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In Vivo Study on the Tooth Whitening by Use of Hydrated Silica and Sodium Hexametaphosphate Contained Dentifrice
Int J Clin Prev Dent 2020;16(2):58-67
Published online June 30, 2020;  https://doi.org/10.15236/ijcpd.2020.16.2.58
© 2020 International Journal of Clinical Preventive Dentistry.

Min Jeong Cho1, Seung Chul Shin2, Sun Young Chung3

1Research Institute Clinical Dentistry, Praha Dental Clinic, Busan, 2Emeritus Professor of Dankook University College of Dentistry, Cheonan, 3Preventive Dentistry Moon Dental Hospital, Cheonan, Korea
Correspondence to: Min Jeong Cho
E-mail: prahaoral@naver.com
https://orcid.org/0000-0002-1761-3052
Received June 21, 2020; Revised June 26, 2020; Accepted June 29, 2020.
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
Objective: This study was performed in clinical experiment in order to prove the tooth whitening effect by use of the abrasives of the dentifrice with Hydrated Silica and Sodium Hexametaphosphate.
Methods: 92 volunteers were participated in this clinical study through dividing 3 groups as control group for using plane dentifrice, experimental 1 group for using Hydrated Silica dentifrice and experimental 2 group for using Hydrated Silica and Sodium Hexametaphosphate contained dentifrice for 2 weeks. Tooth whitening was checked with Vita shade guide and VITA EASY SHADE V. L*, a*, b* value was checked by use of CIE (Commission Internationale de l’Eclairage) Lab system and compared them between 3 groups.
Results: Tooth whitening effect was revealed from a week in experimental group 1 and 2 and the more effect in experimental group 2, measured by Vita Shade guide. It revealed a little color change for experimental group1 from a week later, but much color change for experimental group 2, measured with VITA easy shade V (p<0.05). Moreover, it revealed more satisfaction for tooth whitening effect in subjects of the experimental group 2.
Conclusion: Hydrated Silica and Sodium Hexametaphosphate contained dentifrice would be considered as effective for tooth whitening.
Keywords : discoloration of tooth, tooth bleaching, tooth shade, tooth whitening
Introduction

Tooth whitening has been distributed as common in modern life through the esthetic interest had been increased for people and popular in recent years. It has been classified the discoloration of the tooth surface as extrinsic origin from outer surface and intrinsic origin as color changes in tooth its-self. The etiologic factors for the extrinsic discoloration are known as food and beverages with colors such as coffee and cola, etc. or tobacco, which are favorite products. In this case, it can be removed by physical stimuli and chemical actions such as brushing and professional oral prophylaxis method. And intrinsic discoloration is caused by aging, administration of antibiotics in the tetracycline system and systemic diseases, etc. In this discoloration teeth whitening can only by achieved using chemicals such as peroxide [1].

Therefore, tooth-whitening is effective by the mechanism of action of chemicals and a technique that oxidizes the coloration in the internal tooth and has whitening effects [2].

Tooth whitening is largely classified in three ways. There are in-office bleaching performed by dental clinics and hospitals, home-bleaching under the guidance of dentists, and there is an over the counter (OTC) bleaching that individuals perform on their own without a professional prescription [3]. However, it takes a lot of time and money to increase the effectiveness of all these procedures. Therefore, a product that expects whitening effects by adding a separate drug to dentifrice that is highly accessible to use was developed.

The whitening action of whitening dentifrice is done by various chemicals, which contain enzymes, detergents and oxygen supplies [4]. Therefore, the role of whitening dentifrice is excellent in that it is possible to whiten teeth just by brushing teeth for a long time with dentifrice containing chemicals that are expected to have whitening effects in daily life. Moreover, the ability to reduce and remove the coloration of extrinsic discoloration teeth increases the potential value of whitening dentifrice.

