LG Household ＆ Health Care R＆D (Shanghai) Co.,Ltd.,China

KIM Taehwan,PARK Sunkyu

R＆D Center,LG Household ＆ Health Care,Ltd.,Korea

Abstract A whitening toothpaste containing pyrrolidone groups was developed.Through the stain-removal experiment on the hydroxyapatite discs with tobacco stains,the stain-removal abilities of ammonium acryloyldimethyltaurate/VP copolymer and its toothpaste were studied.The results showed that the new toothpaste containing pyrrolidone groups had good whitening effect.The new whitening toothpaste had good safety and it had no damage to the soft and hard tissues.

Key words toothpaste; whitening; tobacco stain; ammonium acryloyldimethyltaurate

With the improvement of people’s material and cultural living standards,the attention and pursuit of tooth beauty is also increasing year by year.White teeth can increase self-confidence and play an important role in life and work.Long-term smoking causes tar depositing on the tooth surface,forming plaque,making the tooth surface yellow,brown or even black.[1]Smokers desperately need a gentler method of whitening their teeth.

Common teeth whitening products include oral care products (such as toothpaste,tooth powder,mouthwash,etc.),tooth whitening patches,whitening gels and cold light whitening devices.[2]Commonly used active ingredients for tooth cleaning and whitening in oral care products are complexing agents (such as tetrasodium pyrophosphate) to reduce exogenous tooth pigments.However,pyrophosphate has certain adverse reactions in thein vitroexperiment,which can make the calcium content of teeth decrease.[3]The whitening active ingredient in tooth whitening paste and whitening gel is peroxide (such as hydrogen peroxide,carbamide peroxide,etc.).Hydrogen peroxide molecules can enter into the tooth enamel and dentin,and undergo redox reaction with pigment groups,thereby changing the color of tooth enamel and dentin,and achieving the effect of tooth whitening.Carbamide peroxide releases hydrogen peroxide during use.Dentine hypersensitivity and gum irritation are considered to be common side effects of using hydrogen peroxide or carbamide peroxide based whitening products.[4]The principle of the cold light whitening instrument is to use blue light with a wavelength of 480 ～ 520 nm to irradiate the teeth coated with whitening agent (peroxide),so that the peroxide in the whitening agent quickly undergoes redox reaction with the pigment in the tooth enamel and dentin to achieve the effect of teeth whitening.[5]Dentine hypersensitivity and gum irritation are also common side effects of using the cold light whitening device.

OTHS et al.[6]proved that water-soluble terpolymer containing pyrrolidone groups (VP/PEG-OMe-MA/SHEMA) can combine with polyphenols through hydrogen bonds,and then with the strong detergent property of the terpolymer,the exogenous pigments can dissolve to the water.However,the safety of VP/PEG-OMe-MA/SHEMA has not been fully proven and cannot be used in oral products.According to the International Nomenclature Cosmetic Ingredient,the Personal Care Products Council of the United States,and the “general requirements on raw materials of toothpastes (GB 22115-2008)”,watersoluble ingredients with pyrrolidone groups include ammonium acryloyldimethyltaurate/vp copolymer,sodium acryloyldimethyl taurate/acrylamide/vp copolymer,hydrolyzed wheat protein/pvp crosspolymer and pvp.

The ammonium acryloyldimethyltaurate/VP copolymer is a binary copolymer with a large amount of pyrrolidinone group and has good dissolving ability.However,it has not been paid enough attention as an active ingredient for removing tobacco stains.Ammonium acryloyldimethyltaurate/VP copolymer is usually used as a synthetic polyelectrolyte thickener and gelling agent,the products made have good rheological properties,which is widely used in the field of cosmetics,but less researched in oral products.

Polyphenols are the main components of tobacco stains.[7]The polyphenols removing ability is the key for the tobacco stains removing toothpastes.The pyrrolidone group in ammonium acryloyldimethyltaurate/VP copolymer can combine with polyphenols through hydrogen bonds,which help dissolve and remove tobacco stains.This work developed a new type of toothpaste that gently removes tobacco stains by using ammonium acryloyldimethyltaurate/VP copolymer.The in vitro experiment aims to evaluate the effect of toothpaste on the removal of tobacco stains.

1 Experiment

1.1 Reagents and instruments

Experimental group reagent: ammonium acryloyldimethyltaurate/VP copolymer solution(Aristoflex AVC,Clariant Corporation,0.3%); control group reagent: tetrasodium pyrophosphate solution(TSPP,Jiangsu Debang Duoling Health Technology Limited company,0.3%).

Toothpaste of experimental group: toothpaste containing ammonium acryloyldimethyltaurate/VP copolymer (0.7%) (Table 1 for ingredients,and the ingredients used in the formula meet the “General requirements on raw materials of toothpastes (GB 22115-2008)”).In the actual brushing process,the toothpaste will be diluted to a certain extent,and the experiment is carried out after the toothpaste is diluted; the control toothpaste: toothpaste containing 2% (mass fraction) of tetrasodium pyrophosphate.

