Figure 1. The FE models and their characteristics. (A) Parts of the FE model; the maxillary central incisor (I), the PDL (P), the cortical bone (Co), the cancellous bone (Ca), and completed models with normal bone height (N) and reduced height (R). (B) Load-deflection curves of the incisors under horizontal force, from labial to lingual. The solid lines indicate the load-deflection relation reported by in vivo data (Mühlemann, 1951), and the 4 dotted curves represent those of the FE models of the present study: the models of normal bone height with normal and widened PDL space, and those of reduced bone height with normal and widened PDL space. (C) Stress-strain relation used to express the non-linear material property of the PDL used in the models of this study.