Evaluation of tea stain removal efficacy of ficin

Abstract

The aim of the present study was to investigate the stain removal efficacy and whitening effect of ficin with different concentrations comparing with commonly used whitening agents. Ninety enamel slices were obtained from bovine mandibular permanent incisors and randomly divided into 15 groups (n = 6), which were treated with five different concentrations of CP, STPP, and ficin respectively. Colour changes were measured before and after treatments based on the International Commission on Illumination (CIE) L* a* b* colour measurement system. The changes in the surface morphology of enamel slices before and after different treatments, and the degree of enamel damage after treatment with ficin were characterised by scanning electron microscopy (SEM) at different magnifications. The results show that when the concentration of CP and STPP was less than 0.8% and 8%, the change of ΔE (overall colour differences) was not significant (P > 0.05), but when the concentration of ficin was less than 0.1%, the change of ΔE was significant (P < 0.05). To study this issue, we performed dummy variable regression and confirmed that there was no significant difference in the ΔE between 0.1% and 0.2% ficin group (P = 0.089), and it was better than the other 13 groups (P < 0.05). Conclusively, we found that the tea stain removal efficacy of ficin was better than that of low-concentration CP and STPP which were originally introduced into whitening toothpaste as chemical whitening ingredients.

Keywords:
ficin; carbamide peroxide; sodium tripolyphosphate; cysteine proteinases; tooth bleaching

1 Introduction

In recent decades, many studies have reported that CP and STPP were originally introduced into whitening toothpaste as chemical whitening ingredients (Cooper et al., 1992; Farawati et al., 2019; Wongpraparatana et al., 2018). However, the acidic and alkaline environment produced by CP and STPP, respectively, in a liquid environment can cause different degrees of damage to the enamel. Long-term application of > 10% STPP and > 1% CP in whitening toothpaste can cause enamel demineralisation (Milleman et al., 2017; Viscio et al., 2000). The aggressive bleaching agents applied in overnight bleaching can also damage the organic matrix in the tooth, especially dentin (Fearon, 2007), and changes in tooth surface structure and increased tooth sensitivity can occur (Markowitz, 2010). Additionally, the decolourisation power of low-concentration CP and STPP has been questioned. Therefore, safer and more effective whitening ingredients that bypass these limitations need to be developed.

Salivary proteins are an important component of salivary pellicle and have a high affinity for hydroxyapatite (Schipper et al., 2007). In addition, salivary proteins are the basis of extrinsic staining and can combine with the polyphenol pigments in tea (Yao et al., 2011). Tea is a common global beverage; however, excessive tea consumption can adversely affect our dental and oral health. Tea pigments are easily deposited on the surface of the teeth, causing extrinsic staining that hampers dental beauty, thereby limiting people's social activities and adversely affecting their psychological health.

It is worth noting that in recent years, cysteine proteases, such as papain, have been shown to possess a strong hydrolytic effect on salivary proteins and the β-casein/theaflavin complex (Yao et al., 2013; Yao et al., 2012). However, the decolourisation effect of cysteine proteases was not evaluated in these studies. Among the cysteine proteases (endopeptidases) ficin, bromelain, and papain, Ficin is more adaptable to the environment and relatively more stable (Devaraj et al., 2008). Therefore, compared with other chemical whitening ingredients, the decolourisation effect of ficin warrants further study. In the present study, we used low concentrations of CP and STPP, which are commonly used in whitening toothpaste, as controls to further evaluate the whitening effect of ficin.

2 Materials and methods

2.1 Study design

The present study’s sample size estimation method was based on the comparison of multiple sample means in a completely random design. The sample size was calculated using PASS 11, which is a trademark product of Dr. Jerry L. Hintze and NCSS. According to the results of pre-experiments, we obtained a standard deviation of ΔE (overall colour differences) for each experimental group ≤ 0.3. Setting up alpha = 0.05, and power = 0.9, the sample size calculated using the PASS 11 software was 5.6. Therefore, 90 samples were randomly divided into 15 groups (n = 6) and treated with five different concentrations of the three substances.