Studies related to whitening dentifrice on tooth staining caused by extrinsic discoloration are being reported. Trevor et al. [5] reported the results of evaluating the ability to remove external coloration by applying whitening dentifrice. As a result, it reported a significant reduction in coloration after four weeks compared to normal dentifrice, and maintained or further decreased after six weeks. Paik et al. [6] reported tooth whitening effects of calcium peroxide and sodium bicarbonate in dentifrice containing the abrasive silica. Kim et al. [7] evaluated the color change of teeth whitening dentifrice and general dentifrice and reported that the color change of teeth by whitening dentifrice was about 2.3 times higher after four weeks. And these results were then described as containing of calcium carbonate and sodium silica, the abrasive that helps whitening effects. Therefore, the special abrasive component contained in whitening dentifrice was identified as an important component to maintain whitened teeth while increasing the brightness of the tooth color.

Meanwhile, in tooth staining of external discoloration there are cases where the staining substance attaches to the teeth to darker the teeth or the staining substances attached to the teeth produce darker staining by that metal in the oral cavity. In this case, it can be removed using SHMP (SHMP; sodium hexametaphosphate) that chelates metal ions, or by dentifrice mixed with high-cleaning silica (Hydrated Silica) that has excellent stain removing efficacy.

SHMP paste is repeated with pyrophosphate subunit. So it is known to effectively prevent the attachment of new staining components to teeth by combining them a strong fore of calcium ions in hydroxyapatit with the tooth enamel and also to eliminate staining components by chelating metal particles that cause staining [8,9]. In addition, the hydrated silica paste has about 25% better cleaning effect than the normal silica [10].

This study was designed to improve the coloration of teeth by comparing changes in the color of teeth of dentifrice containing Hydrated Silica alone or Hydrated Silica and Sodium Hexametaphosphate with control dentifrice through a two week clinical trial.

Materials and Methods

1. Subjects

The Korean Academy of Preventive Dentistry posted the recruitment documents on its website from September 2019 and those who responded to them were eligible for the clinical trial. Adult male and female over the age of 20 who were all natural maxillary 6 anterior teeth, had no experience in dental caries or restoration treatment, and had similar degree of discoloration of each tooth along with appropriate level of tooth discoloration were selected for study. And after fully explaining the purpose and method of this study and obtaining written consent, the 99 people who participated in the oral examination were randomly assigned 33 persons each to A (Con.), B (Exp 1), and C (Exp 2). The final target was 92 people, excluding those who had difficulty in sustaining the research after their first visit or who were eliminated during the process (Table 1).

Table 1 . Gender and age distribution of the subjects to study

GroupGender (N)Average age

Male Female Total
A group (Con.)11193039.93±13.14
B group (Exp 1)8253339.70±10.99
C group (Exp 2)2092946.17±12.42
Total39539241.82±12.40


This clinical study was performed after permission of the ethic committee certified by the Ministry of Health and Welfare, Korea (IRB, PO1 201908-11-007).

2. Design

This study was conducted by double blindness test method after random assignment of study subjects. A total of four visits were made to each county, before Start, three days after the start, one week after the start, two weeks after the start, to compare the results after conducting a dental color test. In this process, measurement errors were minimized by maintaining the same illumination intensity at the same place for each measurement. And to assess the safety of research dentifrice, gingival index test was conducted before the study began and two weeks later of the study, and a survey was conducted using a sensory satisfaction assessment method after using whitening dentifrice. During the study period, study subjects were asked to use only research dentifrice and toothbrushes provided, and recommended brushing teeth for two minutes at least three times a day after teaching brushing teeth with a rotating method. And in order to check whether the toothbrush was implemented, the subjects were required to fill out their own records and to bring them with them at each visit. It was recommended to refrain from beverages and foods that may cause staining as much as possible. The main ingredients of the dentifrice used in the test are as shown in Table 2.

