The effect of magnesium hydroxide-containing dentifrice using an extrinsic and intrinsic erosion cycling model

Recent Advances in Magnesium-Magnesium Oxide Nanoparticle Composites for Biomedical Applications

Magnesium (Mg) is considered an attractive option for orthopedic applications due to its density and elastic modulus close to the natural bone of the body, as well as biodegradability and good tensile strength. However, it faces serious challenges, including a high degradation rate and, as a result, a loss of mechanical properties during long periods of exposure to the biological environment. Also, among its other weaknesses, it can be mentioned that it does not deal with bacterial biofilms. It has been found that making composites by synergizing its various components can be an efficient way to improve its properties. Among metal oxide nanoparticles, magnesium oxide nanoparticles (MgO NPs) have distinct physicochemical and biological properties, including biocompatibility, biodegradability, high bioactivity, significant antibacterial properties, and good mechanical properties, which make it a good choice as a reinforcement in composites. However, the lack of comprehensive understanding of the effectiveness of Mg NPs as Mg matrix reinforcements in mechanical, corrosion, and biological fields is considered a challenge in their application. While introducing the role of MgO NPs in medical fields, this article summarizes the most important results of recent research on the mechanical, corrosion, and biological performance of Mg/MgO composites.

Combined use of stannous fluoride-containing mouth rinse and toothpaste prevents enamel erosion in vitro

OBJECTIVE

To compare the protective effect of commercial stannous-containing mouth rinses on enamel erosion in a simulated 5-day in vitro cycling model.

MATERIALS AND METHODS

81 human enamel specimens were embedded in resin blocks and divided into nine groups as follows; group 1: stannous fluoride (1000SnF2) toothpaste; groups 2,3, and 4 were the same as group 1 plus Elmex®, PerioMed™, and Meridol®, respectively, group 5: stannous fluoride (1450SnF2) toothpaste, groups 6, 7, and 8 were the same as group 5 plus Elmex®, PerioMed™, and Meridol®, respectively, group 9: negative control. An erosive challenge was induced with a 1 min hydrochloric acid (0.01 M, pH 2.2) treatment 3 times per day. Each cycle included immersing in the toothpaste slurry twice for two minutes and a one-minute rinse. The enamel slabs were immersed in artificial saliva between each erosive cycle and incubated overnight at 37 °C. Surface hardness loss and enamel loss were determined by Knoop surface hardness and non-contact profilometry, respectively. Finally, enamel surfaces were analyzed by scanning electron microscopy and X-ray energy dispersive spectroscopy (SEM/EDS).

RESULTS

All three mouth rinses had similar protective effects against erosion when using adjunct with 1000 SnF2 toothpaste (p > 0.05). With 1450 SnF2 toothpaste, Elmex® presented significantly lower surface hardness loss than Meridol® (p < 0.05). The combined use of Elmex® or PerioMed™ with toothpaste provided significantly better erosion protection than toothpaste alone, either 1000 or 1450 SnF2. In addition, 1000SnF2 toothpaste adjunct with mouth rinse is comparable to 1450 SnF2 toothpaste alone in preventing enamel erosion.

CONCLUSION

All three mouth rinses reduced enamel erosion. The additional use of a high concentration stannous containing mouth rinse with 1450 SnF2 toothpaste increases the protective effect against enamel erosion in vitro.

CLINICAL SIGNIFICANCE

To date, no standard protocol for preventing dental erosion is available. There are three stannous-containing mouth rinses on the market; however, no study compared their efficacy or indicated whether using adjuncts with anti-erosion toothpaste provides additional benefits. This study found that adding stannous mouth rinse to twice-daily toothpaste increases erosion protection.

Treatment for dental erosion: a systematic review of in vitro studies

Background

Dental erosion is a chemical loss of the mineralized dental tissue caused by exposure to nonbacterial acids. Different treatment protocols have been adopted with the use of fluoride compounds to promote the formation of a layer of mineral precipitation in eroded lesions.

Aim

This systematic review aimed to evaluate the main treatments for dental erosion.

Methodology

This study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and recorded in the Open Science Framework database (OSF) under DOI 10.17605/OSF.IO/XMFNZ. The searches were conducted in six electronic databases (Pubmed, Embase, Web of Science, Cochrane, Scopus, Lilacs) and two grey literature sources (Google Scholar and OpenGrey). The eligibility criteria included in vitro studies that evaluated eroded teeth under treatment with some topical agent. Risk of bias assessment and qualitative synthesis were performed using the Cochrane collaboration's tool for assessing risk of bias modified for in vitro studies.

