DENTAL PRODUCT FOR THE PRODUCTION OF ENDODONTIC CEMENT

Description

Technical Field

[0001] The invention relates to a dental product enabling the formation of an endodontic cement, or root canal sealing cement, in the presence of moisture in a dental canal. The cement formed is capable of undergoing an easy reworking operation, for example by the application of ultrasound. Prior art

[0002] Endodontic treatment is a delicate intervention on which periodontal health and the sustainability of the dental organ 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 pathological tooth into a healthy, asymptomatic and functional entity on the arch.

[0003] Root canal or endodontic treatment is indicated in the case 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 case of a living pulp if the prognosis for pulp vitality is unfavorable, if there is a root amputation or hemisection and if the probability of pulp exposure during the coronal restoration not allowing direct capping is high.

[0004] Pulp inflammation and infection can be due to multiple causes such as cavities, cracks, fractures or dental shock. If the infected or inflamed pulp is not treated, it can cause significant pain and even lead to an abscess. Endodontic treatment consists of preventing or eliminating the infection, by eliminating bacteria and their toxins from the root canal system, but also all residues likely to serve as nutrients and support for bacterial multiplication. In order to maintain this disinfection, the pulp or what remains of it, in a healthy root canal system, must be replaced with a watertight filling, promoting healing. This procedure allows the elimination and neutralization of organic and bacterial substances that cause irritation of the periapical tissues. The result must be stable and durable. Once reconstituted, the tooth must be functional, asymptomatic and show no clinical signs.

[0005] The use of root canal sealing cements is known, which are well tolerated and have good resistance. However, the operation of reprocessing the dental cement previously placed in case of need for resumption of endodontic treatment, for example to restore the cement, can be delicate. It may, in fact, be necessary to use solvents, potentially toxic, to reduce the hardness of the cements at the canal level for the resumption operation. WO 2008 / 102214 is known, which discloses an endodontic filling material composed of a mixture of Calcium Phosphate powders, Calcium Silicate and Calcium salts in an aqueous solution.

[0006] It is desirable to have dental products for the formation of an endodontic cement that produces the desired root canal filling while making a revision operation easier. Statement of the invention

[0007] The invention relates to a dental product intended to form an endodontic cement in a dental canal, said product comprising at least: a powdery composition with a mass content of between 40% and 55% comprising at least one calcium phosphate and capable of forming hydroxyapatite in the presence of moisture, a binder with a mass content of between 0.5% and 5%, and a liquid medium with a mass content of between 30% and 50%.

[0008] The particular composition of the dental product described above gives several advantages to the endodontic cement obtained.

[0009] Indeed, this cement is biocompatible and non-irritating. It is based on hydroxyapatite, which is the major constituent of dentin, and its setting occurs naturally by bringing the product into contact with canal moisture. The cement obtained also has sufficient cohesion to provide the desired hold without it being too strong for easy and safe reworking, for example with an ultrasonic tip, to be possible. Thus, the cement advantageously has a compressive strength of between 3 MPa and 15 MPa, for example between 3 MPa and 10 MPa. The viscosity of the product is also limited so that it can be easily introduced into the dental canal without the formation of air bubbles. Thus, the dynamic viscosity of the product is advantageously less than or equal to 240 Pa.s, for example less than or equal to 200 Pa.s, for example less than or equal to 150 Pa.s.Viscosity can be determined by a plane-plane rheometer, for example marketed under the reference "Discovery HR-2" from the company TA instruments, at 20°C. A "flow ramp" method of 0.01 to 10 s -1< and a "flow sweep" method of 10 to 1.10 -6< s -1< can be used to measure the viscosity and the flow threshold of the dental product.

[0010] More specifically, the powder composition content is sufficient so that the compressive strength of the cement is sufficient to achieve the desired cohesion while remaining limited to allow the reworking operation and so that the product maintains a controlled viscosity. The liquid medium, present in the product in a significant content, also helps to limit the viscosity. The binder content is sufficient to help achieve the desired cohesion while remaining limited so as not to affect the viscosity.

[0011] It should be noted that the dental product having the composition described above corresponds to the 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 or in several separate parts, each in a separate compartment, intended to be mixed only at the time of use of the product, as will be described in more detail below. Unless otherwise stated, the contents of the constituents of the dental product are taken before introduction into the dental canal.

[0012] In an exemplary embodiment, the mass content of the powdery composition is between 43% and 52%.

[0013] Such a characteristic advantageously contributes to optimizing the compromise between the compressive strength of the cement and the viscosity of the product.

[0014] In one exemplary embodiment, the powdered composition comprises a mixture of dicalcium phosphate and tetracalcium phosphate.

