Abstract
Introduction
Pastes for professional mechanical tooth cleaning (PMTC) that contain abrasive ingredients can damage the surface of a tooth. A PMTC paste containing silica was recently developed as an adsorption material.
Materials and methods
We assessed the effectiveness with regard to on stain deposition of a novel PMTC paste containing high-performance silica (HPS) comprising porous ultra-fine particles. We also compared the pigment adsorption capability of HPS with that of ordinary silica.
Results
When PMTC solutions were added to hydrated lime stained with coffee or rooibos tea, a PMTC solution containing HPS was more effective with regard to stain removal than other PMTC solutions without HPS. In addition, stain-preventive effect of the PMTC paste containing HPS was also higher than that of the PMTC paste without HPS. When HPS and ordinary silica were immersed in food-coloring additives, HPS was more adasorptive than ordinary silica, especially with regard to high-molecular-weight pigments. Furthermore, HPS was significantly more adsorptive than ordinary silica 5 min after exposure to coffee and 24 h after exposure to rooibos tea ( P < 0.05).
Conclusion
Our results suggest that PMTC paste containing HPS effectively adsorbs pigments and can remove staining and prevent stain deposition without polishing teeth.
1
Introduction
Professional mechanical tooth cleaning (PMTC) is a process by which dental professionals such as dentists and dental hygienists mechanically and chemically remove deposits on the tooth surface using a combination of special instruments and paste [ ]. The main purpose of PMTC is to remove dental plaque, but PMTC is also expected to improve tooth surface aesthetics by removing stains [ , ]. PMTC paste containing abrasive components can remove extrinsic stains, which can lead to loss of tooth structure by smoothing the tooth surfaces [ ]. In addition, the extrinsic staining of primary teeth is often a cause of concern to parents and there have been reports that such staining can adversely affect the social interactions of preschool children [ , ]. Therefore, PMTC paste which has a high effect of stain deposition or highly safe for tooth is needed in clinical pediatric dentistry.
Silica is abundant in the Earth’s crust. Natural silica adopts crystalline forms such as quartz, tridymite, and cristobalite [ ]. However, natural crystalline silica can cause health problems such as pneumoconiosis [ ]. In contrast, synthetic silica, which has an amorphous structure and is prepared by chemically reacting natural silica, is very safe [ ]. Synthetic silica can be used in applications that are ingested or touched by the human body, such as pharmaceuticals, cosmetics, and foods [ ]. Silica is used for various purposes in medicine, including as a sustained release agent, excipient, active substance, and lubricant [ ]. However, its most significant feature is adsorption capability [ ]. Silica has several structural properties that can be adjusted. These properties include shape, particle size, surface area, pore diameter, and pore volume. Differences in these properties lead to differences in effects and applications [ ].
The importance of tooth cleaning to maintain oral health has led to a continuous search for innovative dental care solutions. With silica-containing toothpaste, it is possible to remove stains by exploiting the adsorption capability of the silica without damaging the teeth [ ]. Recent technological advances have enabled the synthesis of silica with porous ultra-fine particles [ , ], but there has been no investigation of its effectiveness in tooth stain deposition. In the present study, we evaluated the ability of a novel PMTC paste containing porous and ultrafine high-performance silica (HPS) to remove or prevent stain deposition. We also compared the pigment adsorption capability of HPS with that of ordinary silica.
2
Material and methods
2.1
Materials
Three one-step type PMTC pastes were used in the present study: a paste containing HPS (Paste HPS; Weltec, Osaka, Japan), and two commercially available pastes without silica: Paste A and Paste B. The characteristics and scanning electron microscopy (SEM) images of each PMTC paste are presented in Table 1 and Fig. 1 . Each PMTC paste was used after adding distilled water to obtain a concentration of 0.5 g/mL and distilled water was used as control. The HPS with porous and ultra-fine particles included in Paste HPS, and the ordinary silica used as the control were provided by SMOCA DENTIFRICE (Osaka, Japan). The SEM images of each silica are presented in Fig. 2 . The characteristics of each food coloring are presented in Table 2 . Commercially available red, blue, green, and yellow food dyes were used after adding distilled water to produce solutions, each with a concentration of 0.2 mg/mL. We also prepared a red dye with a high molecular weight.
