RU2772782C2 - Dental adhesive - Google Patents

Abstract

FIELD: dentistry.

SUBSTANCE: group of inventions relates to dental adhesive and a method for unsticking polymerized dental adhesive. The proposed dental adhesive contains at least one polymerizable monomer, a polymerization initiator and thermally expandable particles containing a shell encapsulating an expanding additive, while shells of thermally expandable particles are made of copolymer of acrylonitrile and methyl methacrylate. The mass content of thermally expandable particles ranges from 10% to 45%. A method is also proposed for unsticking the above-mentioned polymerized dental adhesive attached to the tooth surface, where the mentioned polymerized adhesive contains at least resin and thermally expandable particles having a shell made of copolymer of acrylonitrile and methyl methacrylate, and an encapsulating expanding additive, where polymerized adhesive is unsticked by exposing it to ultrasonic vibrations.

EFFECT: use of the claimed dental adhesive makes it possible to unstick polymerized adhesive at the end of treatment in a way that is simpler and more comfortable for a patient, in particular, as a result of reducing the risk of burns and damage to dental tissue.

8 cl, 1 tbl, 9 dwg, 1 ex

Description

State of the art

Orthodontic adhesives are intended to attach an orthodontic appliance to the surface of a tooth.

Orthodontic adhesives typically contain one or more polymerizable monomers of the acrylate or methacrylate type, together with a polymerization initiator.

The orthodontic appliance is permanently attached to the tooth by stimulating the polymerization of the monomers present in the adhesive, for example by blue light irradiation.

Immediately after orthodontic treatment, the orthodontic appliance must be removed from the tooth surface.

To accomplish this, the appliance can be removed mechanically using dental forceps designed for this purpose. This method is relatively crude and can lead to enamel lesions. The use of dental forceps can be painful or even traumatic for the patient. The adhesive is not necessarily completely removed and residues may remain on the teeth, thus requiring the use of a dental burr to remove them. This treatment can also lead to additional damage to the enamel.

To avoid the use of this mechanical method of peeling (peeling off) an orthodontic appliance, JP 2007/320929 proposes an orthodontic adhesive that includes thermally expandable particles. Each thermally expandable particle is in the form of a shell encapsulating an expanding additive such as butane. Under the effect of increasing temperature, the expansion agent contained in the shell expands, thereby stimulating the expansion of the shell and the increase in particle volume.

JP 2007/320929 proposes to carry out the peeling no longer with dental forceps, but by heating the adhesive to a temperature that is relatively high in order to expand the thermally expandable particles, thereby stimulating the degradation of the polymeric framework. However, the use of a relatively high temperature heating element may result in discomfort and even a risk of burns to the patient being treated.

Removal of other types of dental adhesive is similarly impossible to achieve in a completely satisfactory manner. On this topic, the removal of dental cements, which are used to place temporary fillings in a cavity formed inside the tooth, for example, after the removal of caries, may be mentioned. Such dental cements are usually mechanically removed using a dental bur. This method can lead to damage to the patient's dental tissue.

Purpose and essence of the invention

The present invention overcomes the disadvantages of prior art techniques.

In a first aspect, the invention provides a dental adhesive comprising at least one polymerizable monomer, a polymerization initiator and thermally expandable particles comprising a shell encapsulating an expanding agent, wherein the dental adhesive is notable in that the shells of the thermally expandable particles are made from a copolymer of acrylonitrile and methyl methacrylate .

The inventors during their work made two main observations.

First, according to their observations, the use of ultrasonic vibrations is intended to expand the thermally expandable particles, which, thereby, destroys the polymer framework of the adhesive and reduces its adhesive ability. This effect occurs regardless of the nature of the shells of thermally expandable particles. As a result, exposure to ultrasound makes it possible to obtain effective and comfortable peeling off of the dental adhesive while providing heating that is limited, thereby reducing the occurrence of a risk of burns to the patient.

In addition, it has been observed that the use of particular thermally expandable particles comprising a shell made from acrylonitrile-methyl methacrylate copolymer has the objective of further reducing heat when sonicated, since the expansion of these particles corresponds to a transformation that is endothermic.

Thus, the invention makes it possible at the end of the treatment to peel off the dental adhesive in a way that is simpler and more comfortable for the patient, in particular by reducing the risk of burns and damage to the dental tissue.