[0015] In particular, the ratio of the mass of tetracalcium phosphate in the product to the mass of dicalcium phosphate in the product may be between 0.9 and 1.9.

[0016] In an exemplary embodiment, the powdery composition has an average grain size D50 less than or equal to 50 µm.

[0017] By "average size D50" we mean the dimension given by the statistical particle size distribution to half of the population.

[0018] The choice of fine grains for the powder composition helps to achieve improved cohesion and rapid setting of the cement in the dental canal. In one example, the mass content of the binder is between 0.5% and 3.5%.

[0019] Such a characteristic advantageously contributes to optimizing the compromise between the compressive strength of the cement and the viscosity of the product.

[0020] In an exemplary embodiment, the product further comprises a radiopaque contrast agent in a mass content of less than or equal to 15%.

[0021] The presence of the radiopaque contrast agent allows for monitoring and radiographic control of the cement during its placement. When present, its content must nevertheless remain limited so as not to alter the compressive strength of the cement by affecting the formation of the network by the calcium phosphates.

[0022] In an exemplary embodiment, the product further comprises a suspending agent in a mass content less than or equal to 1.5%.

[0023] The presence of the suspending agent prevents any risk of separation between the solid phase and the liquid phase in the product. When it is present, its content must nevertheless remain limited so as not to increase the viscosity of the product too much. In an exemplary embodiment, the product also comprises a cement setting accelerator with a mass content of less than or equal to 10%.

[0024] This compound helps accelerate the formation of cement. When present, its content must nevertheless remain limited so as not to increase the viscosity of the product too much.

[0025] In an exemplary embodiment, the product is such that: the mass content of powdered composition is between 43% and 52%, the mass content of binder is between 0.5% and 1%, the liquid medium is non-aqueous and its mass content is between 30% and 40%, the product comprises a radiopaque contrast agent in a mass content of between 5% and 15%, for example between 5% and 12%, and the product comprises a cement setting accelerator in a mass content of between 4% and 7%.

[0026] In particular, the radiopaque contrast agent may comprise barium sulfate and the mass content of powdered composition may be between 43% and 48%.

[0027] Alternatively, the radiopaque contrast agent may comprise zirconium oxide and the mass content of powder composition may be between 48% and 52%.

[0028] According to another embodiment, the product is such that: the mass content of powdered composition is between 43% and 52%, the mass content of binder is between 3% and 3.5%, the liquid medium comprises water and its mass content is between 30% and 40%, and the product comprises a radiopaque contrast agent in a mass content of between 5% and 15%.

[0029] The invention also relates to an assembly for filling and sealing a dental canal, comprising at least the product as described above in an introduction device capable of introducing the product into the dental canal.

[0030] The invention also relates to a method for placing an 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.

[0031] The invention also relates to a method for 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 tool vibrating at an ultrasonic frequency. Brief description of the drawings

[0032] [ Fig. 1 ] There figure 1 provides photographs of test specimens and models of teeth filled with different root canal cements. Fig. 2 ] There figure 2 provides photographs of tooth models after root canal cement retreatment. Description of the embodiments

[0033] The dental product is in fluid form and comprises at least the powder composition and the binder in the liquid medium. The dental product may be in the form of a suspension. The dental product is intended to be introduced into a dental canal to form an endodontic cement for filling and sealing this canal. The dynamic viscosity of the dental product may be between 90 Pa.s and 240 Pa.s, for example between 90 Pa.s and 200 Pa.s, or even between 90 Pa.s and 150 Pa.s. As indicated above, the compressive strength of the cement obtained may be between 3 MPa and 15 MPa, for example between 3 MPa and 10 MPa.

[0034] The compressive strength of the cement can be measured by implementing the operating protocol described below. A plaster of Paris mold 6 mm in diameter and 10 mm in height allowing water exchange was filled with the dental product using a spatula, taking care not to leave air bubbles. The filled mold was placed in an oven at 40°C and high relative humidity for 3 days. After 3 days, the endodontic cement specimen was removed from the mold, taking care not to damage it by subjecting it to excessive forces. The specimen was then subjected to a compressive strength test using the universal testing machine marketed under the reference AGS-X by SHIMADZU, equipped with the 500 N or 10 kN cell, the mobile support and the P / 25 mobile. A test speed of 0.750 mm / minute was imposed during the compression test until the specimen ruptured.The compressive strength Rc is then determined using the following formula where Fmax denotes the force applied just before the specimen ruptures and d the initial diameter of the specimen. Rc = Fmax π × d 2 / 4

[0035] The following section focuses on providing more details on the different components of the dental product. The different characteristics described below can be taken in isolation or combined with each other.

