Glass fillers for composites

Abstract

The invention relates to a particulate glass filler wherein glass particles of 0.2 to 1 m mean particle size are connected with other particles, the connection being effected by the glass material itself. More precisely particulate glass filler comprising glass particles, wherein the particles contains centrally located macro glass particles and on the outer surface located micro glass particles wherein the macro and micro glass particles are connected by the material of said particles. Further the invention relates to a method for manufacturing the glass particles and the particulate glass filler comprising said glass particles. It also relates to a composite or dental material comprising the above particulate glass filler.

Claims

1. A particulate glass filler comprising glass particles, wherein the glass particles comprise centrally located macro glass particles with connections to micro glass particles located on an outer surface of the macro glass particles, wherein the connections consist of a material of said glass particles, wherein the glass particles have a refractive index n in the range of n=1.50 to 1.60, and wherein the macro glass particles have a size in the range of 200 to 600 nm.

2. The particulate glass filler according to claim 1, wherein the connections consist of a material of the macro glass particles.

3. The particulate glass filler according to claim 1, wherein the macro glass particles are selected from dental glasses comprising barium and/or strontium.

4. The particulate glass filler according to claim 1, wherein the macro glass particles are selected from dental glasses having a transition temperature lower than 650 C.

5. The particulate glass filler according to claim 1, wherein the macro glass particles have a refractive index n in the range of n=1.50 to 1.58.

6. The particulate glass filler according to claim 1, wherein the macro glass particles are selected from dental glasses comprising barium aluminum silicate glass and/or strontium aluminum silicate glass.

7. The particulate glass filler according to claim 1, wherein the micro glass particles have a refractive index in the range of n=1.52 to 1.59.

8. The particulate glass filler according to claim 1, wherein the micro glass particles are selected from dental glass ceramics having a transition temperature of greater than 700 C.

9. The particulate glass filler according to claim 1, wherein the micro glass particles have a size in the range of 100 to 300 nm.

10. The particulate glass filler according to claim 1, wherein the glass particles have a mean particle size in the range of 0.2 to 1.0 m.

11. The particulate glass filler according claim 1, wherein the particulate glass filler is amorphous.

12. A method of producing a particulate glass filler according to claim 1 comprising the following steps: I. Dispersing glass filler with a refractive index n=1.50 to 1.60 with a suitable solvent; II. Sintering and welding the dispersed glass filler at 450 C. to 800 C.; III. Cooling the sintered glass filler to room temperature; IV. Dispersing welded filler in a suitable solvent; V. Drying of said glass filler; and VI. Obtaining a particulate glass filler comprising glass particles.

13. The particulate glass filler according to claim 1, wherein the macro glass particles have a size in the range of 400 nm100 nm.

14. The particulate glass filler according to claim 1, wherein the macro glass particles have a size in the range of 400 nm50 nm.

15. The particulate glass filler according to claim 8, wherein the micro glass particles are selected from dental glass ceramics having a transition temperature of greater than 750 C.

16. The particulate glass filler according to claim 8, wherein the micro glass particles are selected from dental glass ceramics having a transition temperature of greater than 800 C.

17. The particulate glass filler according to claim 9, wherein the micro glass particles have a size in the range of 2005 nm.

18. The particulate glass filler according to claim 9, wherein the micro glass particles have a size in the range of 1805 nm.

19. The particulate glass filler according to claim 10, wherein the glass particles have a mean particle size in the range of 0.3 to 0.6 m.

20. The particulate glass filler according to claim 1, wherein both the macro glass particles and the micro glass particles have a refractive index n in the range of n=1.50 to 1.60.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1a is an REM photograph of the inventive filler particles sintered together, as described in Example 1.

(2) FIG. 1b is a more detailed schematically image of inventive filler particles sintered together, as described in Example 1.

(3) FIG. 1c is a detailed schematically image of state of the art filler particles sintered together.

(4) FIG. 2 is a diagram showing the flexural strength of composites of the invention, compared to composite outside the invention.

(5) FIG. 3 is a diagram showing Young's modulus of composites of the invention, compared to composite outside the invention.

(6) FIG. 4 is a diagram showing the reflection (tooth brush abrasion of composites of the invention, compared to composite outside the invention.

(7) FIG. 5 is a diagram showing the mean roughness (tooth brush abrasion of composites of the invention, compared to composite outside the invention.

(8) FIG. 6 is a diagram showing the mean depth (ACTA method (poppy seed)) of different filler materials as described in table 2, compared to glass filler of the invention.

(9) FIG. 7 is a diagram showing the lost volume (ACTA method (poppy seed)) of different filler materials as described in table 3 compared to glass filler of the invention.

