Dental product for forming an endodontic cement

Abstract

The invention relates to a dental product for forming an endodontic cement in a dental canal, said product comprising at least: - propylene glycol in an amount of greater than or equal to 20% by mass, - a mixture of dicalcium phosphate and tetracalcium phosphate capable of forming hydroxyapatite in the presence of moisture, this mixture being present in an amount of between 34% and 40% by mass, - a binder in an amount of between 1% and 4% by mass, - a radiopaque contrast agent made of zirconium oxide in an amount of greater than or equal to 20% by mass, and - potassium citrate in an amount of between 0.1% and 0.38% by mass.

Description

Description Title of the invention: Dental product for the formation of an endodontic cement Technical Field

[0001] This presentation concerns a dental product that enables the formation of an endodontic cement, or canal sealing cement, in the presence of moisture in a dental canal. Previous technique

[0002] Endodontic treatment is a delicate procedure upon which periodontal health and the longevity of the tooth depend. It consists of the prevention, diagnosis, and treatment of dental pulp and periapical infections (in the bone and around the roots) in order to transform a diseased tooth into a healthy, asymptomatic, and functional one in the dental arch.

[0003] Root canal or endodontic treatment is indicated in the context of irreversible pulpitis (inflammation, pulp infection) or necrotic pulp with or without clinical and / or radiographic signs of apical periodontitis (inflammatory lesions of the periodontium) or in the context of a living pulp if the prognosis of pulp vitality is unfavorable, if there is a root amputation or hemisection and if the probability of pulp exposure during coronal restoration not allowing direct capping is high.

[0004] Pulp inflammation and infection can be caused by a variety of factors, including cavities, cracks, fractures, or dental trauma. If an infected or inflamed pulp is left untreated, it can cause significant pain and even lead to an abscess. Endodontic treatment aims to prevent or eliminate infection by removing bacteria and their toxins from the root canal system, as well as any residue that could serve as nutrients and support bacterial growth. To maintain this disinfection, the pulp, or what remains of it, must be replaced in a healthy root canal system with a hermetic filling that promotes healing. This procedure eliminates and neutralizes organic and bacterial substances that irritate the periapical tissues. The result should be stable and long-lasting. Once Once restored, the tooth must be functional, asymptomatic, and show no clinical signs.

[0005] The use of well-tolerated and durable root canal sealing cements is well-known. Furthermore, the commercially available sealant material, "Total Fill®", is known for its high radiopacity, allowing for easy radiographic monitoring and control of the cement during placement. FR3116713, which describes a dental product for the preparation of endodontic cement, and US2021298998 and US2020009021, which describe a dental composition and associated preparation process, are also known.

[0006] It is desirable to develop a new dental product with limited viscosity, designed to form an endodontic cement within a dental canal, that exhibits radiopacity similar to that of "Total Fill®", while offering satisfactory setting time and compressive strength, as well as preventing bacterial growth. It is also desirable that the formula be stable over time (no phase separation of the composition, or unwanted setting in the packaging before insertion into the dental canal), and that the resulting cement be relatively easy to process. Description of the invention

[0007] The present description relates, according to a first embodiment, to a dental product intended to form an endodontic cement in a dental canal, said product comprising at least: - propylene glycol in a mass content greater than or equal to 20%, - a mixture of dicalcium phosphate and tetracalcium phosphate suitable for forming Hydroxyapatite in the presence of moisture, this mixture being present in a mass content between 34% and 40%, - a binder with a mass content between 1% and 4%, - a radiopaque contrast agent of zirconium oxide in a mass content greater than or equal to 20%, and - potassium citrate in a mass content between 0.1% and 0.38%, for example between 0.2% and 0.3%.

[0008] The present description relates, according to a second embodiment, to a dental product intended to form an endodontic cement in a dental canal, said product comprising at least: - propylene glycol in a mass content greater than or equal to 20%, - a mixture of dicalcium phosphate and tetracalcium phosphate suitable for forming Hydroxyapatite in the presence of moisture, this mixture being present in a mass content between 34% and 43%, - a binder with a mass content between 0.3% and 1.3%, for example between 0.7% and 1.1%, - a radiopaque contrast agent of zirconium oxide in a mass content greater than or equal to 20%, and - an antiseptic agent comprising chlorhexidine in a mass content between 0.20% and 1.50%.

