Dentures and process for making the same

A denture comprising teeth consisting essentially of hard non-hydrophilic polyurethane elastomer imbedded in and chemically bonded to a gum member consisting essentially of soft non-hydrophilic polyurethane elastomer is prepared from a model assembly consisting of a wax replicate denture (artificial teeth imbedded in a wax pattern) mounted on a mouth model, which assembly is usually provided by a dentist or dental technician after a series of dental impressions, bites, and trials with the patient. A female mold is prepared from the model assembly having a cavity conforming to the wax replicate denture which, together with the mouth model after the wax replicate denture has been removed, forms a denture mold. The hard non-hydrophilic polyurethane elastomer teeth are first cast in the cavity of the mold. The casting is then removed and trimmed of its flash down to the gum line to delineate the shape of that portion of the teeth to be imbedded in the gum portion of the denture and replaced in the mold. The gum portion of soft non-hydrophilic polyurethane elastomer is then cast in and around the teeth with the mouth model in place, thereby forming a denture having exactly the same shape and configuration of the wax replicate denture originally provided.

BACKGROUND OF INVENTION 
1. Field of Invention 
This invention relates to novel dentures and to a method for preparing the 
same. It is particularly directed to novel dentures in which the teeth are 
formed of hard polyurethane elastomer and the gums of soft polyurethane 
elastomer. 
2. Prior Art 
It has been proposed to provide dentures with a soft layer in contact with 
the gums and other mouth parts to provide tissue relief. Such soft layers 
have been composed of acrylics, silicones, and like rubber-like materials. 
But on aging, such soft layers tend to harden and give off undesirable 
odors. In addition, some decomposition of the polymer may also occur 
presumably due to an oxidation process as well as to pH fluctuations 
within the mouth. 
Also, in order to provide a unitary structure in which the teeth are firmly 
imbedded in the gum portion of the dentures, various types of holding 
means such as pins, rods, diotorics, that is, undercut channels or holes, 
are provided so that the teeth become firmly imbedded in the denture 
material. 
OBJECTS OF THE INVENTION 
It is an object of the invention to overcome difficulties heretofore 
encountered in the prior art. It is a further object of the invention to 
provide dentures in which the teeth are chemically bonded into the denture 
material. It is a further object of the invention to provide a denture in 
which the teeth are imbedded in a soft polyurethane elastomer. Still other 
objects are to provide dentures which are inexpensive, trouble free, and 
easy to keep clean. Further objects will appear as the description 
proceeds. 
BRIEF DESCRIPTION OF THE INVENTION 
The invention consists of a denture comprising teeth consisting essentially 
of hard non-hydrophilic polyurethane elastomer having a hardness of not 
less than about Shore D 40, imbedded in and chemically bonded to a gum 
member consisting essentially of soft non-hydrophilic elastomer having a 
hardness of not greater than about Shore A 65 and to a process for making 
the same in which a model assembly comprising a wax replicate denture 
(artificial teeth imbedded in a wax pattern) mounted on a mouth model as 
prepared by a dentist or dental technician after a series of dental 
impressions, bites, and trials with the patient, is coated with release 
material and imbedded in investment material to form a female mold or 
investment having a cavity corresponding to the wax replicate denture. 
Hard non-hydrophilic polyurethane elastomer-forming material is then 
poured into the mold to a depth above the gum line but below the gum 
engaging portion of the denture to be formed and caused to set up to form 
hard non-hydrophilic polyurethane elastomer. The casting is removed and 
trimmed of its flash down to the gum line to delineate the shape of that 
portion of the teeth to be imbedded in the gum portion of the denture and 
replaced in the mold. The wax replicate denture is then removed from the 
mouth model and the exposed gum engaging portion of the wax model is then 
coated with release compound. The mouth model and the female mold are then 
assembled to form a denture mold and soft non-hydrophilic polyurethane 
elastomer-forming material is introduced thereinto by suitable sprue holes 
and caused to set up therein to form soft non-hydrophilic polyurethane 
elastomer gum portion integrally chemically bonded into a unitary mass to 
the hard non-hydrophilic polyurethane elastomer teeth with which it is in 
contact. The cast dentures are then removed from the mold and finished as 
needed, for example, by removing the sprues and polishing. 
For forming the female mold, any suitable investment material may be used. 
