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This study investigated the influence of Sr2+ ions incorporation in calcium phosphates formation on the surface of Al2O3/ZrO2 (5 vol%) nanocomposites. For this, Al2O3/ZrO2 samples were shaped, calcined (400 °C for 1 h), and sintered (1500 °C for 2 h). After surface treatment with aqueous phosphoric acid solution (H3PO4), the nanocomposite was biomimetically coated with Simulated Body Fluid (SBF) solutions 5x enriched with different concentrations of Sr2+ ions for 14 days. The samples were then characterized by confocal microscopy, scanning electron microscopy (SEM), contact angle and X-ray diffraction. In general, the formation of phases attributed to both calcium phosphates and strontium on the surfaces of nanocomposites was observed, evidencing the partial replacement of calcium ion (Ca2+) by strontium ion (Sr2+) in the structure of phosphates. Thus, the following phases were identified: tricalcium α-phosphate (α-TCP), tricalcium β-phosphate (β-TCP), tetracalcium phosphate (TTCP), hydroxyapatite (HAp), strontium phosphate (SrP) and Sr-incorporated HAp (Sr-HAp). Moreover, Sr2+ ions incorporation in the structure of phosphates also influenced their morphology. Therefore, Sr2+ ions increase adsorption, bioactivity and osteoconduction of calcium phosphates.

The sintering behaviour and microstructural evolution of two batches of a commercial calcium-deficient hydroxyapatite powder were investigated. First, the sintered density as a function of the starting particle size distribution was studied, and the minimum particle size to get the desired target density was determined. Then, as the two batches were characterized by a slight difference in Ca/P ratio, the role of such ratio on phase and microstructural evolutions during sintering, as well as on mechanical and biological properties was investigated. It was observed that the powder with lower Ca/P ratio underwent significant hydroxyapatite (HA) to β-tricalcium phosphate (β-TCP) decomposition, with a simultaneous formation of tetracalcium phosphate (TTCP). The microstructure of sintered gelcast samples evolved during isothermal sintering at 1300 °C, moving from a starting homogeneous and narrow grain size distribution to a bimodal distribution after 3 h sintering. In fact, over time, large grains decomposed into smaller ones, finally providing a microstructure composed of coarse grains surrounded by plenty of ultra-fine grains. On the contrary, the powder with the higher Ca/P ratio provided a limited HA to β-TCP transformation, and normal grain growth by increasing the sintering time. Such differences lead to different mechanical properties for gelcast samples produced by the two powder batches, as the material with the lower Ca/P ratio affected by lower mechanical strength. Finally, sintered samples from both powders showed in-vitro bioactivity, with a larger surface coverage observed for the lower Ca/P ratio material. The morphology of the apatite layer seemed to be affected by the material composition, too, showing flake-like and needle-like morphologies depending on the Ca/P ratio of the starting powder.

Changes in the structure and phase composition of the hydroxyapatite (HA) plasma coating were established during deposition at the initial temperatures of 20 and 550°C of the titanium substrate and a deposition distance of 95 and 150 mm. The structure of HA coatings was analyzed by SEM and optical microscopy. DSC analysis established the transition temperatures of HA coatings to the equilibrium state. When deposited on a substrate with an initial temperature of 20°C at a deposition distance of 95 mm, a nanostructure with a crystallite size of 21 nm is recorded in the HA coating. When the deposition distance increases to 150 mm, the nonequilibrium phase composition increases, the crystallite size decreases to 12 nm, the HA content decreases from 72 to 61%, the TTCP content decreases from 10 to 5%, and the α-TCP content increases from 17 to 30%. A nonequilibrium nanostructural state passes into a more equilibrium state with the release of heat at temperatures of 615–727°C in DSC studies. The high-temperature α-TCP phase is not recorded when the coating is deposited onto a substrate with an initial temperature of 550°C at a deposition distance of 95 mm, the TTCP content increases by two times, the size of the HA phase crystallites reaches 36 nm, and their size in the sprayed powder is 75 nm. The HA coating has a dendritic microstructure and has no thermal effect during DSC heating at an initial substrate temperature of 550°C.

Tetracalcium phosphate (TTCP) is considered as an ideal potential implant biomaterial due to its good biodegradability, biocompatibility and bioactivity, while the insufficient mechanical properties limit its use in loading-bearing implants. In this work, TTCP-matrix biocermet scaffolds reinforced with Fe particles contents of 15, 30, 45 and 60 vol% were fabricated by selective laser melting (SLM) technology. Experimental results indicated that the introduction of Fe significantly enhances the mechanical properties of TTCP scaffold. Among them, the 45Fe/TTCP biocermet scaffold exhibited the maximum compressive strength (354.12 ± 5.2 MPa), which was about 29.8 times higher than that of pure TTCP scaffold (11.87 ± 0.64 MPa). Meanwhile, its fracture toughness and tensile strength reached 1.88 ± 0.12 MPa m1/2 and 28 ± 2 MPa, respectively, which were higher than the 1.12 ± 0.1 MPa m1/2 and 17 ± 2.1 MPa of pure TTCP scaffold. Herein, the improvement of strength and fracture toughness under compression mode was probably accomplished by the microstructural strengthening and toughening mechanisms such as the crack deflection, crack bridging, and crack tip closure. The reinforcing mechanism under tension mode was probably due to the ductile microvoid coalescence fracture, which commonly observed in the fractured surface of pure Fe under tensile loading. Besides, the biocermet scaffold also has a good ability to induce the formation of bone-like apatite. In short, the porous Fe/TTCP biocermet scaffold with significantly enhanced mechanical properties and good bioactivity is expected to be a potential candidate for load-bearing bone implants.

Titanium-hydroxyapatite (Ti-HA) based composites have been widely investigated as viable materials to be used in dentistry. However, sintering of these composites is very challenging due to decomposition of HA and oxidation of Ti. The objective of this study was to investigate the effect of incorporating a bioactive glass in Ti-HA composites sintered in different atmospheric conditions. The bioactive glass was prepared and added to different percentages of Ti-HA mixtures and divided into two groups. Samples in Group 1 were sintered with air atmosphere, while samples in Group 2 were sintered with vacuum furnace. All samples were later subjected to XRD, SEM, density, micro-hardness, and compression strength tests. XRD results showed that in Group 1, the major phases were assigned to Ti and HA while the minor phases were assigned to oxidised Ti. Whereas, Group 2 showed that the major phases were assigned to HA and the minor phases showed decomposition of HA to Ca3(PO4)2 (TCP) and Ca4(PO4)2O (TTCP). Oxidized Ti was also present in this group. In terms of density, micro-hardness and compression strength, statistical analyses showed that samples in Group 1 have a significant difference (p = 0.000) as compared to those in Group 2. Sintering Ti-HA composites incorporated with BG by using air atmosphere furnace could reduce the decomposition of HA and oxidation of Ti, thus improve the density, micro-hardness and compression strength of the composites. © 2021 Penerbit Universiti Kebangsaan Malaysia. All rights reserved.

