Tag Archives: dentin

Nano with green tea for sensitive teeth

The future will be beautiful if scientists are successful with a new DNA (deoxyribonucleic acid) sunscreen (my Aug. 3, 2017 posting) and a new dental material for people with sensitive teeth. From an Aug. 2, 2017 news item on phys.org,

An ice cold drink is refreshing in the summer, but for people with sensitive teeth, it can cause a painful jolt in the mouth. This condition can be treated, but many current approaches don’t last long. Now researchers report in the journal ACS [American Chemical Society] Applied Materials & Interfaces the development of a new material with an extract from green tea that could fix this problem—and help prevent cavities in these susceptible patients.

An Aug. 2, 2017 ACS news release, which originated the news item, describes the problem and the work in more detail,

Tooth sensitivity commonly occurs when the protective layers of teeth are worn away, revealing a bony tissue called dentin. This tissue contains microscopic hollow tubes that, when exposed, allow hot and cold liquids and food to contact the underlying nerve endings in the teeth, causing pain. Unprotected dentin is also vulnerable to cavity formation. Plugging these tubes with a mineral called nanohydroxyapatite is a long-standing approach to treating sensitivity. But the material doesn’t stand up well to regular brushing, grinding, erosion or acid produced by cavity-causing bacteria. Cui Huang and colleagues wanted to tackle sensitivity and beat the bacteria at the same time.

The researchers encapsulated nanohydroxyapatite and a green tea polyphenol — epigallocatechin-3-gallate, or EGCG — in silica nanoparticles, which can stand up to acid and wear and tear. EGCG has been shown in previous studies to fight Streptococcus mutans, which forms biofilms that cause cavities. Testing on extracted wisdom teeth showed that the material plugged the dentin tubules, released EGCG for at least 96 hours, stood up to tooth erosion and brushing and prevented biofilm formation. It also showed low toxicity. Based on these findings, the researchers say the material could indeed be a good candidate for combating tooth sensitivity and cavities.

The authors acknowledge funding from the National Natural Science Foundation of China, the Natural Science Foundation of Hubei Province of China and the Fundamental Research Funds for the Central Universities.

Here’s a link to and a citation for the paper,

Development of Epigallocatechin-3-gallate-Encapsulated Nanohydroxyapatite/Mesoporous Silica for Therapeutic Management of Dentin Surface by Jian Yu, Hongye Yang, Kang Li, Hongyu Ren, Jinmei Lei, and Cui Huang. ACS Appl. Mater. Interfaces, Article ASAP DOI: 10.1021/acsami.7b06597 Publication Date (Web): July 13, 2017

Copyright © 2017 American Chemical Society

This paper is behind a paywall.

Discovering why your teeth aren’t perfectly crack-resistant

This helps make your teeth crack-resistant?

Caption: Illustration shows complex biostructure of dentin: the dental tubuli (yellow hollow cylinders, diameters appr. 1 micrometer) are surrounded by layers of mineralized collagen fibers (brown rods). The tiny mineral nanoparticles are embedded in the mesh of collagen fibers and not visible here. Credit: JB Forien @Charité

Caption: Illustration shows complex biostructure of dentin: the dental tubuli (yellow hollow cylinders, diameters appr. 1 micrometer) are surrounded by layers of mineralized collagen fibers (brown rods). The tiny mineral nanoparticles are embedded in the mesh of collagen fibers and not visible here. Credit: JB Forien @Charité

A June 10, 2015 Helmholtz Zentrum Berlin (HZB) press release (also on EurekAlert) explains how the illustration above relates to the research,

Human teeth have to serve for a lifetime, despite being subjected to huge forces. But the high failure resistance of dentin in teeth is not fully understood. An interdisciplinary team led by scientists of Charite Universitaetsmedizin Berlin has now analyzed the complex structure of dentin. At the synchrotron sources BESSY II at HZB, Berlin, Germany, and the European Synchrotron Radiation Facility ESRF, Grenoble, France, they could reveal that the mineral particles are precompressed.

The internal stress works against crack propagation and increases resistance of the biostructure.

Engineers use internal stresses to strengthen materials for specific technical purposes. Now it seems that evolution has long ‘known’ about this trick, and has put it to use in our natural teeth. Unlike bones, which are made partly of living cells, human teeth are not able to repair damage. Their bulk is made of dentin, a bonelike material consisting of mineral nanoparticles. These mineral nanoparticles are embedded in collagen protein fibres, with which they are tightly connected. In every tooth, such fibers can be found, and they lie in layers, making teeth tough and damage resistant. Still, it was not well understood, how crack propagation in teeth can be stopped.

The press release goes on to describe the new research and the teams which investigated the role of the mineral nanoparticles with regard to compression and cracking,

Now researchers from Charite Julius-Wolff-Institute, Berlin have been working with partners from Materials Engineering Department of Technische Universitaets Berlin, MPI of Colloids and Interfaces, Potsdam and Technion – Israel Institute of Technology, Haifa, to examine these biostructures more closely. They performed Micro-beam in-situ stress experiments in the mySpot BESSY facility of HZB, Berlin, Germany and analyzed the local orientation of the mineral nanoparticles using the nano-imaging facility of the European Synchrotron Radiation Facility (ESRF) in Grenoble, France.

When the tiny collagen fibers shrink, the attached mineral particles become increasingly compressed, the science team found out. “Our group was able to use changes in humidity to demonstrate how stress appears in the mineral in the collagen fibers, Dr. Paul Zaslansky from Julius Wolff-Institute of Charite Berlin explains. “The compressed state helps to prevents cracks from developing and we found that compression takes place in such a way that cracks cannot easily reach the tooth inner parts, which could damage the sensitive pulp. In this manner, compression stress helps to prevent cracks from rushing through the tooth.

The scientists also examined what happens if the tight mineral-protein link is destroyed by heating: In that case, dentin in teeth becomes much weaker. We therefore believe that the balance of stresses between the particles and the protein is important for the extended survival of teeth in the mouth, Charite scientist Jean-Baptiste Forien says. Their results may explain why artificial tooth replacements usually do not work as well as healthy teeth do: they are simply too passive, lacking the mechanisms found in the natural tooth structures, and consequently fillings cannot sustain the stresses in the mouth as well as teeth do. “Our results might inspire the development of tougher ceramic structures for tooth repair or replacement, Zaslansky hopes.

Experiments took place as part of the DFG project “Biomimetic Materials Research: Functionality by Hierarchical Structuring of Materials (SPP1420).

Here’s a link to and a citation for the paper,

Compressive Residual Strains in Mineral Nanoparticles as a Possible Origin of Enhanced Crack Resistance in Human Tooth Dentin by Jean-Baptiste Forien, Claudia Fleck, Peter Cloetens, Georg Duda, Peter Fratzl, Emil Zolotoyabko, and Paul Zaslansky. Nano Lett., 2015, 15 (6), pp 3729–3734 DOI: 10.1021/acs.nanolett.5b00143 Publication Date (Web): May 26, 2015

Copyright © 2015 American Chemical Society

This paper is behind a paywall.