Chitosan as protection against dental erosion

Dental erosion is the demineralization of the hard tooth substance caused by acids. Particularly in industrialized countries this is an increasing problem due to changes in drinking and eating habits in recent decades. Additionally, the teeth surface is eroded by mechanical interaction like brushing. To substantially reharden demineralized enamel, the development of appropriate prophylaxis and therapy is important. HMC presents two studies that tested toothpaste and mouth rinses containing chitosan.

The goal in prophylaxis/therapy is to reduce acid exposure for reduction of demineralization, decrease surface hardness and susceptibility to mechanical wear. In addition, the solubility of tooth tissue should be reduced if acid exposure cannot be eliminated. It is well known that the use of fluorides reduces the demineralization of enamel.

Viscosity of chitosan impacts the efficacy of F/Sn containing toothpastes against erosive/abrasive wear in enamel

Pini NIP, Lima DANL, Luka B, Ganss C, Schlueter N. J Dent. 2020 Jan; 92:103247. doi: 10.1016/j.jdent.2019.103247. Epub 2019 Nov 16. PMID: 31743693.

The primary mode of action of F/Sn preparations is the retention of tin ions (Sn²⁺) and the incorporation of tin into the enamel. For mouth rinses containing fluorine and tin, it has already been shown in situ that tissue loss can be reduced by up to 70%. When used as a toothpaste, there is the problem that toothbrushing causes loss of enamel. Chitosan has promising properties to improve the effectiveness of F/Sn toothpaste, as the biopolymer forms a protective layer on the tooth surface. The aim of the study was to investigate whether chitosan increases the anti-erosive efficacy of fluorine/tin-containing toothpastes and the influence of viscosity. For this purpose, 192 teeth from human donors were randomly divided into 2x 6 groups with 16 samples each. Chitosans by Heppe Medical Chitosan with a deacetylation degree of 80% were used for the study. The stated viscosities (mPas) describe the viscosity groups (more information see specifications).

Treatment groups:

1. F/Sn (500 ppm F^-, 800 ppm Sn²⁺) -toothpaste with 0.5% Chitosan (Viscosity 50)
2. F/Sn-toothpaste with 0.5% Chitosan (Viscosity 500)
3. F/Sn-toothpaste with 0.5% Chitosan (Viscosity 1000)
4. F/Sn-toothpaste with 0.5% Chitosan (Viscosity 2000)
5. negative control (toothpaste without F/Sn/Chitosan)
6. positive control (F/Sn-toothpaste without chitosan)

The study was conducted in two experimental branches (E1/E2). The enamel samples were cyclic demineralized (10 days, 6x 2 min per day with 0.5% citric acid). Half of the group (E1) was exposed to toothpaste (2x 2 min) and the second half (E2) was additionally brushed with a machine (2x 15s per day). The loss of tissue was determined and elemental analysis of the sample surface and the toothpastes particulate fraction was performed. In addition, SEM was used to analyze the sample surface.

Results

• Highest tissue loss in the negative controls with 4.96 µm ± 1.55 (E1) and 12.76 µm ± 2.45 (E2)
• E1: toothpaste with active ingredients
  
  • reduction of tissue loss
  • formation of distinct precipitates
  • formation of significantly thicker layers with chitosan 80/500
• E2: toothpaste with active ingredients
  
  • reduction of tissue loss compared to negative control
  • tissue loss due to tooth brushing
  • higher efficacy compared to positive control with Chitosan 80/1000

Conclusion: The viscosity of the chitosan used has an influence on the efficacy of F/Sn toothpaste. Chitosan with a viscosity around 1000 mPas showed the best protective effect with higher tin retention on surfaces and lower absorption of tin by abrasives.

Source: https://www.sciencedirect.com/science/article/abs/pii/S0300571219302520

Previous studies have already investigated the daily use of mouth rinses with titanium tetrafluoride (TiF₄) and sodium fluoride (NaF) by patients at high risk of enamel erosion. The effect of TiF4 is based on the reaction of titanium with phosphate from apatite, forming a glaze-like acid-resistant layer. A previous in situ study on damaged enamel showed similar effect for a TiF₄/NaF solution compared to a commercial solution containing SnCl₂/NaF/AmF. A possible way to improve the oral rinse could be to increase the viscosity with chitosan. A protective effect against tooth erosion has already been shown for the addition of chitosan to zinc/fluoride toothpaste.

Effect of titanium tetrafluoride/sodium fluoride solutions containing chitosan at different viscosities on the protection of enamel erosion in vitro

Beatriz Martines de Souza, Larissa Rodrigues Pereira Santi, Samira Helena João-Souza, Thiago Saads Carvalho, Ana Carolina Magalhães, Archives of Oral Biology, Volume 120, 2020

The authors of the study investigated the protective effect of solutions with TiF₄/NaF and chitosan against enamel erosion in vitro compared to conventional SnCl₂/NaF/AmF solutions. It was hypothesized that the addition of chitosan would increase the protective effect of TiF₄/NaF solutions. Chitosan 75/500 (deacetylation degree/viscosity) and Chitosan 75/2000 from Heppe Medical Chitosan GmbH were used for the study.

In the study, bovine enamel samples (in vitro) were treated with the following solutions (15 samples per group):

1. commercial solution with SnCl₂/NaF/AmF (500 ppm F^-, positive control)
2. NaF/TiF₄ (490 ppm F^-)
3. solution (2) + 0.5 % chitosan (viscosity group 500)
4. solution (2) + 0.5 % chitosan (viscosity group 2000)
5. water (negative control)
6. 0.5 % chitosan (viscosity 500 mPas)
7. 0.5 % chitosan (viscosity 2000 mPas)

The bovine enamel samples were subjected to pH cycles for seven days. They were treated with 0.1% citric acid (pH 2.5) four times a day for 90s. The rest of the time and overnight, the samples were exposed to artificial saliva (pH 6.8). After the last citric acid treatment, the samples were treated daily for 30s with the above solutions. Changes in surface reflectance intensity (%rSRI) were measured after day 1. The erosive enamel loss was quantified by contact profilometer after 7 days.

Results

• TiF₄/NaF with 0.5% chitosan (500 mPas) was able to reduce early erosive demineralization compared to the negative control
• lowest mean enamel loss when treated with commercial solution (median: 0.72 µm)
• significantly reduced enamel loss for NaF/TiF₄ solution with chitosan (solution 3: 1.24 µm and solution 4: 1.28 µm) compared to control (1.70 µm)

Conclusion: The TiF₄/NaF solution with higher viscosity chitosan (Chitosan 75/2000) has a comparable protective effect against enamel erosion as the commercial control solution. Further studies should investigate the results under more complex conditions using human saliva and simulating tooth brushing, as the protective layer produced by chitosan becomes firmer and stronger in the presence of salivary proteins.

Source: http://www.sciencedirect.com/science/article/pii/S0003996920302995