Assessment of tubule occlusion properties of an experimental stannous fluoride toothpaste: A randomised clinical in situ study

Stannous Fluoride in Toothpastes: A Review of Its Clinical Effects and Likely Mechanisms of Action

This article reviews the topic of stannous fluoride as an anti-caries additive in toothpastes. It is based on a literature survey carried out using Science Direct, supplemented by information from PubMed. The keywords used were stannous fluoride, toothpaste, clinical effects, caries, hypersensitivity, gingival health, structure and aqueous solutions. The initial searches covered the period 2015-2024 and identified 57 references. Older references cited in these papers, and also papers already known to the author, were also included. The information thus obtained shows that stannous fluoride has three main effects, namely, reduction in the viability of the oral biofilm, increase in remineralisation of the hydroxyapatite tooth mineral and occlusion of dentinal tubules leading to reduced hypersensitivity. Stannous fluoride was shown to be the most effective of all the fluoride additives used in toothpastes. In much of the dental literature, this is attributed to the effects of Sn2+ ions. However, as has been shown extensively in the wider scientific literature, free Sn2+ ions do not occur in aqueous systems. Rather, the initial products of the dissolution of SnF2 is undissociated, hydrated SnF2 and SnF+ ions. These gradually exchange fluoride to form Sn(OH)2 and Sn(OH)+. Their likely mechanism of action based on their toxicity towards oral micro-organisms and their interaction with hydroxyapatite is discussed.

The Effect of Three Desensitizing Toothpastes on Dentinal Tubules Occlusion and on Dentin Hardness

There are two main methods used for dentin hypersensitivity (DH) treatment: dentinal tubule occlusion and blockage of nerve activity. Dentifrices are the most common vehicles for active ingredients used for DH treatment. The aim of this study was to evaluate the efficacy of three toothpastes on dentinal tubule occlusion, mineral acquisition, and dentin hardness. Forty human dentin disks were submerged in 40% citric acid for 30 s and then exposed to tooth brushing for 2 min twice a day for 14 days using three toothpastes: Dontodent Sensitive (group 1), Dr. Wolff's Biorepair (group 2), and Sensodyne Repair and Protect (group 3). In the control group (group 4), the samples were brushed with water. All of the samples were evaluated using scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and Vickers dentin hardness determination. On SEM images, the degree of dentinal tubule occlusion was assessed using a five-grade scale. The mean score values in groups 1-4 were 3.60 ± 0.69, 2.20 ± 0.91, 2.30 ± 1.16, and 5.00 ± 0.00, significantly higher in study groups when compared to the control group (Kruskal Wallis test p < 0.05). EDX evaluation showed significantly higher calcium and phosphorus concentrations in groups 1 and 3 when compared to control group d. The mean values of Vickers dentin hardness numbers in groups 1-4 were 243.03 ± 10.014, 327.38 ± 56.65, 260.29 ± 37.69, and 225.83 ± 29.93, respectively. No statistically significant results were obtained when comparing the hardness mean values in groups (Kruskal-Wallis statistical test, p = 0.372 > 0.05). All three toothpastes tested demonstrated significant occlusion of dentinal tubules. Dontodent Sensitive and Sensodyne Repair and Protect toothpastes enhanced the calcium and phosphorus content of the dentin surface. None of the toothpastes increased dentin hardness as a result of mineral acquisition.

Acidic Monetite Complex Paste with Bleaching Property for In-depth Occlusion of Dentinal Tubules

Background

Dentin hypersensitivity (DH) is a common dental clinical condition presented with a short and sharp pain in response to physical and chemical stimuli. Currently no treatment regimen demonstrates long-lasting efficacy in treating DH, and unesthetic yellow tooth color is a concern to many patients with DH.

Aim

To develop a bi-functional material which can occlude dentinal tubules in-depth and remineralize dentin for long-lasting protection of the dentin–pulp complex from stimuli and bleach the tooth at the same time.

Methods

A mixture containing CaO, H₃PO₄, polyethylene glycol and H₂O₂ at a specific ratio was mechanically ground using a planetary ball. The mineralizing complex paste was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Dentin was exposed to the synthesized paste for 8 h and 24 h in vitro. The mineralizing property was evaluated using SEM and microhardness tests. Red tea-stained tooth slices were exposed to the synthesized paste for 8 h and 24 h in vitro. The bleaching effect was characterized by a spectrophotometer.

