Dental calculus is a calcified deposit that adheres to the surfaces of teeth and roots. It is classified as either supragingival or subgingival calculus based on its location [1]. These deposits harbor a variety of bacteria, and the surface of dental calculus is covered with a bacterial biofilm, characterized by irregular shapes and bacterial colonization [2,3].

The biofilm adhering to dental calculus and teeth is a major cause of periodontal disease and dental caries, as it facilitates the adhesion and growth of various pathogenic bacteria. Oral diseases are largely attributed to microorganisms such as Porphy-romonas gingivalis, Actinobacillus actinomycetemcomitans, and Fusobacterium nucleatum. These gram-negative bacteria are associated with periodontal disease, emphasizing the importance of managing pathogenic microorganisms in the oral cavity [4,5]. When the biofilm calcifies, it forms dental calculus. This calcification is facilitated by calcium and phosphate ions in saliva or gingival crevicular fluid.

The porous nature of the calculus surface allows for the growth and activity of the biofilm, making it a significant clinical factor in the development of oral diseases [6]. To remove bacterial deposits from the teeth and roots, dental prophylaxis and periodontal treatments are performed. However, residual calculus or deposits on the surface can lead to the regrowth of the biofilm [7,8].

Preventing oral diseases caused by bacteria involves reducing the bacterial count in the oral cavity, physically removing the biofilm, and further inhibiting the formation of calculus. One of the most common methods for controlling biofilm and calculus formation is brushing with toothpaste containing various active ingredients.

Kim et al. [9] studied the anti-biofilm effects of toothpaste containing sodium bicarbonate and triclosan. Ma et al. [10] investigated the effects of a toothpaste containing triclosan and ursodesoxycholic acid on gingivitis and calculus formation. Sodium pyrophosphate is known for its inhibitory effect on calculus formation. It works by adsorbing onto calcium in the pellicle, thereby preventing the attachment of salivary proteins to the tooth surface and inhibiting the growth of calculus [11,12]. Dental type silica acts as an abrasive in toothpaste, playing a fundamental role in the removal of biofilm.

The aim of this study is to evaluate the inhibitory effects of toothpaste containing sodium pyrophosphate and dental type silica on dental calculus formation.

1. Study subjects

The study included 90 adult men and women aged between 20 and 50 years who consented to participate and signed a written consent form. Participants were selected based on the following criteria: regular tooth brushing at least twice a day, no restorations or cervical caries, at least 24 remaining teeth, and relatively healthy oral conditions with mild to moderate gingivitis symptoms. The gender and age distribution of the participants are shown in Table 1.

Table 1 . Gender and age distribution of subjects

Gender	Age
	Total	20s	30s	40s
Total	90	46	32	12
Male	36	20	13	3
Female	54	26	19	9

Three types of dentifrice were used in the study: the experimental dentifrice, the comparative dentifrice, and the control dentifrice. The experimental dentifrice contained sodium pyrophosphate, sodium monofluorophosphate, green tea extract, and dental type silica as main components. The comparative dentifrice was formulated without sodium pyrophosphate and dental type silica. The control dentifrice excluded the main components from the experimental dentifrice. Detailed information on each dentifrice is shown in Table 2.

Table 2 . Ingredients and content of dentifrice

Ingredient	A	B	C
Sodium fluorophosphate	0.76%	0.76%	0%
Green tea extract	0.04%	0.04%	0%
Sodium pyrophosphate	3.40%	0%	0%
Dental type silica	13%	0%	0%
Calcium carbonate	0%	10.00%	0%
Formulation component	Appropriate amount	Appropriate amount	Appropriate amount

A: experimental dentifrice for experimental group, B: comparison dentifrice for positive control group, C: control dentifrice for negative control group.

2. Research methods

This study was conducted with the approval of the Dankook University Institutional Review Board (approval numbers DKU 2017-01-009 and DKU 2017-03-024).

The study was conducted over 16 weeks as a parallel, rando-mized, double-blind, controlled trial. Volunteers who signed the consent form were registered and evaluated for eligibility based on inclusion/exclusion criteria. Eligible participants underwent a 1-week run-in period and were then randomly assigned to the experimental group, positive control group, or negative control group, with 30 participants in each group.

All participants underwent dental prophylaxis to remove all calculus from their oral cavity.

All participants were provided with dentifrice to use for 4 months. The experimental group received the experimental dentifrice, the positive control group received the comparative dentifrice, and the negative control group received the control dentifrice. Each participant used the assigned dentifrice three times a day for 3 minutes, using the Bass technique for tooth brushing, over the 16-week period. All participants were given the same toothbrush to ensure consistent brushing conditions.

Participants underwent oral examinations at baseline, and at 1, 2, 4, 8, and 16 weeks. The simplified calculus index (Simplified Oral Hygiene Index) was used to measure and record the presence of calculus in the oral cavity. The calculus index was scored as follows: 0 points for no calculus, 1 point for calculus on up to one-third of the tooth surface, 2 points for calculus on up to two-thirds of the tooth surface or non-extensive subgingival calculus, and 3 points for calculus on more than two-thirds of the tooth surface or extensive subgingival calculus.

The experimental data were entered using Microsoft Office Excel 2016 (Microsoft, Seattle, U.S.A.) and analyzed using SPSS Statistics version 23.0 (IBM, New York, U.S.A.). Paired t-tests were used for within-group comparisons, and one-way ANOVA was used for between-group comparisons. Scheffe’s test was used for post hoc analysis.

1. Changes in calculus index

After 4 weeks, the dental calculus index in the experimental group using the test dentifrice was 0.0056, compared to 0.1500 in the positive control group and 0.1556 in the negative control group, showing statistically significant differences between the experimental group and both control groups (p<0.05). After 16 weeks, the experimental group had an index of 0.2167, the positive control group 0.3167, and the negative control group 0.4833, again demonstrating statistically significant differences between the experimental group and both control groups (p<0.05) (Table 3).

Table 3 . Changes of dental calculus index

Group		Base	1 week	After 2 weeks	After 4 weeks	After 8 weeks	After 16 weeks
E	Mean	0.0000	0.0000	0.0000	0.0056a	0.0722a**	0.2167a**
	SD	0.0000	0.0000	0.0000	0.0304	0.0840	0.3191
P	Mean	0.0000	0.0000	0.0722	0.1500ab**	0.1889ab**	0.3167ab**
	SD	0.0000	0.0000	0.2175	0.2848	0.3087	0.4514
N	Mean	0.0000	0.0000	0.0056	0.1556b**	0.2667b**	0.4833b**
	SD	0.0000	0.0000	0.0304	0.2696	0.3518	0.4318
p-value†		-	-	0.054	0.018	0.026	0.041

E: experimental group, P: positive control group, N: negative control group, SD: standard deviation.

^†p-value by one-way ANOVA, **p<0.01 by paired t-test between base and after, ^absame letter means no statistical difference by Scheffe test.

2. Changes in dental calculus formation rate

After 4 weeks, the rate of dental calculus formation in the experimental group using the test dentifrice was 3.3%, compared to 36.7% in both the positive and negative control groups, indicating that the experimental group had a rate of dental calculus formation that was over 33% lower than both control groups. Additionally, after 16 weeks, the dental calculus formation rates were 50% in the experimental group, 56.7% in the positive control group, and 76.7% in the negative control group, showing that the experimental group had lower rates by 6.7% and 26.7%, respectively, compared to the control groups (Table 4).

Table 4 . Changes of dental calculus prevalence

Group	N		Base	1 week	After 2 weeks	After 4 weeks	After 8 weeks	After 16 weeks
E	30	n (%)	0 (0.0)	0 (0.0)	0 (0.0)	1 (3.3)	13 (43.3)	15 (50.0)
P	30	n (%)	0 (0.0)	0 (0.0)	4 (13.3)	11 (36.7)	13 (43.3)	17 (56.7)
N	30	n (%)	0 (0.0)	0 (0.0)	1 (3.3)	11 (36.7)	16 (53.3)	23 (76.7)

E: experimental group, P: positive control group, N: negative control group.

3. Changes in inhibitory effect rate on dental calculus formation

Compared to the negative control group, the experimental group showed an inhibitory effect rate of over 90% after 4 weeks and over 50% after 16 weeks (Table 5).

Table 5 . Inhibitory effect rate on dental calculus

Effect rate	After 4 weeks	After 8 weeks	After 16 weeks
Inhibitory effect rate compared with the negative control groupa	93.75	74.07	54.17
Inhibitory effect rate on dental calculusb	96.7	56.7	50.0

^aComparison between groups based on negative control group (negative control group−experimental group)/negative control group×100.

