Method for repairing subfissure tooth sample and device for repairing subfissure teeth in oral cavity

Abstract

The invention belongs to the field of new medical materials, and discloses a method for repairing a subfissure tooth sample and a device for repairing subfissure teeth in an oral cavity, the method comprises the following steps: placing the subfissure tooth sample in an ALD reaction chamber, and vacuumizing; introducing a gaseous titanium precursor titanium tetraisopropylate, carrying out single-layer reaction on the subfissure tooth sample to form a Ti-O bond, and completing a first deposition half cycle; introducing inert gas to purge the reaction chamber; introducing an oxygen source to form a TiO2 film, and completing a second deposition half cycle; repeating the first deposition half cycle and the second deposition half cycle for multiple times until the TiO2 film grows on the subfissure tooth sample; and soaking the subfissure tooth sample subjected to ALD treatment in artificial saliva, and inducing remineralization by using a TiO2 film to form a mineralizer. According to the device and the method disclosed by the invention, the precise repair of the subfissure tooth or the in-vitro subfissure tooth sample can be realized, and the occurrence risk of pulpitis, apicitis and other bacterial infectious diseases in the oral cavity can also be reduced.

Description

Technical Field

[0001] This invention relates to the field of new medical materials technology, specifically to a method for repairing cracked tooth samples and a device for repairing cracked teeth in the oral cavity. Background Technology

[0002] Cracked teeth are a progressive damage condition affecting the hard tissues of the tooth, with a prevalence of approximately 10%; the European consensus among endodontic experts indicates that cracks in the crown area account for as much as 70%. Research reports show that the incidence of cracked teeth in untreated teeth has been increasing over the past two decades, and this increase is associated with age, being most common in individuals over 40. Patients with cracked teeth often seek treatment due to pain in the affected tooth, with the most common symptoms being pain upon biting and pain in response to hot or cold stimuli. In the early stages of cracked teeth, these symptoms can only be addressed through occlusal adjustment, banding, or resin impregnation to seal the crack and slow its further expansion. If early intervention is ineffective, the tooth will gradually develop spontaneous pain, requiring root canal treatment to kill the pulp nerve to alleviate the pain, and may even lead to the tooth's loss. The aforementioned early intervention methods are mainly based on two aspects: biology and mechanics. This involves sealing the pathways of bacterial contamination and toxic elements, stabilizing the fractured portion of the tooth, and preventing stress that could cause pain and further crack expansion. However, epidemiological surveys show that even after early treatment, some patients with tooth cracks in the Asian population still develop pulp necrosis and require root canal treatment.

[0003] There are two main methods for restoring cracked teeth. One method involves grinding away the crack and then directly bonding it with composite resin. The procedure is as follows: the clinician first uses microscopic instruments to precisely locate the crack's direction, then uses a high-speed turbine with a fine bur to thoroughly remove the crack tissue. Subsequently, an inlay or full crown is chosen based on the extent of the defect. During bonding, a highly fluid composite resin material is used, leveraging its excellent marginal fit to form a stable chemical bond with the tooth structure. However, multiple clinical follow-up studies have shown that this method has significant limitations. A 5-year follow-up study involving 300 patients showed that approximately 65% ​​of direct restoration cases developed pulpitis symptoms within 2-3 years post-surgery, requiring further root canal treatment. The second method is crown restoration, which is currently the mainstream recommended approach for protecting cracked teeth. Its core treatment mechanism lies in the structural design of the restoration, effectively reducing the lateral forces generated during chewing, thereby inhibiting further crack propagation. On the one hand, full crowns can form a tight coronal seal, acting like a strong barrier for the affected tooth, blocking bacteria from entering the pulp tissue through the crack at the source. On the other hand, the circumferential design creates a clamping effect, which can evenly distribute occlusal forces to the root, making stress distribution more reasonable and effectively preventing stress concentration from deepening the crack. In clinical practice, overcusp restorations are widely used in the treatment of tooth cracks, with significant results. In addition to full crowns, the literature also records onlays, veneers, and other full-coverage restorations, each with its own characteristics in terms of aesthetic restoration and functional recovery. However, it cannot be ignored that all of the above restoration techniques require extensive preparation and grinding of tooth structure. Studies have shown that about 70% of patients are resistant to these treatment options due to concerns about tooth damage, which is also an important factor limiting their widespread clinical application.

