1Chapman CE.A microscopic study of the apical region of human anterior teeth.J Br Endod Soc,1969,3:52-58.
2Altrnan M,Guttuso J,Seidberg BH,et al.Apical rood canal anatomy of human maxillary central incisors.Oral Surg Oral Med Oral Pathol,1970,30:694-699.
3Dummer PM,McGinn JH,Rees DG.The position and topography of the apical canal constriction and apical foramen.Int Endod J,1984,17:192-198.
4Gutmann J,Dumsha T,Lovdahl P,et al.Problem solving in endodontics.4rd eds.St Louis:C.V.Mosby,2005.155-195.
5Kuttler Y.Microscopic investigation of root apexes.J Am Dent Assoc,1955,50:544-552.
6Ricueci D.Apical Limit of root canal instrumentation and obturation,part 1.Literature review.Int Endod J,1998,31:384-393.
7Ricucci D,Langeland K.Apical limit of root canal instrumentation and obturation,part 2.A histological study.Int Endod J,1998,31:394-409.
8Wu MK,R'oris A,Barkis D,et al.Prevalence and extent of long oval canals in the apical third.Oral Surg Oral Med Oral Path Oral Radio Endod,2000,89:739-743.
9Jou YT,Karabocak B,Levin J,et al.Endodontic working width:current concepts and techniques.Dent Clin North Am,2004,48:323-335.