Abstract:
The present invention relates to an oral care composition and a method of disinfecting the oral cavity. So far synthetic material (e.g. Triclosan) has been used which is believed by many consumers to be harsh on them. Consumers, more and more prefer using products that contain natural materials. Further, in many countries, culturally or otherwise, people are reluctant to using alcohol in their mouthwashes. The present inventors have been working on solving these problems and have come up with an oral care composition which includes natural materials that are found to interact synergistically with certain metal salts in killing  S. mutans , a bacterium responsible for tooth decay.

Description:
TECHNICAL FIELD 
     The present invention relates to an oral care composition and a method of disinfecting the oral cavity. 
     BACKGROUND AND PRIOR ART 
     Oral hygiene is one of the most important aspects of personal care among consumers. Consumers all over the world use different types of products for oral care. People routinely brush their teeth with a toothbrush and a dentifrice which may be a toothpaste or a toothpowder at least two times a day. Use of such brushing ensures maintaining good oral hygiene by minimising oral bacteria that accumulate in the mouth over the course of sleeping in the night or during the course of the day when people eat their food and consume beverages. Brushing, thus minimises problems like cavities, tartar, gingivitis, caries, and bad breath, also known as halitosis. 
     In spite of brushing teeth twice a day, many people suffer from various forms of one or more of the above named diseases and this is believed to be caused by bacteria acting in the oral mucosa over the about twelve hour period between brushing. During such times, people resort to rinsing/gargling their mouth with an antiseptic mouthwash. Most antiseptic mouthwashes contain a substantial amount of alcohol (e.g. ethyl alcohol or isopropyl alcohol) for killing oral bacteria. 
     In solving the above oral care problems, the approach so far has been to use synthetic materials (e.g. Triclosan) which are believed by many consumers to be harsh on them. Consumers, more and more, especially of late, prefer using products that contain natural materials. Further, in many countries, culturally or otherwise, people are reluctant to using alcohol in their mouthwashes. 
     The present inventors have been working on solving these problems and have come up with an oral care composition which includes natural materials that are found to interact synergistically with certain metal salts in killing  S. mutans , a bacterium responsible for tooth decay. 
     Essential oils actives have been cited in prior publications in oral care. 
     JP2196718 (Kowa, 1989) discloses a liquid for external use having increased solubility and stability, containing 0.1 to 5% indomethacin and a 0.3 to 10% dissolution auxiliary as essential components, the dissolution auxiliary selected from limonene, pinene, camphene, cymene, citronellol, geraniol, nerol, linalool, terpineol, rhodinol, borneol, isoborneol, menthone, camphor, thymol, safrole, isosafrole, eugenol and isoeugenol. 
     WO 00/00166 (Warner Lambert) discloses an oral composition that includes thymol, a zinc salt and a sweetener is disclosed. The oral composition has antitartar, antiplaque, antigingivitis efficacy, long lasting breath freshening and high consumer acceptability in spite of the presence of two ingredients, thymol and a zinc salt, that are known to taste bad. 
     None of the publications, to date, teach that a mixture of antimicrobial essential oil actives thymol and terpineol when used along with a specific metal salt provides for fast acting anti-microbial action, in a synergistic way. The present inventive combination provides vastly improved and synergistic anti-bacterial efficacy as compared to a combination of zinc salt and thymol as disclosed in WO 00/00166. 
     It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative. 
     Another object of the present invention is to provide for an antimicrobial composition that has relatively fast antimicrobial action in killing bacteria in the oral cavity. 
     SUMMARY OF THE INVENTION 
     The first aspect of the present invention provides for an oral care composition comprising
     (i) 0.05 to 10% of an antimicrobial essential oil comprising thymol and terpineol, such that the composition comprises
       0.03 to 0.4% by weight thymol, and   0.06 to 0.6% by weight terpineol;   
       (ii) 0.1 to 5% of a zinc salt; and   (iii) an orally acceptable base;
 
wherein the zinc salt is zinc halide, zinc sulphate, zinc acetate or zinc phosphate;
 
and wherein the combination of the thymol, the terpineol and the zinc salt provides synergistic anti-bacterial efficacy against  Streptococcus mutans.  
   