[0036] The dental product comprises a powdery composition which is capable of forming hydroxyapatite Ca 10 (PO 4 ) 6 (OH) 2 in the presence of moisture, in particular in contact with the moisture present in the dental canal into which the product is introduced, in order to form the dental cement.

[0037] The powder composition comprises at least one calcium phosphate and may, in one example, comprise a mixture of an acidic calcium phosphate and a basic calcium phosphate which are capable of reacting in the presence of moisture to form hydroxyapatite. In this case, the acidic and basic calcium phosphates are each in the form of a powder.

[0038] The formation of hydroxyapatite from at least one calcium phosphate is known per se. Mention may be made of the use of a mixture of dicalcium phosphate, which may be anhydrous of formula CaHPO 4 or dihydrate of formula CaHPO 4 , 2 H 2 O, and tetracalcium phosphate of formula Ca 4 (PO 4 ) 2 O. Dicalcium phosphate is an acidic calcium phosphate and tetracalcium phosphate is a basic calcium phosphate. It is also possible to use a powdery composition comprising a mixture of a calcium phosphate, such as dicalcium phosphate dihydrate, with calcium carbonate or calcium hydroxide. However, within the scope of the invention, a powdery composition comprising, for example consisting essentially of, a mixture of an acidic calcium phosphate, such as dicalcium phosphate, and a basic calcium phosphate, such as tetracalcium phosphate, will preferably be used.For example, an equimolar mixture of dicalcium phosphate and tetracalcium phosphate can be used, which react in the presence of moisture to form hydroxyapatite. The powder composition may, for example, be free of calcium carbonate, calcium hydroxide or tricalcium silicate.

[0039] The average grain size D50 of the powder composition may be less than or equal to 50 µm, as indicated above. According to one example, when using a mixture of acidic calcium phosphate and basic calcium phosphate, the average grain size D50 of the basic calcium phosphate may be less than or equal to 10 µm. Such a characteristic advantageously contributes to accelerating the setting of the cement. As indicated above, the powder composition is present in the dental product in a mass content of between 40% and 55%, for example between 43% and 52%, for example between 45% and 50%. In the case where the powder composition comprises a mixture of dicalcium phosphate and tetracalcium phosphate, the mass ratio [mass of tetracalcium phosphate in the product] / [mass of dicalcium phosphate in the product] may be between 0.9 and 1.9.

[0040] The dental product comprises a liquid medium in which the powder composition and the binder are present. The liquid medium may comprise at least one of the following compounds: glycerol, propylene glycol, water and mixtures thereof. The liquid medium may be non-aqueous or, alternatively, comprise water. It has been indicated above that the dental product may be packaged in a single composition comprising all of its constituents before use. In this case, the use of a non-aqueous liquid medium will be preferred in order to avoid the formation of hydroxyapatite before use. According to a variant, the product is packaged in several separate parts, each in a separate compartment, intended to be mixed only at the time of use of the product.In this case, it is possible, for example, to have a powder composition comprising a mixture of an acidic calcium phosphate and a basic calcium phosphate and to condition the acidic calcium phosphate in a first compartment and the basic calcium phosphate in a second compartment, separate from the first compartment. In this case, water can be used in the first compartment and / or the second compartment, given that before use the acidic and basic calcium phosphates are separated and are not able to react to form hydroxyapatite. As indicated above, the liquid medium is present in the dental product in a mass content of between 30% and 50%, for example between 30% and 40%.

[0041] The dental product further comprises a binder which is formed from a compound distinct from that or those forming the powdery composition. According to one example, the binder may be chosen from: carboxymethylcellulose, polyvinylpyrrolidone, and mixtures of these compounds. For example, the product marketed under the reference Kollidon ®< 90 F by the company BASF may be used. As indicated above, the binder is present in the dental product in a mass content of between 0.5% and 5%, for example between 0.5% and 3.5%. More particularly in the case where the liquid medium comprises water, the mass content of binder in the dental product may be between 3% and 5%, for example between 3% and 3.5%. Alternatively, when the liquid medium is non-aqueous, the mass content of binder in the dental product may be between 0.5% and 1%.

[0042] As indicated above, the dental product may include other constituents in the liquid medium in addition to the powder composition and the binder. These additional constituents, if any, are described below.

[0043] The dental product may further comprise a radiopaque contrast agent which may be chosen from: barium sulfate, zirconium oxide, or mixtures of these compounds. The radiopaque contrast agent may be present in the dental product in a mass content of less than or equal to 15%, for example between 5% and 14%, for example between 5% and 12%.

