Oral acid etching agent, preparation method and application thereof

Abstract

The application belongs to the technical field of oral cavity bonding, and particularly relates to an oral cavity acid etching agent and a preparation method and application thereof. The oral cavity acid etching agent comprises theaflavins and hydroxyacetic acid. The oral cavity acid etching agent provided by the application enhances the strength of the demineralized dentin collagen fiber, inhibits the activity of MMPs, blocks the progress of caries, and increases the durability of the dental resin filling body by adding the theaflavins.

Description

Technical Field

[0001] This invention belongs to the field of oral bonding technology, specifically relating to an oral etching agent, its preparation method, and its application. Background Technology

[0002] Dental caries, commonly known as cavities or tooth decay, is a major and frequently occurring oral disease, and one of the most prevalent diseases in humans. The World Health Organization has listed it alongside cancer and cardiovascular disease as one of the three major diseases requiring prevention and control. Dental caries is a progressive lesion of the hard tissues of the teeth caused by a combination of factors in the oral cavity. It manifests as demineralization of inorganic matter and decomposition of organic matter, evolving from discoloration to the formation of substantial lesions as the disease progresses. It can lead to secondary pulpitis and periapical periodontitis, and even inflammation of the alveolar bone and jawbone. If left untreated, the lesion continues to develop, forming cavities, and eventually causing complete destruction and loss of the tooth crown.

[0003] The currently accepted theory of dental caries etiology is the four-factor theory, which mainly includes bacteria, oral environment, host (i.e., parasites including parasites, viruses, etc.), and time. Its basic points are: cariogenic food sugars adhere tightly to the acquired membrane formed by salivary proteins on the tooth surface. This membrane, formed by the anatomical structure and biochemical and biophysical characteristics of the tooth surface, not only adheres firmly to the tooth surface but also, under suitable temperatures, has sufficient time to produce acid deep within the plaque, attacking the enamel and dentin, causing demineralization, and subsequently destroying organic matter, resulting in cavities.

[0004] The goal of dental caries prevention and treatment is to stop the disease process, prevent its further development, and restore the tooth's inherent shape and function. Due to the special structure of teeth, although they have the ability to remineralize, they do not have the ability to repair substantial defects on their own. Therefore, dental restorations, such as amalgam fillings, resin fillings, inlays, and artificial crowns, are used depending on the extent and volume of the tooth defect to restore its shape and function. These are commonly known as fillings and restorations.

[0005] The matrix metalloproteinase (MMP) family is a collective term for a class of secretory or membrane-associated zinc endopeptidases that share high structural homology and conservation. MMPs are present in normal adult tissues, but their expression and activity are usually low. Their expression and activity increase in many destructive pathological processes, such as chronic inflammation and bone destruction. They can degrade extracellular matrix (ECM) components such as fibrin, collagenase, fibronectin, and gelatinase, and play an important role in the remodeling of normal tissues. The role of MMPs in periodontal tissue lesions has been widely confirmed, and they also play important roles in tooth development, mineralization, and caries formation.

[0006] Tooth development results from epithelial-mesenchymal interactions. The basement membrane, located between the enamel organ and the dental papilla, is considered a reservoir of signaling molecules between the epithelium and mesenchyme, regulating and mediating the transmission of these molecules. However, when mature odontoblasts begin secreting pre-dentin matrix, the basement membrane gradually degrades and becomes discontinuous. Pre-ameloblasts then directly interact with odontoblasts. When enamel matrix secretion begins, the basement membrane completely disappears. Therefore, the remodeling and degradation of the basement membrane are crucial during tooth development.

[0007] The main component of the basement membrane is W-type collagen. MMP-2 and MMP-9 are known to be W-type collagenases, which cleave natural W-type collagen molecules at a single site in the helical region to form fragments. Furthermore, they can also degrade natural V, VH, and X-type collagen, gelatin, elastin, and fibronectin.