It has been found according to the invention, however, that it is of 
advantage to use a rigid polyurethane foam-forming material because it is 
simple to mix up such material, inject it into the mold cavity and allow 
it to set up therein. It has the advantage of providing a light, strong 
investment which, unlike plaster or investment compound, can be easily 
broken away from the cast denture and sprues, if necessary, to effect 
removal of the dentures from the mold. The rigid polyurethane foam also 
provides a dimensionally stable mold. Any of the so-called one-shot or 
foam-in-place formulations can be utilized. 
Suitable pigments and/or dyes can be incorporated in the polyurethane 
elastomer-forming material as may be needed to give the desired color to 
the teeth and gums. 
Polyurethane elastomers of varying degrees of hardness and elasticity are 
known in the art. They include both the simple urethane polymers and the 
urethane copolymers, such as urethane-urea copolymers. Any of these known 
polyurethane polymers can be utilized for the purposes of this invention 
provided the components are not colored or at least the resulting product 
is not colored in such a way that the desired coloring of the teeth and 
gums cannot be obtained by the introduction of pigments and dyes. Also, 
provided that the elastomers are not hydrophilic and provided they have a 
degree of hardness consonant with the purposes of the invention. The hard 
non-hydrophilic polyurethane elastomers should have a hardness of at least 
Shore D 40 and up to about Shore D 70, whereas the soft non-hydrophilic 
polyurethane elastomer should not have a hardness greater than about Shore 
A 65 and preferably at least about Shore A 15. Preferred non-hydrophilic 
elastomers are those formed by isocyanate-terminated prepolymers which are 
cross-linked or cured by mixing with a cross-linking agent and heating as 
required to effect curing. 
Isocyanate-terminated prepolymers suitable for preparing the hard 
non-hydrophilic polyurethane elastomers (hard prepolymers) are prepared by 
the reaction of polyether diols or triols with aliphatic or cycloaliphatic 
or aralkyl di- or polyisocyanates in proportion to give free NCO groups. 
The prepolymers are then cured or cross-linked with a diol, polyol, an 
alkanolamine, a diamine or a tertiary amine containing polyol, or blends 
thereof. Advantageously, the diol or polyol is a polyether diol or polyol 
or a hydroxyl-terminated prepolymer. 
The polyether diols can be selected from poly-(oxypropylene) glycols, 
poly-(oxypropylene)poly-(oxyethylene) glycols, poly-(1,4-oxypropylene) 
glycols, graft copolymers of poly-(oxypropylene)-(polyoxyethylene) glycols 
with acrylonitrile or mixtures of acrylonitrile and styrene ("Polymer 
Polyols"). The equivalent weight of these polyether diols may range 
between 200 to 1000 with a preferred range of 200 to 400. The polyol may 
consist of simple polyfunctional alcohols such as glycerine, 
trimethylolpropane, 1,2,6-hexanetriol, or pentaerythritol, or they may 
consist of polyether triols such as poly(oxypropylene) or 
poly(oxyethylene) adducts of the above polyols. The equivalent weight of 
the polyether polyols may range between 100 and 800 with a preferred range 
of 100 and 500. It is also understood that various combinations of diols 
and polyols may be used. 
Isocyanate-terminated prepolymers suitable for preparing the soft 
polyurethane elastomers (soft prepolymers) are based on polyether diols 
alone or combinations of polyether diols or triols, and aliphatic, 
cycloaliphatic or aralkyl di- or polyisocyanates. The same diols and 
polyols as described above may be used but the average equivalent weight 
is significantly higher than that used in the preparation of the hard 
polymer. The preferred range of equivalent weight of the polyethers (diols 
or combination of diols and triols) is 450 to 1500. They are cured in the 
same way as the hard prepolymers. 
The diisocyanates used for the preparation of the hard or soft 
isocyanate-terminated prepolymers may be selected from the following, 
although they are not necessarily restricted to these examples: 
4,4'-Dicyclohexylmethane diisocyanate, isophorone diisocyanate, 
2,2,4-trimethyl-1,6-hexane diisocyanate, hexamethylene diisocyanate, 
xylylene diisocyanate, "dimeryl" diisocyanate, methylcyclohexyl 
diisocyanate and the reaction product of 3 moles of hexamethylene 
diisocyanate with 1 mole of water (Desmodur N-triisocyanate). 