[0009] The inventors sought a dental product with radiopacity similar to that of "Total Fill®" and evaluated compositions with a significant radiopaque contrast agent content. Extensive optimization of the other product components was required to meet all the desired properties for this product with its high radiopaque agent content; namely, to ensure the resulting cement had satisfactory setting time and compressive strength, prevented bacterial growth, and maintained a limited viscosity.It was also sought to find formulas that were stable over time, particularly when packaged in syringes ("ready-to-use" packaging), that did not exhibit phase separation or undesired setting before insertion into the root canal, and cements with sufficient cohesion to provide the desired hold without being so strong as to hinder easy and safe revision, for example, using an ultrasonic tip. The specific compositions described in the first and second embodiments above are the result of this optimization work and exhibit these advantageous properties.

[0010] The choice of zirconium oxide for the radio-opaque contrast agent advantageously allows obtaining a product with limited viscosity, and significantly lower than that obtained if, for example, barium sulfate were used as a replacement.

[0011] The presence of propylene glycol at a concentration of at least 20% by mass also contributes to giving the product a satisfactory viscosity. Furthermore, replacing propylene glycol with another carrier such as glycerol results in a product that sets too quickly and has an excessively high viscosity. Generally, the dynamic viscosity of the product is advantageously less than or equal to 240 Pa·s, for example, less than or equal to 220 Pa·s.

[0012] Bacterial proliferation is prevented in the embodiments of the invention due to the significant propylene glycol content and the presence of a compound having a preservative effect, namely: potassium citrate in the first embodiment and The antiseptic agent containing chlorhexidine in the second embodiment. The reduced presence, or even absence, of water in the embodiments also helps to prevent this proliferation.

[0013] It should also be noted that the first embodiment does not require chlorhexidine due to the presence of potassium citrate, thus avoiding product classification that would delay market access for regulatory reasons. The inventors observed that removing the chlorhexidine-based antiseptic agent led to an acceleration of the cement setting time, which needed to be counteracted. The choice of potassium citrate resulted from a series of tests that also revealed that using different preservatives, instead of chlorhexidine, negatively affected at least one of the following: viscosity, setting time, or compressive strength.

[0014] The embodiments of the invention also have the advantage of forming a biocompatible and non-irritating cement. It is based on hydroxyapatite (Ca10CPCUXOH), which is the major constituent of dentin, and it sets naturally upon contact of the product with canal moisture.

[0015] Dicalcium phosphate and tetracalcium phosphate are capable of forming hydroxyapatite in the presence of moisture. They are each available in powder form. The formation of hydroxyapatite from these compounds is well-known. Dicalcium phosphate is an acidic calcium phosphate and can be anhydrous, with the formula CaHPO₄, or dihydrate, with the formula CaHPC₂·2H₂O. Tetracalcium phosphate is a basic calcium phosphate and has the formula CaPO₄O.

[0016] According to an example relating to the first embodiment, a ratio [amount of substance of dicalcium phosphate] / [amount of substance of tetracalcium phosphate] can be between 0.99 and 1.18.

[0017] According to an example relating to the second embodiment, a ratio [amount of substance of dicalcium phosphate] / [amount of substance of tetracalcium phosphate] can be between 1.13 and 1.16.

[0018] It should be noted that the dental product having the composition according to the embodiments above corresponds to a product ready to be introduced into the dental canal for cement formation. The product may be packaged in a single composition comprising all of its constituents before use, for example in a syringe. However, it does not depart from the scope of the invention if the product is packaged in several separate parts, each in a distinct compartment, intended to be mixed only with time of product use. Unless otherwise stated, the contents of the dental product constituents are taken before introduction into the dental canal.

[0019] According to an example of the first embodiment, propylene glycol is present in a mass content of between 20% and 26%, for example between 22% and 24%.

[0020] According to an example of the second embodiment, propylene glycol is present in a mass content of between 24% and 34%, for example between 24% and 30%, or even between 24% and 26%.