[0044] As indicated above, the dental product may also contain a suspending agent. The suspending agent may contain silica. For example, the product marketed under the reference Aerosil ®< 200 by the company Evonik may be used. The suspending agent may be present in the dental product in a mass content of less than or equal to 1.5%, for example less than or equal to 1%. This content 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%.

[0045] As indicated above, the dental product may further comprise a cement setting accelerator. The setting accelerator may be hydroxyapatite, sodium phosphate, or a mixture of these compounds. The setting accelerator may be present in the dental product in a mass content of less than or equal to 10%, for example less than or equal to 7% or less than or equal to 6%. This content may be between 4% and 10%, for example between 4% and 7%, for example between 5% and 6%.

[0046] The dental product may further comprise at least one preservative. The preservative may be present in the dental product in a mass content less than or equal to 1.5%, for example less than or equal to 1%. This mass content may be between 0.15% and 1.5%, for example between 0.15% and 1%, or between 0.5% and 1.5%, for example between 0.5% and 1%. The preservative allows the stability of the dental product over time and may be chosen from: methyl paraben, propyl paraben, chlorhexidine, and mixtures of these compounds. The dental product may comprise at least one dental treatment agent, for example a therapeutic agent, such as at least one of an antiseptic or an anti-inflammatory. The antiseptic agent may be chosen from chlorhexidine hydrochloride, chlorhexidine dihydrochloride, chlorhexidine gluconate, chlorhexidine digluconate, sodium hypochlorite, quaternary ammoniums, iodine derivatives or mixtures thereof.The antiseptic agent may in particular comprise chlorhexidine gluconate or chlorhexidine digluconate. The anti-inflammatory agent may be chosen from butoform, prednisolone acetate, β-glycyrrhetinic acid, a non-steroidal anti-inflammatory drug or mixtures thereof.

[0047] Various details relating to the composition of the dental product have just been described. The following provides details on the use of this product to form dental cement and carry out its reprocessing.

[0048] The dental product may be packaged in a single composition comprising all of its constituents before use or in several separate parts, each in a separate compartment, intended to be mixed only at the time of use of the dental product, for example with separation of the acid and basic calcium phosphates.

[0049] The introduction device for introducing the dental product into the root canal may be a single or double compartment syringe with specific tips for filling the canal. Such an introduction device is known per se and as an example of a usable introduction device, we can cite the tool marketed under the reference Colibri ™< by the company Sulzer Mixpac ™< (double compartment example). Once introduced into the root canal, the dental product hardens on contact with moisture in the canal in order to form hydroxyapatite and thus achieve obturation and sealing of the root canal.

[0050] The cement has a moderate hardness allowing it to be easily reworked, for example, for carrying out a dental cement restoration operation. The cement can be removed in whole or in part from the canal by contact with a tool vibrating at an ultrasonic frequency, for example an ultrasonic tip. The vibration frequency of the tool can be between 26 kHz and 36 kHz. The tool vibrating at an ultrasonic frequency is known per se and, as an example of a usable tool, we can cite the insert No. ET25S marketed by the company SATELEC. Examples

[0051] The table below provides three examples of dental product formulations according to the invention that have been prepared.

[0052] The constituents of Formulas A and B were packaged in the same composition prior to use, whereas dicalcium phosphate dihydrate (DCPD) and tetracalcium phosphate (TTCP) were packaged in two separate compartments for Formula C with a 1:1 distribution of the contents of these compartments at the time of use to form the dental product of Formula C. The compositions in each of these two compartments are provided below. [Table 3] Components Mass percentage Propylene glycol 32,25% TTCP 65,00% Kollidon 90F 0,75% Aerosil 200 1,00% Chlorhexidine 1,00%

[0053] The radiopaque contrast agent was barium sulfate in formulas A and C and zirconium oxide in formula B. The average D50 grain size of DCPD was 10 µm (9.213 µm measured by laser granulometer) and the average D50 grain size of TTCP was less than 10 µm in each of the formulas.

[0054] In a humid environment, formula A produced a cement with a compressive strength of 3.27 MPa (the viscosity of formula A was 98.2613 Pa.s), formula B a cement with a compressive strength of 6.23 MPa (the viscosity of formula B was 142.127 Pa.s) and formula C a cement with a compressive strength of 4.34 MPa (the viscosity of formula C was 93.2593 Pa.s).

[0055] The performance of the cements obtained within the framework of the invention was evaluated in blind reprocessing tests on specimens and FKG tooth models filled with different sealing materials.

[0056] Formula B above (B in photographs) and Formula A above (C in photographs) were tested against other commercial sealants: Total Fill BC Sealer (A in photographs), MTA Caps (D in photographs) and MTA Flow Extended Work Time (EWT in photographs).

