Method for forming calcium phosphate, kit for forming calcium phosphate, and laser

Abstract

To provide a method for more simply and rapidly forming calcium phosphate which is applicable even to a substrate surface which is not horizontal and a substrate surface which is not smooth, a kit for forming calcium phosphate, and a laser used for the method for forming calcium phosphate.SOLUTION: A method for forming calcium phosphate, comprising the steps of: applying a light absorbent-containing viscous coating material containing a liquid and a light absorbent to a surface of a base material to form a coating film made of the light absorbent-containing viscous coating material on the surface of the base material; and irradiating a surface of the coating film with laser light in a state in which a calcium phosphate supersaturated solution is in contact with the surface of the coating film to precipitate calcium phosphate on the surface of the base material.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for forming calcium phosphate, a kit for forming calcium phosphate, and a laser used in the method for forming calcium phosphate. [Background technology]

[0002] Certain calcium phosphate compounds, such as hydroxyapatite, exhibit excellent biocompatibility and osteoconductivity, and are therefore used in bulk, powder, granular, and other forms in bone filling materials and other medical devices. They are also used in thin film form as surface modifiers for various medical devices, such as artificial hip joints.

[0003] In recent years, the inventors have been working on the development of a technology for selectively, easily, and quickly forming calcium phosphate in target areas on the surface of a substrate by utilizing a laser irradiation method in a supersaturated liquid, which combines physical and chemical processes. This technology is expected to be useful as a new elemental technology for surface modification and high performance of biological tissues or medical devices, which can be used in medical settings, dental laboratories, etc.

[0004] As a technique for forming calcium phosphate on the surface of a substrate, for example, a method is known in which graphite is applied as a light absorber to the surface of the substrate to form a graphite film, and then a supersaturated calcium phosphate solution is brought into contact with the surface of the graphite film, and laser light is irradiated to precipitate calcium phosphate on the surface of the substrate (see, for example, Non-Patent Document 1).

[0005] Furthermore, as one form of the laser irradiation method in a supersaturated liquid for forming calcium phosphate on the surface of a substrate, for example, a method is known in which a certain amount of a liquid containing a light absorber (a liquid in which a light absorber is dissolved in water) is dropped onto the surface of the substrate to form a liquid film, the liquid film is dried and solidified to form a coating film containing the light absorber, and then the surface of the coating film is brought into contact with a supersaturated calcium phosphate solution and irradiated with laser light to precipitate calcium phosphate on the surface of the substrate (for example, see Non-Patent Document 2). [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] Muyang Sun, Nier Wu, Haifeng Chen, “Laser-assisted Rapid Mineralization of Human Tooth Enamel”, Scientific Reports, 2017, 7, 9611. [Non-patent document 2] Ayako Oyane, Ikuko Sakamaki, Maki Nakamura, Kenji Koga, Kanako Shitomi, Saori Tanaka, Hirofumi Miyaji, “Fluoridated Apatite Coating on Human Dentin via Laser-Assisted Pseudo-Biomineralization with the Aid of a Light-Absorbing Molecule”, International Journal of Molecular Sciences, 2022, 23, 15981. Summary of the Invention [Problem to be solved by the invention]

[0007] However, the method described in Non-Patent Document 1 has the following problems. First, graphite, a light absorber, has not been approved as a pharmaceutical product, making it difficult to apply to living organisms. Also, it is difficult to uniformly apply solid graphite to the surface of a substrate, particularly to surfaces with fine irregularities or porous surfaces.

[0008] The method described in Non-Patent Document 2 uses a light-absorbent-containing liquid containing a light-absorbent approved as a pharmaceutical, but has the following problems. First, due to the properties of the light-absorbent-containing liquid dripped onto the surface of the substrate, it is difficult to obtain a thicker coating film or to significantly adjust the thickness of the coating film. Second, if the surface of the substrate is not parallel (horizontal) to the ground surface, it is difficult to maintain a non-dried coating film of the light-absorbent-containing liquid on the surface of the substrate at a certain thickness or more (the liquid will drip downward), making it difficult to apply to uneven or porous surfaces. In fact, when the light-absorbent-containing liquid is applied to the surface of a substrate perpendicular (vertical) to the ground surface, dripping occurs, and the coating thickness does not exceed 0.05 mm even in the non-dried state immediately after application. Furthermore, if a non-dried coating film is formed by applying a light-absorbent-containing liquid to the surface of the substrate and then immediately contacted with a supersaturated calcium phosphate solution, the light absorbent in the coating film will rapidly diffuse and dissipate into the surrounding supersaturated solution. Therefore, it is necessary to leave the coating film to stand and dry for several tens of minutes before contact to form a solid coating film. Furthermore, this drying causes the coating film containing the light absorbing agent to shrink and crack, resulting in areas that are not covered with the coating film containing the light absorbing agent.

[0009] The present invention has been made in consideration of the above circumstances, and aims to provide a simpler and faster method for forming calcium phosphate that can be applied to substrate surfaces that are not horizontal or smooth, a calcium phosphate formation kit, and a laser used in the method for forming calcium phosphate. [Means for solving the problem]

[0010] The present invention has the following aspects. [1] A step of applying a light-absorbing agent-containing viscous coating material containing a liquid and a light-absorbing agent to a surface of a substrate to form a coating film made of the light-absorbing agent-containing viscous coating material on the surface of the substrate; and irradiating the surface of the coating film with a laser beam while the surface is in contact with a supersaturated solution of calcium phosphate, thereby precipitating calcium phosphate on the surface of the substrate. [2] The method for forming calcium phosphate according to [1], wherein the viscous paint containing the light absorber is obtained by mixing the light absorber with water or a liquid containing an additive. [3] The method for forming calcium phosphate according to [2], wherein the additive is a polyhydric alcohol or a polysaccharide. [4] The method for forming calcium phosphate according to any one of [1] to [3], wherein the light absorber is indocyanine green (ICG). [5] The method for forming calcium phosphate according to any one of [1] to [4], wherein the calcium phosphate precipitated on the substrate is composed mainly of any one of hydroxyapatite, octacalcium phosphate, fluorine-containing hydroxyapatite, silver-containing hydroxyapatite, and fluorine- and silver-containing hydroxyapatite. [6] The method for forming calcium phosphate according to any one of [1] to [5], wherein the substrate is tooth substance, titanium metal, dental composite resin, or polyether ether ketone. [7] A vial or syringe containing a light absorbing agent; a vial or syringe containing a liquid for mixing with the light absorber; A calcium phosphate forming kit comprising: two or more vials or syringes containing a raw material solution for a supersaturated calcium phosphate solution. [8] A laser used in the method for forming calcium phosphate according to any one of [1] to [6]. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a calcium phosphate formation method, a calcium phosphate formation kit, and a laser used in the calcium phosphate formation method, which are capable of more simply and quickly forming calcium phosphate even on a substrate surface that is not horizontal or smooth. [Brief explanation of the drawings]

