High-powder-liquid-ratio easy-flowing root canal filling paste and preparation method thereof

Abstract

The invention discloses an easy-to-flow root canal filling paste with a high powder / liquid ratio and a preparation method of the easy-to-flow root canal filling paste. The paste comprises a powder solid phase system and an organic liquid phase system, and the powder-liquid ratio is (5-7): 1; the powder solid phase system comprises a curing component, an X-ray radiation-resistant component, a filler and an additive containing organic bentonite; the organic liquid phase system comprises water, an organic solution, a carrier and a stabilizer containing hexadecyl sulfopropyl betaine. The preparation method of the paste comprises the following steps: mechanically activating the surface of a powder solid-phase system, adding the powder solid-phase system into an organic liquid-phase system, and uniformly mixing to obtain the paste. According to the root canal filling paste, on the basis of the synergistic effect between organic bentonite in a powder solid phase system and hexadecyl sulfopropyl betaine in an organic liquid phase system, the powder-liquid ratio of the paste is greatly increased, and meanwhile the flowability of the paste is greatly improved; the technical problems that after powder is refined, the liquid phase content is too large, so that curing reaction is too fast, and cracking is likely to happen are effectively solved.

Description

Technical Field

[0001] The present invention relates to a root canal filling paste, in particular to a high powder-liquid ratio and easily flowable root canal filling paste and a preparation method thereof, belonging to the technical field of root canal materials. Background Art

[0002] Root canal treatment is a commonly used treatment method for pulp diseases and periapical diseases. Root canal treatment removes most of the infective substances in the root canal by mechanical and chemical methods, fills the root canal, and seals the crown to prevent the occurrence of periapical lesions or promote the healing of existing periapical lesions. Root canal filling refers to tightly filling the entire root canal system, including the main root canal, lateral canals, accessory canals, and various irregular areas of the root canal. Among them, the lateral canals are small branches originating from the root canal. The morphology of the lateral canals is mainly oval and often curved. The lateral canals are thinner and more variable than the main root canal. Although root canal irrigation can remove most of the bacteria in the root canal, it is difficult to completely remove the bacteria in the lateral canals. Some lateral canals communicate with the periodontal tissue, allowing bacteria to enter the periapical tissue, causing periapical discomfort and even treatment failure. Improving the cleaning degree, filling rate, and root filling density of the lateral canals has a positive effect on improving the success rate of root canal treatment.

[0003] The substances used to fill root canals during root canal treatment are collectively referred to as root canal filling materials. The effect of root canal treatment is closely related to the performance of root canal filling materials. Currently, the commonly used root canal filling materials in clinical practice mainly include zinc oxide eugenol, calcium hydroxide, composite resin, glass ionomer, calcium silicate-based bioceramics, etc. Among them, bioceramic root canal filling materials have good physical, chemical and biological properties, and their clinical applications are becoming increasingly widespread. Fluidity is an important technical index of bioceramic root canal filling materials. Pastes with good fluidity are more likely to fill into lateral root canals. In "YY0717-2009 Dental Root Canal Sealing Materials", the fluidity index of the experimental material is that the diameter should not be less than 20 mm. In "ISO6876-2012 Dentistry—Root Canal Sealing Materials", the fluidity index of the material is 17 mm, with a lower requirement for fluidity. There are patents disclosing bioceramic filling materials based on calcium silicate and calcium phosphate (US patent 5415547; US Patent 8722100; USUS patent 5769638; WO / 2011 / 023199; CN 200880011743.1; CN107080697A). However, according to the publicly available literature, the fluidity of bioceramic root canal filling pastes based on these patents is close to that of traditional resin-based materials and gutta-percha materials, all of which are less than 25 mm (Zhou H M, Dds Y S, Zheng W, et al. Physical Properties of5 Root Canal Sealers[J]. Journal of Endodontics, 2013, 39(10):1281-1286.)(DONNERMEYER, David, et al. Physico-chemical investigation of endodontic sealersexposed to simulated intracanal heat application: hydraulic calcium silicate-based sealers. Materials, 2021, 14.4:728.).When the test temperature increases, this value will further decrease (CHEN, Binwen, et al. Cytotoxicity and the effect of temperature on physical properties and chemical composition of a new calcium silicate-based root canal sealer. Journal of endodontics, 2020, 46.4: 531-538.). Patents CN202210218363.7 and CN201810902541.1 added strontium silicate to the solid-phase powder, and patent CN202111144472.0 added bioactive glass to the solid-phase powder. The publicly available patent documents CN113520884B, CN201710205826.5, CN201710205844.3, CN201711277843.6, and CN201610777530.6 mainly focus on the setting time, stability, adhesion, antibacterial properties, etc. of the materials, lacking attention and quantitative research on the fluidity of root canal filling materials.

