CA1091861A - Dental impression compound - Google Patents

Abstract

Abstract of Disclosure A dental impression composition is formulated from a hydrogenated wood rosin, petrolatum, aluminum powder and talc and includes the following characteristics:
(1) good plastic flow at mouth temperature to provide adequate working time with low flow at room temperature;
(2) good heat and light stability which affords good shelf life with no change in flow properties; (3) flow proper-ties not changed during extensive heating and sterilization during preparation for application on the dental tray;
(4) sufficient, but not excessive adhesion strength so that the composition adheres to the tray but not to the patient's wet tissues; and (5) low thermal-expansion coefficient so that there are no dimensional changes as the impression is cooled from mouth temperature; and (6) good definition of detail.

Description

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Dental Impression Compound : Eack~round of Invention , .. .
", A dental impression compound suitable for soft, ,~ mobile ti~sue should meet the following requirements:
. 5 (1) have good plaistic flow at mouth temperature .~ with a minimum of 85% at ~7 C.

(2) ~et quickly when exposed to temperature~
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slightly below that of the mouth;
(~) should unite into a solid mass without ad- ~
hering to mouth tissues or plaster cast material but should :
adhere to th~ tray material;
(~) give a good negative reproduation oP the . dimensions and surfa¢s detail of the mouth tissues without f displacing the detail from its true position;
(5) good dlmensional stability at temperatures below that of the mouth so that it will not deform in any ~:
way because of temperature changes, atmospheric conditions, or the pouring of a plaster cast;
.` (6) should not be unpleasant or toxic to the 0 patient;
. . , (7) should have good shelf life;
(8) should be easy and convenient to use; and (9) capable of sterilization when in the con-tainer in which it is supplied.
?5 Of the commercially available impression compounds ....
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1~91861 known to applicant, EX-3-N-Gold, a trademark for a product made by Johannes Meist of Nurnberg, Germany, apparently made in accordance with the disclosure in. German patent 1,067,175, has the most desirable plastic flow at mouth temperature. However, an impression compound made in accordance with German patent 1,067,175 cannot be sterilized in an autoclave without affecting its properties.
Summary of the Invention .i .
The dental impression composition disclosed herein achieves the ; foregoing objectives. The impression compound has a flow rate of 85% as hereinafter defined at mouth temperature and thus, sets quickly when removed from the mouth. The impression compound gives good reproduction of detail , and is easy to work with. The substances employed in the composition, namely, ~- hydrogenated wood rosin, white petrolatum and with a filler comprising talc , and aluminum powder provide a heat and light stable composition which can be sterilized prior to use without changing its properties.
, The present invention provides a dental impression composition .. :
consisting of hydrogenated wood rosin 65.5 to 91.0 percent; white petrolatum .0 to 9.5 percent; talc 0 to 20 percent; alùminum powder 5 to 25 percent;
total talc and aluminum 5 to 25 percent.
Further objects, features and advantages of the invention will become apparent from the following disclosure.
Description of the Drawings -Figure 1 is a group of curves showing the percent of flow versus ~- temperature for five compositions tested.
Figure 2 is a group of curves similar to Figure 1 showing percent ,: i ; flow versus temperature for other proportions of the chemical.

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` 1091861 Description of Preferred Embodiment In order to evaluate the flow properties of dental impression compounds, equipment was designed and con~tructed to cast impression compound columns ten millimeters in diameter and six millimeters high and to expose each column to a pre~sure of 2000 grams at a selected temperature for ten ~; minutes. The column height was measured before and after ,, exposure to the pressure. The percent decrease in column height is designated as the plastic flow of the material at - 10 the ~elected temperature. The Figures 1 ana 2 show percent ....
flow versus temperature ~or various proportions of the com-ponents of the composition of the invention.
Various thermo-plastics were tested and hyd~ogenated wood rosin appeared to have the most favorable and de~irable -, 1 15 characteristics for a dental impression compound. The par-. - , ticular hydrogenated wood rosin successfully tested is marketed under the trademark "~TAYBELITE" a product of Hercules In-corporated. "STAYBELITE" is highly resistant to oxidation and discoloration and to changes in solubility characteri~tics exposed to air and sunlight. "STAYBELITE" has low taste, odor ,, and good thermo-stability.
Various plasticizers were tested and white petrolatum gave good results. Petrolatum has moderate uni~ormity pro-- vided by high compliance with USP specification~, low o~or or taste, good heat and light stability and most importantly, good .

