We present a case study to illustrate the design and implementation of a teaching sequence about oral and dental health and hygiene. This teaching sequence was aimed at year 10 students (age 15-16) and sought to develop their scientific competences. In line with the PISA assessment framework for science and the tenets of a context-based approach to science education, the design of the teaching sequence was based on real-life situations. After setting out these premises the paper describes and illustrates the stages and tasks involved in the teaching sequence, and discusses certain aspects of its implementation. We conclude by considering a number of issues related to the teaching sequence, including its transfer to teachers.