[0008] MMPs present in the pulp-dentin complex, such as MMP-8, can also participate in the remodeling of the pulp connective tissue. Intrinsic MMPs are mainly located on collagen in the mineralized dentin matrix rather than on hydroxyapatite crystals, and remain active. Therefore, research suggests that bacteria alone are insufficient to cause caries; bacterial acid production removes minerals, exposing the organic matrix, which in turn activates host MMPs. After demineralization reaches a certain level, the pH gradually rises due to the buffering effect of saliva, increasing MMP activity and causing the organic matrix to disintegrate, thus affecting reparative dentin formation. It is generally believed that in the caries process, cariogenic bacteria in the oral cavity first produce acid, causing demineralization of enamel and dentin, followed by the disintegration of the dentin organic matrix and cavity formation. Typically, most people have cavities and should rely on a dentist to use resin materials for fillings or restorations. Before fillings and restorations, the bonding interface is typically prepared using either full-etch bonding or self-etch bonding techniques. Pre-etching demineralizes the dentin matrix, which is the starting point for these bonding systems. The quality of the mixed layer formed by the adhesive and the demineralized dentin determines the success rate of the resin filling and restoration. Pre-etching allows the dental adhesive to fully penetrate the enamel and the collagen fiber network exposed by demineralization, resulting in stable bond strength and durability. Simultaneously, during the filling process, an etching agent is used to treat the enamel and dentin, completely removing the smear layer and forming a 3-5 μm demineralized layer on the dentin surface. A primer is then applied to improve the wettability of the dentin surface, allowing the adhesive to penetrate the demineralized collagen fiber framework and form an intertwined mixed layer, serving as a transitional structure connecting the restorative resin and dentin. This mixed layer, along with the resin projections penetrating the dentinal tubules, provides retention, but the mixed layer plays a primary role in retention. Therefore, the filling process requires demineralization and cleaning of the dentin and inhibition of matrix metalloproteinases, so pre-etching directly affects the effect and lifespan of the filling.

[0009] Currently, traditional acid etchants are mainly phosphoric acid etchants, which have certain side effects. The main problem is that phosphoric acid has a small molecular weight and strong acidity, which can easily lead to excessive demineralization of dentin. Since the main components of dental adhesives are non-hydrophilic macromolecular materials, they cannot completely penetrate to the depth of phosphoric acid demineralization. As a result, the demineralized dentin type I collagen cannot be completely encapsulated by the adhesive, affecting the bonding strength, causing resin filling failure and shortening its lifespan.

[0010] Glutaraldehyde (GA), an artificial chemical agent capable of rapidly cross-linking with demineralized dentin collagen fibers and producing cross-linked products resistant to hydrolysis by matrix metalloproteinases (MMPs), is considered the "gold standard" in cross-linking agent research. However, while glutaraldehyde exhibits excellent cross-linking properties, its reaction time (at least 30 seconds for high concentrations) still limits its practical clinical application (as patients cannot keep their mouths open for extended periods during clinical procedures). Furthermore, its significant biotoxicity is a drawback that cannot be ignored in clinical use. Summary of the Invention

[0011] This invention provides an oral etching agent that, by adding theaflavins, enhances the strength of demineralized dentin collagen fibers, inhibits MMPs activity, blocks the progression of caries, and simultaneously increases the durability of dental resin fillings.

[0012] The oral etching agent provided by this invention contains theaflavins and glycolic acid.

[0013] Preferably, one or a combination of theaflavins-3-monogallate, theaflavins-3'-monogallate, or theaflavins-3,3'-digallic acid can replace the theaflavins or be used in combination with the theaflavins.

[0014] Preferably, the oral etching agent comprises the following raw materials by weight: 3-6 parts theaflavins, 30-38 parts glycolic acid, 0.01-0.15 parts antioxidant, 0.01-0.1 parts thickener, 0.1-1 parts buffer, 0.01-0.1 parts surfactant, 0.01-0.1 parts antiflocculation agent, and 55-65 parts deionized water.

[0015] More preferably, the antioxidant is one or more of ascorbic acid, isoascorbic acid, or α-tocopherol;

[0016] The thickener is one or more of methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, and hydroxypropylmethylcellulose;

[0017] The buffer is sodium dihydrogen phosphate dihydrate, zinc citrate, or sodium citrate.

[0018] The surfactant is one or more of sodium alkylbenzene sulfonate, sodium stearate, N-dodecyl methylamine or sorbitan monostearate;

[0019] The antiflocculating agent is sodium carboxymethyl cellulose or chitosan.

[0020] The present invention also provides a method for preparing the above-mentioned oral etching agent, comprising the following steps:

[0021] S1. Weigh out 3-6 parts by weight of theaflavins, 30-38 parts by weight of glycolic acid, 0.01-0.15 parts by weight of antioxidant, 0.01-0.1 parts by weight of thickener, 0.1-1 parts by weight of buffer, 0.01-0.1 parts by weight of surfactant, 0.01-0.1 parts by weight of antiflocculation agent, and 55-65 parts by weight of deionized water, and set aside.