2.2 Materials

We purchased ficin, L-cysteine, ethylenediaminetetraacetic acid, CP, and STPP from Sigma Chemical. Newly extracted bovine mandibular permanent incisors purchased from Guangdong, China, aged 2-3 years old, were cleaned using ultrasound and stored in a 0.1% thymol solution at 4 °C (Devaraj et al., 2008). Then we prepareted the enamel slice, ninety-six enamel slices (4 mm × 3 mm × 2 mm) were obtained from the middle 1/3 of the buccal halves of each tooth by a low-speed saw (Isomet, Buehler) with a cutting precision of 0.1 mm under constant water cooling. The experimental workflow is presented in Figure 1. Enamel slices were individually embedded in colourless translucent acrylic resin, keeping the enamel surfaces unsealed for treatment. To obtain flat standardised enamel surfaces, the surfaces were serially polished using 600- to 3000-grit silicon carbide paper, with water as a cooler. Subsequently, they were polished with 50 nm aluminium oxide slurry and polishing cloths, followed by rinsing with running water to remove debris layers (Azer et al., 2010). All the surfaces of enamel slices were devoid of stain, enamel cracks or fractures, caries, and other defects on the buccal surfaces as seen by a stereo microscope (Nikon 88286, Tokyo) at a magnification of 40 × (Attin et al., 2007; Turssi et al., 2010). To check whether the preparation procedure affected the enamel surface characteristics, we performed atomic force microscopy (AFM, NanoscopeIIIa, Veeco) and water contact angle measurements (JC2000D, Zhongchen Digital Technology). The water contact angles and roughness of the prepared enamel slices were 46 ± 10° (mean ± SD) and < 2 nm, respectively, as shown in Figure 2, consistent with earlier reports on bovine and human enamel (Landa et al., 1997; Sun et al., 2011). We collected unstimulated whole saliva from 25 donors with normal oral and general conditions using sterile disposable containers and stored at 4 °C. The collected saliva was centrifuged at 12000 rpm for 20 min, and the supernatant was collected and stored at -80 °C until later use (Ericson & Nordlund, 1993).

Figure 1
Comprehensive flow chart of the present study.

Figure 2
Surface parameters of enamel slices. (A) roughness of the enamel slices assessed using atomic force microscopy (AFM); (B) contact angle of the enamel slices.

2.3 Staining model

The staining solution was prepared using tea in the following manner: black tea purchased from Earl Grey Tea Company was ground, and then 2.5 g of the ground mix was boiled in 225 mL water for 3 min, allowed to cool, filtered with Whatman #1 filter paper (pore size: 11 μm), and diluted with water to a final volume of 250 mL (Joiner et al., 2003).

We studied the decolourisation effect of ficin on the surface of bovine teeth using a cyclic immersion staining procedure based on a model established by previous studies, with some modifications. The samples were soaked in prepared saliva (37 °C, pH = 6.9) for 60 min, rinsed with deionised water for about 3 s, soaked in tea solution (37 °C, pH = 6.9) for approximately 60 min, and rinsed again with deionised water for 3 s. This was the cycle of soaking and dyeing. When the total colour difference of all samples was ≥ 2.5, the dyeing cycle was terminated.

2.4 Treatment procedure

Ninety coloured enamel slices were randomly divided into 15 treatment groups as follows:

• Group CP: Coloured enamel slices of five treatment groups (n = 6) were immersed in 10 mL of 0.2%, 0.4%, 0.6%, 0.8%, and 1.0% CP solutions for 30 min.

• Group STPP: Coloured enamel slices of five treatment groups (n = 6) were immersed in 10 mL of 2%, 4%, 6%, 8%, and 10% STPP solutions for 30 min.

• Group ficin: Coloured enamel slices of five treatment groups (n = 6) were immersed in 10 mL of 0.0125%, 0.025%, 0.05%, 0.1%, and 0.2% ficin solutions for 30 min.

