Toothbrushing is the most commonly used method to prevent oral diseases. To prevent oral diseases effectively, it is necessary to select appropriate toothbrushes, brushing methods and toothpaste according to one’s oral condition [1]. Toothpaste, which mainly composed of the abrasive agent, detergent, binding agent, and humectant, is an auxiliary agent that helps effective cleaning of the tooth surface. Among the components, abrasive agent has the oral disease prevention, the halitosis control, and the aesthetic improvement effect through the physical removal of the dental plaque and polishing action [2-4].

Abrasive agent is a component of a toothpaste, that triggers the removal of foreign substances and polishing of the tooth surface. Various types of abrasive agent components are mixed with different combination ratios for each toothpaste, and thus abrasivity of the toothpastes varies. Abrasive agent should exert sufficient abrasivity, however when it is too excessive, the tooth could be worn out more than necessary which can cause hypersensitivity [5]. Even if a toothpaste has proper abrasion force, damage to the hard tissue or soft tissue of the teeth may occur, and it may be different from person to person by the number of brushing times, the method and the strength of brushing.

In addition, various abrasive agents are being used according to its effect. In particular, calculus needs proper management as it reproduce the bacteria causing the oral diseases. When calculus is already formed and calcified, it is difficult to remove by non-professional management and therefore, periodic calculus removal is needed. In addition, the toothpaste that can inhibit the formation of calculus is recommended to those with a remarkable formation of calculus [6].

There are several materials used as abrasive agent; dicalcium phosphate dihydrate (CaHPO₄, 2H₂O), calcium carbonate precipitated (CaCO₃), sodium meta phosphate insoluble (NaPO₃), calcium pyrophosphate (Ca₂PO₇), dicalcium phosphate anhydrous (CaHPO₄), tricalcium phosphate (Ca₃PO₄), and silica etc. [3].

In this paper, the dental type silica, anhydrous silicon dioxide, included in both the control and the experimental group toothpaste used. Radioactive Dentin Abrasion (RDA) value of dental type silica is known as 100; also the particles are relatively homogeneous. RDA value indicates the relative abrasion for calcium pyrophosphate, and is based on abrasion of the calcium pyrophosphate which is known as 100. The ground calcium carbonate, one of the abrasive agent added to this experimental group toothpaste, is mechanically shattered from limestone or calcite, and it has a particle size of 1-3 mm or more. Defined in British Standards Institution (BSI), the appropriate RDA value is from 100 to 200 [7]. Camargo et al. [8] studied about the particle size and the relative tooth abrasivity of dental type silica and calcium carbonate, the dental type silica had larger particle size and higher abrasivity. On the other hand, Li et al. [9] showed that calcium carbonate had more abrasivity than dental type silica because of its irregular and rough particle shape. This conflicting result is thought to be due to the different particle size, shape and content of the abrasive agent that is contained in each toothpaste. In addition, even if two different toothpastes contain silica, the result varies in abrasion depending on the type of silica [10]. This is because the hydrous silicate has a lower abrasion than silicon dioxide.

The dental type silica contained in the toothpaste is used for inhibiting plaque/calculus deposition and preventing from the teeth contamination [11]. The calcium bicarbonate and the hydrous silicate are widely utilized as abrasives of the toothpastes. Calcium bicarbonate calcium bicarbonate is about 3 in hardness, which is lower than enamel with 6.7 in hardness. The hydrous silicate is a silicon dioxide which forms in a water-soluble state, whose particle is larger than a dental type silica. The purpose of this study is to evaluate the abrasivity of toothpaste with the addition of calcium bicarbonate and hydrous silicate with the comparison of the abrasivity of the other toothpastes, which only contained conventional dental type silica.

1. Materials

The experiment was performed in two groups. As for Table 1, the control group was used the toothpaste containing only dental type silica, and as an experimental group, the toothpaste containing calcium carbonate and silicon dioxide as well as dental type silica was used.

