Osteoregenerative efficacy of a novel synthetic, resorbable Ca/P/S-based bone graft substitute in intra- and peri-articular fractures: a brief medical image-based report.

BACKGROUND: When a fracture goes into or around a joint, it usually damages the cartilage at the ends of bones and other joint tissue. As a result, the affected joints are prone to traumatic arthritis, leading to stiffness. Repairing bone damage, maintaining joint integrity, and avoiding subchondral and metaphyseal defects caused by comminuted fractures is often a great challenge for orthopedic surgeons. Tissue engineering of synthetic bone substitutes has proven beneficial to the attachment and proliferation of bone cells, promoting the formation of mature tissues with sufficient mechanical strength and has become a promising alternative to autograft methods. The purpose of this study is to retrospectively evaluate the clinical outcome and efficacy of a novel synthetic, highly biocompatible, and fully resorbable Ca/P/S-based bone substitute based on medical image findings. MATERIALS AND METHODS: A synthetic, inorganic and highly porous Ca/P/S-based bone-substituting material (Ezechbone® Granule, CBS-400) has been developed by National Cheng-Kung University. We collected fourteen cases of complex intra- and peri-articular fractures with Ezechbone® Granule bone grafting between 2019/11 and 2021/11. We studied the evidence of bone healing by reviewing, interpreting and analyzing the medical image recordings. RESULTS: In the present study, CBS-400 was observed to quickly integrate into surrounding bone within three weeks after grafting during the initial callus formation of the early stage of repair. All of these cases healed entirely within three months. In addition, the patient may return to daily life function after 3.5 months of follow-up and rehabilitation treatment. CONCLUSIONS: Ezechbone® Granule CBS-400 was proved capable of promoting bone healing and early rehabilitation to prevent soft tissue adhesions and joint contractures. Moreover, it has a high potential for avoiding ectopic bone formation or abnormal synostosis. TRIAL REGISTRATION: The Institutional Review Board at National Cheng Kung University Hospital (NCKUH) approved the study protocol (A-ER-109-031, 3-13-2020).

Physical/Chemical Properties and Resorption Behavior of a Newly Developed Ca/P/S-Based Bone Substitute Material.

Properly regulating the resorption rate of a resorbable bone implant has long been a great challenge. This study investigates a series of physical/chemical properties, biocompatibility and the behavior of implant resorption and new bone formation of a newly developed Ca/P/S-based bone substitute material (Ezechbone® Granule CBS-400). Experimental results show that CBS-400 is comprised majorly of HA and CSD, with a Ca/P/S atomic ratio of 54.6/39.2/6.2. After immersion in Hank's solution for 7 days, the overall morphology, shape and integrity of CBS-400 granules remain similar to that of non-immersed samples without showing apparent collapse or disintegration. With immersion time, the pH value continues to increase to 6.55 after 7 days, and 7.08 after 14 days. Cytotoxicity, intracutaneous reactivity and skin sensitization tests demonstrate the good biocompatibility features of CBS-400. Rabbit implantation/histological observations indicate that the implanted granules are intimately bonded to the surrounding new bone at all times. The implant is not merely a degradable bone substitute, but its resorption and the formation of new cancellous bone proceed at the substantially same pace. After implantation for 12 weeks, about 85% of the implant has been resorbed. The newly-formed cancellous bone ratio quickly increases to >40% at 4 weeks, followed by a bone remodeling process toward normal cancellous bone, wherein the new cancellous bone ratio gradually tapers down to about 30% after 12 weeks.

Osteoporotic Goat Spine Implantation Study Using a Synthetic, Resorbable Ca/P/S-Based Bone Substitute.