~ 1C~91 8 6 1 compatibility with hydrogenated wood rosin that results in no tendency to migrate or sweat to the surface of the mixture when cooled to solidification. Mineral oil, which had been tried in earlier experimentation as a plasticizer, had a tendency to migrate to the surface of cooled mix-tures when used with STAYBELITE, causing tackiness.
In addition to the thermo-plastic hydrogenated `~ wood rosin and the plasticizer petrolatum, a filler is necessary to maintain the mixture of thermo-plastic and plasticizer when it solidifies in a rigid solid state and to increase the working temperature range of plastic flow between a rigid solid and low viscosity liquid. The filler also is desirable to decrease the surface tackiness of the ! mixture. Talc and aluminum powders were found suitable as fillers. Commercial grades of Alcan MD 3100, a trademark ~ ;
for a product made by Aluminum Company of Canada, and US
Bronze 560, a trademark for a product made by U.S. Bronze Co., provided good results. Both of these aluminum powders are non-leafing, fine mesh, stearic acid-coated powdar with ~- 20 roughly spherical shapes. The Alcan MD 3100 is specified , , to have 97~0% minimum pass through 325 mesh. The aluminum powder improves thermoconductivity so that when the ~ composition is heated preliminary to brushing on a tray, the impression material will be quickly and uni-formly softened to the plastic state so that no local overheating with consequent degradation of the material will occur. Thus, when the compound on the tray is placed in the mouth, all of the mass will be subject to plastic flow.

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.. , - ~ . ,-1C~91861 Furthermore, when the completed impression is cooled by cool water, all of the material will rapidly set to the solid state and not be subject to further stress and deformation. ~en the dental stone is cast in the impression, the heat generated during the thermal stage of the setting stone will be conducted away from the surface of the composition and stone so that the adverse effects of local compound melting and the inter-penetration of the plastic and stone with consequent adhesion, and surface damage, will be minimized. Inasmuch as aluminum has a low density, the larger volums per unit weight in the co~position means that a given weight percent of aluminum will have a greater effect on the thermal-conductivity of the mixture than a similar amount of other heavier metals. Also , the aluminum has less tendency to settle out of the mLxture when it is heated to the fluid state as will occur with heavier metals - In initial tests, aluminum particles in the form of ~-~ flakes were used in formulating a dental impre9sion compound, .
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but ultimately the choice of spherical or more regularly shaped particles was made because the formulations with aluminum flake~ did not have sufficient flow under stress at mouth temperatures. This disadvantage is believed to have been due to an interlocking or interference of relative move-ment of the aluminum due to the irregular shape of the flakes.
In addition, large particles of aluminum can also interfere ' :