[0022] S2. Add the glycolic acid and antioxidant weighed in S1 to deionized water and dissolve to obtain a mixed solution;

[0023] S3. Add theaflavins, thickeners, buffers, surfactants, and antiflocculation agents to the mixed solution, stir for 30-60 minutes, and then fill into the container to obtain the oral etching agent.

[0024] Preferably, the preparation temperature in S1-S2 is 20-50℃.

[0025] The oral etching agent provided by this invention can be used for the prevention of dental caries or as a pretreatment for resin filling restoration of non-carious defects.

[0026] Preferably, the oral etching agent can be used to enhance the bonding strength between the resin filling and the tooth surface, and to prolong the long-term retention of the resin filling in the moist environment of the oral cavity.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] 1. The oral etching agent provided by the present invention contains theaflavins containing multiple exposed hydroxyl groups, which can react with the amino groups in matrix metalloproteinase molecules, block the active sites of matrix metalloproteinases, inhibit the activity of matrix metalloproteinases, and block the corrosion of type I collagen in tooth enamel and dentin by matrix metalloproteinases, thereby delaying the progression of tooth decay.

[0029] 2. When theaflavins cross-link with collagen, they are non-hydrophilic and can transport water molecules from collagen, moving -OH bonds from hydrogen bond reaction regions to non-reactive regions. Collagen loses -OH bonds, and the increased number of hydrogen bonds leads to a significant increase in its own binding free energy. It can quickly chemically bind with theaflavins in their respective hydrogen bond reaction regions, producing stable cross-linked products that resist collagenase degradation.

[0030] 3. Theaflavins can quickly (in just 30 seconds) and effectively cross-link with type I collagen fibers after dentin demineralization, enhancing the strength of collagen fibers to resist the corrosive effects of acid on teeth.

[0031] 4. Dentin etched with glycolic acid not only has the same immediate bonding strength as dental dentin etched with phosphoric acid, which is commonly used in clinical practice, but also has a slower etching rate and shallower demineralization depth due to its larger molecular weight. On the one hand, this allows the theaflavins in the etchant to cross-link with the demineralized dentin simultaneously, forming an etching process that demineralizes while protecting the dentin collagen. On the other hand, it allows the dental adhesive to completely penetrate to the depth of glycolic acid demineralization, so that the demineralized type I collagen of the dentin is completely encapsulated by the adhesive, thereby achieving a more long-term and stable bonding effect. Attached Figure Description

[0032] Figure 1 This is a simplified diagram for shear bond strength testing; where 1-clamp; 2-loading head; 3-filling resin; 4-copper ring; 5-embedding resin; 6-dentin specimen;

[0033] Figure 2 These are electron micrographs (EM) of demineralized dentin under different treatment conditions: A and B are EEM images of demineralized dentin without crosslinking agent treatment (control group), with black arrows pointing to the demineralized layer; E and F are EEM images of demineralized dentin after soaking in 4 wt% TFs for 30 s, with white arrows pointing to the crosslinking reaction layer; G and H are EEM images of the control group after 1 h of enzymatic degradation; K and L are EEM images of the TFs-treated group after 1 h of enzymatic degradation, with white arrows pointing to the crosslinking reaction layer.

[0034] Figure 3 These are transmission electron micrographs (TEM) images of demineralized dentin under different treatment conditions; A1 is a TEM image of demineralized dentin without cross-linking agent treatment (control group), and A2 is a magnified image of the area indicated by the white arrow in image A1; B1 is a TEM image of the control group after 1 hour of enzymatic degradation, and B2 is a magnified image of the area indicated by the white arrow in image B1; D1 is a TEM image of demineralized dentin after immersion in 4 wt% TFs for 30 seconds and then enzymatic degradation for 1 hour, and D2 is a magnified image of the area indicated by the white arrow in image D1. Detailed Implementation

[0035] The present invention is further described below through embodiments, but the present invention is not limited to these embodiments.

[0036] Example 1

[0037] An oral etching agent, with the following specific component contents per 100 grams:

[0038] Theaflavins 3g

[0039] 35g of glycolic acid

[0040] Ascorbic acid 0.01g

[0041] Carboxymethyl cellulose 0.01g

[0042] 0.1g of sodium dihydrogen phosphate dihydrate

[0043] Sodium alkylbenzene sulfonate 0.01g

[0044] Sodium carboxymethyl cellulose 0.01g

[0045] 55.85g of water

[0046] Preparation method:

[0047] S1. Weigh out 3g theaflavins, 35g glycolic acid, 0.01g ascorbic acid, 0.01g zinc citrate, 0.1g sodium dihydrogen phosphate dihydrate, 0.01g sodium alkylbenzene sulfonate, 0.01g sodium carboxymethyl cellulose, and 55.85g deionized water for later use.