All the above treatments were carried out at 37 °C, pH 7.4, and an ionic strength of 10 mM.

2.5 Colour measurement and observation

A spectrophotometer (PR-655 Spectra Scan, Photo Research) was used to measure the colour of the teeth based on the CIE L*a*b* colour space system (0-degree observer and illuminant D₆₅). Before each measurement session, the spectrophotometer was calibrated using a white reflectance standard, according to the manufacturer’s protocol. The middle region of each specimen was measured in a circular area of 1.5 mm diameter at a distance of 95 mm. To ensure that the same area of each sample was surveyed every time, an optical table equipped with a standard light source (a custom sample holder) was used to position the specimens. Colour measurements were taken before staining, after staining, and after treatment. The differences in the L*, a*, and b* values were expressed as ΔL*, Δa*, and Δb*, where ΔL* = L*_{post-intervention} - L*_{pre-intervention}, Δb* = b*_{post-intervention} - b*_{pre-intervention}, and Δa* = a*_{post-intervention} - a*_{pre-intervention}. The overall colour differences were calculated using the following expression: ΔE = [(ΔL*)² + (Δa*)² + (Δb*)²]^1/2. The temperature was controlled between 18 and 25 °C, and the relative humidity was controlled between 50% and 60%. L*, a*, and b* measurement was repeated three times, and the average value was recorded.

The surface morphology of enamel slices randomly selected from the 0.1% ficin, 0.2% CP, and 2% STPP groups before and after treatment was observed by scanning electron microscopy (SEM; SEM-EDS, LEO 1530, GER) at 40000 ×. The enamel slices were randomly selected from the 0.1% ficin group before and after treatment. After gold spraying, vacuuming, and ultrasonic cleaning with alcohol, the surface morphology within the 10 × 10 μm range was observed by SEM at a magnification of 2500 ×.

2.6 Statistical analysis

All statistical analyses were performed using the SPSS software (version 13.0; IBM). Data of ΔL*, Δa*, Δb*, and ΔE of the enamel slices are expressed as the mean ± SD. One-way ANOVA was used to test the ΔL*, Δa*, Δb*, and ΔE values before and after treatment with different concentrations of CP, STPP, and ficin. Statistical significance was set at P < 0.05. Considerding of the rationality of explanation of results,using the 0.2% ficin group as the reference group, and all the other 14 groups as dummy variables, dummy variable regression was used to test the ΔE values of all the 15 groups.

3 Results

3.1 Changes in colour values of all the specimens before and after staining

The mean and standard deviation values of the changes in L*, a*, and b* of all specimens before and after staining are shown in Table 1. The changes in b* and L* indicate that the colour became more yellow and dark. However, the changes in the red/green hue (a*) were weak.

Table 1
The means and standard deviations of color values of all the specimens before and after staining.

Color values	L*0	L*1			ΔL*
	66.21 ± 4.31	64.79 ± 4.14			-1.42 ± 0.19
a*0	-2.86 ± 0.56
b*0	-5.05 ± 2.38
a*1		-3.07 ± 0.49
b*1		-2.69 ± 2.37
Δa*					-0.22 ± 0.27
Δb*					2.36 ± 0.17
ΔE			2.78 ± 0.12

3.2 Changes in ΔL*, Δa*, Δb*, and ΔE of stained enamel slices after treatment with ficin, CP, and STPP

Changes in ΔL*, Δa*, Δb*, and ΔE values of the enamel slices after treatment with different concentrations of ficin, CP, and STPP are shown in Table 2. After treatment, ΔL*, Δb*, and ΔE values were observed, except for Δa*. In groups treated with ficin, the ΔL*, Δb*, and ΔE values increased with increasing ficin concentration (P < 0.05), but there was no further increase at ficin concentration ≥ 0.1%. Further, in groups treated with CP and STPP, when C_CP ≤ 0.8% and C_STPP ≤ 8%, the ΔL*, Δb*, and ΔE values did not increase with increasing concentration. However, when C_CP ≥ 0.8% and C_STPP ≥ 8%, the Δ L*, Δ b*, and Δ E values increased with increasing concentration (P < 0.05). After performing dummy variable regression (Table 3), the ΔE of the 0.2% ficin-treated group was equal to that of the 0.1% ficin-treated group (P = 0.089), but more significant than that of the other 13 groups (P < 0.05).