DETAILED DESCRIPTION

(10) In general, any glass filler particles may be used for the invention. Preferred are conventional dental glass fillers or materials used for the inventive particulate glass filler, for example made on the basis of boron silicate glass or aluminum silicate glass, such as glass made of barium borosilicate or lithium aluminium silicate and barium aluminium silicate, especially barium silicate dental glass fillers. Most preferred the particulate glass filler is comprising barium and/or strontium aluminium silicate dental glasses.

(11) The particulate glass filler comprising glass particles, wherein the glass particles contain centrally located macro particles with connections to micro particles located on the outer surface of the macro particles, wherein the connections consist of the material of said particles, and wherein the refractive index n of the glass particles is in the range of n=1.50 to 1.60.

(12) Macro particles according to the invention are particles having a particle size in the range of 200 nm to 1 m, in particular in the range of 400 nm+/200 nm.

(13) Micro particles according to the invention are particles having a particle size in the range of 50 nm to 390 nm, in particular in the range of 200 nm+/100 nm.

(14) Particulate glass filler according to the invention are glass particles having a mean particle size in the range of 0.2 m to 1.5 m, in particular 400 nm+/200 nm, wherein the glass particles contain centrally located macro particles with connections to micro particles located on the outer surface of the macro particles, wherein the connections consist of the material of said particles, and wherein the refractive index n of the glass particles is in the range of n=1.50 to 1.60.

(15) Preferably the above described particulate glass filler comprises a connection consisting of the material of the macro particles. More preferably the particulate glass filler comprising glass particles comprises macro particles which are selected from dental glasses comprising barium and/or strontium. Most preferably the inventive particulate glass filler comprises macro particles selected from dental glasses comprising barium aluminum silicate and/or strontium aluminum silicate.

(16) Preferred barium dental glass materials comprise at least 25 weight-% of BaO, in particular at least 30 weight-% of BaO, preferably at least 35 weight-% of BaO and barium aluminum silicate dental glass material comprise additionally to the amount of BaO at least 5 weight-% of Al.sub.2O.sub.3, in particular at least 8 weight-% of Al.sub.2O.sub.3, preferably at least 10 weight-% of Al.sub.2O.sub.3.

(17) Preferred strontium dental glass materials comprise at least 10 weight-% of SrO, in particular at least 15 weight-% of SrO, preferably at least 25 weight-% of SrO and strontium aluminum silicate dental glass material comprise additionally to the amount of SrO at least 5 weight-% of Al.sub.2O.sub.3, in particular at least 10 weight-% of Al.sub.2O.sub.3, preferably at least 15 weight-% of Al.sub.2O.sub.3.

(18) In a special embodiment the inventive glass filler with a refractive index n of the glass particles in the range of n=1.50 to 1.60 comprises macro particles made of dental glass comprising barium and/or strontium, preferably barium aluminum silicate and/or strontium aluminum silicate.

(19) In an embodiment the particulate glass filler according to the invention comprises glass particles of macro particles selected from dental glasses having a transition temperature lower than 650 C. Dental glass materials comprising barium and/or strontium, preferably barium aluminum silicate and/or strontium aluminum silicate, having a transition temperature lower than 650 C. are preferred. Said materials having a refractive index n in the range of n=1.50 to 1.60 are mostly preferred.

(20) In another embodiment of the invention the particulate glass filler comprises glass particles of macro particles having a refractive index n in the range of n=1.50 to 1.58. In particular these macro particles are preferably made of a dental glass material comprising barium and/or strontium and additionally, preferably barium aluminum silicate and/or strontium aluminum silicate, having a transition temperature lower than 650 C.

(21) In a preferred embodiment the inventive particulate glass filler comprises glass particles of macro particles of a size in the range of 200 to 600 nm, in particular 400 nm+/100 nm, more preferred +/50 nm. In particular in the range of 300 to 500 nm, preferably +/50 nm, preferably 400 nm+/50 nm.

(22) The inventive particulate glass filler comprises glass particles comprising micro particles having a refractive index n in the range of n=1.52 to 1.59. In particular said micro particles are connected to centrally located macro particles having a refractive index n in the range of n=1.50 to 1.58. Preferably this combination of micro and macro particles leads to glass particles of the inventive particulate glass filler. Most preferably the described combination is preferably used as the glass particles of the inventive particulate glass filler in curable dental materials and/or composites. The refractive index plays an important role for a good transparency of the dental materials.

(23) In another embodiment of the invention the particulate glass filler comprising glass particles with micro particles selected from dental glass ceramics having a transition temperature higher than the transitions temperature of the macro particle dental glass material, in particular higher than 700 C., in particular higher than 750 C., higher than 800 C. Preferred embodiments of the inventive particulate glass filler comprises macro and micro particles wherein their transitions temperature differs by at least 50 C., preferably at least 70 C., most preferably at least 100 C. In particular macro particles made of barium and/or strontium, preferably barium and or strontium aluminum silicate dental glass material, exhibit a transition temperature higher than the dental glass ceramic material of the micro particles as described.