[0012] [Figure 1]FIG. 1 shows the shape retention of paint A and a conventional paint (ICG-containing liquid described in Non-Patent Document 2) (top), and the in-liquid stability of undried coating films made from each paint (bottom). [Figure 2] This shows the viscosity (left) and storage modulus (right) of paint A and a conventional paint. [Figure 3] Scanning electron microscope (SEM) images of the dentin substrate surface (left) and after 30 seconds (right) of laser irradiation in a supersaturated solution (using a NaF-added calcium phosphate supersaturated solution (CP solution) with irradiation distance of 3 mm, output of 3 W, and power density on the irradiation surface of 1.4 W / mm2). [Figure 4] This figure shows a transmission electron microscope (TEM) image (left) of a cross-section of the surface of dentin substrate 30 seconds after laser irradiation in a supersaturated solution (using NaF-added CP solution, irradiation distance: 3 mm, output: 3 W, power density on the irradiation surface: 1.4 W / mm2), and selected area electron diffraction (SAED) patterns (center and right) of region a (precipitation layer) and region b (dentin) in the TEM image. [Figure 5] This figure shows energy dispersive X-ray (EDX) spectra of the dentin substrate surface in the untreated state, after coating A was formed, and after 1 to 30 seconds of laser irradiation in a supersaturated solution (using NaF-added CP solution, irradiation distance: 3 mm, output: 3 W, power density on the irradiated surface: 1.4 W / mm2). [Figure 6] These figures show high-angle anisotropy dark-field (HAADF) images and scanning TEM (STEM)-EDX elemental mapping images of a cross section of the dentin substrate surface after 1 second (left group) or 30 seconds (right group) of laser irradiation in a supersaturated solution (using NaF-added CP solution, irradiation distance: 3 mm, output: 3 W, power density on the irradiation surface: 1.4 W / mm2). [Figure 7] This figure shows SEM images (left group) and SEM-EDX spectra (right) of the dentin substrate surface 30 seconds after laser irradiation in a supersaturated liquid (using NaF-added CP liquid, irradiation distance: 3 mm, output: 3 W, power density on the irradiated surface: 1.4 W / mm2) when coating film A was formed by changing the gap height of the coating film forming spacer from 0.2 mm to 1.5 mm. [Figure 8]These figures show SEM images (far left group) of the surface of an enamel substrate 30 seconds after laser irradiation in a supersaturated solution (using NaF-added CP solution, irradiation distance: 3 mm, output: 3 W, power density on the irradiation surface: 1.4 W / mm2), a cross-sectional TEM image of the surface of the same substrate (second from the left in the top row), SAED patterns (first and second from the right in the top row) of region a (precipitation layer) and region b (enamel) in the TEM image, an HAADF image (second from the left in the bottom row), and a STEM-EDX elemental (fluorine) mapping image (bottom right). [Figure 9] This figure shows SEM images (far left group) of the surface of a cementitious substrate 30 seconds after laser irradiation in a supersaturated liquid (using NaF-added CP liquid, irradiation distance: 3 mm, output: 3 W, power density on the irradiation surface: 1.4 W / mm2), a cross-sectional TEM image of the surface of the same substrate (second from the left in the top row), SAED patterns (first and second from the right in the top row) of region a (precipitation layer) and region b (cementum) in the TEM image, an HAADF image (second from the left in the bottom row), and a STEM-EDX element (fluorine) mapping image (bottom right). [Figure 10] Figure 1 shows an SEM image (left) and SEM-EDX spectrum (right) of the dentin substrate surface 30 seconds after laser irradiation in a supersaturated solution (using an NCP solution (a solution in which the chloride compounds used in preparing the CP solution were replaced with nitrate compounds) containing silver diamine fluoride (0-7 mM), irradiation distance: 3 mm, output: 3 W, power density on the irradiation surface: 1.4 W / mm2). [Figure 11] This figure shows a cross-sectional TEM image (top left) of the dentin substrate surface 30 seconds after laser irradiation in a supersaturated solution (NCP solution containing 3 mM silver diammine fluoride, irradiation distance: 3 mm, output: 3 W, power density on the irradiation surface: 1.4 W / mm2), an SAED pattern (top right) of region a (precipitation layer) in the same TEM image, an HAADF image, and STEM-EDX elemental mapping images (middle and bottom). [Figure 12]This figure shows a cross-sectional HAADF image (top left) of the dentin substrate surface after 30 seconds of laser irradiation in a supersaturated solution (NCP solution with added silver diamine fluoride (3 mM) used, irradiation distance: 3 mm, output: 3 W, power density at the irradiation surface: 1.4 W / mm2), a STEM-EDX spectrum (top right) of region a (precipitation layer) within the HAADF image, a high-resolution TEM image (bottom left), and a fast Fourier transform pattern of the TEM image (bottom right). [Figure 13] Figure 1 shows SEM images (left group) and SEM-EDX spectra (right) of the resin substrate surface in the untreated state, after coating A was formed, and after 3 minutes of laser irradiation in a supersaturated liquid (using NaF-added CP liquid, irradiation distance: 3 mm, output: 1-6 W, power density on the irradiated surface: 0.5-2.8 W / mm2). [Figure 14] These figures show TEM images (top left of each group) of surface precipitates collected from resin substrates 3 minutes after laser irradiation in supersaturated liquid (using CP solution with NaF addition (left group) or without (right group), irradiation distance: 3 mm, output: 6 W, power density on irradiation surface: 2.8 W / mm2), SAED patterns of region a in the same TEM images (top right of each group), HAADF images, and STEM-EDX elemental mapping images (middle and bottom of each group). [Figure 15] Figure 1 shows cross-sectional SEM images (left) and SEM-EDX elemental mapping images (right group) of the surface of resin-filled dentin substrate 3 minutes after laser irradiation in a supersaturated solution (using NaF-added CP solution, irradiation distance: 3 mm, output: 6 W, power density on the irradiation surface: 2.8 W / mm2). [Figure 16] Figure 1 shows SEM images (left group) and SEM-EDX spectra (right) of the titanium substrate surface after anodizing and after 30 or 60 seconds of laser irradiation in a supersaturated solution (using NaF-added CP solution, irradiation distance: 5 mm, output: 9 W, power density on the irradiated surface: 1.8 W / mm2). [Figure 17] Figure 1 shows SEM images (left group) and SEM-EDX spectra (right) of the surface of an anodized titanium substrate 30 seconds after laser irradiation in a supersaturated liquid (using NaF-added CP liquid, irradiation distance: 3-10 mm, output: 9 W, power density on the irradiated surface: 0.5-4.2 W / mm). [Figure 18]Figure 1 shows SEM images (left group) and SEM-EDX spectra (right) of the surface of an anodized titanium substrate 30 seconds after laser irradiation in a supersaturated liquid (using NaF-added CP liquid, irradiation distance: 3 mm, output: 3-9 W, power density on the irradiated surface: 1.4-4.2 W / mm2). [Figure 19] Figure 1 shows a cross-sectional TEM image (top left) of the surface of an anodized titanium substrate 30 seconds after laser irradiation in a supersaturated solution (using NaF-added CP solution, irradiation distance: 3 mm, output: 9 W, power density on the irradiation surface: 4.2 W / mm2), an SAED pattern (top right) of region a in the TEM image, an HAADF image, and STEM-EDX elemental mapping images (middle and bottom). [Figure 20] SEM images (left group) and SEM-EDX spectra (right group) of the surface of an ethylene-vinyl alcohol copolymer substrate (with and without calcium phosphate precoating) 10 seconds after laser irradiation in a supersaturated liquid (using NaF-added CP liquid, irradiation distance: 3 mm, output: 3 W, power density on the irradiation surface: 1.4 W / mm2). [Figure 21] This figure shows SEM images (left group) and SEM-EDX spectra (right) of the resin substrate surface 3 minutes after laser irradiation in a supersaturated solution (NCP solution containing 3 mM diamine silver fluoride, irradiation distance: 3 mm, output: 3 W, power density on the irradiation surface: 1.4 W / mm2). [Figure 22] This figure shows the shape retention of paints prepared by mixing ICG (25 mg) with 0.2 mL of water, a 15% by mass aqueous glycerin solution, or glycerin (top row), and the in-liquid stability of undried coating films made from each paint (bottom row). [Figure 23] This figure shows the viscosity at low shear rate (1.78 s-1) and high shear rate (100 s-1) (left), and the storage modulus at low shear strain (0.01) (right) of paints prepared by mixing ICG (25 mg) with glycerin aqueous solutions (0.2 mL) of various concentrations (0 to 40 mass%). [Figure 24]Figure 1 shows SEM images (left group) and SEM-EDX spectra (right) of the dentin substrate surface 30 seconds after laser irradiation in a supersaturated liquid (using NaF-added CP liquid, irradiation distance: 3 mm, output: 3 W, power density on the irradiation surface: 1.4 W / mm2) when glycerin aqueous solutions of various concentrations (0 to 100 mass%) were used as the ICG mixing liquid. [Figure 25] Figure 1 shows SEM images (left group) and SEM-EDX spectra (right) of the dentin substrate surface 30 seconds after laser irradiation in a supersaturated liquid (using NaF-added CP liquid, irradiation distance: 3 mm, output: 3 W, power density on the irradiated surface: 1.4 W / mm2) when a 0.1 or 0.3 mass% carboxymethylcellulose (CMC) aqueous solution was used as the ICG mixing liquid. [Figure 26] Figure 1 shows SEM images (left group) and SEM-EDX spectra (right) of the dentin substrate surface 30 seconds after laser irradiation in a supersaturated liquid (using NaF-added CP liquid, irradiation distance: 3 mm, output: 3 W, power density on the irradiation surface: 1.4 W / mm2) when a 1 or 10 mass% polyethylene glycol (PEG) aqueous solution was used as the ICG mixing liquid. DETAILED DESCRIPTION OF THE INVENTION

[0013] An embodiment of the method for forming calcium phosphate and the kit for forming calcium phosphate of the present invention will be described. It should be noted that the present embodiment is specifically described to allow a better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

[0014] [Method for forming calcium phosphate] A method for forming calcium phosphate according to one embodiment of the present invention comprises the steps of applying a viscous paint containing a light absorbent to the surface of a substrate to form a coating film consisting of the viscous paint containing the light absorbent on the surface of the substrate (hereinafter referred to as the "first step"), and irradiating the surface of the coating film with a supersaturated calcium phosphate solution in contact with the surface of the substrate with laser light to precipitate calcium phosphate on the surface of the substrate (hereinafter referred to as the "second step").

[0015] "First step" In the first step, the substrate to which the light absorbent-containing viscous coating material is applied is not particularly limited, but examples thereof include tooth tissue, titanium metal, dental composite resin, polyether ether ketone, and the like. Tooth tissue includes dentin, enamel, and cementum. Examples of titanium metal include pure titanium metal, titanium alloys, and those which have been subjected to anodizing treatment, acid treatment, alkali treatment, or the like. The form of the substrate is not limited, and may be a substrate having a smooth surface or a substrate having an uneven surface, such as a substrate having a microscale uneven structure on the surface or a substrate having a porous structure. The surface of the substrate may be pre-treated by calcium phosphate pre-coating, surface roughening, hydrophilization, etc. Pre-coating with calcium phosphate can promote the precipitation of calcium phosphate in the second step. Furthermore, roughening or hydrophilizing the surface of the substrate can improve the adhesion between the calcium phosphate film to be formed and the substrate. Furthermore, in the first step, when the light-absorbing agent-containing viscous coating material is applied, the surface of the substrate does not necessarily have to be horizontal, and the surface of the substrate may be in any orientation or position. The light-absorbing agent-containing viscous paint of the present invention refers to a paint that has fluidity suitable for application to a substrate surface immediately after mixing the light-absorbing agent with a liquid, and exhibits shape retention, allowing it to maintain a certain thickness and shape when applied to the surface of a substrate. Here, a paint that exhibits shape retention refers to a paint that can provide a coating film made of the light-absorbing agent-containing viscous paint with a thickness of 0.05 mm or more (thickness in a wet state immediately after application), even on a vertical surface.

[0016] When preparing a viscous coating containing a light absorber, the liquid into which the light absorber is mixed is not particularly limited as long as it dissolves or uniformly disperses the light absorber, but water or a liquid containing an additive is preferred, and a liquid containing an additive is more preferred for the reasons described below. In order to exhibit both fluidity suitable for application to a substrate and shape retention after application, the light absorber-containing viscous coating is preferably a plastic fluid or pseudoplastic fluid, i.e., a fluid whose viscosity at low shear rates is higher than that at high shear rates.

[0017] From the viewpoint of shape retention after application to the substrate, a low shear rate (1.78 s -1 The viscosity of the light-absorbing agent-containing viscous coating at room temperature (using a parallel-plate rotational viscometer) is preferably 50 mPa·s or more, more preferably 5 Pa·s or more, and even more preferably 10 Pa·s or more. The elastic modulus (storage modulus) of the light-absorbing agent-containing viscous coating is preferably 10 Pa or more to 2000 Pa or less, more preferably 50 Pa or more to 2000 Pa or less, and even more preferably 100 Pa or more to 2000 Pa or less, at low shear strain (0.01, using a parallel-plate rotational viscometer, room temperature). If the viscosity and storage modulus of the coating in the low shear range are below the lower limit values, the coating will have insufficient shape retention, making it difficult to obtain a coating film of a certain thickness on the substrate surface. When such a coating is dripped or applied to an uneven substrate surface or to the surface of a substrate with an uneven or porous structure, the coating will flow due to gravity, resulting in dripping, pooling in recesses, and uneven coating thickness. Furthermore, if the coating film is brought into contact with a supersaturated calcium phosphate solution while it is still wet, the light absorber will quickly diffuse and dissipate into the surrounding supersaturated solution (poor stability in liquid).

