Polyethylene-glycol coated maghemite nanoparticles for treatment of dental hypersensitivity

doi:10.1016/j.matlet.2014.01.120

Materials Letters

Volume 121, 15 April 2014, Pages 89-92

https://doi.org/10.1016/j.matlet.2014.01.120 Get rights and content

Highlights

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We used PEG-maghemite nanoparticles for treating dental hypersensitivity.
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We synthesized PEG-maghemite nanoparticles with particle sizes smaller than 25 nm.
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These nanoparticles are able to effectively occlude dental tubules after 120 min.
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These nanoparticles could transfer other therapeutic agents inside the tubules.

Abstract

Dental hypersensitivity is a common oral problem that is directly related to the number and the diameter of dental tubules. Therefore, the occlusion of the tubules using compounds capable of penetrating and precipitating into dental tubules may result in a long-lasting remedy to this problem. In this in-vitro study, the ability of polyethylene-glycol coated maghemite nanoparticles for treating dental hypersensitivity was investigated. Due to their superparamagnetic characteristics, these nanoparticles are susceptible to navigation inside the dental tubules via an external magnetic field. The experiments were performed in various durations for the purpose of determining the optimum time for the effective occlusion of dental tubules. Our findings showed that the polymer-coated maghemite nanoparticles exhibited a significant potential for reducing the permeability of dental tubules by occluding the open tubular area after a 120 min.

Introduction

Dental hypersensitivity is defined as “a short sharp pain arising from exposed dentin in response to stimuli typically thermal, evaporative, tactile, osmotic, or chemical and which cannot be ascribed to any other form of defect, pathology, or disease” [1]. In other words, it means a painful response to stimuli(s) that is not normally associated with pain [2]. The main cause of dental hypersensitivity is open dental tubules (microscopic channels in the dentin), which serve as direct links between the external environment and the pulp. Previous studies have demonstrated that the dental tubules in hypersensitive dentins are larger in both number and diameter compared to non-sensitive dentin [3]. Therefore, it can correctly be assumed that the severity of dental hypersensitivity is related to the number and width of dental tubules.

Dental tubule occlusion is one of the principal strategies for the treatment of dental hypersensitivity which involves the use of compounds that can precipitate inside the tubules and plug their orifices. However, the micron-sized diameter of dental tubules presents a physiological limitation for diffusion of large therapeutic compounds. Therefore in this protocol, fine particle size is crucial as it allows a faster and deeper deposition of particles inside the dental tubules. Based on this fact, several biomaterials have been synthesized in the nanoscale for treatment of dental hypersensitivity, including gold [4], hydroxyapatite [5], carbonate apatite [6], calcium oxide–mesoporous silica [7], and nanolipid carriers [8]. Although these agents have yielded promising results, the navigation of such nanoparticles inside the tubules remains a challenge [9].

In this research, we have studied the possibility of using polyethylene-glycol coated maghemite nanoparticles (PEG-MNPs) for treating dental hypersensitivity. We assumed that the maghemite nanoparticles (MNPs) could be navigated inside the tubules via an external magnetic field. The PEG coating acts as a protective layer for minimizing the aggregation and biofouling of MNPs in physiological conditions for long periods [10], [11], [12]. The biocompatibility of both PEG and maghemite compounds makes the PEG-MNPs attractive candidates for the fast and effective treatment of dental hypersensitivity.

Section snippets

Materials and methods

Maghemite nanoparticles were synthesized via the modification of the recipes described in literature [13], [14]. In our method, the synthesis was performed in an aqueous medium and air atmosphere (instead of nitrogen) for a more facile production of nanoparticles. In a typical synthetic process, 1.0 mL of 2 M ferrous sulfate heptahydrate (FeSO₄·7H₂O) and 3.5 mL of 1 M ferric chloride (FeCl₃) were mixed in 25 mL of distilled water, and then 25 mL of ammonium hydroxide (NH₄OH, 33% NH₃ in water)

Results and discussion

Fig. 1a shows a TEM image of the synthesized nanoparticles. The diameter of the nanoparticles was mostly smaller than 25 nm, which was suitable for filling the dental tubules. The photomicrograph of a typical untreated specimen is shown in Fig. 1b, which presents a smooth dentin surface without any smear layer covering the tubules׳ orifices.

Fig. 2 shows the SEM images of the M60 samples before rinsing with water. This figure presents two significant modes of tubular occlusion by PEG-MNPs before

Conclusion

In this study, the permeability of polyethylene-glycol coated maghemite nanoparticles into dental tubules was examined via an external magnetic field. Moreover, the effect of exposure time to external magnetic field on the occlusion ratio of the tubules was also investigated. The results of this study provide a confirmation of the research hypothesis that polyethylene-glycol coated maghemite nanoparticles are able to occlude the open dental tubules, and could be used in dental hypersensitivity

Acknowledgments

We wish to thank the Ministry of Science, Technology and Innovation (MOSTI) Malaysia (Science fund: 06-01-03-SF0587) and University of Malaya (Research Grant No: RG055/09HTM) for financing this project. The authors state no conflict of interest.

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View full text

Polyethylene-glycol coated maghemite nanoparticles for treatment of dental hypersensitivity

Highlights

Abstract

Introduction

Section snippets

Materials and methods

Results and discussion

Conclusion

Acknowledgments

Mater Lett

Mater Lett

Mater Lett

Mater Lett

Mater Lett

Guidelines for the design and conduct of clinical trials on dentine hypersensitivity

J Clin Periodontol

Clinical dentin hypersensitivity: understanding the causes and prescribing a treatment

J Contemp Dent Pract