     The second aspect of the present invention provides for a method of disinfecting the oral cavity comprising the steps of 
     (i) applying a composition of the first aspect onto the oral cavity; and 
     (ii) cleaning the cavity to be substantially free of said composition. 
     The third aspect of the present invention provides for use of a composition comprising
         (i) 0.05 to 10% of an antimicrobial essential oil comprising thymol and terpineol, such that the composition comprises
           0.03 to 0.4% by weight thymol, and   0.06 to 6% by weight terpineol; and   
           (ii) 0.1 to 5% of a zinc salt;
 
for disinfecting the oral cavity;
 
wherein the zinc salt is zinc halide, zinc sulphate, zinc acetate or zinc phosphate;
 
and wherein the combination of the thymol, the terpineol, and the zinc salt provides synergistic anti-bacterial efficacy against  Streptococcus mutans.  
       

    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     These and other aspects, features and advantages will become apparent to those of ordinary skill in the art from a reading of the following detailed description and the appended claims. For the avoidance of doubt, any feature of one aspect of the present invention may be utilised in any other aspect of the invention. The word “comprising” is intended to mean “including” but not necessarily “consisting of” or “composed of.” In other words, the listed steps or options need not be exhaustive. It is noted that the examples given in the description below are intended to clarify the invention and are not intended to limit the invention to those examples per se. Similarly, all percentages are weight/weight percentages unless otherwise indicated. Except in the operating and comparative examples, or where otherwise explicitly indicated, all numbers in this description indicating amounts of material or conditions of reaction, physical properties of materials and/or use are to be understood as modified by the word “about”. Unless specified otherwise, numerical tinges expressed in the format “from x to y” are understood to include x and y. When for a specific feature multiple preferred ranges are described in the format “from x to y”, it is understood that all ranges combining the different endpoints are also contemplated. 
     The compositions of the present invention are preferred for non-therapeutic use, and more particularly preferred for use in disinfecting surfaces of the oral cavity. 
     The first aspect of the present invention provides for an oral care composition comprising 0.05 to 10% of an antimicrobial essential oil comprising thymol and terpineol as described below, 0.1 to 5% of a zinc salt; and an orally acceptable base. 
     The composition preferably comprises 0.1 to 5% of essential oil. The essential oil comprises thymol and terpineol and preferably also comprises components selected from eugenol, horned, limonene, iso-borneol, eucalyptol, camphor or a mixture thereof. More preferably, the essential oil also comprises eugenol. 
     Eugenol 
     Eugenol is an allyl chain-substituted guaiacol. It is generally extracted from certain spices like clove or cinnamon. Eugenol has been used as a perfumery component, in preparing flavors, as an antiseptic or as a local anesthetic. The composition of the invention preferably comprises 0.005 to 5%, preferably 0.02 to 1%, more preferably 0.03 to 0.4%, by weight eugenol. 
     Eugenol has the structure: 
     
       
                 
         
             
             
         
      
     
     Thymol 
     The structure of thymol is given below: 
     
       
                 
         
             
             
         
      
     
     The composition of the invention comprises 0.03 to 0.4%, by weight thymol. Thymol may be added to the composition in purified form. Alternatively, thyme oil or thyme extract comprising thymol may be added to the composition, while ensuring that thymol is present in the desired concentration in the composition of the present invention. Thyme oil or thyme extract is obtained from the thyme plant. Thyme plant refers to a plant belonging be genus  Thymus  and includes but is not limited to the following species:  Thymus vulgaris, Thymus zygis, Thymus satureoides, Thymus mastichina, Thymus broussonetti, Thymus maroccanus, Thymus pallidus, Thymus algeriensis, Thymus serpyllum, Thymus pulegoide , and  Thymus citriodorus.    
     Terpineol 
     The structure of a terpineol compound is given below: 
     