[0018] On the other hand, from the viewpoint of fluidity when applying to the substrate, high shear rate (100 s -1 The viscosity of the viscous paint containing a light absorber (measured at room temperature using a parallel plate rotational viscometer) immediately after preparation is preferably 10 Pa s or less, and more preferably 5 Pa s or less. If the viscosity of the paint at high shear rates exceeds the upper limit (10 Pa s), the fluidity of the paint decreases during manual operation, making it difficult to apply it uniformly to the substrate surface.

[0019] The light absorbent in the present invention is a substance that absorbs laser light of a specific wavelength with high efficiency, and in the second step described below, in the process of absorbing and absorbing the laser light, it activates the surface of the base material and heats the surrounding supersaturated calcium phosphate solution, thereby promoting the precipitation of calcium phosphate crystals. Examples of light absorbers having such effects include cyanine-based, porphyrin-based, fluorescein-based, squalium-based, coumarin-based, and rhodamine-based dyes, as well as carbon-based materials, metal-based materials, and metal ions. Among these, cyanine-based dyes such as indocyanine green (ICG), which has been approved as a pharmaceutical, and porphyrin-based dyes such as 5-aminolevulinic acid, methyl aminolevulinate, verteporfin, and talaporfin sodium are preferred, with ICG being particularly preferred from the viewpoints of safety to the living body and light absorption.

[0020] In the second step, a high concentration of the light absorber is preferable for the light-absorbing agent-containing viscous coating to exhibit the effects described in the previous section. However, if the concentration of the light absorber is too high, the fluidity of the coating decreases, making it difficult to mix the light absorber uniformly and to apply it uniformly to the substrate. By appropriately adjusting the light-absorbing agent concentration in the coating, it is possible to obtain a viscous coating that exhibits fluidity suitable for application to the substrate, shape retention after application, and in-liquid stability, and that also contains a high concentration of light absorber. For example, when preparing an ICG-containing viscous paint by mixing water and ICG, the mass concentration of ICG is preferably 9% by mass or more and 12% by mass or less, and more preferably 11% by mass or more and 12% by mass or less. When the mass concentration of ICG is 9% by mass or more and 12% by mass or less, an ICG-containing viscous paint can be obtained that exhibits both fluidity suitable for application to a substrate and shape retention after application, at least immediately after preparation. When the mass concentration of ICG is 11% by mass or more and 12% by mass or less, a viscous paint containing ICG at a high concentration (more than twice that of the paint described in Non-Patent Document 2) can be obtained that exhibits both fluidity suitable for application to a substrate, shape retention after application, and in-liquid stability, at least immediately after preparation. However, high-concentration viscous paints containing light absorbers, prepared by mixing water with light absorbers, are difficult to mix uniformly and have a short usable life (i.e., the time during which they maintain fluidity suitable for application to substrates). For example, when 25 mg of ICG powder is mixed with 0.2 mL of water, the powder remains even after 30 seconds of mixing, and clumps tend to form, making it difficult to prepare a uniform ICG-containing viscous paint. Furthermore, the resulting ICG-containing viscous paint (ICG mass concentration: 11% by mass) rapidly loses its fluidity in air after preparation (after 1.5 minutes of mixing), and uniform application to substrates becomes difficult after 7 minutes. In other words, it is difficult to achieve both shape retention and in-liquid stability after application and good paint handling (ease of light absorber mixing and sufficient usable life).

[0021] The above problem can be solved by using a liquid containing an additive instead of water as the liquid to mix with the light absorber.

[0022] The additives of the present invention are added to a liquid containing a light absorber. By improving the wettability of the light absorber, they facilitate the mixing of the light absorber and extend the usable life of the resulting light absorber-containing viscous coating. The additives are not particularly limited as long as they are non-volatile organic molecules having both hydrophilic and hydrophobic moieties. However, from the viewpoint of biological safety, low-molecular-weight polyhydric alcohols, polysaccharides, proteins, fatty acids, synthetic polymers, and the like that can be used as pharmaceuticals, pharmaceutical additives, or food additives are preferred. Examples of such low-molecular-weight polyhydric alcohols include glycerin, D-sorbitol, ethylene glycol, and propylene glycol. Examples of polysaccharides include carboxymethylcellulose (CMC), sodium alginate, dextran, and starch. Examples of proteins include collagen and gelatin. Examples of fatty acids include calcium stearate and magnesium stearate. Examples of synthetic polymers include polyethylene glycol (PEG), polyvinyl alcohol, sodium polyacrylate, polyvinylpyrrolidone, and carboxyvinyl polymer. Among these additives, low-molecular-weight polyhydric alcohols are preferred because they are easily removed by laser light irradiation in the second step described below. Furthermore, from the viewpoint of extending the usable time, glycerin is particularly preferred among low-molecular-weight polyhydric alcohols because it has a low vapor pressure (high nonvolatility) and excellent hygroscopicity and moisture retention.

[0023] In order to obtain a viscous coating containing a light absorber that exhibits both shape retention and stability in liquid after application, as well as good operability as a coating (ease of mixing the light absorber and sufficient usable time), it is necessary to adjust the concentration of the additive added to the liquid into which the light absorber is mixed to an appropriate range. For example, when glycerin is used as an additive, a light-absorbing agent-containing viscous paint that meets the above requirements can be prepared by mixing 25 mg of ICG with 0.2 mL of a glycerin aqueous solution containing more than 1% by mass but less than 15% by mass. A glycerin concentration of 1% by mass or less results in insufficient improvement in wettability with the ICG powder and insufficient extension of the paint's usable life after preparation. On the other hand, increasing the glycerin concentration to 15% by mass or more reduces the paint's viscosity, reducing its in-liquid stability upon contact with a supersaturated calcium phosphate solution in the second step (prone to diffusion and dissipation of the light-absorbing agent). Increasing the glycerin concentration to 40% by mass or more further reduces the paint's viscosity, impairing not only its in-liquid stability but also its shape retention after application. Therefore, when using a glycerin aqueous solution as the liquid to be mixed with the light-absorbing agent, the glycerin concentration is preferably 2% to 14% by mass. When CMC or PEG is used as an additive, a viscous coating containing a light absorber that meets the above requirements can be prepared by mixing 25 mg of ICG with 0.1% to 0.3% by mass of an aqueous CMC solution or 0.2 mL of a 1% by mass of aqueous PEG solution. In addition to the additives described above, the liquid to be mixed with the light absorber may further contain components that promote the precipitation of calcium phosphate, such as calcium ions, phosphate ions, hydroxide ions, and fluoride ions.

[0024] The method for applying the viscous coating containing the light absorber to the surface of the substrate is not particularly limited, but for example, a method using a syringe, a method using a paintbrush, a method using a brush, a method using a sponge, a method using a spatula, a method using a dispenser, etc. may be used.

[0025] Methods for adjusting the thickness of a coating film made of a light-absorbing agent-containing viscous paint on the surface of a substrate include, but are not limited to, a method using a film thickness adjustment jig to form a coating film of a constant thickness from the light-absorbing agent-containing viscous paint applied to the surface of a substrate. One example of a film thickness adjustment jig is a jig equipped with a concave spacer with a constant gap height. After applying an excess amount of light-absorbing agent-containing viscous paint to the surface of a flat substrate, the surface of the viscous paint is smoothed by sliding the two tip surfaces of the concave spacer against the surface of the substrate, thereby forming a coating film with a thickness corresponding to the gap height (recess depth) of the concave spacer.

[0026] By adjusting the thickness of the coating film, it is possible to adjust the size of the calcium phosphate crystal grains to be precipitated and the thickness of the film consisting of these crystal grains in the second step described below. The thickness of the coating film is not particularly limited, but is preferably 0.1 mm or more and 2.0 mm or less, more preferably 0.2 mm to 1.5 mm, and particularly preferably 0.5 mm, in a wet state immediately after application. For the same viscous paint containing a light absorber, the thicker the coating film, the stronger the effect of solution heating due to laser light absorption by the light absorber, and the faster the calcium phosphate precipitation reaction. As a result, the precipitated calcium phosphate crystals grow larger and the film made of these crystals becomes thicker.

[0027] "Second step" The calcium phosphate supersaturated solution used in the second step refers to a solution supersaturated with respect to calcium phosphate compounds. While the component concentrations and temperature of the calcium phosphate supersaturated solution are not particularly limited, an aqueous solution with a near-neutral pH is preferred. Examples include simulated body fluid (SBF), which has inorganic ion concentrations and a pH (temperature: 36.5°C) similar to those of human body fluids; 1.5SBF, which has an inorganic ion concentration 1.5 times that of SBF; an aqueous solution in which the calcium salt and phosphate concentrations of SBF are increased by 1.5 times and other inorganic salts (except sodium chloride) are removed (CP solution, as described in Example 1 below); and a solution in which the chlorine compounds used as raw materials for the CP solution are replaced with nitrate compounds (NCP solution, as described in Example 2 below). Among these, CP solution and NCP solution are preferred because they can be used at room temperature and maintain a metastable supersaturated state even during irradiation.

[0028] One or more functional components may be added to the calcium phosphate supersaturated solution to improve the functionality of the calcium phosphate to be precipitated. Examples of functional components include ions that replace some of the constituent ions of calcium phosphate, and ions or molecules that co-precipitate with calcium phosphate. Functional components that react with laser light to change the composition or structure may also be used. The composition, structure, and functionality of the calcium phosphate to be precipitated can be controlled depending on the type and concentration of the functional component added to the supersaturated solution.

[0029] For example, adding fluoride ions to a CP solution at a concentration of 1 mM to 3 mM can precipitate fluorine-containing hydroxyapatite crystals. The fluorine-containing hydroxyapatite crystals thus obtained not only have superior acid resistance to hydroxyapatite crystals, but also exhibit antibacterial properties. Furthermore, adding diamminesilver fluoride to an NCP solution at a concentration of 3 mM to 7 mM can precipitate fluorine- and silver-containing hydroxyapatite, which contains silver nanoparticles in addition to fluorine and exhibits even greater antibacterial properties.