Table 1 . Type and contents of toothpastes

	Main ingredient	Addition agent
Control group	Dental type silica 13% (NF)
Experimental group	Dental type silica 13% (NF)	Calcium carbonate silicon dioxide

2. Specimens

The specimens used in this study were fabricated using the extracted bovine teeth without dental caries lesions. The extracted bovine teeth were cut into 3 mm diameter and made into circular specimens by using low speed handpieces. After that, the surface was polished by sandpaper (Grade 600, 1500, 2000) after being buried in a cylindrical acrylic mold with an inner diameter of 8 pie, an outer diameter of 12 pie, and a height of 5 mm. A total of 16 specimens were produced, 8 for each group, and the mass of the specimen was measured by the precision electronic scale (Figure 1).

Figure 1. Bovine tooth block.

3. Methods

Scrub toothbrushing stroke device was used for toothbrushing (Figure 2). After attaching the block to the water tank to where the brush of toothbrush located, the 2:1 ratio suspension of the toothpaste and distilled water was filled, and 20,000 brushing reciprocating exercises were performed per block. The mass of the block was measured before and after the brushing application using the precision electronic scale (Figure 3).

Figure 2. Tooth brushing machine.

Figure 3. Precision Electronic scale.

4. Calculation of abrasivity

The degree of tooth abrasivity was measured by weight-loss technique. Weight of specimens was measured before and after brushing for each. the abrasivity was calculated using the following equation:

5. Statistical analysis

Statistical analysis was done via IBM SPSS Statistics 24.0 (IBM Inc., Armonk, New York, USA). The comparison between weight of blocks before and after the brushing was performed through paired t-test, and the comparison between the products was performed by using two sample t-test.

The mass change before and after brushing each block has shown at Table 2. The average abravisity of the block was about 0.5871±0.1 in the control group and about 0.6114±0.0618 in the experimental group, but there was no significant difference. In the comparison between before and after brushing (a, b), there was significant difference (p<0.05). On the other hand, in the comparison between the products (c, d), there was no significant difference (p>0.05).

Table 2 . Change of mass before and after brushing tooth by block

	Bovine tooth block No.	*Weight before brushing (g)a	*Weight after brushing (g)b	Abravisity (%)	Abrasivity average±standard deviation
Control group	#1	0.6047	0.6009	0.6284	*0.5871±0.1c
	#2	0.6468	0.6441	0.4174
	#3	0.6216	0.6185	0.4987
	#4	0.5900	0.5861	0.6610
	#5	0.6052	0.6016	0.5948
	#6	0.6475	0.6439	0.5560
	#7	0.6223	0.6186	0.5946
	#8	0.5902	0.5858	0.7455
Experimental group	#9	0.6299	0.6263	0.5715	*0.6114±0.0618d
	#10	0.6046	0.6008	0.6285
	#11	0.5974	0.5942	0.5357
	#12	0.6425	0.6387	0.5914
	#13	0.6305	0.6263	0.6661
	#14	0.6054	0.6012	0.6938
	#15	0.5971	0.5939	0.5359
	#16	0.6432	0.6389	0.6685

^aWeight before brushing (g).

^bWeight after brushing (g).

^cAbrasivity average of control group.

^dAbrasivity average of experimental group.

Calculus is produced by calcification of dental plaque or glycoproteins in the dental plaque, and provides an environment that is prone to the reproduction of bacteria that cause periodontal disease or dental caries. Calculus itself does not cause periodontitis. However, due to the bacterial membrane above it, it has the possibility of causing periodontitis and therefore, it is classified as a secondary etiology of periodontitis. Thus, it is important to remove and prevent calculus in order to prevent periodontal disease [6,12].