One primary purpose of the present study is to clarify whether the highly porous, resorbable Ca/P/S-based bone substitute used in this study would still induce an osteoporotic bone when implanted into the osteoporotic vertebral defects of ovariectomized (OVX) goats, or the newly-grown bone would expectantly be rather healthy bone. The bone substitute material used for the study is a synthetic, 100% inorganic, highly porous and fast-resorbable Ca/P/S-based material (Ezechbone® Granule CBS-400). The results show that the OVX procedure along with a low calcium diet and breeding away from light can successfully induce osteoporosis in the present female experimental goats. The histological examination reveals a newly-formed trabecular bone network within the surgically-created defect of the CBS-400-implanted (OVX_IP) goat. This new trabecular bone network in the OVX_IP goat appears much denser than the OVX goat and comparable to the healthy control goat. Histomorphometry show that, among all the experimental goats, the OVX_IP goat has the highest trabecular thickness and lowest trabecular bone packet prevalence. The differences in trabecular plate separation, trabecular number and trabecular bone tissue area ratio between the OVX_IP goat and the control goat are not significant, indicating that the trabecular bone architecture of the OVX_IP goat has substantially recovered to the normal level in about 6 months after implantation without signs of osteoporosis-related delay in the bone maturing process. The quick and nicely recovered trabecular architecture parameters observed in the OVX_IP goat indicate that the present Ca/P/S-based bone substitute material has a high potential to treat osteoporotic fractures.

Microstructural investigation of stress-assisted α″-α' phase transformation in cold-rolled Ti-7.5Mo alloy.

The present study investigated the microstructure and stress-assisted α″-α' phase transformation of a solution-treated Ti-7.5Mo alloy being cold-rolled with a series of different thickness reductions using transmission electron microscopic (TEM) and electron backscatter diffraction (EBSD) techniques. The EBSD/IPF results indicated a substantially random texture in ST sample. When the alloy was mildly cold-rolled, a texture toward 〈101¯0〉 preferred orientation was established, which gradually shifted toward 〈21¯1¯0〉 with increased reduction in thickness. The TEM results indicated that substantially all fine platelets in the solution-treated (ST) sample had an orthorhombic α″ phase, and that a stress-assisted α″-to-α' phase transformation took place when the alloy was cold-rolled, confirming the XRD results. In the mildly rolled (CR20) sample, the existence of α' phase could be easily identified, indicating that the stresses involved in the mild rolling process were sufficient to initiate the α″-α' phase transition. On the other hand, in the heavily rolled (CR80) sample, the presence of residual α″ phase was still observed throughout the sample, indicating that the α″-to-α' phase transition was never complete even after a severe cold rolling process. The SAD analysis indicated an orientation relationship, α(')(12¯10)//α(″)(202¯) and α' [0001]//α″ [020], existing between the two phases.

Structure, properties and animal study of a calcium phosphate/calcium sulfate composite cement.

In-vitro and in-vivo studies have been conducted on an in-house-developed tetracalcium phosphate (TTCP)/dicalcium phosphate anhydrous (DCPA)/calcium sulfate hemihydrate (CSH)-derived composite cement. Unlike most commercial calcium-based cement pastes, the investigated cement paste can be directly injected into water and harden without dispersion. The viability value of cells incubated with a conditioned medium of cement extraction is >90% that of Al2O3 control and >80% that of blank medium. Histological examination reveals excellent bonding between host bone and cement without interposition of fibrous tissues. At 12 weeks-post implantation, significant remodeling activities are found and a new bone network is developed within the femoral defect. The 26-week samples show that the newly formed bone becomes more mature, while the interface between residual cement and the new bone appears less identifiable. Image analysis indicates that the resorption rate of the present cement is much higher than that of TTCP or TTCP/DCPA-derived cement under similar implantation conditions.

Setting solution concentration effect on properties of a TTCP/DCPA-derived calcium phosphate cement.

