CA1145880A - Moulded dental fitments - Google Patents
Moulded dental fitmentsInfo
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- CA1145880A CA1145880A CA000303842A CA303842A CA1145880A CA 1145880 A CA1145880 A CA 1145880A CA 000303842 A CA000303842 A CA 000303842A CA 303842 A CA303842 A CA 303842A CA 1145880 A CA1145880 A CA 1145880A
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- polymers
- diisocyanate
- polyurethane
- diol
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Abstract
MOULDED DENTAL FITMENTS
Abstract of the Disclosure The invention provides moulded dental fittings prepared by the powder-liquid process, such as dentures, bridges, crowns and orthodontic appliances, based on polymethacrylates which have been elasticized with polyurethanes being used or co-used as the powder. The polymethylmethacrylates so elasticized are also in the preparation of synthetic teeth and can further be used as a component of materials for repairing dentures, bridges, crowns and orthodontic appliances, Le A 18 056
Abstract of the Disclosure The invention provides moulded dental fittings prepared by the powder-liquid process, such as dentures, bridges, crowns and orthodontic appliances, based on polymethacrylates which have been elasticized with polyurethanes being used or co-used as the powder. The polymethylmethacrylates so elasticized are also in the preparation of synthetic teeth and can further be used as a component of materials for repairing dentures, bridges, crowns and orthodontic appliances, Le A 18 056
Description
11~5880 The invention relates to moulded dental fittings, such as dentures, crcwns or bridges, with improved mechanical properties.
In most cases, dentures made of plastic are prepared by the pcwder-liquid process [Ger~an Patent Specification 737,058].
In this procedure, a bead polymer based on polymethacrylates is processed, with methacrylates, such as, for example, methyl methacrylate, to form a paste by stirring 2 to 3 parts of powder with 1 part of liquid. A
peroxide has been added to the manomer before preparing the paste, so that after the paste has been moulded it can be cured by heating, the monomer being polymerised.
Because the preparation pro oess for dentures, crcwns and bridges is easy to carry out, the powder-liquid process has become the standard technique for preparing plastic dentures. Furthermore, it is known to im-prove the pro oessability of dental beads in the powder-liquid prooe ss by using polymethyl methacrylate powder or, preferably, polymethyl methacrylate beads of a definite particle size, and it is also known to improve the pro-oe ssing spectrum of dental beads by using beads consisting of ccpolymers of methyl methacrylate with a major proportion of co~olymerised methacrylic acid methyl ester as the powder, instead of polymethyl methacrylate beads.
These variations make it possible to obtain the desired rapid prooe ssability together with the broad pro oessing spectrum which is also desired.
A disadvantage of the dentures, crowns and bridges based on poly-methyl methacrylates and prepared by the powder-liquid process is that the mechanical values of the raw material are not satisfactory for many struc-tures. In particular, in many cases the toughness properties of the plastics under load are not sufficient for dentures, crowns and bridges. Improving the impact strength of the plastic would have the effect of lowering the tendency of the dentures to brcak and also therefore of making it possLble to carry ou~ the cleaning opera~lon more reliably.
It has been found that moulded dental fittings prepared by the powder-liquid process, such as dentures, bridges, crowns and orthodontic appliances, based on polymethacrylates, have irnproved mechanical properties if polymethyl methacrylates which have been elasticized with polyurethanes are used or co-used as the powder.
The same also applies to synthetic teeth prepared in this manner. Polymethyl methacrylates elasticized with polyurethanes are also a suitable component of materials for rep~iring dentures, bridges, crowns and orthodontic appliances.
It is known to elasticize polymethyl methacrylates by polymerising the methyl methacrylate by the bulk polymerisation process, whilst simultaneously shaping. However, it was not to be expected that dentures with improved properties can be obtained if the powder-liquid process i9 used and a polymethyl methacrylate which contains a polyurethane as an elasticizing component is employed as the powder.
As is generally known, dental plastics which are obtained by the powder-liquid process are charac~erized by a particular structure. A multi-phase system, which can be detected by special methods, exists in the cured plastic: only some of the original "liquid" has penetrated into the powder particles during the initial swelling procedure. A
large; if not predominant, preportion of the liquid polyrnerises as a plia~e in itself and fills the intermediate spaces between the swoLlen original powder particles. The structure of moulded fittings which consist of polymethacrylates o-r modified Le A 18 056 - 3 -~5880 polymethyl methacrylates and which have been obtained by the powder-liquid process is thus substantially different to that of mouldsd fitments which consist of polymethyl methacrylates and which have been obtained by customary shaping processes.
It is indeed also known, from German Patent Specifica-tion 940,493, to improve the mechanical properties of moulded fittings consisting of methyl methacrylates, by using mixtures of different polymers or copolymers as the powder components.
For example, copolymers consisting of 80% of methyl methacrylate and 20% of butadiene are used for improving the flexural endurance. However, because of the butadiene content, copolymers of this type have a poor fastness to light.
Furthe more, it is known, from German Patent Specification 940~493, to use post-chlorinated polyvinyl chloride as an additive in order to improve the flexural impact strength and the flexural endurance of moulded fittings which are based on methyl methacrylate polymers and which have been ohtained by the power-liquid process. However, using post-chlorinated polyvinyl chlorides as an additive has the effect of lowering the resistance towards discolouration. Moreover, the stability of post-chlorinated polyvinyl chlorides is not sufficient when relatively active peroxides or relatively high polymerisation temperatures are used.
Moulded fittings for dental purposes, such as full and partial dentures, bridges, crowns or orthodontic appliances, based on organic plastics can be prepared by various procedures.
Thus, for example, it is possible to convert the plastic into the desired moulded fittings ~7ia an injection or extrusion process.