Table 2 . Active ingredients

GroupCon. (A)Exp 1 (B)Exp 2 (C)
Active ingredients (Dentifrice)- Sodium fluoride (KP) 0.22% (1,000 ppm F)- Sodium fluoride (KP) 0.22% (1,000 ppm F)- Sodium fluoride (KP) 0.22% (1,000 ppm F)
- Dental type silica (NF) 14%- Hydrated Silica (KQC) 13%- Hydrated Silica (KQC) 13%
- Tocopherol acetate (KP) 0.05%- Tocopherol acetate (KP) 0.05%- Tocopherol acetate (KP) 0.05%
- Sodium Hexametaphosphate (KQC) 7.5%

All procedures and methods are the same, with only different dentifrice components provided to groups A, B and C also Only A, B, and C are marked on the same shaped container.



3. Method

1) Screening procedures and methods

(1) Oral examination: Using mobile dental chairs and artificial lighting, the dentist conducted only once oral examination of the dental conditions of the maxillary 6 anterior teeth (Time required: 3 minutes). As a result, those with dental conditions that do not comply with this study were excluded from the study.

(2) Method of allocation of study subjects: The number was assigned by simple random assignment method and the number selected assigned to the test group for each county. The control group and test group 1, control group and test group 2 were assigned 33 persons each at a 1:1 level. And the test group was distributed in the same container as the toothpaste of the negative control group so that the test group could not be identified. Random assignment officer, random assignment methods, double blindness methods and procedures, each person in each study procedure, and volunteers were assigned to A-control group, B-Test group 1, C-Test group 2 in the order of volunteers. After the assignment was completed, the number of male and female in each county was readjusted to be similar according to age and gender.

2) Examination and evaluation of tooth color

This study followed the criteria for evaluating whitening effect of the maxillary anterior teeth according to the guidelines for clinical trials of tooth whitening agent by the Ministry of Food and Drug Safety. All those selected for the double blind method were measured with the ‘VITA Easyshade V’ (manufacturing source: VITA Zahnfabrik [Germany]), a colorimetric instrument dedicated to teeth, for objective whitening efficacy evaluation. Before measuring, foreign substances on the maxillary 6 anterior teeth of surface were lightly wiped off with gauze, and the measuring device wore an anti-infection membrane on the measurement tip. In addition, to prevent errors due to measurements, the chromaticity instruments were adjusted to zero points each time they were measured. The measurement of tooth brightness was made with a focus on the center of the crown centered on the maxillary central incisor and three repeated measurements were taken for each tooth to minimize errors in the measurements. The values measured by the measuring instrument were obtained in accordance with the Lab system of the Commission Inter-nationale de l’Eclairage (CIE), and the values of L*, a*, and b* were calculated using the following expressions. The L* value is the intensity value indicating brightness, the a* value is the red-green chromaticity value indicating the degree of red to green, the b* is the yellow-blue chromaticity value indicating the degree of yellow to blue, and the ΔE* value is the value of the color change amount. The shade differences were averaged after the L*, a*, and b* values were obtained and the ΔE* values were calculated and the formula for the calculation of ΔE* values is as follows.

ΔE*={(ΔL*)2+(Δa*)2+(Δb*)2}1/2

ΔL*=L2−L1, L2=post-experimental value, L1=pre-experimental value

Δa*=a2−a1, a2=post-experimental value, a1=pre-experimental value

Δb*=b2−b1, b2=post-experimental value, b1=pre-experimental value

And the effects of whitening teeth were compared and analyzed in parallel with the evaluation of devices and visual evaluation by using the Vita classical shade guide (Vita Zanfabrierek, H. Rauter GmbH & Co. KG, Bad Sackingen, Germany) chromaticity. The visual evaluation was calculated as the average value by giving the highest intensity of 1 to 16 points for the lowest intensity of lightness, referring to the classification by VITA in order of intensity.

3) Gingival index

During this test, the Löe & Silness index test was performed before the start of the study and two weeks after the start to assess the safety of the study dentifrice, observing the change in the maxillary 6 anterior teeth periodontal tissue. The evaluation of a person’s gingival health was divided into 4 sides (mesial, distal, buccal, lingual) surrounding the teeth, and the number of gingivitis per tooth was recorded after scoring o for normal, 1 for very mild, 2 for moderate and 3 for severe.

