NON-DUSTING AND FAST-WETTING IMPRESSION MATERIAL AND METHOD OF PREPARING SAME

SUPPORT D'IMPRESSION A MOUILLAGE RAPIDE ET NE DEGAGEANT PAS DE POUSSIERE, ET METHODE DE PRODUCTION CONNEXE

English Abstract

NONDUSTING AND FAST-WETTING IMPRESSION
MATERIAL AND METHOD OF PREPARING SAME
ABSTRACT OF THE DISCLOSURE
A non-dusting and fast-wetting powdered impression
material is prepared by coating at least a portion of the
powder components of an otherwise conventional impression
material with a surface coating agent prior to mixing with
water.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a dry powdered impression material comprising an
alginic acid salt component and a filler component, wherein
said material exhibits a tendancy toward dusting in its dry
powdered state, wherein said material is mixable with water
to form an impression paste capable of setting to a solid,
and wherein said material exhibits a further tendency toward
dusting upon admixture with water, the improvement comprising
a coating on at least a portion of the powdered components
rendering said material substantially non-dusting in its dry
powdered form and during admixture with water, said coating
being readily and rapidly wet, dispersed or dissolved by water
and present in an amount of from about 1 - 10% by weight based
on the total weight of the dry powdered components.
2. The impression material of claim 1, wherein said coating
agent is selected from the group consisting of natural polymer
dispersing agents, cellulose esters and ethers having ester
or ether groups containing free hydroxyl or carboxyl groups
and synthetic nonionic polymeric surfactants.
3. The impression material of claim 1, wherein said coating
agent is selected from the group consisting of xanthan gum,
hydroxyethyl or hydroxymethyl cellulose, carboxy methyl
cellulose, sodium polyalginate or potassium polyalginate,
polyethylene glycol or polypropylene glycol or polybutylene
glycol or copolymers thereof, ethylene glycol, propylene
glycol, triethanolamine, lauryl sulfate, sucrose butyrate,
glycerol esters and mixtures thereof.
4, The impression material of claim 1 consisting essentially
of the following components in admixture:

<IMG>
wherein said diatomaceous earth had been coated with said
polypropylene glycol prior to having been mixed with the
remaining components.
5. The impression material of claim 1 consisting essentially
of the following components in admixture:
<IMG>
wherein said diatomaceous earth had been coated with said
polypropylene glycol prior to having been mixed with the
remaining components.
6. A method for controlling the dusting of a powdered im-
pression material having a composition which, when mixed

1 6 cont.
with water, forms an impression paste capable of setting to a
solid, said method comprising coating at least a portion of
the powder with from about 1 - 10% by weight, based on the
total weight of the powdered components, of an agent which when
dry renders the powder, in its dry powder form, relatively
non-dusting.

Description

BACKGROUND OF THE INVENTION
This invention relates tc impression materials,
particularly for use in dental applications, which are formed
by mixing a powdered material with water, as for example
alginate impression materials or alginate substitute materials,
i,e., those in which the alginic acid salt component is re-
placed by a substitute polymer, for example, carboxymethyl
cellulose, xanthan gum, and the like.
Alginate impression and alginate substitute materials
are known and have been used successfully for many years in
the dental arts. 5ee, for example, U.S. 2,345,255 to Gross;
U.S. 2,390,137 to Vallandigham; U.~. 2,397,145 to vanBuren
Joy; U.S. 2,422,497 to Noyes; U.S. 2,878,129 to Rabchuck;
U.S. 3,246,998 to Higashi et al; Reissue 23,700 to Lockridge;
and U~S. 2,733,156 to Cornell.
The use of such impression materials generally in-
volves the proper measuring and then mixing of certain powder-
ed constituents or components o the impression material
(referred to hereinafter as the powdered components), with
water or a substitute liquid, proper measuring of the powdered
and liquid components ~eing essential to obtaining satisfac-
tory physical properties. Prior to mixing the powdered and
liquid components, it is common practice for the user to shake
the container in which the various powdered components of the
impression material are stored to fluff them. This fluffing
is done to facilitate the measuring or proportioning of the
powdered components, using a scoop or ladle which usually is
provided with the container. Under such circumstances,
however, when the top of the container is opened, some of the
1uffed powder tends toward dusting,~ i.e., becoming airborne
and 1Oating out of the container, Dusting also tends to
occur when the powdered components are mixed with water or a