[0004] Patients with cracked teeth often seek medical attention due to pain symptoms, with hot and cold stimuli being the most common cause. Normal teeth possess a certain degree of heat resistance, tolerating temperatures from 70°C to 0°C. However, a study applying heat load to the occlusal surface of molars found that during extreme heat stimulation, the highest tooth temperature reached 53.1°C, and the lowest was 1°C. Normal teeth showed no pain or discomfort in the dental pulp nerve within this temperature range, while cracked teeth exhibited pain symptoms. Although the mechanisms of pain transmission and sensitivity in teeth remain speculative, fluid dynamics are the most widely accepted theory. Based on this theory, some scholars believe that the mechanism of hot and cold stimuli pain in cracked teeth is as follows: dentinal tubular fluid accumulates in the crack; when stimulated by external temperature, the dentinal tubular fluid in the crack fluctuates, generating pressure changes that accelerate the movement rate of the fluid within the dentinal tubules, thereby stimulating pain fibers and triggering pain.

[0005] Existing research on thermal insulation mainly focuses on full crown restorations and dentin sealants, incidentally mentioning that temperature changes may cause thermal stress inside the tooth. Mengke Wang et al. pointed out that veneer restorations can, to some extent, insulate against hot and cold stimuli, thus alleviating the pain symptoms caused by hot and cold stimuli in cracked teeth. However, another study showed that among 17 patients who underwent full crown restorations, 20-30% experienced postoperative temperature sensitivity symptoms that persisted for a long time.

[0006] To address the aforementioned issues, the field requires a new device and method for repairing cracked teeth intraorally. Prior to this, a method for repairing cracked tooth samples in vitro needs to be developed to verify the feasibility of the method. Only in this way can the crack be sealed in its early stages to prevent further expansion and thus preserve the pulp. Summary of the Invention

[0007] To address the aforementioned problems, this invention proposes a method for repairing cracked teeth by first inducing the formation of minerals through atomic layer deposition of titanium dioxide thin films, and then using saliva or artificial saliva to remineralize the cracks, thereby filling the gaps in the cracked teeth, isolating them from hot and cold stimuli, and relieving the pain symptoms caused by hot and cold stimuli in patients with cracked teeth.

[0008] Therefore, the present invention first provides a method for repairing a cracked tooth sample, wherein the method is an in vitro method for repairing a cracked tooth sample, the cracked tooth sample being obtained by pretreatment of an extracted tooth; the method includes the following steps:

[0009] Step S1: Deposit a TiO2 thin film on the cracked tooth sample using atomic layer deposition (ALD) technology; specifically including:

[0010] Step S1.1: Place the cracked tooth sample in the ALD reaction chamber and evacuate the reaction chamber;

[0011] Step S1.2: Introduce gaseous titanium precursor into the reaction chamber. The titanium precursor is titanium tetraisopropoxide. The titanium precursor undergoes a monolayer reaction at the hydroxyl sites on the inner wall of the dentinal tubules of the cracked tooth sample to form Ti-O bonds, completing the first half-cycle of deposition. Then, inert gas is introduced to purge the reaction chamber to remove unreacted titanium precursor.

[0012] Step S1.3: Introduce an oxygen source into the reaction chamber. The oxygen source is water vapor or O3. The oxygen source reacts with the titanium precursor adsorbed on the inner wall of the dentinal tubules to form a TiO2 monolayer film. This is the second half-cycle of deposition. Then, an inert gas is introduced to purge the reaction chamber to remove unreacted oxygen source and byproducts.

[0013] Step S1.4: Repeat steps S1.2 and S1.3 multiple times until a uniform and dense TiO2 film grows layer by layer on the inner wall of the crack in the tooth sample.

[0014] Step S2: Soak the ALD-treated cracked tooth sample in saliva or artificial saliva for 2 to 30 days to finally obtain the remineralized cracked tooth.

