RADICAL POLYMERISATION INITIATORS FOR LIGHT-CURABLE DENTAL MATERIALS

Abstract

The invention provides a light-curable dental material comprising a polymerizable compound having at least one ethylenically unsaturated bond and a hexaaryl bisimidazole as a photopolymerisation initiator.

Claims

1. A light-curable dental material comprising (i) a polymerizable compound having at least one ethylenically unsaturated bond and (ii) a hexaaryl bisimidazole.

2. The light-curable dental material according to claim 1, further comprising an α,β-diketone as a polymerization initiator and optionally a polymerisation inhibitor.

3. The light-curable dental material according to any one of claims 1 or 2, further comprising a solid particulate filler.

4. The light-curable dental material according to any of claims 1 to 3, wherein said hexaaryl bisimidazole has the following structure (I):
Ar.sub.3T-TAr.sub.3  (I) wherein each T is an imidazole moiety and each Ar stands for an optionally substituted aryl group that may be the same or different and wherein the substitution on different groups Ar may be the same or different.

5. The light-curable dental material according to claim 1 or 4, wherein the hexaaryl bisimidazole is a homodimer or a heterodimer obtainable by oxidation of any of the triarylimidazoles represented by the following formula: ##STR00006## wherein Ar.sup.1, Ar.sup.2, and Ar.sup.3 may be the same or different and each represents an optionally substituted aryl group and multiple Ar.sup.1, Ar.sup.2, or Ar.sup.3 on the same hexaarylbisimidazole may be the same or different.

6. The light-curable dental material according to any one of claims 1 to 5, wherein the hexaaryl bisimidazole has the structure of the following formula: ##STR00007## wherein Ar.sup.1, Ar.sup.2 and Ar.sup.3 may be the same or different and each represents an optionally substituted aryl group and multiple Ar.sup.1, Ar.sup.2 or Ar.sup.3 on the same hexaarylbisimidazole compound may be the same or different.

7. The light-curable dental material according to any one of claims 4 to 6, wherein the aryl group is selected from phenyl and naphthyl.

8. The light-curable dental material according to any one of claim 4 to 7, wherein each aryl group may have 1 to 5 substituents selected from the group consisting of C.sub.1-6-alkyl, C.sub.1-6-alkoxy, hydroxy, halo, cyano, nitro, nitroso, mercapto, carboxyl, sulfonate, thiol, amino, phenyl, pyridyl, and trifluoromethyl.

9. The light-curable dental material according to any one of claim 1 to 8, wherein the concentration of said hexaaryl bisimidazole based on the total weight of all polymerizable compounds having at least one ethylenically unsaturated bond is from 0.01 to 2.0, preferably from 0.05 to 1.5, and most preferably from 0.1 to 1.0 weight-%.

10. The light-curable dental material according to any one of claim 1 to 9, further comprising a co-initiator selected from the following compound classes: thiols, heteroaromatic thiols, benzothiazoles, benzooxazoles, tertiary amines, alcohols, thiocarboxylic acids.

11. The light-curable dental material according to any one of claim 1 to 10, further comprising a sensitizer for extending the wavelength range usable for activating the hexaaryl bisimidazole.

12. The light-curable dental material according to any one of claims 1 to 11, wherein the light-curable dental material is selected from the group consisting of a dental composite, dental ionomer cement, dental sealant, dental adhesive, dental adhesion promoter, dental adhesion preventer, dental cement, dental crown-forming material, and dental impression material.

13. Light-cured dental material obtained or obtainable by light curing the light-curable dental material of any one of claims 1 to 12.

14. Use of a hexaaryl bisimidazole in a light-curable dental material as a photoinitiator.

15. Light-curable dental material such as dental composite comprising a solid particulate filler and a polymerizable matrix, wherein the polymerizable matrix comprises: (i) one or more polymerizable compounds each having at least one ethylenically unsaturated bond and (ii) a hexaaryl bisimidazole.

Description

EXAMPLES 1 TO 23

[0061] Preparation of experimental resin mixtures: Resin mixtures were prepared with initiator and co-initiator concentrations as given in Table 2 by first mixing together UDMA (40 parts), HPGM (7 parts), and EBA (53 parts) at 40° C. for Resin A, or UDMA (5 parts), HPGM (5 parts), TMPTMA (5 parts), and EBA (85 parts) for Resin B. The initiators and inhibitors were then added as required in amounts shown in the table, and dissolved by stirring at 40-50° C. until no solid particles remained.

[0062] Preparation of dental composites: The chosen resin mixture (33.0 g), Aerosil R972 (0.75 g), and silanated glass with a mean particle size of about 0.8 μm (116.25 g) were kneaded together at 40° C. in a vertical kneader for 160 minutes, and the resulting paste was then degassed by stirring for ten minutes at a pressure of 210±10 mbar. Physical properties of the pastes were measured as described below, and are shown in Table 2.

