Calcium Fluoride Nanoparticles Research Articles

A Comprehensive Narrative Review of Nanomaterial Applications in Restorative Dentistry: Demineralization Inhibition and Remineralization Applications (Part I).

Nanotechnology is extensively employed in various aspects of dentistry, including restorative dentistry, because of its substantial improvement and promising potential in the clinical efficacy of restorative materials and procedures. The main purpose of this review is to explore the different uses of nanomaterials in restorative dentistry. The review is divided into two parts: the current review (Part 1) focuses on the prevention of demineralization and promotion of remineralization, while the upcoming review (Part 2) will discuss the reinforcement of restorative materials and their therapeutic applications. Nanofillers are added to dental materials to boost their antibacterial, anticaries, and demineralization inhibitory capabilities. Additionally, they improve remineralization and enhance both mechanical properties and therapeutic features. The nanoparticles (NPs) used to increase antibacterial and remineralization inhibitions can be classified into two main groups: inorganic and organic NPs. Examples of inorganic NPs include silver, zinc oxide, titanium oxide, and gold. Examples of organic NPs include silica, quaternary ammonium salt monomers, and chitosan NPs. Furthermore, the nanofillers utilized to enhance the process of remineralization include various types such as metals, nano-hydroxyapatite, nano-amorphous calcium phosphate (ACP), dicalcium phosphate NPs, casein phosphopeptide-ACP (CPP-ACP), and calcium fluoride NPs. These uses underscore the potential applications of NPs in restorative dentistry, although there are still some limitations to address.

Evaluation of three physical mixing methods of nanoparticles to orthodontic primer

Background: Demineralization and white spot lesions are the most common complications in fixed orthodontic treatment. It is useful to enhance the remineralization properties of the orthodontic primer by the addition of remineralizing agents. Fluoride and calcium are regarded as the main component of enamel fluorohydroxyapatite crystals. This pilot study compared three mixing methods of calcium fluoride nanoparticles (nCaF2) with conventional orthodontic primer (Transbond XTTM) to develop a primer with enamel remineralization properties. Materials and methods: The nanoparticles were added to Transbond XTTM primer to form 20% (w/w) of the final solution. Three dark plastic bottles were prepared and stored until mixing. The first sample was mixed by a Vortex machine, the second was mixed with an electric agitator, and the third one was mixed with a customized plastic spatula adapted to a dental engine and a straight handpiece. Cured blocks of the developed primer were prepared and were examined for homogeneity, cracks, and agglomeration of the nanoparticles within the primer using Field Emission Scanning Electron Microscopy (FESM). Results: The third Sample showed a continuous distribution of nanoparticles with no apparent cracks or agglomeration of nanoparticles. In contrast, a higher agglomeration was seen in the first sample than in the other two. Conclusion: Mixing of nCaF2 with Transbond XTTM orthodontic primer was best achieved by the customized plastic spatula adapted to a dental engine compared to Vortex and electric agitator machines.

Novel pit and fissure sealant with nano-CaF2 and antibacterial monomer: Fluoride recharge, microleakage, sealing ability and cytotoxicity.

Conventional resin-based sealants release minimal fluoride ions (F) and lack antibacterial activity. The objectives of this study were to: (1) develop a novel bioactive sealant containing calcium fluoride nanoparticles (nCaF2) and antibacterial dimethylaminohexadecyl methacrylate (DMAHDM), and (2) investigate mechanical performance, F recharge and re-release, microleakage, sealing ability and cytotoxicity. Helioseal F served as commercial control. The initial F release from sealant containing 20% nCaF2 was 25-fold that of Helioseal F. After ion exhaustion and recharge, the F re-release from bioactive sealant did not decrease with increasing number of recharge and re-release cycles. Elastic modulus of new bioactive sealant was 44% higher than Helioseal F. The new sealant had excellent sealing, minimal microleakage, and good cytocompatibility. Hence, the nanostructured sealant had substantial and sustained F release and antibacterial activity, good sealing ability and biocompatibility. The novel bioactive nCaF2 sealant is promising to provide long-term F ions for caries prevention.

