Researchers led by Olivier Duverger of the National Institutes of Health-National Institute of Neurological Disorders and Stroke in Maryland have established a connection between hair disorders and an increased susceptibility to dental cavities.
While it has been known for some time that there are similarities in the ways that teeth and hair grow, the fact they are made of different structures means the two have not previously been further connected. Hair is formed from highly cross-linked strands of keratin, whereas tooth enamel is chiefly made of proteins such as amelogenin and ameloblastin, which degrade and mineralise as the enamel approaches maturity.
However, enamel also contains a small amount of cross-linked organic material that had not been fully identified before the study was carried out. It is now believed that the material is a specific form of hair keratin, and has a major impact on teeth’s resistance to cavities.
A mutation in keratin structures that make up hair were found to correlate with higher incidences of tooth decay in mice. The mutation in question was caused by a lack of distal-less homeobox 3 (DLX3), a transcription factor. Immunolocalization of hair keratins was carried out on both mouse enamel organ and mature human enamel.
The forms of epithelial keratin limited by the lack of DLX3 are also known to be a major part of tooth enamel in adult humans. Low levels of these keratins were found to reduce the enamel’s micro-hardness during the maturation and mineralisation processes thanks to transmission and scanning electron microscopy, micro-computed tomography and micro-hardness testing. This lack of micro-hardness is a risk factor for cavities and other forms of tooth decay.
The research was presented at the 93rd General Session and Exhibition of the International Association for Dental Research, and is set to be published under the title “Hair Keratins as Structural Organic Components of Mature Enamel: The Link Between Hair Disorders and Susceptibility to Dental Caries”.