In one embodiment, the mass content of thermally expandable particles is in the range from 10% to 45%.

The mass content of thermally expandable particles, which is 10% or more, serves to further facilitate the peeling off of the adhesive when using ultrasound. Limiting this weight content to no more than 45% also makes it possible to ensure good adherence of the adhesive during treatment.

In particular, the mass content of thermally expandable particles may be in the range of 10% to 20%.

In one embodiment, the polymerizable monomer(s) is selected from: bisphenol A-glycidyl dimethacrylate (Bis-GMA); triethylene glycol dimethacrylate (TEGDMA); hydroxyethyl methacrylate (HEMA); polyethylene glycol dimethacrylate (PEGDMA); diurethane dimethacrylate (DUDMA); and mixtures of such monomers.

The invention also provides a method for peeling off a polymerized dental adhesive attached to a tooth surface, said polymerized adhesive containing at least a resin and thermally expandable particles, the method being remarkable in that the polymerized adhesive is peeled off by exposing the polymerized adhesive to ultrasonic vibrations. .

Such a method makes it possible to peel off the cured dental adhesive in a manner that is comfortable for the patient, in particular by reducing the risk of burns and damage to dental tissue.

The polymerized adhesive can be obtained by polymerizing the adhesive described above. Thus, the thermally expandable particles may include a shell made from a copolymer of acrylonitrile and methyl methacrylate and an encapsulating expander.

As mentioned above, the use of specific thermally expandable particles is intended to impose even greater restrictions on heating during peeling when using ultrasound.

In particular, the frequency of the ultrasonic vibrations exerting an effect may be in the range of 26 kilohertz (kHz) to 36 kHz.

The dental adhesive described above can be used in various dental applications.

Thus, in the first example, the dental adhesive may be an orthodontic adhesive and it may be used to attach an orthodontic appliance to a tooth surface.

Under such circumstances, at the end of the orthodontic treatment, the orthodontic appliance is peeled off by the action of ultrasonic vibrations on the cured adhesive. Thus, in this first example, the method is such that the dental apparatus is attached to the surface of the tooth using a polymerized dental adhesive, and such that the apparatus is peeled off by ultrasonic vibrations.

In particular, the exposure to ultrasonic vibrations can be continued after the orthodontic appliance has been peeled off in order to peel off the remnants of the polymerized dental adhesive adhering to the tooth surface.

In a second example, the dental adhesive may be a dental cement used to seal a cavity formed in a tooth.

Thus, in this second example, the method is such that the polymerized dental adhesive is a dental cement that seals a cavity in a tooth, and such that a filling is removed from the cavity by exposure to ultrasonic vibrations.

Brief description of the drawings

Other characteristics and advantages of the invention will become apparent from the following description of the invention, presented by way of non-limiting example and with reference to the accompanying drawings, in which:

fig. 1 is a flow chart showing the various steps involved in bonding and then bonding an orthodontic appliance to and from the tooth surface, which can be done in the context of an example of the invention;

fig. 2 is a diagram showing an orthodontic appliance attached to a tooth surface;

fig. 3 is a diagram showing the use of ultrasound to peel an orthodontic appliance from a tooth surface in the context of a first example of the method of the invention;

fig. 4 is a diagram showing the use of ultrasound to peel off residual adhesive after peeling off an orthodontic appliance in the context of a first example of the method of the invention;

fig. 5 is a diagram showing the state of the tooth surface that is obtained after the removal of residual adhesive in the context of the first example of the method of the invention;

fig. 6 is a flow chart showing the various steps involved in placing a temporary filling in a cavity formed within a tooth and subsequently removing the filling from it, where these steps may be carried out in the context of one embodiment of the invention;

fig. 7 is a diagram showing the use of ultrasound to remove a filling from a cavity filled with dental cement in the context of a second example of the method of the invention;

fig. 8 is a diagram showing a cavity after removal of a filling obtained after removal of dental cement; and

fig. 9 shows the results obtained using differential scanning calorimetry and comparing the endothermic nature of the expansion of two types of thermally expandable particles.

Detailed description of embodiments

With reference to FIG. 1-5, the following is a description of one example of the invention in which an adhesive is used to attach an orthodontic appliance to a tooth surface.

In order to adhere the orthodontic appliance, an adhesive layer is initially applied to the orthodontic appliance and/or to the tooth surface to be received by the appliance (step E1). In advance, the usual pre-treatment in the form of cleaning and applying a mordant to the tooth surface can be carried out.