The moulded dental fittings, e.g. dentures, bridges, crowns or teeth, according to the invention are obtained by this process by shaping a new class of polymer, namely polyurethane-119~51380 elasticated polym~ethacrylates, optionally mixed with customary "injectable"
polymethyl methacrylates, by means of an injection devioe or by means of an extrusion device.
However, a particularly versatile process for the preparation of dentures, crcwns or bridges is the powder-liquid prooe ss. me moulded fitt-ings according to the invention are obtained by this process by using a poly-urethane-elasticized polymethacrylate as the powder. mese pcwders can be obtained by converting polyurethane-elasticized polymethacrylates into so-called "acrylate chips" via a comminuting process. However, particularly good results are obtained when those polyurethane-elasticized polymethacry-late powders which have been prepared by the procedure of a bead polymerisa-tion are used.
In addition to the better prooessability comçared with the acry-late chips, the use according to the invention of the eias~icized polymer beads additionally has the advantage that the elasticizing co~ponent is better protected against degradation by components in the medium of the mouth and is generally protected against the action of components in the medium of the mouth. In the dental ~eads, the polyurethane present as a separate phase is enveloped by the base substanoe of the dental beads, that is to say the polymethacrylate, and is thus protected from such action. In addition, the dental beads are themselves also in turn embedded in a matrix of polymethacrylate and are thus protected.
A particul æ embodlment of the proceduLe according to the inven-tion, for the preparation of dentures, crcwns or bridges by the powder-/
liquid process consists in setting up the desired processability and the re-quired processing spectrum by using elasticized dental beads of a definite particle size, 588~
or by adjusting the initial swelling behaviour of the polymer beads by using comonomers in the bead polymerisation. However, it is very particularly advantageous to set up the characteristic quantities of processability and processing spectrum, which are particularly important for handling from the point of view of dentistry, by adding non-elasticized beads. It was surprising that the good elasticizing activity of the dental beads is not lowered when the latter are used as a mixture with customary dental beads. The mixing ratios most favourable technologically must nevertheless be determined from case to case and depend on the construction and on the function of the denture or bridge.
Polymethacrylates in the sense of the present invention are understood as polymerisation products of methacrylic acid esters. In most cases, methacrylic acid methyl ester is the main component, but useful results are also obtained with poly-functional esters of methacrylic acid, and for specific purposes, good results are given by, for example, bis-GMA which is chemically bis-(2-hydroxy-3-methacryloyloxypropoxyl-phenyl-dimethylmethane or its modification products and also the comonomers mentioned in United States Patent 3,730,g47.
Polyurethanes in the sense of the present invention are understood as reaction products of polyols and polyisocyanates.
In particular those polyurethanes which are obtained from the diisocyanates below are of industrial interest:
A) aliphatic (particularly alkyl) diisocyanates having a branched carbon skeleton with 7 to 36 C atoms, for example
In most cases, dentures made of plastic are prepared by the pcwder-liquid process [Ger~an Patent Specification 737,058].
In this procedure, a bead polymer based on polymethacrylates is processed, with methacrylates, such as, for example, methyl methacrylate, to form a paste by stirring 2 to 3 parts of powder with 1 part of liquid. A
peroxide has been added to the manomer before preparing the paste, so that after the paste has been moulded it can be cured by heating, the monomer being polymerised.
Because the preparation pro oess for dentures, crcwns and bridges is easy to carry out, the powder-liquid process has become the standard technique for preparing plastic dentures. Furthermore, it is known to im-prove the pro oessability of dental beads in the powder-liquid prooe ss by using polymethyl methacrylate powder or, preferably, polymethyl methacrylate beads of a definite particle size, and it is also known to improve the pro-oe ssing spectrum of dental beads by using beads consisting of ccpolymers of methyl methacrylate with a major proportion of co~olymerised methacrylic acid methyl ester as the powder, instead of polymethyl methacrylate beads.
These variations make it possible to obtain the desired rapid prooe ssability together with the broad pro oessing spectrum which is also desired.
A disadvantage of the dentures, crowns and bridges based on poly-methyl methacrylates and prepared by the powder-liquid process is that the mechanical values of the raw material are not satisfactory for many struc-tures. In particular, in many cases the toughness properties of the plastics under load are not sufficient for dentures, crowns and bridges. Improving the impact strength of the plastic would have the effect of lowering the tendency of the dentures to brcak and also therefore of making it possLble to carry ou~ the cleaning opera~lon more reliably.
It has been found that moulded dental fittings prepared by the powder-liquid process, such as dentures, bridges, crowns and orthodontic appliances, based on polymethacrylates, have irnproved mechanical properties if polymethyl methacrylates which have been elasticized with polyurethanes are used or co-used as the powder.
The same also applies to synthetic teeth prepared in this manner. Polymethyl methacrylates elasticized with polyurethanes are also a suitable component of materials for rep~iring dentures, bridges, crowns and orthodontic appliances.
It is known to elasticize polymethyl methacrylates by polymerising the methyl methacrylate by the bulk polymerisation process, whilst simultaneously shaping. However, it was not to be expected that dentures with improved properties can be obtained if the powder-liquid process i9 used and a polymethyl methacrylate which contains a polyurethane as an elasticizing component is employed as the powder.
As is generally known, dental plastics which are obtained by the powder-liquid process are charac~erized by a particular structure. A multi-phase system, which can be detected by special methods, exists in the cured plastic: only some of the original "liquid" has penetrated into the powder particles during the initial swelling procedure. A
large; if not predominant, preportion of the liquid polyrnerises as a plia~e in itself and fills the intermediate spaces between the swoLlen original powder particles. The structure of moulded fittings which consist of polymethacrylates o-r modified Le A 18 056 - 3 -~5880 polymethyl methacrylates and which have been obtained by the powder-liquid process is thus substantially different to that of mouldsd fitments which consist of polymethyl methacrylates and which have been obtained by customary shaping processes.
