Application of cerium chloride to improve the acid resistance of dentine

doi:10.1016/j.archoralbio.2010.03.016

Archives of Oral Biology

Volume 55, Issue 6, June 2010, Pages 441-446

https://doi.org/10.1016/j.archoralbio.2010.03.016 Get rights and content

Abstract

Objective

To investigate the effect of cerium chloride, cerium chloride/fluoride and fluoride application on calcium release during erosion of treated dentine.

Methods

Forty dentine samples were prepared from human premolars and randomly assigned to four groups (1–4). Samples were treated twice a day for 5 days, 30 s each, with the following solutions: group 1 placebo, group 2 fluoride (Elmex fluid), group 3 cerium chloride and group 4 combined fluoride and cerium chloride. For the determination of acid resistance, the samples were consecutively eroded six times for 5 min with lactic acid (pH 3.0) and the calcium release in the acid was determined. Furthermore, six additional samples per group were prepared and used for EDS analysis. SEM pictures of these samples of each group were also captured.

Results

Samples of group 1 presented the highest calcium release when compared with the samples of groups 2–4. The highest acid resistance was observed for group 2. Calcium release in group 3 was similar to that of group 4 for the first two erosive attacks, after which calcium release in group 4 was lower than that of group 3. Generally, the SEM pictures showed a surface coating for groups 2–4. No deposits were observed in group 1.

Conclusion

Although fluoride showed the best protective effect, cerium chloride was also able to reduce the acid susceptibility of dentine significantly, which merits further investigation.

Introduction

Loss of dental hard tissues due to caries has declined over the last decades.¹ However, other causes of dental hard tissue loss or disintegration have entered into the focus of dentistry, e.g. erosion.² Dental erosion is defined as tooth wear due to chemical dissolution of dental hard tissue not involving bacteria.³ As implied by this definition, acids or acidic metabolites play a major role in dental hard tissue loss for both disease entities.

For the prevention of caries, it is evident that fluoride promotes remineralisation, inhibits demineralisation of dental hard tissues and the use of fluorides in different forms and different application modes has caused a reduction in the prevalence of dental hard tissue loss due to caries over the last decades.1, 4, 5, 6

In 1977, Davis and Winter⁷ also reported that erosive tooth wear could be reduced by the use of fluoridated tooth pastes when applied before an erosive challenge. Since then numerous other in vitro and in situ studies have been performed to examine erosive tooth wear and its prevention, especially focussing on enamel.8, 9, 10, 11, 12, 13 Studies dealing with dentine as a substrate are scarce.14, 15

Fluoride shows a protective effect against caries and erosion, but negative side effects such as fluorosis and toxicity have been reported.16, 17 To avoid these negative side effects, Zhang et al.¹⁸ tested the use of lanthanide solutions and combinations of lanthanides with sodium fluoride solutions for the prevention of carious-like lesion development. The toxicity of rare earth elements such as lanthanum and cerium is lower than that of fluoride and they show a lower tendency to accumulate in the liver, kidney and brain.¹⁹ It was shown that the protective effects of the different lanthanide solutions were comparable with those of fluoride solutions.¹⁸ Furthermore, on cementum, the combination of lanthanide solutions with fluoride solution showed higher acid resistance compared to fluoride-only solution. The effect of cerium compounds on the demineralisation process is not known.

This in vitro study was designed to determine the effect of a cerium solution and combined cerium/fluoride solution on the prevention of mineral loss in dentine during acidic attacks. Furthermore, the presumed protective effect would be compared to the known protection of a commercial fluoride solution. The hypothesis of this study, in consideration of the results of Zhang et al.,¹⁸ was that the protective effect of a cerium solution against acidic attacks would be equal to that of a fluoride solution and that the combination of fluoride and cerium solution would show even better protection than the fluoride solution alone.

Section snippets

Sample preparation

For the study, 40 dentine samples were prepared from ten human premolars that were extracted for orthodontic reasons and assigned to four experimental groups (1–4). Teeth were sectioned at the cementum–enamel junction with a water-cooled diamond disc and the pulp tissue was removed from the roots with endodontic files. The root surfaces were cleaned by scaling and flattened for 2 min with Sof-Lex™ polishing discs (3–9 μm grit, 3 M Espe, 3 M AG, Rüschlikon, Switzerland) and water as coolant. The

Calcium release into the acid

The amount of calcium released into the lactic acid during each of the six erosive attacks (EA 1–EA 6) for the four treatment groups is given in Table 1.