Results

A total of 522 studies were identified, and only four studies that fulfilled our eligibility criteria were included in this review. Among these studies, three were considered to have a low risk of bias, and one to have a high risk of bias. Two studies evaluated the anti-erosion effect of fluoride toothpaste, and the other two assessed the action of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) on the surface of human teeth. Among the products analyzed, CPP-ACP was the only one that promoted a significant increase in enamel microhardness and reduced tooth wear.

Conclusion

Based on the in vitro studies included in this review, there was no anti-erosion effect after using different fluoride toothpaste. However, it should be considered that one of these studies presented a high risk of bias. On the other hand, studies with CPP-ACP showed anti-erosion efficacy when applied before or after erosive wear.

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.

Resin infiltrant protects deproteinized dentin against erosive and abrasive wear

Objectives

This study aimed to investigate the anti-erosive/abrasive effect of resin infiltration of previous deproteinized dentin.

Materials and Methods

Dentin slabs were randomly assigned to 3 groups (n = 15): Control (no deproteinization; no resin infiltrant applied), RI (no deproteinization; resin infiltrant applied), and DRI (deproteinization; resin infiltrant applied). After undergoing the assigned treatment, all slabs were subjected to an in vitro cycling model for 5 days. The specimens were immersed in citric acid (0.05 M, pH = 3.75; 60 seconds; 3 times/day) and brushed (150 strokes). Between the challenges, the specimens were exposed to a remineralizing solution (60 minutes). The morphological alterations were analyzed by mechanical profilometry (µm) and scanning electron microscopy (SEM). Data were submitted to one-way analysis of variance (ANOVA) and Tukey tests (p < 0.05).

Results

Control and RI groups presented mineral wear and did not significantly differ from each other (p = 0.063). DRI maintained a protective layer preserving the dentin (p < 0.001). After erosive/abrasive cycles, it was observed that in group RI, only 25% of the slabs partially evidenced the presence of the infiltrating, while, in the DRI group, 80% of the slabs presented the treated surface entirely covered by a resin-component layer protecting the dentin surface as observed in SEM images.

Conclusions

The removal of the organic content allows the resin infiltrant to efficiently protect the dentin surface against erosive/abrasive lesions.

Effect of Cold Atmospheric Pressure Plasma Coupled with Resin-Containing and Xylitol-Containing Fluoride Varnishes on Enamel Erosion

Purpose

Considering the suggested advantages of cold atmospheric plasma (CAP) in increasing the fluoride uptake by the enamel, this study aimed to assess enamel erosion following the application of helium CAP and two types of fluoride varnishes.

Methods

The microhardness of 70 bovine enamel specimens was measured using a Vickers hardness tester. The specimens were randomly divided into 7 groups (n = 10): control, CAP (P), resin-containing fluoride varnish (RF), CAP + resin-containing fluoride varnish (PRF), fluoride varnish (F), CAP + fluoride varnish (PF), and erosion (E). The specimens in the control and erosion groups did not receive CAP or fluoride varnish. All specimens underwent erosive challenge 4 times/day using hydrochloric acid and artificial saliva except for the control specimens that remained in distilled water during the course of the study. After 5 days of erosive challenge, microhardness was measured again, and the percentage of microhardness change was calculated. Surface roughness of two specimens in each group was assessed by atomic force microscopy (AFM). Data were analyzed using one-way ANOVA followed by Tamhane's post-hoc test.

Results

The percentage of microhardness change in all groups was significantly higher than that of the control group. All groups showed significantly lower percentage of microhardness change compared with the E group except for the P group; no significant difference was noted in microhardness change of P and E groups. Other experimental groups had no significant difference with each other. Surface roughness was the highest in PRF and the lowest in the F group.

Conclusion

CAP application had no significant effect on increasing the enamel resistance to erosion. However, enamel resistance to erosion increased significantly after fluoride varnish application alone or fluoride varnish application combined with CAP. No significant difference was noted between the two types of varnishes in this regard. CAP increased the surface roughness while fluoride varnish application alone decreased the roughness.

Effect of divalent ions on cariogenic biofilm formation

Background

Divalent cations are able to interact with exopolysaccharides (EPS) and thus are capable to modify the structure and composition of dental biofilm. At the moment, little is known about the adsorption of metals by cariogenic EPS; thus, the aim of the present study was to evaluate the effect of divalent ions (calcium, magnesium, and zinc) on the growth and biofilm formation of mutans streptococci and on the dissolution of hydroxyapatite as well as to investigate their binding to the bacterial EPS.

