The title оf this opening chapter ot the Alias requires immediate explanation. The term 'equation' refers to the balance which must be struck between the good and the bad which can arise Irom partial dentures. In this chapter we explore the benefits conferred on the patient by a partial denture and, at the same time, highlight the possible risks of tissue damage by such a demure Ultimately, the deeision on whether or not to provide a partial demure will be influenced by a consideration of this equation and also bv the level of patient motivation.