Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain
the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in
Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles
and JavaScript.
"Coloured scanning electron micrograph (SEM) of a tooth (green) with a dental crown (light blue). The tooth and ceramic crown are coated in debris (orange) which became attached to the tooth when it was extracted for this SEM. Magnification: x10 at 6 x 7 cm size." COVER IMAGE copyright VOLKER STEGER/SCIENCE PHOTO LIBRARY