Prediction of periapical status and tooth extraction L. –L. Kirkevang 1,2 , D. Ørstavik 2 , G. Bahrami 3 , A. Wenzel 1 & M. Væth 4 1 Section of Oral Radiology, Department of Dentistry, Health, Aarhus University, Aarhus, Denmark; 2 Department of Endodontics, Institute of Clinical Dentistry, Faculty of Dentistry, University of Oslo, Oslo, Norway; 3 Section of Prosthetics, Department of Dentistry, Health, Aarhus University, Aarhus; and 4 Section for Biostatistics, Department of Public Health, Health, Aarhus University, Aarhus, Denmark Abstract Kirkevang L–L, Ørstavik D, Bahrami G, Wenzel A, Væth M. Prediction of periapical status and tooth extraction. International Endodontic Journal, 50,5–14, 2017. Aim To describe and analyse risk factors associated with prediction of periapical status, assessed using the full-scale Periapical Index (PAI) supplemented with extraction as outcome variable. Methodology In 1997–1998, 616 randomly selected individuals from Aarhus County, Denmark, underwent a full-mouth radiographic survey. All 616 were re-invited in 2003–2004 and in 2008–2009, when 473 and 363 persons, respectively, consented and attended a new radiographic examination. The study population of the present investigation included 330 persons who had participated in all three exami- nations, and 143 persons who had participated in the ﬁrst and second examination only. Using the full- mouth radiographic survey and interview informa- tion, the following variables were assessed: on person level – age, gender, smoking habits and number of teeth; on tooth level – presence of tooth, PAI, root ﬁll- ing, caries, marginal bone level, restoration, jaw and tooth group. The outcome variable was the 5 score PAI supplemented with extraction. The observation period was 5 years. Ordered logistic regression analy- ses were carried out for root ﬁlled and non-root ﬁlled teeth separately. The Regional Committee of Ethics approved the study. Results For both root ﬁlled teeth and non-root ﬁlled teeth, the baseline PAI score was the most important predictive factor of periapical status and extraction (P < 0.0001). Non-root ﬁlled teeth had in general a better outcome than root ﬁlled teeth. However, in non-root ﬁlled teeth, several other factors had a sig- niﬁcant inﬂuence on the outcome, and the risk esti- mates were larger and showed a more pronounced variation between the different categories of predictive factors. For root ﬁlled teeth few variables, other than baseline PAI score, inﬂuenced the outcome signiﬁ- cantly. Conclusion The full-scale PAI was the strongest predictive factor of periapical status or extraction even when adjusted for additional factors, such as marginal bone level. A high baseline PAI score increased the risk for an impaired outcome. The large difference in risk estimates for non-root ﬁlled compared to root ﬁlled teeth documents the importance of separate analyses/studies for identiﬁcation and quantiﬁcation of predictive factors associated with periapical status and extraction of a tooth. Keywords: apical periodontitis, extraction, PAI, prediction, risk factors. Received 19 August 2015; accepted 11 November 2015 Introduction Apical periodontitis (AP) is an inﬂammatory process in the periapical tissues that may develop if bacteria infect the dental pulp space. Periapical status is, how- ever, not only a question of disease or no disease, but Correspondence: Lise-Lotte Kirkevang, Department of Endodontics, Institute of Clinical Dentistry, Faculty of Den- tistry, University of Oslo, P.B 1109 Blindern, 0317 N-OSLO, Norway (e-mail: l.l.kirkevang@odont.uio.no). International Endodontic Journal, 50, 5–14, 2017 © 2015 International Endodontic Journal. Published by John Wiley & Sons Ltd doi:10.1111/iej.12581 5