[0015] In this invention, the oxygen source is water vapor or O3. Compared with water vapor, ozone has stronger oxidizing properties, which can accelerate the formation of TiO2 and shorten the entire deposition cycle. However, ozone is unstable, needs to be prepared on-site, and has extremely high requirements for the sealing of the equipment. Therefore, water vapor is preferred as the oxygen source.

[0016] In one specific embodiment, before step S1, the pretreatment step of the extracted tooth includes: first placing the collected extracted tooth in liquid nitrogen for 25-35 seconds, and then placing it in hot water at 95-100°C for 25-40 seconds to obtain the cracked tooth sample.

[0017] In one specific embodiment, in step S1, the atomic layer deposition temperature in the ALD reaction chamber is 90-180°C; the temperature of the titanium precursor is greater than 80°C before it is introduced into the reaction chamber.

[0018] In one specific embodiment, in step S1.2, the inert gas is nitrogen, the pulse time of the titanium precursor is 0.8~1.5 seconds, and it is held for 6~10 seconds after the pulse ends; then the nitrogen purging program is started and lasts for t1 seconds, t1=25~35, to remove the unadsorbed titanium precursor vapor remaining in the reaction chamber.

[0019] In one specific embodiment, in step S1.3, the inert gas is nitrogen, the pulse time of the oxygen source is 0.08~0.2 seconds, and it is held for 5~10 seconds after the pulse; then the nitrogen purging program is started and lasts for t2 seconds, t2=32~40, and t2>t1, so as to remove the residual oxygen source and by-products in the reaction chamber.

[0020] In one specific implementation, step S1.4 involves repeating steps S1.2 and S1.3 a total of 2 to 10 times.

[0021] This invention also provides a device for repairing cracked teeth in the oral cavity, comprising a reaction chamber for insertion into the cracked tooth in the oral cavity, a sealing ring around the periphery of the reaction chamber, a heater inside the reaction chamber, an air inlet pipe and an exhaust pipe connected to the reaction chamber, and multiple raw material containers connected in parallel at the other end of the air inlet pipe, including a titanium precursor container, an oxygen source container, and an inert gas container, wherein the titanium precursor container contains titanium tetraisopropoxide, the oxygen source container contains water, and an evaporator is provided on both the titanium precursor container and the oxygen source container, and a high-speed solenoid valve is provided at the outlet of each raw material container; the other end of the exhaust pipe is connected to an exhaust valve, a vacuum gauge, a vacuum pump, and an exhaust gas treatment container; the device also includes a temperature controller and a controller, the temperature controller being electrically connected to the heater and the evaporator, and the controller being electrically connected to the temperature controller, the high-speed solenoid valve, and the exhaust valve.

[0022] In one specific embodiment, the reaction chamber is further provided with a baffle for separating the airflow at the inlet pipe and the outlet pipe, and the heater is disposed on the baffle.

[0023] In one specific embodiment, the shape of the reaction chamber is matched to the shape of a molar in the oral cavity, and space is left in the reaction chamber for air intake and exhaust.

[0024] In one specific embodiment, the reaction chamber is shaped like a saddle or a saddle pad.

[0025] The method for in vitro repair of cracked tooth samples described in this invention can be used to guide clinical treatment. This invention verifies the feasibility of intraoral repair of cracked teeth by repairing cracked tooth samples in vitro.

[0026] In this invention, the ALD described in step S1 has already achieved a certain repair effect on the cracked tooth sample; however, further treatment with saliva or artificial saliva after ALD to promote remineralization of the cracked tooth sample after ALD can achieve a better repair effect.

[0027] After treatment with the device described in this invention, the saliva in the patient's mouth can mineralize the cracked tooth after ALD; in addition, the patient can also rinse their mouth with artificial saliva to promote the remineralization of the cracked tooth after ALD and improve the restoration effect.