| PMTC paste | Main component |
|---|---|
| Paste HPS |
|
| Paste A |
|
| Paste B |
|
| food coloring | Main component; content |
|---|---|
| Blue |
|
| Green |
|
| Yellow |
|
| Red |
|
| Red with high-molecular-weight |
|
2.2
Stain removal using the PMTC paste
The experimental flow for stain removal using the PMTC paste is shown in Fig. 3 A. Hydrated lime (FUJIFILM Wako Pure Chemical Corporation, Osaka, Japan) was stained with coffee or rooibos tea for 48 h. After adding 200 μL of each PMTC paste containing solution to the hydrated lime, it was allowed to stand at room temperature for various period. The supernatant was removed, and after washing with 1 mL of distilled water, 1 mL of distilled water was added. The solution (300 mL) was transferred to a 96-well plate, and an image was taken from the bottom. The image was scanned, and the red, green, blue (RGB) value was determined by Image J software (NIH, Bethesda, MD, USA). The RGB value was calculated using a brightness formula: RGB value = 0.299R + 0.587G + 0.114B [ ]. The color change rate was calculated from the numerical change before and after adding each PMTC solution.
2.3
Stain prevention using the PMTC paste
The experimental flow for stain prevention using the PMTC paste is shown in Fig. 3 B. Two hundred μL of each PMTC paste containing solution was added to hydrated lime and allowed to stand at room temperature for various periods (5 min, 30 min, 3 h, or 24 h). The supernatant was removed, and hydrated lime was stained with coffee or rooibos tea for 48 h after washing with 1 mL of distilled water. The supernatant was removed, and after washing with 1 mL of distilled water, 1 mL of distilled water was added. The solution (300 mL) was then transferred to a 96-well plate, and the color change of the solution before and after the experiment was evaluated by assigning RGB value using Image J software.
2.4
Adsorption of the pigments in food colorings by silica
The HPS or ordinary silica (100 mg) was added to 1 mL of food coloring solution. After 24 h, the supernatant of each solution was removed, washed with 1 mL of distilled water, and 1 mL of distilled water was added. The solution (300 mL) was then transferred to a 96-well plate, and the color change of the solution before and after the experiment was evaluated by assigning RGB value using Image J software.
2.5
Adsorption of the pigments in beverages by silica
The HPS or ordinary silica (100 mg) was added to 1 mL of coffee or rooibos tea. The color change of the silica was evaluated over various periods (30 min, 3 h, or 24 h). The supernatant of each solution was removed and washed with 1 mL of distilled water, and 1 mL of distilled water was added. The solution (300 mL) was transferred to a 96-well plate, and the color was evaluated by assigning RGB value using Image J software.
2.6
Statistical analysis
Statistical analyses were conducted using GraphPad Prism 9 software (GraphPad Software Inc., La Jolla, CA, USA). All assays were carried out three times, and the results are presented as the means ± standard deviations. Comparisons between two groups was performed using the Student’s t -test. Differences between multiple groups for each assay were determined by analysis of variance. The Bonferroni correction was used for post hoc analysis. The results were considered significantly different at P < 0.05.
3
Results
3.1
Stain removal capability of the PMTC paste
The decrease in the RGB value of hydrated lime, which is a major raw material component of hydroxyapatite, after staining with coffee and rooibos tea for 48 h is shown in Fig. 4 A. Three one-step PMTC pastes were prepared: a paste containing HPS and two pastes without silica ( Table 1 ). Suspensions comprising each PMTC paste in distilled water (0.5 g/mL) were added to hydrated lime that had been dyed with coffee or rooibos tea for 48 h. The resulting color change rates were evaluated using RGB value. Of the four pastes tested, the one containing HPS had the highest color change rate over 5 min, which implied the highest stain removal effect, and there were significant differences compared with the control ( P < 0.05) ( Fig. 4 B). The color change rate of the paste containing HPS was also highest when the various pastes were tested for three other durations ( Fig. 4 C–E); at 3 h, there were significant differences between the paste with HPS and the other two PMTC pastes without silica ( P < 0.05).