Calcium phosphate cement (CPC) is widely used as a repair material for bone defects. However, there is no report on the use of biphasic CPC combined with dental pulp stem cells (DPSCs) for bone tissue engineering. The aim of this study was to construct biphasic CPC and to investigate its effect in the osteogenic stimulation of human DPSCs (hDPSCs) and macrophage polarization. Biphasic CPC was developed by adding different ratios of β-TCP to an equimolar mixture of tetracalcium phosphate (TTCP) and dicalcium phosphate anhydrous (DCPA). The biocompatibility, osteogenic capacity, and inflammatory reactions of the cements were examined. Our results show that biphasic CPC containing both HA and β-TCP was successfully fabricated. The addition of β-TCP did not increase necrosis or apoptosis of DPSCs. Significant increases in hDPSC mineral deposition and osteogenic marker (ColI and ALP) expression were observed in 20% TCP-CPC. The addition of β-TCP did not promote macrophage polarization to a proinflammatory phenotype. In conclusion, biphasic CPC with hDPSCs for bone regeneration was developed for the first time; the biphasic CPC combined with hDPSCs is expected to be used for the repair and regeneration of bone.

A post-treatment of hydrothermal process was conducted to evaluate its effects on the material characteristics and mechanical properties of plasma-sprayed pure HA and HA/20% YSZ coatings. Surface morphology and microstructural changes, relative element contents as well as phase transformations were analyzed by scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffractometry. Both microhardness and Young’s modulus were measured. CaCO3 was found existing before and after the whole process of post-treatment. Peaks of impurity phases such as CaO, TCP, and TTCP of as-sprayed coatings were observed to disappear while HA peaks show a tendency of getting higher and wider over time. Surface morphology of SEM analysis presents a clear deposition behavior of ultrafine HA crystallized particles and cross-sectional analysis exhibits a dense and fine structure. Mechanical properties of HA/20%YSZ coatings are found to be significantly higher than those of pure HA coatings and both of which displayed an overall increase with the heating time, indicating enhanced performances.

Polymeric and tetracalcium phosphate (TTCP)-containing polymeric scaffolds were fabricated using a freeze-drying technique, with a homogenous solution of hydroxyethyl cellulose (HEC)/hyaluronic acid (HA)/gelatin (G) or suspension of 15 or 20% TTCP) particles in HEC/HA/G solution. The morphology, phase composition, chemical bands, and swelling behavior of the scaffold were determined. In vitro fibroblast cell viability and migration potential of the scaffolds were determined by MTT, live/dead staining, and scratch assay for wound healing. The in vivo chick embryo angiogenesis test was also carried out. Finally, the initial antibacterial activity of the scaffolds was determined using Staphylococcus aureus. The scaffolds exhibited an enormous porous structure in which the size of pores increased by the presence of TTCP particles. While the polymeric scaffold was amorphous, the formation of low crystalline hydroxyapatite phase and the initial TTCP particles was determined in the composition of TTCP-added scaffolds. TTCP increased swelling behavior of the polymeric scaffold in PBS. The results demonstrated that the amount of TTCP was a crucial factor in cell life. A high concentration of TTCP could restrict cell viability, although all the scaffolds were nontoxic. The scratch assessments determined better cell migration and wound closure in treating with TTCP-containing scaffolds so that after 24 h, a wound closure of 100% was observed. Furthermore, TTCP-incorporated scaffolds significantly improved the angiogenesis, in the chick embryo test. The presence of TTCP had a significant effect on reducing the bacterial activity and 20% TTCP-containing scaffold exhibited better antibacterial activity than the others.

In this study, ε-polylysine and calcium phosphate precipitation (CPP) methods were employed to induce antibacterial effects and dentin tubule occlusion. Antibacterial effects of ε-polylysine were evaluated with broth dilution assay against P. gingivalis. CPP solution from MCPM, DCPD, and TTCP was prepared. Four concentrations of ε-polylysine(ε-PL) solutions (0.125%, 0.25%, 0.5%, 1%) were prepared. Dentin discs were prepared from recently extracted human third molars. Dentin discs were incubated with P. gingivalis (ATCC 33277) bacterial suspension (ca. 105 bacteria) containing Brain Heart Infusion medium supplemented with 0.1 g/mL Vitamin K, 0.5 mg/mL hemin, 0.4 g/mL L-cysteine in anaerobic jars (37 °C) for 7 days to allow for biofilm formation. P. g–infected dentin specimens were randomly divided into four groups: CPP + 0.125% ε-PL, CPP + 0.25% ε-PL, CPP + 0.5% ε-PL, CPP + 1% ε-PL. On each dentin specimen, CPP solution was applied followed by polylysine solution with microbrush and immersed in artificial saliva. Precipitate formation, antibacterial effects, and occlusion of dentinal tubules were characterized in vitro over up to 72 h using scanning electron microscopy. ε-PL showed 34.97% to 61.19% growth inhibition levels against P. gingivalis (P. g) after 24 h of incubation. On P. g-infected dentin specimens, DCPD + 0.25% ε-PL, and DCPD + 0.5% ε-PL groups showed complete bacterial inhibition and 78.6% and 98.1% dentin tubule occlusion, respectively (p &lt, 0.001). The longitudinal analysis on fractured dentin samples in DCPD and TTCP groups revealed deeply penetrated hydroxyapatite-like crystal formations in dentinal tubules after 72 h of incubation in artificial saliva.

Compared with traditional leads, carbon fiber composite leads have a series of advantages such as lightweight, soft texture, and high conductivity. In this experiment, we attempted to improve the existing carbon-fiber-based TTCP metal leads by using carbon-fiber-graphene-woven leads or conductive cloth, so as to solve a series of defects of TTCP metal leads commonly used in the clinical temporary cardiac pacemaker. We performed a series of measurements, including resistance comparisons and stability checks on the finished product characteristics. The results showed that the resistivity of the whole lead did not change significantly after modification, and the carbon fiber bundle was stable and easily deformed under lower stress to reduce the damage to the myocardium, which had excellent clinical application value.