Statistically significant highest amounts of calcium released in the acid during each erosive attack (EA 1–EA 6) were observed for the samples treated with the placebo solution (group 1). The amount of calcium released into the acid decreased statistically significant from EA 1 (6.6 ± 0.5 μg) and EA 2 (6.6 ± 0.5 μg) to EA 6 (5.6 ± 0.6 μg) in this group (

Discussion

In the present study, dentine samples were prepared from human premolar roots. Various other studies concerning dentine erosion have used bovine dentine.14, 21, 22 An advantage of using bovine dentine is that it is easier to obtain a sufficient number of sound bovine teeth instead of human teeth.²³ However, wear due to erosion is higher for human dentine²⁴ so that human root dentine was used in the present study. Zhang et al.¹⁸ used dentine samples with intact cementum to test the preventive

Conclusion

By the results of the present study it can be concluded that the protective effect of cerium chloride alone is limited but the combined application of fluoride solution followed by a cerium chloride solution demonstrated quite promising results although distinctive protective effect was observed after fluoride application only. To substantiate this finding, further studies within a clinical framework should be performed.

Funding

None.

Competing interests

All authors declare that there is no conflict of interests concerning the materials used in this study.

Ethical approval

Not required.

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A review on biomedical and dental applications of cerium oxide nanoparticles ― Unearthing the potential of this rare earth metal
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Nanotechnology deals with particles ranging from 1 to 100 nm in size called as nanoparticles. These nano particles exhibit unique properties which find an application in many industries and medical fields. A growing body of evidence points out the newer developing technologies adopted in the field of medicine in terms of target therapies, imaging systems, drug deliveries, etc. is through the incorporation of nanoparticles. Cerium oxide nanoparticles have gained attention in the last decade due to exceptional properties such as redox activity, biofilm inhibition, antibacterial activity, anti-inflammatory activity, etc. The method of synthesis of cerium oxide nanoparticles plays a pivotal role in its application. It exhibits redox properties and catalytic activity and thus has found its use in biomedical applications. Nanoparticles are incorporated into dental materials such as restorative cements/sealants, adhesives, and denture systems to improve their properties. Among the various metal oxide nanoparticles, cerium oxide nanoparticles (CeO₂NPs) are known to exhibit lower toxicity to mammalian cells and possess unique antibacterial mechanism. In addition, they exhibit potent properties such as antitumor, anti-inflammatory, antibacterial activities, and functions as an immunosensor. CeO₂NPs have excellent scavenging properties for reactive oxygen species, which is why they are being considered for therapeutic purposes. In this review, various methods of synthesis of CeO₂NPs are discussed. Several factors that determine the particle size and morphology of these materials are important for biomedical and dental applications. Emphasis is given to preparation methods and variables such as calcination temperature, which have a profound effect on particle size and morphology. This article also presents various applications of CeO₂NPs in the biomedical and dental fields.
Calcium lactate pre-rinse increased fluoride protection against enamel erosion in a randomized controlled in situ trial
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Citation Excerpt :
However, these precipitates may be dissolved as the pH drops.1,7–9 To produce more acid resistant mineral precipitates, numerous studies have been devoted to assess the role of fluoride preparations containing polyvalent metal cations or organic compounds.10–20 In addition, some papers deal with strategies to increase the fluoride bioavailability in the oral cavity.
This in situ trial study was designed to evaluate whether calcium (Ca) pre-rinse would increase the fluoride (F) rinse protection against enamel erosion.
Fifteen volunteers participated in this split-mouth, 3-phase, crossover design study wearing a palatal appliance containing four sterilized bovine enamel slabs, for 10 days. In the 1st phase, five participants followed protocol A: daily rinse with a Ca lactate (CaL, 150 mmol/L, 1 min), followed by F (NaF 12 mmol/L, 1 min). Other five participants followed protocol B: daily rinse only with F, while the remainders followed protocol C: no rinse (negative control). Appliances were removed from the mouth and one side of the palatal appliance was exposed to a daily erosive challenge (0.05 M citric acid, 90 s); the other side served as control (deionized water – no erosion). In the 2nd phase volunteers were crossed over to other protocol and in the 3rd phase volunteers received the remaining protocol not yet assigned. Specimens were evaluated for surface loss using an optical profilometer.
Repeated-measures three-way ANOVA (p = 0.009) and Tukey's test showed that CaL pre-rinse followed by NaF rinse significantly decreased surface loss of enamel when performed prior to an erosive challenge in comparison with the condition in which NaF only was used.
Pre-rinse with CaL may increase the protection exerted by NaF against erosive wear.
Effect of cerium chloride application on fibroblast and osteoblast proliferation and differentiation
2012, Archives of Oral Biology
Citation Excerpt :
Zhang et al. tested the use of different lanthanide solutions and combinations of lanthanides with sodium fluoride, amongst them cerium, for the prevention of carious-like lesion development on root cementum and showed that the protective effects of the different lanthanide solutions.8 Recently, Wegehaupt et al. were able to confirm these results on dentine.9 Nevertheless, for any biomaterial applied in contact or close to human tissues, cytocompatibility of the materials depends not only on their physical and chemical surface properties but also on the initial response of the cells on the material surface.
This study investigated effects of cerium-chloride on fibroblast and osteoblast differentiation and proliferation.