(24) Suitable ceramic materials are nitride, carbide or oxide of the elements silicon, zirconium, aluminium, titanium, lithium, and/or lanthanum. AL.sub.2O.sub.3, SiO.sub.2, TiO.sub.2 La.sub.2O.sub.3, ZrO.sub.2, Li.sub.2O, P.sub.2O.sub.5 and MgO are preferred.

(25) Glass-ceramics are polycrystalline materials produced through controlled crystallization of base glass. Glass-ceramic materials share many properties with both glasses and ceramics. Glass-ceramics have an amorphous phase and one or more crystalline phases and are produced by a so-called controlled crystallization in contrast to a spontaneous crystallization, which is usually not wanted in glass manufacturing. Glass-ceramics have the fabrication advantage of glass as well as special properties of ceramics. Glass-ceramics usually have between 30% [m/m] to 90% [m/m] crystallinity and yield an array of materials with interesting properties like zero porosity, high strength, toughness, translucency or opacity, low or even negative thermal expansion.

(26) In another embodiment the inventive particulate glass filler comprises micro particles in the range of 100 to 300 nm, in particular 200 nm+/50 nm, more preferred 180 nm, in particular +/50 nm. In particular 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, 210 nm, 220 nm or 230 nm.

(27) In a preferred embodiment the inventive particulate glass filler comprising glass particles, preferably having a mean particle size of 0.2 m to 0.7 m, wherein the glass particles contain macro particles of dental glass comprising barium, preferably barium aluminium silicate, in the range of 400 nm+/50 nm having a refractive index in the range of n=1.50 to 1.58, preferably n=1.55+/0.01 and optionally having a transition temperature of lower than 650 C., preferably lower than 630 C., most preferably in the range of 630 C. to 580 C.

(28) and micro particles of dental glass comprising ceramics, in the range of 200 nm+/50 nm, having a refractive index in the range of n=1.50 to 1.58, preferably n=1.57+/0.01 and optionally having a transition temperature of greater than 700 C., in particular greater than 750 C., most preferably greater than 800 C.,
wherein macro particles are centrally located and said micro particles are connected to the outer surface of the macro particles. Preferably, the connection between the macro and micro particles is made of the material at least of the macro particles.

(29) The connection between the macro and micro particles, in particular obtainable by sintering and welding these particles, is effected by the dental glass material(s) itself. More precisely the connection may be made of the dental glass material barium only, barium aluminum silicate only, strontium only, strontium aluminum silicate only, ceramics only or of a combination of at least two of the mentioned materials.

(30) When strontium glass material is used, in particular strontium aluminum silicate, said material has a refractive index n=1.51+/0.01.

(31) The particulate glass filler according to the invention and the above described embodiments comprise glass particles in the range of 0.2 m to 1 m mean particle size, preferably in the range of 0.3 m to 0.8 m, more preferred 0.2 m to 0.7 m, most preferred in the range of 0.3 m to 0.6 m.

(32) The above described inventive particulate glass filler comprising the described glass particles preferably is an amorphous and in particular porous glass filler.

(33) Examples of commercially available dental glass particles without a limitation are those from SCHOTT comprising glass ceramics GM31684, GM31685, barium glasses GM27884, GM39923, G018-053, 8235, G018-186 and strontium glasses GM32087, G018-093 and G018-163. FIG. 1b a schematically image of the inventive glass filler comprising the above described dental glass particles, in particular representing the combination of GM27884 (refractive index n=1.52) as the centrally located macro particle and GM31685 (refractive index n=1.53) as the micro particles connected to GM27884. FIG. 1c a schematically image of state of the art particles with silica particles (refractive index 1.45) as the micro particles.

(34) Another object of the invention is a method of producing particulate glass filler comprising glass particles according to the invention, as described above, wherein the method comprises the following steps, in particular particulate glass filler as described above obtainable by the method comprising the following steps: I. Dispersing, in particular in a ball mill or other mixer suitable for mixing solids, glass filler with a refractive index n=1.5 to 1.60 with a suitable solvent, in particular the described macro and/or micro glass filler particles with a refractive index n=1.5 to 1.60 preferably with a ratio macro particles to micro particles of 1:1-4, II. Sintering and welding the dispersed glass filler, in particular the dispersed macro and/or micro glass filler particles, at 450 C. to 800 C., III. Cooling the sintered glass filler, in particular the macro with thereto connected micro glass filler particles, to room temperature, IV. Dispersing welded filler, preferably comprising macro and micro glass particles, wherein the micro particles are connected to the centrally located macro particles, in a suitable solvent, preferably an anhydrous alcohol, in particular in an ultrasonic dispersing machine, and V. Drying of said glass filler, preferably performed in a vacuum cold drying machine, wherein a particulate glass filler comprising glass particles is obtained. In particular glass particles
are obtained which contain centrally located macro particles with connections to micro particles located on the outer surface of the macro particles, wherein the connections consist of the material of said particles, and wherein the refractive index n of the glass particles is in the range of n=1.50 to 1.60. Most preferably an amorphous particulate glass filler is obtained.

