Patented Mar. 7, 1950 2,499,676

UNITED STATES PATENT OFFICE. 2,499,676. DENTALEMPRESSION WATERA. Lloyd.T.Parr and Samuel B. Rabishaw, Chicago, Ill., No Drawing, Application. August 21, 1945, Serial No. 61,920 Clain (C. 8-4) 2 The present, invention pertains to impression incorporation of a plasticizer, or water-holding. materials, for producing. accurate reproductions agent, such as glycerine. But, heretofore, it has of objects, and more particularly to, materials for not been; possible to package a product of this taking dental impressionS. type commercially in dry powder form. The principal object of the invention is to pro Crystallie SOrbitol, mannitol or dextrose in duce a dental impression material of Such con dry poWodered form can be mixed and packaged sisteracy as to facilitate the production of more With the dry powdered alginate type in pression precise dentures. materials, and when mixed with Water Will dis Where comfort, appearance, and function re solve to form a plasticizing or water-holding quire that the denture should precisely fit the O agent, which will control evaporation and will mouth it is absolutely necessary to produce in greatly reduce or prevent dimensional inaccuracy pressions with materials whose ingredients are caused by evaporation. conducive to proper combination to create more The following is a formula using a plasticizer effective molds. of the above mentioned type to control the loss in the field of dentistry there has been the 5 of Water by evaporation, and thus to maintain the problem of inaccurate and inefficient materials noisture at a constant level. The following for for taking impressions of the teeth. Plaster of mula illustrates the incorporation of both a plas Paris was used for many years, but this had many ticizer and an active filler. The ingredients disadvantages. It was not only unpleasant to thereof are finely powdered and mixed to a horno the patient, but also, after the impression had 20 geneous naSS: set in the mouth it was difficult or impossible to Per cent remove the impression without damage, With a Trisodium phosphate ------. 2.40 resultant reconstruction of doubtful accuracy. Potassium (water-soluble) alginate ------8.6 More recently, impression materials of agar Were Crystalline Sorbitol ------23.00 introduced, and although it was an improvement, 25 Calcium Sulphate ------8.61. there was nevertheless, Some distortion due to Starch (active filler) ------57.38. uncontrolled factors. Moreover, With the agar impression materials, which were time consum 100.00 ing in preparation, there is the ever present dan This entire mass is then mixed with Water that ger of burning the mouth of the patient. Due 30 is at room temperature in Sufficient amount to to the Wartime shortage of agar, there Were de form a paste by stirring and working the mixture veloped impression materials of the alginate type. rapidly with a spatula, for a predetermined length These, too, have been an improvement, yet they of time, thus maintaining in paste form the have shown inadequacies. homogeneity of the powder. The mass is then In the practice of the present invention, CryS 5 ready for insertion into the patient's mouth and talline Sorbitol, mannitol, or dextrose has been is placed in a suitable impression tray, carried incorporated into an alginate impression mate to the mouth and seated in position. In a few rial so as to delay the dehydration, and control minutes after the mass is placed in the mouth, dimensional change, of the finished impression. it gels to a solid which is sufficiently elastic to Heretofore, available impression materials of the 40 withdraw from undercuts, etc. without permanent dry powder alginate type were composed mainly distortion. of a jelling agent (alginate), a gel retarder (tri The mass after gelling does not adhere to the sodium phosphate), a gel accelerator (calcium mouth or teeth, and a replica or stone cast of the sulphate), and an inert filler. These chemicals, mouth is obtained by casting any of the several When properly balanced and mixed with Water, artificial stone products on the market into the set, to form a flexible gel. After the calcium Sul impression, the artificial Stone in powdered form phate had reacted with the water-soluble aligi being first formed, of course, into a suitable paste. nate to form calcium alginate, this gel Would lose In the above formula, the crystalline sorbitol water by evaporation when exposed to air, or serves as the plasticizer, and the starch acts as imbibe water by immersion. In either event, the 50 the Active filler. dimensional accuracy is changed to Such an eX With the above formula, a balance of moisture tent that the positive cast made therefron is an is maintained between the impression material inaccurate one. and the stone material, thereby imparting to the It is Well known that the loss of noisture from replica, or stone cast of the mouth a smooth and products of this type can be controlled by the 55 durable and tough surface of fine texture, a result 2,499,676 3 4. not heretofore achieved with similar products. tion to its application in dental science, we do By using both the plasticizer (crystalline sor not intend SO to limit its use, but rather to extend bitol, mannitol, dextrose, etc.) and an active filler its application to all cases where a resilient, accu (starch) we have discovered that it is possible to rate impression material may be of utility. control dimensional change and increase flexi What we claim is: bility which will prevent dimensional distortion. Material for taking impressions comprising tri In addition to the use of starch as an active Sodium phosphate, potassium alginate, crystalline filler, there are other fillers which can be used, SOrbitol, calcium Sulphate and starch. which also actively enter into the formation of LLOYD. T. PARR. the gel, thereby increasing the strength and re O SAMUEL B. RABISHAW. ducing dimensional change due to evaporation. Fillers of this type would include the water REFERENCES CITE) Soluble gums Such as karaya, acacia, locust bean, The following references are of record in the tragacanth and pectin. In addition to the natural file of this patent: gums, materials such as hide glue, gelatine, and 15 polyvinyl-alcohol, when used as fillers, also enter UNITED STATES PATENTS actively into the formation of a strong and stable Number Name Date gel. In general, colloids which are Water-soluble 1,194,176 Healy ------Aug. 8, 1916 or exhibit water-holding properties, having a pH 1897,034 Harrison ------Feb. 14, 1933 no lower than 4.5 and no higher than 10.0 and 20 2,158,485 Preble ------May 16, 1939 which are non-reactive to calcium and trisodium. 2,165,680 Staugenbury et al. --- July 11, 1939 phosphate, may also be used. 2,249,694 Wilding ------July 15, 1941

While we have described our invention in rela 2,359,512 Dickson et al. ------Oct. 3, 1944