Table 2
The ΔL*, Δa*, Δb* and ΔE values of stained bovine enamel slices after treatment with ficin, carbamide peroxide and sodium tripolyphosphate under different concentrations.

	Concentration	ΔL*	Δa*	Δb*	ΔE
Ficin	0.0125%	0.46 ± 0.36*	-0.05 ± 0.05	-0.38 ± 0.08*	0.50 ± 0.07*
	0.0250%	0.57 ± 0.08*	-0.05 ± 0.04	-0.58 ± 0.07*	0.81 ± 0.08*
	0.0500%	0.97 ± 0.16*	-0.06 ± 0.04	-0.96 ± 0.09*	1.37 ± 0.12*
	0.1000%	1.10 ± 0.16*	-0.18 ± 0.13	-1.68 ± 0.20*	2.02 ± 0.18*
	0.2000%	1.30 ± 0.11	-0.07 ± 0.06	-1.78 ± 0.21	2.21 ± 0.20
Carbamide peroxide	0.2%	0.53 ± 0.08	0.03 ± 0.03	-0.31 ± 0.34	0.69 ± 0.12
	0.4%	0.53 ± 0.10	0.07 ± 0.05	-0.41 ± 0.13	0.69 ± 0.04
	0.6%	0.58 ± 0.07	0.04 ± 0.02	-0.43 ± 0.10	0.73 ± 0.08
	0.8%	0.96 ± 0.08*	0.04 ± 0.04	-0.75 ± 0.14*	1.29 ± 0.11*
	1.0%	1.22 ± 0.25*	0.03 ± 0.07	-1.02 ± 0.21*	1.61 ± 0.22*
	2.0%	0.39 ± 0.12	0.04 ± 0.03	-0.56 ± 0.22	0.70 ± 0.19
	4.0%	0.52 ± 0.22	0.05 ± 0.02	-0.59 ± 0.22	0.81 ± 0.23
Sodium tripolyphosphate	6.0%	0.55 ± 0.14	0.03 ± 0.01	-0.80 ± 0.20	0.98 ± 0.23
	8.0%	0.86 ± 0.26*	0.04 ± 0.03	-0.88 ± 0.23*	1.24 ± 0.28*
	10.0%	1.21 ± 0.24*	0.07 ± 0.03	-1.12 ± 0.48*	1.69 ± 0.34*

• Within the same column, the values (mean ± SD) with asterisk are significantly different (one-way ANOVA analysis and SNK-q test, P < 0.05).

Table 3
Regression coefficients of the dummy variable regression of theΔE values of 15 groups.

Model	Unstandardized coefficients		Standardized coefficients	t	Sig.	95.0% CI for Beta
	Beta	SE	Beta			Lower bound	Upper bound
Constant	2.210	0.077		28.860	0.000	2.057	2.363
0.2% ficin	Reference
0.2% Carbamide peroxide	-1.525	0.108	-0.701	-14.082	0.000	-1.741	-1.309
0.4% Carbamide peroxide	-1.520	0.108	-0.699	-14.036	0.000	-1.736	-1.304
0.6% Carbamide peroxide	-1.477	0.108	-0.679	-13.635	0.000	-1.692	-1.261
0.8% Carbamide peroxide	-0.920	0.108	-0.423	-8.495	0.000	-1.136	-0.704
1.0% Carbamide peroxide	-0.600	0.108	-0.276	-5.540	0.000	-0.861	-0.384
2.0% Sodium tripolyphosphate	-1.515	0.108	-0.696	-13.989	0.000	-1.731	-1.229
4.0% Sodium tripolyphosphate	-1.415	0.108	-0.651	-13.066	0.000	-1.631	-1.199
6.0% Sodium tripolyphosphate	-1.233	0.108	-0.576	-11.389	0.000	-1.449	-1.018
8.0% Sodium tripolyphosphate	-0.970	0.108	-0.446	-8.957	0.000	-1.186	-0.754
10.0% Sodium tripolyphosphate	-0.520	0.108	-0.239	-4.802	0.000	-0.736	-0.034
0.0125% Ficin	-1.717	0.108	-0.789	-15.852	0.000	-1.932	-1.501
0.0250% Ficin	-1.402	0.108	-0.644	-12.943	0.000	-1.617	-1.186
0.0500% Ficin	-0.843	0.108	-0.388	-7.787	0.000	-1.059	-0.628
0.1000% Ficin	-0.187	0.108	-0.086	-1.724	0.089	-0.402	0.029