[0004] When filling lateral canals, the root canal filling paste often fails to fully fill the lateral canals. The reason for this phenomenon is that the lateral canals are small in size, with an average diameter usually in the order of dozens of micrometers, an average length of several hundred micrometers, and an irregularly curved shape. The average particle size of some root canal filling paste powders is about 10 micrometers, which is close to the diameter of the lateral canals, making it difficult to fill. Therefore, the paste needs fine powder particles to fill the lateral canals. However, after the powder is refined, the specific surface area increases significantly, and the amount of liquid required to wet the powder surface becomes larger. More liquid is needed to obtain excellent fluidity, thereby reducing the proportion of the powder in the paste. When the solid content is too low, it will lead to more pores, poor sealing, and reduced radiopacity to X-rays. In addition, powder refinement is prone to causing too fast curing reaction and easy curing cracking due to large volume changes. Moreover, pastes without water or almost without water have poor wettability to the root canal and are difficult to enter the lateral canals due to the action of surface tension. In summary, whether it is possible to effectively fill the lateral canals by obtaining easy flowability from the design and preparation method of the paste itself remains an unsolved problem for existing root canal filling pastes. Summary of the Invention

[0005] In view of the problems existing in the prior art, the first object of the present invention is to provide a high powder-liquid ratio and easily flowable root canal filling paste. Based on the synergistic effect between the organobentonite in the inorganic powder solid phase system and the cetylsulfopropyl betaine in the organic liquid phase system, this root canal filling paste can play a good wetting role between the refined powders without increasing the liquid phase content. Thus, while greatly increasing the powder-liquid ratio of the paste, it also significantly improves the fluidity of the paste, effectively solving the technical problems of too fast curing reaction and easy cracking caused by excessive liquid phase content after powder refinement in the prior art, and can effectively fill the lateral root canals.

[0006] The second object of the present invention is to provide a preparation method of a high powder-liquid ratio and easily flowable root canal filling paste. This method first refines the powder into nanoscale by surface mechanical activation, which is more likely to enter the lateral root canals in terms of size. Then, an organic liquid phase system is added and mixed evenly to increase the wettability of the paste to the root canal, and the coordination interaction between cellulose and bentonite is utilized to improve the powder accommodation capacity of the tough hydrogel per unit volume, thereby endowing the paste with excellent fluidity and microscopic adhesion strength.

[0007] To achieve the above technical objects, the present invention provides a high powder-liquid ratio and easily flowable root canal filling paste. The paste comprises a powder solid phase system and an organic liquid phase system, and its powder-liquid ratio is 5-7:1;

[0008] The powder solid phase system comprises a curing component, an X-ray radiopaque component, a filler, and an additive containing organobentonite; the organic liquid phase system comprises water, an organic solution, a stabilizer, and a wetting agent containing cetylsulfopropyl betaine;

[0009] The mass percentage of the organobentonite in the inorganic powder solid phase system is less than or equal to 1%; the mass percentage of the betaine in the organic liquid phase by volume is 0.01-1%.

[0010] As a preferred scheme, the mass ratio of the curing component, the X-ray radiopaque component, the filler, and the additive in the powder solid phase system is 30-55:24-50:1-5:1-10.

