this invention relates to oral compositions that provide sustained , efficient , inexpensive , anti - hypersensitivity activity without deleterious or undesirable side effects , and methods for using such compositions . by &# 34 ; sustained - release &# 34 ; is meant the continuous release of an active substance at efficacious levels for a suitable period of time , such as overnight . by a &# 34 ; suitable &# 34 ; period of time is meant a period of time sufficiently long to provide the desired treatment for hypersensitivity . the release of the active substance may be constant or pulsed , as long as efficacious levels of the active substance are provided to the surrounding milieu for the desired period of time . by an &# 34 ; efficacious level &# 34 ; is meant a level or concentration of a drug or other active agent which is high enough to be effective in treating the condition the drug was designed to treat . by &# 34 ; oral varnish &# 34 ; is meant a composition which is topically applied to a surface such as a tooth , and which dries as a film adhering to that surface , in a manner which resists removal under normal conditions , for example by saliva and unvoluntary mouth movements during sleep , and is mechanically removable , for example by brushing the teeth . the compilation of the components of the aforementioned oral composition is based upon the specific properties of each combination increases the antihypersensivity effectiveness of other members of the combination . the oral composition of the invention assists in the prevention of dental hypersensitivity . a variety of anti - hypersensitivity agents are suitable for the present invention . preferred is the use of strontium salts . other anti - hypersensitivity agents useful in the composition of the invention include potassium , lithium or sodium nitrate , potassium bicarbonate , potassium chloride , hydroxyapatite , fluorapatite , ammonium oxalate , edta with fluoride , fluoride , and ammonium glycyrrhizzinate . it is also a feature of this invention that the aforementioned anti - hypersensitivity agent is released to the hypersensitive site in a long - term sustained release manner so as to reduce the required frequency of use . this kind of release is accomplished by embedding the anti - hypersensitivity agent in a cellulosic or hydrophobic acrylic polymer to form a varnish for administration to the oral cavity . the use of these polymers has the additional advantage of minimizing side effects of the hypersensitivity agent . preferred are the insoluble and inexpensive polymers : hydrophobic type ( polyethylene , polymethacrylate , polyamide - nylon , poly ( ethylenevinyl acetate ) cellulose nitrate , silicones and others ). a preferred cellulosic polymer is ethyl cellulose . thus , in a preferred embodiment , an oral composition with the highly desirable characteristics mentioned above comprises an anti - hypersensitivity compound such as strontium , preferably strontium chloride , embedded in a sustained release cellulosic polymer such as ethyl cellulose , in a pharmaceutically effective vehicle . for example , strontium ( 1 - 5 parts ) and ethyl cellulose ( 5 - 9 parts ) may be dissolved in ethanol ( 80 - 120 parts ) for the preparation of sustained release delivery systems . the efficacy of such preparations ( see examples below ) demonstrates that the anti - hypersensitivity agent is efficiently released from said varnish at efficacious levels for an overnight period . in another embodiment , combinations of strontium salts with another anti - hypersensitive agent are used . for application to a dental surface , that is , a surface within the oral cavity such as the buccal and lingual surfaces of teeth , an ethanolic solution of the antisensitivity agent and cellulosic or hydrophobic polymer ( containing up to 4 % of the anti - hypersensitivity agent as used in the varnish ) are applied with a soft brush or with a spray . the dry film is formed in situ . after application of the varnish to the tooth surface and evaporation of the solvent . mouthwash forms are not suitable because of inefficient application of the composition to affected areas . preferably , a film of 10 - 160 μm thick dries on the surface of the tooth . those skilled in the art of oral medicine will , without undue experimentation , be able to produce ranges of concentrations of other appropriate antisensitivity agents and sustained release polymers . it is another feature of the invention that the oral compositions for hypersensitivity treatment and prevention also provide for additional desirable components . for example , the adhesiveness of the oral composition may be improved by the incorporation within said composition of gums such as gum mastic in a formulation providing from 1 - 20 % by weight of the gum mastic . other suitable mastics are disclosed in u . s . pat . no . 4 , 315 , 779 to heyd , d ., et al ., and u . s . pat . no . 