The adhesive contains at least one polymerizable monomer and a polymerization initiator. Said at least one polymerizable monomer may be an acrylate or methacrylate monomer. The adhesive may be a single polymerizable monomer, or it may contain a mixture of many different polymerizable monomers.

The adhesive used in the context of the invention also contains thermally expandable particles. Each thermally expandable particle includes a shell that encapsulates an expanding additive (expandable additive).

In a preferred embodiment, the shell is made from a copolymer of acrylonitrile and methyl methacrylate (AN/MMA). Coated particles are available as Expancel FG52 DU 80 or Expancel 031 DU 40 from AkzoNobel.

In one embodiment, it is possible to use thermally expandable particles, including a shell made from a copolymer of vinylidene chloride and acrylonitrile (VCl ₂ /AN). Coated particles are available under the designation Microsphere® F-30 from Matsumoto.

By way of example, the expander may be a hydrocarbon such as butane. The expander may be in a gaseous state.

The average size (D50) of the thermally expandable particles can range from 6 micrometers (μm) to 80 μm.

The adhesive may also contain a coupling agent such as organosilane. The adhesive may also contain at least one filler such as silica.

In particular, the adhesive may contain:

- mentioned at least one polymerizable monomer at a weight content in the range from 24% to 84.8%, for example, in the range from 57.5% to 79.4%;

- the polymerization initiator at a weight content in the range from 0.1% to 1%, for example, in the range from 0.1% to 0.5%; and

- thermally expandable particles at a mass content in the range from 10% to 45%, for example, in the range from 10% to 20%; and

- optional filler at a weight content in the range from 5% to 25%, for example, in the range from 10% to 20%; and

- optional coupling agent (adhesion agent) at a mass content in the range from 0.01% to 5%, for example, in the range from 0.5% to 2%.

Following this, immediately after applying the adhesive, the orthodontic appliance is placed on the surface of the tooth (step E2).

The orthodontic appliance may be an orthodontic bracket to which an orthodontic wire is to be attached. In one embodiment, the orthodontic appliance may be, for example, an orthodontic ring or a retaining arch. The orthodontic appliance can be made of metal, ceramic or composite material.

Immediately after positioning in place of the orthodontic appliance, the monomer(s) are polymerized, for example by exposure to light irradiation (step E3). The polymerized adhesive that is obtained contains a resin that results from the polymerization of the polymerizable monomer(s). The polymerization is initiated using a polymerization initiator. The orthodontic appliance is attached to the tooth surface using a cured adhesive. It is possible to attach a plurality of orthodontic brackets to a patient's teeth. Once the orthodontic brackets are in place, when using these brackets, an orthodontic wire can be attached to perform the desired orthodontic treatment.

At the end of the orthodontic treatment, the orthodontic appliance(s) are peeled off by exposure of the polymerized adhesive layer to ultrasound (step E4).

To carry out this step, an ultrasonic applicator, such as an ultrasonic tip, is advanced towards the cured adhesive. As one example of a suitable ultrasonic applicator, insert No. 10P sold by the supplier Satelec can be mentioned. The frequency of the ultrasound used for peeling can be in the range of 26 kHz to 36 kHz.

It is preferred to use thermally expandable particles, each of which has an AN/MMA copolymer shell. Figure 9 shows the experimental result obtained using differential scanning calorimetry (DSC), which demonstrates that the expanding AN/MMA particles (curve A) are significantly more endothermic than the expanding VCl2/AN particles (curve B): 69.62 joules per one gram (J/g) compared to 13.83 J/g. This test was performed using Expancel FG52 DU 80 AN/MMA particles and Microsphere® F-30 VCl ₂ /AN particles from supplier Matsumoto. During the test, the temperature was increased at a rate of 3°C/minute (min) from 60°C to 140°C. During thermal activation in the DSC test, the AN/MMA particles expanded at a temperature somewhat higher than the corresponding temperature at which the VCl ₂ /AN particles expanded. However, in the case of particle expansion due to ultrasonic vibrations, as in the context of the invention, there will be no need to bring the AN/MMA particles to an elevated temperature, and the heating produced during peeling is much more limited with AN/MMA particles. than with VCl ₂ /AN particles. Thus, the use of AN/MMA particles makes it possible to provide even more comfortable peeling of the adhesive when using ultrasound than when using VCl ₂ /AN particles.