[0021] These propylene glycol contents in the first and second embodiments contribute advantageously to optimizing the viscosity of the product.

[0022] In one embodiment, the binder comprises carboxymethyl cellulose, polyvinylpyrrolidone, or a mixture of these compounds.

[0023] In particular, the binder can be an aqueous gel of carboxymethylcellulose and can be present in a mass content of between 2% and 5%, for example between 3% and 4%, the mass content of carboxymethylcellulose in the dental product being for example between 0.15% and 0.20%.

[0024] This characteristic contributes advantageously to optimizing product stability. The binder can be an aqueous gel of sodium carmellose.

[0025] In one embodiment, the radio-opaque zirconium oxide contrast agent is present in a mass content of between 25% and 35%, for example between 28% and 32%.

[0026] In one example, the dental product further includes Hydroxyapatite is present in a mass content of between 3% and 10%, for example between 3% and 7%.

[0027] Hydroxyapatite is a setting accelerator and contributes advantageously to optimizing the setting time of cement.

[0028] In one embodiment, the dental product further comprises a suspending agent.

[0029] The suspending agent plays a beneficial role in optimizing the stability of the dental product.

[0030] The suspending agent may contain silica. For example, the product marketed under the reference Aerosil® 200 by Evonik may be used. The suspending agent may be present in the dental product at a mass concentration of 1.5% or less, for example, 1% or less. This concentration may be between 0.25% and 1.5%, for example, between 0.25% and 1%, or between 0.5% and 1.5%, for example, between 0.5% and 1%.

[0031] According to an example relating to the second embodiment, the antiseptic agent may be selected from chlorhexidine hydrochloride, chlorhexidine dihydrochloride, chlorhexidine gluconate, chlorhexidine digluconate, or mixtures thereof. The antiseptic agent may, in particular, comprise chlorhexidine gluconate or chlorhexidine digluconate; in particular, it may be chlorhexidine digluconate.

[0032] According to an example relating to the first embodiment, the dental product comprises, for example essentially comprises, or even consists of: - propylene glycol in a mass content of between 20% and 26%, for example between 22% and 24%, - the mixture of dicalcium phosphate and tetracalcium phosphate capable of forming Hydroxyapatite in the presence of moisture, this mixture being present in a mass content between 35% and 37%, - the binder, which is an aqueous gel of carboxymethylcellulose and is present in a mass content of between 2% and 5%, for example between 3% and 4%, the mass content of carboxymethylcellulose in the dental product being, for example, between 0.15% and 0.20%, - a suspending agent in a mass concentration between 0.5% and 1.5%, - the radiopaque contrast agent zirconium oxide in a mass content between 28% and 32%, - of hydroxyapatite in a mass content of between 5% and 7%, and - potassium citrate in a mass content between 0.1% and 0.38%, for example between 0.2% and 0.3%.

[0033] According to an example relating to the second embodiment, the dental product comprises, for example essentially comprises, or even consists of: - propylene glycol in a mass content of between 24% and 30%, for example between 24% and 26%, - the mixture of dicalcium phosphate and tetracalcium phosphate capable of forming Hydroxyapatite in the presence of moisture, this mixture being present in a mass content between 35% and 40%, - the binder which includes polyvinylpyrrolidone and is present in a mass content of between 0.5% and 1%, - a suspending agent with a mass concentration between 0.25% and 0.75%, - the radiopaque contrast agent zirconium oxide in a mass content between 28% and 32%, - of hydroxyapatite in a mass content of between 3% and 5%, and - the antiseptic agent comprising chlorhexidine in a mass content of between 0.20% and 1.50%, for example between 0.50% and 1.50% or between 0.75% and 1.25%.

[0034] In one example, the total mass water content in the dental product may be less than or equal to 4%; in particular, the product may be water-free. This total water content includes water in all its forms, and therefore specifically any water that may be present in the aforementioned constituents.

[0035] The reduced water content helps to advantageously reduce the risk of bacterial proliferation.

[0036] In general, the product may be free of calcium carbonate, calcium hydroxide or tricalcium silicate.

[0037] The invention also relates to an assembly for the obturation and sealing of a dental canal, comprising at least one product as described above in an introduction device suitable for introducing the product into the dental canal.