(35) The solvent used in step I is preferably a mixture of water and alcohol, more preferably water and 0.01 wt-% to 1 wt-% alcohol, most preferably 0.1 wt-% alcohol with regard to the total of the mixture. The Dispersing step is preferably performed for 24 hours at 30 rpm (see example 1 below).

(36) Before sintering (step II) the dispersed particles may be dried, preferably in a vacuum cold drying machine. Step I results in amorphous glass filler particles of certain distance.

(37) In general, the particles are first subjected to a dispersion process in order to make the individual particles keep a distance from each other. This is preferably done by grinding with a suitable solvent.

(38) After removal of the solvent after step I the fillers are advantageously sintered together by thermal treatment (welding, step II).

(39) In a preferred embodiment of the above method the sintering (step II) is carried out at 500 C. to 770 C., more preferably from 600 C. to 750 C. The sintering is carried out preferably for 1 to 3 hours. In an embodiment of the inventive method the sintering and welding step is performed by the following temperature curve: heating up from room temperature to 600 C. (5 C./minute) then to 700 C./710 C./720 C. (2 C./minute) and keep this temperature for 2 hours; cooling from to 700 C./710 C./720 C. to 300 C. (2 C./minute) and cooling naturally to room temperature (step III).

(40) In the above method the treatment of step IV preferably takes 24 hours, in particular in anhydrous alcohol. After step IV amorphous and porous glass filler comprising glass particles of certain distance with retentive function are achieved.

(41) Optionally silanization of the particulate glass filler, in particular performing salinization of the glass filler after step IV before drying, can be carried out. Silanization preferably is performed in a rotary evaporator. The slurry with an anhydrous alcohol and the welded filler are filled into the rotary flask, a suitable silane hydrolysate is added and followed by evaporating the alcohol (calculation of silane hydrolysate: 0.00965weight of silanzed fillersurface area). Finally, silanized inventive particulate glass filler is removed from the flask and grinded, in particular by special rolling machine, and then sieving, preferably through a 100 mesh sieve, and keep it about 12 hours before final drying (step V). Thus, a silanized particulate glass filler comprising glass particles, wherein the glass particles contain centrally located macro particles with connections to micro particles located on the outer surface of the macro particles, wherein the connections consist of the material of said particles, and wherein the refractive index n of the glass particles is in the range of n=1.50 to 1.60.

(42) In another embodiment the inventive method comprises the steps Steps I to V as described above, steps VI is preformed by VI A treating the slurry with a suitable silane hydrolysate followed by evaporating the alcohol; VI B grinding in a rolling machine; VI C sieving, optionally through a 100 mesh sieve; VI D optionally keeping the product for about 12 hours; VI E and finally drying.

(43) A most preferred embodiment of the inventive method comprises Step I: Dispersing 3 kg glass filler into the miller (10 L) with 5 mm ZrO.sub.2 ball 12 kg and plus 3200 g water and 0.1% alcohol, 30 rpm for 24 hours, Drying the glass filler in a vacuum drying machine, Step II-III: Sintering and welding using the above described temperature curve using Nabertherm N30/85HA, Step IV: Dispersing by means of a special ultrasonic dispersing machine with 150 g of the welded filler in 1750 ml anhydrous alcohol, wherein the dispersing takes 24 h, Silanization as described above with a suitable silane hydrolysate, and Step V: Drying under 105 C. for 8 hours.

(44) Another object of the invention is a method of improving gloss stability while maintain abrasions resistance in dental composite materials by incorporating therein a particulate glass filler comprising glass particles, wherein the glass particles contain centrally located macro particles with connections to micro particles located on the outer surface of the macro particles, wherein the connections consist of the material of said particles, and wherein the refractive index n of the glass particles is in the range of n=1.50 to 1.60.

(45) By means of the described method particulate glass filler as previously described, in particular providing high gloss, improved translucency and advantageous radio-opacity of the resulting dental materials, is achieved.

(46) The sintering temperature depends on the type of the glass filler particles and generally is between 450 to 1000 C. The temperature is selected such that during sintering the particles start to melt. Preferably, the macro particle starts to melt so that the micro particle will be retained when the micro particles adhere to the melted surface of the macro particle. At this point the macro particles only start to melt whereas micro particle keep solid because of their higher transition temperature. Consequently, the connection between the centrally located macro particle and bound micro particles is preferably built of the dental glass material of said macro particle as described above.

(47) In principle, any amorphous glass filler with a particle size of 0.2 to 0.6 m will be suitable. It may be commercially acquired as such, or produced by milling and sieving coarser glass particles.