[0048] S2. Add the glycolic acid and antioxidant weighed in S1 to deionized water and dissolve to obtain a mixed solution;

[0049] S3. Add theaflavins, zinc citrate, sodium dihydrogen phosphate dihydrate, surfactant, and antiflocculation agent to the above mixed solution, stir for 30-60 minutes, and then fill into the container to obtain the oral etching agent.

[0050] The preparation temperature for each step in the above preparation method is 25℃.

[0051] Example 2

[0052] An oral etching agent, with the following specific component contents per 100 grams:

[0053] Theaflavin-3-monogallate 5g

[0054] 30g of glycolic acid

[0055] α-Tocopherol 0.1g

[0056] Carboxymethyl cellulose 0.1g

[0057] 1g of sodium dihydrogen phosphate dihydrate

[0058] Sodium alkylbenzene sulfonate 0.1g

[0059] Sodium carboxymethyl cellulose 0.1g

[0060] 58.6g of water

[0061] Preparation method:

[0062] S1. Weigh out 5g theaflavins-3-monogallate, 30g glycolic acid, 0.1g ascorbic acid, 0.1g zinc citrate, 1g sodium dihydrogen phosphate dihydrate, 0.1g sodium alkylbenzene sulfonate, 0.1g sodium carboxymethyl cellulose, and 58.6g deionized water for later use.

[0063] S2. Add the glycolic acid and antioxidant weighed in S1 to deionized water and dissolve to obtain a mixed solution;

[0064] S3. Add theaflavins, zinc citrate, sodium dihydrogen phosphate dihydrate, surfactant, and antiflocculation agent to the mixed solution, stir for 30-60 minutes, and then fill into the container to obtain the oral etching agent.

[0065] The preparation temperature for each step in the above preparation method is 25°C. The effects of the oral etching agent provided by this invention will be explained below.

[0066] Example 3

[0067] An oral etching agent, with the following specific component contents per 100 grams:

[0068] Theaflavin-3'-monogallate 6g

[0069] 38g of glycolic acid

[0070] Ascorbic acid 0.1g

[0071] Hydroxypropyl methylcellulose 0.1g

[0072] 1g of sodium dihydrogen phosphate dihydrate

[0073] Sodium alkylbenzene sulfonate 0.1g

[0074] N-Dodecylmethylamine 0.1g

[0075] 65.6g of water

[0076] Preparation method:

[0077] S1. Weigh out 6g theaflavins-3'-monogallate, 38g glycolic acid, 0.1g ascorbic acid, 0.1g zinc citrate, 1g sodium dihydrogen phosphate dihydrate, 0.1g sodium alkylbenzene sulfonate, 0.1g sodium carboxymethyl cellulose, and 65.6g deionized water for later use.

[0078] S2. Add the glycolic acid and antioxidant weighed in S1 to deionized water and dissolve to obtain a mixed solution;

[0079] S3. Add theaflavins, zinc citrate, sodium dihydrogen phosphate dihydrate, surfactant, and antiflocculation agent to the mixed solution, stir for 30-60 minutes, and then fill into the container to obtain the oral etching agent.

[0080] The preparation temperature for each step in the above preparation method is 25℃.

[0081] Example 4

[0082] An oral etching agent, with the following specific component contents per 100 grams:

[0083] Theaflavins-3,3'-digallic acid 5g

[0084] 35g of glycolic acid

[0085] Ascorbic acid 0.012g

[0086] Carboxymethyl cellulose 0.08g

[0087] Sodium citrate 0.8g

[0088] Sodium alkylbenzene sulfonate 0.6g

[0089] Sodium carboxymethyl cellulose 0.5g

[0090] 62.34g of water

[0091] Preparation method:

[0092] S1. Weigh out 6g theaflavins-3'-monogallate, 38g glycolic acid, 0.1g ascorbic acid, 0.1g zinc citrate, 1g sodium dihydrogen phosphate dihydrate, 0.1g sodium alkylbenzene sulfonate, 0.1g sodium carboxymethyl cellulose, and 65.6g deionized water for later use.

