Autograft, beta-TCP, beta-TCP + PDGF; n = 10/group). Following 12-weeks of healing, animals were sacrificed and femur specimens were analyzed through qualitative histology and quantitative histomorphometry. There was new bone bridging femoral SBD in all groups and qualitatively, better bone formation was seen in autograft and EB + PDGF groups. Histomorphometric bone-area (BA %) was significantly high in autograft group, followed by EB + PDGF, beta-TCP + PDGF, EB, and beta-TCP groups. Addition of PDGF to EB and beta-TCP during GBR resulted in significantly higher BA%. After 12-weeks of healing, EB + PDGF for GBR of rat femoral segmental defects resulted in new bone formation similar to that of autograft. Based on this study, GBR with EB and adjunct PDGF could be a potential clinical alternative for reconstruction and regeneration of segmental bone defects.

Histological Evaluation of the Effects of Growth Factors in a Fibrin Network on Bone Regeneration

OBJECTIVE

The aim of this study was to evaluate the effect of mineralized plasmatic matrix (MPM), comprising a combination of synthetic graft and platelet concentrates, on bone regeneration.

METHODS

Critical size defects of 6-mm diameter were created on the tibias of 6 male sheep, with the animals subsequently assigned into 2 groups. Of the 5 bone defects generated per animal, 4 were randomly filled with MPM, beta-tricalcium phosphate graft (β-TCP), platelet-rich fibrin (PRF) + β-TCP, and autogenous graft. One defect was left empty as a control group. Animals were killed at 3 weeks (early healing group) and 6 weeks (late healing group). The specimens underwent histologic and histomorphometric analysis to evaluate new bone formation.

RESULTS

In both healing periods, new bone formation from autogenous bone was observed significantly more often than from biomaterials or the empty defect. The degree of new bone formation for MPM was significantly higher than that of the control group at all healing periods. In addition, it was significantly higher in both healing periods than that of β-TCP albeit only in the late healing period than that of the PRF + β-TCP combination. In all biomaterial groups, residual graft ratios decreased from early to late healing periods.

CONCLUSION

The results indicated that MPM, representing growth factors in a fibrin network, increases new bone formation in surgically created defects in sheep tibia as confirmed by histologic assessment.

Guided bone regeneration using beta-tricalcium phosphate with and without fibronectin-An experimental study in rats

OBJECTIVE

This histomorphometric study compared bone regeneration potential of beta-tricalcium phosphate with fibronectin (β-TCP-Fn) in critical-sized calvarial defects (CSDs) in rats to assess whether fibronectin (Fn) improved new bone formation.

MATERIAL AND METHODS

Critical-sized calvarial defects were created in 30 adult male Sprague Dawley rats, which were divided into four groups according to the time of euthanasia (6 or 8 weeks of healing) and type of filling (β-TCP-Fn/6 weeks, β-TCP/6 weeks, β-TCP-Fn/8 weeks and β-TCP/8 weeks). The primary variables related to new bone formation were augmented area (AA) and gained tissue (GT; sum of mineralized bone matrix [MBM] and bone substitute [BS]). Secondary variables were the diameter of the defect, MBM, non-mineralized tissue (NMT) and BS.

RESULTS

A total of 29 rats and 58 histological samples were evaluated, 28 (48.3%) samples obtained at 6 weeks and 30 (51.7%) at 8 weeks, homogeneously distributed between right and left sides. Thirteen (22.4%) were treated with β-TCP-Fn, 16 (27.6%) with β-TCP and 29 (50%) were controls. At 8 weeks, histomorphometric analysis showed significant differences in AA using β-TCP and β-TCP-Fn versus controls (p = 0.001 and p = 0.005, respectively). Bone turnover expressed as % within the target area was slightly higher but not statistically significant in the β-TCP-Fn than in β-TCP (MBM) at 6 weeks versus 8 weeks (p = 0.067 and p = 0.335, respectively). Finally, the total GT area in mm² was higher using β-TCP-Fn as compared to β-TCP (p = 0.044).

CONCLUSIONS

β-TCP-Fn was slightly but non-significantly more effective than β-TCP without Fn for improving the volume of regenerated bone in CSDs of rats, possibly allowing a more efficient bone remodelling process. This effect however should continue being investigated.

Nano-Biphasic Calcium Phosphate Ceramic for the Repair of Bone Defects

Calcium phosphate bioceramics has recently experienced increased interest in bone reconstruction. Mimicking of natural structure of bone, like the use of nanomaterials, is an attractive approach for generating scaffolds for bone regeneration. The aim of present study was to evaluate the effect of nanonization on the biphasic calcium phosphate (BCP) ceramic in the repair of bone cavities in the canine mandible. A commercial BCP was dry-milled in a high energy planetary ball mill with zirconia balls and container. Three holes (8 mm in diameter) were outlined to the depth of cortical bone of mandibular angle of 5 dogs bilaterally. The first hole (positive control group A, n = 10) was filled in with commercial BCP material. The second hole was loaded with the nanonized BCP (experimental group C, n = 10) and the third one was left untreated (negative control group B, n = 10). The defects were allowed to regenerate for 8 weeks. New bone formation was greater in groups A and C than in B. No difference was seen between group A and group C (P = 0.676). The residual bone material in group C (19.34 ± 8.03) was as much as one-half of that in group A (38.69 ± 7.90%) (P = 0.000). The negative control group B presented the highest amount of soft tissue within the bone defects. The least percentage of marrow space was found in the positive control group (13.23 ± 13.52). Our results depicted that the rate of resorption increased significantly after nanonization even though the nano-sized BCP failed to make a superior regeneration than the ordinary BCP.