(48) When the suitable solvent is an alcohol, it is preferably a low boiling alcohol such as ethanol, propanol or isopropanol. Ethanol is preferred.

(49) Suitable silane hydrolysates are known to the art-skilled person. 3-methacryloxypropyl-trimethoxysilane is preferred. The inventive welded fillers, in particular obtainable by the inventive method as described above, may be used in dental composites, suitably in amounts from 60 to 80, preferably from 65 to 75% by weight of the uncured composition.

(50) The statements made in regard to the micro-structure of the filler particles and their anchoring in the matrix as illustrated by the transmission electron micrograph shown in FIG. 1a and the detailed schematically image in FIG. 1b compared to the state of the art filler shown in FIG. 1c. The bright zones in FIG. 1a represent the filler particles, the dark zones the polymer matrix. It is evident that the shape of the filler particles gives many possibilities for anchoring in the matrix.

(51) The use of the above described inventive particulate glass filler, obtainable by the above described method, in dental materials, in particular in composites, is also an object of the invention.

(52) A further object of the invention is a dental material comprising the above described particulate glass filler comprising glass particles, wherein the glass particles contain centrally located macro particles of the above characteristics and micro particles of the above characteristics, wherein these micro particles are connected to the outer surface of the macro particles, or at least a glass filler obtainable by the above described method, wherein the dental material is an uncured or cured material.

(53) Preferably said inventive dental material possesses a gloss level greater than 30, in particular greater than 35, more particular greater than 40, 45, in the cured material.

(54) Preferably said inventive dental material possesses a reflection level greater than 4%, in particular greater than 4.5, more particular greater than 5.0, 6.0, in the cured material.

(55) Preferably said inventive dental material possesses a gloss level greater than 40, in particular greater than 45, in combination with a reflection level greater than 5%, in particular greater than 6.0% in the cured material. For example an embodiment of the inventive dental material comprising the above described glass filler having as the central macro particle GM27884 with a particle size of 0.4 m and GM31684 with a particle size of 0.18 m as the micro particle located on the outer surface of said macro particle exhibits a gloss level greater than 45 and an a reflection of greater than 6.0 (FIG. 1a, 1b).

(56) Advantages of dental materials, curable or cured, containing fillers according to the invention are:

(57) non slumping consistency and advantageous workability;

(58) fast polishability;

(59) high mechanical strength, as expressed by flexural strength and Young's modulus;

(60) low abrasion, as expressed by roughness values,

(61) high gloss stability, in particular permanent gloss stability, as expressed by high reflection, and

(62) build a radio-opaque dental material with advantageous handling properties, in particular modelling behavior and shape stability.

(63) Furthermore, as the invention allows higher filler loads compared to conventional fillers, it provides a way to raise X-ray opacity by using higher total amounts of barium-containing dental glass filler.

(64) To explain the invention in detail, the production of a particulate composite filler in accordance with the invention and a formulation containing the composite filler for use as a dental material which can be polymerized by irradiation with light will be described in the examples which follow. The flexural strength of the different cured dental materials with and without fillers according to the invention will be determined and compared. The values of Young's modulus, mean roughness and reflection will be presented. All percentages are by weight unless otherwise indicated.

EXAMPLES

(65) Methods

(66) Method for Measuring Gloss Level of Dental Materials

(67) A gloss testing device was used (angle 60) from BYK Gardner GmbH (82538 Geretsried, Germany). The mean value was achieved from 5 measurements per sample.

(68) Method for Measuring Reflection Level of Dental Materials

(69) A surface laser scanner system (OPM GmbH, 76275 Ettlingen, Germany) was used to analyse the surface structure and roughness. The reflection degree of the laser beam was used to evaluate the surface reflection level. The resolution was set to 100 P/mm.

(70) Tooth brush abrasion and ACTA method (poppy seed) were performed as described in ISO-TS14569-1/-2. The results are summarized in the following table 2 and 3.

Example 1

Production of the Filler

(71) Step 1: Milling

(72) Equipment: ball milling machine (the composition of the milling tank is the same basically as the glass filler) Process: put 3 kg glass filler into the miller (10 L) with 5 mm ZrO2 balls (12 kg), add 3200 g distilled water and 0.1% alcohol, rotate at 30 rpm for 24 hours;

(73) Step 2: Drying of the glass filler:

(74) The milled glass filler obtained in step 1 is dried in a conventional vacuum cold drying machine.

(75) Step 3: Sintering and welding process:

(76) Equipment: Nabertherm N30/85HA air circulation chamber furnace

(77) Process: The product obtained in step 2 is introduced into the furnace and heated up from the room temperature to 600 C. (5 C./minute) then to 700 C./710 C./720 C. (2 C./minute) and kept at this temperature for 2 hours; followed by cooling from 700 C./710 C./720 C. to 300 C. (2 C./minute) and cooling naturally to room temperature

(78) Step 4: Dispersing welded filler

(79) Equipment: special ultrasonic dispersing machine.