[0093] S2. Add the glycolic acid and antioxidant weighed in S1 to deionized water and dissolve to obtain a mixed solution;

[0094] S3. Add theaflavins, zinc citrate, sodium dihydrogen phosphate dihydrate, surfactant, and antiflocculation agent to the mixed solution, stir for 30-60 minutes, and then fill into the container to obtain the oral etching agent.

[0095] The preparation temperature for each step in the above preparation method is 25℃.

[0096] Example 5

[0097] The difference from Example 1 is that the theaflavins in Example 1 are replaced by an equal mass mixture of theaflavins-3-monogallate and theaflavins-3,3'-digallic acid, that is, the amount of both theaflavins-3-monogallate and theaflavins-3,3'-digallic acid added is 1.5g.

[0098] Example 6

[0099] The difference from Example 1 is that theaflavin-3-monogallate and theaflavin are mixed in equal mass to replace theaflavin in Example 1, that is, the amount of theaflavin-3-monogallate and theaflavin added is 1.5g each.

[0100] Example 7

[0101] The difference from Example 1 is that the theaflavins in Example 1 are replaced by a mixture of theaflavins-3-monogallate, theaflavins-3,3'-digallic acid, and theaflavins by mass, that is, the amount of each of theaflavins-3-monogallate, theaflavins-3,3'-digallic acid, and theaflavins added is 1g.

[0102] Example 8

[0103] The difference from Example 1 is that the theaflavins in Example 1 are replaced by a mixture of theaflavins-3-monogallate, theaflavins-3'-monogallate, theaflavins and theaflavins-3,3'-digallic acid in equal mass. Specifically, the amount of each of theaflavins-3-monogallate, theaflavins-3'-monogallate, theaflavins and theaflavins-3,3'-digallic acid added is 0.75g.

[0104] It should be noted that Examples 5-8 only list several cases of arbitrary combinations of theaflavins-3-monogallate, theaflavins-3'-monogallate, theaflavins, and theaflavins-3,3'-bisgallic acid. In actual applications, these four monomers do not necessarily need to be mixed in equal mass. They can be mixed in any proportion, as long as the total mass of the four monomers after arbitrary combination does not affect the effect of the oral etching agent provided by the present invention within the scope of this application.

[0105] The effects of the oral etching agent provided by this invention will be described below.

[0106] 1. Main materials and instruments

[0107] Theaflavin complex TFs (Sigma-Aldrich, USA, T5550-10MG, HPLC >80%), glutaraldehyde (GA, 25wt%, Hatfield, PA, USA), 35% phosphoric acid pre-gel (3M Company, USA), phosphoric acid (Sigma-Aldrich, USA), 0.1M PBS (Sigma-Aldrich, USA), hydrochloric acid (Sigma-Aldrich, USA), chlorhexidine (Sigma-Aldrich, USA), sodium hypochlorite (Sigma-Aldrich, USA), distilled water, ethanol (Sigma-Aldrich, USA), anhydrous acetone (Sigma-Aldrich, USA), liquid nitrogen;

[0108] Isomet 1000 slow cutter (Buehler, USA), Leica Polycut S slow cutter (Leica, Deerfield IL, USA), EX125ZH electronic analytical balance (Ohaus, USA), Raman (Perkin Elmer, Waltham, USA), FTIR (Perkin Elmer, Waltham, USA), Philips CM12 TEM (PHILIPS Company, Netherlands), Adper™ Single Bond 2 (3M ESPE, USA), Filtek Z250 (3M ESPE, USA).

[0109] 2 methods

[0110] 2.1 Experimental Subjects

[0111] Twenty freshly extracted, caries-free adult third molars were stored at 4°C in 0.01M PBS solution containing 0.002% sodium azide for later use after the periodontal soft tissue was removed.

[0112] 2.2 Prepare a 4 wt% solution of analytical grade TFs with deionized water and a 10 wt% solution of GA with deionized water. Store both solutions together in a 4°C refrigerator for later use.

[0113] 2.3 Preparation of TFs-treated samples for ESEM and TEM observation and research methods. The cross-linking agent treatment time was 30 s, and the enzyme degradation time was 1 h.

[0114] Sample preparation and grouping:

[0115] Using an Isomet1000 slow-speed cutter under cold water, 1 / 3 to 1 / 2 of the crown of the tooth was removed parallel to and perpendicular to the occlusal surface (complete removal of enamel). Whole dentin blocks were randomly selected. After preparing a smear layer with 600-grit sandpaper, dentin blocks with a thickness of 1 mm were prepared perpendicular to the smear layer for ESEM observation (Group A) and 0.5 mm dentin blocks were prepared for TEM observation (Group B). Eight dentin specimens were prepared for each of Groups A and B.

