The present invention relates to silicone-based dental compositions based on a functionalized silicone crosslinkable and/or polymerizable by heat-process. These novel dental compositions are polymerizable and/or crosslinkable in an oral environment, have markedly improved qualities, in particular as regards the very marked reduction in the phenomenon of shrinkage of the materials and prostheses obtained from said compositions. These novel dental compositions are particularly advantageous in terms of reactivity; they are crosslinkable and/or polymerizable by heat, which makes it possible to use conventional crosslinking/polymerization methods and furthermore at temperatures of less than 150.degree. C. This reactivity is in particular due to the presence of a particular type of initiator based on a boron derivative; That initiator is active in low concentration and advantageously requires only small quantities of energy to carry out the crosslinkage/polymerization.