MC3T3-E1 cells were plated for an alkaline phosphatase (ALP) activity test. On day 3, CeCl₃-solutions (1, 5 or 10, w/v%) were added. After 10 s, the solutions were aspirated and washed to remove residual CeCl₃. On day 6 ALP activity was determined. Cell activity and proliferation was assessed by thiazolyl blue tetrazolium dye reduction assay (MTT-test) also 3 days after exposure to the CeCl₃-solutions. Calcium deposition by preosteoblastic cells was determined 4 weeks after the exposure of the cells by alizarin red staining. Furthermore, in all experiments the influence of adding rhBMP-2 was tested. Statistical analysis was performed by repeated-measures ANOVA using the post hoc Fisher least significant difference (LSD) test. Statistical significance was set at p < 0.05.
Exposure to a Ce-solution of 1% or higher reduced ALP activity significantly. The addition of rhBMP-2 was able to elevate ALP activity above control level. MTT-test showed a significant decrease in cellular activity by 5% Ce or higher. The addition of rhBMP-2 had no positive effect. For human foreskin fibroblasts, exposure to even 10% Ce yielded a significant increase in cellular activity. Ce reduced calcium deposition to a level of below 50% of the control. The addition of rhBMP-2 restored mineral deposition to control levels for all Ce concentrations.
CeCl₃ had a stimulating effect on fibroblasts but a depressing influence on osteoblasts. However, adding rhBMP-2 could compensate the latter influence.
Long-term protective effect of surface sealants against erosive wear by intrinsic and extrinsic acids
2012, Journal of Dentistry
Citation Excerpt :
The amount of enamel was quantified by assignation of 32P in the collected solutions by determining the Cherenkow radiation and comparing this radiation with the radiation of known amounts of apatite. Different other studies concerning prevention of erosive dental hard tissue loss have also measured the amount of certain apatite minerals in the demineralisation solution by chemical analysis of minerals dissolved in the used erosive agent by Arsenazo III procedure,42,43 atomic absorption spectroscopy44 or by colorimetric methods.45,46 As one of the used surface sealants (Silicon Seal Nano Mix) contains apatite, it was not feasible to detect certain apatite minerals in the used solutions since the above listed methods are not able to differentiate between minerals dissolved from the sealed enamel or from the used surface sealant.
To test sealants to prevent erosive tooth wear caused by extrinsic and intrinsic acids under long-term exposition.
144 bovine enamel samples were randomly allocated to twelve groups (1–12). Samples of groups 1, 5 and 9 remained unsealed (positive controls), 2, 6 and 10 were sealed with Silicon Seal Nano Mix and 3, 7 and 11 with Seal&Protect. Groups 4, 8 and 12 were sealed with flowable composite (negative controls).
Groups 1–4 were immersed in artificial saliva, 5–8 in hydrochloric acid and groups 9–12 in citric acid for 28 days, respectively. After 1, 2, 4, 7, 11, 14, 21 and 28 days, solutions were renewed and enamel wear was quantified by assignation of ³²P in the solutions.
In all immersion solutions, lowest mineral loss was observed for the negative controls whilst highest loss was observed for unsealed positive controls.
In artificial saliva and citric acid, the loss from samples sealed with Seal&Protect was not significantly different compared with negative controls whilst loss in groups sealed with Silicon Seal Nano Mix was significantly higher.
In hydrochloric acid, loss from samples sealed with Seal&Protect was not different compared with that of negative controls up to 4 days. Except day 1, the mineral loss in the Seal&Protect group was significantly lower compared with that of the Silicon Seal Nano Mix group.
The tested resin based surface sealant is able to significantly reduce the erosive demineralisation of enamel caused by hydrochloric and citric acid even under long-term exposition.
Anti-erosive potential of amine fluoride, cerium chloride and laser irradiation application on dentine
2011, Archives of Oral Biology
Citation Excerpt :
Furthermore, a possible additive effect of concomitant laser irradiation through the solutions was tested. Taking in consideration that the uptake of fluoride is enhanced by laser irradiation through topical applied fluoride25 and the promising results by Wegehaupt et al.3 concerning the protective effect of cerium, the hypothesis of the present study was that the mineral loss due to erosion would be significantly reduced after application of cerium solutions and that an additional laser irradiation could improve dentine protection against demineralisation by enhancing the uptake of cerium into dentine. Ninety-six dentine samples were prepared from human premolars and were assigned to eight experimental groups (n = 12, per group).
Ninety-six dentine samples were prepared from human premolars and randomly assigned to eight groups (G1–G8). Samples were treated for 30 s with the following solutions: placebo (G1/G2), amine fluoride (Elmex fluid; G3/G4), cerium chloride (G5/G6) and combined fluoride/cerium chloride application (G7/G8). Samples of groups G2, G4, G6 and G8 were additionally irradiated with a carbon dioxide laser through the solutions for 30 s. Acid resistance was assessed in a six-time 5-min consecutive lactic acid (pH 3.0) erosion model and calcium release was determined by atomic absorption spectroscopy (AAS). Furthermore, six additional samples per group were prepared and subjected to EDS-analysis.
In the non-irradiated groups, specimens of G1 (placebo) showed the highest calcium release when compared to the other treatments (G3, G5 and G7). The highest acid resistance was observed for G7. In G3, calcium release was lower than in G5, but higher than in G7. In general (except for the placebo groups), calcium release in the laser-irradiated groups was higher compared with the respective non-irradiated groups. EDS showed a replacement of calcium by cerium and of phosphor by fluoride.
The highest anti-erosive potential was found after combined cerium chloride and amine fluoride application. Laser irradiation had not adjunctive effect.
Cerium and cerium-based materials in dental applications
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Application of cerium chloride to improve the acid resistance of dentine