The ratio of NCO to OH in the preparation of the soft isocyanate-terminated 
prepolymer may range between 1.75 to 2.5 with a preferred range of 2.0 to 
2.25, while the NCO/OH of the hard isocyanate-terminated prepolymer may 
range between 2 to 3. The soft isocyanate-terminated prepolymers should 
have a free NCO content of about 3.5 to 5.5 percent, preferably, 3.7 to 
4.7 percent, and the hard isocyanate-terminated prepolymers, a free NCO 
content of about 9.5 to 14 percent, preferably, 10 to 13 percent. 
For the curing (crosslinking) of the soft or hard prepolymers, preferred 
polyols are tertiary amine- containing polyols such as poly(oxypropylene) 
or poly(oxyethylene) adducts of diamines or triamines, such as 
ethylenediamine, diethylene triamine, tolylenediamine, phenylenediamine, 
or aniline, or any diols, polyols or their blends. Advantageously, they 
are polyols of relatively low molecular weight such as are obtained by 
condensing propylene oxide with ethylenediamine or pentaerythritol to a 
molecular weight of about 500, or of trimethylolpropane or any other base 
compound to a molecular weight up to 2500. 
Another preferred curing or crosslinking agent is a hydroxyl-terminated 
prepolymer. These are prepared essentially the same way as the 
isocyanate-terminated prepolymers but the ratio is such that there are 
free and un-reacted hydroxyl groups. The same diols and polyol and 
isocyanates can be used, though it is preferred that the prepolymer have a 
functionality greater than 2, which can be obtained by using a polyol 
having a functionality greater than 2 and/or an isocyanate having a 
functionality greater than 2. Advantageously, the isocyanate is 
2,2,4-trimethyl-1,6-hexane diisocyanate, hexamethylene diisocyanate and 
Desmodur N. 
The ratio of OH/NCO in the hydroxyl-terminated prepolymers, advantageously, 
may be in the same range as the NCO/OH ratio in the isocyanate-terminated 
prepolymers. It will be understood, however, that inasmuch as the 
cross-linking agent may consist of one or more diols or polyols (no 
isocyanate), the ultimate OH/NCO ratio is infinity. 
Another preferred curing or crosslinking agent is a prepolymer-polyol 
blend. Thus, a polyurethane prepolymer, advantageously, one having neither 
free NCO nor free OH groups, can be mixed with a polyol, advantageously a 
polyol having a functionality of more than 2, to form a prepolymer-polyol 
blend. When such a blend is mixed with an isocyanate-terminated prepolymer 
in a NCO/OH ratio of greater than 1, crosslinking is effected both through 
an NCO--OH reaction and through NCO-urethane reaction. 
The isocyanate-terminated prepolymers and the cross-linking agent should be 
mixed together in proportions to give an NCO/OH ratio of at least about 
1.05 to 1.0 and preferably not greater than 1.1 to 1.0. This excess of NCO 
groups ensures a crosslinked polymer which is non-hydrophilic and one 
which is sufficiently reactive so that the soft non-hydrophilic 
polyurethane elastomers react chemically with the hard non-hydrophilic 
polyurethane elastomers to form an integral and unitary chemical bond 
between the two. 
In order to accelerate the formation of the prepolymers or the cure of both 
the hard and soft isocyanate-terminated prepolymers with the crosslinking 
agents, metal catalysts such as tin catalysts, for example, dibutyltin 
dilaurate and stannous octanoate can be used.

DETAILED DESCRIPTION OF THE INVENTION 
As shown in the side elevation of FIG. 1 and in plan view in FIG. 2, 1 
represents a denture according to the invention, 2 the artificial teeth, 
and 3 the artificial gums in which teeth 2 are imbedded. The teeth 2 are 
composed of hard polyurethane elastomer and the gum 3 of soft polyurethane 
elastomer. The teeth 2 and the gum 3 are unitarily and integrally united 
by a chemical bond which results when the gum portion is cast in contact 
with the cast teeth. 
If desired, the teeth may be cast in contact with a re-inforcing element 4 
which has the shape of the teeth assembly. The re-inforcing element 4, 
advantageously, is also made of hard polyurethane elastomer, preferably 
freshly cast, and the teeth and the gum portions are unitarily and 
integrally bonded therewith. 