In FIG. 2 demonstrates the implementation of orthodontic treatment, in which an orthodontic bracket 1 is attached to the surface of the 5th tooth.

Bonding of the bracket 1 to the surface 5 is promoted by using a layer of polymerized adhesive 16 which contains resin 4 and thermally expandable particles 6.

A layer of polymerized adhesive 16 is located between the back wall 1a of the bracket 1 and the surface 5. In order to carry out orthodontic treatment, an orthodontic wire 2 is attached to the bracket 1.

In FIG. 3 and 4 show the detached bracket 1 at the end of the orthodontic treatment.

The ultrasonic tip 10 is advanced towards the cured adhesive 16 and vibrated at an ultrasonic frequency (FIG. 3). Under this influence, the thermally expandable particles 6 expand, thereby destroying the adhesive's polymer framework. The ultrasonic handpiece 10 may be provided with a water delivery nozzle to improve the removal of the adhesive 20 from the tooth surface.

The treatment worker can then easily detach the bracket 1 from the tooth surface 5 (arrow D in FIG. 4) with limited heat and without risk of damage to the dental tissue.

It is possible for adhesive residue 20 to remain on the tooth surface 5 after the bracket 1 has been peeled off, as shown in FIG. four.

Preferably, sonication may be continued after the bracket 1 has been detached in order to eliminate the residue 20. After that, the tooth is in a state 5 of the adhesive-free surface, as shown in Figure 5.

The use of ultrasound is beneficial to avoid the use of a dental bur to remove residual adhesive, thereby further limiting the risk of damage to dental tissue.

With reference to FIG. 6-8, the following is a description of an embodiment in which the adhesive is a dental cement used to place a temporary filling in a cavity present in a tooth. By way of example, such dental cement may be used to place a filling in a cavity resulting from the removal of caries while awaiting subsequent treatment.

With reference to FIG. 6, the measurement example described herein includes filling a cavity with dental cement formed from the dental adhesive described above (step E10).

After that, the adhesive is polymerized in accordance with the above description of the invention in such a way as to obtain a polymerized dental cement inside the cavity, (step E30). Thus, the polymerized dental cement serves to seal the cavity for the desired length of time while waiting for subsequent dental treatment.

At the desired time point, the cured dental cement is removed by sonication. In a variant similar to that described above, sonication results in expansion of the thermally expandable particles and unsticking of the dental cement so that the filling is removed from the cavity (step E40).

The removal of a filling from a cavity is described with reference to FIG. 7 and 8.

In FIG. 7 shows the location of the ultrasonic tip 10 in the vicinity of the cured dental cement 26 sealing cavity C. As described above, the cement 26 contains resin 4 and thermally expandable particles 6. The characteristics described above in relation to the orthodontic adhesive, such as the content of various ingredients, apply to this embodiment. .

As a result of the expansion of the thermally expandable particles 6 when exposed to ultrasound, the cement 26 becomes non-adherent and is removed from the cavity C.

This treatment results in a cavity after removal of the filling C, as shown in FIG. eight.

This method of removing a filling from a cavity filled with dental cement using ultrasound is advantageous in order to avoid the use of a dental bur, thereby limiting the risk of damage to dental tissue.

The invention is used for the treatment of natural teeth or artificial teeth.

Example

Received orthodontic adhesive having the composition shown in the following table 1. The proportions of each of the ingredients are presented as mass percent.

Table 1

Ingredients BIS-GMA 48.68% TEGDMA 20.87% Expancel FG52 DU 80 15.00% Photoinitiator system 0.45% Filler (modified silicon dioxide) 14.00% Gelling agent (colloidal silicon dioxide) 1.00% TOTAL 100.00%

In order to manufacture an orthodontic adhesive having the composition shown in Table 1 above, the following work protocol was implemented.

The first mixture of BIS-GMA and TEGDMA monomers was made in a beaker using a stirrer of the turbotest type. The total duration of the mixing step was 15 minutes. Stirring was carried out at a speed of 200 revolutions per minute (min).