[0116] Group A was randomly divided into two subgroups (A1 and A2), with four samples in each subgroup. The smeared dentin layer was etched with 35% phosphate gel for 15 seconds, then rinsed with deionized water for 10 seconds. After complete drying, the A2 subgroup was immersed in 4 wt% TFs solution for 30 seconds. The A1 subgroup served as the control group without treatment. Two samples from each subgroup were randomly selected for direct ESEM observation without degradation, while the other two samples were degraded with 1 ml of 0.1 wt% collagenase at 37°C for 1 hour before ESEM observation. All samples (except those pre-prepared for ESEM) were fixed in 0.1 M sodium dimethylproline buffer + 2.5% glutaraldehyde for 1 hour, then dehydrated sequentially with 33%, 67%, 85%, and 95% ethanol for 30 minutes each. After drying for 24 hours, the samples were split, adhered to conductive adhesive, carbon-sprayed, and then observed by ESEM.

[0117] Group B was randomly divided into two subgroups (B1 and B2), with four samples in each subgroup. The smeared dentin layer was etched with 35% phosphate gel for 15 seconds, then rinsed with deionized water for 10 seconds. After complete drying, group B2 was soaked in 4 wt% TFs solution for 30 seconds. Group B1 served as the control group without treatment. Two samples from group B1 were randomly selected without degradation and directly prepared for TEM observation. The other two samples, along with those from group B2, were degraded in 1 ml of 0.1 wt% collagenase at 37°C for 1 hour before being prepared for TEM observation. All experiments were repeated three times.

[0118] 2.4 Micro-shear bond strength test

[0119] Sample preparation method: Approximately one-third of the length of the occlusal surface of six extracted teeth, perpendicular to their long axis, was completely removed using a slow-speed cutter. A smear layer was then prepared on the exposed intermediate dentin surface using 600-grit sandpaper under water cooling. The samples were randomly divided into three groups. The dentin surfaces of the smear layers in each group were etched with 35% phosphoric acid etching agent for 15 seconds, followed by rinsing with deionized water for 10 seconds. The surface water was then absorbed with absorbent paper. Two groups were treated with 10wt% GA and 4wt% TFs solutions, respectively, for 30 seconds, followed by absorption with absorbent paper. One group served as a control group without treatment. Adper™ Single Bond 2 adhesive (Etch-and-rinse) was applied according to the manufacturer's instructions and irradiated. A 4-5mm layer of Filtek Z250 resin was then applied and irradiated for 40 seconds, followed by immersion in deionized water for 24 hours. Using a slow-speed cutter under water cooling, dentin-resin strips measuring 0.7 mm x 0.7 mm x 8 mm were prepared along the long axis of the tooth from three groups of specimens, with approximately 12 strips prepared per tooth. The strips were randomly divided into two subgroups of eight specimens each. One subgroup underwent immediate microshear strength testing, while the other subgroup was immersed in a 0.01 M PBS solution containing 0.002% sodium azide at 37°C for six months (with the storage solution changed weekly) before undergoing microshear bond strength testing.

[0120] 2.5 Micro-shear bond strength test

[0121] The prepared sample is fixed on the universal testing machine using metal clamps. The bonding micro-bottom interface is parallel to the loading head plane, and the lowest point of the loading head is placed 0.5 mm away from the copper ring (e.g., Figure 1 As shown in the figure, a loading speed of 0.5 mm / min was set. The maximum load (N) at which the specimen fractured was recorded.

[0122] Shear bond strength (MPa) = Maximum breaking load (N) / Bond area (mm²) 2 ).

[0123] 2.6 Statistical Analysis Methods

[0124] One-way ANOVA was performed using IBM SPSS v.19 (NY, USA). Statistical inference between the two groups was performed using the small sample t-test, and P < 0.05 was considered statistically significant.

[0125] 3 Results

[0126] 3.1 ESEM Observation Results

[0127] Electron micrographs (AL: x5000) of demineralized dentin samples soaked in 4wt% crosslinking agent TFs for 30 seconds and then subjected to enzymatic degradation for 1 hour (experimental group) and demineralized dentin samples without crosslinking agent treatment (control group) before and after degradation under the same degradation conditions are shown below. Figure 2 As shown.

