In situ clinical evaluation of a stabilised, stannous fluoride dentifrice

Ultrastructural investigation of the effect of toothpastes containing different remineralizing agents on demineralized enamel

OBJECTIVE

The present study aimed to evaluate the effect of remineralizing agents on demineralized enamel intended for use as fluoride substitutes or supplements for oral hygiene applications.

METHODOLOGY

Enamel samples were obtained from 30 bovine teeth. The enamel blocks were stored in 20 mL of demineralization solution for 72 h. They were then brushed with the following toothpaste for the remineralization protocol: NaF, NaF/SnF2 combination, NovaMin, or nano-hydroxyapatite. SEM/EDX examinations and microhardness measurements of the samples were performed to investigate the remineralization efficacy of the studied toothpaste. One-way analysis of variance (ANOVA) with post hoc Tukey's HSD test was used to analyze the change in microhardness values in different remineralization protocols (p < 0.05).

RESULTS

Differences in the mean remineralization (%RP) and hardness recovery (%HR) were determined between the groups (p < 0.05). Groups 1 and 4 showed significant differences in %RP (p < 0.05). In the SEM/EDX examinations, the samples treated with n-HAp showed an accumulation of crystal deposits on the enamel surface, although at a lower density than those treated with NaF and NaF/SnF2 combination.

CONCLUSION

The remineralization strategy in toothpaste plays an important role in enamel remineralization. NovaMin-containing toothpaste showed positive effects on the enamel surface with better Ca/P ratio. Toothpastes containing n-HAp triggered less change in the increase of microhardness values compared to other toothpastes. The use of SnF2 in toothpaste in combination with NaF significantly increased the binding of fluoride to demineralized enamel compared to toothpaste containing NaF alone.

Recent advancements of fluorescent tin(IV) complexes in biomedical molecular imaging

In the last few years, tin(IV) complexes have emerged as very attractive candidates in the field of molecular imaging due to their unique photophysical properties. Despite the few reviews published to date covering the chemistry of organotin and tin complexes and their cytotoxic potential, there are no reviews devoted to their live cell imaging properties. Therefore, this feature article summarizes the discussion of the fundamental photophysical properties of fluorescent tin metal complexes focusing on their recent advances in "biomedical molecular imaging". A debate on the design of tin complexes as cellular imaging agents relating to their chemical, electronic and photophysical properties is enclosed. This paper also discusses the imaging applications of tin complexes in cells, tissues, and organisms via confocal and multiphoton imaging for sensing mechanisms in cellular media, bioimaging, and therapeutic labeling. In addition, it explores and explains the current challenges and prospects associated with these tin complexes as emerging luminescent cellular agents for potential clinical use.

Morphological and Elemental Evaluation of Investigative Mouthwashes to Repair Acid-Eroded Tooth Surface

Purpose

Erosive tooth wear (ETW) is characterized by subsurface demineralization and tooth substance loss with crater formation. Remineralization of subsurface demineralization has previously been demonstrated; however, repair of the eroded surface is still under investigation. This study investigated the effectiveness of mouthwashes containing hydrolyzed wheat protein (HWP) in repairing ETW through promotion of organized crystal growth.

Methods

Enamel Erosion was created on 210 enamel blocks by 10-minute demineralization in 1% Citric Acid (pH 3.5). Then, blocks were randomly assigned to seven groups (30/group); (A) 0.2% HWP, B) 1% HWP, (C) 2% HWP, (D) 1% HWP + 0.05% NaF, (E) Listerine™ mouthwash, (F) 0.02% NaF Crest™ Pro-health mouthwash and (G) artificial saliva (AS) only. Groups were subjected to daily pH-cycling consisting of one 5-minute erosive challenge with citric acid, three 1-minute mouthwash treatment periods, and then storage in AS for the rest of the time for 28 days. Treatment effects were assessed using SEM-EDX. Statistical analysis was by ANOVA and Tukey's multiple comparison.