_ ~ , with obtaining an impression with the necessary fine detail snd definition.
The U~P talc used in the composition is a native, hydrous magnesium silicate that is moderately uniform in pr~perty if it complys with the U~P specifications. Its specific gravity of 2.7 to 2.8 is similar to the specific gravity of aluminum of 2.708 90 they don't tend to separate in the mixture when in a fluid state.
The following tables 1 and 2 disclose various pro- -.
portions of STAYBELITE, petrolatum, aluminum and talc and the temperature flow characteristics obtained in M ow measure-ments for these particular compositlons. Table 1 contains ,,i~ .
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;,~ the data for Figure 1, which shows percent flow at various temperatures for compositions 115, 116, 117, 118 and 119.
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Fig. 1 also includes a curve I whioh shows the desired flow characteristic for this type of dental impression compound.
-' The curve I pa~ses through the recommended maximum permitted ~'?~ flows of ten percent at ten degrees C, twenty percent at 15 degrees C, fifty-five percent at twenty degrees C and through the recommended minimum flow of 85% at 37 C or .
~ mouth temperature.
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~ -6-~' ' TART~ ample Formula~ and Flows Formul~ Weight Percent _ . . . .
StaybelitePetrolatum Aluminum Talc (White, USP) US Bronze 560) (USP) ~15 78.78 5.84 5.12 10.25 ~ 116 77.o8 '7.89 5-23 9.80 ,~ 117 77.02 8.02 '4.99 9.97 118 86.20 8.9I 4.78 0.00 ' 119 76.49 8.51 5.00 10.00 ,' .
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,' Formula Temperatures, C Mouth '~ Flow~ ~ Temperature (37 C) , ' .
, . , '~-',115 15,8 21.8 27.9 ~4.2 ~9.4 ',, 7.8 ~7.9 70.9 84.~ 89.o 87.5 i, ` , . ~
','116 ~7.1 22.2 27.6 33.6 38.2 ,,,, 38.1 66.7 78.8 86.2 90.5 89.4 -, ,,''117 16.2 24.8 31.7 37.8 '' 15.4 66.6 81.4 88.2 87.8 . .','118 17.7 25.1 31.4 37.0 ~-, , 57.6 78.6 86.6 91.0 90.8 . , '''~119 10.016.6 25.6 33.7 37.1 , 11.845.4 74.6 87.5 90.3 90.3 ,,;,,.~
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':' TABLE 2. Trial Batch Formulas and Flows Batch Weight Percent Staybelite Petrolatum Aluminum Talc (White, U~P)(Alcan MD 3100~ (USP) 1 77.00 8.oo 5.00 10.00 2 77.00 8.oo 5.00 10.00 ~C 78.26 6.50 5.08 10.16 , 4 78.50 6.50 5. 10.00 ', ,5A 78.50 6.50 5.00 10.00 '"~
' 5C 78.34 6.70 4.99 9.98 '~
O Mouth Tem}
, Batch Tlmper~ ure~, C perature , 1 ~, 16.2 26.1 35.1 36.1 ' ' 28.6 73.0 85.5 89.0 87.6 ~;'', 2 36.2 "" 89 5 ~ C 80~ 16,0 19.5' 26.4 30.9 38.8 `,' 7.45 16.17 47.04 77.44 84.92 88.5288.2 ', 4 12.4 18.4 22.6 29.1 32.9 ~5.4 40.0 ,'"' 8.69 40.84 61.93 79.97 85.82 89.oo 89.7589.3 :
'''' 5A 10.5, 16.4''- ?2-1' 29.2 35.7 ~6.4 ~7:8 '', ' 6.02 8.66 35.56 69.47 82.04 88.56 89.7289.0 5C 1~.9 36-7 , 5.83 86.51 .,~ .

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- In the experiments recorded in Table 2, the changing from one brand of white USP petrolatum to another can greatly effect; the amount of petrolatum needed for desired flow properties. Table 2, Batch 1, had one type o~ petrolatum `5 (white USP) and Batch 2 had a different type of petrolatum, although in the same proportions as Batch 1. Different percent flow characteristics were achieved between Batches 1 and 2.
The following Table 3 indicates composition ranges for the dental impres~ion compound based on formulas 115 10 through 119 in Table 1 and Batch 1 of Table 2.