The present work was to investigate the effects of concentration of (NH(4))(2)HPO(4) (diammonium hydrogen phosphate) setting solution on properties of a tetracalcium phosphate (TTCP)/dicalcium phosphate anhydrous (DCPA)--derived calcium phosphate cement. Experimental results indicated that working/setting time of the cement paste decreased with increasing (NH(4))(2)HPO(4) concentration of the setting solution. After being immersed in Hanks' solution for 1 day or longer, the XRD intensities of initial TTCP and DCPA phases largely decreased, while apatite phase became dominant. More residual TTCP phase was observed in the 1 day-immersed cement prepared from higher concentration setting solutions. Compressive strength of the cement immersed for 1 day was consistently higher than that immersed for 30 min or 7 days. After being immersed for 1 day, the average CS value reached a maximal value (59 MPa) as (NH(4))(2)HPO(4) concentration was increased to 0.6 M, beyond that the cement strength decreased and maintained in a relatively high range of 47-54 MPa. Cells incubated with conditioned medium of Al(2)O(3) powder and with blank medium exhibited similar average viability values (0.80 and 0.78, respectively). The OD value with extractions of cement decreased with increasing (NH(4))(2)HPO(4) concentration of the setting solution. The average 0.25, 0.5 and 0.6 M--OD values were 0.78, 0.67 and 0.66, respectively. When setting solution concentration was greater than 0.6 M, the OD value sharply declined to 0.47.

Mechanical testing and osteointegration of titanium implant with calcium phosphate bone cement and autograft alternatives.

The purpose of this study was to evaluate the osteointegration of a titanium (Ti) implant with the calcium phosphate cement (CPC) and autograft prostheses by pull-out test and histological examination. Stems of sixty Ti cylinders were bilaterally inserted into femoral medullary canals in 30 rabbits at the 1st, 4th, 12th, 26th and 70th postoperative weeks. The bone autograft and CPC were filled into the pre-trimmed bone marrow cavity with a polymethyl methacrylate retarder in the distal end, and then a Ti cylinder was inserted into femurs. The CPC group was significantly (p<0.05) associated with a larger pull-out force at 4th (37%) and 12th (62%) weeks compared to the autograft group. The bone area and the bone-to-implant contact ratios of the CPC groups were significantly higher than that of the autograft groups at early healing stage. The histological exams suggest that the CPC enhanced the earlier bone formation around the implant at a period not longer than 12 weeks postoperation. We conclude that CPC graft has the higher ability to facilitate the osteointegration and stabilize the Ti implant at a relatively early stage than the autograft in vivo.

Effect of ball milling on structures and properties of dispersed-type dental amalgam.

OBJECTIVES: The purpose of the present study was to investigate the effect of ball milling on the initial mercury vapor release rate and mechanical properties such as compressive strength, diametral tensile strength and creep value, of the dispersed-type dental amalgam, and comparison was made with respect to two commercial amalgam alloys. METHODS: Ball milling was employed to modify the configuration of the originally spherical-shaped Ag-Cu-Pd dispersant alloy particles. Improvement in mechanical properties while maintaining a low early-stage mercury vapor release rate of the amalgam is attempted. RESULTS: The experimental results show that the amalgam (AmB10) which was made from Ag-Cu-Pd dispersant alloy particles that were ball-milled for 10 min and heat-treated at 300 °C for 2 days exhibited a low initial mercury vapor release rate of 69 pg/mm(2)/s, which was comparable with that of commercial amalgam alloy Tytin (68 pg/mm(2)/s), and was lower than that of Dispersalloy (73 pg/mm(2)/s). As for mechanical properties, amalgam AmB10 exhibited the highest 1h compressive strength (228 MPa), which was higher than that of commercial amalgam alloy Dispersalloy by 72%; while its 24h diametral tensile strength was also the highest (177 MPa), and was higher than that of Dispersalloy by 55%. Furthermore, the creep value of the amalgams made from Ag-Cu-Pd alloy particles with 10 min ball-milling and heat treatment at 300 °C for 2 days was measured to be 0.12%, which was about 20% that of Dispersalloy. SIGNIFICANCE: It is found that ball milling of the dispersant Ag-Cu-Pd alloy particles for 10 min was able to modify the configuration of the alloy particles into irregular-shapes. Subsequently, heat treatment at 300 °C significantly lowered the initial mercury vapor release rate, increased its 1h compressive strength and 1h diametral tensile strength, and lowered its creep value.

