LIGHT-CURING COMPOSITION FOR THE PRODUCTION OF DENTAL COMPONENTS WITH MATT SURFACES

Abstract

The invention relates to a light-curing composition for producing dental components in a DLP method or SLA method, comprising, in relation to the total mass of the light-curing composition: a liquid monomer composition with a mass fraction of 60% or more, comprising one or more radically polymerizable monomers, one or more photoinitiators with a combined mass fraction in the range from 0.001 to 10%, and solid polymer particles with a particle diameter in the range from 0.4 to 4 μm and a combined mass fraction in the range from 0.1 to 30%, wherein the solid polymer particles are dispersed in the liquid monomer composition.

Claims

1. A light-curing composition for producing dental components in a digital light processing (DLP) method or a stereolithography (SLA) method, comprising, based on the total mass of the light-curing composition: a liquid monomer composition with a mass fraction of 60% or more, comprising one or more radically polymerizable monomers, one or more photoinitiators with a combined mass fraction in the range from 0.001 to 10%, and solid polymer particles with a particle diameter in the range from 0.4 to 4 μm and a combined mass fraction in the range from 0.1 to 30%, wherein the solid polymer particles are dispersed in the liquid monomer composition.

2. The light-curing composition according to claim 1, wherein the solid polymer particles comprise polymers of monomers selected from the group consisting of monofunctional (meth)acrylates, polyfunctional (meth)acrylates, and polymethyl methacrylate, wherein the solid polymer particles comprise polymers of monomers that are not part of the liquid monomer composition.

3. The light-curing composition according to claim 1, wherein the solid polymer particles are present in the light-curing composition as non-agglomerated particles, wherein the solid polymer particles are dispersed substantially homogeneously in the liquid monomer composition.

4. The light-curing composition according to claim 1, wherein the liquid monomer composition comprises radically polymerizable monomers whose boiling point at 101.3 kPa pressure is one or more above 100° C., above 120° C., or above 140° C.

5. The light-curing composition according to claim 1, wherein the solid polymer particles have a particle diameter in the range from 0.5 to 2.5 μm, or in the range from 0.7 to 2 μm.

6. The light-curing composition according to claim 1, wherein the light-curing composition has at 23° C. a dynamic viscosity in the range from 0.1 to 10 Pa s, in the range from 0.5 to 5 Pa s, or in the range from 0.7 to 2.5 Pa s.

7. The light-curing composition according to claim 1, wherein the solid polymer particles have a substantially spherical particle shape and have been produced by spray-drying.

8. A method for producing a light-curing composition for the production of dental components in a digital light processing (DLP) method or a stereolithography (SLA) method, comprising the steps of: A) producing or providing a liquid monomer composition comprising one or more radically polymerizable monomers, B) producing or providing solid polymer agglomerates comprising agglomerated solid polymer particles with a particle diameter in the range from 0.4 to 4 μm, C) mixing the components produced or provided in steps A and B in order to obtain a basic mixture, comprising on the basis of the total mass of the basic mixture: the liquid monomer composition with a mass fraction of 60% or more, and the solid polymer agglomerates with a combined mass fraction of 0.1 to 30%, E) mechanically treating the basic mixture to break down the solid polymer agglomerates and to disperse the polymer particles in the liquid monomer composition.

9. The method according to claim 8, wherein the mechanical treatment is carried out by a milling process and/or stirring process and/or rolling process, in particular with a ball mill and/or a dissolver and/or a three-roll mill, preferably in a rolling process, in particular in a three-roll mill.

10. Use of a light-curing composition according to claim 1 for producing dental components with matte surfaces in a digital light processing (DLP) method or as stereolithography (SLA) method, wherein the surface of the dental component has a gloss value of 10 GU or less, 5 GU or less, or 2 GU or less.

11. Use of solid polymer particles with a particle diameter in the range from 0.4 to 4 μm in a light-curing composition for the production of dental components in a digital light processing (DLP) method or a stereolithography (SLA) method for reducing the gloss of the dental components obtained by light curing.

12. A kit for producing a light-curing composition according to claim 1, comprising as separate components in separate containers: solid polymer agglomerates comprising agglomerated solid polymer particles with a particle diameter in the range from 0.4 to 4 μm, and a liquid monomer composition comprising one or more radically polymerizable monomers.