FIG. 3 shows a cross-section of the anterior portion and FIG. 4 is a 
cross-section of the posterior portion. 
By the techniques of this invention, the denture 1 has the shape and 
configuration of the wax replicate denture 10 prepared by the dentist or 
dental technician. The wax replicate denture 10 includes the wax pattern 
14, or gum portion, with the teeth 13 imbedded therein. The wax replicate 
denture 10 is positioned on the mouth model 12 and the whole constituting 
the model assembly is mounted in the upper half 11 of a flask 21. This 
model assembly is prepared in the usual manner after a series of dental 
impressions, bites, and trials with the patient so that the wax replicate 
denture represents exactly what the dentist wants the final dentures to be 
like. 
In preparing dentures from the model assembly, there is attached to the 
inner ends of the posterior portions of the wax pattern 14, wax sprues 15 
for the purpose of providing sprue holes into the mold cavity. These wax 
sprues should lie on, or be partially imbedded in the edges of the mouth 
model. (By edges of the mouth model is meant the portions extending beyond 
the actual impression of the gums or palate), and so shaped and so located 
that when the mouth model is removed for the investment mold, yet to be 
described, the cast denture and sprues can be easily removed. The entire 
exposed surface of the model assembly is then coated with a coating 16 of 
release material and the whole assembly inserted into the bottom half 22 
of the flask 21 as shown in FIG. 8. The bottom half of the flask is then 
filled with investment material 23 which is allowed to or caused to set 
up. On removal of the model assembly, there is left a female mold or 
investment having a cavity 24 which conforms to the shape of the wax 
replicate denture 10. 
If it is desired to provide re-inforcing element 4, it is fitted in the 
cavity in the desired position, for example, along the posterior side as 
shown in FIG. 9, or it may be imbedded in hard non-hydrophilic 
polyurethane elastomer-forming material, or simply laid on top of it, 
before it sets up. 
The cavity 24 now forms the mold for the teeth portion which are formed by 
filling the cavity 24 with hard non-hydrophilic polyurethane 
elastomer-forming material to the desired depth intermediate the gum line 
and the gum-engaging portion of the denture to be formed. This material is 
then either allowed to or caused to set up as shown in FIG. 9. The casting 
is then withdrawn from the mold and the flash 25a cut off to the dotted 
lines 25b, i.e., down to the gum line, to delineate the portion of the 
teeth to be imbedded in the gum portion. The cast teeth 25, thus modified, 
are reinserted into the cavity 24 as shown in FIG. 10. The wax replicate 
denture is then removed from the mouth model 12, the exposed portion 
thereof coated with release material 16a, and the two halves of the flask 
assembled as shown in FIG. 11. Mold cavity 24 is then filled with soft 
non-hydrophilic polyurethane elastomer-forming material which is then 
allowed to or caused to set up to form the soft non-hydrophilic 
polyurethane elastomer 27 which is the gum portion 3 of denture 1. 
It will be understood that the release material 16 and 16a is not actually 
as thick as shown since it is really nothing more than a coating of latex, 
silicone, shellac, zinc stearate, or the like. 
The investment material, advantageously, is a rigid polyurethane foam such 
as commonly used for insulation purposes. Two-component systems are 
readily available on the market which in a short time after mixing, will 
set up into a rigid blown foam. It is sufficient simply to mix the two 
components together and to inject a measured quantity into the mold cavity 
through suitable sprue holes, where in a few minutes or a few seconds, 
according to the time factor of the particular composition, it will begin 
to foam and will fill up the bottom half of the flask 21 into close and 
intimate contact with the model assembly therein. A hole, or holes, may be 
provided in a wall to the lower half of the flask to vent the flask and to 
provide for expansion in case too much of the foam-forming material is 
introduced into the flask cavity. The flask is placed in a suitable clamp 
(not shown), to assure that any pressure engendered by the blowing of the 
foam or any of the subsequent operations, will not disrupt the relative 
position of the upper and lower flasks. The size of the sprue holes and 
the vents can be adjusted to the amount of material introduced to cause 
more or less pressure to be exerted as the foam sets up. 
