The use of posts as the foundation of dental restorations goes back to the earliest days of modern dentistry, but the materials, design and effectiveness of these posts has advanced greatly since the days of Pierre Fauchard. Today there are numerous systems of pre-fabricated posts that can become the foundation of the restoration of an endodontically treated tooth. These posts commonly simply fit into the canal to provide passive retention, but in some cases a post that can actively grip the dentin is a key to success. Here is a look at several endo post systems providing active retention.