• Using the group of 0.2% ficin as the reference group, and all the other 14 groups as dummy variables. The variables in the first column of tables were the dummy variables of the corresponding experimental groups. CI: confidence interval; t: Statistics for significance test of Beta; Sig: Corresponding p value; SE: standard error.

3.3 Surface morphology of stained enamel slices after treatment with ficin, CP, and STPP

Comparing the SEM images of bovine enamel slices before and after staining, before staining, the bovine enamel slices with evident porosities, depressions, cracks and superficial irregularities (Figure 3A), after staining, we observed that the morphology of the enamel disappeared after staining and was replaced by layers of stacked lumps (Figure 3B). The change in morphology of the enamel slice surface after treatment with CP (concentration: 0.2%) was not prominent (Figure 4A). However, the morphology of the enamel slice surface after treatment with STPP (concentration: 2%) showed evident changes, particularly thinned layers of stacked lumps, reduced volume, and loosened structure (Figure 4B). The change in the surface morphology was most pronounced in the ficin-treated group (concentration: 0.1%) wherein the accumulated bulk material was thinner or disappeared (Figure 4C).

Figure 3
Scanning electron micrographs of bovine enamel slices (A) before staining, and (B) after staining. Scale bar: 1.0 µm.

Figure 4
Scanning electron micrographs of stained bovine enamel slices treated by different whitening agents. (A) no intervention; (B) 0.2% carbamide peroxide intervention; (C) 2% sodium tripolyphosphate intervention; (D) 0.1% ficin intervention. Scale bar: 1.0 µm.

3.4 Degree of enamel damage after treatment with 0.1% ficin

The enamel surface morphology after 37% phosphoric acid etching (Figure 5D) was used as the positive control group of this experiment. From Figure 5D, it can be seen that the surface of the glaze column became rough and the outline of the glaze column became clear. However, the enamel surface of bovine teeth without intervention and cleaning (Figure 5A) was smooth, without an erosion mark, and the contour of the enamel column was not clear. Compared with the enamel surface morphology (Figure 5B) after 10 min of alcohol cleaning, the enamel surface morphology after 0.1% ficin intervention (Figure 5C) had no obvious change; only a cavity appeared in the enamel sheath.

Figure 5
Scanning electron micrographs of bovine enamel slices before and after treatment with 0.1% ficin. (A) before staining; (B) after ultrasonic cleaning with alcohol; (C) after treatment by 0.1% ficin; (D) after treatment with 37% phosphoric acid (positive control group). Scale bar: 20.0 µm.

4 Discussion

This study first determined that ficin had a substantially decolourisation effect in aqueous solution compared with CP and STPP at low concentrations. In addition, to the best of our knowledge, this is the first study to evaluate the effect of concentration on the decolourisation properties of ficin.

