Contemporary methods of resection and management of the root end during apical surgery were reviewed. Two studies are reported here, one on the amount of peripheral root structure remaining after root-end cavity preparation in maxillary central incisors and canines, and the other on the effect of the dimensions of the cut root face on the size of the root-end cavities cut by experienced endodontists. To investigate the amount of peripheral root structure remaining after root-end cavity preparation, three senior endodontic graduate students were asked to prepare conservative root-end cavities in thirty root-treated maxillary central incisors and thirty canines. Not a single tooth had the recommended 2 mm circumferential root dentine after 3 mm resection. Sixty two percent of the central incisors did not have a 2 mm dentine periphery around the root-end cavity preparations after 6 mm resection. To investigate the effect of the dimensions of the cut root face on the size of root-end cavities, five practicing endodontic specialists prepared conservative root-end cavities in thirty single-rooted teeth each after resection of the apical 3 mm. The endodontists prepared larger cavities in larger root faces. More precisely, the cavity sizes suggested that the endodontists were suffering from the effects of a visual illusion, the Delboeuf illusion. There are two major conclusions. First, the theory concerning the amount of circumferential dentine in a resected root face needs revision. Second, endodontists need to be aware of how the appearance of a cut root face can influence the size of cavities they cut.