Löe & Silness index=sum of gingivitis score/total of gingival margin

*The lower score, the better gingival health

4) Survey

After the two-week test, 92 people who finally participated in the test were evaluated using a five-point scale questionnaire on whitening effects from the use of contrasting dentifrice and test dentifrice and the symptoms of sensitivity on their teeth, etc.

4. Data analysis

All statistical analyses used SPSS Statistics ver. 19.0 for Window (SPSS Inc., Chicago, IL, USA), and all statistical significance levels were set at p=0.05. Frequency analysis was performed to determine the general characteristics of the study subjects and satisfaction with the whitening teeth, and c2-test was performed to analyze the relevance of the whitening dentifrice used. In addition, pared t-test was performed to determine the change in the gingival index over the period of use of dentifrice, and change of brightness over the period of use of dentifrice was analyzed using the Repeated Measure ANOVA test method, and significant differences between groups were tested post-test using Tukey’s multiple comparison method. In addition, a one-way ANOVA test was performed to compare differences between groups by measurement point.

Results

1. Teeth whitening effect

1) Comparison of brightness changes (DL*) using Vita shade guide standard table

Table 3 is the result of comparing the change in brightness using the Vita shade guide standard table. The teeth whitening effect during the period of use of the test dentifrice was evaluated using the Vita shade guide, showing statistically significant differences between the groups in the degree of brightness of the teeth over the period of use of the test dentifrice (p<0.05). And as a result of comparing the group-specific measurement scores, the control group displayed minimal teeth whitening effects during the two weeks of the test (p>0.05). However, test group 1, which contains only high- clean silica, showed differences in the change of brightness from the third day of examination, and gradually brightened tooth tones until the last two weeks of examination, showing statistically significant differences (p<0.05). The second group of tests containing sodium hexametaphosphate showed a rapidly brightening of the teeth a week after the examination. And the difference in brightness between before (4.59±3.42) and after 2 weeks (2.66±2.57) of the use of dentifrice was 1.93 points, the biggest difference in brightness (p<0.05). In addition, there was no difference between pre-test and three days after the examination the test in the post-analysis, and there was a difference between one week after the test and two weeks after the test.

Table 3 . Comparison of brightness changes over the period of use of dentifrice

GroupBefore3 days1 week2 weeksp-value1p-value2
ΔL*Con.304.37±3.77a4.27±3.54a4.30±3.60a4.17±3.29a0.222<0.001
Exp1334.42±4.05a3.55±2.85b3.15±2.72bc2.97±2.51c<0.001
Exp2294.59±3.42a3.97±2.88a3.17±2.56b2.66±2.57c<0.001
p-value30.1210.002**0.14*

Values are presented as mean±standard deviation. 1Repeated measures ANOVA. 2Repeated measure ANOVA (between subject effects). 3Repeated measure ANOVA (differences between groups over time). abcSame letters means there is no significant difference between times by Tukey’s multiple comparison at a=0.05 in each group.



As a result of comparing the average difference between the three groups over the period of use of dentifrice, there were no statistically significant difference at the measurement point between groups pre-test and three days after the examination (p>0.05). Comparison to at the measurement point three days after the test and one week after the test, test group 1 and group 2 showed brightening of their teeth and statistically significant differences (p<0.05). And the comparison between the time points one week after the test and two weeks after the test showed that the teeth of all groups had brightened, especially the highest mean difference in the second group of tests, and there were statistically significant differences between groups.

Figure 1 shows the change in brightness of each group over the period of use of dentifrice. Two weeks after and before use of dentifrice for each group, the values of the change in brightness according to the Vita Shade Guide were compared. The results showed that the whitening effect of the teeth over the period of use of the dentifrice was minimal, but the whitening effect of teeth was evident in the first group of tests using dentifrice containing only high-cleaning silica and the second group of experiments using dentifrice containing sodium hexametaphosphate. Among them, it showed the brightest tooth whitening effect in the second group of tests.

