Symbolism is something that is most interestingly explored through the title of the novel itself. White Teeth is a title that draws attention to the one aspect of humanity that unites us all and transcends the colour of our skin and differences that humans impose on each other as a result of ethnicity and culture. This is key in a novel where Smith deliberately explores multiculturalism and seeks to present a radically different view of contemporary Britain. In a novel where difference is such a focus, the title reminds the reader that there are aspects of humanity that are common to all humans, and having white teeth is just one of those.
Also consider how the symbol of teeth is used to explore the past of characters. In Chapter 5, entited "The Root Canals of Alfred Archibald Jones and Samad Miah Iqbal," for example the "root canals" are never literally mentioned, but rather function as symbols of the past of these two characters that Smith chooses to reveal. Note how this chapter begins:
A propos: it's all very well, this instruction of Alsana's to look at the thing close up; to look at it dead-straight between the eyes; an unfliching and honest stare, a meticulous inspection that would go beyond the heart of the matter to its marrow, beyond the marrow to the root--but the question is how far back to you want? How far will do?
Smith therefore uses the symbol of teeth to explore the past of various characters and to present her view that to fully live in the present humans must balance their past experiences with their hoped for futures. Delving into the past can be painful, as it can expose some decay, as this chapter makes clear, yet it is important to do so in order to lead a happy life. This is shown through the character of Samad, who places so much stress on his cultural heritage and his hoped for future that he fails to ever live in the present and enjoy it.