Thermal crystallization of amorphous calcium phosphate combined with citrate and fluoride doping: a novel route to produce hydroxyapatite bioceramics

Comparison of the remineralization effectiveness of three remineralizing agents on artificial enamel lesions: an in vitro study

INTRODUCTION

Early enamel demineralization can be reversed through remineralization, which restores lost minerals to strengthen enamel and prevent decay.

AIM

This study evaluated the remineralization efficiency of three commercial treatments on artificially demineralized primary enamel.

METHODS

Forty exfoliated primary anterior teeth were demineralized and divided into five groups: untreated control, artificial saliva, fluoridated toothpaste, Curasept toothpaste, and BioMin toothpaste. The treatments were applied for 28 days. Remineralization efficacy was assessed using Vickers microhardness testing, surface roughness measurement, and Scanning electron microscope combined with EDX (SEM-EDX). One-way ANOVA and Tukey's HSD test were used for statistical analysis.

RESULTS

Microhardness and surface roughness tests confirmed BioMin's superior remineralization potential. Scanning electron microscopy showed that untreated enamel exhibited extensive demineralization, whereas treated groups displayed varying degrees of remineralization. BioMin demonstrated the highest calcium, phosphate, and fluoride incorporation, followed by Curasept and fluoridated toothpaste. The artificial saliva group showed no significant improvement over the control.

CONCLUSION

BioMin, followed by Curasept and fluoridated toothpaste, effectively remineralized demineralized enamel. BioMin's bioactive glass formulation provided the highest mineral gain, suggesting its potential for non-invasive enamel restoration in pediatric dentistry.

Citrate-Stabilized Amorphous Calcium Phosphate Nanoparticles as an Effective Adsorbent for Defluorination

Amorphous calcium phosphate (ACP), one of the most important calcium-phosphorus compounds, is widely used in dentistry, orthopedics, and medicine, but is rarely reported for fluoride removal from water. In view of this, sodium citrate-stabilized amorphous calcium phosphate (Cit-ACP) and Cit-ACP calcinated at different temperatures were successfully prepared for fluoride removal. The results showed that the adsorption data of the Cit-ACP sample could be well described by the Langmuir model, and the adsorption kinetic followed the pseudo-second-order model. The maximum adsorption capacity was 27.48 mg/g at pH 7.0 when the fluoride concentration is 100 mg/L. The thermodynamic parameters suggested that the adsorption of fluoride was a spontaneous endothermic process. The XRD, XPS, and Zeta potential analysis of the Cit-ACP sample before and after fluoride removal revealed that, owing to the core-shell structure of the Cit-ACP nanoparticles, the fluoride ions in solution and the calcium ions in shell layer of the Cit-ACP nanoparticles co-promoted the transformation of the core of the Cit-ACP nanoparticles into fluorapatite. Given the simplicity of its preparation and effectiveness of its fluoride removal properties, Cit-ACP would be a potentially economical, efficient, and biocompatible adsorbent for fluoride removal.

Extraction and Characterization of Aceh Bovine Bone-Derived Hydroxyapatite for Applications in Dentistry

OBJECTIVE

 Bone grafts derived from natural hydroxyapatite (HA) are increasingly being explored because they are more economical in terms of production costs compared with commercial HA. HA can be obtained from local cattle slaughter waste in Aceh, Indonesia, which has not been widely studied for its potential for dental applications. This study examines the synthesis and characterization of bovine HA (BHA) derived from Aceh cattle femur through calcination for applications in dentistry.

MATERIALS AND METHODS

 This research began with the cleaning of fresh bones by boiling and soaking them in acetone for 2 hours before 3-hour calcination at varying temperatures. The BHA samples were characterized using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction, scanning electron microscopy with energy dispersive X-ray (SEM-EDX), and particle size analyzer (PSA).

STATISTICAL ANALYSIS

 Data were analyzed using SPSS with a one-way analysis of variance to assess the impact of calcination temperature on the yield and particle size of BHA.