Results

In groups exposed to HWP-containing mouthwashes, there was growth of fiber-like crystals that increased in packing density in a dose-dependent manner (0.2%, 1%, 2%) on the eroded enamel surfaces, with increased calcium and phosphate contents on the treated surfaces. The non-HWP-containing groups had the eroded surfaces covered by structureless deposit layer firmly attached to the surface.

Conclusion

Treating eroded enamel surface with HWP-containing mouthwash resulted in repair of the damaged tissue by formation of a protective layer of crystal deposits within and on the eroded enamel tissue.

Topical Agents for Nonrestorative Management of Dental Erosion: A Narrative Review

A nonrestorative approach to the management of dental erosion is the foremost option: controlling dental erosion. The objectives of this study are to provide an overview and to summarise the effects and properties of topical anti-erosive agents as a nonrestorative treatment of dental erosion. A literature search was conducted on five databases of peer-reviewed literature—Cochrane Library, EMBASE, PubMed, Scopus and Web of Science—to recruit articles published between 1 January 2000 and 31 December 2021. The literature search identified 812 studies; 95 studies were included. Topical anti-erosive agents can be broadly categorised as fluorides, calcium phosphate-based agents, organic compounds and other anti-erosive agents. In the presence of saliva, fluorides promote the formation of fluorapatite on teeth through remineralisation. Calcium phosphate-based agents supply the necessary minerals that are lost due to the acid challenge of erosion. Some organic compounds and other anti-erosive agents prevent or control dental erosion by forming a protective layer on the tooth surface, by modifying salivary pellicle or by inhibiting the proteolytic activity of dentine collagenases. Topical anti-erosive agents are promising in managing dental erosion. However, current evidence shows inconsistent or limited results for supporting the use of these agents in clinical settings.

Easy and rapid chemosensing method for the identification of accumulated tin in algae: a strategy to protect a marine eco-system

A simple and potent chemosensor AFL has been successfully developed to recognize Sn2+ selectively in marine algae or, more precisely, seaweed, as they are at huge risk from marine contamination.

Mitochondria-targeted dual-channel colorimetric and fluorescence chemosensor for detection of Sn2+ ions in aqueous solution based on aggregation-induced emission and its bioimaging applications

Several fluorescence and colorimetric chemosensory for Sn²⁺ detection in an aqueous media have been reported, but applications remain limited for discriminative Sn²⁺ detection in live human cells and zebrafish larvae. Herein, a mitochondria-targeted Sn²⁺ "turn-on" colorimetric and fluorescence chemosensor, 2CTA, with an aggregation-induced emission (AIE) response was developed. The sensing of Sn²⁺ was enabled by a reduction-enabled binding pathway, with the conversion of -C˭O groups to -C-OH groups at the naphthoquinone moiety. The color changed from light maroon to milky white in a buffered aqueous solution. The chemosensor 2CTA possessed the excellent characteristics of good water solubility, fast response (less than 10 s), and high sensitivity (79 nM) and selectivity for Sn²⁺ over other metal ions, amino acids, and peptides. The proposed binding mechanism was experimentally verified by means of FT-IR and NMR studies. The chemosensor 2CTA was successfully employed to recognize Sn²⁺ in live human cells and in zebrafish larvae. In addition, a colocalization study proved that the chemosensor had the ability to target mitochondria and overlapped almost completely with MitoTracker Red. Furthermore, a bioimaging study of live cells demonstrated the discriminative detection of Sn²⁺ in human cancer cells and the practical applications of 2CTA in biological systems.

Characterisation of mechanical and surface properties of novel biomimetic interpenetrating alumina-polycarbonate composite materials

OBJECTIVE

To determine the mechanical and surface characteristics of two novel biomimetic interpenetrating phase alumina-polycarbonate (Al₂O₃-PC) composite materials, comprising aligned honeycomb-like porous ceramic preforms infiltrated with polycarbonate polymer.

METHOD

Two composite materials were produced and characterised. Each comprised a porous structure with a ceramic-rich (polymer-poor) top layer, graduated through to a more porous ceramic-poor (polymer-rich) bottom layer. In addition, pure polycarbonate and dense alumina specimens were subjected to the same characterisation namely: density, compression, three-point bend, hardness, surface loss and surface roughness testing. Scanning electron microscopy and micro computerised tomography were employed for structural examination.