(80) Process: put 150 g of the welded filler obtained in step 3 into 1750 ml anhydrous alcohol and disperse for 24 hours.

(81) Step 5: Production of silanized filler

(82) Equipment: rotary evaporator.

(83) Process: Put the slurry with anhydrous alcohol with the welded filler as obtained in step 4 into the rotary flask, add suitable silane hydrolysate and evaporate alcohol (calculation of silane hydrolysate:0.00965weight of silanized fillersurface area); take out the filler from flask, grind by conventional rolling machine followed by sieving (100 mesh); keep for about 12 hours; put into drying cabinet at 105 C. for 8 hours.

Example 2

Tests in Composite Dental Material BHB, GM #201103

(84) Filler containing dental composite pastes wherein conventional fillers are exchanged for different fillers and filler combinations as shown below were mixed and polymerized by light in the presence of photoinitiators as known in the art. The compositions of the dental materials are summarized in table 1 below.

(85) Ingredients for the Test Results Displayed in FIGS. 2 and 3

(86) Bis-GMA: bisphenol-A-(di)methacrylate TEDMA, also known as TEGDMA: triethylenglycol-dimethacrylate NF 180: Very fine glass filler, grain size d50=180 nm, by Schott, Germany, particle size distribution: d50: 180+/30 nm, d99>/=500 nm Glass welded filler (695 C., 0.4p): Conventional barium silicate glass filler particles, mean diameter of the center particle is 0.4 m, welded in analogy to Example 1 at 695 C. Pre-polymer (or splint) Grinded polymer particles containing silanized pyrogenic silica, polymerized in the presence of a crosslinking methacrylate.

(87) TABLE-US-00001 TABLE 1 compositions VP110516/ VP110511/ VP110516/ 3 Ju 1 Ju 1 Ju 201103 [wt.-%] [wt.-%] [wt.-%] [wt.-%] Bowen 18.12 18.12 18.12 17.77 TEDMA 7.77 7.77 7.77 7.62 Campherchinon 0.05 0.05 0.05 0.05 Genocure EHA 0.06 0.06 0.06 0.06 GM 27884 UF 72.01 0 0 0 sil.200 m/Kulzer Silanized self- 0 72.00 0 55.88 welding filler. based on GM 27884 (d.sub.50 ~0.4 m). welding temperature 695 C. GM27884 NF 180- 0 0 72.00 18.63 Si03 Estic Microfill 2.00 2.00 2.00 0 Splitter total 100.00 100.00 100.00 100.00
The Glass Filler was Prepared by the Following Method Step I: Dispersing 3 kg glass filler into the miller (10 L) with 5 mm ZrO.sub.2 ball 12 kg and plus 3200 g water and 0.1% alcohol, 30 rpm for 24 hours. A ball milling machine was used, wherein the component of the milling tang is the same basically as the glass filler. Drying the glass filler in a vacuum drying machine, Step II-III: Sintering and welding was performed by means of Nabertherm N30/85HA with the following temperature curve: heating up from room temperature to 600 C. (5 C./minute) then to 700 C./710 C./720 C. (2 C./minute) and keep this temperature for 2 hours; cooling from to 700 C./710 C./720 C. to 300 C. (2 C./minute) and cooling naturally to room temperature (step III). Step IV: Dispersing by means of a special ultrasonic dispersing machine with 150 g of the welded filler in 1750 ml anhydrous alcohol, wherein the dispersing takes 24 h, Silanization of the particulate glass filler was carried out in a rotary evaporator. The slurry with an anhydrous alcohol and the welded filler was filled into the rotary flask, a suitable silane hydrolysate was added and followed by evaporating the alcohol (calculation of silane hydrolysate: 0.00965weight of silanzed fillersurface area). Finally, silanized inventive particulate glass filler was removed from the flask and grinded in a rolling machine and then was sieved through a 100 mesh sieve, and kept for about 12 hours before final drying (step V). Step V: Drying at 105 C. for 8 hours.

(88) The following composite pastes were polymerized and subjected to mechanical testing:

(89) Pastes mixed from: Bis-GMA/TEDMA liquid+glass welded filler (675 C., 0.4 m)+additionally NF 180, silanized Bis-GMA/TEDMA+72% NF 180+2% pre-polymer filler Bis-GMA/TEDMA+72% glass welded filler (675 C., 0.4 m)+2% pre-polymer filler Bis-GMA/TEDMA+72% conventional barium silicate glass filler (0.85 m)+2% pre-polymer filler (reference)
Ingredients for the Rest Results Displayed in FIGS. 4 to 7

(90) % Pre-polymer: as described above;

(91) % 0.85 m: conventional barium silicate glass filler, mean particle diameter 0.85 m

(92) % 0.4 m filler welded at various temperatures according to the invention

(93) % 0.85 m filler welded at various temperatures outside the scope of to the invention

(94) NF 180 as described above

(95) Bis-GMA/TEDMA monomer composition 70:30 as described above.