       
                 
         
             
             
         
      
     
     The terpineol is preferably selected from alpha-terpineol, beta-terpineol, gamma-terpineol or mixtures thereof. It is particularly preferred that the terpineol is alpha-terpineol. Terpineol may be added to the antimicrobial composition in purified form. Alternatively pine oil comprising terpineol may be added to the antimicrobial composition while ensuring that terpineol is present in the desired concentration in the composition of the present invention. The composition comprises 0.06 to 0.6% by weight terpineol. 
     The composition may preferably comprise a combination of thymol and terpineol in any of the preferred concentrations as specified above for thymol and terpineol, respectively. 
     For instance, the composition may preferably comprise a mixture of 0.03 to 0.6% thymol and 0.06 to 1.5% terpineol by weight of the composition. The composition of the present invention most preferably comprises a mixture of 0.03 to 0.4% eugenol, 0.03 to 0.6% thymol, and 0.06 to 1.5% terpineol by weight of the composition. 
     Zinc Salt 
     Preferred zinc salts are zinc halide (preferably chloride or bromide), zinc sulphate, zinc acetate, or zinc phosphate. The composition comprises 0.1 to 5% zinc salt. 
     Orally Acceptable Base 
     The antimicrobial composition comprises an orally acceptable base. The orally acceptable base depends on the format in which the oral care composition is delivered. Most suitable formats are an antiseptic mouthwash, a toothpaste or a toothpowder. 
     Mouthwash 
     When the composition is formulated as an antiseptic mouthwash, the orally acceptable base is water. The desired antibacterial efficacy in the mouthwash of the present invention can be obtained without the use of low molecular weight (C1 to C3) alcohols e.g. ethanol or isopropyl alcohol, i.e the composition is preferably substantially free of low molecular weight alcohol. By the term substantially free of low molecular weight alcohols is meant that the alcohol may be present in an amount which does not significantly affect the microbial kill. Preferably, C1 to C3 alcohols are present in leas than 2%, more preferably less than 1% and most preferably absent from the composition of the invention. 
     Thus, the invention, provides an antimicrobial mouthwash composition according to the first aspect of the invention (i.e. comprising thymol, terpineol and a zinc salt) also comprising 80 to 99.9% water. The antimicrobial mouthwash composition of the invention preferably comprises 0.05 to 10%, more preferably 0.05 to 8%, most preferably 0.5 to 5% of a surfactant by weight of the composition. The surfactant is preferably of the cationic, anionic, or zwitterionic class, most preferably of the cationic class. When anionic surfactant is present it is preferably chosen from alkali or alkaline earth metal salts of alkyl sulphonic acid, fatty acid, or alkyl ether sulphate. When zwitterionic surfactant is present it is preferably chosen from betaines, sulphobetains, hydroxyl sulphobetains, or amino carboxylates When a cationic surfactant is present it is benzalkonium chloride, alkyl pyridinium chloride or quaternary ammonium gemini surfactants. 
     The antimicrobial mouthwash composition of the invention is used for disinfecting the oral cavity either by using the composition with no dilution or after diluting the composition with water. The preferred weight ratio of composition to water for the dilution step is in the range of 1:1 to 1:200, more preferably 1:5 to 1:50, further more preferably 1:15 to 1:30 and ideally about 1:20. 
     Toothpaste 
     The composition of the invention may be delivered in a toothpaste format. When the composition is a toothpaste, the orally acceptable base is an abrasive which may be calcium carbonate or abrasive silica. When calcium carbonate is the abrasive, the toothpaste is in the opaque paste format. When abrasive silica is used, the toothpaste is usually delivered in the transparent gel format. Toothpastes also preferably comprise a surfactant in 2 to 15% by weight of the composition. Preferred surfactants are anionic or amphoteric in nature. Anionic surfactant is preferably an alkali metal alkyl sulphate, more preferably a sodium lauryl sulphate (SLS). Mixtures of anionic surfactants may also be employed. The amphoteric surfactant is preferably a betaine, more preferably an alkylamidopropyl betaine (wherein the alkyl group is a linear C10˜C18 chain), and most preferably is cocoamidopropyl betaine (CAPB). Mixtures of amphoteric surfactants may also be employed. Suitable surfactant concentrations in oral care application are generally from about 2% to about 15%, preferably from about 2.2% to about 10%, more preferably from about 2.5 to about 5% by weight of the total composition. 
     Opaque Toothpaste 
     When calcium carbonate is the abrasive, it is usually present in 15 to 70%, more preferably in 30 to 60% by weight of the composition. 
     Calcium carbonate (also known as chalk) is available in many forms and some of these forms are used in oral care compositions. Two commonly used forms are FGNC (fine ground natural chalk) and PCC (precipitated calcium carbonate). Of the total chalk content in the oral care composition, FGNC, is generally present in 35 to 100% preferably from 75 to 100% and especially from 95 to 100%, the balance being PCC. Typically, the FGNC will comprise from 30 to 65%, preferably from 35 to 55% and most preferably from 40 to 55% by weight of the composition. 