[0057] Before the degradation test, the setting of the sealing materials was checked by applying pressure on the top. All materials were hard and appeared to be fully set. The degradation tests were carried out using the Newtron P5XS ultrasonic generator at power 10 (maximum power in the endodontic range) and the ET25S tip, dedicated to resuming treatment in the coronal third and isthmuses.

[0058] During the degradation tests on the specimens, the following observations were made: the “Total Fill BC Sealer” cement is easily degraded using ultrasound, it even seems to be dissolved upon contact with water (whitish color of the water after reprocessing); the cements obtained from the formulas according to the invention are, like “Total Fill BC Sealer”, easily degraded using ultrasound. It also seems that dissolution is present but to a lesser extent than for “Total Fill BC Sealer”; the “MTA Flow EWT” cement is easily degraded using ultrasound. However, it is not dissolved upon contact with water; the “MTA Caps” cement is more difficult to degrade than the other test pieces and shows greater resistance. In addition, the sealing material blackens upon prolonged contact with ultrasound.

[0059] During the degradation tests of the different sealing materials on FKG tooth models, more visible differences appeared. Indeed, on deeper and narrower areas, the root canal sealing cement "Total Fill BC Sealer" shows greater resistance than in the test specimen. The degradation of the sealing material is possible little by little because it is impossible to insert the insert deeply into the canals. Some parts even seem more difficult to degrade and require a prolonged contact time with ultrasound. It is noted that with this sealing material, resumption of treatment is difficult in limited accesses such as narrow canals.

[0060] The cements obtained within the framework of the invention have reduced resistance compared to "Total Fill BC Sealer". Indeed, in contact with ultrasound, it is very easy to degrade the entire cement, even in limited access. It was also noted during this test that the formula containing zirconium oxide has slightly greater resistance than the formula containing barium sulfate.

[0061] The resumption of root canal treatment using ultrasound is facilitated in the presence of the formulas according to the invention compared to existing sealing materials.

[0062] The expression "between ... and ..." must be understood as including the limits.

Claims

1. A dental product for forming an endodontic cement in a dental canal, said product comprising at least: - a powder composition in a mass content comprised between 40% and 55% comprising at least one calcium phosphate and able to form hydroxyapatite in the presence of moisture, - a binder in a mass content comprised between 0.5% and 5%, and - a liquid medium in a mass content comprised between 30% and 50%.

2. The product as claimed in claim 1, wherein the mass content of the powder composition is comprised between 43% and 52%.

3. The product as claimed in claim 1 or 2, wherein the powder composition comprises a mixture of dicalcium phosphate and tetracalcium phosphate.

4. The product as claimed in any one of claims 1 to 3, wherein the powder composition has an average particle size D50 of less than or equal to 50 µm.

5. The product as claimed in any one of claims 1 to 4, wherein the mass content of the binder is comprised between 0.5% and 3.5%.

6. The product as claimed in any one of claims 1 to 5, further comprising a radiopaque contrast agent in a mass content of less than or equal to 15%.

7. The product as claimed in any one of claims 1 to 6, further comprising a suspending agent in a mass content of less than or equal to 1.5%.

8. The product as claimed in any one of claims 1 to 7, further comprising a cement setting accelerator in a mass content of less than or equal to 10%.

9. The product as claimed in any one of claims 1 to 8, wherein: - the mass content of the powder composition is comprised between 43% and 52%, - the mass content of binder is comprised between 0.5% and 1%, - the liquid medium is non-aqueous and its mass content is comprised between 30% and 40%, - the product comprises a radiopaque contrast agent in a mass content comprised between 5% and 15%, and - the product comprises a cement setting accelerator in a mass content comprised between 4% and 7%.

10. The product as claimed in claim 9, wherein the radiopaque contrast agent comprises barium sulfate and wherein the mass content of the powder composition is comprised between 43% and 48%.

11. The product as claimed in claim 9, wherein the radiopaque contrast agent comprises zirconium oxide and wherein the mass content of the powder composition is comprised between 48% and 52%.

12. The product as claimed in any one of claims 1 to 8, wherein: - the mass content of the powder composition is comprised between 43% and 52%, - the mass content of binder is comprised between 3% and 3.5%, - the liquid medium comprises water and its mass content is comprised between 30% and 40%, and - the product comprises a radiopaque contrast agent in a mass content comprised between 5% and 15%.

13. A kit for filling and sealing a dental canal, comprising at least the product as claimed in any one of claims 1 to 12 in an introduction device suitable for introducing the product into the dental canal.