Obtaining nano calcium fluoride and ammonium sulfate from phosphogypsum

This study presents an efficient and sustainable procedure for converting phosphogypsum (PG) waste, along with hydrofluoric acid (HF) and ammonia (NH3), into valuable materials. The results obtained demonstrate the high efficiency of this proposed procedure, resulting in the synthesis of relatively pure calcium fluoride (CaF2) nanoparticles and ammonium sulfate ((NH4)2SO4). The latter is recommended for agricultural use as a fertilizer, while the obtained CaF2 can be utilized in the metallurgical industry. Furthermore, this procedure not only offers a solution for reducing fluorine gas emissions and managing PG waste but also contributes to the conservation of fluorite reserves.

The beneficial effects of simultaneous supplementation of Lactobacillus reuteri and calcium fluoride nanoparticles on ovariectomy-induced osteoporosis

BackgroundThe development of new strategies to inhibit and/or treat osteoporosis as a chronic systemic disease is one of the most crucial topics. The present study aimed to investigate the simultaneous effects of calcium fluoride nanoparticles (CaF2 NPs) and lactobacillus reuteri ATCC PTA 6475 (L. reuteri) against osteoporosis in an ovariectomized rat model (OVX).MethodsIn this study, 18 matured Wistar female rats were randomly assigned into 6 groups, including control, OVX, sham, OVX + L. reuteri, OVX + CaF2 NPs, and OVX + L. reuteri + CaF2 NPs. We used OVX rats to simulate post-menopausal osteoporosis, and the treatments were begun two weeks before OVX and continued for four weeks. All groups’ blood samples were collected, and serum biomarkers (estrogen, calcium, vitamin D3, and alkaline phosphatase (ALP)) were measured. The tibia and Femur lengths of all groups were measured. Histopathological slides of tibia, kidney, and liver tissues were analyzed using the Hematoxylin and Eosin staining method.ResultsOur results revealed that dietary supplementation of L. reuteri and CaF2 NPs in low doses for 6 weeks did not show adverse effects in kidney and liver tissues. The tibial and femoral lengths of OVX rats as well as the population of osteoblasts and osteocytes and newly generated osteoid in the tibia remarkably increased in the combination therapy group. Moreover, there was a significant increase in serum estrogen levels and a significant decrease in serum calcium and alkaline phosphatase levels in combination treatment groups compared to the OVX groups not receiving the diet.ConclusionsOur results suggest the favorable effects of the simultaneous supplementation of L. reuteri and CaF2 NP to reduce post-menopausal bone loss.Graphical abstract

Effect of nanoparticles on the aggregation and amyloid formation of amyloid-beta peptide.

Nanoparticles are becoming more and more important in medicine and biotechnology. Moreover, due to environmental pollution, the human body is exposed to nanoparticles in the everyday life. Nanomaterials can also affect the aggregation processes of proteins. The Aβ peptides are known for forming amyloid aggregates in the brain in Alzheimer's disease. We used in-house expressed recombinant Aβ(1-42) to study the structure, aggregation kinetics and cytotoxicity of the peptide. We characterized nanoparticles of different materials and studied their effects on the structure and aggregation of Aβ. We followed amyloid formation by monitoring Thioflavin T fluorescence in the presence of nanoparticles. We observed that nanoparticles typically reduce the lag time of aggregation. We found that polystyrene particles bind monomers to a certain saturation point and allow only excess monomers to form fibrils. Calcium fluoride (CaF2) nanoparticles do not bind monomers in a similar fashion, but do influence the secondary structure composition of the resulting amyloid fibrils. We used CD spectroscopy and the BeStSel method to determine the secondary structure composition of the different forms of Aβ. While the main characteristics of Aβ fibrils formed alone is parallel β-sheet, in the presence of CaF2, Aβ forms significant amount of antiparallel β-structure as well. We also conducted cytotoxicity experiments to investigate if nanoparticles alter the toxic effect of Aβ on mouse hippocampal cells. Our preliminary findings suggest that studied particles might reduce cytotoxicity of Aβ if applied in very low concentrations.

Evaluation of Dentin Remineralization with Zinc Oxide and Calcium Fluoride Nanoparticles - An In vitro Study.