RESULTS

Three-dimensional aligned honeycomb-like ceramic structures were produced and full interpenetration of the polymer phase was observed using MicroCT. Depending on the ceramic volume in the initial aqueous ceramic suspension, the density of the final interpenetrating composites ranged from 2.64 to 3.01g/cm³, compressive strength ranged from 192.43 to 274.91MPa, flexural strength from 105.54 to 148.47MPa, fracture toughness from 2.17 to 3.11MPa.m^½, hardness from 0.82 to 1.52GPa, surface loss from 0.71 to 1.40μm and surface roughness, following tooth brushing, from 0.70 to 0.99μm. Composite specimens showed characteristic properties part way between enamel and polycarbonate.

SIGNIFICANCE

There was a correlation between the initial solid ceramic loading in the aqueous suspension, used to produce the porous ceramic scaffolds, and the subsequent characteristic properties of the composite materials. These novel composites show potential as aesthetic orthodontic bracket materials, as their properties fit part way between those of ceramic, enamel and polycarbonate.

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.

Antierosive Effect of Topical Fluorides: A Systematic Review and Meta-Analysis of In Situ Studies

BACKGROUND

The effectiveness of the application of topical fluorides in prevention of erosive tooth wear has been an issue of controversy in the literature. The objective of this systematic review was to assess in situ studies investigating the effects of using topical fluorides on prevention of erosive tooth wear.

MATERIAL AND METHODS

Two electronic databases PubMed/MEDLINE and Cochrane Central Register of Controlled Trials were searched. Eligibility criteria included in situ-controlled studies that assessed the effect of the erosive process without additional tooth brushing. The search involved English-written articles only. A total of 684 potentially relevant titles and abstracts were found after removal of duplicates, of which 22 full-text articles were selected. Seventeen studies were included in the qualitative synthesis of which 6 studies included in the meta-analysis. The following data were obtained for each study: authors, year of publication, country, study design, periods of study, duration, blinding, interventions (type/concentration/form), tooth substrate, location of the intraoral appliance, number of samples attached to each appliance, type of acidic media used for erosive challenge, duration of erosive challenge, subjects (number/age/sex), reported side effects -if any-, measuring device, amounts of tissue loss.

RESULTS

The risk of bias of the included studies was assessed using the Cochrane Collaboration tool for assessing the risk of bias. A meta-analysis of the present study was performed using Comprehensive Meta-Analysis version 2.2.048 software.

CONCLUSION

The use of oral hygiene products containing AmF/NaF/SnCl2 or NaF may be effective in the prevention of erosive tooth wear.

Efficacy of Stannous Ions on Enamel Demineralization under Normal and Hyposalivatory Conditions: A Controlled Randomized in situ Pilot Trial

The study aim was to investigate the effect of antierosive agents on enamel under normal and hyposalivatory conditions. This double-blind crossover in situ pilot study evaluated 4 toothpastes: placebo (0 ppm F), sodium fluoride (NaF, 1,450 ppm), stannous/sodium fluoride (SnF/NaF, 1,450 ppm F-, 1,090 ppm Sn2+), and sodium fluoride, stannous chloride and chitosan (NaF/Sn/Ch, 1,450 ppm F-, 3,500 ppm Sn2+, 0.5% Ch). Twenty participants were assigned to 2 groups (n = 10 each): normal and low salivary flow. Participants wore palatal appliances holding 4 bovine enamel specimens previously eroded in vitro (D1) for 20 min prior to an in situ phase after which they were eroded again (D2). Surface microhardness was determined at baseline (BL), after D1, in situ phase and D2 to assess hardness loss (%SMH), residual hardness loss (%RHL) and erosion resistance (%RER). Additional specimens were evaluated by scanning electron microscopy after the in situ phase. ANOVA and a factorial analysis for between-subject effects were performed. Sn-based toothpastes showed the best effects (p < 0.05). Under normal flow, SnF/NaF showed higher efficacy, with a significant difference compared to NaF/Sn/Ch, NaF, and placebo (p < 0.05). Under low flow, SnF/NaF and NaF/Sn/Ch were comparable (p > 0.05); NaF and placebo were statistically similar. Comparing salivary conditions, there were significant differences for SnF/NaF for %SMH after the in situ phase (%SMHtotal)), %RHL and for all toothpastes in case of %RER. Factorial analysis revealed interactions between toothpaste and saliva flow for %SMHtotal and %RHL. Salivary flow can influence the efficacy of the antierosive toothpastes; however, Sn2+ preparations show even under low salivary flow conditions the highest efficacy in the prevention of enamel erosion.