[0011] As a preferred scheme, the curing component is tricalcium silicate and / or dicalcium silicate. Further preferably, the curing component is tricalcium silicate and dicalcium silicate.

[0012] As a preferred scheme, the X-ray radiopaque component includes zirconia.

[0013] As a preferred scheme, the filler includes calcium hydroxide.

[0014] As a preferred scheme, the additive includes calcium carbonate, calcium hydroxide, barium sulfate, and organobentonite.

[0015] As a preferred embodiment, the average particle size of the curing component is 0.1 - 10 μm.

[0016] As a preferred embodiment, the average particle size of the X-ray radiopaque component is 0.02 - 5 μm.

[0017] As a preferred embodiment, the average particle size of the additive is 1 - 10 μm.

[0018] As a preferred embodiment, the powder solid phase system is composed of the following components in parts by mass: 1 - 5 parts of calcium carbonate, 1 - 5 parts of calcium hydroxide, 1 - 5 parts of barium sulfate, and 0.01 - 1 part of organic bentonite.

[0019] As a preferred embodiment, the organic solution is at least one of propylene glycol, polyethylene glycol, glycerol, silicone oil, and hydrogenated castor oil.

[0020] As a preferred embodiment, the stabilizer is at least one of xanthan gum, cellulose, sodium cellulose, and carbomer.

[0021] As a preferred embodiment, the wetting agent is cetylsulfopropyl betaine or a mixture of cetylsulfopropyl betaine and Tween.

[0022] As a preferred embodiment, the mass ratio of water, organic solution, stabilizer, and wetting agent containing cetylsulfopropyl betaine in the organic liquid phase system is 4 - 96:3 - 95:0.01 - 2:0.01 - 1.

[0023] The present invention also provides a preparation method of a high powder-liquid ratio and easy-flowable root canal filling paste. After mechanically activating the surface of the powder solid phase system, it is added to the organic liquid phase system, and then mixed evenly to obtain the paste.

[0024] As a preferred embodiment, the method of surface mechanical activation is wet ball milling, and the conditions are: the ball milling agent is absolute ethanol, the ball-to-material ratio is 5 - 9:1, the rotation speed is 400 - 800 r / min, and the time is 3 - 5 h.

[0025] As a preferred embodiment, the mixing method is ball milling and / or grinding.

[0026] As a preferred embodiment, the particle size of the mixed paste is 0.1 - 1 μm.

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

[0028] 1) The root canal filling paste provided by the present invention is based on the synergistic effect between organobentonite in the powder solid phase system and cetylsulfopropyl betaine in the organic liquid phase system. Without increasing the liquid phase content, it can play a good wetting role between the refined powders, thereby greatly increasing the powder-liquid ratio of the paste while also significantly improving the fluidity of the paste, effectively solving the technical problems of too fast curing reaction and easy cracking caused by excessive liquid phase content after powder refinement in the prior art, and can effectively fill the lateral root canals.

[0029] 2) In the preparation method provided by the present invention, first, the powder is refined into nanoscale by surface mechanical activation, which is easier to enter the lateral root canals in terms of size. Then, the organic liquid phase system is added and mixed evenly to increase the wettability of the paste to the root canals, and the powder accommodation capacity of the tough hydrogel per unit volume is improved by the coordination interaction between cellulose and bentonite, thereby endowing the paste with excellent fluidity and microscopic adhesion strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a picture of the paste obtained in Example 1 of the present invention filling the lateral root canals;

[0031] Figure 2 It is a photo of the fluidity test result of the paste obtained in Example 1 of the present invention;

[0032] Figure 3 It is a picture of the powder particle size of the paste obtained in Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0033] The present invention will be further described in detail below with reference to the drawings and embodiments. Through these descriptions, the features and advantages of the present invention will become clearer and more definite. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0034] Example 1

[0035] Calculated based on the total mass of the powder being 100, take the total content of tricalcium silicate and dicalcium silicate as 40 wt% (0.8 μm); the content of zirconia is 50 wt% (0.05 μm); calcium carbonate 2% (0.2 μm): calcium hydroxide 5% (0.2 μm): barium sulfate 2.5% (0.2 μm): organobentonite 0.5% (0.5 μm). Calculated based on the total mass of the liquid phase being 100, select water 10%, propylene glycol 10 wt%, polyethylene glycol 79.96%, hydroxypropyl methylcellulose 0.02%, and cetylsulfopropyl betaine 0.02%. First, prepare the mixed liquid according to the designed components; then, add the prepared powder to the mixed liquid at a mass ratio of the powder to the mixed liquid of 5.5:1, and mix them evenly by the method of stirring ball milling.

