NZ196864A

NZ196864A - Polymerisable dental composition containing a methacrylate monomer

Info

Publication number: NZ196864A
Application number: NZ196864A
Authority: NZ
Inventors: S C Temin; M C Richards
Original assignee: Colgate Palmolive Co
Priority date: 1980-04-29
Filing date: 1981-04-16
Publication date: 1984-04-27
Also published as: PH17044A; ZA812567B; IE810958L; NO158991C; DK189781A; ATA187781A; IE51152B1; CA1223696A; NL8102128A; MX156002A; GB2075035A; AU6991181A; SE450547B; NO811448L; NO158991B; AT376125B; DK157727B; ES8206560A1; ES501695A0; BE888599A

Description

<div class="application article clearfix" id="description"> New Zealand Paient Spedficaiion for Paient Number 1 96864 1CK c Priori • - *■'» t ■ ■, •• & ^ ■ ¥~ • $° • I i'Jt 3«. » 4—'•-.>*.-- • taciaiiaaaaaatata Compl^io G-p«csOcatjcn Filed: Lk^. Class: PubHczCon Date: . ,?.7. APR J984 P.O. Jaumzl, No: ?l Patents Form No. 5 Number PATENTS ACT 1953 COMPLETE SPECIFICATION DENTAL COMPOSITIONS &We COLGATE-PALMOLIVE COMPANY of 300 Park Avenue, New York, N.Y.10022, United States of America, a company organised under the laws of the state of Delaware, United States of America do hereby declare the invention for which X/we pray that a Patent may be granted to uw^us, and the method by which it is to be performed, to be particularly described in and by the following statement: - 1 - 1 if*N # 10 15 20 25 The invention relates in general to polymerizable dental compositions and particularly to such compositions capable of undergoing a rapid rate of cure to produce a product polymerizate having a relatively higher quantity of insoluble component. Polymerizable dental compositions based on the use of methacrylate monomers, e.g. the reaction product of the bis glycidyl ether of bis phenol A and methacrylic acid (hereinafter designated BIS-GMA), are commonly used as fillings, pit and fissure sealants and are advantageously adapted to a wide variety of dental restorative techniques. Such compositions typically include one or more methacrylate monomers.and at least one component of a free radical liberating (redox) polymerization system for said monomer(s). Usually, the monomer composition so formulated includes the peroxy type catalyst (oxidant) which is later contacted with the reducing agent (reductant) shortly prior to dental use. Upon contact of the oxidant with the reductant compositions, usually for convenience provided as pastes, polymerization occurs leading to the formation of a polymerizate having the physical properties necessary to the maintenance of good structural integrity within the oral cavity, e.g. high compressive strength, high degree of insolubles, etc.. The latter condition is highly desirable to minimize leaching out of vital ingredients and consequent deterioration of the polymerizate. /■ I > I ! -2- Rapid and complete curing are thus highly desirable objectives. To some extent, increase in catalyst concentration enhances curing rate; however, correlative enhancement in the degree of cure does not necessarily obtain. In fact, it is often the case that large catalyst concentrations impair the degree of cure thus producing a relatively- larger percentage of soluble and leachable components in the final polymerizate. Moreover, larger amounts of peroxy catalyst increase the possibility of pre-polymerization of methacrylate monomer, i.e. prior to contact with reductant thereby often necessitating the use of adjuvants, often in unusually large amounts having a stabilizing or polymerization retardant effect. However, such retardant effects are inevitably manifest to some extent during monomer-oxidant-reductant contact thereby depressing the cure rate and, unavoidably the degree of cure. Accordingly the invention in its broader