In contradistinction, the non-hydrophilic polyurethane elastomer-forming 
compositions or materials of the invention do not set up spontaneously and 
do not expand on setting up. Nonetheless, the flask should be tightly 
clamped to insure that a precise replication is obtained. The 
isocyanate-terminated polymers used in the invention are liquids or 
heat-liquefiable materials as are the cross-linking agents. When the two 
are mixed in the proper proportions at the proper temperature, the 
resulting liquid can be poured into or injected into the molds as required 
and there caused to set up by holding at a suitable temperature for a 
requisite period according to the time constant and cure constant of the 
particular system used. Suitable such systems are illustrated in the 
following Formulations and Examples in which the parts and percentages are 
by weight unless otherwise specified. 
I -- SOFT ISOCYANATE-TERMINATED PREPOLYMERS 
(Components A) 
______________________________________ 
FORMULATION 1 
______________________________________ 
Polymeg 1000.sup.1, 4 moles .times. 976 = 
3904 
Polymeg 2000.sup.2, 1 mole .times. 1998 = 
1998 
Hylene W.sup.3, 10 moles .times.262 = 
2620 
Dibutyltin dilaurate 
catalyst 1.7 
8523.7 
Equivalent weight per one NCO 
852.4 
______________________________________ 
Footnote: 
.sup.1 Poly(oxytetramethylene) glycol; Mol. wt. 976 
.sup.2 Poly(oxytetramethylene) glycol; Mol. wt. 1998 
.sup.3 4,4' dicyclohexylmethane diisocyanate 
PREATION PROCEDURE 
Polymeg 1000 and Polymeg 2000 are charged into the reactor and the mixture 
heated 70.degree. C. It is demoisturized in vacuum for 2-3 hours until the 
evolution of bubbles ceases. 
Afterwards a dry nitrogen blanket is applied and the mixture is cooled to 
50.degree. C and Hylene is added. The reaction mixture is stirred at 
100-120 rpm for at least 30 minutes and watched, for a slight exothermic 
reaction may ensue. The temperature of the reactor is maintained at 
65.degree.-70.degree. C. The catalyst is added in portions in order to 
speed up the reaction. After 3 hours have elapsed the NCO content is 
checked using the n-dibutylamine titration method. The NCO content should 
be in the range of 4.8%. The variation here and elsewhere may be .+-. 5 
percent. 
When this level of free NCO is reached, the contents of the reactor are 
cooled and are packaged into one gallon or one quart lined containers. Dry 
nitrogen is used to maintain an inert atmosphere in the containers which 
are then tightly closed. 
______________________________________ 
FORMULATION 2 
______________________________________ 
Polymeg 1000, 2 moles .times. 976 = 
1952 
Polymeg 2000, 1 mole .times. 1998 = 
1998 
Hylene W, 6 moles .times. 262 = 
1572 
Dibutyltin dilaurate 
catalyst 1.1 
5523.1 
Equivalent weight per one NCO 
920.5 
______________________________________ 
Preparation procedures are the same as in Formulation 1. The free NCO 
content of the prepolymer should be 4.56%. 
______________________________________ 
FORMULATION 3 
______________________________________ 
Polymeg 2000, 1 mole .times. 1998 = 
1998 
Polymeg 1000, 1 mole .times. 976 = 
976 
Hylene W, 4 moles .times. 262 = 
1048 
4022 
Equivalent weight per one NCO 
1005.5 
______________________________________ 
Preparation procedures are the same as in Formulation 1. The free NCO 
content should be 4.18%. 
______________________________________ 
FORMULATION 4 
______________________________________ 
Polymeg 2000 1198 
Polymeg 1000 488 
Hylene W 786 
Dibutyltin dilaurate, catalyst 
.76 
3272.76 
Equivalent weight per one NCO 
1190 
______________________________________ 
PREATION PROCEDURE 
Poly(oxytetramethylene) glycols, Polymeg 2000 and Polymeg 1000, are charged 
into a reactor and demoisturized in vacuum for 2-3 hours upon a gentle 
stirring of 60-120 rpm at 70.degree. C. 
The demoisturized glycol mixture is cooled down to 50.degree. C, a dry 
nitrogen blanket is applied, and diisocyanate (Hylene W) is added. The 
catalyst is added in portions in order to speed up the reaction. 
The charge of the reactor should exotherm. The temperature of the reactants 
should not be allowed to go over 75.degree. C. After 2-3 hours of the 
reaction, the NCO content should be checked by the n-dibutylamine 
titration method. The NCO content should be in the range of 3.3%. If the 
content of NCO higher than 3.7% is found, the heating should be continued 
for an additional hour at 70.degree. C after the addition of a small 
amount (0.005%) of the catalyst. 