[0030] The method for bringing the surface of the substrate on which the coating film has been formed in the first step into contact with the supersaturated calcium phosphate solution is not particularly limited, and examples thereof include a method of immersing the substrate in the supersaturated calcium phosphate solution, a method of continuously dripping or spraying the supersaturated calcium phosphate solution onto the surface of the substrate, and a method of applying the supersaturated calcium phosphate solution to the surface of the substrate. The step of bringing the surface of the substrate on which the coating film has been formed into contact with the supersaturated calcium phosphate solution can be carried out immediately after the first step without going through the step of leaving it to stand and drying.

[0031] The oscillation mode of the laser light irradiated onto the surface of the substrate on which the coating film has been formed, while the surface is in contact with a supersaturated calcium phosphate solution, may be pulse oscillation or continuous wave (CW) oscillation.

[0032] The wavelength of the laser light is not particularly limited, but is preferably a wavelength near the maximum absorption wavelength of the light absorbent used in the first step. When ICG (maximum absorption wavelength: approximately 805 nm) is used as the light absorbent, the wavelength of the laser light is preferably 760 nm or more and 830 nm or less, and more preferably 798 nm or more and 818 nm or less. By using laser light with a wavelength within this optimal range, the coating film on the substrate surface can efficiently absorb the laser light.

[0033] The energy density of the laser light should be equal to or greater than the threshold at which the coating film formed on the substrate surface is removed. If the energy density is less than the threshold, the coating film remains on the substrate surface and it is difficult to induce the calcium phosphate precipitation reaction. The higher the energy density exceeds the threshold, the more accelerated the removal of the coating film and the calcium phosphate precipitation reaction. However, depending on the material of the substrate, if the energy density is too high, it may cause reactions such as melting or ablation of the substrate itself, inhibiting the calcium phosphate precipitation reaction or damaging the substrate.

[0034] From the above, the optimal range of the energy density of the laser beam varies depending on the type and amount of the light absorber contained in the coating film, as well as the substrate. For example, when an ICG-containing viscous coating (25 mg of ICG mixed with 0.2 mL of a 7% by mass glycerin aqueous solution) is applied to the surface of a dental composite resin substrate, the energy density of a CW laser beam with a wavelength of 808 ± 10 nm is 0.5 W / mm 2 Over 2.8W / mm 2 Less than 1.4W / mm is preferable. 2 Over 2.8W / mm 2 The following is more preferred:

[0035] The irradiation time of the laser light is not particularly limited, but it may be the time required to remove the coating film formed on the surface of the substrate and promote the calcium phosphate precipitation reaction. The longer the irradiation time, the larger and more the precipitated calcium phosphate crystal grains grow, and the thicker the film made of these crystal grains becomes. The light-absorbing agent-containing viscous coating material of the present invention can thicken the coating film applied to the substrate surface by several times or more, thereby accelerating the calcium phosphate precipitation reaction. Therefore, calcium phosphate can be formed even with a relatively short laser irradiation time. For example, when an ICG-containing viscous coating material (25 mg of ICG mixed with 0.2 mL of a 7% by mass glycerin aqueous solution) is applied to the surface of a cementitious substrate (to a film thickness of approximately 0.5 mm) and then irradiated with laser light in a supersaturated calcium phosphate solution, a calcium phosphate film approximately 0.5 μm thick can be formed in just 30 seconds of irradiation.

[0036] As described above, by irradiating the surface of a substrate on which a coating film made of a viscous paint containing a light absorber has been formed with a laser beam while the surface is in contact with a supersaturated calcium phosphate solution, calcium phosphate precipitates on the surface of the substrate, and a film made of calcium phosphate is formed on the surface of the substrate.

[0037] The size of the precipitated calcium phosphate crystal grains and the thickness of the film made of these crystal grains can be adjusted by the amount (concentration) of the light absorber in the coating film, the thickness of the coating film, as well as the energy density of the laser light, the irradiation time, the ion concentration, pH, temperature, etc. of the calcium phosphate supersaturated solution.

[0038] According to the calcium phosphate formation method of this embodiment, a coating film with excellent shape retention of 0.05 mm or more (thickness in a wet state immediately after application) made of a viscous paint containing a light absorber can be formed on the surface of a substrate with an uneven or porous structure or an uneven surface (such as an animal tooth). The coating film surface can be contacted with a supersaturated calcium phosphate solution and then irradiated with laser light, thereby precipitating calcium phosphate on the surface of the substrate to form a film made of calcium phosphate. Furthermore, the thickness of the coating film can be adjusted using the light absorber-containing viscous paint, thereby controlling the size of the calcium phosphate crystal grains and the thickness of the film made of these crystal grains. Furthermore, because the light absorber-containing viscous paint has excellent in-liquid stability, the substrate after coating can be immediately contacted with a supersaturated calcium phosphate solution and irradiated with laser light (without a drying process).

[0039] [Calcium phosphate formation kit] A calcium phosphate formation kit according to one embodiment of the present invention comprises a first vial or syringe containing a light absorber, a second vial or syringe containing a liquid for mixing with the light absorber, and third and fourth vials or syringes containing raw material solutions of a supersaturated calcium phosphate solution. In addition to these, the calcium phosphate formation kit may further comprise a tool for adding the contents of each vial or syringe to the other vial or syringe, a mixing / application applicator, a film thickness adjustment tool, and a supersaturated solution administration tool.

[0040] The first vial or syringe is for containing the light absorber in a light-shielding and sealed state. The material of the first vial or syringe is not particularly limited as long as it does not deteriorate the light absorber or is not deteriorated by the light absorber, and examples thereof include light-shielding polypropylene, polyethylene, polystyrene, glass, etc.

[0041] The second vial or syringe is for storing in a sealed state the liquid to be mixed with the light absorber. The material of the second vial or syringe is not particularly limited as long as it is not deteriorated by the liquid, and examples thereof include polypropylene, polyethylene, polystyrene, and glass.

[0042] The third and fourth vials or syringes are intended to contain the plurality of raw material solutions of the above-mentioned supersaturated calcium phosphate solution in a sealed state. The material of the third and fourth vials or syringes is not particularly limited as long as it is not deteriorated by the supersaturated calcium phosphate solution, and examples thereof include polypropylene, polyethylene, polystyrene, glass, etc. Since the supersaturated calcium phosphate solution has poor storage stability (it is prone to precipitation), it is desirable to prepare it each time it is used by mixing an unsaturated raw material solution with calcium phosphate.

[0043] Examples of tools for adding the contents of one vial or syringe to another include a syringe adapter or a three-way stopcock for connecting two syringes (e.g., a third and fourth syringe) to mix the contents, a syringe needle for adding the contents of one syringe to another vial, and a syringe with a needle for adding the contents of one vial to another vial.

[0044] The mixing / application applicator is a tool used to prepare a viscous paint containing a light absorber by mixing the liquid contained in the second vial or syringe with the light absorber contained in the first vial or syringe, and then to apply the mixed viscous paint containing a light absorber to the surface of a substrate. Applicators with excellent mixing and stirring capabilities include hard brushes that can withstand the viscosity of the paint, applicators with sponge-like or brush-like tips, paintbrushes, and spatulas. Separate applicators may be used for mixing and application.

[0045] The film thickness adjusting jig is a jig for forming a coating film of a constant thickness made of a viscous paint containing a light absorber on the surface of a substrate. For example, a jig equipped with a concave spacer with a constant gap height can be used. The material of the film thickness adjusting jig is not particularly limited, but in order to suppress adhesion of the viscous paint, it is preferable that the surface that comes into contact with the paint is made of a material with excellent releasability, such as fluororesin, polyolefin resin, or silicone resin.

[0046] The supersaturated solution administration tool is a tool for bringing a supersaturated calcium phosphate solution into contact with the surface of a substrate on which a coating film has been formed. Examples of the supersaturated solution administration tool include a container for holding the supersaturated calcium phosphate solution on the surface of the substrate, and a syringe for dripping the supersaturated calcium phosphate solution onto the surface of the substrate. The third and fourth vials or syringes may be used as they are as the supersaturated solution administration tool.

[0047] A method for forming calcium phosphate using the calcium phosphate forming kit of this embodiment will be described.

[0048] The light absorber contained in the first vial or syringe is mixed with the liquid contained in the second vial or syringe. To mix the liquid and the light absorber, for example, the liquid from the second vial or syringe is added to the first vial or syringe containing the light absorber, and the liquid and the light absorber are mixed in the first vial or syringe using a mixing / application applicator to form a viscous paint containing the light absorber.

[0049] Next, the viscous paint containing the light absorber is applied to the surface of the substrate using a mixing / application applicator, forming a non-dried coating film made of the light absorber solution on the surface of the substrate.

[0050] Next, the thickness of the non-dried coating film formed on the surface of the substrate is made constant using a film thickness adjusting jig.

[0051] Next, the raw materials for the calcium phosphate supersaturated solution contained in the third and fourth vials or syringes are mixed using a syringe adapter, a three-way stopcock, a syringe needle, or the like to prepare a calcium phosphate supersaturated solution.

[0052] The coating film is brought into contact with the supersaturated calcium phosphate solution by pouring the supersaturated calcium phosphate solution into a container such as a beaker and immersing the substrate on which the coating film has been formed therein, or by dropping the supersaturated calcium phosphate solution onto the surface of the substrate on which the coating film has been formed.

[0053] Next, the coating film that has been brought into contact with the calcium phosphate supersaturated solution is irradiated with laser light to precipitate calcium phosphate on the surface of the substrate, thereby forming a film made of calcium phosphate on the surface of the substrate.