aspects provides a polymerizable dental composition and process for using samethe composition having an accelerated curing rate and high degree of cure comprising at least one methacrylate monomer having 2 to k polymerizable double bonds^ from about 19-6S-8-4- 0 to 400% by weight based on said monomer of inorganic particulate filler, from about 0 to 5% by weight based on said monomer of silane coupling agent, an effective catalyst - activating amount of accelerator comprising cupric ion and from about 0.5 to 5% by weight based on said monomer of compound selected from (a) free radical liberating polymerization catalyst comprising an organic peroxy compound, (b) reducing agent for said peroxy compound and (c) mixtures of (a) and (b), and wherein the concentration (b) does not exceed about 40% by weight of the total quantity of (a) and (b). Cupric ions are most conveniently supplied in the form of copper salts with organic and inorganic acids. Particularly preferred materials for use herein include, without necessary limitation, cupric acetate, cupric acetyl acetonate, cupric chloride, and cupric sulfate. The compounds may be used singly or in admixture comprising two or more. In addition, cuprous ion maybe present with the foregoing, although the cupric compounds are found to be generally more effective as regards the obtention of both high degree and rate of cure. Accordingly, it is particularly preferred herein that cupric ion Cu++, constitute at least about 50% of the total copper ion used. However, and as will be hereinafter demonstrated, the use of cuprous salts alone provides significant improvement when compared to test runs omitting entirely the copper ion. Whether this is due to the presence of cupric ions invariably present in available cuprous salts or to the cuprous ion or to the combination has not been clearly estab- ic," 4 I */ ^ - r The amount of co'pper ion present in the monomer composition is exceedingly small generally ranging from about 5 to 100 ppm preferably 8 to 50 ppm based on total monomer. Otherwise stated, the amount of copper ion is at least that necessary to provide effective catalyst activating or accelerating effects. The term "total monomer" as. used herein refers to the total monomer which would be present at the time polymerization actually occurs. Thus, in accordance with a preferred embodiment, peroxy catalyst, monomer and filler if used are included in a first paste composition referred to as the "oxidant" paste and the reducing agent -for '•said peroxy catalyst is included in a second "reductant" paste preferably including the same components as the first paste except for the peroxy catalyst. The pastes are mixed shortly prior to dental use whereupon polymerization is initiated The copper ion may be added to either or both of the paste j compositions with its presence in the oxidant composition being most preferred. In any event, copper ion concentration in this embodiment has reference to the total monomer present in both the oxidant and reductant pastes. On the basis of catalyst, the concentration of copper ion ranges from about 0.02 to 0.4$ of the peroxy compound. Generally, it is preferred to add the copper compound to the fluid monomer system (absent filler) which is intended as the oxidant paste. The copper compound can be added to the composition by dispensing same in the normally liquid monomer(s) component. The roqirl r;j l;<; <1 1 rip or o"! on onn bo achieved by addlnp 1;lio copper compound to the monomer as a solution in a solvent preferably a polar organic solvent; of low. hoi linn point such as ether or lower alkanol, e.g. methanol. Since the solvent is merely a carrier for the copper compound it is most desirable that it be of high volability so that