Figure 1. Line chart for change of brightness score by Vita Shade Guide over period of use of dentifrice.

2) Color change (ΔE*) using VITA Easyshade V

Table 4 is the result of testing with the colorimetric measuring instrument ‘VITA Easy Shaded V’ to check the color change of the teeth. And to check the overall amount of color change, the ΔE* value was calculated by putting the change in Lab* value in the formula among the measurements taken by the instrument. As a result of analyzing the calculated values, there was statistically significant differences between test groups in the amount of changes in the color of the teeth as the period of use increased (p<0.05). As a result of checking the amount of color change by group at each measurement point, in the control group, ΔE* showed no statistically significant difference in the amount of change between measurement points over time (p>0.05). However, test group 1 showed that the ΔE* value at the point of time increases as the period of use of dentifrice increases, with 4.09±2.60 after three days of testing, 6.38±4.12 after one week of testing, and 7.43±5.19 after two weeks of testing. It was shown that there was a statistically significant change (p<0.05). In addition, test group 2 showed the greatest difference in time ΔE* value of 4.02 at test 3 days (4.96 ± 2.86) later and one week later (8.98 ± 2.86). Results of the post-test, there was no difference in hue change one week after the test and two weeks after the test, and that there was a difference from three days after the test.

Table 4 . CIE Lab*(DE) color changes over the period of use of dentifrice

Categories3 days1 week2 weeksp-value1p-value2
ΔE*Con.305.79±3.66a6.59±4.78a6.17±3.73a0.621<0.001
Exp1334.09±2.60a6.38±4.12a7.43±5.19ab0.005**
Exp2294.96±2.86a8.98±4.24b9.34±3.83b<0.001
p-value30.0940.043*0.022*
p-value40.034*0.540

Values are presented as mean±standard deviation. 1Repeated measures ANOVA. 2Repeated measure ANOVA (between subject effects). 3One-way ANOVA. 4Repeated measure ANOVA (differences between groups over time). abSame letters means there is no significant difference between times by Tukey’s multiple comparison at a=0.05 in each group.



Comparing the timing of color changes over the period of use of dentifrice, three days after the test and one week after the test, the color of the teeth in all groups was shown to have brightened and showed statistically significant differences (p<0.05).

Figure 2 represents the ΔE* value change over the period of use of dentifrice. Comparing the value of color change (ΔE*) between two weeks of use of each dentifrice, the results showed that the second group of experiments with dentifrice containing sodium hexametaphosphate was much brighter than the first group with dentifrice containing only control and high-cleaning silica.

Figure 2. Line chart of ΔE* changes according to period of use of dentifrice.

2. Gingival index

Prior to and after two weeks of testing of gingival index for the safety assessment of dentifrice, the results showed that the index was lower in all groups than before the test, but there was no statistically significant difference (Table 5).

Table 5 . Gingival index

n0 days2 weeksp-value
Con.300.40±0.560.37±0.560.326
Exp1330.42±0.560.39±0.560.325
Exp2290.41±0.570.38±0.560.326

Values are presented as mean±standard deviation. p-value obtained from the paired t-test.



3. Questionnaire survey on feeling satisfaction after use of whitening dentifrice

Table 6 shows the results of the feeling satisfaction after two weeks of use of whitening dentifrice. Survey was conducted on a five–point. For the safety feeling assessment resulting from the use of whitening dentifrice, the satisfaction was expressed in order of group 2 (51.7%), group 1 (45.5%) and control (43.3%) in the ‘no symptoms of hypersensitivity’, but there was no statistically significant difference (p>0.05). And in the feeling assessment of gingival inflammation change by dentifrice, all three groups showed the highest response rate of ‘same as other dentifrice’ and showed statistically significant differences (p<0.05).