The above soft isocyanate-terminated prepolymers are essentially linear. 
II -- HARD ISOCYANATE-TERMINATED PREPOLYMERS 
(Components A) 
______________________________________ 
FORMULATION 5 
______________________________________ 
Polymeg 650.sup.1, 1 mole = 
650 
Pluracol TP 440.sup.2, 1 mole = 
420 
Hylene W.sup.3, 7 moles = 
1834 
Dibutyltin dilaurate 
catalyst 0.6 
2904.6 
Equivalent weight per NCO 
322.7 
______________________________________ 
Footnote: 
.sup.1 Poly(oxytetramethylene) glycol; Mol. wt. 650 
.sup.2 Poly(oxypropylene) derivative of trimethylolpropane, Mol. wt. 420 
.sup.3 4,4' dicyclohexylmethane diisocyanate 
PREATION PROCEDURE 
Polymeg 650 and Pluracol TP 440 are charged into the reactor and the 
mixture is heated to 70.degree. C. It is then demoisturized under vacuum 
for 2-3 hours until the evolution of bubbles ceases. Afterwards a dry 
nitrogen blanket is applied, the mixture cooled to 40.degree. C and Hylene 
W added. The reaction mixture is stirred at 100-200 rpm for at least 30 
minutes, taking care to control any exothermic reaction which may occur. 
The temperature in the reactor is kept at a level of 65.degree.-70.degree. 
C. The catalyst is added in portions, if necessary, to speed up the 
reaction. 
After two hours have elapsed, the NCO content is checked by means of the 
n-dibutylamine titration method. The NCO content should be in the range of 
13%. When this level of free NCO is reached, the contents of the reactor 
are cooled and packaged into one gallon or one quart lined containers. The 
empty space in the containers is filled with dry nitrogen. 
______________________________________ 
FORMULATION 6 
______________________________________ 
Polymeg 650.sup.1, 2 moles .times. 650 = 
1300 
Pluracol TP 740.sup.2,1 mole .times. 720 = 
720 
Hylene W, 9 moles = 2358 
Dibutyltin dilaurate 
catalyst 0.9 
4378.9 
Equivalent weight per one NCO 
398.0 
______________________________________ 
Footnote: 
.sup.1 Poly(oxytetramethylene) glycol; Mol. Wt. 650 
.sup.2 Poly(oxypropylene) derivative of trimethylolpropane, Mol. wt. 720 
Preparation procedure is identical to the Formulation 5 procedure. The free 
NCO content should be 10.55%. 
The above hard isocyanate-terminated prepolymer which is made from a 
tri-functional polyol is branched and is introduced for crosslinking 
purposes. 
III -- CROSSLINKING AGENTS (Components B) 
A. For Soft and Hard Elastomer 
______________________________________ 
FORMULATION 7 
______________________________________ 
Pluracol 355* 100 g. 
TiO.sub.2 (rutile) 0.2 g. 
Dibutyltin dilaurate catalyst 
as needed 
100.2 
Equivalent weight per one hydroxyl 
125.1 
______________________________________ 
*Poly(oxypropylene) derivative of ethylenediamine, Mol. wt. 490 
PREATION PROCEDURE 
All the pigments are dispersed in 5% of the total polyol, Pluracol 355. For 
dispersion purposes a ball mill or roller mill or any well-dispersing high 
speed mill can be employed. 
Then all of the remainder of the polyol, Pluracol 355, is stirred in. 
Afterwards the mixture is degassed and demoisturized by applying a vacuum 
and gentle heating at 60.degree.-70.degree. C. 
The catalyst has to be added before application. The amount of the catalyst 
depends on the type of isocyanate-terminated prepolymer to be used. 
Usually 0.15-0.35% of the catalyst is added, based on the total weight of 
the polymer and on the type of the polymer and the reacting groups. 
______________________________________ 
FORMULATION 8 
______________________________________ 
1,4-Butanediol 450 
Pluracol PeP 550* 500 
TiO.sub.2 1. g. 