4 , 374 , 844 to wahmi , h . v . r ., et al . in another formulation , other compositions may include demulcents / humectants ( i . e ., plasticizers ) such as polyethylene glycol 400 - to - 4000 , glycerol , sorbitol , or mineral oil in concentrations of about 1 % by weight . other humectants , detergents , or surface - active agents will be known to those skilled in the formulation of oral compositions . thus , in a preferred composition , the oral composition of the invention comprises strontium , ethyl cellulose polymer , an adhesive , a plasticizer , and solvent ( i . e ., aqueous ethanol ). in a highly preferred formulation , gum mastic is also present . water , flavorings , and coloring agents may also be present as required . having now generally described the invention , the same will become better understood by reference to certain specific examples which are included herein for purposes of illustration only and are not intended to be limiting unless otherwise specified . the following formulations ( table 1 ) were all prepared by the same general procedure as follows : ethyl cellulose and polyethylene glycol polymers were dissolved in the suitable solvent . after complete dissolution of the polymers , the additional components of the varnish were added . table 1__________________________________________________________________________material / formulation i ii iii iv v vi vii viii ix__________________________________________________________________________str ( g ) 1 . 0 2 . 0 3 . 0 3 . 0 3 . 0 4 . 0 3 . 0 3 . 0 3 . 0ec - nf100 ( g ) 8 . 5 7 . 0 6 . 0 6 . 0 6 . 0 5 . 0 6 . 0 6 . 0 6 . 0peg 400 ( g ) 0 . 5 1 . 0 1 . 0 1 . 0 1 . 0 1 . 0 -- -- -- peg 4000 ( g ) -- -- -- -- -- -- 1 . 0 -- -- glycerol ( g ) -- -- -- -- -- -- -- 1 . 0 -- mineral oil ( g ) -- -- -- -- -- -- -- -- 1 . 0ethanol ( c &# 34 ; c ) 100 100 100 80 120 100 100 100 100__________________________________________________________________________ ethyl cellulose -- ec polyethylene glycol -- peg strontium chloride -- str the best formulation was no . iv . the concentration of strontium in no . iv is lower than that currently used in toothpaste and dental solutions which contain 10 % strontium . the effect of local application of sustained release varnish containing strontium on hypersensitivity of teeth the effects of local application of a sustained - release delivery system of strontium on hypersensitive teeth is shown in table 2 . the study includes nine patients , among whom 55 teeth were treated . patients applied to their teeth nightly the strontium varnish formulation no . iv from table 1 and the teeth were tested again after 7 and 30 days . sensitivity was rated on a scale of 0 - 5 , with five being the highest sensitivity . none of the patients complained of a metallic or salty taste . table 2______________________________________the effect of local application of sustained - releasevarnish of strcntium on hypersensitivity of teethmechanical stimuli thermal stimuli day 0 day 7 day 30 day 0 day 7 day 30______________________________________patient 1 4 2 2 5 4 3 1 0 0 4 3 1 3 3 2 3 1 0 3 1 1 3 2 2 2 1 0 3 1 0 1 1 0 1 1 0 4 3 2 4 4 1patient 2 2 2 1 4 2 2 4 3 4 5 5 4 3 2 2 3 2 2patient 3 5 4 3 5 4 4 3 3 3 2 2 1 3 3 2 2 2 1 4 3 0 5 4 3 1 1 0 2 2 1patient 4 3 2 1 4 3 0 1 1 0 3 3 2 3 1 0 3 1 1patient 5 5 4 3 5 3 3 3 2 2 3 2 2 3 2 2 4 4 3 3 2 1 2 2 1 3 3 1 3 3 1patient 6 3 1 1 5 4 2 4 2 1 5 5 4 4 3 1 5 5 5 2 1 1 2 1 1 4 2 1 4 2 1 4 3 2 4 4 2 2 2 0 1 0 1 4 3 2 5 5 5 2 1 0 3 3 3 4 3 3 4 3 2 3 2 3 4 4 3patient 7 2 2 2 4 4 3 1 1 1 4 3 3 4 4 4 5 5 5 5 5 4 5 4 4 4 4 2 3 3 4patient 8 4 3 1 5 4 2 3 3 1 4 3 3 3 3 0 5 3 3 3 3 1 4 2 2 3 3 1 5 5 2 5 4 2 5 5 5 3 2 1 4 2 1 3 2 1 4 4 4patient 9 2 0 0 3 2 1 1 0 0 4 3 2 3 1 0 5 4 3 1 0 0 4 3 3 2 1 1 4 3 2 2 1 1 5 5 2 2 2 1 3 3 3 3 1 2 4 4 4number : 55 55 55 55 55 55mean : 2 . 94 2 . 13 1 . 33 3 . 80 3 . 09 2 . 33median : 3 . 00 2 . 00 1 . 00 4 . 00 3 . 00 2 . 00standard 1 . 11 1 . 17 1 . 12 1 . 09 1 . 26 1 . 36deviation : ______________________________________statistical evaluation : mechanical stimuliday 7 - significantly different than day 0 ( pl10 . sup .- 6 , pair t - test , two tailed ). day 30 - significantly different than day 0 ( pl10 . sup .- 6 , pair t - test , two - tailed ). thermal stimuliday 7 - significantly different than day 0 ( pl10 . sup .- 6 , pair t - test , two tailed ). day 30 - significantly different than day 0 ( pl10 . sup .- 6 , pair t - test , two - tailed ). ______________________________________ the results in table 2 show that most of the teeth varnished with a strontium - containing composition of the invention were no longer hypersensitive or showed significantly less hypersensitivity for as long as 30 days after beginning the application of the varnish on a daily basis . now having fully described the invention , it will be understood by those with skill in the art that the scope may be performed with a wide and equivalent range of conditions , parameters , and the like , without affecting the spirit or scope of the invention or any embodiment thereof .
the invention relates to an oral composition for the treatment and prevention of dental hypersensitivity comprising an anti - hypersensitivity agent embedded in a sustained release carrier such as a cellulosic or hydrophobic polymer , and a method for the use of said composition in treating and preventing dental hypersensitivity . the invention also provides for the supplementation of said oral composition with an adhesive and a plasticizer to increase the effectiveness of the anti - hypersensitivity agent .