Table 6 . Feeling satisfaction after whitening dentifrice

CategoryCon.Exp1Exp2p-value
Cold sensitivity symptom0.643
Ache cold sensitivity symptoms0 (0.0)0 (0.0)1 (3.4)
Seem to have ache cold sensitivity symptoms6 (20.0)5 (15.2)3 (10.3)
Not sure7 (23.3)5 (15.2)3 (10.3)
Not likely to be cold sensitivity4 (13.3)8 (24.2)7 (24.1)
No sign of cold sensitivity at all13 (43.3)15 (45.5)15 (51.7)
Gingiva change0.003**
Inflammation in the gingiva0 (0.0)0 (0.0)0 (0.0)
Sensation of gingiva damage0 (0.0)2 (6.1)4 (13.8)
Feeling the same as other dentifrice19 (63.3)28 (84.8)14 (48.3)
Feeling of strong gingiva10 (33.3)3 (9.1)6 (20.7)
Feeling of healthy gingiva1 (3.3)0 (0)5 (17.2)
Cleaning power0.304
No cleaning power at all0 (0.0)0 (0.0)0 (0.0)
No cleaning power1 (3.3)0 (0.0)0 (0.0)
Feeling the same as other dentifrice7 (23.3)5 (15.2)2 (6.9)
Feeling clean18 (60.0)22 (66.7)18 (62.1)
Feeling cleaner4 (13.3)6 (18.2)9 (31.0)
Feeling of use0.000***
Unpleasant sensation0 (0.0)0 (0.0)0 (0.0)
Bad feeling2 (6.7)0 (0.0)0 (0.0)
Feeling the same as other dentifrice7 (23.3)7 (21.2)0 (0.0)
Less refreshing feeling18 (60.0)22 (66.7)9 (31.0)
Very refreshing feeling3 (10.0)4 (12.1)20 (69.0)
Whitening effect0.000***
Not at all0 (0.0)0 (0.0)0 (0.0)
Not so1 (3.3)0 (0.0)0 (0.0)
Similar to other dentifrice7 (23.3)11 (33.3)5 (17.2)
Gotten whiter22 (73.3)21 (63.6)11 (37.9)
Definitely whitened0 (0.0)1 (3.0)13 (44.8)
Total30 (100.0)33 (100.0)29 (100.0)

Values are presented as number (%). Statistically significant differences by chi-square test at a=0.01**, 0.001***.



Meanwhile, although there was no statistically significant difference in the feeling assessment of the cleaning power of whitening dentifrice, the group 2 (93.1%) showed the highest level of satisfaction for “feeling clean” and “feeling cleaner” (p>0.05). And after the use of whitening dentifrice, the group with the highest desirability of 69% in “very fresh and good feeling” was the second group of tests, with test 1 and control showing 12.1% and 10%, respectively, showing statistically significant differences (p<0.05). In the question of whitening effects after using whitening dentifrice, the highest response rate was 44.8% in the second group of tests, ‘I think I’ve definitely whitened’, But test group 1 showed a 3% response rate and control group 0%, indicating the most obvious whitening effect in test group 2 and significant differences between groups (p<0.05).

Discussion

In today’s modern people, appearance is an important factor in success as it gives them confidence in social activities. The aesthetic aspect of the teeth is also increasing the desire for white teeth. So whitening dentifrice, which can effectively promote beauty functions at low cost without being disturbed by daily life, is well received by the public. However, the biggest drawback of whitening dentifrice is that it takes a certain amount of time for the expected whitening effect to occur. This is because whitening dentifrice is classified as quasi drug along with self-whitening agents, limiting the concentration of hydrogen peroxide, known as the effective ingredient of whitening teeth, to less than 0.75% for dentifrice [11]. Therefore, a quick whitening effect can be expected in procedures where high concentration peroxide chemicals such as office tooth bleaching can be used. However, problems are being reported as they can cause side effects such as hypersensitivity, etc. caused by peroxide chemicals [12-14]. Research is being conducted on components that can obtain whitening effects within a safe and short period of time that can replace hydrogen peroxide, but reports on them are still minimal.