[0036] Example 2

[0037] This example is exactly the same as Example 1, except that: the content of cetylsulfopropyl betaine in the liquid phase system is increased to 1%; that is, based on the total mass of the liquid phase being 100, select 10% water, 10 wt% propylene glycol, 78.98% polyethylene glycol, 0.02% hydroxypropyl methylcellulose, and 1% cetylsulfopropyl betaine.

[0038] Example 3

[0039] This example is exactly the same as Example 2, except that: the content of organobentonite in the solid powder system is 1%, and at the same time the solid-liquid ratio is increased to 7:1. That is, based on the total mass of the powder being 100, take the total content of tricalcium silicate and dicalcium silicate as 40 wt% (0.8 μm); the content of zirconia is 49.5 wt% (0.05 μm); calcium carbonate 2% (0.2 μm): calcium hydroxide 5% (0.2 μm): barium sulfate 2.5% (0.2 μm): organobentonite 1% (0.5 μm).

[0040] Example 4

[0041] Based on the total mass of the powder being 100, take the total content of tricalcium silicate and dicalcium silicate as 50 wt% (0.8 μm); the content of zirconia is 35 wt% (0.05 μm); calcium carbonate 4% (0.2 μm): calcium hydroxide 5% (0.2 μm): barium sulfate 5% (0.2 μm): organobentonite 1% (0.5 μm). Based on the total mass of the liquid phase being 100, select 10% water, 10 wt% propylene glycol, 79.93% polyethylene glycol, 0.05% xanthan gum, and 0.02% cetylsulfopropyl betaine. First, prepare the mixed solution according to the designed components; then add the prepared powder to the mixed solution at a mass ratio of 6.5:1 of the powder to the mixed solution, and make it uniformly mixed by means of stirring and ball milling.

[0042] Comparative Example 1

[0043] This comparative example is exactly the same as Example 1, except that: no organobentonite and cetylsulfopropyl betaine are added.

[0044] Comparative Example 2

[0045] This comparative example is exactly the same as Example 1, except that: the average particle size of the tricalcium silicate and dicalcium silicate raw materials is 10 μm.

[0046] The present invention also tested the root canal fluidity and penetration depth of Examples 1 to 4 and Comparative Examples 1 and 2. The test results are shown in Table 1, and the test process is as follows:

[0047] The obtained paste was tested for fluidity according to the method in 7.2 of the YY0717-2009 standard, and the diameter of the test piece was 25 mm. See the physical picture of the test for Figure 1 . The laser confocal test method was used to test the depth of penetration into the root canal. The test method was as follows: Extracted premolars (single root canal) were selected, the crown part was removed, and a standard apical length of 15 mm was obtained. The pulp was removed with a pulp extirpator, the root canal was prepared, and finally the root canal was irrigated alternately with 5 mL of 17% EDTA and 10 mL of 5% NaOCl to remove the smear layer, and finally the root canal was irrigated with 5 mL of DW. The processed extracted teeth were stored in distilled water for later use. Before filling, the inner wall of the root canal was dried with absorbent paper points. The paste in the root canal was first mixed with 0.1% rhodamine b as a fluorescent tracer. The paste was filled into the root canal, and the filler was compacted with a flat head pressure filling instrument. After filling tightly, the coronal part of the root canal orifice was sealed with light-curing resin. All samples were stored in SBF solution at 37 °C and 100% relative humidity for 14 d. After 14 d, the samples were taken out, the experimental samples were marked at 5 mm from the root apex, and cut perpendicularly to the long axis of the extracted tooth with a low-speed diamond saw at the marked point, with a thickness of about 1 mm. Then the cut samples were rinsed in 17% EDTA and 5% NaOCl for 2 min in sequence, ultrasonically cleaned in distilled water for 5 min, and blotted dry with absorbent paper. Subsequently, the sections were fixed on glass slides and scanned with a laser confocal scanning electron microscope (the maximum absorption wavelength and emission wavelength were 488 / 525 nm). The taken pictures were calibrated with Image J software and then analyzed to measure the maximum penetration depth of the paste at 5 mm from the root apex.