(96) Further Abbreviations:

(97) GM and 6 digit numbers: various batches

(98) BHB abbrevation for Heraeus affiliate company

(99) The following pastes were polymerized; and reflection and roughness were determined.

(100) TABLE-US-00002 BHB, GM, VP110516/3Ju VP110516/3Ju: 0.85 m glass particles (72% 0.85 m + 2% Pre-polymer) not welded, BHB, GM, VP110329/1Ju VP110329/1Ju: 0.85 m glass particles (70% 0.85 m + 5% Pre-polymer) not welded BHB, GM #20100723 20100723 0.85 m glass particles welded (76.5% 0.85 m/700 C. + 0.18 m) at 700 C. + 0.18 m glass particles welded at 700 C. BHB, GM VP101122/2 Ju, VP101122/2Ju: 0.85 m glass particles (70% 0.85 m/700 C. + 2% Pre-polymer) welded at 700 C. BHB, GM, VP110328/1Ju, VP110328/1Ju: 0.85 m glass particles (70% 0.85 m/700 C. + 5% Pre-polymer) welded at 700 C. BHB, GM, VP110329/3Ju, VP110329/3Ju: 0.85 m glass particles (70% 0.85 m/710 C. + 5% Pre-polymer) welded at 710 C. BHB, GM, VP110329/4Ju, VP110329/4Ju: 0.85 m glass particles (70% 0.85 m/730 C. + 5% Pre-polymer) welded at 730 C. BHB, GM #201103 #201103 0.4 m glass particles welded at (56% 0.4 m/695 C. + 18.5% 0.18 m) 695 C. within the scope of the invention BHB, GM, VP110511/1Ju VP110511/1Ju 0.4 m: glass particles (72% 0.4 m/695 C. + 2% Pre-polymer) welded at 700 C. BHB, GM, VP110516/1Ju Defined as below (72% 0.18 m + 2% Pre-polymer) BHB, GM, VP110329/2Ju Defined as below (70% 0.18 m + 5% Pre-polymer) Durafill VS A2, # 010214 Defined as below (reference)

(101) TABLE-US-00003 TABLE 2 Tooth Brush Abrasion (see FIGS. 4 and 5) GM27884 Welding Mean Particle size temperature roughness Reflection Gloss Material [m] [ C.] [m] [%] level BHB, GM, VP110516/3Ju 0.85 0.48 4.0 15.8 (72% 0.85 m + 2% Pre-polymer) BHB, GM, VP110329/1Ju 0.85 0.65 3.2 11.4 (70% 0.85 m + 5% Pre-polymer BHB, GM #20100723 0.85 700 0.43 4.0 19.5 (76.5% 0.85 m/700 C. + 0.18 m) BHB, GM, VP110328/1 Ju (70% 0.85 700 0.57 3.3 14.7 0.85 m/700 C. + 5% Pre-polymer BHB, GM, VP110329/3 Ju (70% 0.85 710 0.61 3.6 15.3 0.85 m/710 C. + 5% Pre-polymer BHB, GM, VP110329/4 Ju (70% 0.85 730 0.56 3.4 14.1 0.85 m/730 C. + 5% Pre-polymer according to the invention 0.4 695 0.49 6.4 47.4 BHB, GM#201103 (56% 0.4 m/695 C. + 18.5% 0.18 m BHB, GM, VP110511/1 Ju (72% 0.4 0.4 695 0.64 5.3 37.5 m/675 C. + 2% Pre-polymer) BHB, GM, VP110516/1 Ju (72% 0.18 1.08 7.1 31.9 0.18 m + 2% Pre-polymer BHB, GM, VP110329/2 Ju (70% 0.18 1.05 6.2 32.1 0.18 m + 5% Pre-polymer Durafill VS, A2, #010214 (reference) 0.60 7.1 36.5

