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Current tooth enamel repair technologies generally involve stimulation of natural regeneration or the addition of (partial or full) artificial lining material in more severe cases. However, these techniques are quite limited as they are not necessarily durable in the long term and can sometimes even weaken the tooth. Biomaterials, which are the most famous guides today, scientists recently found a way to improve the structure of hydroxyapatite to create a new type of dental coating that mimics the structure of natural enamel and makes it more durable than the other. The new material would ultimately prevent tooth erosion or repair cracks and fractures more effectively.
Tooth enamel, the hardest tissue in the human body, plays an important role in protecting teeth from decay and tartar. Despite its great resistance, it can erode during a person’s life, especially through poor diet, poor oral hygiene, decalcification, abrasions, etc. Unlike most body tissues, including bones (with which it is often associated), it cannot regenerate. By cracking, it then loses its protective function and leaves the passage – up to the dentin and pulp – free for the microbial flow constantly present in the oral cavity.
” It is therefore necessary to restore the enamel surface to a healthy level or build up additional layers on the surface if it is very thin. », Explain Pavel Seredin, a researcher at Ural Federal University, head of the Department of Physics of Solids and Nanostructures at Voronezh State University in Russia, and lead author of the new study. To repair enamel, dentists often use artificial materials that seal cracks like cement.
However, because enamel is mainly composed of apatite (an inorganic biological substance that makes up 95% of its weight), collagen fibers (1 to 1.5%) and water (4%), composite dentures do not have the ability to physically and chemically bond to it . Acid etching techniques are used to effectively bond these materials to healthy enamel. These techniques are sometimes not effective enough and can even damage the enamel even more.
Restorative technologies have benefited from major advances in natural enamel regeneration with the goal of doing (if possible) without these composite materials. They consist, for example, in the use of special gels or toothpastes loaded with peptides or low-power laser beams to stimulate the differentiation of stem cells into ameloblasts. Biomaterials such as hydroxyapatite are also used to remineralize enamel to restore its mechanical properties.
Researchers of the new study, published in the journal Science Direct, may have found an even more efficient way to achieve this by improving the resistivity of hydroxyapatite. This material, which consists mainly of mineralized human and animal tissues, is commonly used in various medical fields such as orthopedics and cosmetology. Manufactured in a laboratory using calcified materials such as eggshells, its structure can be easily modelled. The new study, led jointly by Al-Azhar University and the National Research Center of Egypt, aimed to find the best structure to improve the increase in enamel resistance.
From hydroxyapatite “doped” with amino acids
In a new study, scientists created a biomimetic mineralized coating whose nanocrystals reproduce the properties of those that make up natural enamel apatite. They also added a complex of amino acids to reproduce a molecular structure similar to the surface of a tooth, but with greater resistance.
Amino acids such as lysine, arginine and histidine are really important factors in the regeneration of bone and muscle tissue. Under the right environmental conditions, amino acid “doped” hydroxyapatite is able to perfectly mimic natural enamel. ” To reproduce the enamel layers with biomimetic techniques, we neutralized and removed the etching products using calcium alkali. In this way, we improved the bonding of the new hydroxyapatite layers ” says Seredin.
The structural similarity to natural enamel was confirmed by field emission analysis and atomic force electron microscopy, as well as by chemical imaging of surfaces using Raman microspectroscopy (which consists in sending a beam of monochromatic light onto the sample and analyzing the scattered light). In addition, the new coating was tested on healthy teeth to assess the increase in resistance compared to other untreated healthy teeth.
The promising results show that the new material could be used to reduce tooth sensitivity after abrasion or erosion. The next phase of the study will be to assess its effectiveness for deeper fillings, including volume cracks and fractures.