[0038] The delivery device can be a single or double-compartment syringe with specific tips for filling the canal. Such a delivery device is well-known, and as an example of a usable delivery device, the tool marketed under the name Colibri™ by Sulzer Mixpac™ (double-compartment example) can be cited. Once introduced into the root canal, the dental product hardens upon contact with the moisture in the canal to form hydroxyapatite, thus obturation and sealing of the root canal.

[0039] The cement has a moderate hardness, allowing for easy removal, for example, during a dental cement restoration procedure. The cement can be removed, in whole or in part, from the canal by contact with a vibrating tool operating at an ultrasonic frequency, such as an ultrasonic tip. The vibration frequency of the tool can range from 26 kHz to 36 kHz. Ultrasonic vibrating tools are well-known, and as an example of a usable tool, we can mention the ET25S insert marketed by SATELEC.

[0040] Generally, dental products are in fluid form, and may be a suspension of solid particles in a liquid medium. The dental product is intended to be introduced into a dental canal to form an endodontic cement for filling and sealing that canal.

[0041] The invention also relates to a method for applying endodontic cement comprising at least: - the introduction of a dental product as described above into a dental canal, and - the setting of the dental product thus introduced in contact with the moisture present in the dental canal in order to form the endodontic cement.

[0042] The invention also relates to a method of treating an endodontic cement obtained from the dental product as described above and present in a dental canal in which said endodontic cement is brought into contact with a vibrating tool at an ultrasonic frequency. Brief description of the drawings [Fig. 1] Figure 1 is an X-ray of a dental canal filled with cement according to the invention. [Fig. 2] Figure 2 is an X-ray of a dental canal filled with cement obtained from the commercial product "Total Fill ®". [Fig. 3] Figure 3 provides a photograph of an ultrasonic tip reprocessing test of a cement according to the invention. [Fig. 4] Figure 4 provides a photograph of an ultrasonic tip reprocessing test of a cement according to the invention. [Fig. 5] Figure 5 provides a photograph of an ultrasonic tip reprocessing test of cement obtained from the commercial product "Total Fill ®". [Fig. 6] Figure 6 provides a photograph of an ultrasonic tip reprocessing test of cement obtained from the commercial product "Total Fill ®". Description of the implementation methods

[0043] The experimental section below demonstrates the advantages of the dental products according to the invention. It is preceded by a detailed description of the measurement protocols implemented for the various relevant parameters.

[0044] Viscosity measurement protocol

[0045] Generally, viscosity is evaluated using a 20 mm diameter aluminum planar rheometer, for example, the "Discovery HR-2" from TA Instruments, at 20°C. A flow ramp method can be used, with durations ranging from 0.01 to 10 s. -1 to measure viscosity.

[0046] Protocol for measuring the pH of unset cement

[0047] Generally, the measurement is carried out with a Metrohm 827 pH meter in a solution obtained by dissolving approximately 0.5 g of cement in 20 mL of distilled water, after magnetic stirring for a few minutes.

[0048] Setting time measurement protocol

[0049] In general, the setting time of cements is evaluated by depositing the product in a plaster of Paris mold hollowed out with an impression of 10 mm in diameter and 1 mm in height, the product is leveled and then placed in the oven at 40°C and high humidity.

[0050] At regular intervals, the mold is placed under a penetrometer equipped with a 4 mm diameter pin with a flat end. The pin is positioned so that it is flush with the surface of the cement, and the rod is released for 10 seconds. The resulting impression is then observed. The cement setting time is determined when no impression is visible after measurement.

[0051] Compression resistance measurement protocol

[0052] The compression force is measured using the AGS-X universal testing machine, marketed by SHIMADZU, equipped with a 500 N force cell and a P / 25 mobile.

[0053] The first step involves preparing the cement test specimens. The product is incorporated into split Teflon molds, 6 mm in diameter and 12 mm high, using a syringe fitted with a cannula, and then leveled. The molds are then placed in an oven at 40°C and high humidity until the cement has completely set. The test specimens are then carefully removed from the molds to avoid breakage.