[0028] Furthermore, plasma-assisted ALD can be introduced into the device described in this invention. Applying plasma during the reaction process can significantly improve the activity of the precursor, accelerate the reaction rate, and obtain high-quality TiO2 films in a shorter time. However, the device requires an additional plasma analyzer, which increases the cost and complexity of the operation.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. This invention utilizes atomic layer deposition (ALD) technology to deposit titanium dioxide to seal the dentinal tubules of cracked teeth. The thickness of the deposited TiO2 film is typically between a few nanometers and tens of nanometers, precisely covering the exposed dentinal tubules on the crack walls and inducing the formation of new minerals for effective sealing. This sealing effect significantly reduces dentin permeability, preventing external stimuli (such as cold, heat, acid, and sweetness) from being conducted to the pulp through the dentinal tubules, thereby alleviating dentin hypersensitivity symptoms. Simultaneously, the TiO2 film can also, to a certain extent, resist the invasion of bacteria and their metabolites into the dentinal tubules, reducing the occurrence of bacterial infections such as pulpitis and apical periodontitis.

[0031] 2. In the method described in this invention, the TiO2 surface contains a large number of hydroxyl (-OH) groups. These hydroxyl groups can complex with calcium ions in aqueous solution, causing calcium ions to accumulate on the TiO2 surface. When phosphate ions are present in the environment, the accumulated calcium ions combine with phosphate ions, gradually forming calcium phosphate salts through a series of chemical reactions and crystal growth processes. This induced calcium phosphate layer has significant implications: firstly, it can be used to repair dentin defects, as the newly formed hydroxyapatite is tightly integrated with the original dentin structure, enhancing the mechanical properties of the tooth tissue; secondly, it can form a protective layer on the dentin surface, further sealing the dentinal tubules.

[0032] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0033] The accompanying drawings are provided to further illustrate embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings:

[0034] Figure 1 This is a scanning electron microscope (SEM) image of the fracture surface of a tooth with a hidden crack.

[0035] Figure 2 This is a scanning electron microscope image of the fracture surface of a tooth sample with a hidden crack after ALD in this invention.

[0036] Figure 3 This is a scanning electron microscope image of a cracked tooth sample after it has been soaked in ALD and artificial saliva in this invention.

[0037] Figure 4 This is an EDS energy spectrum result of a tooth sample with a hidden crack after being processed by the method described in this invention.

[0038] Figure 5 The images show the IR images of a cracked tooth sample before and after processing by the method described in this invention.

[0039] Figure 6 This is a schematic diagram of a heat insulation effect evaluation device.

[0040] Figure 7 The images show the thermal insulation effect of a cracked tooth sample before and after treatment using the method described in this invention.

[0041] Figure 8 This is a schematic diagram of a device used to repair cracked teeth in the oral cavity. Detailed Implementation

[0042] The present invention will now be described in detail with reference to the embodiments shown in the accompanying drawings. However, it should be noted that these embodiments are not intended to limit the present invention. Equivalent transformations or substitutions in function, method, or structure made by those skilled in the art based on these embodiments are all within the scope of protection of the present invention.

[0043] The titanium source used in this invention is titanium tetraisopropoxide, also known as tetraisopropyl titanate, isopropoxy titanium, or tetraisopropoxy titanium. It is an organic compound with the chemical formula C. 12 H 28 O4Ti has a relative molecular mass of 284.22. Under normal conditions, it is a colorless to pale yellow, transparent, homogeneous liquid with no odor. It will fume in moist air and is soluble in organic solvents such as anhydrous ethanol, ether, benzene, and chloroform.

[0044] The titanium source in this invention is neither tetrakis(dimethylamino)titanium nor titanium tetrachloride. The main reason is that tetrakis(dimethylamino)titanium can react with H₂O or O₂ to produce TiO₂ and dimethylamine ((CH₃)₂NH), but the amino ligand therein readily reacts with OH⁻. - The reaction with O produces dimethylamine, a highly volatile byproduct with an irritating odor and toxicity, requiring strict ventilation and protection; therefore, it is unsuitable for use in the oral cavity to repair cracked teeth. Titanium tetrachloride (TiCl4) reacts with oxidants such as water to produce TiO2, with HCl as a byproduct. HCl is highly volatile and easily desorbed; however, the byproduct HCl has a severe corrosive effect on metal components such as reaction chambers and pipes. Therefore, devices for repairing cracked teeth must use corrosion-resistant materials such as quartz, thus increasing equipment cost and complexity.