This study focuses on the effect of boron substitution on the crystallisation behaviour of an important bioceramic phase, tetracalcium phosphate (TTCP, Ca4P2O9), in the 4.5SiO2-3Al2O3-1.5P2O5-5CaO glass system. The influence of phase separation on the crystallisation activation energy as well as the microstructure is systematically analysed. The results indicate that increasing the extent of substitution of B for Al tends to lead to a decrease of the glass-transition temperature (Tg) and crystallisation temperature (Tp). When the substitution amount of B reaches 15 mol%, phase separation is observed. Weak phase separations during glass making can promote the nucleation of crystals due to heterogeneous nucleation with reduced nucleation activation energy. When 50 mol% B is substituted, serious phase separation is observed, with spherical-shaped TTCP phases appearing in the glass. The growth of striped-shaped TTCP crystals is largely suppressed even when a long holding time (1 h) at 900 °C is applied.

In this study, an injectable bone substitute (IBS) was produced by mixing a liquid and powder phase. The liquid phase consisted of 8 wt% methylcellulose (MC), 2.5% gelatin, and different amounts of graphene oxide (GO). The powder phase was composed of tetracalcium phosphate (TTCP), dicalcium phosphate dihydrate (DCPD), and calcium sulfate dihydrate (CSD). The results showed that 1 and 1.5 wt% GO added IBS samples showed higher stability, injectability, rheological properties, and biocompatibility than the other GO added IBS samples. GO addition significantly decreased the setting time, but it did not significantly affect the compressive strength of the samples.

Hydroxyapatite (HA) is widely used as surface coatings on biomedical metal implants because of its excellent biocompatibility and osteoconductivity. In this study, HA coatings were deposited onto Ti-6Al-4V substrates by micro-plasma spraying and then heat treated at 650 °C in a muffle furnace for 3 h and 6 h. XRD results showed that, the HA peaks were sharper than those of corresponding as-sprayed coatings and the amorphous diffuse background was reduced after heat treatment. The transformation from impurity phases such as tetra-calcium phosphate (TTCP) and tri-calcium phosphate (TCP) and amorphous calcium phosphate (ACP) to crystalline HA occurred during the heat treatment. Moreover, the texture intensity was not increased during the re-crystallization of ACP and the transformation of impurity phases into HA. The SEM results showed that nanograins were formed on the coating surface. In addition, with the increase of the holding time, the nanograins become coarse.

In order to acquire a tetracalcium phosphate/magnesium phosphate (TTCP/MPC) composite bone cement that combines the excellent bioactivity of TTCP and high mechanical strength of MPC, the cement was...

The objective of this study was to investigate the effect of heat treatment on setting reaction and mechanical properties of tetracalcium phosphate (TTCP) and dicalcium phosphase (DCP)-based calcium phosphate cements. CPC pastes were prepared at room temperature and heated at different temperatures (from 37 to 60°C) for 10 min. Then, the preheated CPC pastes were rapidly cooled down to room temperature before further heated at 37°C until they set. Three different CPC formulations prepared from different particle sizes of TTCPs were used for the investigation. From the study, it was found that preheating could accelerate setting reaction for all CPCs according to increasing speed of hydroxyapatite (HA) conversion. The higher the preheating temperature, the faster the cements could set. However, at preheating temperature higher than 60°C longer cement setting times were observed. It may be that at high temperature some liquid content in the CPC paste evaporated, resulting in slow setting reaction rate. Compressive strengths of the cements after immersion in simulated body fluid (SBF) for 7 days increased as a result of an increase of HA conversion.

A modified one-step process was used to prepare tetracalcium phosphate/monetite/calcium sulfate hemihydrate powder cement mixtures (CAS). The procedure allowed the formation of monetite and calcium sulfate hemihydrate (CSH) in the form of nanoparticles. It was hypothesized that the presence of nanoCSH in small amounts enhances the in vitro bioactivity of CAS cement in relation to osteogenic gene markers in mesenchymal stem cells (MSCs). The CAS powder mixtures with 15 and 5 wt.% CSH were prepared by milling powder tetracalcium phosphate in an ethanolic solution of both orthophosphoric and sulfuric acids. The CAS cements had short setting times (around 5 min). The fast setting of the cement samples after the addition of the liquid component (water solution of NaH2PO4) was due to the partial formation of calcium sulfate dihydrate and hydroxyapatite before soaking in SBF with a small change in the original phase composition in cement powder samples after milling. Nanocrystalline hydroxyapatite biocement was produced by soaking of cement samples after setting in simulated body fluid (SBF). The fast release of calcium ions from CAS5 cement, as well as a small rise in the pH of SBF during soaking, were demonstrated. After soaking in SBF for 7 days, the final product of the cement transformation was nanocrystalline hydroxyapatite. The compressive strength of the cement samples (up to 30 MPa) after soaking in simulated body fluid (SBF) was comparable to that of bone. Real time polymerase chain reaction (RT-PCR) analysis revealed statistically significant higher gene expressions of alkaline phosphatase (ALP), osteonectin (ON) and osteopontin (OP) in cells cultured for 14 days in CAS5 extract compared to CSH-free cement. The addition of a small amount of nanoCSH (5 wt.%) to the tetracalcium phosphate (TTCP)/monetite cement mixture significantly promoted the over expression of osteogenic markers in MSCs. The prepared CAS powder mixture with its enhanced bioactivity can be used for bone defect treatment and has good potential for bone healing.

Hydrogenophilus thermoluteolus, Thermochromatium tepidum, and Allochromatium vinosum, which grow optimally at 52, 49, and 25 °C, respectively, have homologous cytochromes c′ (PHCP, TTCP, and AVCP, respectively) exhibiting at least 50% amino acid sequence identity. Here, the thermal stability of the recombinant TTCP protein was first confirmed to be between those of PHCP and AVCP. Structure comparison of the 3 proteins and a mutagenesis study on TTCP revealed that hydrogen bonds and hydrophobic interactions between the heme and amino acid residues were responsible for their stability differences. In addition, PHCP, TTCP, and AVCP and their variants with altered stability similarly bound nitric oxide and carbon oxide, but not oxygen. Therefore, the thermal stability of TTCP together with PHCP and AVCP can be tuned through specific interactions around the heme without affecting their gas-binding function. These cytochromes c′ will be useful as specific gas sensor proteins exhibiting a wide thermal stability range.