In-vitro and in-vivo evaluation of a new Ti-15Mo-1Bi alloy.

The newly developed Ti-15Mo-1Bi alloy not only possesses all the desirable mechanical properties inherent to beta-Ti Mo alloys, but may even enjoy better clinical applicability with the addition of bismuth element, which has long been administered as antibacterial and antitumor medicines. A significantly higher viability of 3T3 cells was demonstrated when they were grown on Ti-15Mo-1Bi alloy than on Ti-15Mo and Ti-6Al-4V. Cells incubated in the medium conditioned by Bi powder at 37 degrees C for 96 h exhibited viability similar to that in the blank group and higher than that in the Ni conditioned group. In vivo experiments using 6 mm x 2 mm metal pin implanted into the epicondyle of rabbit femur revealed superior potential of new bone growth and better persistence of the deposited bony tissue with the Ti-15Mo-1Bi alloy in contrast to that with Ti-6Al-4V. The difference is evident at 12th week and become even more prominent after 26 weeks, with the new bone area measuring 249% of that around Ti-6Al-4V alloy. In summary, Ti-15Mo-1Bi alloys show no cytotoxicity in the in-vitro test and demonstrates superior ability to retain bone in the in-vivo implantation experiment as compared with Ti-6Al-4V alloys.

In vivo testing of nanoparticle-treated TTCP/DCPA-based ceramic surfaces.

This study reports the development of a non-dispersive calcium phosphate cement (nd-CPC) paste containing tetracalcium phosphate and anhydrous dicalcium phosphate that can be used as a filling material in dental and orthopedic applications. The nd-CPC bone cement is compared with two commercial materials, OsteoSet and Collagraft bone grafts. Gross examination of retrieved implants/bone composite samples indicated that none of the implants in this study evoked an inflammatory response. The OsteoSet (calcium sulfate) implant was resorbed too quickly to allow for osteo-remodeling, and it led to the formation of fibrous connective tissue in the fracture site, which remained even 24 weeks after implantation. Histological examination revealed that nd-CPC and Collagraft (hydroxyapatite/tricalcium phosphate/collagen) had greater remodeling and osteoconductive activity than OsteoSet at both 12 and 24 weeks after implantation. Greater remodeling activities were found with nd-CPC cement than with the other materials at 12 weeks after implantation, and the Fourier transform infrared absorption band of carbonate or cellulose derivatives grew from 6 weeks to 24 weeks after implantation in nd-CPC cement. These findings show that nd-CPC compares favorably to commercial bone remodeling materials, and the fact that it is in a paste formulation makes it an ideal material to fill regeneration defects.

Brittle and ductile adjustable cement derived from calcium phosphate cement/polyacrylic acid composites.

OBJECTIVES: Bone filler has been used over the years in dental and biomedical applications. The present work is to characterize a non-dispersive, fast setting, modulus adjustable, high bioresorbable composite bone cement derived from calcium phosphate-based cement combined with polymer and binding agents. This cement, we hope, will not swell in simulated body fluid and keep the osteogenetic properties of the dry bone and avoid its disadvantages of being brittle. METHODS: We developed a calcium phosphate cement (CPC) of tetracalcium phosphate/dicalcium phosphate anhydrous (TTCP/DCPA)-polyacrylic acid with tartaric acid, calcium fluoride additives and phosphate hardening solution. RESULTS: The results show that while composite, the hard-brittle properties of 25wt% polyacrylic acid are proportional to CPC and mixing with additives is the same as those of the CPC without polyacrylic acid added. With an increase of polyacrylic acid/CPC ratio, the 67wt% samples revealed ductile-tough properties and 100wt% samples kept ductile or elastic properties after 24h of immersion. The modulus range of this development was from 200 to 2600MPa after getting immersed in simulated body fluid for 24h. SIGNIFICANCE: The TTCP/DCPA-polyacrylic acid based CPC demonstrates adjustable brittle/ductile strength during setting and after immersion, and the final reaction products consist of high bioresorbable monetite/brushite/calcium fluoride composite with polyacrylic acid.

