To learn more about "missing teeth" in urban centers, take a listen to this podcast:

"Empty Spaces in the Streetscape"

In this podcast, James Howard Kunstler explains the negative effects that empty building lots have on the urban streetscape. These empty spaces or 'missing teeth' are dead zones that are repellent to pedestrians. But, at the moment, our car crazy society prefers to keep those dead zones for surface parking rather than to infill them with good urban buildings. (Released Dec 18, 2008)

Urban Design Resources: