Introduction The aim of this study was to evaluate the effect of the order of preparation of four-
canal maxillary molars on volume variation, instrument deformation, cyclic fatigue, and
preparation time by using the WaveOne Gold Primary (WOG 25.07). Methods We selected
48 permanent, human, four-canal maxillary molars. The teeth were divided into 4 groups
according to the order of initiation of the canal preparation sequence:(1) mesiobuccal (MB),
distobuccal (DB), palatal (P), second mesiobuccal (MB2);(2) DB-P-MB2-MB;(3) P-MB2-MB …