It is indeed also known, from German Patent Specifica-tion 940,493, to improve the mechanical properties of moulded fittings consisting of methyl methacrylates, by using mixtures of different polymers or copolymers as the powder components.
For example, copolymers consisting of 80% of methyl methacrylate and 20% of butadiene are used for improving the flexural endurance. However, because of the butadiene content, copolymers of this type have a poor fastness to light.
Furthe more, it is known, from German Patent Specification 940~493, to use post-chlorinated polyvinyl chloride as an additive in order to improve the flexural impact strength and the flexural endurance of moulded fittings which are based on methyl methacrylate polymers and which have been ohtained by the power-liquid process. However, using post-chlorinated polyvinyl chlorides as an additive has the effect of lowering the resistance towards discolouration. Moreover, the stability of post-chlorinated polyvinyl chlorides is not sufficient when relatively active peroxides or relatively high polymerisation temperatures are used.
Moulded fittings for dental purposes, such as full and partial dentures, bridges, crowns or orthodontic appliances, based on organic plastics can be prepared by various procedures.
Thus, for example, it is possible to convert the plastic into the desired moulded fittings ~7ia an injection or extrusion process.
The moulded dental fittings, e.g. dentures, bridges, crowns or teeth, according to the invention are obtained by this process by shaping a new class of polymer, namely polyurethane-119~51380 elasticated polym~ethacrylates, optionally mixed with customary "injectable"
polymethyl methacrylates, by means of an injection devioe or by means of an extrusion device.
However, a particularly versatile process for the preparation of dentures, crcwns or bridges is the powder-liquid prooe ss. me moulded fitt-ings according to the invention are obtained by this process by using a poly-urethane-elasticized polymethacrylate as the powder. mese pcwders can be obtained by converting polyurethane-elasticized polymethacrylates into so-called "acrylate chips" via a comminuting process. However, particularly good results are obtained when those polyurethane-elasticized polymethacry-late powders which have been prepared by the procedure of a bead polymerisa-tion are used.
In addition to the better prooessability comçared with the acry-late chips, the use according to the invention of the eias~icized polymer beads additionally has the advantage that the elasticizing co~ponent is better protected against degradation by components in the medium of the mouth and is generally protected against the action of components in the medium of the mouth. In the dental ~eads, the polyurethane present as a separate phase is enveloped by the base substanoe of the dental beads, that is to say the polymethacrylate, and is thus protected from such action. In addition, the dental beads are themselves also in turn embedded in a matrix of polymethacrylate and are thus protected.
A particul æ embodlment of the proceduLe according to the inven-tion, for the preparation of dentures, crcwns or bridges by the powder-/
liquid process consists in setting up the desired processability and the re-quired processing spectrum by using elasticized dental beads of a definite particle size, 588~
or by adjusting the initial swelling behaviour of the polymer beads by using comonomers in the bead polymerisation. However, it is very particularly advantageous to set up the characteristic quantities of processability and processing spectrum, which are particularly important for handling from the point of view of dentistry, by adding non-elasticized beads. It was surprising that the good elasticizing activity of the dental beads is not lowered when the latter are used as a mixture with customary dental beads. The mixing ratios most favourable technologically must nevertheless be determined from case to case and depend on the construction and on the function of the denture or bridge.
Polymethacrylates in the sense of the present invention are understood as polymerisation products of methacrylic acid esters. In most cases, methacrylic acid methyl ester is the main component, but useful results are also obtained with poly-functional esters of methacrylic acid, and for specific purposes, good results are given by, for example, bis-GMA which is chemically bis-(2-hydroxy-3-methacryloyloxypropoxyl-phenyl-dimethylmethane or its modification products and also the comonomers mentioned in United States Patent 3,730,g47.
Polyurethanes in the sense of the present invention are understood as reaction products of polyols and polyisocyanates.
In particular those polyurethanes which are obtained from the diisocyanates below are of industrial interest:
A) aliphatic (particularly alkyl) diisocyanates having a branched carbon skeleton with 7 to 36 C atoms, for example
2,2,4- or 2,4,4-trimethyl-hexane-1,6-diisocyanate or industrial mixtures thereof, diisocyanates derived from esters of lysine or diisocyanates based on dimerised fatty acids, which are prepared in a known manner by conversion of dicarboxylic acids of this type with up to 36 C atoms into the corresponding diamines and subsequent l~S880 phos~cnation, B) cycloaliphatlc (particularly cycloalkyl hydrocarbon having 4 to 6 ring members) dLisocyanates, for example cyclobutane-1,3-diisocyanate, cyclohexane-1,3- and -1,4-cliisocyanate, 2,~-or 2,6-diisocyanato-1-methylcyclohexane or 4,4'-diisocyanato-dicyclohexylmethane, either in the form of the pure geometric isomers or an industrial mixtures thereof, an~ furthermore 1~
isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclollexane (i&o-phorone diisocyanate), and finally C) aliphatic (partlcularly alkyl)or cycloaliphatic (particularly cycloalkyl) diisocyanates whlch are modified by free radical graft copolymerisation wlth vinyl monomers and which are obtained by polymeri~ing in the presence of 100 parts of the diisocyanate of 10 to 100 parts, preferably methyl methacrylate, with the aid of a free radical polymerisation initiator, for example an organic peroxide, such as benzoyl peroxide, tert.-butyl peroctoate and the like, or an aliphatic azo compound, such as azoisobutyro-nitrile. In addition to the diisocyanates already mentioned, aliphatic (particularly alkyl) diisocyanates having a linear carbon chain, for example hexamethylene diisocyanate, are also suitable for use as the graft substrate. It has been shown that aliphatic diisocyanates modified in this manner lead to polyurethene-urea elastomers, wlich are soluble in monomeric methyl meth-acrylate to give a clear solution and give clear polymers when the refractive indices of the polymer phase and viscous phase are correctly matched.