generally, most if not all of the solvent is removed in subsequent handling operations, e.g. mixing, etc. The amount of solvent used is quite low, thus to provide 80 ppm Cu++, and using only a 1% solution in methanol, the volume of solvent would be only 12.5% of monomer volume and 2.5% of a suitable paste on a weight basis. Alternatively, the copper compound may be sorbed onto the filler component, e.g. silica, should such material be used, for mixing with the monomer component(s). In addition to the copper compound, the preferred compositions herein are as follows: Parts by weight Monomer(s) 100 Inorganic particulate filler -0-100 t Silane coupling agent 0.5-5.0 Peroxy catalyst 0.5-5-0 Reducing agent 0.3-2.0 The methacrylate monomer is selected from materials having at least two, and preferably two to four polymerizable double bonds per molecule in order that the cured composite be crosslinked and thus better suited for use in the oral cavity. The most preferred monomers are those having two polymerizable double bonds per molecule. Desirable characteristics.for such monomers include low polymerization shrinkage, low exotherm during polymerization, low water sorption and the ability to cure rapidly and completely in the mouth. It is also desirable that the monomers be low In volatility and non-irritating to the tooth pulp. invention are those represented by the following general formulae: Methacrylate monomers particularly useful in this [ (M- A - 0)n - Ar ] - B (M - A - 0C0)2Ar I ' II (M - A) CR M R 2 (M - A - 0C0 - NH)2R m III IV V CH CH CH M 2 VI wherein M is methacryloyloxy, i.e. CH = C(CH )C00- ; 2 3 M' is methacryloyloxy or hydroxyl; A is alkylene having 1-3 carbon atoms, such as methylene, propylene, isopropylene 19686c hydrocyalkylene having 1-3 carbon atoms, such as hydroxy-methylene, 2-hydroxypropylene or acetoxyalkylene having 3-5 carbon atoms in the alkylene group such as 2-acetpxypropylene, 3-acetoxyamylene etc.; n is 1 to 1 preferably 1 or 2; m is 2 or 3 and p is 1 or 2 with the proviso that the sum of m and p is R is hydrogen, methyl, ethyl or -A-M wherein A and M are previously described; Ar is phenylene, e.g. o-phenylene, m-phenylene or p-phenylene, alkyl substituted phenylene, e.g. tolylene or 5-t-butyl-m-phenylene or cycloaliphatic having 6 to 10 carbon atoms such as 1,3-cyclohexylene; \ ^R B is . C . ^ wherein R and R are independently X \ u 5 X Vr5 hydrogen, alkyl e.g. to , or substituted alkyl and R' is alkylene having 2 to 12 carbon atoms such as ethylene, dodecylene etc., or -R^(O-R^) OR- wherein R^ is alkylene having 2 or 3 X carbon atoms such as ethylene, propylene or isopropylene and x is - 8 - 2 0 OCT 1983 RECEIVED 196864 zero to 5; and is phenylene, tolylene, methylene-bis-pheny-lene or alkylene having 2 to 12 carbon atoms. Monomers having the above formulae are well known and generally commercially available materials. Alternately, they are readily provided by conventional synthetic routes, for example, by reacting a phenolic compound such as diphenolic acid, phloroglucinol or bisphenol A with glycidyl methacrylate in the presence of various tertiary amines or by reacting methacrylic acid with an epoxide containing compound such as the diglycidyl ether of a bisphenol. Some of these monomers also are made by reacting appropriate alcohols with methacrylic acid, methacrylyl chloride or methacrylic anhydride. Illustrative monomers having these formulae include: CH2=C (CH3) COOCH2-OCO—^2y"COOCH2CH2OCOC (CH3) =CH2 C -fCH2OCOC (CH3) =CH214; CH-,CH_C i CH_0-C-C=CH„) ; J Z Z H I Z b ck3 CH2= C(CH3)COO(CH2)4OCOC(CH3)=CH2; CH2= C(CH3)COOCH2CH2OCH2CH2OCH2CH2OCOC(CH2)=CH2; CH2= C (CH3)COO— C (CH'3) —(^) O-COC (CH3)=CH2; CH2=C (CH3) COO-CH2CH (OH) CH9-O—^OCH0CH (OH)CH2OOOC(CH3)=CH2 CH2= C (CH3)COO-CH2CH2OCONH CH OCH2CH(OH)OCOC(CH3)=CH2 HCOOCH2CH2OCOC(CH3)=CH2 CH =C (CH.,) COO-CH-CH- 0CCNH-CHoCHoC-C--C-CHo—NHC00CH-CHo—CXX)-C (CHJ=CH0 Z J Z | Z Zi H | Z . Z Z CH CH CH CH i ■ *2. EXTENT OW** _9_ 2 0 OCT 1983 RECEIV'! 