Table 1.Formula of the whitening toothpaste containing Aristoflex AVC

Hydroxyapatite tablets (HA tablets,diameter 8 mm,Huaqiao Technology); Ivoclar Vivadent AD 16-color tooth shade guide (16 colors,Ivoclar Vivadent); the color gradation order of the shade guide from light to dark: B1,A1,B2,D2,A2,C1,C2,D3,A3,D4,B3,A3.5,B4,C3,A4,C4.

1.2 Experimental method

1.2.1 HA tablets with tobacco stain samples

Choose hydroxyapatite tablets as the model of teeth.In order to study the whitening effect on colored teeth,the hydroxyapatite tablets are first put into cigarette smoke to obtain color gradation A4 samples for use.

1.2.2 Tobacco stain removal test of ingredients

Take the HA tablets with color gradation A4 and put them respectively into 100 mL 0.3% (mass fraction) Aristoflex AVC solution and 100 mL 0.3%(mass fraction) tetrasodium pyrophosphate solution.The stirring speed is 400 r/m,and the stain removal effect is compared after 14 days treatment.

1.2.3 Tobacco stain removal test of toothpaste

Put 21 g experimental toothpaste and control toothpaste respectively into 49 mL of deionized water and disperse evenly.Take the HA tablets with the color gradation A4 and put them into the abovementioned dispersion respectively,with a stirring speed of 400 r/m,and the stain removal effect is compared after 14 days treatment.

1.2.4 Impact test of oral soft tissue

The qualified inspection agency conducts the test according to theoral soft tissue irritation detection methodspecified in “YY/T 0127.13-2009 Biological evaluation of medical devices used in dentistry - Part 2: Test Method - Oral mucous membrane irritation test”.The repeated exposure method was used.Golden hamsters are anesthetized by intraperitoneal injection of sodium pentobarbital with 40 mg/kg,and the internal and external oral tissues of golden hamsters were disinfected with iodophor.The golden hamster was fixed in a supine position,and the left and right cheek pouches were exposed.The left side was the test group and the right side was the control group.A cotton ball with a diameter of 10 mm saturated with the experimental sample was placed in the left cheek pouch with forceps and contacted for 5 minutes.The right control group was treated with a cotton ball saturated with saline.According to the above method,repeat the contact once every 1 hour,4 times a day,and repeat the contact for 5 days.The cheek pouch was visually observed 24 hours after the last contact.After the experiment,the animals were killed by anesthesia.Take the mucosa and surrounding tissues treated with the samples,fix with 10% formalin,embed in conventional paraffin,semi-sequential section,take 5 slices at intervals,H-E staining,and examine tissues under a microscope.

1.2.5 The abrasivity value of toothpaste test

According to the toothpaste abrasivity value detection method specified in “GB/T 35832-2018 Testing method of the abrasivity value of toothpastes”,a full-process brushing load controllable brush grinder is used,and polymethylmethacrylate(PMMA) is used as substitute material for teethin vitroexperiments,and the toothpaste samples were tested under certain conditions of brushing speed and brushing load.After the brushing test,the abrasivity value (Ra) of the PMMA abrasive block was measured with a surface roughness meter,and the average value of the Ra value on the 8 PMMA abrasive blocks after the brushing test was used to evaluate the abrasiveness of the toothpaste sample to the PMMA abrasive block.

2 Results and discussion

2.1 Tobacco stain removal test of ingredients

The color gradation of HA tablets with tobacco stain is A4 by comparing the color with the tooth shade (Figure 1a); A4 colored HA tablets were treated with 0.3% ammonium acryloyldimethyltaurate/VP copolymer solution.After processing for 7 days,the color gradation of the HA tablets increased to A1,as shown in Figure 1b.After processing for 14 days,the color gradation of the HA tablets increased to B1.It is close to the ultra-white color shown in Figure 1c.

The color gradation of HA tablets with tobacco stain is A4 is shown in Figure 2a.A4 colored HA tablets were treated with 0.3% tetrasodium pyrophosphate solution.After processing for 7 days,the color gradation of the HA tablets increased to A3,as shown in Figure 2b.After processing for 14 days,the color gradation of the HA tablets increased to C1 shown in Figure 2c.