Partially demineralized dentin is remineralizable when mineral ions are made available in the near vicinity. Nanoparticles (NPs) have wide applications in remineralization process. Zinc promotes remineralization and has a synergistic effect when combined with fluoride. Hence, zinc oxide and calcium fluoride NPs were considered for dentin remineralization. The aim of this study was to evaluate the remineralizing ability of zinc oxide and calcium fluoride NPs on demineralized dentin individually and in combined form. This was an in vitro study. Forty-eight dentin disks were prepared from the crowns of 12 extracted human molars and were allocated into four groups of 12 each, i.e., Group I - nano zinc oxide (nZnO), Group II - nano calcium fluoride (nCaF2), Group III - combined group (nZnO + nCaF2), and Group IV - artificial saliva (AS, control group). The specimens were demineralized with 37% phosphoric acid and placed in the respective remineralizing solutions for 24 h and 1 month. Calcium (Ca) and phosphorous (P) uptake was measured using energy-dispersive X-ray spectrometry, and structural changes were analyzed using scanning electron microscopy (SEM). One-way analysis of variance, Student's t-test, and post hoc Tukey's test were used for statistical analysis. At 1-month interval, all the groups showed an increase in Ca/P ratio, with highest being the combined group (4.24), followed by nCaF2 (3.30), nZnO (1.71), and AS (1.31) groups, and these differences were statistically significant (P = 0.000). On SEM analysis of dentinal samples at 1 month, depositions were evident in intertubular regions, wherein the highest deposits were observed in the nZnO group, followed by nZnO + nCaF2 and nCaF2 groups. Dentin samples subjected to remineralization with aqueous solutions of nZnO and nCaF2 showed an increase in calcium and phosphorous uptake and also dense granular depositions were evident in intertubular regions of dentin.

Luminescence and thermoluminescence of Er3+-doped CaF2 nanomaterials

Er3+-doped calcium fluoride (CaF2:Er3+) nanoparticles (NPs) have been synthesized by a chemical co-precipitation method. A solution of water ethanol in a 1:1 ratio was used as a solvent. X-ray diffraction and scanning electron microscopy (SEM) results indicated that the fabricated material had a cubic crystal structure and a characteristic cubic shape of Caionscrystals. The main grain size calculated from Scherer’s formula was about 30 nm. The photoluminescence (PL) spectrum of the material showed the specific emissions of Er3+ ion in the CaF2 host lattice and the highest emission intensity was obtained at 2 mol% Er3+ ion. Under a 980 nm laser excitation, the up-conversion luminescence spectra with predominance of red emission were recorded. The thermoluminescence (TL) characteristics of the material were also studied. The obtained CaF2:Er3+ nanocrystals exhibit a high TL sensitivity and linearity to beta (β) radiation doses. The main TL peak is located at 235°C (508 K) and the kinetic parameters corresponding to the trap have been determined by TLAnal software These properties make the phosphor useful for application to estimate exposures of beta rays.

Effect of calcium fluoride nanoparticles in prevention of demineralization during orthodontic fixed appliance treatment: a randomized clinical trial.

White spot lesions (WSLs) are the most common complications of fixed appliance orthodontic treatment. To evaluate the effectiveness of calcium fluoride nanoparticles-containing orthodontic primer (nCaF2-primer) in preventing the incidence of WSLs during orthodontic treatment. Single-centre, double-blinded, split-mouth, randomized clinical trial. The sample involved 31 orthodontic patients (≥12 years). Participants were recruited using a simple nonstratified randomization. Data collection, measurements, and analysis were performed blindly. Outcome measures included comparing the effect of nCaF2-primer with control primer (Transbond) regarding the degree of demineralization (DIAGNOdent pen), Streptococcus mutans (S. mutans) bacterial counting [real-time polymerase chain reaction device (PCR)], and WSLs incidence (pre- and post-operative photographs). The measurements were performed before bonding, 1, 3, and 6 months after bonding and after appliance removal. A two-way repeated measure analysis of variance test (for DIAGNOdent pen scores), and Wilcoxon signed-rank test (for the difference between bacterial counting and WSLs incidence) were used (P < 0.05). Thirty-one patients were recruited and randomized (mean age 17.9 ± 2.45 years). For the primary outcome (DIAGNOdent pen scores) and secondary outcome of S. mutans counting: 31 patients (310 teeth for each group) were included in scoring at T1 and T3, and 30 patients (300 teeth) were included at T6. While for the photographic scores, 26 patients were included after bracket bonding. The demineralization scores showed significant differences at all-time intervals within the 6 months after bracket bonding which was more noticeable after the first month. There was a significant difference in bacterial count between the two primer groups at the T1 only. Regarding photographic scores, there were no significant differences in the WSLs incidence between the two primers groups after brackets removal. No harm was detected during treatment, except the usual pain/gingival irritation. nCaF2-primer effectively decreased demineralization scores within the 6 months after bracket bonding. Moreover, it significantly reduced S. mutans colonization after the first month. However, the tested primer did not have an extra advantage in preventing WSLs development at the clinical level after appliance removal. The trial was registered with ClinicalTrials.gov on 8 May 2021 (registration number: NCT04994314).