Biofabrication has been adapted in engineering patient-specific biosynthetic grafts for bone regeneration. Herein, we developed a three-dimensional (3D) high-resolution, room-temperature printing approach to fabricate osteoconductive scaffolds using calcium phosphate cement (CPC). The non-aqueous CPC bioinks were composed of tetracalcium phosphate, dicalcium phosphate anhydrous, and Polyvinyl butyral (PVB) dissolved in either ethanol (EtOH) or tetrahydrofuran (THF). They were printed in an aqueous sodium phosphate bath, which performs as a hardening accelerator for hydroxyapatite formation and as a retainer for 3D microstructure. The PVB solvents, EtOH or THF, affected differently the slurry rheological properties, scaffold microstructure, mechanical properties, and osteoconductivity. Our proposed approach overcomes limitations of conventional fabrication methods, which require high-temperature (>50 °C), low-resolution (>400 μm) printing with an inadequate amount of large ceramic particles (>35 μm). This proof-of-concept study opens venues in engineering high-resolution, implantable, and osteoconductive scaffolds with predetermined properties for bone regeneration.

The objective of this study was to characterise apatite formation ability of a tetra calcium phosphate (TTCP) and dicalcium phosphate anhydrous (DCPA) based desensitising product, TeethmateTM (TM). Methods: Cylindrical samples of TM were produced and immersed in TRIS buffer and artificial saliva (AS) for selected time periods. This was followed by characterisation of the phases formed using 31P Magic Angle - Nuclear Magnetic Resonance Spectroscopy, X-ray powder diffraction and Fourier-transform infrared spectroscopy. Dentine discs treated with the material were analysed by scanning electron microscopy (SEM) to evaluate crystal shape and tubules occlusion. Results: SEM analysis showed the formation of plate-like crystals occluding the dentinal tubules. Solid-state characterisation analyses showed that TM cement samples immersed in TRIS-buffer (pH: 7.3) formed hydroxyapatite phases within approximately six hours of immersion. HA formation was less rapid for the samples stored in AS (pH: 6.5). Conclusions: This study shows that a TTCP-DCPA based desensitising product (TM) converts to HA in vitro and provides an effective option for the treatment of dentine hypersensitivity.

The aim of this work was to develop injectable bone substitutes (IBS) consisting of zoledronic acid (ZOL) and graphene oxide (GO) for the treatment of osteoporosis and metastasis. The powder phase was consisting of tetra calcium phosphate (TTCP), dicalcium phosphate dihyrate (DCPD) and calcium sulfate dihyrate (CSD), while the liquid phase comprised of methylcellulose (MC), gelatin and sodium citrate dihyrate (SC), ZOL and GO. The structural analysis of IBS samples was performed by Fourier Transform Infrared Spectroscopy (FTIR). Injectability, setting time and mechanical strength were investigated. Additionally, in vitro properties of synthesized IBS were analyzed by means of bioactivity, ZOL release, degradation, pH variation, PO43− ion release and cell studies. Overall, all IBS exhibited excellent injectability results with no phase separation. The setting time of the IBS was prolonged with ZOL incorporation while the prolonging effect decreased with GO incorporation. The mechanical properties decreased with ZOL addition and increased with the incorporation of GO. The maximum compressive strength was found as 25.73 MPa for 1.5GO0ZOL incorporated IBS. In vitro results showed that ZOL and GO loaded IBS also revealed clinically suitable properties with controlled release of ZOL, pH value and PO43− ions. In in vitro cell studies, both the inhibitory effect of ZOL and GO loaded IBS on MCF-7 cells and proliferative effect on osteoblast cells were observed. Moreover, the prepared IBS led to proliferation, differentiation and mineralization of osteoblasts. The results are encouraging and support the conclusion that developed IBS have promising physical and in vitro properties which needs to be further validated by gene expression and in vivo studies.

Meng Liu,1,2 Pingsheng Wu2 1Emergency Department, Hunan Provincial People’s Hospital, Medical School of Hunan Normal University, Changsha, People’s Republic of China; 2Cardiology Department, Nanfang Hospital, Southern Medical University, Guangzhou, People’s Republic of ChinaCorrespondence: Pingsheng WuCardiology Department, Nanfang Hospital, Southern Medical University, No. 1838, North Guangzhou Road, Guangzhou, People’s Republic of ChinaTel +86 02061641502Email wupingshengnf@sina.comIntroduction: Temporary transvenous cardiac pacing (TTCP) can lead to potential penetration and occasional perforation of the right ventricular wall. No study to date has analyzed the effect of TTCP on myocardial injury by cardiac troponin (cTn) measurement. The present study was designed to investigate perioperative myocardial injury in elective TTCP in noncardiac surgical settings.Patients and Methods: This retrospective study investigated the data collected from August 2018 through March 2020 from 22 eligible patients who underwent elective TTCP for noncardiac procedures. The patients had a median age of 66 (50– 83) years; six (27.3%) of them were women, and all of them had a baseline cTn < 1 upper reference limit (URL). Cardiac biomarker assays were performed before and after TTCP, and their results were compared.Results: After TTCP, cTn > 1 URL was detected in 20 (91%, N=22) patients. Among these 22 patients, paired t-test comparing assay results before and after TTCP lead insertion showed a mean cTn elevation of 3.599 URL (95% CI: 1.566 to 5.632, P< 0.01), and a mean creatine kinase-MB isoform elevation of 0.1550 URL (95% CI: − 0.01239 to 0.3224, P> 0.05).Conclusion: The study demonstrates a high incidence of myocardial injury associated with TTCP, which should be a matter of concern for the involved physicians.Keywords: temporary pacemaker, temporary transvenous cardiac pacing, myocardial injury, bradycardia, perioperative myocardial injury

Tetracalcium phosphate (TTCP), a potential biological scaffold material, has attracted increasing interest for bone regeneration applications due to its good biodegradability and biocompatibility. In this research, three-dimensional porous TTCP scaffolds were manufactured via selective laser sintering (SLS), and an in-depth and meticulous study on the influence of laser power on the microstructure and mechanical properties of TTCP scaffolds was performed. The results showed that the TTCP particles fused together and formed a solid object due to the decrease in the number of micro-pores in the scaffold as the laser power increased from 6 W to 9 W. The maximum compressive strength that the scaffold could withstand and the strength of the fracture toughness were 11.87 &plusmn, 0.64 MPa and 1.12 &plusmn, 0.1 MPa&middot, m1/2, respectively. When the laser power increased from 9 W to 10 W, the TTCP grains grew abnormally, resulting in diminished mechanical properties. The bioactivity tests showed that the surfaces of the scaffolds were entirely covered by bone-like apatite layers after soaking in simulated body fluid (SBF) for three days, indicating that the scaffolds exhibit excellent bioactivity. Moreover, cell experiments showed that the TTCP scaffolds had good biocompatibility. This study indicated that SLS-fabricated TTCP scaffolds may be a promising candidate for bone regeneration applications.