RESULTS

 BHA obtained from calcination at 900°C and 1,000°C showed the highest crystallinity, with values above 84%, and uniform particle distribution. PSA and SEM analysis showed that BHA particles were spherical in submicron size, which became smaller and more uniform but agglomeration did not occur significantly between each increase in calcination temperature. FTIR analysis showed the presence of phosphate, carbonate, and hydroxyl functional groups. Elemental composition analysis using EDX confirmed that essential elements such as calcium and phosphorus were distributed consistently at all temperatures with a Ca/P ratio of 1.7 to 2.3.

DISCUSSION

 Based on the characteristics of crystallinity, particle size, and chemical composition of the obtained BHA, it is considered optimal for bioactivity, which allows stimulation of new bone tissue formation and promotes osseointegration while balancing structural stability. This makes BHA derived from Aceh cattle bones a suitable bone filler candidate for treating alveolar bone defects in hard tissue regeneration. These findings highlight the potential use of cattle bone waste as a sustainable source of HA in dental applications.

CONCLUSION

 These findings suggest that Aceh bovine bones are a viable source for producing quality BHA, potentially contributing to more sustainable and ecofriendly biomaterials for dental applications.

Calcium Phosphate Nanoparticles Functionalized with a Cardio-Specific Peptide

Cardiovascular diseases (CVDs) remain the leading cause of mortality worldwide, highliting the urgent need for new therapeutic strategies. Peptide-based therapies have demonstrated significant potential for treating CVDs; however, their clinical application is hindered by their limited stability in physiological fluids. To overcome this challenge, an effective drug delivery system is essential to protect and efficiently transport peptides to their intended targets. This study introduces two distinct strategies for loading a cardio-specific mimetic peptide (MP), previously designed to modulate L-type calcium channel function in cardiomyocytes, onto calcium phosphate nanoparticles (CaP NPs). MP-loaded CaP NPs were prepared by two different wet precipitation syntheses, one of which involved the use of sodium polyacrylate as a templating agent. Characterization of MP-loaded CaP NPs showed that their crystallinity, size, surface charge, and morphology could be tuned by adjusting the synthesis parameters. In vitro tests on cardiac cells confirmed that both types of MP-loaded CaP NPs are biocompatible with HL-1 cardiomyocytes and restored intracellular calcium flux under stressed conditions, highlighting their therapeutic potential. These results pave the way for further optimization of CaP NP formulations and suggest their potential as a viable nanomaterial for CVD treatment.

Preparation of calcium phosphate ion clusters through atomization method for biomimetic mineralization of enamel

Dental enamel is a mineralized extracellular matrix, and enamel defect is a common oral disease. However, the self-repair capacity of enamel is limited due to the absence of cellular components and organic matter. Efficacy of biomimetic enamel mineralization using calcium phosphate ion clusters (CPICs), is an effective method to compensate for the limited self-healing ability of fully developed enamel. Preparing and stabilizing CPICs presents a significant challenge, as the addition of certain stabilizers can diminish the mechanical properties or biosafety of mineralized enamel. To efficiently and safely repair enamel damage, this study quickly prepared CPICs without stabilizers using the atomization method. The formed CPICs were evenly distributed on the enamel surface, prompting directional growth and transformation of hydroxyapatite (HA) crystals. The study revealed that the mended enamel displayed comparable morphology, chemical composition, hardness, and mechanical properties to those of the original enamel. The approach of repairing dental enamel by utilizing ultrasonic nebulization of CPICs is highly efficient and safe, therefore indicating great promise.

Application of a calcium and phosphorus biomineralization strategy in tooth repair: a systematic review

Biomineralization is a natural process in which organisms regulate the growth of inorganic minerals to form biominerals with unique layered structures, such as bones and teeth, primarily composed of calcium and phosphorus. Tooth decay significantly impacts our daily lives, and the key to tooth regeneration lies in restoring teeth through biomimetic approaches, utilizing mineralization strategies or materials that mimic natural processes. This review delves into the types, properties, and transformations of calcium and phosphorus minerals, followed by an exploration of the mechanisms behind physiological and pathological mineralization in living organisms. It summarizes the mechanisms and commonalities of biomineralization and discusses the advancements in dental biomineralization research, guided by insights into calcium and phosphorus mineral biomineralization. This review concludes by addressing the current challenges and future directions in the field of dental biomimetic mineralization.