Enamel lesions: Meta-analysis on effect of prophylactic/therapeutic agents in erosive tissue loss

This study aims to perform a meta-analysis on the effect of prophylactic/therapeutic agents in enamel tissue loss due to erosion. A paper search was done on Medline, PubMed, Embase, and Cochrane Library, and 732 papers were identified. The inclusion criteria were very restrictive in order to be able to compare different protocols and methodologies used on those studies. Sixteen papers were eligible, grouped according to the measurement method of enamel tissue loss, and a meta-analysis was done for each type of fluoride- and casein-based agent applied. Standardized mean differences were pooled across studies. There was a significant difference between all the treatment groups and their respective control groups. The highest standardized mean difference on enamel tissue loss (mean; 95% confidence interval) was obtained by stannous fluoride (4.789 μm; 1.968-7.610; P < 0.001), followed by amine fluoride (2.485 μm; 0.746-4.225; P < 0.010), and titanium tetrafluoride (1.787 μm; 1.106-2.469; P < 0.001); the lowest difference was obtained by casein phosphopeptide-amorphous calcium phosphate (0.869 μm; 0.007-1.731; P < 0.050) and sodium fluoride (0.820 μm; 0.417-1.223; P < 0.001). Stannous fluoride as a fluoride-based prophylactic/therapeutic agent allowed the lowest enamel tissue loss in erosive conditions. Standardization among future study protocols will allow better comparison regarding the prophylactic/therapeutic agent with the best clinical efficacy.

Erosion protection benefits of stabilized SnF2 dentifrice versus an arginine-sodium monofluorophosphate dentifrice: results from in vitro and in situ clinical studies

Objectives

The aim of these investigations was to assess the ability of two fluoride dentifrices to protect against the initiation and progression of dental erosion using a predictive in vitro erosion cycling model and a human in situ erosion prevention clinical trial for verification of effectiveness.

Materials and methods

A stabilized stannous fluoride (SnF₂) dentifrice (0.454 % SnF₂ + 0.077 % sodium fluoride [NaF]; total F = 1450 ppm F) [dentifrice A] and a sodium monofluorophosphate [SMFP]/arginine dentifrice (1.1 % SMFP + 1.5 % arginine; total F = 1450 ppm F) [dentifrice B] were tested in a 5-day in vitro erosion cycling model and a 10-day randomized, controlled, double-blind, two-treatment, four-period crossover in situ clinical trial. In each study, human enamel specimens were exposed to repetitive product treatments using a standardized dilution of test products followed by erosive acid challenges in a systematic fashion.

Results

Both studies demonstrated statistically significant differences between the two products, with dentifrice A providing significantly better enamel protection in each study. In vitro, dentifrice A provided a 75.8 % benefit over dentifrice B (p < 0.05, ANOVA), while after 10 days in the in situ model, dentifrice A provided 93.9 % greater protection versus dentifrice B (p < 0.0001, general linear mixed model).

Conclusion

These results support the superiority of stabilized SnF₂ dentifrices for protecting human teeth against the initiation and progression of dental erosion.

Clinical relevance

Stabilized SnF₂ dentifrices may provide more significant benefits to consumers than conventional fluoride dentifrices.