[0045] The titanium source in this invention is titanium tetraisopropoxide. Titanium tetraisopropoxide reacts with H2O to generate TiO2 and isopropanol. Its byproduct, isopropanol, is an organic alcohol and contains no acidic substances. It has good compatibility with equipment and does not require special anti-corrosion design. Furthermore, the film has high purity and no risk of residue.

[0046] The present invention provides a method for repairing a cracked tooth sample, which specifically includes the following steps.

[0047] 1. ALD Deposition of TiO2: First, the pretreated microcracked tooth sample is placed in the ALD reaction chamber, which is evacuated to a low vacuum state to create a stable environment for the reaction. Then, gaseous titanium precursor is introduced into the reaction chamber. Its molecules undergo a monolayer reaction at the hydroxyl (-OH) sites on the inner wall of the dentinal tubules through physical or chemical adsorption, forming Ti-O bonds, completing the first half-cycle of deposition. Next, an inert gas (such as nitrogen) is introduced to purge the reaction chamber, removing unreacted precursors and possible byproducts. Then, an oxygen source (such as water vapor H2O) is introduced to react with the adsorbed titanium precursor, forming a TiO2 monolayer film, which is the second half-cycle of deposition. By repeating these two half-cycles multiple times, a uniform and dense TiO2 film can be grown layer by layer on the inner wall of the tooth microcrack.

[0048] 2. Artificial saliva soaking: The cracked tooth samples after ALD treatment are soaked in artificial saliva (37℃). The longer the soaking time in the prepared artificial saliva, the more minerals are generated, and the better the restoration effect of the cracked tooth samples.

[0049] Example 1

[0050] The specific operations in this invention are as follows:

[0051] First, a liquid nitrogen freezing method was used to prepare cracked tooth samples. The collected extracted teeth were immersed in liquid nitrogen for 30 seconds, followed by immersion in 100°C hot water for 30 seconds to obtain cracked tooth samples. The scanning electron microscopy results of the fracture surface of the cracked tooth samples are shown below. Figure 1 As shown in the figure, the dentinal tubules are exposed.

[0052] The cracked tooth sample is then carefully placed into the reaction chamber of the ALD reactor, ensuring that the sample is in a stable position and that the cracked area is fully exposed to the reaction space.

[0053] The core reaction for depositing TiO2 depends on titanium tetraisopropoxide (C 12 H 28 O4Ti) and water were used as precursors, and the two reacted chemically on the surface and within the crack of the tooth sample by alternating pulses, with a deposition temperature of 150℃.

[0054] Before being introduced into the ALD reactor, the tetraisopropoxide titanium precursor is heated to 80°C to achieve a vapor pressure sufficient to support the reaction. The carrier gas used in the reaction consists of high-purity nitrogen.

[0055] Tetraisopropoxide titanium pulse: The pulse duration is 1 second. During this period, the carrier gas carries tetraisopropoxide titanium vapor rapidly into the reaction chamber, ensuring full contact with the tooth surface and cracks. After the pulse ends, there is an 8-second hold time to allow tetraisopropoxide titanium molecules to achieve saturation adsorption on the tooth surface (especially inside cracks). Subsequently, a nitrogen purging procedure is initiated and lasts for 30 seconds to thoroughly remove any remaining unadsorbed tetraisopropoxide titanium vapor from the reaction chamber, preventing gas-phase reaction with subsequently introduced H2O. This reaction step constitutes half a cycle.

[0056] H2O Pulse: The pulse duration is only 0.1 seconds. This short pulse duration avoids the formation of a liquid water film on the tooth surface due to excessive H2O, preventing interference with precise deposition within the cracks. An 8-second pause is maintained after the pulse to ensure sufficient surface reaction between the H2O molecules and the tetraisopropoxide titanium adsorbed on the tooth surface. This is followed by a 35-second nitrogen purging process, slightly longer than the tetraisopropoxide purging time. This is because H2O molecules are highly polar and have a stronger adsorption capacity, requiring a longer carrier gas purging time to thoroughly remove residues and avoid affecting the starting state of the next reaction cycle. This reaction step constitutes half a cycle.