Therefore, in this study, the effects of changes in teeth color and teeth color improvement are evaluated after two weeks of use of dentifrice containing high-cleaning silica (Hydrated Silica), and sodium hexametaphosphate (SHMP), a chelating agent that is more effective in preventing and removing colouring than silica in the current dentifrice in circulation. And we checked the safety of dentifrice and the satisfaction level after subjective whitening dentifrice use.

Visual evaluation of the tooth whitening effect using Vita shade guide chromaticity showed a change in brightness as the period of use of dentifrice increased (p<0.05). When comparing of the measured average shade guide score by time, the difference in color change was minimal in the control group, but the difference in color change was seen in the test group 1 and test group 2. Test group 1 containing only high-cleaning silica showed a brighter color change than test group 2 containing sodium hexametaphosphate 3 days after the start of the test. However, test group 1 showed a difference of 1.45 points from 3.15 points a week later to 2.97 points two weeks later, while test group 2 showed a difference of 1.93 points from 3.17 points a week later to 2.66 points two weeks later. As a result, the brightening of the teeth was in Test 1 and 2, but the largest difference in color was identified as Test 2, showing and there was a statistically significant differences (p<0.05). These results are judged to be the result of a combination of hydrated silica, known as a substance that chelating agent and abrasive components of sodium hexametaphosphate, resulting in test group 2. Because Sodium Hexametaphosphate is a polymeric phosphate whose chemical action is similar to that of a pyrophosphate. Sodium pyrophosphate is a metal ion containment action compound and is known to relieve tooth inflammation by inhibiting the formation of stains and tartar in teeth in dentifrice [15]. Also, whitening effect tests in dentifrice containing sodium pyrophosphate are reported in Korea and abroad [16,17]. In the study of Kim et al. [18] reported that sodium pyrophosphate helps whitening effects by removing extrinsic staining. Therefore, Sodium hexametaphosphate, similar to sodium pyrophosphate, is thought that the whitening effect was shown by weakening the reattachment force of the staining substance and affecting the cleaning force.

The assessment of changes in the color of the teeth using VITA Easy Shaded V showed that the color changes significantly as the period of use of dentifrice increases (p<0.05). Gross and Moser [19] reported that if the value of ΔE* is 0-2, the color difference cannot be visually recognized, but 2-3 is slightly recognizable and 3-8 is generally recognizable and 8 or more is clearly recognizable. As a result of comparing the point-in-time measurement mean values of ΔE* in this study, the control group indicated the amount of change in generally recognizable color in a two-week test. However, there was a brightening change in color until one week after the test, and after two weeks, the variation in the reduced color was shown (p>0.05). This is thought to be the result of the dental type silica content contained in the control test dentifrice. Silica is used as abrasive agent, along with dicalcium phosphate and calcium carbonate, among the various ingredients contained in dentifrice. Therefore, it will be responsible for extrinsic discoloration removal and dental plaque removal in dentifrice agent.

Meanwhile, in experimental group 1, which contains only high-cleaning silica, the change in the tone of the color from three days after the test to the last two weeks after the test was improved slightly. This was a generally recognizable color change, such as the control group, although it was found to maintain a brighter tooth color with a higher cleaning force than the normal silica component (p<0.05). However, the test group 2 showed a generally recognizable color change of teeth of 4.96 until three days after the test, but after a week, it was 8.98, showing a rapid color change. And two weeks later the color change was evident up to 9.34 and the whitening effect was clearly identified after two weeks (p<0.05). However, these findings differed from the preceding paper [20-22]’s report that whitening effects from whitening dentifrice showed a noticeable difference in tooth color changes after three weeks. This is thought to be the result of the excellent cleaning power of sodium hexametaphosphate added only to the dentifrice agent used in the test group 2.