[0048] Table 1

[0049]

Claims

1. A high powder-liquid ratio and easily flowable root canal filling paste, characterized in that: The paste contains a powder solid phase system and an organic liquid phase system, and the powder-liquid ratio is 5-7:1; The powder solid phase system contains a curing component, an X-ray radiopaque component, a filler, and an additive containing organic bentonite; the organic liquid phase system contains water, an organic solution, a stabilizer, and a wetting agent containing cetylsulfopropyl betaine; The mass percentage of the organic bentonite in the inorganic powder solid phase system is less than or equal to 1%; the mass percentage of the betaine in the organic liquid phase is 0.01-1%.

2. The highly flowable root canal filling paste with a high powder-liquid ratio according to claim 1, characterized in that: In the powder solid phase system, the mass ratio of the curing component, the X-ray radiopaque component, the filler, and the additive is 30-55:24-50:1-5:1-10.

3. A highly flowable root canal filling paste with a high powder-liquid ratio according to claim 1, characterized in that: The curing component is tricalcium silicate and / or dicalcium silicate; the X-ray radiopaque component includes zirconia; the filler includes calcium hydroxide; the additive includes calcium carbonate, calcium hydroxide, barium sulfate, and organic bentonite.

4. A highly flowable root canal filling paste with a high powder-liquid ratio according to claim 1, characterized in that: The average particle size of the curing component is 0.1-10 μm; the average particle size of the X-ray radiopaque component is 0.02-5 μm; the average particle size of the additive is 1-10 μm.

5. A highly flowable root canal filling paste with a high powder-liquid ratio according to claim 1, characterized in that: The powder solid phase system is composed of the following components in parts by mass: 1-5 parts of calcium carbonate, 1-5 parts of calcium hydroxide, 1-5 parts of barium sulfate, and 0.01-1 part of organic bentonite.

6. The highly flowable root canal filling paste with a high powder-liquid ratio according to claim 1, characterized in that: The organic solution is at least one of propylene glycol, polyethylene glycol, glycerol, silicone oil, and hydrogenated castor oil; the stabilizer is at least one of xanthan gum, cellulose, sodium cellulose, and carbomer; the wetting agent is cetylsulfopropyl betaine or a mixture of cetylsulfopropyl betaine and tween.

7. A highly flowable root canal filling paste with a high powder-liquid ratio according to claim 1, characterized in that: In the organic liquid phase system, the mass ratio of water, the organic solution, the stabilizer, and the wetting agent containing cetylsulfopropyl betaine is 4-96:3-95:0.01-2:0.01-1.

8. A method for preparing a highly flowable root canal filling paste with a high powder-liquid ratio according to any one of claims 1 to 7, characterized in that: After the surface of the powder solid phase system is mechanically activated, it is added to the organic liquid phase system, and then mixed evenly to obtain the paste.

9. The preparation method of a highly flowable root canal filling paste with a high powder-liquid ratio according to claim 8, characterized in that: The method of the surface mechanical activation is wet ball milling, and the conditions are: the ball milling agent is anhydrous ethanol, the ball-to-material ratio is 5-9:1, the rotation speed is 400-800 r / min, and the time is 3-5 h.

10. The preparation method of a highly flowable root canal filling paste with a high powder-liquid ratio according to claim 8, characterized in that: The mixing method is ball milling and / or grinding; the particle size of the mixed paste is 0.1-1 μm.

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