[0057] The above-mentioned "tetraisopropoxide titanium pulse" and "H2O pulse" steps are performed alternately. These two "half-cycles" constitute one complete cycle. The number of cycles for TiO2 deposition can be modified and determined according to the actual situation. The scanning electron microscope results of the fracture surface of the tooth sample with hidden cracks after ALD are shown below. Figure 2 As shown in the figure, it can be seen that there is an accumulation of material at the opening of the dentinal tubules.

[0058] Artificial saliva was prepared and used to soak ALD-treated cracked tooth samples. The longer the soaking time, the more minerals formed. The scanning electron microscopy results of the cracked tooth samples soaked in artificial saliva are shown below. Figure 3 As shown in the figure, a large number of spherical minerals have been formed.

[0059] Figure 4 This is an EDS (Energy Dispersive Spectrum) result of a cracked tooth sample processed by the method described in this invention. Figure 4 It can be seen that the processed cracked tooth sample contains not only the three elements of calcium phosphate, but also titanium. Figure 5 The images show the IR images of a cracked tooth sample before and after processing by the method described in this invention. Figure 5 The horizontal axis represents wavenumber, and the vertical axis represents intensity. From Figure 5 It can be seen that Ti-O bonds have been formed in the treated cracked tooth sample.

[0060] Figure 6This is a schematic diagram of the heat insulation effect evaluation device. In the diagram, a thermal infrared imager (FLUKE) is used to record the temperature changes of the teeth during contact heat transfer. Thermal infrared imaging is performed on samples of cracked teeth before treatment and after treatment using the method described in this invention. The heating device for contact heat transfer includes a retractable control rod (threaded rod) and a heating platform. The heating platform consists of a heating strip (connected to the upper wire), a copper plate (shown in yellow), and a temperature control probe (connected to the lower wire). The heating strip heats the copper plate, which contacts the surface of the cracked tooth to simulate contact between a hot solid and the tooth. The temperature of the copper plate is set to 50°C. The thermal infrared imager starts timing from the initial contact of the copper plate with the cracked tooth surface, taking one image every 20 seconds until the tooth surface temperature no longer changes, obtaining the following results: Figure 7 The diagram shows the heat insulation effect.

[0061] Figure 7 The images show the thermal insulation effect of a cracked tooth sample before and after treatment using the method described in this invention. Figure 7 In the images below, the top row shows samples of cracked teeth before treatment, and the bottom row shows samples of cracked teeth after treatment using the method described in this invention. The blue color of the teeth in each bottom image is darker than that in each top image, indicating that the temperature conduction rate of the cracked teeth samples treated with the method described in this invention is significantly reduced. This means that the method described in this invention can effectively isolate temperature, and the method and apparatus described in this invention are suitable for repairing cracked teeth.

[0062] Figure 8 This is a schematic diagram of a device for repairing cracked teeth intraorally. The device includes a reaction chamber 1 for insertion into the cracked tooth, a sealing ring 2 around the periphery of the reaction chamber, a heater 3 inside the reaction chamber, an air inlet pipe 5 and an exhaust pipe 6 connected to the reaction chamber, and a baffle 4 within the reaction chamber to separate the airflow at the air inlet and exhaust pipes. The heater is mounted on the baffle. Multiple raw material containers 7 are connected in parallel at the other end of the air inlet pipe. The raw material containers include a titanium precursor container 71, an oxygen source container 72, and an inert gas container 73. The device includes a gas container 73, a titanium precursor container containing titanium tetraisopropoxide, an oxygen source container containing water, an evaporator 74 on both the titanium precursor container and the oxygen source container, and a high-speed solenoid valve 8 at the outlet of each raw material container; the other end of the exhaust pipe is connected to an exhaust valve 9, a vacuum gauge 10, a vacuum pump 11 and an exhaust gas treatment container 12; the device also includes a temperature controller 13 and a controller 14, the temperature controller being electrically connected to the heater and the evaporator, and the controller being electrically connected to the temperature controller, the high-speed solenoid valve and the exhaust valve.

[0063] The present invention achieves at least the following functions and effects.

[0064] 1. ALD deposition of titanium dioxide to seal dentinal tubules.