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water substitute due, at least in part, to the difficulty with
which the powdered components are wet by the water. In
practice, the powdered compon~nts are placed in a flexible
mixing bowl and water is added to ito The powdered components
do not wet immediately and the bulk o~ the powder floats for
a period of time on the surface of the water during mixing,
thus permitting some dusting to occur. The dusting problem
is further exaggerated because the harder one stirs the
powdered components/water mix, the greater is the opportunity
for a portion of the powder to become airborne.
This dusting, which occurs primarily when a portion
of the filler in the powdered components separates from the
remaining powdered components and becomes airborne upon mixing
or shaking, or upon stirring with the liquid component of the
impression material has become the cause of concexn because
of its potential health hazard. (Woody, R. D. et al, JA~A 9~,
501, 1977). Accordingly, it is a principal object of the
present invention to reduce the dusting that occurs when the
filler in the powdered components separates and becomes air-
borne upon mixing or shaking.
It i5 another object of the present invention toachieve easier wetting of the powdered components by water or
a substitute liquid.
DESCRIPTION OF THE INVENTION
In accordance with the present invention, the greater
ease and speed with which the powdered components are wet by
water during mixing, the elimination of airborne particles
o~ powder, and other objects and advantages are achieved when
the constituent powdered particles, or at least a portion
thereof, are coated with a minor amount of a surfactant/dis-
persing agent or compound which is readily and rapidly wet,
dispersed or dissolved by the water or substitute liquid
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component of the impression material~ This coating o~ the
powdered particles causes the individual particles to be
attracted to one another so that they do not easily become
airborne, and permits the powder particles to be easily wet
by the water or substitute liquid. Examples of substances
which may be used to coat the powdered particles are, for
example, natural polymer dispersing agents such as xanthan
gum, sodium polyalginate or potassium polyalginate, cellulose
esters or ethers having ester or ether groups containing free
hydroxy or carboxyl groups such as hydroxyethyl or hydroxy-
methyl cellulose, carboxyl methyl cellulose, synthetic ionic
polymeric surfactants such as those which contain substantial
amounts of units derived from alkylene o~ides such as poly-
ethylene glycol or polypropylene or polybutylene glycol or
copolymers of them, .including polymeric surfactants of which
the Tween* and Brij* series produced by ICI Americas are
examples, and others including, for example, block copolymers
of polysiloxanes and polyethylene glycols. The coating agent
need not necessarily be limited to polymers but may include
monomeric substances, for example, polyols such as ethylene
glycol, propylene glycol, alkanolamines such as triethanol-
amine, and compounds such as lauryl sulfate, sucrose butyrate,
glycerol esters, and the like. Mixtures of the above coating
agents also may be used. It should be evident, then, that a
wide variety of coating agents may be employed, in varying
dusting reducing, powder wetting enhancing amounts, usually
from about 1-10% by weight based on the total weight of the
powdered components, so long as the respective agent that is
used adequately coats the powdered compo~ents, and is readily
and quickly wet, dispersed or dissolved by the liquid compon-
ent of the impression material to provide a composition
wherein dusting is significantly reduced and the powdered
* Trade Mark