Bioresorption behavior of tetracalcium phosphate-derived calcium phosphate cement implanted in femur of rabbits.

One primary focus of the present study was to clarify the crucial resorption-location relationship of a recently developed single-phase TTCP-derived calcium phosphate cement (CPC) implanted in rabbit femur in a systematic and quantitative way. Gross examination of retrieved CPC/bone composite samples indicated that the CPC implant did not evoke inflammatory response, necrosis or fibrous encapsulation in surrounding bony tissues. Histological examination revealed excellent CPC-host bone bonding. At 4 weeks, the resorption-induced voids between terminals of bone defects and implants were largely filled with new bone. CPC resorption, new blood vessels, osteocytes, osteons and osteoblast-like cells lining up with active new bone were observed at remodeling sites. At 12 weeks, a new bone network was developed within femoral defect, while CPC became islands incorporated in the new bone. At this stage, crevices filled with lamellar new bone structure were frequently observed. At 24 weeks, bone ingrowth and remodeling activities became so extensive that the interface between residual cement and new bone became less identifiable. In general, at all implant locations the resorption ratio values increased with implantation time, while at all implantation times the resorption ratios decreased from the exterior (cortical site) to the interior (cancellous site) of implants. At the end of 24 weeks, CPC was almost completely resorbed and bone remodeling almost finished at the cortical site.

Effect of heat treatment on structure and properties of dispersed-type dental amalgam.

Effect of heat treatment of Ag-Cu-Pd dispersant particles on the structure, mechanical properties and mercury vapor release rate of an Ag-Cu-Sn/Ag-Cu-Pd-based dental amalgam has been investigated. Experimental results indicate that crystallinity of dispersant Ag-Cu-Pd alloy increases with increasing HTT, with most notable increase occurring between 100 and 200 degrees C. Increasing HTT of Ag-Cu-Pd alloy does not change much of the mercury/alloy ratio for amalgamation, but largely reduces working/setting time of the amalgam. The Ag-Cu-Pd particles in 7 d-aged amalgam are comprised primarily of an outer Sn/Cu/Pd-rich zone and an inner Ag/Cu/Pd-rich zone with eutectic-type morphology and chemical distribution. The annealing-enhanced Pd segregation effect is most significantly observed in the amalgam derived from 300 degrees C-annealed Ag-Cu-Pd dispersant. This amalgam also has the highest compressive strength, highest DTS, and lowest creep rate. Higher annealing temperature causes mechanical property of the amalgam to deteriorate. The initial mercury vapor release rates of amalgams derived from 100, 200 and 300 degrees C-annealed Ag-Cu-Pd dispersant are significantly lower than that derived from 400 degrees C-annealed dispersant.

Bone formation at the surface of low modulus Ti-7.5Mo implants in rabbit femur.

The biocompatibility of the Ti-7.5Mo alloy was examined, because the alloy has a high-strength/modulus ratio and thus is a potential candidate for orthopedic applications. Cell viability assay using 3T3 cells revealed that the Ti-7.5Mo did not induce apparent cell death, when the cells were grown on disks made of the alloy or incubated with the alloy-conditioned medium at 37 or 72 degrees C for 24-72h. The Ti-6Al-4V alloy was used as a control and did not cause apparent cell death either. Moreover, pins of 6mm long and 2mm in diameter of Ti-7.5Mo and Ti-6Al-4V were implanted into the left and right rabbit femurs, respectively, for 6, 12 and 26 weeks. New bone tissue grew to surround the pins, which spanned cortical and marrow regions, as shown by toluidine blue-stained bone sections of the three time points. Strikingly, the amount of new bone encircling the Ti-7.5Mo implant was approximate two-folds of that at Ti-6Al-4V by 26 weeks post-implantation. This facilitation of bone formation could be associated with the unique properties, such as a low modulus and the composition of Mo, of the Ti-7.5Mo.