Results

The complex paste had very a fine texture, was injectable, and had a gel-like property with 2.6 (mass/volume) % H₂O₂ concentration. The X-ray diffraction pattern showed that the inorganic phase was mainly monetite (CaHPO₄). The mineralizing complex paste induced the growth of inorganic crystals on the dentin surface and in-depth occlusion of dentin tubules by up to 80 μm. The regenerated crystals were integrated into the dentin tissue on the dentin surface and the wall of dentinal tubules with a microhardness of up to 126 MPa (versus 137 Mpa for dentin). The paste also bleached the stained dental slices.

Conclusion

The mineralizing complex paste is a promising innovative material for efficient DH management by remineralizing dentin and in-depth occlusion of dentin tubules, as well as tooth bleaching.

Stannous Fluoride Effects on Enamel: A Systematic Review

In recent years there has been a lot of talk about toothpastes with a particular chemical compound: stannous fluoride (SnF2). Its presence is currently still highly controversial, as the latter could have negative health effects. The different companies that produce toothpastes express its dosage in ppm. The purpose of this systematic literature review is to analyze all randomized clinical trials in the literature over the last 10 years and to draw clear results on the function of stannous fluoride, for this purpose the authors performed a Mann-Whitney U Test.

MATERIALS

The first analysis of the literature produced a number greater than 800 results, subsequently applying the inclusion and exclusion criteria, and following a manual analysis of the results, 26 manuscripts have been obtained.

RESULTS

From the results analyzed in this review, it could be shown that stannous fluoride does not present important contraindications, if not those commonly reported for fluorine. A meta-analysis on enamel loss has been conducted, it shows that SnF2 products provide better results with a p < 0.05 value.

CONCLUSION

This compound could have significant effects in favor of erosion and recalcification of the enamel, on the biofilm formation, gingival inflammation, and in addition, it could be an important aid in the removal of tooth stains and halitosis.

The ability of a potassium oxalate gel strip to occlude human dentine tubules; a Novel in vitro: In situ Study

OBJECTIVES

To determine if an oxalate strip reduced fluid flow in dentine samples and whether this reduction was maintained following a 14 day intra-oral period.

METHODS

Dentine tubule fluid flow was measured by a modified Pashley cell in 40 acid-etched dentine discs 1 mm thick, diameter >10 mm, with an acquired pellicle, pre-equilibrated with Hartmann's solution and conditioned by toothbrushing, pre and post treatment (10 min) with an oxalate (3.14 %) gel strip or no treatment. One control and one test sample were exposed in-situ for 14 days to the oral environment in 20 healthy adult volunteers, and fluid flow re-measured. The appliance containing the two samples was removed for brushing with water after mealtimes when the participant brushed their teeth and for a 2 min daily soak in chlorhexidine.

RESULTS

Fluid flow rate was reduced significantly immediately following treatment with the oxalate strip compared to baseline flow rate by 58 %. Following 14 days in-situ oral environment phase, a significant further reduction in fluid flow compared to baseline was identified in both control and oxalate strip treated samples, both (p < 0.0001), but the reduction was greater in the test samples, 94 % vs 87 %, p < 0.01.

CONCLUSIONS

This novel investigation is the first to show fluid flow measurement using the Pashley model in dentine samples that have been housed in the mouth for 14 days. Treatment with an oxalate strip designed for dentine hypersensitivity alleviation reduced dentine fluid flow more than control providing evidence that the oxalate treatment withstood the oral environment over a prolonged time.

CLINICAL SIGNIFICANCE

This study demonstrated the efficacy and durability of the oxalate precipitate over a 14 day period in achieving and maintaining dentine tubule occlusion when participants had no dietary restrictions. This demonstrates the suitability of the oxalate strip for the treatment of patients suffering from dentine hypersensitivity pain.

Measurement of eroded dentine tubule patency and roughness following novel dab-on or brushing abrasion

OBJECTIVES

To investigate the effect of dab-on or brushing of stannous-fluoride SnF2 or sodium-fluoride NaF dentifrice on eroded dentine tubule patency, surface and inter-tubular dentine roughness, using Confocal-Laser-Scanning-Microscopy (CLSM), Atomic-Force-Microscopy (AFM), Energy-Dispersive-X-ray-Spectroscopy (EDX), Scanning-Electron-Microscopy (SEM) and Contact-Profilometry (CP).