Isophorone diisocyanate and hexamethylene diisocyanate or isophorone diisocyanate ~hich have been modified by graEt copolymerisation with methyl methacrylate and have a polymer content of up to 50%, preferably of up to 40V/o~ are preferably used.
Suitable polyols which can be used, accordin~ to the Le A 1~ 056 - 7 -ll~S880 present invention, for the preparation of the polyurethanes are longer-chain diols with 2 terminal hydroxyl groups. Polyesters, polyethers, polyaoetals or polycarbonates with m~lecular weights of 400 to 6,000 and a glass transi-tion temperature <20& are preferably used.
Suitable polyesters containing hydroxyl groups are, for example, reaction products of dihydric alcohols with dibasic carboxylic acids.
In the preparation of the polyurethanes to be used according to the invention, the hydroxyl ccmponent and the isocyanate ccmponent are not employed in equivalent amounts, but an excess of one or other component is used. In particulæ, in the prepolymer process, a polyurethane prepolymer which is free from QH groups and has NCO functional groups and which can still contain free diisocyanate is obtained in the first stage, and this is reacted in the second stage with the chain lengthener until the desired mole-cular weight is reached. A residue of free NCO groups usually remains in the product, and these are appropriately protected with the aid of a monofunc-tional chain stopper [component (C)]. Examples of suitable chain stoppers are lower aliphatic alcohols, such as methanol, ethanol, butanol or allyl alcohol.
Chain lengtheners for the polyurethanes to be used according to the invention include suitable short-chain compounds with 2 hydroxyl groups are, for e~ample: ethylene glycol, propylene 1,2- and 1,3-glycol, butylene 1,4-, 1,3- and 2,3-glycol, penta-1,5-diol, hexane-1,6-diol, heptane-1,7-diol, octane-1,8-diol, neopentyl-glycol, 1,4-bis-hydroxymethyl-cyclohexane, 2-methyl-propane-1,3-diol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycols with a molecular weight <400, dipropylene glycol, poly-propylene glycols with a lecular weight <400 dibutylene glyool, poly-~;~
.~
119~588~
butylene glycols with a molecular weight <400, 4,4'-dihydroxy-diphenylpro-pane or hydroqL mone-bis-(20 hydroxyethyl ether).
For their prooessing by the powder-/liquid process in dentistry, the polyurethane-elasticized polymethacrylates are mixed with a mono~er to form a paste. Methyl methacrylate is preferably used as the monomer. Mono-mers which contain two or more double bonds in the molecule (such as deriva-tives of acrylic and methacrylic acid) and which thus lead to crosslinking are added in order to increase the resistance to solvents and the abrasion resistan oe. The following oompounds, for example, can be added as crosslink-ing agents in amounts of about 0~1% by weight to 30% by weight, preferablyabout 1% by weight to 15~ by weight: ethylene glycol dimethacrylate, tri-ethylene glycol dimethacrylate, butanediol dimethacrylate, triacrylformal and the bifunctional comonomers mentioned in U.S. Patent 3,730,947.
The resulting CQmpOSitiOnS consisting of bead polymer and monomer can be cured using initiator systems, based on peroxides or aliphatic azo ecmpounds, which release free radicals. Examples of suitable polymerisation initiators are diacyl peroxides, such as, for example, dibenzoyl peroxide, or aIkylacyl peroxides, such as, for example, tertiary butyl perpivalate, option-ally in the presenoe of ac oelerators, such as aromatic tertiary amines, for example alkylated anilines, toluidines or xylidines. Cobalt salts or copper salts as well as oompounds frcn the barbiturate group and sulphinic acids and sulphones can also be used as acoe lerators.
Whilst curing at elevated temperature can be OE ried out by means of peroxides alone, such as dibenzoyl peroxide, chlorobenzoyl peroxide, toluyl peroxide or lauryl peroxide, or by means of free radical initiators _ g _ X
~1~5880 alone, such as, for example, azoisobutyric acid nitrile or azoisobutyric acid esters, it is neoe ssary to add acoe lerators in the case of curing at 1GW
temperatures. About 0.01% by weight to 2% by weight of polymerisation initiator are required in the case of curing at elevated temperature. About 0.02% by weight to 5% by weight of polymerisation initiators and about 0.02%
by weight to 5% by weight of acoe lerators are required in the case of curing at lcw temperatures.
Example 1 Dental beads are prepared, in the presen oe of a polyurethane, by a pro oe ss for the bead polymerisation of methyl methacrylate.
MgCO3 is used as the dispersing agent in the bead polymerisation and a mixture of lauroyl peroxide and dicyclohexyl percarbonate in the ratio 1:1 is used as the peroxidic initiator in an amount of 0.73%, relative to methyl methacrylate used (% by weight). The methyl methacrylate aontained 9.9% of dissolved polyurethane.
The polyurethane is a "diol"-lengthened polyester-polyurethane based on a mixture of tw~ polyester-diols A and B.
Polyester-diol A consists of a polyester based on adipic acid, hexane-1,6-diol and neopentylglycol, with a hydroxyl number of 66.
Polyester B is a polyester based on ethylene glycol, adipic acid and phthalic anhydride, with a hydroxyl number of 64.