[0054] The calcium phosphate forming kit of this embodiment can form a calcium phosphate film on a substrate having an uneven or porous structure or on the surface of an uneven substrate (such as an animal tooth surface). Furthermore, the thickness of the calcium phosphate film can be adjusted by adjusting the thickness of the coating film made of the light-absorbing agent-containing viscous paint. [Example]

[0055] The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0056] [Example 1] (Laser irradiation in supersaturated solution on dentin, enamel, and cementum substrates) After forming a coating film consisting of an ICG-containing viscous paint on the surface of each substrate (dentin, enamel, and cementum), fluoride-containing apatite was precipitated on the substrate surface by irradiating it with laser light in a calcium phosphate supersaturated solution (CP solution) containing sodium fluoride (NaF).The effect of the coating thickness on the structure of the precipitated layer was also confirmed.

[0057] "method" (Preparation of dentin, enamel, and cementum substrates) After obtaining informed consent, teeth extracted for medical purposes were provided. After cutting, the teeth were ultrasonically cleaned to prepare dentin, enamel, and cementum substrates.

[0058] (Preparation of NaF-added CP solution) First, a metastable CP solution was prepared. The CP solution was prepared by adding and dissolving NaCl (final concentration: 142 mM), K2HPO4·3H2O (1.50 mM), HCl (40 mM), and CaCl2 (3.75 mM) in ultrapure water while stirring, and then adding trishydroxymethylaminomethane (50 mM) and the required amount of 1 M HCl in small amounts to adjust the pH to 7.40 (25 °C). The CP solution was stored refrigerated and used within one month of preparation. Just before laser irradiation in the supersaturated solution, NaF (1 mM) was added to the CP solution and the solution was stirred for 20 minutes to prepare the NaF-added CP solution.

[0059] (Preparation of ICG-containing viscous paint (paint A)) As a liquid for mixing with ICG, a 7% by mass glycerin aqueous solution was prepared by diluting glycerin (for molecular biology, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) with ultrapure water. 0.2 mL of this 7% by mass glycerin solution was added to ICG (Diagnogreen; C 43 H 47 A viscous paint containing ICG (hereafter referred to as "Paint A") was prepared by adding 25 mg of powder of ICG (N2NaO6S2, manufactured by Daiichi Sankyo Co., Ltd.) to a glass vial and quickly mixing for 1.5 minutes using an applicator equipped with a small plastic brush (GC Disposable Applicator II, manufactured by GC Corporation). After coating the surface of the substrate with the applicator, two tip surfaces of recessed spacers with various gap heights (recess depths) (0.2 mm to 1.5 mm) were slid against the surface of the substrate while being in close contact with the surface of the substrate, smoothing the surface of the coating. In this way, non-dried coating films (hereinafter referred to as "Coating Film A") of various thicknesses made of Coating A were formed. Unless otherwise specified below, spacers with a gap height of 0.5 mm were used. For comparison, the low-viscosity paint described in Non-Patent Document 2 (hereinafter referred to as "conventional paint") was prepared by adding and mixing 0.5 mL of distilled water to a glass vial containing 25 mg of the above-mentioned ICG powder.

[0060] (Laser irradiation in supersaturated liquid) The substrate on which coating film A was formed was immersed in 10 mL of NaF-added CP solution (kept at 25°C until immediately beforehand), and immediately, using a diode laser (S-LASER, manufactured by GC Corporation) connected to an optical fiber with a core diameter of 300 μm, the surface of the substrate was irradiated with near-infrared laser light (continuous wave oscillation) with a wavelength of 808 ± 10 nm for various times up to 30 seconds. The laser light output was set to 3 W, and the distance from the tip of the fiber to the substrate surface (hereinafter referred to as the irradiation distance) was adjusted to 3 mm, resulting in a power density of 1.4 W / mm 2 It was decided.

[0061] "result" (Properties of Paint A (compared to conventional paint)) Ten microliters of each paint was dropped onto a glass dish. The dish was then immediately raised to a vertical position, and the shape retention of the paint was assessed by the presence or absence of dripping after 30 seconds. As shown in the upper panel of Figure 1, Paint A remained on the vertical surface for over 30 seconds without dripping, whereas the conventional paint did drip. The same procedure was performed on a glass slide, with the drip amount increased to 40 μL. The thickness of Paint A after 30 seconds on the vertical surface was estimated to be 1.3–1.4 mm using a square wet film thickness meter (TQC Sheen SP402, Industrial Physics). The thickness of the upper portion of the conventional paint, which dripped, was estimated to be less than 0.05 mm. Next, the substrate on which the coating A made from Paint A had been formed was immersed in a NaF-added CP solution (without a drying process), and the diffusion of ICG (green) was observed after 30 seconds. As shown in the lower left of Figure 1, there was almost no diffusion of ICG into the liquid, confirming the good stability of paint A in the liquid. On the other hand, when the conventional paint was dropped (0.2 μL / mm 2When the dentin substrate was immersed in the NaF-added CP solution without a drying process, significant diffusion of ICG was confirmed (Figure 1, bottom right). From the above, it was found that Paint A exhibits better shape retention and stability in liquid than conventional paints. Furthermore, Paint A maintained fluidity suitable for application to the substrate even 7 minutes after preparation. The viscoelasticity of paint A was measured using a parallel plate rotational viscometer (ONRH-1B, manufactured by Ohnagiken Co., Ltd., disk diameter: 12.5 mm, gap: 0.5 mm). -1 ~6s -1 ) (measured at the third cycle) exceeded 10 Pa·s, while at high shear rates (100 s -1 ) was below 5 Pa·s (Figure 2, left). Furthermore, the storage modulus of Paint A (measured at the second cycle) exceeded 300 Pa at low shear strains (below 0.05), but dropped to around 100 Pa at high shear strains (1.0) (Figure 2, right). In other words, Paint A is a pseudoplastic fluid that increases in viscosity and elasticity in an environment close to a static state, which is thought to give it both the fluidity suitable for application to substrates and the shape retention that enables the formation of thick films on vertical surfaces. Furthermore, the high viscosity at low shear rates is thought to contribute to the in-liquid stability of Paint A. On the other hand, conventional paints have a shear rate of 1.8 s -1 ~100s -1 The conventional paint exhibited a low viscosity (less than 50 mPa·s) regardless of shear strain, and its storage modulus was less than 10 Pa at any shear strain (0.05 to 1). In other words, the conventional paint was found to be a Newtonian fluid with low viscosity and low elasticity. This result indicates that the conventional paint has poor shape retention and stability in liquid.

[0062] (Laser irradiation of dentin substrate in supersaturated solution) Figure 3 shows scanning electron microscope (SEM) images of the untreated dentin substrate surface and after 30 seconds of laser irradiation. Submicron-sized particles were newly observed on the substrate surface after irradiation (Figure 3, right group). Using a microsampling method with a focused ion beam processing and observation device, cross-sectional structures of the substrate surface after 30 seconds of irradiation were collected, thinned, and observed by transmission electron microscope (TEM). TEM observation revealed that the precipitate layer was 0.2 μm–0.25 μm thick and seamlessly bonded to the dentin substrate surface (Figure 4, left). Furthermore, the particle groups (arrows) observed in the SEM image were found to be columnar particles elongated roughly perpendicular to the dentin substrate surface. Selected-area electron diffraction (SAED) patterns for region a (precipitate layer) and region b (dentin) in the TEM image on the left of Figure 4 are shown in Figure 4, center and right, respectively. Based on the distance from the center of the diffraction spots and the angle between the spot directions in the SAED pattern of the precipitate layer (Figure 4, center), all of the spots were identified as diffraction spots originating from apatite crystals. The SAED pattern revealed the apatite 00l orientation (strongly represented by 002 and 004) and the 100 orientation. From this image, most of the columnar crystals in the precipitate layer were elongated in the 001 direction (the c-axis direction of the apatite crystals). Combined with the TEM image (Figure 4, left), this elongation direction was considered to be roughly perpendicular to the surface of the dentin substrate. These findings confirmed that the precipitate layer formed on the surface of the dentin substrate was an apatite crystalline layer. Meanwhile, the SAED pattern of the dentin region (Figure 4, right) showed Debye rings (rings corresponding to 121, 211, and 112 diffractions), indicating the random orientation of apatite crystals, and within these, arc-shaped patterns corresponding to the apatite 00l diffraction (002 and 004 diffractions) were also observed. Figure 5 shows the results of an energy dispersive X-ray (EDX) analysis of the untreated dentin substrate surface, after coating A was applied, and after 1 to 30 seconds of laser irradiation. The SEM-EDX spectrum of the untreated dentin substrate clearly showed peaks for calcium, phosphorus, oxygen, and carbon derived from the dentin. After coating A was applied, the calcium and phosphorus peaks almost disappeared, replaced by peaks for sodium and sulfur, which are components of ICG. Furthermore, an increase in the surface concentration of carbon, the main component of ICG, was observed. After 1 second of irradiation, the sodium and sulfur peaks almost disappeared, revealing a surface composition nearly identical to that of the untreated dentin substrate. This is likely due to the ICG contained in the coating absorbing the laser light and being decomposed and removed. After 10 to 30 seconds of irradiation, the spectrum showed trace peaks for calcium and phosphorus, as well as fluorine. This result indicates the presence of trace amounts of fluorine in the deposition layer. Figure 6 shows high-angle anisotropic dark-field (HAADF) images of the cross section of the substrate surface 1 second (left group) and 30 seconds (right group) after irradiation, as well as two-dimensional EDX elemental mapping images obtained by scanning transmission electron microscope (STEM). After 1 second of irradiation, a small amount of sulfur, indicating the presence of a coating film, was observed on the substrate surface, but no precipitates were observed. After 30 seconds of irradiation, a precipitate layer approximately 0.2 μm thick containing calcium, phosphorus, and fluorine was observed on the substrate surface. The results in Figures 3–6 confirmed that a fluoride-containing apatite layer was formed on the surface of the dentin substrate 30 seconds after irradiation. Fluorine is thought to be incorporated into the crystal lattice by replacing some of the hydroxyl groups in the apatite crystals as fluoride ions. Furthermore, the sulfur and carbon signal intensities at the interface between the precipitate and the dentin after 30 seconds of irradiation were comparable to those of the substrate (no contrast enhancement, indicating residual sulfur or carbon, was observed) (Figure 6, right group). This result is consistent with the SEM-EDX results (Figure 5), indicating that coating A on the substrate surface had almost completely disappeared 30 seconds after laser irradiation. The removal and disappearance of the coating exposed the apatite in the dentin on the substrate, bringing it into contact with the supersaturated solution. This, in turn, locally heated the surrounding supersaturated solution (which increased the mass transfer rate and the degree of supersaturation), likely promoting the rapid precipitation and growth of apatite crystals. When the irradiation time was kept constant at 30 seconds and the gap height of the spacer for forming the coating was changed from 0.2 mm to 1.5 mm to thicken Coating A, no significant difference was observed in the surface composition of the substrate (Fig. 7, right), but the precipitated columnar crystals tended to develop larger (Fig. 7, left group). It was thought that the thickness of the precipitated layer also increased as the coating thickness increased. This is thought to be because the thicker coating enhanced the effects of solution heating, etc., due to the coating absorbing the laser light.

