Recent advances in the use of inorganic nanomaterials as anti caries agents

Abstract

Caries is the most prevalent and widespread chronic oral disease. Traditional caries filling materials, due to their lack of anti-caries capabilities, can readily develop secondary caries. Nanomaterials proposed as an effective approach for caries treatment can inhibit biofilm formation. It also can not only reduce demineralization but also promote remineralization. In recent years, nanotechnology in anti-caries materials, particularly nano-adhesive and nano-composite resin, has advanced rapidly. Because inorganic nanoparticles (NPs) interfere with bacterial metabolism and inhibit biofilm development, inorganic NPs have emerged as a new trend in dental applications. Metal and metal oxide NPs by releasing metal ions, oxidative stress induction, and non-oxidative mechanisms showed significant antimicrobial activity. For applying metal and metal oxide NPs as anti caries agents, silver, zinc, titanium, copper, and calcium ions have been shown significant attention. Moreover, fluoride functionalized inorganic NPs were also employed to improve their efficacy of them. The fluoride-functionalized NPs can promote remineralization, and inhibit demineralization by enhancing apatite formation. In this review, we have provided an overview and recent advances in the use of inorganic NPs as anti caries agents. Furthermore, their antimicrobial, remineralizing, and mechanical impacts on dental materials were discussed.

Keywords: Anti-caries; Biofilm; Inorganic; Metal; Remineralization.

Fig. 1

Application of nanomaterials in dentistry. Reproduced with permission from Ref. [38], with the permission of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/). Copyright 2022, MDPI.

Fig. 2

Dental nanomaterials available on the market. Reproduced with permission from Ref. [48], with the permission of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/). Copyright 2021, MDPI.

Fig. 3

a) SEM images and EDS mapping of the uncoated NiTi alloy sample. b) SEM images and EDS mapping of the 10 min GO/AgNPs coated NiTi alloy sample (CT10). Black arrows indicate the GO assembly with the Ag NPs. Reproduced with permission from Ref. [63], with the permission of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/). Copyright 2021, Springer Nature.

Fig. 4

a–h) Inhibition of virulence genes in S. mutans exposed to different concentrations of AgNPs. Reproduced with permission from Ref. [64], with the permission of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/). Copyright 2021, Elsevier.

Fig. 5

a–d) TEM images of the NFS, and e) Photograph of tooth treated with NSF after 12 months. Reproduced with permission from Ref. [71], with the permission of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/). Copyright 2014, Elsevier.

Fig. 6

SEM images of S. mutans mature biofilm adhered to a–b) unmodified, modified composite resin specimens with c–d) 1% of ZCS NPs, e–f) 2% of ZCS NPs, g–h) 1% of ZPS NPs and i–j) 2% of ZPS NPs. Reproduced with permission from Ref. [72]. Copyright 2019, with permission from Elsevier.

Fig. 7

a) Schematic illustration of antibacterial activity of Ag/ZnO assisted with LED curing light. b) antibacterial activity of 1 mg/mL Ag/ZnO or ZnO and 40 μg/mL Ag NPs against planktonic S. mutans with or without 5 min LED illumination. Reproduced with permission from Ref. [76]. Copyright 2019, with permission from ACS.

Fig. 8

The effect of ZnO NPs with different morphology on antimicrobial activity (number of colonies). Reproduced with permission from Ref. [83], with the permission of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/). Copyright 2021, Hindawi.

Fig. 9

a) Hemolytic effect of Zeo/ZnONPs. b) Cytotoxic effects of Zeo/ZnONPs on cell viability of HuGu cells. c) Intracellular ROS production in polymicrobial suspension following different treatments. Reproduced with permission from Ref. [89], with the permission of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/). Copyright 2021, BMC.

Fig. 10

Schematic illustration of the effects of ZnO₂–Cu@RB NPs on S. mutans and its oral biofilm. Reproduced with permission from Ref. [97]. Copyright 2022, with permission from Elsevier.

Fig. 11

a) Calcium (Ca) and b) phosphate (P) ion releases from the 3% DMAHDM + 30% amorphous calcium phosphate NPs composite immersed in solutions of pH 4 and 7. Reproduced with permission from Ref. [103]. Copyright 2020, with permission from Elsevier.

Fig. 12

Schematic of the experimental design illustrating the reversal-remineralizing pH-cycling model. A. The artificial caries-like lesions are created in the pit and fissures of all teeth. The initial surface hardness is assessed. B. The caries-like lesions are sealed using the tested formulation and subjected to pH cycling for 5 days. C. The final surface hardness is assessed. Reproduced with permission from Ref. [105]. Copyright 2020, with permission from Elsevier.

Fig. 13

a) Viable count of S. mutans in all the groups. b) Mean distribution of the microbial count (×10⁶) in all the groups. Reproduced with permission from Ref. [111]. Copyright 2020, with permission from Elsevier.

Fig. 14

Schematic illustration of demineralization of enamel and remineralization process by SN15-PAMAM + amorphous calcium phosphate NPs adhesive. Reproduced with permission from Ref. [112]. Copyright 2020, with permission from Elsevier.

Fig. 15

Remineralization of enamel after 30 days of demineralization-remineralization cycles (mean ± sd; n = 6). a) Surface hardness of enamel. b) Lesion depth of enamel. Reproduced with permission from Ref. [114]. Copyright 2020, with permission from Elsevier.