19686,4- Monomers having the formulae I, III, III and IV are preferred in the practice of this invention. Of these monomers, I, II and III are particularly preferred, monomers IV being employed more often in admixture with one or more of monomers I, II and III. Further useful monomers comprise: Other useful methacrylate monomers suitable for use in the practice of this invention include those having the following formulae wherein M and Ar are as previously described; 4 4 (MR OAr^CfCH^^ wherein R is ispropylene; (MR^OAr)2 and (MR^O)2Ar wherein R^ is 2-hydroxy- propylene; MA R^M wherein R^ is hydroxycyclopentyl or hydroxy- 8 8 cyclohexyl, and A is 2-hydroxyethylene; and M2R wherein R is: (A) CH" s >-c-( s ^ -CH2-(S)-CH2- CH2i§)"0i§^CH2- or (D> -ch2"<2^ch2- -10- HZ. PATENT pynca 20 OCT 1983 RECEIVED 1 9 ^ /f o 4 15 20 # Preparative? details .for many of those monomers are given in U.S. Patent Nos.3,066,112; 3,721,641; 3,730,9^7; 3,770,881 and 3,77') ,305. A tertiary outcctic monomer mixture also suitable for use in this invention is described in U.S. Patent No. 3,539,526. All of the aforementioned patents are herewith incorporated by reference in their entirety. It is to be understood that mixture of two or more appropriate methacrylate monomers are within the scope of this invention. In fact, depending on the choice of monomers, mixture are often highly desirable to optimize the characteristics of the resulting dental composition. Thus, it is preferred that the monomer or monomer blend have a viscosity of from about 100 to about 10,000 centi-poises as determined using a Brookfield viscometer at 20 rpm,at room temperature. The inorganic particulate filler employed in the compositions of this invention include fused silica, quartz, crystalline silica, amorphous silica, soda glass beads, glass rods, ceramic oxides, particulate silicate glass, radiopaque glasses(barium and strantium glasses), and synthetic minerals such as beta-eucryptic (LiAlSiO^), the latter having a negative coefficient of thermal expansion. It is also feasible to employ finely divided materials and powdered hydroxylapatite, although materials that react with silane coupling agents are preferred. Also available as a filler are colloidal or sub-rnicron silicas coated with a polymer. - 11 - 1 5 .0 15 io 25 Small amounts of pigments to allow matching of the composition to various shades of teeth can be included. Suitable pigments include iron oxide blacky cadmium yellows and oranges, fluorescent zinc oxides, titanium dioxide, etc.. The filler particles viould be generally smaller than about 50 microns in diameter and preferably smaller than 30 microns. It will be noted that the filler is an optional ingredient,unfilled formulations being employed where the dental composition is intended for use as a coating, malrgin sealant for amalgam restorations or adhesive. The silane coupling agents or keying agents are materials that contain at least one polymerizable double bond to react with the methacrylate monomers. Examples of suitable coupling agents are vinyl trichlorosilane, tris(acetoxy) vinyl silane, 1-N(vinylbenzylaminoethyl) aminopropyl trimethoxysilane-3 or 3-methacryloxypropyl trim-ethoxy silane. The last named1 Material is preferred for use with methacrylate monomers because of the similarity in reactivity of the double bonds. Peroxy catalysts useful herein and capable of initiating polymerization of the methacrylate monomer(s) are well known in the art for such use and include, without limitation, conventional