[0063] (Laser irradiation of enamel substrate in supersaturated solution) Figure 8 shows the results for the enamel substrate. As shown in the SEM images on the far left of Figure 8, clusters of particles approximately 0.1 μm in diameter were observed on the substrate surface 30 seconds after laser irradiation. Cross-sectional TEM analysis revealed that these particles were columnar, elongated perpendicular to the substrate surface, and the thickness of the precipitate layer consisting of these clusters was 0.15 μm to 0.2 μm. Fluorine mapping by STEM-EDX and SAED analysis revealed that the precipitate layer on the enamel substrate surface was a fluoride-containing apatite crystal layer, similar to that of the dentin substrate. Furthermore, the SAED patterns of the precipitate layer (region a) and the enamel (region b) were nearly identical, indicating that the crystals in the precipitate layer inherited the orientation of the apatite crystals in the enamel substrate.

[0064] (Laser irradiation of cementitious substrates in supersaturated liquid) Figure 9 shows the results for the cementitious substrate. After 30 seconds of laser irradiation, clusters of particles approximately 0.15 μm in diameter were observed on the substrate surface (the leftmost cluster in Figure 9). Cross-sectional TEM analysis revealed that these particles were columnar, elongated roughly perpendicular to the substrate surface, and the thickness of the precipitate layer comprised of these clusters was 0.3 μm to 0.4 μm. The SAED pattern of the precipitate layer (region a) showed diffraction spots (002 and 004) corresponding to c-axis-oriented apatite and Debye rings (corresponding to the 121, 211, and 112 diffractions of apatite) indicating random crystal orientation. Combining these results with the results of STEM-EDX analysis, it was confirmed that a precipitate layer composed of fluoride-containing apatite crystals was formed on the surface of the cementitious substrate, similar to that of the dentin and enamel substrates.

[0065] [Example 2] (Change of supersaturated solution) By adding diamminesilver fluoride (Ag(NH3)2F) to a supersaturated calcium phosphate solution, apatite containing silver, which exhibits stronger antibacterial properties in addition to fluoride, was precipitated on the surface of dentin substrate.

[0066] "method" Because the CP solution used in Example 1 contains chloride ions, silver chloride precipitates immediately upon addition of diaminesilver fluoride. Therefore, a chloride-ion-free metastable calcium phosphate supersaturated solution (NCP solution) was prepared in the same manner as in Example 1, except that the hydrochloride (NaCl, CaCl) and hydrochloric acid (1M HCl) used in preparing the CP solution were replaced with nitrate (NaNO, Ca(NO)·4H0) and nitric acid (1M HNO), respectively. Just before laser irradiation in the supersaturated solution, diaminesilver fluoride (38% Saffolide® Dental Solution, manufactured by Toyo Pharmaceutical Co., Ltd.) was added to the NCP solution at various concentrations (0 mM, 3 mM, 5 mM, and 7 mM) and stirred to prepare diaminesilver fluoride-added NCP solutions.

[0067] In the same manner as in Example 1, the dentin substrate on which coating film A was formed was immersed in 10 mL of NCP solution containing diamine silver fluoride, and a laser beam (irradiation distance: 3 mm, output: 3 W, power density on the irradiation surface: 1.4 W / mm2 ) was irradiated for 30 seconds.

[0068] "result" Figure 10 shows SEM images (left) and SEM-EDX spectra (right) of the surface of untreated and laser-irradiated dentin substrates. When diaminesilver fluoride was added at a concentration of 3 mM or higher, submicron-sized particles were observed on the substrate surface after irradiation (Fig. 10, left), and fluorine and silver were detected on the same surface in addition to calcium, phosphorus, and oxygen (Fig. 10, right). It is believed that calcium phosphate containing fluorine and silver precipitated on the surface of these substrates. On the other hand, when NCP solution without diaminesilver fluoride was used, no clear precipitates were observed on the substrate surface after irradiation (Fig. 10, left). It is believed that diaminesilver fluoride has the effect of accelerating the calcium phosphate precipitation reaction by increasing the supersaturation of the NCP solution. Cross-sectional TEM analysis was performed on dentin substrates irradiated with laser light in an NCP solution containing 3 mM diamine silver fluoride. As shown in the upper left of Figure 11, columnar particles with diameters of approximately 0.1 to 0.2 μm were observed on the surface of the substrate, and the thickness of the precipitate layer consisting of these particles was just under 1 μm. The SAED pattern of the precipitate layer (region a) showed diffraction spots corresponding to the 002 and 004 apatite crystals (upper right of Figure 11), suggesting that the c-axes of the apatite crystals were oriented perpendicular to the substrate surface. Elemental mapping analysis using STEM-EDX revealed that calcium, phosphorus, and fluorine were uniformly detected in the precipitate layer (middle and bottom of Figure 11). Furthermore, silver nanoparticles with diameters of several tens of nanometers were observed in part of the precipitate layer and within the surface layer of the dentin substrate (middle right of Figure 11). Laser irradiation in the NCP solution containing diamine silver fluoride likely led to the photoreduction of silver ions in parallel with the precipitation of apatite crystals. In the cross-sectional HAADF-TEM image of the precipitated layer shown in the upper left of Figure 12, the STEM-EDX spectrum of crystalline region a (within the dashed-line frame) where silver nanoparticles (black arrows) are not clearly visible (upper right of Figure 12) also showed peaks for calcium, phosphorus, fluorine, and oxygen, as well as silver. High-resolution TEM observation of the columnar crystals in the precipitated layer confirmed the incorporation of approximately 5 nm diameter silver nanoparticles (lower left of Figure 12, white arrows) into the crystals. Extracting the periodicity of the lattice fringes from the high-resolution TEM image of this crystal using fast Fourier transform revealed spots corresponding to the 002 and 102 interplanar spacings of the apatite crystals (lower right of Figure 12), indicating that the crystals were single crystals of apatite. From the above, it was found that by using NCP solution containing diamminesilver fluoride as a supersaturated solution, a precipitate layer consisting of fluoride- and silver-containing apatite crystals can be formed on the surface of dentin substrates. It is presumed that fluoride is incorporated into the precipitate layer by substituting some of the hydroxyl groups of the apatite crystals as fluoride ions, and silver is incorporated into the precipitate layer as silver nanoparticles.

[0069] [Example 3] (Laser irradiation in supersaturated liquid for dental composite resin) A fluoride-containing apatite precipitate layer was also formed on the surface of dental composite resin.

[0070] "method" After filling the mold with uncured resin mud of an acrylic dental composite resin containing glass filler (Gracefill Zero Flow, manufactured by GC Corporation), a disk-shaped resin substrate (diameter: 4 mm, thickness: 1 mm) was produced by a photopolymerization curing reaction (irradiation time: 10 seconds) using an LED light irradiator (Pencure, manufactured by Morita Manufacturing Co., Ltd.). After forming coating film A on the surface of the resin substrate in the same manner as in Example 1, the substrate was irradiated with laser light for 3 minutes in CP liquid or CP liquid containing NaF (1 mM). The irradiation distance was set to 3 mm, and the laser output was varied from 1 W to 6 W, resulting in a power density of 0.5 W / mm on the irradiated surface. 2 to 2.8W / mm 2 It has changed up to.

[0071] "result" Figure 13 shows SEM images (left group) and SEM-EDX spectra (right group) of the untreated resin substrate surface, after coating A, and after laser irradiation. Carbon, oxygen, and silicon were detected on the untreated resin surface (Figure 13 right). After coating, the silicon peak disappeared, and peaks for sodium and sulfur, which are constituent elements of ICG, were observed. Since sodium and sulfur were not detected on the substrate surface after irradiation, it is believed that Coating A, which contains ICG, disappeared upon laser irradiation. When NaF-added CP solution was used, submicron-sized particles were observed in the SEM image of the substrate surface after irradiation (Figure 13 left group). In addition to silicon, a constituent element of resin, calcium, phosphorus, and trace amounts of fluorine were detected on the surface of the same substrate (Figure 13 right). Therefore, the particles on the substrate surface are believed to be fluorine-containing calcium phosphate. The peak intensities of calcium and phosphorus relative to the silicon peak increased with increasing laser power. This result shows that the thickness of the precipitate layer consisting of fluorine-containing calcium phosphate particles increased with increasing laser light output. On the other hand, when a CP solution without NaF was used, micron-sized scale-like precipitates were observed on the substrate surface after irradiation (Figure 13, left group), and no fluorine was detected on the same surface (Figure 13, right group). Figure 14 shows the laser light output of 6 W (2.8 W / mm 2 ) irradiation conditions, the results of TEM analysis of precipitates formed from CP solution with (left) or without (right) NaF addition are shown. In SAED analysis, diffraction spots attributed to apatite were observed in the precipitates formed from the NaF-added CP solution, while diffraction spots attributed to octacalcium phosphate (OCP) were observed in the precipitates formed from the CP solution (top row of Figure 14). Taking into account the results of STEM-EDX analysis (middle and bottom rows of Figure 14), it was concluded that the columnar particle groups formed from the NaF-added CP solution were fluorine-containing apatite crystals, and the scaly precipitates formed from the CP solution were OCP crystals. These results demonstrate that this method can form a precipitate layer consisting of fluoride-containing apatite or OCP on the surface of artificial material substrates that do not contain apatite. It is thought that the substrate surface and the supersaturated solution near the surface are locally heated by the absorption of laser light by the coating and its conversion into thermal energy, and that the resin surface is activated by laser light irradiation, thereby inducing the nucleation of calcium phosphate on the irradiated surface. After creating a defect on the surface of the dentin substrate, the above resin was filled and hardened into the defect to create a resin restoration model tooth surface. Coating A was then formed on the model tooth surface, including the adhesive interface between the resin and dentin, and laser light (irradiation distance: 3 mm, output: 6 W, power density on the irradiation surface: 2.8 W / mm ) was applied in NaF-added CP solution. 2 ) was irradiated for 3 minutes. As shown in Figure 15, a precipitated layer (arrow) thought to be fluoride-containing apatite formed on the irradiated surface, sealing the adhesive interface between the dentin and resin. Fluoride-containing apatite has been reported to exhibit higher acid resistance and antibacterial properties than apatite. By sealing the adhesive interface between the resin and tooth structure with a fluoride-containing apatite layer, it may be possible to prevent secondary caries (which occurs when bacteria penetrate the interface between the resin and tooth structure) after resin restoration.