Preparation of Calcium Fluoride Nanoparticles by Double-Jet Precipitation

Preparation of Calcium Fluoride Nanoparticles by Double-Jet Precipitation

Screen printed calcium fluoride nanoparticles embedded antibacterial cotton fabric

Calcium fluoride (CaF2) nanoparticles were combined with a stock paste consisting of crosslinkable acrylate copolymer. Screen printing technique was used for coating the prepared mixture on cotton fabric. Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Field Emission-Scanning Electron Microscopy (FE-SEM) were used to characterise the coated cotton fabric. Excellent antibacterial activities against E. coli and S. aureus were observed in the coated cotton. Furthermore, the fabric demonstrated remarkable laundering durability of antibacterial property with a bacterial reduction of over 93% after 15 consecutive washing cycles. The embedding of CaF2 nanoparticles on cotton surface did not affect the intrinsic qualities of fabric, such as water vapour permeability, tensile strength and abrasion resistance. The finished product has a lot of potential and might be used in medical textiles and everyday clothing as an alternative to antibiotic materials.

Polymeric Dental Nanomaterials: Antimicrobial Action.

This review aims to describe and critically analyze studies published over the past four years on the application of polymeric dental nanomaterials as antimicrobial materials in various fields of dentistry. Nanoparticles are promising antimicrobial additives to restoration materials. According to published data, composites based on silver nanoparticles, zinc(II), titanium(IV), magnesium(II), and copper(II) oxide nanoparticles, chitosan nanoparticles, calcium phosphate or fluoride nanoparticles, and nanodiamonds can be used in dental therapy and endodontics. Composites with nanoparticles of hydroxyapatite and bioactive glass proved to be of low efficiency for application in these fields. The materials applicable in orthodontics include nanodiamonds, silver nanoparticles, titanium(IV) and zinc(II) oxide nanoparticles, bioactive glass, and yttrium(III) fluoride nanoparticles. Composites of silver nanoparticles and zinc(II) oxide nanoparticles are used in periodontics, and nanodiamonds and silver, chitosan, and titanium(IV) oxide nanoparticles are employed in dental implantology and dental prosthetics. Composites based on titanium(IV) oxide can also be utilized in maxillofacial surgery to manufacture prostheses. Composites with copper(II) oxide nanoparticles and halloysite nanotubes are promising materials in the field of denture prosthetics. Composites with calcium(II) fluoride or phosphate nanoparticles can be used in therapeutic dentistry for tooth restoration.

The influence of calcium fluoride nanoparticles’ addition on the bond integrity, degree of conversion, ion-release, and dentin interaction of an adhesive

The influence of calcium fluoride nanoparticles’ addition on the bond integrity, degree of conversion, ion-release, and dentin interaction of an adhesive

Mineral Nanomedicine to Enhance the Efficacy of Adjuvant Radiotherapy for Treating Osteosarcoma

It is vital to remove residual tumor cells after resection to avoid the recurrence and metastasis of osteosarcoma. In this study, a mineral nanomedicine, europium-doped calcium fluoride (CaF2:Eu) nanoparticles (NPs), is developed to enhance the efficacy of adjuvant radiotherapy (i.e., surgical resection followed by radiotherapy) for tumor cell growth and metastasis of osteosarcoma. In vitro studies show that CaF2:Eu NPs (200 μg/mL) exert osteosarcoma cell (143B)-selective toxicity and migration-inhibiting effects at a Eu dopant amount of 2.95 atomic weight percentage. These effects are further enhanced under X-ray irradiation (6 MeV, 4 Gy). Furthermore, in vivo tests show that intraosseous injection of CaF2:Eu NPs and X-ray irradiation have satisfactory therapeutic efficacy in controlling primary tumor size and inhibiting primary tumor metastasis. Overall, our results suggest that CaF2:Eu NPs with their osteosarcoma cell (143B)-selective toxicity and migration-inhibiting effects combined with radiotherapy might be nanomedicines for treating osteosarcoma after tumor resection.