The staining model in our experiment was based on a model established by previous studies, with some modifications (Pontefract et al., 2004; Claydon et al., 2001; Gadhia et al., 2006; Lath et al., 2006). The staining procedure through cyclying soaked the substance in human saliva (pooled from three volunteers) and staining solution for minutes, then rinsing in deionized water for minutes after the each time soaking. However, the termination of stain cycle was different in based on the time of staining and different typy of staining solution. Because physiological exogenous colouring takes place over a longer time frame, chlorhexidine, phosphoric acid, and other substances were introduced in this previous modelling procedure to shorten the staining time. To better simulate physiological exogenous colouring, this step, which often leads to extended procedure time, was omitted in our modelling procedure. Therefore, in our experiment, we developed an automatic circulation device to reduce workload. The assumed treatment time of 30 min was based on studies that determined the optimal reaction time for 0.0125-0.05% cystine proteases to be 5-30 min at the molecular level (Yao et al., 2013; Yao et al., 2012). Similarly, a food-based study also confirmed that ficin had a good hydrolytic effect at 30 min of treatment (Hu et al., 2020). In this experiment, the sample size of each treatment group was smaller than the sample size estimated in previous studies (Sheen et al., 2001; Griffiths et al., 2008; Kalyana et al., 2011). It is of importance to note that the total sample size of each substance containing five treatment groups was 30, and our results showed a good dose-effectiveness relationship.

CP and STPP are effective chemical whitening ingredients in whitening toothpaste at low concentrations (C_CP ≤ 1% and C_STPP ≤ 10%) (Frawley et al., 1952; Joiner, 2006). However, their concentrations are usually diluted 2-5 times when brushing teeth, which is the underlying reason for selecting the concentrations of CP and STPP used in this experiment (Shellis et al., 2005; Matis et al., 2002). The decolourisation effect of CP and STPP was remarkably only at high concentrations in our experiment. However, these high concentrations exceed the safety concentration for the human body (CCP < 0.75% and CSTPP < 5%), it was demonstrated by recent experimental researches (Chang et al., 2013; Arumugam et al., 2014; Zhao et al., 2019; Araya-Quesada et al., 2020). Moreover, a brushing experiment confirmed that long-term application of STPP at concentrations higher than 2.5% can cause a decrease in enamel gloss and even lead to enamel demineralisation (Milleman et al., 2017).

Due to safety concerns, the concentration of hydrogen peroxide in cosmetic toothpastes is limited to a maximum of 0.1% in the European Union (Fearon, 2007). Therefore, we believe that the decolourisation effect of CP and STPP, which were introduced into over-the-counter products such as whitening toothpaste, is not effective at low concentrations. This result also confirms the concerns of many scholars that low concentrations of CP and STPP in toothpaste may not be potent enough for effective decolourisation. These concerns are based on the inherent instability of CP and STPP in an aqueous formulation, on short contact time during toothbrushing, and the additional dilution due to salivary flow (Epple et al., 2019; Hadidi et al., 2021).

In the present study, ficin showed good decolorising ability at low concentrations (C _ficin = 0.05%) (Table 2). The main changes in b* and L* indicate that the colour became bluer and brighter. The reason may be that the salivary protein in the salivary protein/tea pigment complex was degraded, and the characteristics (absorption maximum and extinction coefficient) of their chromophores were changed, leading to less light absorption in the visible range (Epple et al., 2019). Because the yellow tea polyphenols in black tea absorbed weakly in the red/green hue (Menet et al., 2004; Mao et al., 2021), the changes in a* were not significant (P > 0.05). When the concentration was ≥ 0.1%, the decolourisation effect did not continue to increase significantly (P > 0.05) (Table 2). This may be because the salivary protein/tea pigment complex was completely hydrolysed by ficin, resulting in the disappearance of enzyme binding sites on the sample surface (Hu et al., 2020; Li et al., 2020; Maqsood et al., 2018). In contrast to the SEM images (as shown in Figure 4D), we also found that the cloud lumps became smaller and loose, and some areas even disappeared. This can explain why the hydrolysis of salivary protein or the salivary protein/tea pigment complex by ficin requires further microscopic experiments for validation. A concentration of 0.1% was used as the critical concentration for ficin decolourisation in this experiment. This concentration was much lower than the estimated concentration of 1% ficin-based gel in a similar study (Ribeiro et al., 2020) on the effect on bovine enamel stained using coffee instead of tea. It should be emphasised that the 1% ficin gel was not diluted with an aqueous solution in their study. In addition, saliva was not involved in the staining process in their study, which cannot explain the potential effect of enzymes on salivary proteins. Some studies have reported that a ficin concentration < 0.2% has an anti-cancer effect and does not harm the soft and hard tissues of the human body (Fossum & Whitaker, 1968; Sen & Whitaker, 1973). With respect to enamel damage, a similar study has confirmed that enzyme-based gels caused less damage to the enamel surface (Ribeiro et al., 2020). Surprisingly, papain- and ficin-containing whitening gels had protective roles and increased the hardness of the enamel surface when used with a remineralisation solution (Ribeiro et al., 2020). Consistent with this report, we also observed that the damage on the enamel surface was not prominent after treatment with 0.1% ficin. However, further studies are needed to address whether a high concentration of ficin can damage the protein composition of the enamel.