The objective was to investigate and compare the osseointegrative responses of sandblasted/acid-etched (SLA) and calcium phosphate (CaP) implants in vivo. The CaP implant was prepared by control group of SLA surface modification and anchoring with sintering ceramic of tetracalcium phosphate (TTCP) to form a mechanical interlocking film. Customized screw Ti implants (size O 2.0 mm × 6 mm length) were utilized to histologically examine the bone-to-implant contact (BIC) after implantation. The implant stability quotient scales in the postoperative implants within femurs were recorded. Subsequently, the postoperative implants were scanned using microcomputed tomography (micro-CT), and the topography was examined microscopically to analyze the BIC conditions. The SLA and CaP implant groups showed increased bone mineral density (g/cm3) and BIC (%). Compared with the SLA implant, the CaP implant with TTCP improved the early osteointegration of the BIC at 1-month post-operation and demonstrated quantitative effects on the BIC at 1-month post-operation. SLA and CaP implants all showed good osseointegration through micro-CT analysis (1–6 months). The current findings suggest the CaP anchoring Ti surface demonstrated improvement in early stages of osseointegration and thus shows the potential clinical benefits of TTCP anchoring on Ti surfaces in bone-level solutions.

In this study, the influence of a biodegradable polymer matrix on the conversion of tetracalcium phosphate (TTCP) or TTCP–monocalcium phosphate monohydrate (MCPM) powders was investigated. As a reference, the properties of three calcium phosphate cements (CPCs) based on TTCP or TTCP–MCPM mixtures were discussed. Additionally, the influence of these calcium phosphate (CP) reacting powders on the polymer degradation was studied. Composites were formulated by mixing cross-linkable dimethacrylates of the e-caprolactone/glycolide co-polymer with hydroxyethylmethacrylate, a photo-initiator and TTCP or TTCP–MCPM. The composite samples were set by visible light irradiation. CPC and composite samples were immersed in HEPES at 37 °C. The CPC based on TTCP converted to a carbonated apatite. Adding MCPM to the TTCP powder improved the conversion of TTCP. By varying the MCPM/TTCP ratio it was possible to tailor the conversion reactions so that an apatitic phase could be formed via intermediate products like DPC, DCPD and OCP. In the composites, a mutual interaction between the CP reacting powders and the polymer was observed. The co-polymer and its degradation products influenced the conversion reactions of the CP reacting powders. The degradation products tend to enhance the TTCP conversion after a long immersion time. The conversion of the TTCP–MCPM mixtures was retarded by the polymer matrix although the intermediate products were not altered. The basicity or acidity of the CP reacting powders and their conversion reactions were the main cause for the retarded polymer degradation, which was more pronounced when the basicity of the CP reacting powders increased.

In this study, the natural hydroxyapatite (HA) has been obtained from Corbicula moltkiana shell (CS), which are available as waste from local food processing. The shell can be used as an inexpensive source of natural HA providing at the same time to give added value to food processing by-products as well as reducing the undesirable environmental impact. The synthesized natural HA have been characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), X-ray Fluorescence (XRF) spectrometer and transmission electron microscopy (TEM) studies. The XRD peaks were in agreement with the standard JCPDS file (ICSD-157481). The material obtained at 900 and 1000 °C (HA 900 and HA 1000) have a low crystallinity of hydroxyapatite. At 1000 °C, a tetracalcium phosphate (TTCP) peak was observed. In addition, the crystal size of HA calculated from XRD pattern was found to be a nanosized crystal of 28.90 nm and 6.31 nm for HA 1000 and HA 900 respectively.

Calcium phosphate cements (CPCs) are ideally suited for the local delivery of antibiotics in infected bone defects as they have multiple binding sites for loading various drugs. CPCs can also be substituted with ions such as Ag+, Zn2+, Mg2+, Sr2+, etc., to exhibit extended broad-spectrum antimicrobial activity. Strontium (Sr) in particular is known to enhance the new bone formation and decrease bone resorption. The current work aims to develop a dual action tetracalcium phosphate (TTCP) based cement which releases both the Sr2+ ion and ornidazole antibiotic drug for the treatment of bone infections. The TTCP with Sr2+ ion substitution was prepared by the solid state reaction method and it was used to form ornidazole loaded CPC. The ornidazole loaded cement prepared using 8 at% Sr substituted TTCP (8SCPC-O) showed complete hydroxyapatite (HA) formation in phosphate buffered solution at the end of 1 week. Fine needle-shaped HA crystals were observed in 8SCPC-O cement. In vitro drug release studies showed an accelerated ornidazole release from the 8SCPC-O sample when compared to samples without Sr substitution. Ornidazole releasing cements were found to be biocompatible with skeletal myoblast (L6) cells. Antibacterial activity of ornidazole releasing cement was evident from day 1 onwards against E. coli. The above results suggest 8SCPC-O as a good candidate for treating local bone infections.

The performance of orthopaedic and dental implants counts on the ability to appraise the mechanical properties of biomaterials. In the present study, nanoindentation was used to characterize the mechanical properties of thermally sprayed hydroxyapatite-coated commercial pure titanium (HA/CP-Ti). From the XRD patterns, the as-sprayed HA coating showed an inhomogeneous mixture of polycrystalline and amorphous phases along with the formation of the decomposed constituents including tricalcium phosphate (α-TCP), tetracalcium phosphate (TTCP) and calcium oxide (CaO). The SEM micrographs of HA coating indicated some incompletely melted particles on the surface of flattened droplets, where the average pore size was around 0.8 μm. After the loadunload indentation experiment, a clear severe sink-in deformation feature was observed around the residual indentation impression of the amorphous part. In contrast, pile-up only occurs during loading for the crystalline part of the coating. In addition, the crystalline part of the coating exhibited a Young’s modulus and hardness of around 120.46 and 7.91GPa, respectively, which were almost 8 and 259% higher than that of the bare CP-Ti substrate. This is the first report on the nanoindentation characterization of the inhomogeneous mixture of various phase structures in thermally sprayed HA coatings.