Polyester A (0.35 equivalent) and polyester B (0.15 equivalent) are reacted with isophorone diisocyanate (0.75 equivalent), and the chain is lengthened to the extent of 85% by means of butane-1,4-diol and terminated by means of 2-hydroxyethyl methacrylate. The polyurethane formation is catalysed by tin dioctoate.
X
11~5880 0.25% by weight of dibenzoyl peroxide are added to 15 parts by weight of the dental beads prepared in this manner and the mixture is made into a paste with 5.36 parts by weight of a liquid consisting of 94% by weight of methyl methacrylate and 6% by weight of ethylene glycol dimethacry-late. Sheets 2mm thick are pressed fram this paste and polymerisation is then carried out.
The polymerisation is carried out as follows: the water bath is heated to 70C in the course of 30 minutes, the temperature is kept constant for 30 minutes, the bath is then heated to loo& and this te~perature is kept constant for a further 30 minutes. m e cell is cooled in a water bath.
After remDving from the cell, test pieces are cut out of the sheet without heating the sheet. The test pie oes thus obtained are subjected to the Dynstat test according to DIN 53,452.
Test results: (in each case the mean value from 5 test pieces) Impact strength 30.4 kp/cm2 Bending angle 12.6 Flexural strength 981 kp/cm2 Ball indentation hardness 10" 1,355 kp/cm2 60" 1,249 kp/cm2 Dental beads elasticated by polyurethanes are also used in Examples 2, 3 and 4. These dental beads differ in that different polyurethanes are used as the elasticating agents in the bead polymerisation.
Ex2mple 2 The dental beads contain a polyurethane which is prepared using 1 equivalent of isophorane diisocyanate instead of 0.75 equivalent of iso-phorone diisocyanate. For lengthening, the chain is lengthened to the extent of 90% using butanediol.
~7 ~x5880 0.5% by weight of lauroyl peroxide is added to the beads obtained in this manner, the mixture is polymerised with a liquid consisting of 97%
by weight of methyl methacrylate and 3~ by weight of triethylene glycol dimethacrylate and the polymer is subjected to the strength test according to DIN 53,452:
Impact strength 32.0 kp/cm2 Bending angle 23.4 FJexural strength 1,315 kp/cm Ball indentation hardness 10" 1,249 kp/cm 60" 1,137 kp/cm2 Example 3 The dental beads used are also obtained as described in Example l;
a polyester-polyurethane which is prepared using 1.25 equivalents of iso-phorone diisocyanate and the chain of which is lengthen~d to the extent of 90% using butane-1,4-diol is employed as the elasticating polyurethane.
0.1% by weight of dichlorodibenzoyl peroxide is added to the beads obtained in this manner, the mixture is polymerised with a liquid consisting of 90~ by weight of methyl methacrylate and 10% by weight of trimethylolpro-pane trimethacrylate and the polymer are subjected to the strength test according to DIN 53,452:
Impact strength 49.1 kp/cm Bending angle 16.6 Flexural strength 1,086 kp/cm Ball indentation hardness 10" 1,360 kp/cm2 60" 1,252 kp/cm2 Example 4 The dental beads used are elasticated with a polyurethane which has been prepared using 1.5 equivalents of X
~58t30 isophorone dilsocyanate and the chain of which has been lengthened to the extent of 90% using butane-1,4-diol.
1% by weight of Ditoluyl peroxide i.s added to the bead polymers obtained in this manner, is mixture polymeriscd with a liquid consisting of 88% by weight of methyl methacrylate and 12% by weight of butanediol dimethacrylate and the polymer is subjected to the strength test according to DIN 53,452:
Impact strength 27.3 kp/cm2 Bending angle 16.8 Flexural strength 1,267 kp/cm2 Ball indentation hardnes~ 10" 1,517 kp/cm2 60" 1,385 kp/cm2 Example 5 1% by weight of bls-4-chloro-benzoyl peroxide is added to 4 parts by weight of the dental beads prepared according to Example 1 and the mixture is made lnto a paste with 3 parts by weight of a liquid consisting of 94% by weight of methyl meth-acrylate, 6% by weight of ethylene glycol dimethacrylate and 0.7% by weight of N,N'-dimethyl-p-toluidine. A pourable consistency is obtaîned with this mixing ratio. A knead-able consistency is obtained with a mixing ratio of 4.7 parts by weight of powder and 2 parts by weight of liquid. The polymerisation has ended after 16-17 minutes at 23C.
The test pieces described in Example 1 are subjecte~ to the Dynstat test according to DIN 53,452. Test results:
(in each case the mean value from 5 test pieces) Impact strength 27.4 kp/cm2 Flexural strength 1,005 kp/cm2 Bending angle 28.8 Ball indentation hardness 101' lt327 kp/cm2 60" 1,137 kp/cm2 Le A 18 056 - 13 - `
l~S880 ocmparison As a control experiment, customary methyl methacrylate beads con-taining 0.25~ by weight of dibenzoyl peroxide are polymerised with a liquid consisting of 94% of methyl ~ethacrylate and 6% by weight of ethylene glycol dimethacrylate and the polymer is subjected to the strength test according to DIN 53,452:
Impact strength 19.4 kp/cm2 Bending angle 18 Flexural strength 1,059 kp/cm2 Ball indentation h ædness 10" 1,249 kp/cm2 60" 1,158 kp/cm2 'X
isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclollexane (i&o-phorone diisocyanate), and finally C) aliphatic (partlcularly alkyl)or cycloaliphatic (particularly cycloalkyl) diisocyanates whlch are modified by free radical graft copolymerisation wlth vinyl monomers and which are obtained by polymeri~ing in the presence of 100 parts of the diisocyanate of 10 to 100 parts, preferably methyl methacrylate, with the aid of a free radical polymerisation initiator, for example an organic peroxide, such as benzoyl peroxide, tert.-butyl peroctoate and the like, or an aliphatic azo compound, such as azoisobutyro-nitrile. In addition to the diisocyanates already mentioned, aliphatic (particularly alkyl) diisocyanates having a linear carbon chain, for example hexamethylene diisocyanate, are also suitable for use as the graft substrate. It has been shown that aliphatic diisocyanates modified in this manner lead to polyurethene-urea elastomers, wlich are soluble in monomeric methyl meth-acrylate to give a clear solution and give clear polymers when the refractive indices of the polymer phase and viscous phase are correctly matched.