To what extent does hyaluronic acid affect healing of xenografts? A histomorphometric study in a rabbit model

Among the many graft materials that have been used for the treatment of bone defects in oral and maxillofacial regions is xenograft. To improve osteoconductive effects of xenografts, they have been combined with various biocompatible materials, such as hyaluronic acid and bone morphogenetic protein. To determine bone-healing capacity of high molecular weight hyaluronic acid (HA) combined with xenograft in rabbit calvarial bone defects. Ten adult male New Zealand rabbits (mean weight 3 kg) were included in the study. Three 6-mm-diameter bicortical cranial defects were created on calvarial bone of all rabbits. These defects were filled as follows: a) xenograft; b) HA+xenograft; c) autograft. One month after the first operation, rabbits were sacrificed. Specimens were evaluated histomorphometrically. Considering multiple comparisons, differences regarding new bone were statistically significant between all groups (p<0.05). The volume of residual graft was significantly decreased in HA group compared to xenograft group (p=0.035). Marrow space, trabecular thickness (TbTh), trabecular width (TbWi), trabecular separation (TbSp), and number of node: number of terminus (NNd:NTm) in the autograft group were significantly better than xenograft and HA groups (p<0.05). However, regarding marrow space, TbTh, TbWi, TbSp, and NNd:NTm values, xenograft and HA groups showed similar results and the difference were not significant (p>0.05). These results support that high molecular weight hyaluronic acid could contribute to the healing of xenograft by improving the percentage of new bone formation and reducing the percentage of residual graft. However, HA did not significantly affect the quality of newly formed bone assessed by microarchitectural parameters.

Application of selected scaffolds for bone tissue engineering: a systematic review

PURPOSE

The current systematic review investigated the results of application of some of the most commonly used scaffolds in conjugation with stem cells and growth factors in animal and clinical studies.

METHODS

A comprehensive electronic search was conducted according to the PRISMA guidelines in NCBI PMC and PubMed from January 1970 to December 2015 limited to English language publications with available full texts. In vivo studies in relation to "bone healing," "bone regeneration," and at least one of the following items were investigated: allograft, β-tricalcium phosphate, deproteinized bovine bone mineral, hydroxyapetite/tricalcium phosphate, nanohydroxyapatite, and composite scaffolds.

RESULTS

A total of 1252 articles were reviewed, and 46 articles completely fulfilled the inclusion criteria of this study. The highest bone regeneration has been achieved when combination of all three elements, given scaffolds, mesenchymal stem cells, and growth factors, were used. Among studies being reported in this review, bone marrow mesenchymal stem cells are the most studied mesenchymal stem cells, β-tricalcium phosphate is the most frequently used scaffold, and platelet-rich plasma is the most commonly used growth factor.

CONCLUSION

The current review aimed to inform reconstructive surgeons of how combinations of various mesenchymal stem cells, scaffolds, and growth factors enhance bone regeneration. The highest bone regeneration has been achieved when combination of all three elements, given scaffolds, mesenchymal stem cells, and growth factors, were used.

Effects of Hypericum perforatum on the healing of xenografts: a histomorphometric study in rabbits

The aim of this study was to investigate effects of the Hypericum perforatum (St John's Wort) on bone healing in rabbit calvarium. Ten male New Zealand rabbits each had three bicortical defects made in the calvarial bones, which were filled with xenograft, xenograft+H perforatum oil extract, and autogenous graft. Four weeks postoperatively all rabbits were killed and the bony defects examined histomorphometrically. Tissue compartments including new bone (p<0.001), marrow space (p<0.001), and residual bone grafts (p=0.014) differed significantly among groups. The volume of residual graft was significantly decreased in the xenograft/H perforatum group compared with those with xenografts alone (p=0.0147). The differences in microarchitectural variables of de novo bone formation were also significant (trabecular thickness (p<0.001), trabecular width (p<0.001), trabecular separation (p=0.001). There were no significant differences in node:terminus ratio between the xenograft/H perforatum group and the other two groups. However, the difference in node:terminus ratio between the autogenous graft and xenograft group was significant (p=0.001) Oil extracts of H perforatum improved bony healing in defects filled with bovine-derived xenografts.

Extra-oral defect augmentation using autologous, bovine and equine bone blocks: A preclinical histomorphometrical comparative study

OBJECTIVES

This study aimed to compare autologous bone (AB), bovine bone (BB), and equine bone (EB) blocks with regard to de novo bone formation, connective tissue, and residual bone substitute material portions in a standardized defect animal model.

MATERIAL AND METHODS

In the frontal skull of 20 pigs, 106 standardized cylindrical "critical size defects" were prepared. Defects were randomly filled with AB, BB, and EB blocks. After a healing period of 30 and 60 days, de novo bone formation, residual bone substitute material, and connective tissue portion was assessed by means of histomorphometry (Toluidine blue O staining). Mann-Whitney U-tests were used to evaluate differences between the groups.

RESULTS

The de novo bone formation was significantly higher in the AB group in comparison to the xenogeneic groups (p < 0.05). After 30 days, EB showed significantly (p < 0.05) more newly formed bone compared to the BB group. The soft tissue formation was significantly higher in the BB and EB group. Defects augmented with BB showed significantly (p < 0.05) higher portions of bone substitute materials compared to sides augmented with EB after 30 days.

CONCLUSION

In the extra-oral model, AB blocks were superior concerning de novo bone formation. No clinical advantages of EB blocks could be observed.