Results

S. mutans strains used in this study show the highest tolerance towards calcium of the ions tested. Growth parameters showed no differences to control condition for both strains up to 100 mM; revealing natural tolerance to higher concentration of calcium in the surroundings. Although excessive levels of calcium did not impair the growth parameters, it also did not have a positive effect on biofilm formation or its binding affinity to EPS. Magnesium-saturated environment proved to be counterproductive as strains were able to dissolve more Ca²⁺ from the tooth surface in the presence of magnesium, therefore releasing excessive amounts of Ca²⁺ in the environment and leading to the progression of the disease. Thus, this supports the idea of self-regulation, when more Ca²⁺ is released, more calcium is bound to the biofilm strengthening its structure and however, also less is left for remineralization. Zinc inhibited bacterial adhesion already at low concentrations and had a strong antibacterial effect on the strains as well as on calcium dissolution; leading to less biofilm and less EPS. Additionally, Zn²⁺ had almost always the lowest affinity to all EPS; thus, the unbound zinc could also still remain in the surrounding environment and keep its antimicrobial properties.

Conclusion

It is important to maintain a stable relationship between calcium, magnesium and zinc as excessive concentrations of one can easily destroy the balance between the three in cariogenic environment and lead to progression of the disease.

Chemical and mechanical resistance of novel experimental hybrid coatings on dentin permeability

This study aimed to evaluate the capacity of novel experimental hybrid coatings (HC) to reduce dentin permeability and to verify their resistance to erosive and abrasive challenges. Dentin disc specimens (1 mm thick) were treated with 0.5 M EDTA solution and randomly allocated into three experimental groups (n = 10): Control (Saliva); Concentrated Hybrid Coating (TEOS/GPTMS/Y-APS); and Diluted Hybrid Coating (1:3 ratio with distilled water). Dentin permeability was assessed by hydraulic conductance in the following experimental time periods: post-EDTA, post treatment, post erosion (5 min in 0.05 M citric acid solution, pH = 3.8), and post abrasion (toothbrushing for 3,900 cycles). Dentin permeability percent was calculated with respect the values of post-EDTA for each experimental time. The morphology of the surface of extra dentin specimens was examined by scanning electron microscopy (SEM) in the same time periods (n = 3). Permeability data were analyzed by two-way repeated measures ANOVA and Tukey tests (p < .05). Both HC presented significantly lower dentin permeability than control post treatment and post erosion (p < .05), without difference between them (p > .05). Post abrasion, there were no significant difference among groups (p > .05). Post treatment and post erosion, the HC seemed to flow into the tubules, occluding them, while the tubules in control remained opened. Post abrasion, the tubules appear to be occluded in all groups. In conclusion, the experimental hybrid coatings were capable of reducing dentin permeability after treatment. They were also able to resist to erosive and abrasive challenges, with the advantage of forming thinner and colorless films that can be potentially used to treat dentin hypersensitivity.

Fluoride dentifrice containing calcium silicate and sodium phosphate salts on dental erosion: In vitro study

OBJECTIVE

To investigate the effect of a commercial dentifrice containing fluoride, calcium silicate, and sodium phosphate and its dual phase gel serum to prevent erosive tooth wear in enamel.

METHODS

Forty-eight enamel specimens were selected by surface hardness and randomly allocated into 4 groups (n = 12) according to the commercial toothpastes: non-fluoridated (NF); 1100 ppm Stannous fluoride (SnF₂); 1450 ppm MFP + calcium silicate + sodium phosphate (CSSP); CSSP + dual-phase gel (CSSP + Serum). Cyclic experiments were repeated 3x / day for five days, including an erosive challenge with 0.05 M citric acid (pH 3.75 for 30 s), treatment with toothpaste slurries (1 min), and remineralization with artificial saliva (pH 7.0 for 60 min). Surface alterations were determined by stylus profilometry (μm) and scanning electron microscopy (SEM). Data were analyzed by ANOVA and Tukey tests (α = 0.05).

RESULTS

SnF₂, CSSP and CSSP + Serum significantly reduce surface wear compared to NF treated group. Besides, there were no significant differences among SnF₂, CSSP and CSSP + Serum. In micrographs of both groups treated with CSSP, the surface demonstrates the presence of a protective layer as a deposition of particles.

CONCLUSIONS

Dentifrice containing calcium silicate and sodium phosphate with or without the dual-phase gel was able to prevent the erosive tooth wear.