[0128] Figure 2 In the images, A and B are electron micrographs of demineralized dentin (control group) without cross-linking agent treatment, with black arrows pointing to the demineralized layer; E and F are electron micrographs of demineralized dentin after soaking in 4wt% TFs for 30s, with white arrows pointing to the cross-linking reaction layer; G and H are electron micrographs of the control group after 1h of enzymatic degradation; K and L are electron micrographs of the TFs-treated group after 1h of enzymatic degradation, with white arrows pointing to the cross-linking reaction layer.

[0129] 3.2 TEM Results

[0130] Transmission electron microscopy (TEM) images of demineralized dentin samples soaked in 4 wt% crosslinking agent TFs for 30 seconds and then subjected to enzymatic degradation for 1 hour (experimental group) and demineralized dentin samples without crosslinking agent treatment (control group) before and after degradation under the same degradation conditions are shown below. Figure 3 As shown.

[0131] Figure 3 In the image, A1 is a transmission electron microscope (TEM) image of demineralized dentin (control group) without cross-linking agent treatment, and A2 is a magnified image of the area indicated by the white arrow in image A1; B1 is a TEM image of the control group after 1 hour of enzymatic degradation, and B2 is a magnified image of the area indicated by the white arrow in image B1; D1 is a TEM image of demineralized dentin after immersion in 4 wt% TFs for 30 seconds and enzymatic degradation for 1 hour, and D2 is a magnified image of the area indicated by the white arrow in image D1.

[0132] 3.3 Micro-shear bond strength

[0133] The test results are shown in Table 1.

[0134] Table 1 shows that the bond strength of the experimental groups was greater than that of the control group, and the difference was statistically significant (P<0.05). Pairwise comparisons between experimental groups showed that the TFs group was stronger than the GA group, and the difference was statistically significant (P<0.05). After soaking in deionized water at 37℃ for 6 months, the bond strength between dentin and resin in each group was tested. The results showed that the bond strength of each experimental group was greater than that of the control group, and the difference was statistically significant (P<0.05). The bond strength of the TFs group after 6 months was slightly lower than its immediate bond strength, but the difference was not statistically significant (P>0.05).

[0135] Table 1. Effect of different storage times after treatment with different crosslinking agents on the microshear bond strength of dentin-resin (n=8)

[0136] immediate 40.09±5.02 <![CDATA[54.56±4.08 Ba ]]> <![CDATA[58.02±3.87 Ca ]]> 6 months later 26.15±5.30 <![CDATA[50.96±6.12 Bb ]]> <![CDATA[57.64±4.88 Ca ]]>

[0137] Note: Different uppercase superscript letters indicate that the difference between this group and the control group is statistically significant; different lowercase superscript letters indicate that the difference between groups in the same category is statistically significant (P<0.05).

[0138] The above results indicate that TFs can rapidly cross-link with exposed collagen fibers in demineralized dentin, enabling the demineralized dentin to resist degradation by proteolytic enzymes. Qualitative studies using ESEM and TEM at 4 wt% TF concentration and 30 s treatment showed that TFs protected the demineralized dentin from degradation by proteolytic enzymes, while the control group, without cross-linking agent treatment, showed complete disappearance of the demineralized layer after enzymatic degradation (see...). Figure 2 G, H and Figure 3 B1 and B2 indicate that TFs have the ability to rapidly undergo chemical cross-linking reactions with demineralized dentin collagen fibers.

[0139] TFs, commonly known as theaflavins, are a class of naturally derived high-molecular-weight compounds formed by the benzoic acid cyclization reaction of catechins, precursors of natural tea polyphenols. These compounds mainly contain four monomers: theaflavin (TF1), theaflavin-3-gallate (TF2), theaflavin-3'-gallate (TF3), and theaflavin-3,3'-bisgallate (TF4, TFdG). This complex typically constitutes 0.3% to 1.5% of tea leaves and is hailed as "soft gold" in tea. It possesses unique lipid-lowering properties, not only reducing cholesterol absorption but also inhibiting the body's own cholesterol synthesis. Furthermore, it exhibits anti-cancer, antibacterial, anti-caries, and preventative effects against oral cancer and periodontal disease. As can be seen from the present invention, the theaflavins complex can also quickly protect demineralized dentin collagen fibers from degradation by protein-degrading enzymes.