Gamma-radiation-induced changes in structure and properties of tetracalcium phosphate and its derived calcium phosphate cement.

The purpose of the present study was to investigate the gamma-radiation effect on the structure and properties of the single-phase tetracalcium phosphate (TTCP) powder and its derived calcium phosphate cement (CPC). Experimental results show that low-dosed (0-30 kGy) CPC has a setting time of 10-12 min, while high-dosed (40-120 kGy) CPC has a setting time of 8-10 min. The low dose gamma-radiation does not significantly change porosity volume fraction or compressive strength of the CPC. The pH values of all CPC samples fell in a relatively narrow band, with a band width of 8.5-9.1 (in terms of pH value). With a dose of 10 or 20 kGy gamma-radiation, the TTCP-apatite conversion ratio does not change much. With 30 kGy the conversion ratio significantly increases and reaches a maximum value. With further increases in dose, the conversion ratio quickly declines. With increasing gamma-ray dose, the CPC morphology becomes more porous/loose and apatite particles become larger in size. When exposed to a high dose (120 kGy) of gamma-radiation, TTCP structure is radiation-damaged, and gamma-ray-induced formation of apatite is confirmed by transmission electron microscopic/selected-area diffraction/lattice imaging analyses.

A comparison of the fatigue behavior of cast Ti-7.5Mo with c.p. titanium, Ti-6Al-4V and Ti-13Nb-13Zr alloys.

The purpose of the present study is to compare the high-cycle fatigue behavior of newly developed Ti-7.5Mo alloy with that of c.p. Ti, Ti-13Nb-13Zr and Ti-6Al-4V alloys in their as-cast state. Experimental results indicate that Ti-6Al-4V and c.p. Ti have higher stress-controlled fatigue resistance but lower strain-controlled fatigue resistance than Ti-7.5Mo and Ti-13Nb-13Zr. Among four materials Ti-7.5Mo demonstrates the best strain-controlled fatigue performance. The fracture surfaces of the present materials are comprised of three morphologically distinct zones: crack initiation zone, crack propagation zone, and the final-stage overload zone. The fatigue cracks almost always initiate from casting-induced surface/subsurface pores. A river pattern is observed in the propagation zone. In the overload zone dimples are typically observed. Three factors most significantly affecting the fatigue performance of the present materials are the presence of the casting-induced surface/subsurface pores; the location of the pores; and the inherent mechanical properties of the materials.

Transmission electron microscopic study on setting mechanism of tetracalcium phosphate/dicalcium phosphate anhydrous-based calcium phosphate cement.

This work studied transmission electron microscopy on the setting mechanism of tetracalcium phosphate/dicalcium phosphate anhydrous (TTCP/DCPA)-based calcium phosphate cement. The results suggest the process for early-stage apatite formation as the follows: when TTCP and DCPA powders are mixed in the phosphate-containing solution, the TTCP powder is quickly dissolved because of its higher solubility in the acidic solution. The dissolved calcium and phosphate ions, along with those ions readily in the solution, are then precipitated predominantly on the surface of DCPA particles. Few apatite crystals were observed on the surface of TTCP powder. During the later stages of reaction, the extensive growth of apatite crystals/whiskers, with a calcium/phosphorous ratio very close to that of hydroxyapatite, effectively linked DCPA particles together and also bridged the larger TTCP particles. It is suggested that, when the large TTCP particles are locked in place by the bridging apatite crystals/whiskers, the CPC is set and would not dissolve when immersed in Hanks' solution after 20-40 min of reaction.