In this paper we seek to further investigate whether having different backgrounds influences Engineering teachers' views of Calculus and shapes their opinion of how the subject should be taught, and whether these views affect their actual teaching practices. Our research is based on an institutional perspective and employs Chevallard's Anthropological Theory of the Didactic (ATD), in particular the notion of personal relationship, and we analyse the possible impacts of institutional choices on an individual's practices. Our data seem to indicate that even when they occupy the same position in the same institution, teachers with different academic backgrounds hold quite different personal relationships with the contents of their Calculus course, and that this has a significant impact on their practices.