     FGNC generally comprises particles of weight-based median particle size ranging from 1 to 15 μm, preferably from 2 to 10 μm and especially from 4 to 7 μm. 
     The composition may also include other known “non-chalk” abrasives to improve the abrasive action. Such abrasives include dicalcium phosphate dihydrate (DCPD) and silica. 
     In addition to calcium carbonate, one can also include abrasive silica in opaque toothpastes for enhanced abrasive action. The abrasive silica may be included in 4 to 15%, preferably 6 to 12%, and further more preferably 7 to 10%. Alternatively perlite may be included in 0.0.1 to 2%, preferably in 0.1 to 0.8%, further more preferably 0.3 to 0.7% by weight of the composition. 
     Water in these toothpastes is generally included in 15 to 40%, preferably 20 to 30% by weight of the composition. 
     Preferred compositions include a humectant, e.g. xylitol, glycerol or sorbitol. Glycerol and sorbitol are particularly preferred. Preferably, the compositions include 0.1 to 20 wt % humectant. More preferred compositions include 1 to 15 wt % humectants while further preferred compositions include 5 to 13 wt % humectants. 
     The compositions preferably also include an alkali-metal bicarbonate salt. Preferably the alkali-metal bicarbonate salt is a sodium salt, from 1 to 30 wt %, more preferably from 2 to 20 wt % and especially from 3 to 8 wt %. 
     Gel Toothpaste 
     Preferred compositions to prepare gel toothpaste comprise an abrasive silica. They preferably have a low refractive index in the range of 1.41-1.47, preferably 1.435-1.445, preferably having a weight mean particle size of between 5 and 15 micrometer, a BET (nitrogen) surface area of between 10 and 100 m 2 /g and an oil absorption of about 70-150 cm 3 /100 g. Typical examples of suitable low refractive index abrasive silicas are Tixosil 63 and 73 ex Rhone Poulenc; Sident 10 ex Degussa; Zeodent 113 ex Zeofinn; Zeodent 124 ex Huber, Sorbosil AC series supplied by Crosfield, for example Sorbosil ACI1, Sorbosil AC39 and Sorbosil AC35, particularly Sorbosil AC 77 ex Crosfield Chemicals. The amount of these silicas in the composition generally ranges from 2-60% by weight, usually 2-20% by weight and more preferably 5 to 12 wt %. 
     Thickening silica may also be incorporated in gel toothpastes. They are usually incorporated in 4 to 12%, preferably 5 to 10% by weight of the composition. Preferred grades are medium thickening silica such as MFIL (ex. Madhu Silica India), TC15 (from PQ Corp UK), and Zeodent 165 Ex. Huber, or Tixosil 43 from Rhodia. 
     Water in these toothpastes is generally included in 8 to 14%, preferably 8 to 10% by weight of the composition. These amounts of water are exclusive of water which are incorporated in the composition from aqueous solutions of other ingredients e.g. sorbitol. 
     The compositions for any type of toothpaste (opaque or gel type) may also include an anti-caries agent, binders, thickeners, flavours, stabilizing agents, polymers, vitamins, buffers and anti-calculus agents. 
     Thus, according to a preferred embodiment of the invention there is provided a toothpaste composition according to the first aspect of the invention, also comprising 2 to 70% of an abrasive selective from calcium carbonate or silica; and 8 to 40% water. 
     Toothpowder 
     Toothpowders usually have very high percentage of abrasives. Chalk (FGNC) is the most preferred one but PCC can also be used. Usual percentages of such abrasives are from 90 to 99.9%, preferably 90 to 95% by weight of the composition. Desired amount of foam is provided by including an anionic surfactant e.g. Sodium Lauryl Sulphate in the toothpowder composition. The surfactant may be incorporated from 2 to 3% in the composition. Other ingredients like silica or Sodium monofluoro phosphate may be included at up to about 1 weight % of the composition. 
     Sweeteners such as xylitol, sorbitol, glycerol or sachharin may be included. Flavors such as spearmint or peppermint may be included at up to 1 weight % of the toothpowder composition. 
     The present invention therefore also provides a toothpowder composition according to the first aspect of the invention, comprising 90 to 99.9% of an abrasive selected from calcium carbonate or silica. 
     Thus, in the composition of the present invention the orally acceptable base is preferably selected from water, silica, or calcium carbonate. 
     An aspect of the present invention provides for a method of disinfecting the oral cavity comprising the steps of (i) applying a composition of the invention on to the oral cavity; and (ii) cleaning the cavity, to be substantially free of said composition. By cleaning is meant that the composition is substantially removed from the oral cavity. The composition, when in liquid form (e.g. a mouthwash) is simply spat out. When the composition is in powder, paste or gel form the composition may be rinsed off from the oral cavity using suitable amount of water. When the composition is a toothpaste, it is generally brushed on to the teeth or gums in the oral cavity before the step of rinsing. Rinsing is usually done by taking water and washing or gargling the mouth with this water. 
     Yet another aspect of the present invention provides for use of a composition comprising
         (i) 0.05 to 10% of an antimicrobial essential oil comprising thymol and terpineol, such that the composition comprises
           0.03 to 0.4% by weight thymol, and   0.06 to 0.6% by weight terpineol; and   
           (ii) 0.1 to 5% a zinc salt;
 