Isophorone diisocyanate and hexamethylene diisocyanate or isophorone diisocyanate ~hich have been modified by graEt copolymerisation with methyl methacrylate and have a polymer content of up to 50%, preferably of up to 40V/o~ are preferably used.
Suitable polyols which can be used, accordin~ to the Le A 1~ 056 - 7 -ll~S880 present invention, for the preparation of the polyurethanes are longer-chain diols with 2 terminal hydroxyl groups. Polyesters, polyethers, polyaoetals or polycarbonates with m~lecular weights of 400 to 6,000 and a glass transi-tion temperature <20& are preferably used.
Suitable polyesters containing hydroxyl groups are, for example, reaction products of dihydric alcohols with dibasic carboxylic acids.
In the preparation of the polyurethanes to be used according to the invention, the hydroxyl ccmponent and the isocyanate ccmponent are not employed in equivalent amounts, but an excess of one or other component is used. In particulæ, in the prepolymer process, a polyurethane prepolymer which is free from QH groups and has NCO functional groups and which can still contain free diisocyanate is obtained in the first stage, and this is reacted in the second stage with the chain lengthener until the desired mole-cular weight is reached. A residue of free NCO groups usually remains in the product, and these are appropriately protected with the aid of a monofunc-tional chain stopper [component (C)]. Examples of suitable chain stoppers are lower aliphatic alcohols, such as methanol, ethanol, butanol or allyl alcohol.
Chain lengtheners for the polyurethanes to be used according to the invention include suitable short-chain compounds with 2 hydroxyl groups are, for e~ample: ethylene glycol, propylene 1,2- and 1,3-glycol, butylene 1,4-, 1,3- and 2,3-glycol, penta-1,5-diol, hexane-1,6-diol, heptane-1,7-diol, octane-1,8-diol, neopentyl-glycol, 1,4-bis-hydroxymethyl-cyclohexane, 2-methyl-propane-1,3-diol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycols with a molecular weight <400, dipropylene glycol, poly-propylene glycols with a lecular weight <400 dibutylene glyool, poly-~;~
.~
119~588~
butylene glycols with a molecular weight <400, 4,4'-dihydroxy-diphenylpro-pane or hydroqL mone-bis-(20 hydroxyethyl ether).
For their prooessing by the powder-/liquid process in dentistry, the polyurethane-elasticized polymethacrylates are mixed with a mono~er to form a paste. Methyl methacrylate is preferably used as the monomer. Mono-mers which contain two or more double bonds in the molecule (such as deriva-tives of acrylic and methacrylic acid) and which thus lead to crosslinking are added in order to increase the resistance to solvents and the abrasion resistan oe. The following oompounds, for example, can be added as crosslink-ing agents in amounts of about 0~1% by weight to 30% by weight, preferablyabout 1% by weight to 15~ by weight: ethylene glycol dimethacrylate, tri-ethylene glycol dimethacrylate, butanediol dimethacrylate, triacrylformal and the bifunctional comonomers mentioned in U.S. Patent 3,730,947.
The resulting CQmpOSitiOnS consisting of bead polymer and monomer can be cured using initiator systems, based on peroxides or aliphatic azo ecmpounds, which release free radicals. Examples of suitable polymerisation initiators are diacyl peroxides, such as, for example, dibenzoyl peroxide, or aIkylacyl peroxides, such as, for example, tertiary butyl perpivalate, option-ally in the presenoe of ac oelerators, such as aromatic tertiary amines, for example alkylated anilines, toluidines or xylidines. Cobalt salts or copper salts as well as oompounds frcn the barbiturate group and sulphinic acids and sulphones can also be used as acoe lerators.
Whilst curing at elevated temperature can be OE ried out by means of peroxides alone, such as dibenzoyl peroxide, chlorobenzoyl peroxide, toluyl peroxide or lauryl peroxide, or by means of free radical initiators _ g _ X
~1~5880 alone, such as, for example, azoisobutyric acid nitrile or azoisobutyric acid esters, it is neoe ssary to add acoe lerators in the case of curing at 1GW
temperatures. About 0.01% by weight to 2% by weight of polymerisation initiator are required in the case of curing at elevated temperature. About 0.02% by weight to 5% by weight of polymerisation initiators and about 0.02%
by weight to 5% by weight of acoe lerators are required in the case of curing at lcw temperatures.
Example 1 Dental beads are prepared, in the presen oe of a polyurethane, by a pro oe ss for the bead polymerisation of methyl methacrylate.
MgCO3 is used as the dispersing agent in the bead polymerisation and a mixture of lauroyl peroxide and dicyclohexyl percarbonate in the ratio 1:1 is used as the peroxidic initiator in an amount of 0.73%, relative to methyl methacrylate used (% by weight). The methyl methacrylate aontained 9.9% of dissolved polyurethane.