Dibutyltin dilaurate catalyst 
as needed 
951. -Equivalent weight per one hydroxyl 
______________________________________ 
68.0 
Footnote: 
*Poly(oxypropylene) adduct of pentaerythritol of about 500 molecular 
weight 
PREATION PROCEDURE 
All the pigments are dispersed in 5% of the polyols; then all the remainder 
of the polyols is blended with the pigment dispersion. Afterwards the 
mixture is demoisturized by applying a vacuum and gentle heating at 
60.degree.-70.degree. C. 
The catalyst has to be added before application. The amount of the catalyst 
depends on the type of isocyanate-terminated prepolymer to be used. 
Usually for the rigid elastomer formulation the amount of the catalyst is 
in the range of 0.15-0.25%, for the soft elastomer formulation, in the 
range of 0.30-0.35%. 
______________________________________ 
FORMULATION 9 
______________________________________ 
Pluracol PeP 550 500 g. 
TiO.sub.2 0.5 
500.5 
Equivalent weight per one hydroxyl 
125.1 
______________________________________ 
Preparation procedure is similar to the procedure of Formulation 8. 
______________________________________ 
FORMULATION 10 
______________________________________ 
Pluracol TP 440 420 g. 
Butanediol 450 g. 
TiO.sub.2 1 g. 
Dibutyltin dilaurate catalyst 
as needed 
871. 
Equivalent weight per one hydroxyl - 
67 
______________________________________ 
Preparation procedure is similar to the procedure of Formulation 8. 
B. For the Soft Elastomer 
______________________________________ 
FORMULATION 11 
______________________________________ 
Desmodur N - triisocyanate.sup.1 
478 
Polymeg 650 - 2112 
Pluracol TP 1540.sup.2 750 
TiO.sub.2 5.0 
Yellow No. 6 Lake 3.0 
Red No. 3 Lake 1.8 
Blue No. 1 Lake 0.2 
3350.0 
Equivalent weight per one hydroxyl 
668 
______________________________________ 
Footnote: 
.sup.1 (three moles of hexamethylene diisocyanate reacted with one mole o 
water) 
.sup.2 Poly(oxypropylene) derivative of trimethylolpropane, Mol. Weight 
1500 
PREATION PROCEDURE 
Poly(oxytetramethylene) glycol is charged into a reactor and demoisturized 
in vacuum for 2-3 hours upon gentle stirring at 60-120 rpm at 70.degree. 
C. Then the vacuum is released under dry nitrogen, and the dry nitrogen 
blanket is retained during the reaction time. 
Desmodur N-triisocyanate is stirred in and reacted with the glycol until 
the NCO content is reduced to zero. Then Pluracol TP 1540 is blended in. 
The pigments are dispersed in a small amount of the triol, Pluracol TP 
1540, and stirred in with the total content of the prepolymer-polyol 
blend. 
C. For the Hard Elastomer 
______________________________________ 
FORMULATION 12 
______________________________________ 
Desmodur N - triisocyanate 
526 
Polymeg 650 2,324 
Pluracol PeP 650* 17,150 
TiO.sub.2, rutile 40 
20,040 
Equivalent weight per one hydroxyl 
186 
______________________________________ 
*Poly(oxypropylene) derivative of pentaerythritol, Mol. Weight ca 600 
PREATION PROCEDURE 
Poly(oxytetramethylene) glycol is charged into a reactor and demoisturized 
in vacuum for 2-3 hours upon a gentle stirring of 60-120 rpm at 70.degree. 
C. Then under a dry nitrogen blanket, the triisocyanate is stirred in. The 
components are reacted until all free NCO disappears. Then Pluracol PeP 
650 is blended in. A small portion of Pluracol PeP 650 is employed for 
dispersion of pigments. 
The dispersed pigment base is added to the prepolymer-polyol blend and the 
contents are stirred properly. 
The components A and B are mixed together with the catalyst, degassed and 
then cast as above described, according to whether the components are 
selected to produce a hard non-hydrophilic polyurethane elastomer or a 
soft one. The following examples are illustrative. 
