The abnormal existing long axis of the premolars is probably related to anterior crowding (Fig.12).  The roots of the premolars remains in the original place, while the crowns shift anterior (arrow).  Therefore, it is justifiable to change the trajectory of the implant.   In addition, more new bone is gained for primary stability when the trajectory is changed. 

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Xin Wei, DDS, PhD, MS 1st edition 12/12/2014, last revision 01/19/2018