TABLE ~ - Approximate Compo~ition Ranges of the ;Dental Impres~ion Compound, weight percents Range Wide Narrow Optimum Total Filler 5 - 25 10 - 20 15 Aluminum powder 5 - 25 5 - 20 5 - 15 Talc, USP O - 20 0 - 15 0 - 10 Plasticizer White Petrolatum, USP 6.5 - 9-5 7.5 - 8.5 7.75 - 8.25 ~Plastic Hydrogenated wood ro~in 65.5 - 88.5 71.5 - 82.5 76.75 - 77.25 Overall Total 100 100 100 ..'.' ,,,:
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Because the properties of the impression compound depend ; on selection of the mutually interdependent weight percents of its components, some of the factors that affect the choice should be discussed. Experiment indicates that the total filler content may be varied from about 5 to 25% while main-taining a reasonable plastic flow temperature range centered on mouth temperatures by compensating selection of the plasti-cizer content. Eelow about 5~ filler content the plastic flow temperature range is more narrow than desired, the surface of ; 10 the warmed mixture increases in tackiness, and even if the filler is all aluminum powder the thermal conductivity of the mlxture will not be much better than that of the plastic alone.
Above 25% filler content, the plastic flow temperature range ... .
is wider than desired ~o that it may extend close to room tempera-tures and result in impres~ion~ that will lose detail and . .
accuracy before and during ca~ting of the dental stone positive~
For convenience the total filler content of the formulation i~
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initially selected at or near 15%. Of this at least 5% is selected to be aluminum powder so that significant thermal conductivity ~ ,~
~ 20 improvement will be achieved. Additional thermal conductivity - improvement i3 realized with increa~ed aluminum powder content . .
up to the total filler limit. However, the presence of talc as the balance of the total filler content has the advantages of decreasing the mixture's cost and easing the possible selection of another mixture color.

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If a pigment were to be used to produce another mixture color, its weight percent would be ~ubtracted from that of the talc 90 the total filler content would remain constant. The plasticizer content is then selected to provide ~ufficient 5 flo~ at mouth temperature.
Because even the ingredients of this compound which have been selected partially for their uniformity do vary slightly in their properties from purchased batch to batch, the correct ~, amount of plasticizer must be ~elected ~or a selected total filler ,~
: 10 content on the basis of flow tests of tri~l formulation~ of the ,v, components.' In practice, the correct amount o~ plasticizer for ,~, 15% fillér content has been,about 8% with one petrolatum and, ; . . . .
"; 6.5% with another. After selecting the filler content and ~inding '~
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~" the correct plasticizer content through experiment, the plastic :, .
, 15 content (hydrogenated ro~in) is of course, fixed because it i9 ,, the remainder of the formulation. To in~ure that each batch , .
of the impression compound has the correct flow characterlstics, ,~ proper quality control will require that the flow be determined ,; ~ .
with the proper instruments and methods at a minimum of two 20 temperatures - one between 10 snd 15 C, and one at about ~7 C.
~`' This quali'ty control is especially important whenever new ~uantities ,., '' of the components are obtained.
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',' To achieve good results with almost any dental material, requires correct manipulative techniques. This fact,is also 25 true in the case of this dental imp,ression material. To obtain , . . .

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, good impressions of soft mouth tissues with this material, the correct techniques ~re required.

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Claims (4)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A dental impression composition consisting of hydrogenated wood rosin 65.5 to 91.0 percent; white petrolatum 4.0 to 9.5 percent; talc 0 to 20 percent; aluminum powder 5 to 25 percent; total talc and aluminum 5 to 25 percent.

2. A dental impression composition in accordance with claim 1 wherein the composition consists of essentially a mixture by weight of hydrogenated wood rosin 71.5 to 89.0 percent; white petrolatum 6.0 to 8.5 percent; talc 0 to 15 percent; aluminum powder 5 to 20 percent; total talc and aluminum 5 to 20 percent.

3. A dental impression composition in accordance with claim 1 wherein the composition consists of essentially a mixture by weight of hydrogenated wood rosin 76.75 to 88.75 percent; white petrolatum 6.25 to 8.25 percent; talc 0 to 10 percent; aluminum powder 5 to 15 percent; total talc and aluminum 5 to 15 percent.

4. A dental impression composition in accordance with claim 1 wherein the hydrogenated wood rosin, white petrolatum, aluminum powder and talc are in such proportions to have a maximum permitted flow of 10% at 10°C, 20% at 15°C, 55% at 20°C and a minimum flow of 85% at 37°C.