2Orstavik D, Kerekes K, Eriksen HM. The periapical index: A scoring system for radiographic assessment of apical periodontitis [J]. Endod Dent Traumatol, 1986, 2(1):20-34.
3Maalouf EM, Gutmann JL. Biological perspectives on the non- surgical endodontic management of periradicular pathosis[J]. Int Endod J, 1994, 27(3) : 154-162.
4Walton R, Fouad A. Endodontic interappointment flare-ups: A prospective study of incidence and related factors[J]. J Endod, 1992, 18 (4) : 172-177.
5Fava LR. A comparison of one versus two appointment endodontie therapy in teeth with non-vital pulps[J]. Int Endod J, 1989, 22 (4) : 179-183.
6Albashaireh ZS, Alnegrish AS. Postobturation pain after single- and multiple-visit endodontic therapy. A prospective study[J]. J Dent, 1998, 26 (3) : 227-232.
7Smith CS, Setchell D J, Harry FJ. Factors influencing the success of conventional root canal therapy--a five-year retrospective study [J]. Int Endod J, 1993, 26(6):321-333.
8Sjogren U, Hagglund B, Sundqvist G, et al. Factors affecting the long-term results of endodontic treatment[J]. J Endod, 1990, 16 (10) : 498-504.
9Orstavik D. Time-course and risk analyses of the development and healing of chronic apical periodontitis in man[J]. Int Endod J, 1996, 29(3) : 150-155.