We previously described the gelation mechanism of calcium polyphosphate (CPP) in the presence of water. In this study, we developed novel and injectable poly-dicalcium phosphate dihydrate (P-DCPD) forming cement by the reaction of acidic CPP gel with alkali tetracalcium phosphate (TTCP). The setting reaction mechanism of P-DCPD is due to the intermolecular interaction between CPP gel and TTCP that was supported by XRD, AFM, Raman spectra analysis and SEM. The setting mechanism of P-DCPD is completely different from the classical calcium phosphate cement (CPC) that achieves crystallization by monophosphates reaction. P-DCPD represents a new type of poly-CPCs with significant advantages, including strong mechanical strength, excellent cohesion and easy of handling. More extensive experiments are currently underway to further evaluate the performance of P-DCPD cements, including biocompatibility, degradation behavior and bone defect hearing efficacy, among others.

This study aimed to examine the anti-demineralization capacities of (a) tetracalcium phosphate (TTCP) and dicalcium phosphate anhydrous (DCPA) and 950 ppm fluoride paste, (b) casein phosphopeptide amorphous calcium phosphate paste and (c) 950 ppm fluoride solution using optical coherence tomography (OCT). Enamel blocks were cut from the bovine incisors and treated using one of the above-mentioned three materials or deionized water as control (n=10). All samples were subjected to a demineralization gel for 1 h followed by a remineralization solution for 23 h. This experimental cycle was repeated for 28 days. The specimens were imaged using OCT at baseline and at four stages and measured lesion depth using image analysis software (ImageJ). Repeated measures ANOVA revealed that demineralization time, material and their interaction significantly affected the optical lesion depth (p

A biomimetic nanoporous 50HA–50TiO2 composite surface has been put on a plasma deposition process with the orthopedic use of Ti–6Al–4V alloy in the present research paper. Scanning electron microscope (SEM) fitted out of energy-dispersive spectroscopy (EDS) and X-ray (XRD) was used for the analysis of the coated morphology, elementary, and phase composition of the test. The results show that Ti–6Al–4V’s HA/TiO2-coated surface shows the natural bone-like nanoporous morphology that was favorable for bone growth in the host body around the implant. The study of EDS and XRD revealed that the deposited layer includes Ca, P, O materials, as well as the essential parent product components (Ti, Al, V), and bioactive phase oxides (TTCP, TCP, rutile) formed on the substrate surface. This corrosion resistance and bioactivity of the Ti–5Al–4V was increased significantly. The composite coating tests of nanoporous material have shown that the hardness and roughness values of the HA/TiO2 coating on the surface of the Ti–6Al–4V substratum are 277 HV and 3.59 μm. Overall, the HA–TiO2 coating can be concluded that the Ti–6Al–4V alloy surface has been tailored to the requirements of orthopedic implants.

Background: Calcium phosphate-based compounds are used to treat dental hypersensitivity (DH). Their long-term clinical behaviour needs further research. This study compared the 24-week effectiveness of Teethmate Desensitizer (TD), a pure tetracalcium phosphate (TTCP) and dicalcium phosphate dihydrate (DCPD) powder/water, to that of Dentin Desensitizer (DD), and Bite &amp, White ExSense (BWE), both of calcium phosphate crystallites. Methods: A total of 105 subjects were selected. A random table was utilised to form three groups of 35 subjects. DH was evaluated using the evaporative sensitivity, tactile sensitivity tests, and the visual analogue scale (VAS) of pain. Response was recorded before the application of the materials (Pre-1), immediately after (Post-0), at 1 week (Post-1), 4 weeks (Post-2), 12 weeks (Post-3) and 24 weeks (Post-4). The non-parametric distribution was assessed with the Shapiro&ndash, Wilk statistical test. Intra-group differences for the six time points were evaluated with the Friedman statistical test and the Kruskal&ndash, Wallis test. Results: All the materials decreased DH after 24 weeks in comparison to Pre-1. However, the TTCP/DCPD cement showed the greatest statistical efficiency. Conclusions: The significant decrease of VAS scores produced by TD in the long term suggest the material as the most reliable in the clinical relief of DH.

Calcium phosphate-based bone cements have been widely adopted in both orthopedic and dental applications. Phosphoserine (pSer), which has a natural role in biomineralization, has been identified to possess the functionality to react with calcium phosphate phases, such as tetracalcium phosphate (TTCP) and α-tricalcium phosphate (α-TCP), and form a uniquely adhesive cement. This study investigated the chemical composition and phase evolution of a heterogeneous calcium phosphate (56% TTCP and 15% α-TCP) and pSer cement system with respect to pH. The coordination network of calcium phosphoserine monohydrate was discovered as the predominant crystalline phase of this adhesive apatitic cement system. Furthermore, it was determined that pH has a significant effect on the reaction kinetics of the system, whereby a lower pH tends to accelerate the reaction rate and favor products with lower Ca/P ratios. These findings provide a better understanding of the reaction and products of this adhesive organo-ceramic cement, which can be compositionally tuned for broad applications in the orthopedic and dental spaces. STATEMENT OF SIGNIFICANCE: The application of self-setting calcium phosphate cements (CPCs) in hard tissue regeneration has been a topic of significant research since their introduction to the field 30 years ago. Traditional CPCs, however, are limited by their suboptimal mechanical properties due to their solely inorganic composition. Recently, it was discovered that monomeric phosphoserine (pSer) is capable of serving as a setting reagent for a subset of CPC systems, resulting in an adhesive organo-ceramic composite. Despite its adhesive functionality and biomedical potential, its reaction chemistry and product composition were not well characterized. The present study identifies a calcium phosphoserine coordination network as the primary crystalline phase of this apatitic cement system and further characterizes compositional tunability of the products with respect to pH.