for disinfecting the oral cavity;
 
wherein the zinc salt is zinc halide, zinc sulphate, zinc acetate or zinc phosphate;
 
and wherein the combination of the thymol, the terpineol, and the zinc salt provides synergistic anti-bacterial efficacy against  Streptococcus mutans.  
       

     The invention preferably provides for non-therapeutic benefits. 
     EXAMPLES 
     The invention will now be demonstrated with examples. The examples are for purpose of illustration only and do not limit the scope of claims in any manner. 
     Examples 1 to 5 
     Synergistic Interaction of the Ingredients of the Composition of the Invention 
       Streptococcus mutans  ( S. mutans ) is a Gram-positive, facultatively anaerobic bacterium commonly found in the human oral cavity.  S. mutans  is the leading cause of dental caries (tooth decay) worldwide and is considered to be the most cariogenic of all of the oral streptococci.  S. mutans , sticks to the surface of teeth and subsists on a diverse group of carbohydrates. While metabolising sugar and other energy sources, the microbe produces acid that causes cavities in teeth. 
     Various Compositions as Shown in Table-1 were Prepared. 
     The compositions listed in Table-1 were used to test the efficacy as an antibacterial composition against  S. mutans  in a 15 second contact test in suspension, using the following procedure. 
     The test bacteria  S. mutans  was grown overnight at 37° C. in BHI broth under 5% CO 2  (CO 2  incubator). Then the culture was processed and the cell density was adjusted at 620 nm to get the final count of 10 8  cfu/ml (0.3 OD). 9 ml of the compositions was taken in a sample container and 1 ml of processed culture was added to it. After a 15 second contact time 1 ml of the above mixture was immediately neutralized in D/E broth. This was serially diluted in D/E broth and plated in BHI agar in duplicates. In case of the control, 1 ml of test culture was added to 9 ml of saline and was serially diluted and plated on BHI agar. After solidification, the plates were incubated at 37° C. under 5% CO 2  for 48 hrs. The residual colonies were counted after 48 hours and the log reduction of bacteria with respect to the control sample was calculated. The data are compiled in Table 1. 
     