components are significantly more rapidly wet upon mixing as
compared to the same composition absent the coating agent.
The preferred composition of the invention has a Dust
Index of less than about 100 using a Gelman* Air Analyzer
(See Example 4).
The invention will be more fully understood in con-
junction with the following examples thereof, which examples
merely are illustrative and should not be considered to be
limitive of the materials and procedures employed in practic-
ing the invention.
Example 1
An alginate impression material was produced from thefollowing components:
Component
Sodium alginate 14.0
Calcium sulfate 17.4
T~trasodium pyrophosphate 2.5
Potassium titanium fluoride 1.0
Magnesium oxide 2.6
Diatomaceous earth (filler) 57.8
Polypropylene glycol (coating agent) 4.7
The diatomaceous earth filler was wet with the polypropyl~ne
glycol coating agent before being admixed with the other
powdered components. The entire mixture was blended in a
ribbon blender. A 14 gram sample of the resulting mixture
was placed in a mixing bowl mounted on an "Alginator"*
produced by Cadco Products. An appropriate quantity of
water was then added to the bowl and the "Alginator" was
caused to turn. A spatula was held in a fixed position in
the turning mixture and it was observed that after 5 seconds
the alginate powder was wet. It was also observed that there
were no dust particles released upon stirring.
The procedures of Example 1 were repeated, except
that potassium alginate was used in place of sodium alginate.
* Trade Mark

20~7
A complete wetting of the alginate was noted within 5 seconds
and no dusting was observedO
Example 3
The procedure of Example 1 was repeated except that
the polypropylene glycol (coating ag~nt) was eliminated from
the alginate powder formulation. In contrast with the results
of Example 1, it was observed that it took the same alginate
formulation, except for the omission of the surface coating
agent, 10 seconds to be wet by the water. It was also observ-
ed that there was a great deal of "dusting".
~,~
In order to quantify the observation of dusting a
standard container of alginate impression material powder was
fluffed by turn~ng and rotating the container for 20 seconds.
Immediately the top was removed and the relative concentration
of particles released from the surface were quantifiad using
a Gelman Air Analyzer, a unit which is designed to measure
particulate contaminates in industry. The air immediately
above a c~ntainer of the alginate formulation prepared in
accordance with Example 1, i.e. having a coating agent present
on the filler particles, was sampled and a particle content
(Dust Index) of 6.S micro grams per liter of air per minute
was observed. This was much less than a particle content
(Dust Index) of 215 micro yrams per liter of air per minute
measured for the same alginate impression material powder
handled in the same manner, but not surface treated. Both
the surface treated powder and that not treated, complied
fully with the requirement of ADA Specification 18 for
Alginate Impression Material.
Using the same procedure, additional dust-free
alginate compositions were made using different coating
agents. Successful coating ayents, their "Dust Index", and
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2a~
chemical name are listed in the following Table:
Trade Wame HLB Value Chemical Name"Dust Index"
Xanthan gum 59
Tween ~0* 16.7 polyoxyethylene (20)14
sorbitan monolaurate
BRIJ 97* 12.4 polyoxye-thylene (10)34
oleyl ether
SPAN 85* 1~8 Sorbitan trioleate 37
Propylene glycol 44
These coating agents all are capable of providing useful
alginate materials.
Example 5
The procedure of Example 1 was repeated, except that
the alginate impression material was pxoduced from the
following components:
Component Parts by Wei~ht
Sodium alginate 8.5
Potassium alginate 8.5
Magnesium oxide 3.0
Magnesium carbonate 4.0
Potassium fluorotitanate 4.1
Calcium sulfate 17.0
Sodium fluoride 0.5
Sodium tripolyphosphate 1.5
Potassium diphosphate 1.3
Polypropylene glycol 3.5
Diatomaceous earth 48.0
A complete wetting of the alyinate impression material was
noted within 5 seconds and no dusting was observed.
Although the present invention has been described in
connection with preferred embodiments thereof, it is to be
understood that modifications and variations may be resor-ted
to, without departing from the spirit and scope thereof, as
those skilled in the art will readily understand~ Such
modifica~tions and variations are considered to be within the
purview and scope of the appended claims.
* Trade Mark
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