El objetivo del presente trabajo es estudiar, analizar y evaluar el comportamiento del Fosfato tetracálcico fraguable Ca4(PO4)2, su combinación con la hidroxiapatita sintética y su posible aptitud como material de injerto. Como así también diseñar una estrategia terapéutica frente a los defectos estructurales del hueso e identificar factores que favorezcan la neoformación ósea. Se utilizaron 30 ratas endocriadas de cepa Fisher (F344/N), libres de patógenos específicos (SPF), con un peso de 500 gramos y 16 semanas de edad, provenientes del Bioterio de la Facultad de Ciencias Veterinarias de la Universidad Nacional de La Plata. Las mismas fueron escogidas por muestreo aleatorio simple, y luego divididas en 3 grupos de 10 animales cada uno. Todas fueron operadas bajo anestesia general con Ketamina/Xilacina 75 mg/kg + 10 mg/kg por vía IM. Se realizó una perforación de 9 mm de largo, por 3 mm de ancho y 3 mm de profundidad. El grupo 1 fue injertado con fosfato tetracálcico fraguable, el grupo 2 con la combinación de fosfato tetracálcico e hidroxiapatita sintética y el grupo 3, sin tratamiento, fue el grupo control. Una vez operados, los animales integrantes de cada una de las experiencias que se efectuaron, permanecieron alojados bajo observación en el pabellón de Animales de Experimentación de la Cátedra de Animales de Laboratorio de la Facultad de Ciencias Veterinarias de la UNLP, durante 30 días. Posteriormente los animales fueron sacrificados por inhalación de monóxido de carbono, y sus fémures resecados a fin de hacer preparados para su evaluación por microscopía. Estudios que se llevaron a cabo en el Servicio de Microscopía de la Cátedra de Patología General de la Facultad de Ciencias Veterinarias de la UNLP. Las mismas fueron digitalizadas y se evaluó la superficie de hueso regenerado, dentro del defecto. Los distintos elementos de la imagen histológica fueron segmentados en base al color de la tinción (H.E) y posteriormente calculada su superficie mediante un analizador digital de imágenes., Facultad de Odontología

The combination of tetracalcium phosphate (TTCP; Ca4(PO4)2O) and dicalcium phosphate anhydrous (DCPA; CaHPO4) which are known as one system of apatite cements already used in the medical and dental application. In spite of several advantages of apatite cements, such as self-setting ability and biocompatibility, their mechanical strengths are still low. The aim of this study is to improve the mechanical strength of the TTCP-DCPA apatite cement using the hydroxyapatite/collagen nanocomposite (HAp/Col). The apatite cement powder was prepared using an equimolar TTCP and DCPA with addition of 10% and 20% of the HAp/Col. That without the HAp/Col was used as a control group. Each group was mixed with 1 mol/L Na1.8H1.2PO4 aqueous solution at powder/liquid ratio of 0.5 and hardened at 37°C and 100 % of relative humidity for 24 hours. A setting time of the cement was evaluated using Vicat needle according to ISO 1566 for dental zinc phosphate cements. Morphology of the cements set were observed by the scanning electron microscopy (SEM), and crystalline phases were identified by the powder X-Ray diffractometry (XRD). The mechanical strength of the cement set was evaluated by the diametral tensile strength (DTS). The setting times of cements were the shortest for the cement with HAp/Col and the longest for the control. XRD patterns of the cement at 24 hours after mixing revealed that all cements changed into apatite from the mixture of TTCP and DCPA. The DTSs of cements were the highest for the cement with 20% HAp/Col and the lowest for the control with significant differences between the cement with 20 % HAp/Col and respective other two cements. The scanning electron micrographs of the surface and fracture surface of the cements suggested that the cement with HAp/Col showed denser structure in comparison to the control and the HAp/Col fibers and/or sheets covered the fracture surface. The HAp/Col would act as reinforcement fibers as well as an adhesive of apatite granules formed by the reaction between TTCP and DCPA. The setting time and mechanical strength of apatite cement was statistically significant improved by adding 20% HAp/Col.

Purpose Biodegradable polymer fixators have been used widely in oral and maxillofacial surgery for fracture management. However, short-comings such as insufficient mechanical strength, inappropriate degradation time, lack of radiolucency, and foreign body reactions during bone remodeling remain. Material and methods In this study, calcium phosphate ceramic (CPC, including tricalcium phosphate [TCP] and tetracalcium phosphate/dicalcium phosphate [TTCP/DCP]) and poly(e-caprolactone) (PCL) were used to fabricate biodegradable orthopedic fixation devices. Results Different weight ratios of CPC were added to PCL, and the results showed that the PCL/CPC composites had good radiopacity, mechanical properties, and biocompatibility. CPC was transformed into hydroxyapatite when the composites were immersed in simulated body fluid. The PCL/TTCP/DCP composite had a higher compressive strength relative to PCL/TCP after setting, and this self-reinforcing property contributed to the hydration of TTCP/DCP and formation of apatite crystals. Thus, PCL/TTCP/DCP screws were prepared for animal studies. No postoperative mortality or complications were noted 6 months postsurgery. Biodegradation of the PCL/TTCP/DCP screws and newly formed bony tissue around the degraded composites were shown on both micro–computed tomography and histology. No peri-implant bone resorption was noted. Conclusion The self-reinforcing PCL/TTCP/DCP composite can be used to fabricate biodegradable fixators for fracture management in craniomaxillofacial fracture fixation.

Despite its common usage in vertebral augmentation procedures (VAPs), shortcomings of commercial polymethylmethacrylate (PMMA) still remain. Accordingly, injectable and biodegradable composite cements, which are composed of poly(propylene fumarate)/α-tricalcium/hydroxyapatite (PPF/α-TCP/HAP) and PPF/tetracalcium phosphate/dicalcium phosphate (PPF/TtCP/DCP), were developed. A porcine model was used and cylindrical holes in critical size were created at the center of the lateral cortex of vertebral bodies of the lumbar spine. A fixed volume of testing materials and PMMA were randomly injected into the defects. Results showed that both composite groups had a comparable radiolucency as PMMA but a significantly lower setting temperature. Histological inspections revealed new bone formation and remodeling along the border of the two composite cements. New bone substitution and irregular sclerotic bone mantles were found along the composite cements but not in the PMMA group. Radiological and histological changes were observed in the two composite groups and these modifications were diminished along the block boundaries. These findings imply gradual substitution of decomposed composite by new bone formation, which could not be found around the PMMA block. Comparing PPF/α-TCP/HAP with the PPF/TtCP/DCP cement block, smaller particles that were spreading out were observed in the TtCP/DCP group, which represents rapid degradability. In conclusion, the composite cements have advantages such as a low setting temperature, radio-opacity, biodegradability, and osteoconductivity. The injectable PPF/calcium phosphate ceramic composite has the potential to be used in VAPs. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2232-2243, 2017.