       
         
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                 Example 1 
                 Example 2 
                 Example 3 
                 Example 4 
                 Example 5 
               
               
                 Ingredient 
                 wt % 
                 wt % 
                 wt % 
                 wt % 
                 wt % 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Zinc 
                 0.2 
                 — 
                 0.2 
                 — 
                 0.2 
               
               
                 sulphate 
               
               
                 Thymol 
                 — 
                 0.125 
                 0.125 
                 — 
                 0.125 
               
               
                 Terpineol 
                 — 
                 — 
                 — 
                 0.25 
                 0.25 
               
               
                 Water 
                 To 100 
                 To 100 
                 To 100 
                 To 100 
                 To 100 
               
               
                 Log 
                 0 
                 0.1 
                 0.4 
                 0 
                 7.1 
               
               
                 reduction 
               
               
                   
               
             
          
         
       
     
     The data in Table 1 indicate that the composition as per the invention (Example-5) provides for synergistic anti-bacterial efficacy as compared to using a combination of thymol and zinc salt (Example 3 as disclosed in WO 00/000166) and when using terpineol alone (Example-4). 
     Examples 6-8 
     Efficacy of Various Compositions Against  S. mutans  in a One Minute Contact Test in Suspension 
     Various compositions as shown in Table-2 were prepared. 
     The compositions listed in Table-2 were used to test the efficacy as an antibacterial composition against  S. mutans  in a one minute contact test in suspension, using the following procedure. 
     Culture  S. mutans  was taken in a BHI broth [and was allowed to grow in CO 2  incubator (15% CO 2 ) at 37° C. for 15 hours]. The  S. mutans  culture was adjusted to a optical density to 0.3 (˜10 8  cfu/ml) at 620 nm. 9 ml of the desired composition was taken and added to 1 ml of culture and mixed. After a one minute contact time with the culture, they were neutralized in D/E broth and after serial dilution they were plated in BHI Agar. The plates were incubated in CO 2  incubator. The residual colonies were counted after 48 hours of incubation. The efficacy compared to a control sample was measured and the data is compiled in Table-2. 
     The amount of log reduction of the bacteria was measured and the data is summarized in Table 2. 
     
       
         
               
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                   
                 Example 6 
                 Example 7 
                 Example 8 
               
               
                   
                 Ingredient 
                 Wt % 
                 Wt % 
                 Wt % 
               
               
                   
                   
               
             
             
               
                   
                 Terpineol 
                 0.125 
                 — 
                 0.125 
               
               
                   
                 Thymol 
                 0.250 
                 — 
                 0.250 
               
               
                   
                 Eugenol 
                 0.025 
                 — 
                 0.025 
               
               
                   
                 Zinc Sulphate 
                 — 
                 0.120 
                 0.120 
               
               
                   
                 Water 
                 To 100 
                 To 100 
                 To 100 
               
               
                   
                 Log reduction 
                 1.0  
                 0.2  
                 7.3  
               
               
                   
                 of bacteria 
               
               
                   
                   
               
             
          
         
       
     
     The data in Table 2 indicate that the antibacterial efficacy of a composition of the invention (Example 8) demonstrates synergistic antibacterial activity with respect to essential oil active combination of thymol, terpineol and eugenol (Example 6) and zinc salt composition alone (Example 7).