Abrasive agent of the toothpaste should have abrasivity to remove the dental plaque on the surface of the tooth. However, since the hard tissue of the tooth can be damaged by the abrasion force, it is important to have a proper degree of abrasivity. The degree of tooth abrasion of the toothpaste differs according to the content of the abrasive agent [13]. The higher the content of the abrasive agent, the higher the degree of abrasion. This suggests that the more the abrasive agent content increases, the higher the cleaning effect of the toothpaste, and simultaneously the abrasion of the teeth will increase. As proved from previous studies, Berry [14] explained that the more the content of the abrasive agent increases, the more effective the inhibition of the formation of plaque. Paik et al. [15] explained that the more the content of the abrasive agent increases, the more the cervical abrasion.

Miller et al. [16] measured the abrasivity of powdered toothpaste in 1907, and many researches have been conducted on the relation between various toothpastes and tooth abrasion. Franzò et al. [17] compared the abrasion of the teeth according to time and change of the concentration of the toothpaste. In addition, the relative tooth abrasion of the toothpaste marketed in Korea was measured and analyzed in 2011 [4]. In addition, there are comparative studies between evaluation methods to measure relative tooth abrasion and studies on the suitability evaluation of newly developed toothpastes by international standards. The weight-loss technique is the first method of measuring abrasivity which was presented by Kim [18] in 1975. Since then, abrasivity test with copper plate and radioactive method was introduced and used for measuring abrasivity [4].

This research compared the abrasivity of pre-marketed dental silica-containing toothpaste and new product that contains dental silica, ground calcium carbonate and hydrous silicon dioxide. The result shows abrasivity was high in the toothpaste containing ground calcium carbonate and hydrous silicon dioxide, but it was not statistically significant.

In a clinical study comparing a toothpaste that contains 0.8% monofluorophosphate and silica with a toothpaste containing monofluorophosphate, silica, 0.3% triclosan and 0.75% zinc citrate, the toothpaste which contained 0.3% triclosan and 0.75% zinc citrate had effect in relieving the gingivitis, simultaneously controlling the dental plaque and supragingival calculus formation [19]. Sowinski et al. [20] also conducted a comparative study on the Volpe-Manhold Calculus Index score of the experimental subjects containing triclosan and PVM/MA compared to the conventional pre-marketing toothpaste, and the results showed that the formation of supragingival calculus was suppressed.

This study examined the cleaning power of the toothpastes through the analysis of the comparison of abrasivity among different toothpastes. The abrasivity was higher in the toothpaste with the addition of ground calcium bicarbonate and hydrous silicon dioxide than the conventional toothpaste, and this can be inferred to have more effect on inhibiting calculus formation by effectively removing dental plaque. This is similar to the results of Svatun et al. [19] and Sowinski et al. [20].

However, there was no significant difference in the comparison among the toothpastes, so it is necessary to conduct further study on the increasing contents of calcium bicarbonate and silicon dioxide, or to add other abrasive components to the toothpaste with various content rations. In addition, this experiment has limitations in that it was conducted using the bovine teeth rather than human teeth, the sample was small and the experimental period was not long enough, only quantitative analysis of the abrasion was performed, and the experiment was conducted in the laboratory, so it did not confirm the direct effect on the inhibition of calculus formation. Therefore, further studies on the effects of supplementation of specimens, longer-term studies, qualitative studies on the abrasion, and clinical effects on human teeth are needed.

In this research, the effects of ground calcium carbonate and hydrous silicon dioxide on the abrasivity of the toothpaste were investigated by measuring weight of bovine tooth block of pre- and post-toothbrushing reciprocating motions in two groups.

In the comparison between before and after brushing, there was significant difference (p<0.05). On the other hand, the comparison between the products, there was no significant difference (p>0.05).

The experimental group with ground calcium carbonate and hydrous silicon dioxide showed higher abrasivity than the control group. Therefore, it is considered that the addition of ground calcium carbonate and hydrous silicon dioxide will increase the abrasivity of the toothpaste, which will be effective in suppressing calculus formation.

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