[0065] Atomic layer deposition (ALD) is a nanoscale thin film preparation technique based on chemical vapor deposition, possessing unique advantages such as self-limiting surface reactions, precise thickness control, and excellent uniformity. In its application of sealing dentinal tubules, from a microscopic perspective, the deposited TiO2 film typically ranges in thickness from a few nanometers to tens of nanometers, precisely covering and effectively sealing exposed dentinal tubules on the walls of dental fissures. This sealing effect significantly reduces dentin permeability, preventing external stimuli (such as cold, heat, acid, and sweetness) from being conducted to the dental pulp through the dentinal tubules, thereby alleviating dentin hypersensitivity symptoms. Simultaneously, the TiO2 film can also, to some extent, resist the invasion of bacteria and their metabolites into the dentinal tubules, reducing the risk of tooth decay.

[0066] 2. Titanium dioxide induces the formation of calcium phosphate.

[0067] Titanium dioxide (TiO2) plays a crucial role in inducing calcium phosphate formation due to its unique surface chemistry and photocatalytic activity. The TiO2 surface possesses numerous hydroxyl (-OH) groups, which can react with calcium ions (CaO) in aqueous solution. 2+ Complexation occurs, leading to the accumulation of calcium ions on the TiO2 surface. When phosphate ions (PO4) are present in the environment... 3- When calcium ions are enriched, they combine with phosphate ions and gradually form calcium phosphate salts through a series of chemical reactions and crystal growth processes.

[0068] From a crystallographic perspective, the initially formed calcium phosphate is usually amorphous calcium phosphate (ACP), whose structure is unstable and gradually transforms into the more stable hydroxyapatite (HAp). TiO2 can act as a template or catalyst, guiding the calcium phosphate crystals to grow along specific directions, forming a hydroxyapatite crystal structure similar to the inorganic components of natural dentin. In dental applications, this induced calcium phosphate layer is of great significance: firstly, it can be used to repair dentin defects, as the newly formed hydroxyapatite tightly integrates with the original dentin structure, enhancing the mechanical properties of the tooth tissue; secondly, it can form a protective layer on the dentin surface, further sealing dentinal tubules and improving the tooth's resistance to caries.

[0069] This invention belongs to the field of new medical materials and discloses a method for repairing cracked tooth samples, comprising: first, placing the cracked tooth sample in an ALD reaction chamber and evacuating it; introducing gaseous titanium precursor tetraisopropoxide titanium, which undergoes a monolayer reaction on the cracked tooth sample to form Ti-O bonds, completing the first deposition half-cycle; purging the reaction chamber with inert gas; then introducing an oxygen source to form a TiO2 film, completing the second deposition half-cycle; repeating the first and second deposition half-cycles multiple times until a TiO2 film grows on the cracked tooth sample; immersing the ALD-treated cracked tooth sample in artificial saliva to induce remineralization using the TiO2 film to form minerals. This invention also provides a device for repairing cracked teeth in the oral cavity. The device and method described in this invention can achieve precise repair of cracked teeth or in vitro cracked tooth samples, and can also reduce the risk of bacterial infections such as pulpitis and periapical periodontitis in the oral cavity. Specifically, the deposited TiO2 film and the induced minerals in this invention can precisely cover the exposed dentinal tubules on the walls of dental fissures, reducing dentin permeability and preventing the transmission of external hot and cold stimuli, thereby alleviating dentin hypersensitivity symptoms. The TiO2 film can also, to a certain extent, resist the invasion of bacteria and their metabolites into the dentinal tubules, reducing the risk of bacterial infections such as pulpitis and apical periodontitis.