Enamel Thickness Determination by Optical Coherence Tomography: In vitro Validation

Optical coherence tomography (OCT) has been introduced in dentistry as a nondestructive diagnostic imaging tool that does not utilize ionizing radiation. This study investigated the agreement between polarization-sensitive OCT (PS-OCT), microcomputed tomography (μ-CT), and histology for enamel thickness measurements. Human enamel samples were prepared and evaluated with μ-CT and PS-OCT and then sectioned and observed via digital transversal light microscopy. For all methods, a standard transversal section (b-scan) in each sample was selected, and the enamel thickness was measured at three predetermined positions using ImageJ analysis software. The results revealed significant high agreement between all tested methods, indicating the potential of PS-OCT as a clinical tool to effectively measure enamel thickness.

Effect of Fluoride-Containing Toothpastes on Enamel Demineralization and Streptococcus mutans Biofilm Architecture

This study aimed to explore the effect of fluoridated toothpastes on biofilm architecture and enamel demineralization in an in vitro biofilm model. Streptococcus mutans was grown on enamel and treated with slurries of commercial toothpastes, containing SnF2 or NaF. Water and chlorhexidine were used as negative and positive controls, respectively. The developed biofilms were imaged and enamel demineralization was measured. SnF2 and NaF toothpaste treatments significantly reduced enamel demineralization, but SnF2 toothpaste was more effective. Only SnF2 toothpaste and chlorhexidine treatments caused reductions on biofilm mass and thickness. In conclusion, this biofilm model was able to differentiate the effects of the SnF2 and NaF toothpastes on biofilm architecture and enamel demineralization.

The Future of Fluorides and Other Protective Agents in Erosion Prevention

The effectiveness of fluoride in caries prevention has been convincingly proven. In recent years, researchers have investigated the preventive effects of different fluoride formulations on erosive tooth wear with positive results, but their action on caries and erosion prevention must be based on different requirements, because there is no sheltered area in the erosive process as there is in the subsurface carious lesions. Thus, any protective mechanism from fluoride concerning erosion is limited to the surface or the near surface layer of enamel. However, reports on other protective agents show superior preventive results. The mechanism of action of tin-containing products is related to tin deposition onto the tooth surface, as well as the incorporation of tin into the near-surface layer of enamel. These tin-rich deposits are less susceptible to dissolution and may result in enhanced protection of the underlying tooth. Titanium tetrafluoride forms a protective layer on the tooth surface. It is believed that this layer is made up of hydrated hydrogen titanium phosphate. Products containing phosphates and/or proteins may adsorb either to the pellicle, rendering it more protective against demineralization, or directly to the dental hard tissue, probably competing with H+ at specific sites on the tooth surface. Other substances may further enhance precipitation of calcium phosphates on the enamel surface, protecting it from additional acid impacts. Hence, the future of fluoride alone in erosion prevention looks grim, but the combination of fluoride with protective agents, such as polyvalent metal ions and some polymers, has much brighter prospects.

Protective effects of SnF2 - Part I. Mineral solubilisation studies on powdered apatite

PURPOSE

To compare the ability of two active ingredients - sodium fluoride (NaF) and stannous fluoride (SnF2 ) - to inhibit hydroxyapatite (HAP) dissolution in buffered acidic media.

METHODS

Two in vitro studies were conducted. HAP powder, which is representative of tooth mineral, was pretreated with: test solutions of NaF or SnF2 , 10 g solution per 300 mg HAP powder (Study 1); or NaF or SnF2 dentifrice slurry supernatants, 20 g supernate per 200 mg HAP powder for 1 minute followed by three washes with water, then dried (Study 2). About 50 mg of pretreated HAP was exposed to 25 ml of acid dissolution media adjusted to and maintained at pH 4.5 in a Metrohn Titrino reaction cell. Exposure of HAP to the media results in dissolution and release of hydroxide ion, increasing the pH of the solution. The increase in pH is compensated for by automatic additions of acid to maintain the original pH (4.5) of the reaction cell. Total volume of titrant added after 30 minutes was used to calculate the percentage reduction in dissolution versus non-treated HAP control.