Abstract

Objective

Methods

Results

Conclusion

Introduction

Section snippets

Sample preparation

Calcium release into the acid

Discussion

Conclusion

Funding

Competing interests

Ethical approval

Arch Oral Biol

J Dent

Arch Oral Biol

Arch Oral Biol

Am J Orthod Dentofacial Orthop

J Dent

The caries decline: a review of reviews

Eur J Oral Sci

Prevalence, incidence and distribution of erosion

Monogr Oral Sci

Salivary citrate and dental erosion; procedure for determining citric acid in saliva; dental erosion and citric acid in saliva

J Dent Res

Factors influencing the caries decline in Lithuanian adolescents—trends in the period 1993–2001

Eur J Oral Sci

The decline in dental caries among Belgian children between 1983 and 1998

Community Dent Oral Epidemiol

Effectiveness of fluoride in preventing caries in adults

J Dent Res

Dietary erosion of adult dentine and enamel. Protection with a fluoride toothpaste

Br Dent J

Influence of in vivo formed salivary pellicle on enamel erosion

Caries Res

Brushing abrasion of eroded bovine enamel pretreated with topical fluorides

Caries Res

The protective effect of fluoride treatments against enamel erosion in vitro

J Oral Rehabil

Protective effect of different tetrafluorides on erosion of pellicle-free and pellicle-covered enamel and dentine

Caries Res