The polyurethane is a "diol"-lengthened polyester-polyurethane based on a mixture of tw~ polyester-diols A and B.
Polyester-diol A consists of a polyester based on adipic acid, hexane-1,6-diol and neopentylglycol, with a hydroxyl number of 66.
Polyester B is a polyester based on ethylene glycol, adipic acid and phthalic anhydride, with a hydroxyl number of 64.
Polyester A (0.35 equivalent) and polyester B (0.15 equivalent) are reacted with isophorone diisocyanate (0.75 equivalent), and the chain is lengthened to the extent of 85% by means of butane-1,4-diol and terminated by means of 2-hydroxyethyl methacrylate. The polyurethane formation is catalysed by tin dioctoate.
X
11~5880 0.25% by weight of dibenzoyl peroxide are added to 15 parts by weight of the dental beads prepared in this manner and the mixture is made into a paste with 5.36 parts by weight of a liquid consisting of 94% by weight of methyl methacrylate and 6% by weight of ethylene glycol dimethacry-late. Sheets 2mm thick are pressed fram this paste and polymerisation is then carried out.
The polymerisation is carried out as follows: the water bath is heated to 70C in the course of 30 minutes, the temperature is kept constant for 30 minutes, the bath is then heated to loo& and this te~perature is kept constant for a further 30 minutes. m e cell is cooled in a water bath.
After remDving from the cell, test pieces are cut out of the sheet without heating the sheet. The test pie oes thus obtained are subjected to the Dynstat test according to DIN 53,452.
Test results: (in each case the mean value from 5 test pieces) Impact strength 30.4 kp/cm2 Bending angle 12.6 Flexural strength 981 kp/cm2 Ball indentation hardness 10" 1,355 kp/cm2 60" 1,249 kp/cm2 Dental beads elasticated by polyurethanes are also used in Examples 2, 3 and 4. These dental beads differ in that different polyurethanes are used as the elasticating agents in the bead polymerisation.
Ex2mple 2 The dental beads contain a polyurethane which is prepared using 1 equivalent of isophorane diisocyanate instead of 0.75 equivalent of iso-phorone diisocyanate. For lengthening, the chain is lengthened to the extent of 90% using butanediol.
~7 ~x5880 0.5% by weight of lauroyl peroxide is added to the beads obtained in this manner, the mixture is polymerised with a liquid consisting of 97%
by weight of methyl methacrylate and 3~ by weight of triethylene glycol dimethacrylate and the polymer is subjected to the strength test according to DIN 53,452:
Impact strength 32.0 kp/cm2 Bending angle 23.4 FJexural strength 1,315 kp/cm Ball indentation hardness 10" 1,249 kp/cm 60" 1,137 kp/cm2 Example 3 The dental beads used are also obtained as described in Example l;
a polyester-polyurethane which is prepared using 1.25 equivalents of iso-phorone diisocyanate and the chain of which is lengthen~d to the extent of 90% using butane-1,4-diol is employed as the elasticating polyurethane.
0.1% by weight of dichlorodibenzoyl peroxide is added to the beads obtained in this manner, the mixture is polymerised with a liquid consisting of 90~ by weight of methyl methacrylate and 10% by weight of trimethylolpro-pane trimethacrylate and the polymer are subjected to the strength test according to DIN 53,452:
Impact strength 49.1 kp/cm Bending angle 16.6 Flexural strength 1,086 kp/cm Ball indentation hardness 10" 1,360 kp/cm2 60" 1,252 kp/cm2 Example 4 The dental beads used are elasticated with a polyurethane which has been prepared using 1.5 equivalents of X
~58t30 isophorone dilsocyanate and the chain of which has been lengthened to the extent of 90% using butane-1,4-diol.
1% by weight of Ditoluyl peroxide i.s added to the bead polymers obtained in this manner, is mixture polymeriscd with a liquid consisting of 88% by weight of methyl methacrylate and 12% by weight of butanediol dimethacrylate and the polymer is subjected to the strength test according to DIN 53,452:
Impact strength 27.3 kp/cm2 Bending angle 16.8 Flexural strength 1,267 kp/cm2 Ball indentation hardnes~ 10" 1,517 kp/cm2 60" 1,385 kp/cm2 Example 5 1% by weight of bls-4-chloro-benzoyl peroxide is added to 4 parts by weight of the dental beads prepared according to Example 1 and the mixture is made lnto a paste with 3 parts by weight of a liquid consisting of 94% by weight of methyl meth-acrylate, 6% by weight of ethylene glycol dimethacrylate and 0.7% by weight of N,N'-dimethyl-p-toluidine. A pourable consistency is obtaîned with this mixing ratio. A knead-able consistency is obtained with a mixing ratio of 4.7 parts by weight of powder and 2 parts by weight of liquid. The polymerisation has ended after 16-17 minutes at 23C.
The test pieces described in Example 1 are subjecte~ to the Dynstat test according to DIN 53,452. Test results:
(in each case the mean value from 5 test pieces) Impact strength 27.4 kp/cm2 Flexural strength 1,005 kp/cm2 Bending angle 28.8 Ball indentation hardness 101' lt327 kp/cm2 60" 1,137 kp/cm2 Le A 18 056 - 13 - `
l~S880 ocmparison As a control experiment, customary methyl methacrylate beads con-taining 0.25~ by weight of dibenzoyl peroxide are polymerised with a liquid consisting of 94% of methyl ~ethacrylate and 6% by weight of ethylene glycol dimethacrylate and the polymer is subjected to the strength test according to DIN 53,452:
Impact strength 19.4 kp/cm2 Bending angle 18 Flexural strength 1,059 kp/cm2 Ball indentation h ædness 10" 1,249 kp/cm2 60" 1,158 kp/cm2 'X
Claims (28)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Moulded dental fittings based on polymethacrylates, characterized in that polymethacrylates which are elasticized by polyurethanes are used.
