K-slide 1: A. Cortical plate [Buccal] B. Cortical plate [Lingual] C. Alveolar bone proper D. Spongiosa E. Periodontal ligament F. Coronal dentin G. Radicular dentin H. Pulp (coronal and radicular) I. Inferior alveolar canal Note how the PDL narrows near the middle to lower one-third of the root. This indicates the area of the tooth's fulcrum through which tipping (tilting) takes place.   next return to index