Amorphous Calcium Phosphate and Amorphous Calcium Phosphate Carboxylate: Synthesis and Characterization

Amorphous calcium phosphate (ACP) is the first solid phase precipitated from a supersaturated calcium phosphate solution. Naturally, ACP is formed during the initial stages of biomineralization and stabilized by an organic compound. Carboxylic groups containing organic compounds are known to regulate the nucleation and crystallization of hydroxyapatite. Therefore, from a biomimetic point of view, the synthesis of carboxylate ions containing ACP (ACPC) is valuable. Usually, ACP is synthesized with fewer steps than ACPC. The precipitation reaction of ACP is rapid and influenced by pH, temperature, precursor concentration, stirring conditions, and reaction time. Due to phosphates triprotic nature, controlling pH in a multistep approach becomes tedious. Here, we developed a new ACP and ACPC synthesis approach and thoroughly characterized the obtained materials. Results from vibration spectroscopy, nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), true density, specific surface area, and ion release studies have shown a difference in the physiochemical properties of the ACP and ACPC. Additionally, the effect of a carboxylic ion type on the physiochemical properties of ACPC was characterized. All of the ACPs and ACPCs were synthesized in sterile conditions, and in vitro analysis was performed using MC-3T3E1 cells, revealing the cytocompatibility of the synthesized ACPs and ACPCs, of which the ACPC synthesized with citrate showed the highest cell viability.

Remineralization Efficacy of Four Remineralizing Agents on Artificial Enamel Lesions: SEM-EDS Investigation

Dental remineralization represents the process of depositing calcium and phosphate ions into crystal voids in demineralized enamel, producing net mineral gain and preventing early enamel lesions progression. The aim of the present study was to qualitatively and quantitatively compare the remineralizing effectiveness of four commercially available agents on enamel artificial lesions using Scanning Electron Microscopy (SEM) combined with Energy Dispersive Spectroscopy (EDS) techniques. Thirty-six extracted third molars were collected and randomly assigned to six groups (n = 6), five of which were suspended in demineralizing solution for 72 h to create enamel artificial lesions, and one serving as control: G1, treated with a mousse of casein phosphopeptide and amorphous calcium−phosphate (CPP-ACP); G2, treated with a gel containing nano-hydroxyapatite; G3, treated with a 5% SF varnish; G4, treated with a toothpaste containing ACP functionalized with fluoride and carbonate-coated with citrate; G5, not-treated artificial enamel lesions; G6, not demineralized and not treated sound enamel. G1−G4 were subjected to pH cycling over a period of seven days. Analyses of the specimens’ enamel surfaces morphology were performed by SEM and EDS. Data were statistically analyzed for multiple group comparison by one-way ANOVA/Tukey’s test (p < 0.05). The results show that the Ca/P ratio of the G5 (2.00 ± 0.07) was statistically different (p < 0.05) from G1 (1.73 ± 0.05), G2 (1.76 ± 0.01), G3 (1.88 ± 0.06) and G6 (1.74 ± 0.04), while there were no differences (p > 0.05) between G1, G2 and G6 and between G4 (2.01 ± 0.06) and G5. We concluded that G1 and G2 showed better surface remineralization than G3 and G4, after 7 days of treatment.

Amorphous calcium phosphate, the lack of order is an abundance of possibilities

For almost three decades from its discovery, amorphous calcium phosphate (ACP) was not considered a suitable biomaterial due to its structural instability. Thanks to its unique properties in respect to crystalline calcium phosphate phases, nowadays ACP is used in promising devices for hard tissue regeneration. Here we have highlighted the features of ACP that were harnessed to create excellent biomaterials for dental remineralization, self-setting bone cements, drug delivery, and coatings of prostheses. Its current limitations as well as future perspectives of development were concisely described. Despite more research works are needed, we envisage that the future of ACP is bright.