Sodium Hexametaphosphate is a polymeric phosphate in which calcium containment action and cleaning action may have been combined together. It is also estimated that the formation of dental plaque and scale was significantly inhibited because calcium component are combined in advance with the saliva in the mouth to produce a chelating compound. The preceding paper also reported that sodium metaphosphate was contained as a dentifrice agent component and thus had the same effect. An et al. [23] reported that the re-staining inhibitory effect was shown in laboratory assessments to confirm whitening effects after whitening treatment. And Kwon et al. [24] reported in clinical trials that there was a cleaning force and removal of the plaque disclosing agent.

On the other hand, the gingival index test was conducted before and after the test as a way to assess the safety of the dentifrice, and satisfaction survey was conducted after the use of the whitening dentifrice. The results showed that the oral condition improved in all groups two weeks after the test, but there was no statistically significant difference (p>0.05). In the feeling satisfaction safety evaluation survey, 51.7% of test group 2, 45.5% of test group 1, and 43.3% of control group for symptoms of hypersensitivity(p>0.05), and in the gingiva change assessment, the highest response rate was ‘feeling the same as other dentifrice’ (p<0.05). These results were different from reports of side effects such as tooth sensitivity and gingiva swelling in whitening dentifrice, which included chemicals such as hydrogen peroxide as the main ingredient [25]. Therefore, it is believed that the test dentifrice used in this study is a safe component without human hazards. In addition, in the feeling satisfaction assessment following the use of dentifrice, sense of cleansing (p>0.05) and feeling refreshed after brushing (p<0.05) and whitening effect of teeth (p<0.05) showed the highest satisfaction level in the test group 2. This is thought to be the result of a certain level of cleaning power due to the chemical action of high-cleaning silica and sodium hexametaphosphate contained in dentifrice when brushing teeth.

This study has limitations that do not reflect subjects’ usual tooth brushing attitudes and eating habits as subjects were selected according to research designs consistent with clinical trials. It is believed that this affected oral hygiene condition. In addition, clinical evaluations are difficult to observe with a long term period and the capture of a large numbers of subjects.

And so, in this study, studies related to maintenance of whitening teeth and re-coloration of teeth have not been reflected from a long-term perspective. Therefore, future research is thought to require research on tooth whitening and tooth staining prevention and removal effects by subdividing tooth staining components from a long-term perspective.

Conclusion

The purpose of this study was to evaluate changes in teeth color and personal satisfaction that result from using dentifrice containing Hydrated Silica and Sodium Hexa-metaphosphate. The study included 92 volunteer subjects, who were divided into three groups: the control group (n=30), experimental1 group (n=33), and experimental2 group (n=29). These groups were subjected to a clinical evaluation for 2 weeks.

First, a comparison of the whitening effect of the dentifrice was conducted using the VITA Shade Guide to assess chromaticity, which revealed that the sodium hexametaphosphate group showed the maximum color change (p<0.05).

Second, the changes in the teeth color were evaluated using the VITA Easyshade V, which revealed that the control group showed generally recognizable tone changes in a 2-week test period (p>0.05), the Hydrated Silica group showed a moderate color change from 3 days after the test, and the Sodium Hexametaphosphate group showed a sharp color change after 1 week and a definite whitening effect after 2 weeks.

Third, a personal satisfaction assessment was performed after using the test dentifrice, which revealed that the sense of cleansing (p>0.05), refreshing feeling after brushing (p< 0.05), and the tooth-whitening effect (p<0.05) were the highest in the sodium hexametaphosphate group.

These results show that the Hydrated Silica and Sodium Hexametaphosphate components in the dentifrice shortened the time taken for teeth whitening, which has typically been a major disadvantage of whitening dentifrice. Therefore, this study is indicative of the use of these components in whitening dentifrice.

Conflict of Interest

No potential conflict of interest relevant to this article was reported.

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