Ionic substitutions in hydroxyapatite (HA) scaffolds and self-setting cements containing Sr(2+) ions incorporated are particularly of interest in bone regeneration. To date, the approach widely used to incorporate Sr(2+) ions into HA cements has been the addition of Sr(2+) containing salts, such as SrCO3, SrCl2∙6H2O, or SrHPO4. However, this approach is dependent upon the relative solubility of Sr(2+) containing salts with respect to calcium phosphate (CaP) precursors. Therefore, in the current study Sr(2+) substituted dicalcium phosphate dihydrate (DCPD) was first synthesized and directly reacted with tetracalcium phosphate (TTCP) to form Sr(2+) substituted HA forming cements. Rietveld refinement indicated that after one week of aging in phosphate buffered saline, cements prepared with and without Sr(2+) were composed of 75% HA and 25% unreacted TTCP by weight. Cements prepared with 10% Sr(2+) DCPD exhibited increased compressive strengths in comparison to unsubstituted cements. Increased MC3T3-E1 proliferation and differentiation were also observed on the cements prepared with increasing Sr(2+) content. It was concluded that both the scaffold microstructure and Sr(2+) ion release supported osteogenic differentiation. With respect to osteoclastic differentiation, no statistically significant differences in TRAP activity or cell morphology were observed. This suggests that the amount of Sr(2+) released may have been too low to influence osteoclast formation in comparison to unsubstituted cements. The results obtained herein demonstrate that the use of Sr(2+) substituted DCPD precursors rather than individually separate Sr(2+) containing salts may be a useful approach to prepare Sr(2+) containing HA cements.

This contribution discusses salient properties and functions of hydroxylapatite (HA)-based plasma-sprayed coatings, including the effect on biomedical efficacy of coating thickness, phase composition and distribution, amorphicity and crystallinity, porosity and surface roughness, cohesion and adhesion, micro- and nano-structured surface morphology, and residual coating stresses. In addition, it will provide details of the thermal alteration that HA particles undergo in the extremely hot plasma jet that leads to dehydroxylated phases such as oxyhydroxylapatite (OHA) and oxyapatite (OA) as well as thermal decomposition products such as tri-(TCP) and tetracalcium phosphates (TTCP), and quenched phases such as amorphous calcium phosphate (ACP). The contribution will further explain the role of ACP during the in vitro interaction of the as-deposited coatings with simulated body fluid resembling the composition of extracellular fluid (ECF) as well as the in vivo responses of coatings to the ECF and the host tissue, respectively. Finally, it will briefly describe performance profiles required to fulfill biological functions of osteoconductive bioceramic coatings designed to improve osseointegration of hip endoprostheses and dental root implants. In large parts, the content of this contribution is a targeted review of work done by the author and his students and coworkers over the last two decades. In addition, it is considered a stepping stone toward a standard operation procedure aimed at depositing plasma-sprayed bioceramic implant coatings with optimum properties.

Polymethylmethacrylate (PMMA) cement has been used in orthopedics for more than 70 years. The advantages of PMMA bone cement include high compressive strength, stickiness, deformable ability and rapid self-setting. But the heat produced during polymerization would hinder the recovery. In order to improve the properties, in this research we added tetracalcium phosphate (TTCP) into polymethylmethacrylate cement as TP cement. A serious of characterizations including thermal property study, compression strength and micor-CT evaluation were carried out. According to the results, the polymerization heat was significantly reduced for the TP cement. The compressive strength was also enhanced with TTCP addition. TP-10 had better properties. As to thermal tests, TP-40 showed better results. Micro CT was used to monitor the composition inside the materials, and the results showed that TTCP was well dispersed in the PMMA matrix. The composite PMMA bone cement adding with tetracalcium phosphate seemed to be a potential candidate as low temperature product.

The development of the calcium phosphate ceramics (CPC) using natural materials such as coral, eggshell, bovine bone, fish bone etc., from Indian origin have been reviewed. The CPCs from natural sources has the benefit that they inherit some of the properties of the raw materials such as the macro-and micro-pore structure, optimal composition, similar morphology etc., as well as the advantage of unlimited world wide availability at a very low raw material cost. Hydroxyapatite (HA), carbonated HA and fluorapatite from natural coral genus "Goniopora” has been obtained. Growth factor loaded coralline HA has been found to significantly accelerate early-stage bone formation in in vivo rabbit model studies. Sea shells have been tested as the source of calcium for electrochemical deposition of HA on titanium implants. Deproteinized hydroxyl carbonate apatite phase was formed by heating adult bovine tibia at 500o C. As eggshell could be easily procured, a great deal of effort has been made to utilize this resource as value-added CPCs including nanocrystalline HA (OHA), calcium deficient HA (CDHA), TCP, tetracalcium phosphate (TTCP) etc., which are the most widely used bone substitutes. Also OHA showed higher antibiotic delivery and more controlled protein release profile compared to the synthetic apatites. Eggshell derived CPCs were also found to have minor amount of Mg, Sr, Si and Na ions inherited from the eggshell. As these ions are crucial for bio-mineralization of eggshell, the influence of multi-ions substituted CPCs as a potential bioceramic for bone regenerative applications has been emphasised.

Hydroxyapatite coatings (HAp, Ca 10 (PO 4 ) 6 OH 2 ) were deposited by air plasma spraying onto Ti6Al4V substrates and investigated to determine the depth-dependent behaviour of phase composition, crystallinity, and residual stress using diffractometric techniques. Through-thickness characterisation was carried out by conventional X-ray and synchrotron radiations in reflection and transmission geometries. Results showed HAp together with its thermal decomposition products, tetracalcium phosphate (TTCP), tricalcium phosphate (TCP) and calcium oxide to be present throughout the coating thickness. Quantitative phase identification employing Rietveld refinement showed HAp and TTCP to be the two major phases, with the former decreasing with depth whilst the latter increases. The largest changes were observed adjacent to the coating-substrate interface region. Crystallinity investigation showed a similar trend, revealing a more crystalline near-surface region and increasing amorphisation toward the coating-substrate interface. Residual stress investigation revealed the normal components σ 11 and σ 33 to be tensile and compressive, respectively. The stresses relax and increase to respective minimum and maximum within the first 145 μm. With further penetration depth, both normal stress components became tensile.