peroxy as well as hydroperoxy compounds such as cumenc hydroperoxide, p-methane hydroperoxide, diisopropyl benzene hydroperoxide and t-butyl hydroperoxides. ■ « - 12 - ' c Hydroperoxides are the preferred species of organic peroxy polymerization catalyst with cumene hydroperoxide (CIIP) being particularly preferred. If desired, peroxide stabilizers such as ascorbic acid, maleic acid and the like may be included in small amounts. Reducing agents useful herein generally include any material capable of reacting with the peroxy compound to form polymerization initiating, free radical species as is known in the art. Particularly useful herein is a substituted thiourea having the formula: i ll X N G Z wherein X is H or Y and Y is alkyl having 1 to 8 carbon atoms, such as methyl, butyl, octyl; cycloalkyl having 5 or 6 carbon atoms such as cyclopentyl, cyclohexyl; chloro, hydroxy or mercapto substituted alkyl having 1 to 8 carbon atoms such as"chloroethyl, mereapto-ethyl, hydroxymethyl and chlorooctyl; alkenyl having 3 to 4 carbon atoms, such as allyl or methallyl; aryl having 6 to 8 carbons, such as phenyl or xylyl, and chloro-, hydroxy-, methoxy-, or sulfonyl substituted phenyl such as chlorophenyl,.phenylsulfonyl, hydroxyphenyl and methoxyphenyl; acyl having 2 to 8 carbon atoms such as acetyljbutyry1, octanoylj chloro or methoxy substituted acyl, such as chloroacetyl, chlorobenzoyl, chlorotoluoyl and methoxybenzoyl; aralkyl having 7 to 8 carbon atoms, such - 13 - 1 96 v • - - as benzyl, or chloro or methyl substituted aralkyl such as methoxybenzyl; and Z is NH^, NHX or NX . Examples of illustrative compounds suitable for use in the practice of this invention are methyl thiourea, isopropyl thiourea, butyl thiourea octyl thiourea, benzyl thiourea, acetyl thiourea, benzoyl thiourea, octanoyl thiourea, cyclohexyl thiourea, allyl thiourea, 1,1,3-triphenyl thiourea, 1,1,3-trimethyl thiourea, 2,4-xylyl thiourea, p-tolysulfony1 thiourea, l-octyl-3-phenyl thiourea, o-methoxyphenyl thiourea, m-hydroxyphenyl thiourea, 1,1-diallyl thiourea, 1,3-dially thiourea, 2-methallyl thiourea, o-methoxybenzyl thiourea, 1-(hydroxymethyl)-3-methyl thiourea, 1,1-dibutyl thiourea, 1,3-dibutyl thiourea, l-(p chloro phenyl)-3-methyl thiourea, 1 butyl-3-butyryl thiourea, l-acetyl-3-phenyl thiourea, 1 methyl-3-(p-vinylphenyl) thiourea, l-methyl-3-0 tolyl thiourea, l-methyl-3-pentyl thiourea, 3-methyl-l, 1-diphenyl thiourea and l-acetylr, 3-(2 metcaptoethyl) thiourea. While any of the aforementioned thioureas can be employed in the practice of this invention, preferred are the monosubstituted thioureas, that is, those having the aforementioned formula wherein X is H and Z is NH . Particularly preferred are i 2 I phenyl thiourea, acetyl thiourea and allyl thiourea. Preferably the composition contains about 0.5 to about 1% by weight of reducing agent. The following examples are given for purposes of _ in _ ) illustration only and are not to be considered as limiting the invention. EXAMPLES 1-14 Radiopaque reductant pastes having the following compositions are prepared: Ingredient 1NUPOL 2HMDMA 3A-174 Composition % by Weight j i ABCDEFGHj 10.27 10.24 10.27 10.27 10.27 10.27 10.27 10.2^ 10.27 10.24 10.27 10.27 10.27 10.27 10.27 10.2"/ 1.03 1.02 1.03 1.03 1.03 1.03 1.03' 1.0 Acetyl Thiourea 0.43 0.43 0.43 0.43 0.43 0.43 0.43 0.43 Ascorbic acid 4 „ ++ Cu ; 'Imsil A-10 0.07 -- .00022 .00044.0011 .0022 .0033-0044 41.86 41.86 41.86 41.86 41.86 41.86 41.86 41.86 'Corning 7724 TOTAL 36.14 36.14 36.14 36.14 36.14 36.14 36.14 36.14 100 100 100 100 100 100 100 100; 1 - Bis (GMA) 2 - 1.6 hexanedioldimethacrylate 3 ^ * - z-methacryloxy propyl trimethoxy silane - In the form cupric acetate added from methanol solution to monomer mixture c. - Amorphous silica (Illinois Minerals) - Barium Glass (Corning) Radiopaque oxidant pastes having the following compositions arc prepared. Composition % by weight Ingredient Nupol HMDMA A - 17 4 Naleic acid : v Ascorbic, acid Cumene hydroperoxide (80$) Imsil A-10 Corning 7724 Total Oxidant and reductant pastes respectively are mixed in a weight ratio of 1:1 as indicated in the following examples. Curing times are given in minutes and include time required for mixing, approximately 30 seconds. The cessation of the curing reaction is determined by the material no longer being indentable by a spatula. It can also be done by measuring the percent of polymerizate insoluble in methanol upon completion of the curing reaction. Samples of the polymer-forming mass are taken at timed intervals during the curing reaction; cessation of the latter is indicated by the point at which percent insolubles remains substantially constant. The results are summarized as follows: I. 9.94 9.94 0.99 0.07 1.05 41.93 36.06 100 .. Sk •- - 3-'--. . J 9.78 9.78 0.98 0. .41 • •' 1^0 5 41.79 36.22 100 - 16 - > 1C ^ < 4 \J v..' v,5 Example Oxidant Reductant PPM CU+*1' Cure Temp No. Paste Paste in Reductant Minutes on Paste 1 J C 2.2 3.5-4.3 21 2 II D 4.4 2.8-3.2 23 3 II E . 11.0 1.8-2.2 23 4 it F 22.0 1.7-2.2 20.5 5 II G 33.0 1.5-1.8 21.5 6 ii H 44.0 1.3-1.8 23 7 it A none 4.0-5.0 27 8 C 2.2 3.3-3.8 21 9 II D 4.4 2.7-3.5 22.5 10 II E 11.0 1.8-2.2 23 11 tt F 22.0 1.7-2.0 20.5 12 n G 33.0 1.3-1.7 21 13 II Ii 44.0 1.25-1.6 23 14 II A none 3.3-4.0 21 In each of the runs, curing is carried out in air, i.e. in an open vessel. Increased concentration of Cu"1"* provides more rapid cures. - 17 - 1 ~ 5 4 In comparison to Examples 7 and 14, which omit the copper accelerator, the data establish marked improvement in curing rate for the present invention. Similar combinations (1:1) of reductant paste B with I and J produce comparable results. EXAMPLES 15 ~ 17 The procedure of the foregoing examples is repeated but using a Nupol: HMDMA (71:29) by weight monomer blend in each of the oxidant and reductant compositions. Filler is omitted altogether in each of the examples. Copper ions are provided by the following compounds: Example No. Accelerator 15 cupric acetate 16 cupric chloride 17 cupric acetonyl acetonate (no solvent) In each case, improved rate of curing is achieved when compared to identical control runs omitting the copper compound. 18 - 1 O < A » K J , ■ -}• EXAMPLES 18 - 20 The procedure of Examples 15-17 Is repeated but using the following materials as accelerators: The results are similar to those of the preceding examples. EXAMPLES 21 - 34 Each of examples 1-14 is repeated with the exception that the cupric acetate is sorbed onto the filler and then added to the monomer composition. Similar improvement is obtained in curing rate by comparison with control runs omitting the copper compound. EXAMPLES 35-37 The following reductant-containing and oxidant-containing compositions are prepared: Example No. Accelerator (weight ratios) 20 18 19 cupric acetate/cupric chloride (50:50) cupric acetate/cuprous chloride (50:50) cupric chloride/cuprous chloride (50:50' - 19 - REDUCTANT Composition % by weight Ingredient NUPOL HMDMA Acetyl Thiourea Cu++ Corning 7724a IMSIL A-10a Colloidal Silica a. Silanized K 9.9 9.9 0.45 0.0002 36.25 42.25 1.30 L 9.9 9.9 0.45 0.0005 36.25 42.25 1. 30 M 9.9 9.9 0.45 0.0010 36.25 42.25 1. 30 OXIDANT COMPOSITION - N Ingredient NUPOL HMDMA CHP (801) Corning 7724a IMSIL A-10a Colloidal Silica ai Silanized Composition % by weight 9.325 9.325 1.05 36.25 42.25 1. 80 The Oxidant paste is mixed on a clean glass plate with each of the three reductant pastes in a 1:1 ratio. Curing times for each of three mixes are determined by the - 20 - </div>