METHODS

75-polished human dentine samples were prepared and eroded in agitated 6% citric acid to expose patent tubules and 'initiate' DH. Samples were randomly allocated into 5 intervention groups; artificial saliva control (1); electric tooth-brushing with NaF (2) or SnF2 (3), and dab-on application of NaF (4) or SnF2 (5). Samples underwent three cycles of intervention followed by further acid challenge. Patent tubules, likely to cause DH clinically, were measured using validated biocomputational methods with CLSM images of dentine surfaces taken baseline and post-intervention. Randomised samples (n = 15, 20 %) were investigated using AFM, EDX and SEM to study surface and sub-surface tubular occlusion. Dentine surface and inter-tubular roughness were measured using CP and AFM respectively.

RESULTS

At baseline, mean tubule patency in all samples was 216 (SD 58) with no significant inter-group differences. Post-intervention, the mean patency was 220 (40) and 208 (35) in groups 1 and 2 respectively (p ≥ 0.06), but decreased to 62 (41), 62 (21) and 63 (19) in groups 3, 4 and 5 respectively (p < 0.0001). Patency was confirmed using AFM, SEM and EDX. SnF2 interventions created greater sub-surface occlusion (p < 0.01), and increased CP surface roughness (p = 0.015). Significant negative correlation (-0.6) existed between CP surface roughness and tubule patency (p = 0.009).

CONCLUSIONS

Dab-on with NaF and SnF2 or brushing with SnF2 reduces DH in eroded dentine with ongoing acid challenges. Contacting surface roughness measures indicate risk of DH.

CLINICAL SIGNIFICANCE

Dab-on is a convenient supplementary method of dentifrice application to reduce DH; it beneficially avoids brushing post-erosion or overzealous brushing, enables re-establishment of an appropriate brushing regime post-DH and supports oral health. Significant modes of action of SnF2 in reducing DH are revealed. Finally, CP roughness measures provide indication of dentine lesions that may cause DH clinically.

Influence of desensitizing and anti-erosive toothpastes on dentine permeability: An in vitro study

OBJECTIVE

This study analyzed the effect of desensitizing and/or anti-erosive toothpastes on dentine permeability.

METHODS

One-mm dentin discs were prepared from human molars and exposed to EDTA solution (5 min, 17%). Initial dentine permeability was measured, under constant pressure. Specimens were randomly allocated into 10 groups: four anti-erosive toothpastes (calcium silicate + sodium phosphate, potassium nitrate, stannous chloride + chitosan, oligopeptide-104); four desensitizing toothpastes (arginine + calcium carbonate, calcium sodium phosphosilicate, strontium acetate, stannous fluoride); and two controls (regular fluoridated toothpaste, and human saliva). They were submitted to a 5-day erosion-abrasion cycling model. Erosion consisted of immersion in citric acid (2 min, 0.3%, natural pH ˜ 2.6, 4x/day), followed by 1 h exposure to human saliva. Specimens were brushed for 15 s (2 N, 45 strokes) with the toothpaste slurries (total exposure time of 2 min). After 5 cycles, the final dentine permeability was determined. Dentine permeability change was calculated as a percentage of the initial hydraulic conductance (%Lp). Data were analyzed with one-way ANOVA and Tukey tests (α=0.05).

RESULTS

The toothpastes calcium silicate + sodium phosphate and potassium nitrate, showed significant decrease in %Lp, with no difference between them. The regular fluoridated toothpaste also decreased the %Lp, not differing from potassium nitrate. No desensitizing toothpaste showed change in %Lp. Human saliva, oligopeptide-104 and stannous chloride + chitosan presented significant increase in %Lp, without difference between them.

CONCLUSION

Calcium silicate + sodium phosphate, potassium nitrate, and the regular fluoridated toothpaste decreased dentine permeability, whereas the desensitizing toothpastes tested did not.

CLINICAL RELEVANCE

Toothpastes had distinct impacts on dentine permeability, which may reflect a variable effect on the treatment of dentine hypersensitivity. Within the limitations of a laboratory-based study, toothpastes with an anti-erosive claim could also be effective in reducing the pain in dentine hypersensitivity.