Description

[0103] In the drawings:

[0104] FIG. 1 shows a micrograph of spray-dried polymer agglomerates of polymethyl methacrylate at 200×magnification;

[0105] FIG. 2 shows a micrograph of the primary particles of a spray-dried polymer agglomerate of polymethyl methacrylate at 8000×magnification;

[0106] FIG. 3 shows a micrograph of the primary particles of a spray-dried polymer agglomerate of polymethyl methacrylate at 10000×magnification;

[0107] FIG. 4 shows a plot of the experimentally determined gloss number (Y) of test specimens produced from light-curing compositions, as well as the dynamic viscosity (Z) of the corresponding light-curing compositions plotted against the mass fraction of solid polymer particles (X) in the light-curing com positions.

[0108] The invention and preferred embodiments of the invention are explained and described in more detail below with reference to experiments.

[0109] To demonstrate the surprising technical effect of the light-curing composition according to the invention, a reference system is considered below which is regularly used by the inventors in order to investigate the effects of additives, for example. Here, the reference system comprises in particular five radically polymerizable monomers which have very different chemical structures and which represent a broad spectrum of (meth)acrylates used particularly frequently in practice. For the solid polymer particles, PMMA particles were selected in the reference system because they were available as sufficiently small particles and solid PMMA is, from experience, relatively representative of polymerized (meth)acrylates. Neither in the experiments shown here nor in the accompanying experiments carried out by the inventors were any observations made that would have called into question the assumption that the results are transferable to other systems.

[0110] The reference system uses the following: [0111] a liquid monomer composition consisting of a mixture of a first and a second monomer mixture in a mixing ratio of 1 to 1.67 by mass, wherein the first monomer mixture consists of equal mass fractions of tris(2-acryloyloxyethyl)isocyanurate, dicyclopentanyl methylacrylate and tricyclo[5.2.1.0.sup.26]decanedimethanol diacrylate, and wherein the second monomer mixture consists of bisphenol A ethoxylate dimethacrylate and diurethane dimethacrylate in a mass ratio of 2 to 1. [0112] phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide as photoinitiator; [0113] an additive composition consisting of 2-hydroxy-4-methoxybenzophenone (additive 1); titanium (IV) oxide (additive 2), flame black (additive 3) and 5% PV true blue A2R in diurethane dimethacrylate (additive 4); and [0114] polymer particles of polymethyl methacrylate, i.e. the polymer of methyl methacrylate.

[0115] From these substances, light-curing compositions were produced as listed in Table 1, wherein the values are given as a mass fraction in percent. Of these compositions, Ex. 1 to Ex. 5 are light-curing compositions according to the invention, whereas the composition Comp. 1 is a comparative composition which contains no solid polymer particles.

TABLE-US-00001 TABLE 1 Composition of the investigated light-curing compositions with different contents of solid polymer particles. Comp. Ex. Ex. Ex. Ex. Ex. Substance 1 1 2 3 4 5 Monomer composition 98.22 97.00 95.76 93.44 91.21 88.26 Photoinitiator 0.82 0.80 0.80 0.78 0.76 0.80 Additive 1 0.35 0.34 0.34 0.33 0.32 0.34 Additive 2 0.55 0.54 0.54 0.53 0.51 0.54 Additive 3 0.03 0.03 0.03 0.03 0.03 0.03 Additive 4 0.03 0.03 0.03 0.03 0.03 0.03 Polymer particles 0.00 1.25 2.49 4.87 7.13 10.00 Total 100 99.99 99.99 100.01 99.99 100

[0116] Minimal deviation in the sum of all components from 100% is due to rounding, but, as understood by the person skilled in the art, does not affect the validity of the experiments, especially since it would not make sense from the point of view of a person skilled in the art to specify the mass fractions more precisely than the production method allows.

[0117] The liquid monomer composition comprises five radically polymerizable monomers, and is produced by mixing the components. The photoinitiator is suitable for causing polymerization of the liquid monomer composition by irradiating the composition with light. The polymer particles are solid, spherical polymer particles with a diameter in the range from 0.7 to 2.0 μm. The compositions described above were produced by the method according to the invention, wherein the polymer particles were introduced into the compositions by adding spherical polymer agglomerates with a diameter of about 15 to 75 μm. The additives and the photoinitiator were added to the liquid monomer composition before being mixed with the polymer agglomerates. Mechanical treatment of the basic mixture to break down the solid polymer agglomerates was carried out using a three-roll process wherein the mixture was homogenized twice through a roll gap of 5 μm. As a result of the mechanical treatment, the polymer particles were present in the compositions according to the invention in dispersed form as non-agglomerated particles, wherein no concentration gradients of solid polymer particles were observed over the volume of the light-curing compositions.

[0118] FIGS. 1 to 3 show micrographs of the polymer agglomerates used at various magnifications (200×, 8000× and 10000×), wherein the solid polymer particles can be clearly seen as primary particles of the polymer agglomerates.