Claims

<div class="application article clearfix printTableText" id="claims"> time required for the blended material to be resistant to indentation by a plastic spatula. The results are summarized as follows: PPM Cu++ in Reductant Curea Example No. Oxidant Paste Reductant Paste Paste Minutes 1 N K 2 4.2-5.0 2' N L 5 2.5-3.0 3 N M 10 2.3-2.8 a.• at 23°C In each of the above runs, curing is carried out in air. (Shorter curing times would result under glass or in a cavity covered by a matrix strip.) It is evident that increasing the concentration of Cu++ results in a shorter cure time. Similar results are obtained when the foregoing examples are repeated but utilizing, within the ranges hereinbefore specified the following peroxy catalysts and reductant compounds: peroxy catalysts - p-methane hydroperoxide, diisopropylbenzene hydroperoxide and t-butyl hydroperoxide; reductants-allyl thiourea, phenyl thiourea, and 3-allyl-l, 1-diethylthioureai,. - 21 - • 1 2 3 4 5 6 7 8 9 10 1 1 12 13 14 1 5 1 2 1 I 2 1 2 »3 1 I 96 6 84 WHAT WE CLAIM IS:

1. A polymerizable dental composition having an accelerated curing rate comprising at least one methacrylate monomer having 2 to 4 polymerizable double bonds, from 0 to 400% by weight based on said monomer of inorganic particulate filler, from 0 to 5% by weight based on said monomer of silane coupling agent, an effective catalyst -activating amount of accelerator comprising cupric ion and from 0.5 to 5.0% by weight based on said monomer of compound selected from (a) free radical liberating polymerization catalyst comprising an organic peroxy compound, (b) reducing agent for said peroxy compound and (c) mixtures of (a) and (b), and wherein the concentration of (b) does not exceed 40% by weight of the total quantity of (a) and (b).

2. A composition according to claim 1 wherein the ratio by weight of (a) to '(b) is 2:1.

3. A composition according to claim 1 wherein said reducing agent is a substituted thiourea compound.

4. A composition according to claim 3 wherein said reducing agent is an allyl or acetyl - substituted thiourea.

5. A composition according to claim 4 wherein reducing agent is acetyl thiourea. said peroxy compound is cumene hydropero> 22 1 96684 (>.

A composition according t.o claim k wherein r.nlil peroxy compound is cumene hydroperoxide and .'Jaid reducing agent is allyl thiourea.

7. A composition according to claim 1 wherein said cuprio ioti is present as cupric acetate, cupric acetyl acetonate, cupric chloride, or a mixture thereof.

8. A composition according to claim 1 wherein the concentration of said cupric ion is from 5 to 100 ppm based on said monomer.

9. A composition according to claim 1 wherein said cupric ion is dispersed in said monomer.

10. A composition according to claim 1 wherein at least 40% by weight of said monomer comprises the reaction product; of glycidyl methacrylate and bisphenol A.

11. A composition according to claim 10 wherein up to 60 /o by weight of said monomer is 1 ,6- hexanedioldimethacry-late.

12. A composition according to claim 1 includi up to 50% bv weight based on the weight of cupric ion of , " -• cuprous ion. I i4DEfMQ«? ng -23- \ \ ' V

13. A composition according to claim 1 having a pat c -.1 ikc c on r. i r> t c nc y.

14. A process for forming a dental polymerizate comprising contacting methacrylate monomer having 2 to 4 polymerizable double bonds with a redox polymerization catalyst capable of initiating the polymerization of said methacrylatc monomer and comprising organic3 peroxy compound and reducing agent therefor,said contacting being carried out in the presence of an effective catalyst activating amount of cupric ion. WEST-WALKER, McCABE per: ATTORNEYS FSR-THE APPLICANT -24- </div>