Efficacy of the stannous ion and a biopolymer in toothpastes on enamel erosion/abrasion
Introduction
Dental erosion is a condition with a pathomechanism that differs considerably from caries. In enamel, an erosive impact leads to a layer wise loss of mineral, resulting in a total bulk loss with a partly demineralised surface on the remaining tissue.1 This is in contrast to caries, which is predominantly a subsurface phenomenon. The substantial difference as to the pathomechanism and pathohistology requires preventive and therapeutic strategies that are different from the established approaches in cariology. The first approach is the identification of the source of the acid exposure and elimination of the cause of the disease. Additional measures are strengthening the acid resistance of the tooth surface by establishing organic protective layers on the tooth surface2, 3, 4, 5 or by making the crystalline structure of dental hard tissues less soluble.6, 7, 8
For the latter, fluoride compounds with polyvalent metal cations have been shown to be particularly effective, at least in solutions.6, 7, 8 Whether this is true for toothpaste formulations and when applied under combined chemical/physical impacts is unclear. There is preliminary evidence that Sn2+-toothpastes could be promising,9, 10, 11 but the positive effect of a slurry application may be counteracted when the physical forces from toothbrushing are added.12 Overall, there is limited knowledge about the role of the Sn2+ ion in toothpastes.
The other strategy for strengthening the acid resistance of the tooth surface is using organic polymers as active ingredients; casein,2, 13 ovalbumin,2 pectin, alginate and gum arabic polymers4 as well as inorganic polymers such as pyrophosphate, tripolyphosphate and polyphosphate14 are substances under study. These substances have been used as additives in the erosive medium2, 4 or in experimental rinses,3, 13 showing reduction values of the erosive loss between 15% and nearly 100%, at least in vitro. Casein was also investigated as a component of a tooth cream in combination with amorphous calcium phosphate (CPP–ACP) with or without fluoride, with conflicting results,15, 16, 17, 18 but unlike toothpaste, this product is not indicated for daily use. A biopolymer that is widely used in industrial and biomedical applications is chitosan.19, 20 Chitosan, the collective name for polymers derived from chitin, is a cationic polysaccharide obtained by the deacetylation of chitin. It has been used in a toothpaste with no fluoride as active agent and has been shown to inhibit erosive loss in the dimension of fluoride toothpastes when compared to another fluoride free control formulation.12 Chitosan microparticles have potential as carriers of fluoride for the delivery in the oral cavity.21 Although there is some evidence that chitosan might be promising in the field of erosion,12 there is only limited information about the strength of the possible effects.
Overall, very little is known about the potential benefits of the stannous ion and chitosan in toothpaste formulations against erosion/abrasion. The aim of this paper was therefore to investigate the anti-erosion and abrasion-prevention potential of various experimental and commercial Sn2+-containing toothpastes compared with NaF formulations. In addition, one experimental Sn2+ formulation that contains chitosan as an additional active ingredient was included. To gather the first insights into the possible modes of action, the tin retention on the sample surfaces was investigated.
Section snippets
Sample preparation and solutions
Samples were prepared from previously impacted human third molars. Longitudinal slices, approximately 1 mm thick, were prepared from the smooth surfaces, ground flat and polished (diamond grinding and polishing discs, 30, 15 and 3 μm; Bühler GmbH, Düsseldorf, Germany). The resulting flattened area of approximately 3 mm × 3 mm was half covered with light curing acrylic (Technovit 7230 VLC, Kulzer-Exakt, Wehrheim, Germany). A total of 150 enamel samples were prepared (n = 15 per group), mounted on sample
Results
The data for the tissue loss and retention of Sn on the enamel following the 10 days cycling regimen are presented in Table 2.
Brushing with the placebo increased tissue loss compared with erosion by 40% and resulted in the overall highest loss values. In contrast, the positive control was most effective and reduced the tissue loss by 77% and 68% compared with the placebo and erosion only, respectively (p ≤ 0.001 each). Except for the acidic NaF toothpaste (NaF/1), all test products showed a
Discussion
There is a huge variety of experimental settings in erosion/abrasion studies,25 and a standard procedure has not yet been established. The experimental setting used here intended to mirror clinical conditions relevant to subjects with an increased risk for dental erosion (e.g., frequent consumption of soft drinks) but who are not prone to severe acid impacts. The overall experimental setting was designed to produce tissue loss values in the order of 10–15 μm in the negative control group, which
Conclusions
The Sn2+ formulations without chitosan exhibited anti-erosion/abrasion-prevention effects, but there were no differences between the investigated formulations, and the order of effects was similar to the NaF formulations. The experimental Sn2+ formulation with chitosan showed the greatest reduction of tissue loss, which was in the order of the positive control. Treatment with any of the formulations containing Sn2+ resulted in retention of tin on the enamel surface, but there was no obvious
Acknowledgements
The study was supported by GABA International, Therwil, Switzerland. We thank our technical assistant B. Meier for performing the fluoride analysis.
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