[0119] For the samples produced, the dynamic viscosity (Z) at 23° C. was determined using a Rheometer (Anton Paar, Physica NCR 301, viscosity ranges 200-3000 m.Math.Pa s at 100/s, 23° C.) according to DIN 1342-2; 2003-11 Newtonian liquids and DIN 1342-3; 2003-11 Non-Newtonian liquids. The results obtained are collated in Table 2.

TABLE-US-00002 TABLE 2 Dynamic viscosities (Z) of the investigated light-curing compositions with different contents of solid polymer particles. Dynamic viscosity Sample (Z)/(m Pa s) Comp. 1 1050 Ex. 1 1100 Ex. 2 1300 Ex. 3 1700 Ex. 4 2200 Ex. 5 3100

[0120] The measured values clearly indicate that the viscosity of the light-curing compositions according to the invention is still sufficiently low, even for a mass fraction of the solid polymer particles of 10%, for use in a SLA or DLP method. By extrapolating the viscosity increase as a function of the mass fraction of the polymer particles, it can be estimated that mass fractions of up to 30% are feasible without losing the fundamental suitability of the composition according to the invention for use in SLA or DLP methods.

[0121] At the same time, it has proven advantageous that the viscosity of the light-curing compositions can be adjusted particularly easily by adding the solid polymer particles in light-curing compositions according to the invention and can be adapted to the respective requirements without needing, for example, inorganic additives.

[0122] To investigate the gloss property of the dental components produced from the light-curing compositions according to the invention, test specimens measuring 60 mm×10 mm×3.3 mm were produced by a DLP method using a DLP printer from the Kulzer company of the cara Print 4.0 type. The test specimen was manufactured in each case horizontally or vertically, i.e. the material layers generated in the DLP method were built up parallel or perpendicular to the surface measured as part of the gloss measurement.

[0123] The gloss figures were determined using a gloss measurement method which was performed with a device from the BYK company of the micro-TRI gloss type using a 60° angle. The values obtained are summarized in Table 3.

TABLE-US-00003 TABLE 3 Gloss number (Y) of the investigated test specimens produced from light-curing compositions with different contents of solid polymer particles, including standard deviation. Gloss number Gloss number (Y)/GU (Y)/GU (horizontally (vertically Sample manufactured) manufactured) Comp. 1 5.3 ± 1.2 43.4 ± 3.2  Ex. 1 4.6 ± 1.3  9.5± 1.1 Ex. 2 3.6 ± 0.8 2.6 ± 0.7 Ex. 3 2.5 ± 0.6 — Ex. 4 2.1 ± 0.6 — Ex. 5 1.8 ± 0.7 1.2 ± 0.9

[0124] The values of the gloss number (Y) tabulated above for horizontal manufacturing are plotted in FIG. 4 together with the dynamic viscosities (Z) against the mass fraction of the solid polymer particles in the corresponding light-curing compositions (X).

[0125] It is clear from the experimental data that even adding small amounts of solid polymer particles with a particle diameter in the range from 0.4 to 4 μm results in an advantageous reduction in the gloss property of the test specimens. The observed effect is particularly pronounced in the case of vertically manufactured test specimens, i.e. when the surface gloss is measured on a surface that is parallel to the built-up layers. Even when a 1.25% mass fraction of solid polymer particles is added, a reduction of more than 75% in the gloss property is observed. The data obtained indicate that this is an effect whose magnitude varies with the amount of solid polymer particles, which means that there is no indication of a possible limit value above which the effect would be observed for the first time. By selecting suitable amounts of solid polymer particles, particularly matte and therefore readily scannable surfaces can be obtained accordingly in the dental components produced from light-curing compositions according to the invention.

[0126] In addition, the average surface roughness Ra of selected test specimens was determined. The values obtained are summarized in Table 4.

TABLE-US-00004 TABLE 4 Average surface roughness (Ra) of the investigated test specimens produced from light-curing compositions with different contents of solid polymer particles. Average surface roughness Sample (Ra)/μm Comp. 1 1.36 Ex. 1 1.94 Ex. 2 1.68 Ex. 3 1.75 Ex. 4 0.79 Ex. 5 1.13

[0127] It is evident that the average surface roughness of the test specimens produced with the light-curing compositions according to the invention is advantageously not significantly increased compared to the comparative sample. Accordingly, it is advantageously possible to manufacture dental components which have smooth surfaces. Such dental components are particularly easy to clean and make it possible to remove applied molding compositions so as to leave especially little residue.