[0070] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for repairing a cracked tooth sample, characterized in that, The method is a method for in vitro restoration of cracked tooth samples, wherein the cracked tooth samples are obtained by pretreatment of extracted teeth; the method includes the following steps: Step S1: Deposit a TiO2 thin film on the cracked tooth sample using atomic layer deposition (ALD) technology; specifically including: Step S1.1: Place the cracked tooth sample in the ALD reaction chamber and evacuate the reaction chamber; Step S1.2: Introduce gaseous titanium precursor into the reaction chamber. The titanium precursor is titanium tetraisopropoxide. The titanium precursor undergoes a monolayer reaction at the hydroxyl sites on the inner wall of the dentinal tubules of the cracked tooth sample to form Ti-O bonds, completing the first half-cycle of deposition. Then, inert gas is introduced to purge the reaction chamber to remove unreacted titanium precursor. Step S1.3: Introduce an oxygen source into the reaction chamber. The oxygen source is water vapor or O3. The oxygen source reacts with the titanium precursor adsorbed on the inner wall of the dentinal tubules to form a TiO2 monolayer film. This is the second half-cycle of deposition. Then, an inert gas is introduced to purge the reaction chamber to remove unreacted oxygen source and byproducts. Step S1.4: Repeat steps S1.2 and S1.3 multiple times until a uniform and dense TiO2 film grows layer by layer on the inner wall of the crack in the tooth sample. Step S2: Soak the ALD-treated cracked tooth sample in saliva or artificial saliva for 2 to 30 days to finally obtain the remineralized cracked tooth.

2. The method according to claim 1, characterized in that, Before step S1, the pretreatment steps for extracted teeth include: first, placing the collected extracted teeth in liquid nitrogen for 25-35 seconds, and then placing them in hot water at 95-100°C for 25-40 seconds to obtain the tooth sample with hidden cracks.

3. The method according to claim 1, characterized in that, In step S1, the atomic layer deposition temperature in the ALD reaction chamber is 90-180°C; the temperature of the titanium precursor is greater than 80°C before it is introduced into the reaction chamber.

4. The method according to claim 1, characterized in that, In step S1.2, the inert gas is nitrogen, the pulse time of the titanium precursor is 0.8~1.5 seconds, and it is held for 6~10 seconds after the pulse ends; then the nitrogen purging program is started and lasts for t1 seconds, t1=25~35, to remove the unadsorbed titanium precursor vapor remaining in the reaction chamber.

5. The method according to claim 1, characterized in that, In step S1.3, the inert gas is nitrogen, the pulse time of the oxygen source is 0.08~0.2 seconds, and it is held for 5~10 seconds after the pulse; then the nitrogen purging program is started and lasts for t2 seconds, t2=32~40, and t2>t1, in order to remove the residual oxygen source and by-products in the reaction chamber.

6. The method according to claim 1, characterized in that, In step S1.4, steps S1.2 and S1.3 are repeated 2 to 10 times.

7. A device for repairing cracked teeth in the oral cavity, characterized in that, The device includes a reaction chamber (1) for insertion into a cracked tooth in the oral cavity. A sealing ring (2) is provided around the periphery of the reaction chamber (1). A heater (3) is installed inside the reaction chamber (1). An air inlet pipe (5) and an exhaust pipe (6) are connected to the reaction chamber (1). Multiple raw material containers (7) are connected in parallel at the other end of the air inlet pipe (5). Each raw material container (7) includes a titanium precursor container (71), an oxygen source container (72), and an inert gas container (73). The titanium precursor container (71) contains titanium tetraisopropoxide, and the oxygen source container (72) contains water. Evaporators (74) are provided on both the precursor container (71) and the oxygen source container (72), and a high-speed solenoid valve (8) is provided on the outlet of each raw material container (7); the other end of the tail gas pipe (6) is connected to a tail gas valve (9), a vacuum gauge (10), a vacuum pump (11) and a tail gas treatment container (12); the device also includes a temperature controller (13) and a controller (14), the temperature controller (13) is electrically connected to the heater (3) and the evaporator (74), and the controller (14) is electrically connected to the temperature controller (13), the high-speed solenoid valve (8) and the tail gas valve (9).

8. The apparatus according to claim 7, characterized in that, The reaction chamber (1) is also provided with a baffle (4) for separating the airflow at the inlet pipe (5) and the outlet pipe (6), and the heater (3) is provided on the baffle (4).

9. The apparatus according to claim 7, characterized in that, The shape of the reaction chamber (1) is matched with the shape of a certain molar in the oral cavity, and the reaction chamber (1) leaves space for air intake and exhaust.

10. The apparatus according to claim 7, characterized in that, The reaction chamber (1) is shaped like a saddle or a saddle pad.

Images