(102) TABLE-US-00004 TABLE 3 ACTA method (poppy seed) (FIGS. 6 and 7) GM27884 welding Mean Lost particle size temperature depth volume Material [m] [ C.] [m] [mm.sup.3] BHB, GM, VP110516/3Ju 0.85 33.6 0.2778 (72% 0.85 m + 2% Pre-polymer) BHB, GM, VP110329/1Ju 0.85 32.5 0.2939 (70% 0.85 m + 5% Pre-polymer) BHB, GM #20100723 0.85 700 36.0 0.3470 (76.5% 0.85 m/700 C. + 0.18 m) BHB, GM, VP101122/2Ju, 0.85 700 35.9 0.3307 (70% 0.85 m/700 C. + 2% Pre-polymer) BHB, GM, VP110328/1Ju, (70% 0.85 700 37.5 0.3670 0.85 m/700 C. + 5% Pre-polymer) BHB, GM, VP110329/3Ju, (70% 0.85 710 33.4 0.2988 0.85 m/710 C. + 5% Pre-polymer) BHB, GM, VP110329/4Ju, (70% 0.85 730 35.4 0.3354 0.85 m/730 C. + 5% Pre-polymer) according to the invention 0.4 695 39.3 0.3871 BHB, GM #201103 (56% 0.4 m/695 C. + 18.5% 0.18 m) BHB, GM, VP110511/1Ju (72% 0.4 695 39.9 0.3865 0.4 m/695 C. + 2% Pre-polymer) BHB, GM, VP110516/1Ju 0.18 45.6 0.4334 (72% 0.18 m + 2% Pre-polymer) BHB, GM, VP110329/2Ju 0.18 43.3 0.4271 (70% 0.18 m + 5% Pre-polymer)
Discussion of the Results: Flexural Strength and Young's Modulus (FIG. 2, FIG. 3):

(103) The compositions within the scope of the invention comprising 0.4 m filler according to the invention show superior values for of flexural strength and Young's modulus as compared to conventional filler materials. The filler-combination of welded filler according to the invention and pre-polymer (splint) is the strongest composition in both tests.

(104) Discussion of Results: Mean Roughness and Reflection (FIG. 4, FIG. 5)

(105) One can see that compositions a little outside the scope of the invention (1.8 m, black and checked bars on the extreme right of the diagrams show good reflection values, but at the cost of high roughness.

(106) In contrast the results for the compositions containing 0.4 m welded filler according to the invention (horizontally and vertically striped bars on the right of the diagrams surprisingly provide optimal balancing of good abrasion resistance (i.e. low roughness) and good reflection. The remaining compositions represented by the first six bars from the left of the diagrams are state of the art compositions which show good abrasion resistance but low reflection values.

(107) The glass filler [BHB, GM, VP110516/1 Ju (72% 0.18 m+2% Pre-polymer] and [BHB, GM, VP110329/2 Ju (70% 0.18 m+5% Pre-polymer] both show a good reflection of 6.2/7.1% but their mean roughness of 1.08/1.05 m is not satisfactory (table 2).

(108) [BHB, GM, VP110511/1 Ju (72% 0.4 m/675 C.+2% Pre-polymer)] exhibits a worse reflection of 5.3% compared to the above described fillers but shows a lower mean roughness of 0.64%.

(109) Durafill (reference) exhibits a good reflection of 7.1% but its mean roughness of 0.60 m and gloss level of 36.5 are not as good as compared to the inventive glass filler.

(110) In contrast the glass filler according to the invention [BHB, GM#201103 (56% 0.4 m/695 C.+18.5% 0.18 m] exhibits a good reflection of 6.4% and at the same time a very low mean roughness of 0.49 m which is lower than the higher mean roughness values of previously described fillers.

(111) Additionally, the inventive glass filler exhibits a gloss level of 47.4 which is significantly higher than the gloss level of [BHB, GM, VP110516/1 Ju (72% 0.18 m+2% Pre-polymer], [BHB, GM, VP110329/2 Ju (70% 0.18 m+5% Pre-polymer] or [BHB, GM, VP110511/1 Ju (72% 0.4 m/675 C.+2% Pre-polymer)] with 31.9/32.1/37.5 (see table 2).

(112) Thus, the inventive glass filler comprising macro glass particles of 0.4 m and micro particles of 0.18 m, obtained by the inventive method, surprisingly provides optimal balancing of an improved abrasion resistance (i.e. low roughness) and good reflection as well as a higher gloss level compared to the known fillers as described above.

(113) The remaining compositions represented by the first six bars from the left of the diagrams are state of the art compositions which show comparable mean roughness (FIG. 5) with the inventive glass filler but low reflection values (FIG. 4) and significantly worse gloss values (table 2).

(114) Discussion of Results: Mean Depth and Lost Volume (Table 3, FIGS. 6 and 7)

(115) The glass filler according to the invention [BHB, GM#201103 (56% 0.4 m/695 C.+18.5% 0.18 m] exhibits a reduced depth of 39.3 m and reduced lost of volume of 0.3871 mm.sup.3 compared to state of the art glass filler combined with pre-polymer on the outer surface of the macro particles [BHB, GM, VP110516/1 Ju (72% 0.18 m+2% Pre-polymer] and [BHB, GM, VP110329/2 Ju (70% 0.18 m+5% Pre-polymer] showing a mean depth of 45.6/45.3 m and lost of volume of 0.4334/0.4271 mm.sup.3 (table 3).

(116) Summary of Test Results

(117) In summary the compositions with 0.4 m welded glass particles show optimal balance between mechanical strength and reflection (gloss stability) and have very good mechanical strength.