Calcium phosphate nanoparticles for potential application as enamel remineralising agent tested on hydroxyapatite discs

Calcium phosphate exhibits excellent biocompatibility, and with particle size in the nanoscale, calcium phosphate nanoparticles (CPNPs) were explored to replace the hydroxyapatite lost in the nanoporous teeth due to dental erosion. CPNPs (2% w/v) colloidally stabilised by sodium citrate were synthesised via co-precipitation. They were characterised in terms of particle size, morphology, crystallinity, Ca/P ratio and calcium ion release. To ensure uniformity of the substrate, hydroxyapatite (HA) discs were examined as an alternative substrate model to enamel. They were eroded in acetate buffer (0.5 M; pH 4.0) at various timepoints (1, 5, 10, 30 min, and 2, 4 h), and their physical differences compared to enamel were assessed in terms of surface microhardness, surface roughness and step height. The remineralisation properties of the synthesised CPNPs on eroded HA discs at different pH levels were investigated. It was established that CPNPs were heterogeneously deposited on the HA discs at pH 9.2, whereas newly precipitated minerals from CPNPs were potentially formed at pH 6.2.

Synthetic amorphous calcium phosphates (ACPs): preparation, structure, properties, and biomedical applications

Amorphous calcium phosphates (ACPs) represent a metastable amorphous state of other calcium orthophosphates (abbreviated as CaPO4) possessing variable compositional but rather identical glass-like physical properties, in which there are neither translational nor orientational long-range orders of the atomic positions. In nature, ACPs of a biological origin are found in the calcified tissues of mammals, some parts of primitive organisms, as well as in the mammalian milk. Manmade ACPs can be synthesized in a laboratory by various methods including wet-chemical precipitation, in which they are the first solid phases, precipitated after a rapid mixing of aqueous solutions containing dissolved ions of Ca2+ and PO43- in sufficient amounts. Due to the amorphous nature, all types of synthetic ACPs appear to be thermodynamically unstable and, unless stored in dry conditions or doped by stabilizers, they tend to transform spontaneously to crystalline CaPO4, mainly to ones with an apatitic structure. This intrinsic metastability of the ACPs is of a great biological relevance. In particular, the initiating role that metastable ACPs play in matrix vesicle biomineralization raises their importance from a mere laboratory curiosity to that of a reasonable key intermediate in skeletal calcifications. In addition, synthetic ACPs appear to be very promising biomaterials both for manufacturing artificial bone grafts and for dental applications. In this review, the current knowledge on the occurrence, structural design, chemical composition, preparation, properties, and biomedical applications of the synthetic ACPs have been summarized.

Bioactive Calcium Phosphate-Based Composites for Bone Regeneration

Calcium phosphates (CaPs) are widely accepted biomaterials able to promote the regeneration of bone tissue. However, the regeneration of critical-sized bone defects has been considered challenging, and the development of bioceramics exhibiting enhanced bioactivity, bioresorbability and mechanical performance is highly demanded. In this respect, the tuning of their chemical composition, crystal size and morphology have been the matter of intense research in the last decades, including the preparation of composites. The development of effective bioceramic composite scaffolds relies on effective manufacturing techniques able to control the final multi-scale porosity of the devices, relevant to ensure osteointegration and bio-competent mechanical performance. In this context, the present work provides an overview about the reported strategies to develop and optimize bioceramics, while also highlighting future perspectives in the development of bioactive ceramic composites for bone tissue regeneration.

The influence of Fe3+ doping on thermally induced crystallization and phase evolution of amorphous calcium phosphate

The present study investigates thermally induced crystallization and phase evolution of amorphous calcium phosphate (ACP) partially substituted with Fe³⁺ ions (M/P = 1.5 : 1).