[0140] This invention compares the effective concentration (4 wt%, determined based on previous experimental experience) of GA and TFs as pretreatment agents before bonding. In an in vitro simulation of dental bonding using the etch-and-rinse technique on dentin, dentin-resin specimens were obtained by treating the dentin after demineralization for 30 seconds, followed by the final bonding step. The bond strength of the dentin to resin was then tested. The immediate results were stronger than the control group without crosslinking agents (P<0.05), directly demonstrating that crosslinking agents can enhance the bond strength between dentin and resin. After 6 months of immersion in a simulated oral environment, the bond strength between dentin and resin in the control group significantly decreased (P<0.05), and the GA group also showed a decrease compared to 6 months prior (P<0.05). The TFs group showed no significant decrease in bond strength. This indicates that the theaflavins complex's ability to enhance the long-term bond strength and stability between dentin and resin is highly promising and worthy of further research.

[0141] Low-concentration TFs possess the same ability as high-concentration GA to rapidly crosslink demineralized dentin collagen fibers and enhance their resistance to enzymatic degradation. Furthermore, TFs can enhance the immediate bond strength between dentin and resin at low concentrations, with effects comparable to high-concentration GA. In maintaining the long-term bond between dentin and resin, the low-concentration TFs group is significantly superior to the high-concentration GA group.

[0142] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An oral acid etchant, characterized by, The oral etching agent comprises the following raw materials by weight: 3-6 parts theaflavins, 30-38 parts glycolic acid, 0.01-0.15 parts antioxidant, 0.01-0.1 parts thickener, 0.1-1 parts buffer, 0.01-0.1 parts surfactant, 0.01-0.1 parts antiflocculation agent, and 55-65 parts deionized water; The theaflavins contain multiple exposed hydroxyl groups, which can react with the amino groups in matrix metalloproteinase molecules to block the active sites of matrix metalloproteinases and prevent matrix metalloproteinases from corroding type I collagen in tooth enamel and dentin. Furthermore, the theaflavins undergo a cross-linking reaction with type I collagen fibers after dentin demineralization to enhance the strength of collagen fibers and resist the corrosive effect of acid on teeth. The glycolic acid is used to etch dentin. On the one hand, it enables the theaflavins to cross-link with the demineralized dentin, forming an acid etching process that demineralizes while protecting dentin collagen. On the other hand, it allows the adhesive to fully penetrate to the depth of glycolic acid demineralization, so that the demineralized dentin type I collagen is completely encapsulated by the adhesive.

2. The oral etching agent according to claim 1, characterized in that, Theaflavin-3-monogallate, theaflavin-3'-monogallate, and theaflavin-3,3'-digallic acid, or a combination thereof, can replace the theaflavin or be used in combination with the theaflavin.

3. The oral etching agent according to claim 1, characterized in that... The antioxidant is one or more of ascorbic acid, isoascorbic acid, or α-tocopherol; The thickener is one or more of methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, and hydroxypropylmethylcellulose; The buffer is sodium dihydrogen phosphate dihydrate, zinc citrate, or sodium citrate; the surfactant is one or more of sodium alkylbenzene sulfonate, sodium stearate, N-dodecyl methylamine, or sorbitan monostearate; and the antiflocculation agent is sodium carboxymethyl cellulose or chitosan.

4. The method for preparing the oral etching agent according to claim 1, characterized in that, Includes the following steps: S1. Weigh out 3-6 parts by weight of theaflavins, 30-38 parts by weight of glycolic acid, 0.01-0.15 parts by weight of antioxidant, 0.01-0.1 parts by weight of thickener, 0.1-1 parts by weight of buffer, 0.01-0.1 parts by weight of surfactant, 0.01-0.1 parts by weight of antiflocculation agent, and 55-65 parts by weight of deionized water, and set aside. S2. Add the glycolic acid and antioxidant weighed in S1 to deionized water and dissolve to obtain a mixed solution; S3. Add theaflavins, thickeners, buffers, surfactants, and anti-flocculation agents to the mixed solution, stir for 30-60 minutes, and then fill into the container to obtain the oral etching agent.

5. The method for preparing the oral etching agent according to claim 4, characterized in that, In S1~S2, the preparation temperature is 20~50℃.

6. The application of the oral etching agent according to any one of claims 1 to 3 in the pretreatment of resin filling restoration for non-carious defects.

7. The application according to claim 6, characterized in that, The oral etching agent can be used to enhance the bonding strength between the resin filling and the tooth surface, and to prolong the longevity of the resin filling in the moist environment of the oral cavity.

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