Ormocers, which can be obtained by the hydrolytic condensation of one or more silicon compounds, and the subsequent polymerization of organic monomers, wherein at least one silicon compound comprises vinyl ether radicals of formula : 1wherein R represents hydrogen, methyl, or ethyl. To enhance the opportunities for collaborations on a reply to the e-mail message, each of the messaging servers supporting the addressees maintains a message record identifying each addressee that signals he has begun working on a reply. A registration device is engageable with each of the implants in a predefined relative position.