RESULTS

Both F sources provided protection against acid dissolution; however, in each study, SnF2 -treated HAP was significantly more acid-resistant than the NaF treated mineral. In study 1, at 280 ppm F, representing concentrations of F found in the mouth after in vivo dentifrice use, the reduction in HAP dissolution was 47.7% for NaF and 75.7% for the SnF2 -treated apatite (extrapolated). In study 2, the reduction in HAP dissolution was 61.3% for NaF and 92.8% for SnF2 -treated samples. Differences in percentage reduction were statistically significant (Paired-t test).

CONCLUSIONS

Results of these studies demonstrate that both of the fluoride sources tested enhance the acid resistance of tooth mineral and that resistance is significantly greater after treatment with SnF2 compared with treatment of tooth mineral with NaF.

Protective effects of SnF2 - Part II. Deposition and retention on pellicle-coated enamel

Deposition of an acid-resistant barrier onto enamel represents a potentially superior means for delivering protection against dietary, erosive acid challenges.

PURPOSE

The purpose of this study was to demonstrate the ability of a stabilised stannous fluoride (SnF2 ) dentifrice to: (1) deposit a SnF2 barrier layer onto pellicle-coated enamel surfaces; (2) increase the intensity of the barrier layer over time; and (3) be retained on the enamel surface for hours after product use.

METHODS

Squares of human enamel were exposed to pooled saliva for 1 hour (pellicle formation) and separated into six sets. Set 1 was treated with the supernatant of a 1:3 slurry of the test dentifrice (Crest(®) Pro-Health(®) : water for 2 minutes), then rinsed. Set 2 was treated in the same manner and then placed into saliva (6 hours). Set 3 was cycled through seven repeated treatments. Set 4 was treated for seven cycles and then placed into saliva (6 hours). Set 5 was a water control, and set 6 was a water control that remained in saliva for 6 hours. Surface analysis of specimens was done using laser ablation Inductively Coupled Plasma Mass Spectroscopy (ICP-MS).

RESULTS

Deposition of a barrier layer was demonstrated, beginning with the initial treatment, with Sn (using isotopes (117) Sn + (120) Sn) measured on the enamel surface as the reference marker. Deposition of the barrier layer was greater after seven cycles, and the retention of this layer was highly significant (P = 0.05, anova: 6 hours).

CONCLUSIONS

This study confirms that: (1) the stabilised SnF2 dentifrice deposits a barrier layer onto the enamel surface, beginning with the first use of the product; (2) this barrier is enhanced following multiple treatments; and (3) the barrier layer is retained on the enamel surface for hours after product use.

Protective effects of SnF2 - Part III. Mechanism of barrier layer attachment

OBJECTIVE

To assess the ability of various fluoride salts to protect enamel against acid attack via a barrier mechanism.

METHODS

Extracted human enamel specimens were cleaned and rinsed, then soaked in pooled human saliva for 1 hour to initiate formation of an early pellicle. Groups of three specimens each were etched for 10 minutes in 1% citric acid (pH 2.3), treated in a 1:3 slurry of dentifrice [1,100 ppm F as stannous fluoride (SnF2 ), 1,100 ppm F as sodium fluoride (NaF), 1,000 ppm F as sodium monofluorophosphate (SMFP), or 1,400 ppm F as amine fluoride (AmF)] and saliva for 2 minutes, exposed to 2% alizarin red-S (a calcium-selective dye) and rinsed again. The relative ability of each test product to deposit a barrier layer on the enamel surface was measured by its ability to protect against attachment of the calcium-selective dye.

RESULTS

Specimens treated with the SnF2 dentifrice showed the least dye attachment, indicating a high level of surface protection. On a five-point scale, with 0 being no dye deposition (100% protection) and four being complete dye coverage (0% protection), the SnF2 -treated specimens scored an average of 0.25, with NaF scoring 3.4, SMFP scoring 3.4 and AmF scoring 3.7. Protection of the enamel surface was significantly higher for the SnF2 product than for the other products (P < 0.05), with no significant differences among the other three F salts.

CONCLUSIONS

These results demonstrate that after an aggressive acid challenge, SnF2 deposits a barrier layer onto the pellicle-coated enamel surface, and the barrier layer which attaches onto acid challenged tooth surfaces is different from any that might be provided by treatment with the other fluoride compounds tested.