The photoinitiator system was included in the first mixture and mixing was carried out for 40 minutes using a "turbotest" stirrer. The photoinitiator system was a system comprising camphorquinone and a tertiary amine. The beaker was surrounded by aluminum foil to avoid exposure to light. Stirring was carried out at a speed of 180 rpm. After that, the content of the mixture obtained in this way was transferred to the vessel of the planetary mixer and mixed in vacuum for 5 minutes. Thus, a second mixture was obtained.

The filler was added to the second mixture and mixing was carried out for about 10 minutes to obtain a paste. Thereafter, an additional mixing stage of the resulting paste was carried out under vacuum for 5 minutes. Thus, a third mixture was obtained.

Expancel FG52 DU 80 thermally expandable particles were then added to the third mixture. A first agitation was performed for 5 minutes to completely incorporate the particles, followed by a second agitation under vacuum for 5 minutes. Thus, a fourth mixture was obtained.

Thereafter, the gelling agent was added to the fourth mixture. Stirring was carried out for 2 minutes in order to completely include the gelling agent. After that, stirring was carried out for 8 minutes under vacuum.

The orthodontic adhesive that is obtained at the end had a weight of 91.91 grams (g). The resulting adhesive was in the form of a pale yellow paste that was tacky and thick.

Thereafter, the orthodontic adhesive obtained in this way is used to adhere the orthodontic bracket to the tooth surface to evaluate the feasibility of bonding the bracket using ultrasound. The following working protocol has been implemented:

- cleaning the surface of each tooth;

- application to the same surfaces of a mordant in the form of a gel, which was placed in place and left in place for from 30 seconds (sec) to 60 seconds;

- removal of the mordant gel, rinsing and drying the surface on which it was applied;

- using a syringe to apply orthodontic adhesive to the back wall of the orthodontic bracket for attachment;

- the location of the bracket on the surface of the teeth and the correction of its location when using the hook;

- removal of excess adhesive in the vicinity of the base of the bracket without moving it;

- using blue light irradiation from a "Mini LED" device sold by the supplier Satelec to cure the orthodontic adhesive for 5 sec to 25 sec above each interdental side;

- repeating the operations described above for the complete dental arch to be processed; and

- the location of the orthodontic wire after the attachment of the last bracket.

Subsequently, sonication was applied in the vicinity of each bracket at the interface between adhesive and bracket using a 10P insert sold by Satelec. Thus, the brackets were easily peeled off the surfaces of the teeth with limited heating and without damaging the dental tissue.

After removal of the orthodontic wire and brackets, teeth that still showed adhesive deposits were cleaned by sonication until all residue was removed.

The term "ranging from ... to ..." should be understood to include boundary values.

Claims (8)

1. A dental adhesive containing at least one polymerizable monomer, a polymerization initiator and thermally expandable particles containing a shell encapsulating an expanding additive, while the dental adhesive is characterized in that the shells of thermally expandable particles are made of a copolymer of acrylonitrile and methyl methacrylate, while the mass content of thermally expandable particles is in the range from 10% to 45%. 2. Adhesive according to claim 1, in which the mass content of thermally expandable particles is in the range from 10% to 20%. 3. The adhesive according to claim 1, wherein the polymerizable monomer(s) is selected from bisphenol A-glycidyl dimethacrylate; triethylene glycol dimethacrylate; hydroxyethyl methacrylate; polyethylene glycol dimethacrylate; diurethane dimethacrylate; and mixtures of such monomers. 4. A method for peeling off a polymerized dental adhesive according to claim 1 attached to a tooth surface, wherein said polymerized adhesive comprises at least a resin and thermally expandable particles having a shell made from an acrylonitrile-methyl methacrylate copolymer and an encapsulating expander, where the method is different the fact that the cured adhesive is peeled off by exposing the cured adhesive to ultrasonic vibrations. 5. The method according to claim 4, where the frequency of the applied ultrasonic vibrations is in the range from 26 kHz to 36 kHz. 6. The method of claim. 4, where the dental apparatus is attached to the surface of the tooth using a polymerized dental adhesive, and where the apparatus is peeled off by exposure to ultrasonic vibrations. 7. The method of claim. 6, where the impact of ultrasonic vibrations is continued after peeling off the orthodontic appliance to peel off the remainder of the polymerized dental adhesive located on the surface of the tooth. 8. The method of claim. 4, where the polymerized dental adhesive is a dental cement that closes the cavity in the tooth, and where the filling is removed from the cavity as a result of exposure to ultrasonic vibrations.

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