A biological model for evaluating pulpo-dentinal capping materials is described. The model uses cultures of human pulp cells which are explanted to form cell monolayers. Four products already tested in vivo on teeth subsequently extracted for orthodontic reasons were laid directly over these cultures and observed after 7, 14, 21 and 28 days, corresponded to the in vivo test periods. The growth and morphology of the cells were similar for both test systems, indicating comparability between the two biological models as well as the validity of the developed in vitro method. A preliminary scale of biological activity is proposed which could be useful for preliminary screening of materials.