2. A process for the preparation of molded dental fittings by polymerizing a paste comprising a) a liquid monomer, b) a fine-particled organic filler based on a polymethacrylate and c) a polymerization initiator, characterized in that the organic filler comprises a polymethacrylate which is elasticized by a polyurethane.
3. A process as claimed in claim 2 wherein the liquid monomer is a methacrylic acid ester.
4. A process as claimed in claim 2 characterized in that polyurethane-elasticized fine-particled polymethacrylates which are obtained in the form of polymer beads by the bead polymerization procedure are used as the organic filler.
5. A process as claimed in claim 2 characterized in that polyurethane-elasticized polymethyl methacrylates which have been obtained in the form of acrylate chips via a grinding process are used as the organic filler.
6. A process as claimed in claim 2 wherein the polyurethane is a reaction product of a diisocyanate, and a long-chain diol with a molecular weight of 400 to 6000.
7. A process as claimed in claim 2 wherein the polyurethane is a reaction product of a diisocyanate, a long-chain diol with a molecular weight of 400 to 6000 and a short-chain diol or a mono-functional chain stopper, or both such a diol and such a chain stopper.
8. A process as claimed in claim 6 or 7 wherein the diisocyanate is selected from the group of hexamethylene diisocyanate, isophorone diisocyanate and isophorone diisocyanate grafted with methyl methacrylate.
9. A process as claimed in claim 6 or 7 wherein the long-chain diol has a glass transition temperature less than or equal to 20°C.
10. A process as claimed in claim 2, 6 or 7 wherein the polyurethane is prepared by a prepolymer process comprising the chain extension of a prepolymer containing functional NCO groups.
11. A process as claimed in claim 7 wherein the chain stopper is a lower aliphatic alcohol.
12. A process as claimed in claim 2 wherein the monomer comprises methyl methacrylate.
13. A process as claimed in claim 2, 3 or 12 wherein the monomer includes from 0.1 to 30% by weight of a crosslinking agent.
14. A process as claimed in claim 2, 3 or 12 wherein the monomer includes from l to 15% by weight of a crosslinking agent.
15. Elasticized polymers characterized in that they are polymethacrylates elasticized by polyurethanes.
16. Polymers as claimed in claim 15 wherein the polyurethane is a reaction product of a diisocyanate and a long-chain diol with a molecular weight of 400 to 6000.
17. Polymers as claimed in claim 15 wherein the poly-urethane is a reaction product of a diisocyanate, a long-chain diol with a molecular weight of 400 to 6000 and a short-chain diol or a mono-functional chain stopper, or both such a diol and such a chain stopper.
18. Polymers as claimed in claim 16 or 17 wherein the diisocyanate is selected from the group of hexamethylene diisocyanate, isophorone diisocyanate and isophorone diisocyanate grafted with methyl methacrylate.
19. Polymers as claimed in claim 16 or 17 wherein the long-chain diol has a glass transition temperature less than or equal to 20°C.
20. Polymers as claimed in claim 15, 16 or 17 wherein the polyurethane is prepared by a prepolymer process comprising the chain extension of a prepolymer containing functional NCO
groups.
groups.
21. Polymers as claimed in claim 17 wherein the chain stopper is a lower aliphatic alcohol.
22. Elasticized bead polymers characterized in that the polymers are polymethacrylates elasticized by polyurethanes.
23. Polymers as claimed in claim 22 wherein the polyurethane is a reaction product of a diisocyanate, a long-chain diol with a molecular weight of 400 to 6000.
24. Polymers as claimed in claim 22 wherein the polyurethane is a reaction product of a diisocyanate, a long-chain diol with a molecular weight of 400 to 6000 and a short-chain diol or a mono-functional chain stopper, or both such a diol and such a chain stopper.
25. Polymers as claimed in claim 23 or 24 wherein the diisocyanate is selected from the group of hexamethylene diisocyanate, isophorone diisocyanate and isophorone diisocyanate grafted with methyl methacrylate.
26. Polymers as claimed in claim 23 or 24 wherein the long-chain diol has a glass transition temperature less than or equal to 20°C.
27. Polymers as claimed in claim 22, 23 or 24 wherein the polyurethane is prepared by a prepolymer process comprising the chain extension of a prepolymer containing functional NCO
groups.
groups.
28. Polymers as claimed in claim 24 wherein the chain stopper is a lower aliphatic alcohol.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19772723604 DE2723604A1 (en) | 1977-05-25 | 1977-05-25 | DENTAL MOLDED BODY |
| DEP2723604.0 | 1977-05-25 | ||
| DE2745643A DE2745643C3 (en) | 1976-10-18 | 1977-10-11 | Platter arrangement |
| DEP274564.3 | 1977-11-05 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1145880A true CA1145880A (en) | 1983-05-03 |
Family
ID=25772059
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000303842A Expired CA1145880A (en) | 1977-05-25 | 1978-05-23 | Moulded dental fitments |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1145880A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5502087A (en) | 1993-06-23 | 1996-03-26 | Dentsply Research & Development Corp. | Dental composition, prosthesis, and method for making dental prosthesis |
-
1978
- 1978-05-23 CA CA000303842A patent/CA1145880A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5502087A (en) | 1993-06-23 | 1996-03-26 | Dentsply Research & Development Corp. | Dental composition, prosthesis, and method for making dental prosthesis |
| US5554665A (en) * | 1993-06-23 | 1996-09-10 | Dentsply Research & Development Corp. | Method and dispenser for making dental products |
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