[0072] [Example 4] (Laser irradiation of anodized titanium in supersaturated solution) A fluorine-containing apatite precipitate layer was also formed on the surface of anodized titanium with a micro-scale uneven structure.

[0073] "method" A disk-shaped titanium metal substrate (diameter: 8 mm, thickness: 1-1.5 mm) was anodized using a 0.15 M aqueous solution of calcium acetate and a 0.1 M aqueous solution of calcium glycerophosphate at a voltage of 300 V and a current of 15 A. Coating film A was formed on the surface of the resulting anodized titanium substrate in the same manner as in Example 1, and then the substrate was irradiated with laser light for 30 or 60 seconds in a NaF-added CP solution. The irradiation distance was varied from 3 mm to 10 mm and the laser light output from 3 W to 9 W, resulting in a power density of 0.5 W / mm2 on the irradiated surface. 2 to 4.2 W / mm 2 It has changed up to.

[0074] "result" SEM-EDX analysis revealed that the surface of the titanium substrate after anodizing had a microscale uneven structure (Figure 16, left group) and contained calcium and phosphorus (Figure 16, right group). Laser light (irradiation distance: 5 mm, output: 9 W, power density on the irradiated surface: 1.8 W / mm 2 After 30 seconds of irradiation, new particulate precipitates were observed on the substrate surface (Figure 16, left group), and fluorine was detected (Figure 16, right group). The size and amount of these particulate precipitates further increased after 60 seconds of irradiation. The irradiation time was fixed at 30 seconds, and the laser light output was kept constant at 9 W while the irradiation distance was varied. As a result of SEM-EDX analysis, the irradiation distance was 10 mm (power density on the irradiation surface: 0.5 W / mm 2 ), no deposits were found on the substrate surface and no fluorine was detected, whereas at an irradiation distance of 5 mm or less (power density of the irradiation surface 1.8 W / mm 2 Under the above conditions, the formation of fluorine-containing precipitates was observed on the surface of the substrate (Fig. 17). Next, when the laser light output was changed while keeping the irradiation distance constant at 3 mm, the amount of particulate precipitates formed on the substrate surface increased with increasing output (Fig. 18, left group). The substrate on which the most particulate precipitates were observed (irradiation distance: 3 mm, output: 9 W, power density on the irradiation surface: 4.2 W / mm 2 ), cross-sectional TEM analysis revealed that columnar particles with a diameter of approximately 0.1 μm were precipitated on the substrate surface (Figure 19, top left). In the SAED pattern of the precipitate layer (area a) consisting of these columnar particles, a diffraction spot corresponding to 100 of apatite crystals was observed (Figure 19, top right). Elemental mapping analysis using STEM-EDX revealed that calcium, phosphorus, and fluorine were uniformly detected in the precipitate layer (Figure 19, middle and bottom). These results demonstrate that the columnar particles precipitated on the substrate surface are fluorine-containing apatite crystals.

[0075] [Example 5] (Calcium phosphate pre-coating on substrate) The effect of calcium phosphate pre-coating on the substrate was confirmed.

[0076] "method" The surface of a flat ethylene-vinyl alcohol copolymer substrate (size: 10 mm square, thickness: 1 mm, ethylene content: 32 mol%) was polished with SiC polishing paper (#2000) and then washed to prepare a substrate. The substrate was immersed in a 0.2 M CaCl2 aqueous solution for 10 seconds, then immersed in ultrapure water for 1 second and dried, then immersed in a 0.2 M K2HPO4·3H2O aqueous solution for 10 seconds, then immersed in ultrapure water for 1 second and dried. This alternating immersion procedure was repeated three times to pre-coat the substrate surface with calcium phosphate. Coating film A was then formed on the surface of the substrate thus pre-coated with calcium phosphate and on the untreated substrate (without calcium phosphate pre-coating) in the same manner as in Example 1, and the substrate was then irradiated with a laser beam (irradiation distance: 3 mm, output: 3 W, power density on the irradiation surface: 1.4 W / mm) in a NaF-added CP solution. 2 ) was irradiated for 10 seconds.

[0077] "result" SEM-EDX analysis revealed columnar particles on the substrate surface after laser irradiation (Figure 20, left group). Calcium, phosphorus, and fluorine were detected on the substrate surface in addition to the substrate's constituent elements (Figure 20, right). This confirmed that the columnar particles were fluorine-containing calcium phosphate precipitated on the substrate surface. While the precipitates were sparsely scattered on the substrate surface without a calcium phosphate precoat, the calcium phosphate precoated substrate surface exhibited a high density of columnar precipitates elongated perpendicular to the substrate. The calcium phosphate precoated on the substrate surface likely provided sufficient nucleation sites, allowing for rapid oriented precipitation of crystals through geometric sorting. These findings demonstrate that applying a calcium phosphate precoat to the substrate surface can accelerate the calcium phosphate precipitation reaction in the second step.

[0078] [Example 6] (Changes in ICG-containing viscous paint: (1) Addition of calcium) The effect of adding calcium to paint was confirmed.

[0079] "method" A calcium-added paint (paint A-Ca) was prepared in the same manner as in Example 1, except that the glycerin dilution liquid used in preparing the 7 mass% glycerin aqueous solution, which was the ICG mixing liquid in Example 1, was changed from ultrapure water to a 0.2 M CaCl2 aqueous solution. A non-dried coating film consisting of the paint A-Ca or the calcium-free paint A was formed on the resin substrate used in Example 3 in the same manner as in Example 3. These substrates were immersed in 10 mL of the NCP solution containing diamine silver fluoride (3 mM) used in Example 2, and a laser beam (irradiation distance: 3 mm, output: 3 W, power density on the irradiation surface: 1.4 W / mm) was applied to the surface of the substrate. 2 ) was irradiated for 3 minutes.

[0080] "result" SEM-EDX analysis revealed precipitation on the substrate surface after laser irradiation (Figure 21, left group). In addition to the resin component elements, calcium, phosphorus, fluorine, and silver were detected on the substrate surface (Figure 21, right), confirming that the precipitates were fluorine- and silver-containing calcium phosphate. The calcium and phosphorus peak intensities relative to the silicon peak were higher when Paint A-Ca was used. Furthermore, the density and surface coverage of the precipitates on the substrate surface were also higher when Paint A-Ca was used. It is believed that calcium ions added to the paint precipitated as calcium salts upon laser irradiation, providing nucleation sites, or were released into the solution, increasing the supersaturation of the solution near the substrate surface, thereby increasing the frequency of calcium phosphate nucleation on the substrate surface. These findings demonstrate that adding calcium to the paint can accelerate the calcium phosphate precipitation reaction in the second step.

[0081] [Example 7] (Changes in ICG-containing viscous paint: (2) Changes in the glycerin concentration of the ICG mixing liquid) The optimum range of glycerin concentration for the ICG mixing liquid was confirmed.

[0082] "method" ICG-containing viscous paints were prepared in the same manner as in Example 1, except that the concentration of the glycerin aqueous solution used as the ICG-mixing liquid was changed from 0% by mass to 100% by mass, and their properties were evaluated. After forming a coating film of the ICG-containing viscous paint on the surface of the dentin substrate in the same manner as in Example 1, the coating film was irradiated with laser light (irradiation distance: 3 mm, output: 3 W, power density on the irradiated surface: 1.4 W / mm ) in the NaF-added CP solution. 2 According to Non-Patent Document 3 (Segur, J.B., and Oberstar, H., Ind. Eng. Chem., 43:2117-2120, 1951), the viscosities at 20°C of glycerin aqueous solutions with glycerin concentrations of 0 mass%, 1 mass%, 3 mass%, 7 mass%, 10 mass%, 15 mass%, 40 mass%, and 100 mass% are calculated to be 1 mPa·s, 1.03 mPa·s, 1.09 mPa·s, 1.21 mPa·s, 1.49 mPa·s, 3.72 mPa·s, and 1410 mPa·s, respectively.

[0083] "result" (Properties of ICG-containing viscous paint) Table 1 shows the ease of mixing ICG powder (25 mg) with each ICG mixing liquid (0.2 mL of glycerin aqueous solution of various concentrations), the applicability (working time), shape retention, and in-liquid stability of the ICG-containing viscous coating obtained after mixing (1.5 minutes). In Table 1, the ease of mixing was evaluated as "Good" if there was no powdery abrasion after 30 seconds of mixing, and "Poor" if there was powdery abrasion after 30 seconds of mixing. The working time of the coating was evaluated as "Poor" if the time required for fluidity suitable for application was less than 7 minutes, and as "Good" if the time required for fluidity suitable for application was 7 minutes or more. The coating film retention was evaluated as "Good" if there was no dripping from the coating film (10 μL, thickness 0.05 mm or more) even on a vertical glass surface, and as "Poor" if there was dripping from the coating film (10 μL, thickness 0.05 mm or more) on a vertical glass surface. Regarding the in-liquid stability of the coating film, cases where there was almost no ICG diffusion into the NaF-added CP liquid were marked as "○", and cases where there was ICG diffusion into the NaF-added CP liquid were marked as "×".