EXAMPLE 1 
HARD ELASTOMER 
Component A, Formulation 5, 100 parts 
Component B, Formulation 7, 36 parts 
Catalyst, dibutyltin dilaurate, 8 drops 
Nco/oh = 1.08 to 1 
Components A and B are degassed and demoisturized for at least 1 hour at 
60.degree. C and then blended gently with the catalyst and placed in a 
pre-heated vacuum oven for 1-2 minutes. The mixture is then poured into a 
pre-heated denture mold treated with a mold release material as previously 
described and heated at 40.degree. C for at least 1/2-1 hour. A further 
period of 2 or 3 hours at the same temperature is necessary to achieve a 
satisfactory cure but this further heating may be effected simultaneously 
with the curing of the soft elastomer. The two halves of the flask 
prepared as above described form the complete denture mold, for the 
casting of the soft-non-hydrophilic polyurethane elastomer onto the cast 
hard-non-hydrophilic polyurethane elastomer. 
The preparation of soft, non-hydrophilic polyurethane elastomers is 
illustrated in the following example. 
EXAMPLE 2 
SOFT ELASTOMER 
Component A, Formulation 1, 100 parts 
Component B, Formulation 7, 13.6 parts 
Catalyst, stannous octoate, 8 drops 
Nco/oh = 1.08 to 1 
Components A and B are degassed and demoisturized for at least 1 hour at 
60.degree. C and then blended gently with the catalyst and placed in a 
pre-heated vacuum oven for 1-2 minutes. They are then cast into a 
pre-heated denture mold containing a previously cast hard-non-hydrophylic 
polyurethane elastomer as above described and kept in an oven at 
90.degree. C for 3 hours. The denture is then removed from the mold and 
finished by removing the sprues and flash and polishing as necessary. 
In place of the hard non-hydrophilic polyurethane elastomer-forming 
composition of Example 1, there may be substituted the following. 
EXAMPLE 3 
Component A, Formulation 5, 100 parts 
Component B, Formulation 9, 36.9 parts 
Catalyst, dibutyltin dilaurate, 16 drops 
Nco/oh = 1.05 to 1 
EXAMPLE 4 
Component A, Formulation 6, 100 parts 
Component B, Formulation 9, 16 parts 
Catalyst, dibutyltin dilaurate, 16 drops 
Nco/oh = 1.05 to 1 
The compositions of Examples 3 and 4 are degassed, demoisturized, blended 
and otherwise treated as in Example 1. 
EXAMPLE 5 
HARD ELASTOMER 
Component A, Formulation 5, 100 parts 
Component B, Formulation 12, 50 parts 
Catalyst, stannous octoate, 0.40 parts 
Nco/oh = 1.1 to 1 
PREATION PROCEDURE 
Components A and B should be degassed and demoisturized under vacuum before 
blending. Then the catalyst should be blended in. The charge should be 
cast into a preheated mold, treated with a mold release agent. The 
elastomer should be cured for a half hour at 40.degree. C. 
The soft non-hydrophilic polyurethane elastomer-forming compositions of 
Example 2 may be substituted by the following: 
EXAMPLE 6 
Component A, Formulation 2, 100 parts 
Component B, Formulation 8, 7 parts 
Catalyst, dibutyltin dilaurate, 12 drops 
Nco/oh = 1.05 to 1 
EXAMPLE 7 
Component A, Formulation 3, 100 parts 
Component B, Formulation 8, 6.44 parts 
Catalyst, dibutyltin dilaurate, 16 drops 
Nco/oh = 1.05 to 1. 
The compositions of Examples 6 and 7 are degassed, demoisturized, blended, 
cast, and cured as in Example 2. 
EXAMPLE 8 
Component A, Formulation 4, 100 parts 
Component B, Formulation 11, 56.2 parts 
Catalyst, stannous octoate, 0.32 
Nco/oh = 1.05 to 1. 
PREATION PROCEDURE 
Components A and B should be heated up to approximately 60.degree. C and 
degassed and demoisturized under vacuum before blending. Then the catalyst 
should be added. The blend should be cast into a preheated mold and heated 
with a mold release agent. The elastomer should be cured in an oven at 
95.degree. C for 2 hours. 
Dentures may be made up of any combination of hard non-hydrophilic 
polyurethane elastomer-forming compositions, for example, Examples 1, 3, 
4, and 5 with any of the soft hydrophilic polyurethane elastomer-forming 
compositions, for example, Examples 2, 5, 6, and 8. Particularly good 
results are obtained by casting Example 8 on Example 5. 
It is to be understood that the invention is not to be limited to the exact 
details of operation or structure shown and described as obvious 
modifications and equivalents will be apparent to one skilled in the art.