[0054] Compression measurements are then performed using a compression test at a rate of 0.75 mm / min. The maximum force applied at the moment of failure is measured, and the stress, or compressive strength, is determined using the following formula: [Math. 1]

[0055] Example 1: Dental product Al according to the invention without chlorhexidine, comprising potassium citrate

[0056] The table below provides the formulation of the dental product Al according to the invention that was prepared. In the tables provided below, DCPD denotes phosphate dicalcium dihydrate, and TTCP tetracalcium phosphate. In this formula, potassium citrate is incorporated as a 2M aqueous solution; the mass content of potassium citrate (excluding water) in this composition is approximately 0.24%.

[0057] [Table 1]

[0058] The following characterizations were obtained for the Al product. The Al product exhibits limited viscosity and the resulting cement has satisfactory setting time and compressive strength.

[0059] [Table 2]

[0060] Furthermore, the inventors did not observe any sedimentation (phase separation) or syringe collection phenomenon for this product.

[0061] Example 2 (comparative): Dental product A21 outside the scope of the invention, without chlorhexidine, comprising calcium hydroxide

[0062] Calcium hydroxide possesses antibacterial activity, and its use has been evaluated with the aim of developing a chlorhexidine-free product. The table below provides the formulation of the comparative dental product A21 based on calcium hydroxide that was prepared.

[0063] [Table 3]

[0064] Product A21 exhibits an insufficient compressive strength of 0.7 MPa. The cement's setting reaction is an acid-base reaction, and since calcium hydroxide is a strong base, the reaction is disrupted.

[0065] Example 3 (comparative): Dental product A22 outside the scope of the invention, without chlorhexidine, comprising qlvcerol

[0066] Glycerol acts as a preservative, and its use has been evaluated as a replacement for propylene glycol, with the aim of developing a chlorhexidine-free product. The table below provides the formulation of the comparative glycerol-based dental product A22 that was prepared.

[0067] [Table 4]

[0068] The A22 product has a very fast setting time, less than 1h30, and a very high viscosity of 648 Pa.s.

[0069] In order to slow down the setting of the cement and decrease the viscosity of the mixture, the inventors carried out additional tests, removing hydroxyapatite from the formula and... Increasing either the amount of zirconium oxide or the TTCP / DCPD quantities did not yield satisfactory results. Further tests were also conducted by modifying the Kollidon 90F content and increasing the glycerol content, but the cements exhibited excessive viscosity and set in syringes at 40°C in less than 7 days.

[0070] Example 4 [comparative]: Dental products A23-1 and A23-2 outside the invention, without chlorhexidine, comprising sodium citrate

[0071] Sodium citrate acts as a preservative, and its use was evaluated with the aim of developing a chlorhexidine-free product. The table below provides the formulations of the sodium citrate-based dental products A23-1 and A23-2 that were prepared.

[0072] [Table 5]

[0073] Both cements set in an oven at 40°C in 2 days for the 3% cement and in 7 days for the 1% cement. The combined products are therefore not sufficiently stable over time.

[0074] Example 5 [comparative]: Dental product A24 outside the invention, without chlorhexidine, comprising citric acid

[0075] Citric acid acts as a preservative, and its use was evaluated with the aim of developing a chlorhexidine-free product. The table below provides the formulation of the citric acid-based dental product A24 that was prepared.

[0076] [Table 6]

[0077] Formula A24, packaged in a syringe and placed in an oven at 40°C, took 6 days. Therefore, the product is not sufficiently stable over time. Example 6: Dental product B according to the invention with chlorhexidine

[0078] The table below provides the formulation of dental product B according to the invention which was prepared.

[0079] [Table 7]

[0080] The following characterizations were obtained for product B. Product B exhibits limited viscosity and the resulting cement has satisfactory setting time and compressive strength.

[0081] [Table 8]

[0082] Furthermore, the inventors did not observe any sedimentation (phase separation) or syringe collection phenomenon for this product.

[0083] Furthermore, Figure 1 shows the radio-opacity obtained with product B due to the high zirconium oxide content used; this radio-opacity is comparable to that obtained with the commercial product "Total Fill ®" shown in Figure 2. The ultrasonic tip reprocessing test was conclusive for product B (Figures 3 and 4), while the product "Total Fill ®" presents a more difficult reprocessing (Figures 5 and 6).

[0084] Furthermore, for comparison, replacing zirconium oxide in formula B above with barium sulfate resulted in a product with a much higher viscosity of 703.6 Pa.s.

[0085] Although the present invention has been described with reference to specific embodiments, it is evident that modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various embodiments illustrated / mentioned can be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

[0086] The expression "between ... and ..." should be understood as including the boundaries.

Claims

Demands

1. A dental product intended to form an endodontic cement in a dental canal, said product comprising at least: - propylene glycol in a mass content greater than or equal to 20%, - a mixture of dicalcium phosphate and tetracalcium phosphate suitable for forming Hydroxyapatite in the presence of moisture, this mixture being present in a mass content between 34% and 40%, - a binder with a mass content between 1% and 4%, - a radiopaque contrast agent of zirconium oxide in a mass content greater than or equal to 20%, and - potassium citrate in a mass content between 0.1% and 0.38%.

2. A dental product intended to form an endodontic cement in a dental canal, said product comprising at least: - propylene glycol in a mass content greater than or equal to 20%, - a mixture of dicalcium phosphate and tetracalcium phosphate suitable for forming Hydroxyapatite in the presence of moisture, this mixture being present in a mass content between 34% and 43%, - a binder with a mass content between 0.3% and 1.3%, - a radiopaque contrast agent of zirconium oxide in a mass content greater than or equal to 20%, and - an antiseptic agent comprising chlorhexidine in a mass content between 0.20% and 1.50%.

3. Dental product according to claim 1, wherein propylene glycol is present in a mass content of between 20% and 26%.

4. Dental product according to claim 2, wherein propylene glycol is present in a mass content of between 24% and 34%.

5. Dental product according to any one of claims 1 to 4, wherein the binder comprises carboxymethyl cellulose, polyvinylpyrrolidone, or a mixture of these compounds.

6. Dental product according to claim 5, wherein the binder is an aqueous gel of carboxymethylcellulose and is present in a mass content of between 2% and 5%.

7. Dental product according to any one of claims 1 to 6, wherein the radio-opaque contrast agent zirconium oxide is present in a mass content of between 25% and 35%.

8. Dental product according to any one of claims 1 to 7, wherein the dental product further comprises hydroxyapatite present in a mass content of between 3% and 10%.

9. Dental product according to any one of claims 1 to 8, wherein the dental product further comprises a suspending agent.

10. A dental product according to any one of claims 1, 3 and 5 to 9 related to claim 1, wherein the dental product comprises: - propylene glycol in a mass content between 20% and 26%, - the mixture of dicalcium phosphate and tetracalcium phosphate capable of forming hydroxyapatite in the presence of moisture, this mixture being present in a mass content of between 35% and 37%, - the binder, which is an aqueous gel of carboxymethylcellulose and is present in a mass content of between 2% and 5%, - a suspending agent in a mass concentration between 0.5% and 1.5%, - the radiopaque contrast agent zirconium oxide in a mass content between 28% and 32%, - hydroxyapatite in a mass content of between 5% and 7%, and - potassium citrate in a mass content between 0.1% and 0.38%.

11. A dental product according to any one of claims 2, 4 and 5 to 9 related to claim 2, wherein the dental product comprises: - propylene glycol in a mass content between 24% and 34%, - the mixture of dicalcium phosphate and tetracalcium phosphate capable of forming hydroxyapatite in the presence of moisture, this mixture being present in a mass content of between 35% and 40%, - the binder which includes polyvinylpyrrolidone and is present in a mass content of between 0.5% and 1%, - a suspending agent with a mass concentration between 0.25% and 0.75%, - the radiopaque contrast agent zirconium oxide in a mass content between 28% and 32%, - of hydroxyapatite in a mass content of between 3% and 5%, and - the antiseptic agent comprising chlorhexidine in a mass content of between 0.20% and 1.50%.

12. Assembly for obturating and sealing a dental canal, comprising at least one product according to any one of claims 1 to 11 in an introduction device suitable for introducing the product into the dental canal.

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