TABLE-US-00002 TABLE 2 Formulations comprising hexaarylbisimidazoles, with measured physical properties co- % co- comp. yield flex. life- Ex. initiator initiator initiator initiator BHT str. str. str. time Doc No. resin — % — % % MPa MPa MPa VH5 sec mm 1 A 2-Cl HABI 0.5 MMT 0.5 0.0 327.5 152 139 67 300 2.0 2 A 2-Cl HABI 0.5 MMT 0.25 0.0 325.6 150 138.5 60 480 1.8 3 A 2-Cl HABI 0.25 MMT 0.5 0.0 302.9 136 131.5 54 540 1.8 4 A 2-Cl HABI 0.25 MMT 0.25 0.0 284.6 124 141.4 55 600 1.6 5 A 2-Cl HABI 0.75 MMT 0.25 0.0 348.5 163 138.7 63 360 1.9 6 A 2,4-Cl HABI 0.5 MMT 0.5 0.0 322.0 175 142.5 59 180 2.0 7 A 2,4-Cl HABI 0.5 MMT 0.25 0.0 283.5 152 141.1 57 420 3.0 8 A 2,4-Cl HABI 0.25 MMT 0.5 0.0 260.6 131 122.0 49 480 2.0 9 B 2-Cl HABI 0.5 MMT 0.5 0.05 253.2 110 93.0 23 >300 1.6 10 B TCDM-HABI 0.5 MMT 0.5 0.05 280.9 — 89.1 — >300 1.8 11 B 2,4-Cl HABI 0.5 MMT 0.5 0.05 267.2 127 124.6 — >300 2.0 12 B 2,4-Cl HABI 0.5 MMT 0.75 0.05 317.5 156 150.2 57 >300 2.3 13 B 2-Cl HABI 0.66 MMT 0.35 0.05 272.4 131 132.6 41 >300 2.0 14 B TCDM-HABI 0.75 MMT 0.35 0.05 271.5 120 122.4 28 >300 1.9 15 B 2,4-Cl HABI 0.73 MMT 0.35 0.05 277.0 138 140.0 47 >300 2.24 16 B 2-TFM HABI 0.73 MMT 0.35 0.05 281.5 135 137.9 33 >300 2.06 17 B 2-Cl HABI 0.66 MBT 0.51 0.05 299.4 152 123.2 55 >300 2.3 18 B TCDM-HABI 0.75 MBT 0.51 0.05 208.5 — — 54 >300 1.6 19 B 2,4-Cl HABI 0.73 MBT 0.51 0.05 297.3 149 122.1 59 >300 2.3 20 B 2-TFM HABI 0.73 MBT 0.51 0.05 293.9 144 144.9 54 >300 2.1 21 B 2,4-Cl, HABI 0.73 MBT 0.76 0.05 319.6 160 150.7 58 280 3.4 22 B 2-TFM HABI 0.73 MBT 0.76 0.05 318.2 156 161.9 59 210 2.5 23 B 2,4Cl HABI/ 0.73/ DMABE 0.6 0.3 284.4 136 127 49 >300 — CQ 0.31

Comparative Examples

[0063]

TABLE-US-00003 co- % co- comp. yield flex. life- Initiator initiator initiator initiator BHT str. str. str. time Doc No. Resin — % — % % MPa MPa MPa VH5 sec mm 1 A CQ 0.31 DMABE 0.6 0.6 293.5 133 119.7 58 135 3.0 2 B CQ 0.31 DMABE 0.6 0.6 264.8 145 100.7 58 70 3.6

KEY TO ABBREVIATIONS

[0064] UDMA Urethane dimethacrylate [0065] HPGM the reaction product of Hydroxypropyl methacrylate and glutaric anhydride [0066] EBA Ethoxylated bisphenol A dimethacrylate [0067] CQ Camphorquinone [0068] DMABE Dimethylamino benzoic acid, ethyl ester [0069] BHT butylated hydroxytoluene [0070] MMT 3-Mercapto-4-methyl-4H-1,2,4-triazole [0071] 2-Cl HABI 2,2′-Bis(2-chlorophenyl)-4,4′,5,5′-tetraphenyl-1,1′-biimidazole [0072] 2,4-Cl HABI 2,2′-Bis(2,4-dichlorophenyl)-4,4′,5,5′-tetraphenyl-1,1′-biimidazole [0073] TCDM 2,2,′4-Tris(2-chlorophenyl)-5-(3,4-dimethoxyphenyl)-4′,5′-diphenyl-1,1′-biimidazole [0074] 2-TFM HABI 2,2′-Bis(2-trifluoromethyl)-4,4′,5,5′-tetraphenyl-1,1′-biimidazole [0075] CDM 2-(o-Chloro)-4,5-bis(m-methoxyphenyl)-1,1′-biimidazole [0076] TCTM 2,5-Bis(o-chlorophenyl)-4-[3,4-dimethoxyphenyl]-1H-imidazole dimer [0077] 2-MBO 2-Mercaptobenzoxazole [0078] 2-MBT 2-Mercaptobenzothiazole [0079] Doc depth of cure [0080] VH5 Vickers hardness measured with a load of 5 kg (49.03 N)

[0081] It is seen from the examples in Table 2 that the use of a bisimidazole initiator according to the present invention leads to lengthened lifetimes of the compositions under the influence of ambient light at 10000 lux. Further, composite material with improved compressive, yield, and flexural strengths compared to the comparative examples can be obtained.

[0082] The content (including description and claims) of European patent application 08008693.7 filed on May 8, 2008, the priority of which is claimed, is included herein by reference in its entirety.