Regression analysis of dummy variables revealed that the decolorisation effect of ficin was the best. The total colour difference in 0.1% and 0.2% ficin groups, which were 2.02 ± 0.18 and 2.21 ± 0.20 respectively, reached the clinical minimum visible colour difference (ΔE_min = 2.0) (Douglas & Brewer, 1998). However, the total colour difference between the CP- and STPP-treated samples was far from the clinical minimum visible colour difference. A previous study also reported a difference between the whitening effect of similar biological proteases and their clinical applications (Demarco et al., 2009). It is possible that the external environment interferes with the biological proteases during clinical applications. When using enzymes, special emphasis must be placed on their storage conditions. Most enzymes are stable only within a selective temperature range and for a short period of time. Inactivation of enzymes may occur during the production process and during transport and storage.

We believe that the decolourisation effect of ficin on the extrinsic colouring of the enamel surface that we observed has major implications. Different concentrations of ficin had certain decolorization effect on exogenous tooth staining caused by tea, and the decolorization effect increased with the increase of concentration. When the concentration increased to 0.1%, the decolorization effect was visible to the naked eye. The current research shows that some natural compounds such as ficin, papain and bromelain are widely used at dental bleaching due to their anti-infammatory, antithrombotic and immunomodulatory effects (Mazilu et al., 2021). However, whether ficin can be introduced into whitening products requires further microscopic assessments and clinical trials. Further studies can provide insights into the synergistic or antagonistic effects of ficin when used in combination with other chemical components on the overall decolourisation effects of toothpaste.

5 Conclusion

In conclusion, this study have scientific and rationale study objectives and designs. Even the hydrolysis of salivary protein by ficin has been confirmed, the only in vitro study on the whitening effect of ficin ignores saliva in the modeling process. Therefore, the modeling method of cyclic staining with saliva is more suitable to study the whitening effect of ficin.We have found that under the safe concentrations, the whitening effect of ficin is better than that of STTP and CP, the common chemical whitening components in toothpaste. This study indicates the potential application of ficin for at-home or non-invasive whitening therapy and suggests that ficin are worthy of further investigation for use in oral healthcare.

Acknowledgements

The authors thank Yunwei Shi for her help during the preparation of this manuscript. The authors are grateful for the financial support from the Natural Science Foundation of Fujian Province (grant no.: 2013D010) and Nantong Science and Technology Bureau (MS12021098).

• Practical Applications: In the present study, we used low concentrations of CP and STPP, which are commonly used in whitening toothpaste, as controls to further evaluate the whitening effect of ficin. We have found that under the safe concentrations, the whitening effect of ficin is better than that of STTP and CP, the common chemical whitening components in toothpaste. This study indicates the potential application of ficin for at-home or non-invasive whitening therapy and suggests that ficin are worthy of further investigation for use in oral healthcare.
• #Runsheng Pei and Cong Xiao are joint first authors

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Publication Dates

• Publication in this collection
  13 May 2022
• Date of issue
  2022

History

• Received
  02 Feb 2022
• Accepted
  25 Mar 2022