^bPercentage of subjects without changes in dental calculus index (number of subjects without change in dental calculus index)/(total number of subjects)×100.

Dental calculus refers to calcified deposits formed on the surfaces of teeth or other oral structures, classified as supragingival or subgingival based on their location [13]. The surface of dental calculus is covered with dental plaque, which harbors various bacteria, making it a major cause of periodontal disease and dental caries. To prevent oral diseases caused by bacteria, numerous studies have been conducted, with tooth brushing using dentifrice being the most widely used method. Dentifrice studies aim to achieve higher oral disease prevention effects through various ingredient research. Dong et al. [11] reported that brushing with dentifrice containing Triclosan, pyrophosphate, and tranexamic acid showed no significant statistical difference, but demonstrated a 7.4% and 9.6% inhibition after 4 and 8 weeks, respectively. Ma et al. [14] found that brushing with dentifrice containing 3.5% tetra sodium pyrophosphate, 0.5% hydroxyapatite, and vitamin E showed no significant statistical difference after 4 weeks, but after 12 weeks, the dental calculus index was 10.46 in the control group and 5.06 in the experimental group, showing a statistically significant difference.

Internationally, Lobene et al. [15] claimed that brushing with dentifrice containing sodium pyrophosphate reduced calculus formation, and Cohen et al. [16] reported that brushing twice daily for 12 weeks with dentifrice containing 1.3% soluble pyrophosphate inhibited supragingival calculus formation by 54.4%.

This study aimed to investigate the inhibitory effect of dentifrice containing sodium pyrophosphate and dental type silica on calculus formation, involving 90 adult participants over 16 weeks, brushing three times a day with the same toothbrush using the Bass technique.

Before starting the experiment, all calculus in the participants’ oral cavities was removed through dental prophylaxis.

After 4 weeks, the dental calculus index in the experimental group using the test dentifrice was 0.0056, compared to 0.1500 in the positive control group and 0.1556 in the negative control group, showing statistically significant differences between the experimental group and both control groups (p<0.05). After 16 weeks, the experimental group had an index of 0.2167, the positive control group 0.3167, and the negative control group 0.4833, demonstrating statistically significant differences between the experimental group and both control groups (p<0.05).

After 4 weeks, the rate of dental calculus formation in the experimental group using the test dentifrice was 3.3%, compared to 36.7% in both the positive and negative control groups, indicating that the experimental group had a rate of dental calculus formation that was over 33% lower than both control groups. Additionally, after 16 weeks, the dental calculus formation rates were 50% in the experimental group, 56.7% in the positive control group, and 76.7% in the negative control group, showing that the experimental group had lower rates by 6.7% and 26.7%, respectively, compared to the control groups.

Compared to the negative control group, the experimental group showed an inhibitory effect rate of over 90% after 4 weeks and over 50% after 16 weeks.

These results confirm that using dentifrice containing sodium pyrophosphate, sodium monofluorophosphate, green tea extract, and dental type silica can be expected to have effective inhibitory effects on dental calculus formation.

To confirm the inhibitory effect of dentifrice containing sodium pyrophosphate, sodium monofluorophosphate, green tea extract, and dental type silica on dental calculus formation, an experiment was conducted with 90 participants over 16 weeks. The participants were divided into three groups: 30 in the experimental group using the complete dentifrice, 30 in the positive control group using dentifrice without sodium pyropho-sphate and dental type silica, and 30 in the negative control group using dentifrice without the main ingredients. After 16 weeks of using the dentifrices, the following conclusions were drawn:

1. The experimental group showed statistically significant differences in dental calculus index compared to both control groups from 4 weeks onwards (p<0.05).

2. The inhibitory effect rate of the experimental group compared to the negative control group was 93.75% after 4 weeks, 74.07% after 8 weeks, and 54.17% after 16 weeks.

3. The inhibitory effect rate of the experimental group was 96.70% after 4 weeks, 56.70% after 8 weeks, and 50.00% after 16 weeks.

These results confirm that using dentifrice containing sodium pyrophosphate, sodium monofluorophosphate, green tea extract, and dental type silica can be expected to have effective inhibitory effects on dental calculus formation.

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