Figure 1.Effects of 0.3% Aristoflex AVC solution in the experimental group on removing tobacco stains for 7 and 14 days

Figure 2.Effects of 0.3% TSPP solution in the control group on removing tobacco stains for 7 and 14 days

Comparing the results of the tobacco stain removal experiment between ammonium acryloyldimethyltaurate/VP copolymer and TSPP,it can be found that under the same concentration and the same processing method,the color gradation of the HA tablets treated with 0.3%ammonium acryloyldimethyltaurate/VP copolymer solution enhances by 5 brands more than treated by 0.3% tetrasodium pyrophosphate solution.Under the same conditions,the whitening effect of ammonium acryloyldimethyltaurate/VP copolymer in removing tobacco stains is better than that of tetrasodium pyrophosphate.

2.2 Tobacco stain removal test of toothpaste

The color gradation of HA tablets with tobacco stain is A4 by comparing the color with the tooth shade (Figure 3a).A4 colored HA tablets were treated with toothpaste containing 0.7% ammonium acryloyldimethyltaurate/VP copolymer for 14 days.The color gradation of HA tablets increased to B1,which is close to ultra-white,as shown in Figure 3b.

The color gradation of HA tablets with tobacco stain is A4 by comparing the color with the tooth shade (Figure 4a).A4 colored HA tablets were treated with toothpaste containing 2% tetrasodium pyrophosphate for 14 days.The color gradation of the HA tablets increased to A2,as shown in Figure 4b.

Figure 3.The effect of the toothpaste in the experimental group on removing tobacco stains for 14 days

Figure 4.The effect of the toothpaste in the control group on removing tobacco stains for 14 days

Comparing the results of the tobacco stain removal experiment between the control groups,it can be found that under the same treatment method,the color gradation of the HA tablets treated by toothpaste containing 0.7% ammonium acryloyldimethyltaurate/VP copolymer is B1,which is 4 bands more than treated by the toothpaste containing 2% tetrasodium pyrophosphate (the color gradation is A2).Under the same treatment method,the whitening effect of toothpaste containing 0.7% ammonium acryloyldimethyltaurate/VP copolymer is better than that of toothpaste containing 2% tetrasodium pyrophosphate.The ammonium acryloyldimethyltaurate/VP copolymer contains a large number of pyrrolidone groups.The nitrogen and oxygen atoms on the pyrrolidone group are good hydrogen bond acceptors,which can combine with the polyphenol in tobacco stains and form a composition.A strong intermolecular interaction is formed through the form of hydrogen binding adsorption.[8]The presence of the ammonium acryloyldimethyltaurate group makes the composition have a good water-soluble ability.With the aid of mechanical force,the composition interacts with water molecules and dissolves into water,thereby achieving the effect of stain removal and whitening.

2.3 National standard compliance testing

After being tested by a qualified inspection agency in accordance with the requirements specified in “Toothpaste (GB/T 8372-2017)”,13 tests including packaging appearance,paste appearance,pH value,stability,strong particles,hygiene indicators,and product markings are in line with the Chinese standard.The results are shown in Table 2.

Table 2.Testing of the new whitening toothpaste according to national standards

continued

2.4 Security testing

The test results of oral soft tissue are shown in Table 3 and Table 4.Table 3 shows the visual observation results of the mucosa in the sample placement site.Comparing the mucosa of the test side and the control side,the result shows that the irritation index of the new whitening toothpaste sample is 0 after the last contact with the mucosa.Table 4 shows the results of oral histopathology.The irritation response scores of epithelial tissue,leukocyte infiltration,vascular congestion,and edema of the mucosa and surrounding tissue sections at the toothpaste sample contact site are all 0,and the oral mucosal tissue response irritation index is 0.In summary,according to the oral mucosal tissue reaction grading standard,the new whitening toothpaste has no irritation effect on the oral mucosa tissue.

Table 3.Visual evaluation of oral mucosa irritation response

Table 4.Summary of oral tissue response scores

The Ra value of the new whitening toothpaste is 0.837,which is lower than the Ra value of the standard sample (1.082) (the RDA value of the standard sample is 195,which meets FDA safety standards).The new whitening toothpaste is safe for oral hard tissues.

3 Conclusion

The control groups experiment verified that under the same conditions,ammonium acryloyldimethyltaurate/VP copolymer has a good effect of removing tobacco stains,and the whitening effect on simulated teeth stained with exogenous pigments is better than tetrasodium pyrophosphate.The toothpaste containing ammonium acryloyldimethyltaurate/VP copolymer has better tobacco stains removal effect than the toothpaste containing tetrasodium pyrophosphate on the market.In summary,ammonium acryloyldimethyltaurate/VP copolymer is a new type of ingredient that can be used in toothpaste to remove stains.Toothpaste containing ammonium acryloyldimethyltaurate/VP copolymer is effective for tobacco stains (exogenous pigments caused by smoking).It significantly reduces the adhesion of tobacco stains,and improves the color gradation of the tooth model,and the whitening effect is better than the control group.Through qualified third-party testing,the new whitening toothpaste meets the national toothpaste standard.The new whitening toothpaste has good safety and does not damage the oral soft and hard tissues.