the wording &# 34 ; substance being sparingly soluble in water &# 34 ; used in the present disclosure refers to tannic acid derivatives which are hardly or slightly soluble in water , inter alia , tannic acid - protein combinations , tannic acid - formaldehyde combinations , acetyl tannic acid and metal tannates . the protein used for the tannic acid - protein combinations may be of either simple or conjugated type . for example , use may be made of simple protein such as protamin , globulin , albumin , glutelin , prolamin , gelatin and the like as well as conjugated protein such as nucleoprotein , phosphoprotein and the like . of these protein , particular preference is given to albumin . no particular limitation is placed upon the metal salts of tannic acid used in the present invention . however , it is preferred to make use of salts of low toxicity ( in vivo ) such as aluminium , calcium , zinc , magnesium and strontium salts . tannic acid derivatives can be added to the compositions applied in the mouth such as dentifrices , mouthwashes and gargles , oral refrigerants , caries preventive agents and tooth make - up agents etc . a mouthwash is a solution for rinsing the teeth and mouth . generally , a mouthwash serves as an adjunct in cleaning the mouth and as an aid in removing loose debris after brushing . a gargle is liquid to wash mouth and throat especially for medicinal purposes . an oral refrigerant is in such forms as chewing gum , candy , liquid and pellet etc . chewing gum usually consists of a chicle base , glucose , powdered sugar , starch and flavoring . other bases may be also used . a caries preventive agent is an agent to have an effect on prevention of caries , for example , fluoride agents ( fluoride solutions and gels , fluoride rinses , fluoride containing varnishes ). a tooth make - up agent is a kind of cosmetics applied on the teeth . this is similar to nail enamel , namely , it is tooth enamel . it is to be noted that the compositions according to the present invention may contain other additives in addition to the tannic acid derivatives . for instance , the incorporation of other known substances serving to prevent dental caries poses no problem . it is also to be noted that the tannic acid derivatives being sparingly soluble in water , as used in the present invention , may be synthesized in various known processes . the present invention will now be explained in further detail with reference to some examples , to which the invention is not limited . toothpaste was prepared by using the composition of example 1 , provided that 3 . 5 % by weight of tannic acid was used in place of albumin tannate . after one - day storage , the resultant toothpaste apparently turned ashen . toothpaste was prepared by using the composition of example 1 free from albumin tannate . after one - day storage , the resultant toothpaste underwent no discoloration . it was evidently appreciated from the example 1 , comparative example 1 and comparative example 2 that the toothpaste of example 1 did not discolore unlike in comparative example 1 . plaque estimation was then made with the toothpaste of example 1 and comparative examples 1 and 2 . the marrow was extracted from a fresh tooth pulled out of a cattle , which was in turn sterilized in an ethylene oxide gas sterilizer after ultrasonic washing . a toothbrush ( manufactured by gc dental industrial corp . and sold in the trade name of prospeck m ), to which 1 . 5 grams of the toothpaste of example 1 were applied , was reciprocated 200 times for cleaning the surface of that tooth . the thus cleaned tooth was suspended in mitis - salivarius liquid medium in which the overnight - cultured bacteria of streptococcus mutaos strains was planted at a concentration of 5 %, and was then cultured at 37 ° c . for 8 hours under gentle stirring with a magnetic stirrer . thereafter , the test piece was washed with water , dried under reduced pressure in a desiccator to observe the surface of enamel thereof with a scanning electron microscope ( sem ). in another experiment , sem observation was carried out with a tooth sample which was cleaned in the same manner with a dentifrice - free brush . in a further experiment , similar sem observation was undertaken with a tooth sample cleaned with a brush to which albumin tannate - free dentifrice , for instance , those of comparative examples 1 and 2 , was applied . in consequence , it was observed that the surface of enamel of the tooth cleaned with the dentifrice - free brush was entirely covered with bacteria and plaque formed . on the contrary , 90 % of enamel was covered with bacteria in the case of using the dentifrice of comparative example 2 . it was also noted that 40 % and 35 % of enamel were covered with bacteria in the case of using the dentifrice formulations of comparative example 1 and example 1 , respectively . from this , it has been appreciated that albumin tannate has an effect upon the inhibition of plaque formation , which indicates that it serves to prevent dental caries . twelve healthy men ( 23 - 29 old ) were subdivided into four groups , each comprising three . group a cleaned the teeth with a brush to which the toothpaste of example 1 , groups b and c did so with brushes to which the toothpaste of comparative examples 1 and 2 was applied , and group d did so with a dentifricefree brush . brushing was effected three times a day , say , in the morning , afternoon and evening , and continued for ten days . brushing was then discontinued for 24 hours . thereafter , the dirt was rubbed off from the neck of the entire upper jaw teeth located on the cheek with a ready - made applicator , planted in mitis - salivarius liquid medium , and allowed to stand at 37 ° c . for 48 hours . subsequently , the ph of the liquid medium was measured with a ph meter . the ph values of groups a , b , c and d were respectively 6 . 2 , 6 . 0 , 5 . 6 and 5 . 2 on the average . it has been appreciated that group a shows the lowest actvity to caries .
a composition applied in the mouth which has a preventive effect on dental carries and contains such tannic acid derivatives as of solubility resistance to water .