The nuts and bolts of hemisection treatment: managing congenitally missing mandibular second premolars.

When you treat the congenital absence of mandibular second premolars by extracting the residual deciduous second molar and closing the space, you run the risk of flattening facial fullness, especially in patients with nonextraction features--diminished facial fullness, absence of crowding, and reduced tooth size. This challenge is heightened by the increased likelihood that these features will occur in patients who have agenesis. This article describes a new approach that has been shown to minimize such a loss of anchorage. The technique is called hemisection and involves buccolingual sectioning of the second deciduous molar, followed by removal of its distal half. As necessary, the mesial half is also removed, and space closure can be completed. The advantages, philosophy, and technique are discussed in detail.