Novel rechargeable calcium fluoride dental nanocomposites

ObjectivesComposite restorations with calcium fluoride nanoparticles (nCaF2) can remineralize tooth structure through F and Ca ion release. However, the persistence of ion release is limited. The objectives for this study were to achieve long-term remineralization by developing a rechargeable nCaF2 nanocomposite and investigating the F and Ca recharge and re-release capabilities. MethodsThree nCaF2 nanocomposites were formulated: (1) BT-nCaF2:Bisphenol A glycidyl dimethacrylate (BisGMA) and triethylene glycol dimethacrylate (TEGDMA); (2) PE-nCaF2:Pyromellitic glycerol dimethacrylate (PMGDM) and ethoxylated bisphenol A dimethacrylate (EBPADMA); (3) BTM-nCaF2:BisGMA, TEGDMA, and Bis[2-(methacryloyloxy)ethyl] phosphate (Bis-MEP). All formulations contained 15% nCaF2 and 55% glass particles. Initial flexural strength and elastic modulus, F and Ca ion release, recharge and re-release were tested and compared to three commercial fluoride-containing materials. ResultsBT and BTM nCaF2 composites were 3–4 times stronger and had elastic modulus 2 times that of resin-modified glass ionomer controls. PE-nCaF2 had comparable strength to RMGIs. All nCaF2 composites had significant F and Ca ion release and ion rechargeability. In F and Ca recharging cycles, PE-nCaF2 had the highest ion recharging capability among nCaF2 groups, followed by BT-nCaF2 and BTM-nCaF2 (p < 0.05). For all recharge cycles, ion release maintained similar levels, demonstrating long-term ion release was possible. Furthermore, after the final recharge cycle, nCaF2 nanocomposites provided continuous ion release for 42 days without further recharge. SignificanceNovel nCaF2 rechargeable nanocomposites exhibited significant F and Ca ion release over multiple recharge cycles, demonstrating continuous long-term ion release. These nanocomposites are promising restorations with lasting remineralization potential.

Investigation of the deposition of calcium fluoride nanoparticles on the chips of CaF2 single crystals

The deposition of calcium fluoride nanoparticles on single crystal chips of calcium fluoride was studied. CaF2 nanoparticles were synthesized by co-precipitation from aqueous nitrate solutions using hydrofluoric acid as a fluorinating agent at a batch system. The prepared samples were examined by atomic force microscopy, scanning electron microscopy, transmission electron microscopy and optical transmission. There is an inhomogeneous coating of the substrate surface with submicron particles of about 100–150 nm in size, which are clusters of nanoparticles of 15-20 nm in size. The initial nanoparticles coherently grow on the surface of the crystal substrate. Heat treatment of the substrate-deposited layer composite at 600 °C leads to the coalescence of submicron particles and the formation of a porous layer of a complex structure.

Adhesive bond integrity of Y‐TZP post with calcium fluoride infiltrated resin dentin adhesive: An SEM, EDX, FTIR and micro‐Raman study

The study aimed to synthesize calcium fluoride (CaF2) nanoparticles and compare the push‐out bond strength and viscosity of experimental adhesive (EA) and EA with 5 wt.% CaF2 (CAF‐5%). The CaF2 nanoparticles were synthesized and then characterized with scanning electron microscopy (SEM)‐energy‐dispersive X‐ray spectroscopy (EDX), Fourier transform infrared (FTIR), and micro‐Raman spectroscopies. CaF2 nanoparticles were incorporated in the adhesives to yield two groups; gp‐1: EA‐CAF‐0% (control) and gp‐2: CAF‐5%. Canals of 20 teeth (N = 20) were prepared, and then yttria‐stabilized tetragonal zirconia polycrystalline (Y‐TZP) ceramic posts were cemented. Adhesives were assessed for push‐out bond strength and rheology. CaF2 filler was seen as irregularly shaped agglomerates on SEM. The EDX analysis demonstrated the presence of calcium and fluoride for the CAF‐5% group. The FTIR indicated characteristic bands for CaF2 containing materials. The micro‐Raman spectra of CaF2 nanoparticles demonstrated the presence of CaF2 by showing strong bands at 840 cm−1, 1380 cm‐1, and 1400 cm−1 for fluorine and 950 cm−1 and 1080 cm−1 for calcium ions. The highest push‐out bond strength values were obtained for CAF‐5% group samples (cervical: 9.67 ± 1.46 MPa, apical: 8.66 ± 1.24 MPa), and both adhesives revealed adhesive‐dentin interfacial fractures. The CAF‐5% adhesive also revealed comparable rheological properties with the controls. The addition of CaF2 nanoparticles in the adhesive improved its push‐out bond strength to Y‐TZP post and root dentin, although CAF‐5% showed reduced viscosity on rheological assessment (compared with the controls).

Evaluation of a newly developed calcium fluoride nanoparticles-containing orthodontic primer: An in-vitro study

ObjectivesFluoride and calcium ions have the ability to reduce the formation of white spot lesions (WSL) in enamel. This study aimed to develop a novel orthodontic primer that incorporates calcium fluoride nanoparticles (nCaF2) and investigate its cytotoxic and physical properties as this primer could enhance the remineralization process when used with the conventional acid etching technique. Materials and methodsThree groups of the newly introduced primers were prepared by adding and mixing nCaF2 (Nanoshell Company, USA at 5%, 10%, 20% in weight) to Transbond™ XT orthodontic primers (3M-Unitek, Monrovia, USA). X-Ray Diffraction (XRD) was performed to verify and evaluate the phase of the nanopowders. Field Emission Scanning Electron Microscope (FESEM) observation was used to assess the homogeneity of tested primers, and Energy Dispersive X-Ray Spectroscopy (EDS) was performed to analyze elements of the prepared samples. The three primer groups were compared to the control primer (without the addition of nCaF2) in terms of cytotoxic behavior, homogeneity, agglomeration, shear bond strength (SBS), and adhesive remnant index (ARI). ResultsnCaF2 primers with all the prepared concentrations revealed good homogeneity with no apparent agglomeration after four months of mixing. Cytotoxicity of the new primers was higher than that of the control primer, but it was within the accepted limits of the ISO standards (70% cell viability). While the SBS and ARI values were comparable with the control primer (p > 0.05). ConclusionsThe newly developed orthodontic primers with different concentrations of nCaF2 (5%, 10%, and 20%) showed a homogenous distribution of nCaF2 within the primers with no apparent agglomeration, acceptable cytotoxic level, adequate SBS, and ARI. Future clinical testing of nCaF2-containing orthodontic primer as a preventive measure for WSLs during fixed orthodontic treatment is suggested.

Synthesis of Calcium Fluoride Nanoparticles in a Microreactor with Intensely Swirling Flows

Synthesis of Calcium Fluoride Nanoparticles in a Microreactor with Intensely Swirling Flows

Fabrication of Nd3+ and Yb3+ doped NIR emitting nano fluorescent probe: A candidate for bioimaging applications

The intentional design of rare earth doped luminescent architecture exhibits unique optical properties and it can be considered as a promising and potential probe for optical imaging applications. Calcium fluoride (CaF2) nanoparticles doped with optimum concentration of Nd3+ and Yb3+ as sensitizer and activator, respectively, were synthesized by wet precipitation method and characterized by x-ray diffraction (XRD) and photoluminescence. In spite of the fact that the energy transfer takes place from Nd3+ to Yb3+, the luminescence intensity was found to be weak due to the lattice defects generated from the doping of trivalent cations (Nd3+ and Yb3+) for divalent host cations (Ca2+). These defect centres were tailored via charge compensation approach by co-doping Na+ ion and by optimizing its concentration and heat treatment duration. CaF2 doped with 5 mol% Nd3+, 3 mol% Yb3+ and 4 mol% Na+ after heat treatment for 2 h exhibited significantly enhanced emission intensity and life time. The ex vivo fluorescence imaging experiment was done at various thickness of chicken breast tissue. The maximum theoretical depth penetration of the NIR light was calculated and the value is 14 mm. The fabricated phosphor can serve as contrast agent for deep tissue near infrared (NIR) light imaging.