[0084] [Table 1]

[0085] Figure 22 shows the evaluation results of the shape retention and in-liquid stability of representative paints. Aqueous solutions with glycerin concentrations of 1% by mass or less had poor wettability with ICG powder, making it difficult to uniformly mix the ICG (even after 30 seconds of mixing, powder remained and clumps easily formed). The resulting paint exhibited fluidity suitable for application to substrates immediately after preparation (mixing), but after about 5 minutes, fluidity decreased, and after 7 minutes, uniform application to the substrate became difficult. This is likely due to water evaporation from the paint. On the other hand, when the glycerin concentration was increased to 3% by mass or higher, wettability with the ICG powder improved, making it easier to mix the ICG powder (no powder remained after 30 seconds of mixing). It is believed that glycerin, which has both hydrophilic and hydrophobic groups, improved the mixability and dispersibility of the ICG powder. Furthermore, the resulting paint retained the same fluidity as immediately after preparation even after 7 minutes, allowing for uniform application to the substrate. It is presumed that the glycerin inhibited water evaporation from the paint and the structural development of the paint (irreversible ICG aggregation and network formation), thereby extending the usable time. However, when the glycerin concentration was increased to 15% by mass or more, the paint's stability in the liquid decreased (ICG diffusion into the NaF-added CP liquid became significant), and when it was increased to 40% by mass or more, even the shape retention decreased (10 μL of paint dripped on a vertical glass surface). The viscoelasticity of each paint was measured in the same manner as in Example 1. -1 ) and high shear rate (100 s -1The left side of Figure 23 shows a graph plotting the viscosity (average and standard deviation of measurements from the second to fourth cycles) at 15% by mass or less against the concentration of the glycerin aqueous solution used for mixing with ICG. When the glycerin concentration was 15% by mass or less, the viscosity of the resulting paint was higher at low shear rates than at high shear rates, confirming its pseudoplastic fluid properties. It was also confirmed that these paints exhibited a relatively high storage modulus at low shear strains (0.01) (right side of Figure 23, average and standard deviation of measurements from the first to second cycles). On the other hand, paints prepared using glycerin aqueous solutions with concentrations of 40% by mass or more became Newtonian liquids with a constant low viscosity (approximately 67 mPa·s) regardless of shear rate. The storage modulus of the paint at low shear strains (0.01) decreased to approximately 4 Pa. These results explain the paint's poor shape retention and in-liquid stability. As described above, it was found that glycerin added to the ICG mixing liquid improves the mixability of the ICG powder and extends the usable life of the resulting paint. In order for glycerin to exert the above effects and for the resulting paint to exhibit both fluidity suitable for application to substrates and shape retention that enables the formation of thick films on vertical surfaces, it was thought that a glycerin concentration of 3% to 15% by mass in the ICG mixing liquid would be sufficient. SEM-EDX analysis revealed that when a glycerin solution containing 10% or less by mass was used as the ICG mixing liquid, submicron-sized precipitates believed to be fluorine-containing apatite were formed on the substrate surface after irradiation (Figure 24, left group). The largest precipitates were observed when a 7% by mass glycerin solution was used. When the glycerin concentration of the ICG mixing liquid was increased to 15% by mass or more, the precipitates on the substrate surface became smaller, suggesting that the calcium phosphate precipitation reaction was suppressed. This is thought to be due to a decrease in the amount of ICG on the substrate surface (diffusion into the liquid) due to a decrease in in-liquid stability. Taking into account the in-liquid stability of the paint, the optimal glycerin concentration range in the ICG mixing liquid was thought to be greater than 1% by mass and less than 15% by mass.

[0086] [Example 8] (Changes in ICG-containing viscous paint: (3) Changes in additives added to the ICG mixing liquid) The effectiveness of substances other than glycerin as additives to the ICG mixing liquid was examined.

[0087] "method" ICG-containing viscous coatings were prepared and their properties evaluated in the same manner as in Example 1, except that the ICG-mixing liquid was changed to a 0.1% or 0.3% by mass aqueous solution of carboxymethylcellulose (CMC) or a 1% or 10% by mass aqueous solution of polyethylene glycol (PEG). The CMC and PEG aqueous solutions were prepared by dissolving sodium CMC (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., weight-average molecular weight: 100,000-110,000) or molecular biology-grade polyethylene glycol (manufactured by SERVA Electrophoresis, average molecular weight: 5,400-6,600) in ultrapure water. After forming a coating film consisting of each coating on the surface of a dentin substrate in the same manner as in Example 1, the substrate was immersed in a NaF-added CP solution, and a laser beam (irradiation distance: 3 mm, output: 3 W, power density on the irradiation surface: 1.4 W / mm) was applied to the surface. 2 ) was irradiated for 30 seconds.

[0088] "result" The properties of the paints obtained using each ICG mixing liquid and the same liquid are shown in Table 2. For comparison, the results when water (without additives) was used as the ICG mixing liquid are also shown in the top row of Table 2 (data from Table 1 is reproduced). The symbols in Table 2 are the same as those in Table 1.

[0089] [Table 2]

[0090] Like glycerin (Table 1), both CMC and PEG, when added to the ICG mixing liquid at appropriate concentrations, were found to improve the mixability of the ICG powder and extend the usable life of the resulting paint. However, increasing the concentration of the PEG aqueous solution from 1% to 10% by mass reduced the shape retention of the resulting paint and the stability of the coating film in the liquid. SEM-EDX analysis revealed the formation of submicron-sized precipitates, likely fluorine-containing apatite, on the substrate surface after irradiation with both ICG-containing viscous paints (Figures 25 and 26). However, these precipitates were smaller than those observed with Paint A (Figure 24, left group), suggesting the suppression of calcium phosphate precipitation. The use of CMC and PEG as additives with higher molecular weights than the additive (glycerin) in Paint A may have consumed more laser energy to remove the coating, potentially reducing the effectiveness of solution heating. This hypothesis is supported by the fact that the precipitates became even smaller with increasing CMC concentration (Figure 25, left). (For PEG, the decrease in in-solution stability due to increasing additive concentration, as shown in Table 2, also contributed.) Furthermore, the carbon peak intensity in the SEM-EDX spectrum of the irradiated surface (Figure 25, right) was higher when a higher concentration of 0.3% CMC aqueous solution was used. This result suggests the presence of CMC remaining on the irradiated surface. It was found that the type of additive and its concentration must be appropriately selected not only in terms of the properties and operability of the paint, but also in terms of the ease of removal by laser irradiation in a supersaturated solution and the acceleration effect of the calcium phosphate precipitation reaction.

[0091] [Example 9] (Changes in ICG-containing viscous paint: (4) Changes in ICG concentration in ICG-containing viscous paint) "method" An ICG-containing viscous paint was prepared in the same manner as in Example 1, except that the ICG mixing liquid added to 25 mg of ICG powder was changed to water (without additives) and the amount was changed from 0.10 mL (equivalent to the amount of conventional paint) to 0.50 mL, and its properties were evaluated.

[0092] "result" The ICG mass concentration and properties of each paint are shown in Table 3. In Table 3, the ease of mixing was evaluated as "Good" if there was no powdery air after 30 seconds of mixing, and "Poor" if there was powdery air after 30 seconds of mixing. Regarding the usable life of the paint, "Poor" was evaluated if the time it took to show fluidity suitable for application was less than 7 minutes, and "Good" was evaluated if the time it took to show fluidity suitable for application was 7 minutes or more. Regarding film retention, "Good" was evaluated if there was no dripping from the film (10 μL, thickness 0.05 mm or more) even on a vertical glass surface, and "Poor" was evaluated if there was dripping from the film (10 μL, thickness 0.05 mm or more) on a vertical glass surface. Regarding the in-liquid stability of the paint film, "Good" was evaluated if there was almost no diffusion of ICG into the NaF-added CP solution, and "Poor" was evaluated if there was diffusion of ICG into the NaF-added CP solution. Unassessed status was evaluated as "-."

[0093] [Table 3]

[0094] The properties of the conventional paint (ICG concentration: 4.8% by mass) are as described in Example 1. When the ICG mass concentration of the paint was increased to 9.1% by mass, the paint exhibited shape retention due to increased viscoelasticity, and when it was further increased to 11.1% by mass, improved stability in liquid was also observed. However, at 11.1% by mass, the amount of water (0.20 mL) relative to the amount of powder was small, making it difficult to uniformly mix the ICG powder and shortening the usable life of the paint. When the ICG mass concentration of the paint was increased to 14.3% by mass or higher, the fluidity was insufficient even immediately after preparation, making it difficult to apply to the substrate and adjust the film thickness. From the above, it was found that by changing the powder-to-liquid ratio (ICG mass concentration) of conventional paint, it is possible to prepare a paint that exhibits both shape retention and stability in liquid. However, without additives such as glycerin, it was not possible to obtain a paint that combines the above two properties with the ease of mixing ICG powder and a sufficient pot life (7 minutes or more).

Claims

1. A step of applying a light-absorbing agent-containing viscous coating material containing a liquid and a light-absorbing agent to a surface of a substrate to form a coating film made of the light-absorbing agent-containing viscous coating material on the surface of the substrate; and irradiating the surface of the coating film with a laser beam while the surface is in contact with a supersaturated solution of calcium phosphate, thereby precipitating calcium phosphate on the surface of the substrate.

2. 2. The method for forming calcium phosphate according to claim 1, wherein the light absorbent-containing viscous paint is obtained by mixing the light absorbent with water or a liquid containing an additive.

3. 3. The method for forming calcium phosphate according to claim 2, wherein the additive is a polyhydric alcohol or a polysaccharide.

4. 2. The method of claim 1, wherein the light absorber is indocyanine green.

5. 2. The method for forming calcium phosphate according to claim 1, wherein the calcium phosphate precipitated on the substrate is composed primarily of any one of hydroxyapatite, octacalcium phosphate, fluorine-containing hydroxyapatite, silver-containing hydroxyapatite, and fluorine- and silver-containing hydroxyapatite.

6. 2. The method for forming calcium phosphate according to claim 1, wherein the substrate is a tooth, titanium metal, dental composite resin, or polyether ether ketone.

7. a vial or syringe containing a light absorbing agent; a vial or syringe containing a liquid for mixing with the light absorber; A calcium phosphate forming kit comprising: two or more vials or syringes containing a raw material liquid for a supersaturated calcium phosphate solution.

8. A laser used in the method for forming calcium phosphate according to claim 1.

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