J Korean Assoc Oral Maxillofac Surg 2019; 45(6): 309~315
Modified difficult index adding extremely difficult for fully impacted mandibular third molar extraction
Jae-Young Kim, Hae-Sung Yong, Kwang-Ho Park, Jong-Ki Huh
Department of Oral and Maxillofacial Surgery, Gangnam Severance Hospital, Yonsei University College of Dentistry, Seoul, Korea
Jong-Ki Huh
Department of Oral and Maxillofacial Surgery, Gangnam Severance Hospital, Yonsei University College of Dentistry, 211 Eonju-ro, Gangnamgu, Seoul 06273, Korea
TEL: +82-2-2019-4560 FAX: +82-2-3463-4052
E-mail: omshuh@yuhs.ac
ORCID: https://orcid.org/0000-0002-7381-3972
Received July 22, 2019; Revised October 10, 2019; Accepted November 2, 2019.; Published online December 31, 2019.
© The Korean Association of Oral and Maxillofacial Surgeons.. All rights reserved.

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
 Abstract
Objectives: The aim of this study was to evaluate the validity of the existing classification and difficulty index of impacted mandibular third molars in clinical situations and propose a more practical classification system.
Materials and Methods: This study included 204 impacted mandibular third molars in 154 patients; panoramic x-ray images were obtained before tooth extraction. Factors including age, sex, and pattern of impaction were investigated. All impacted third molars were classified and scored for spatial relationship (1-5 points), depth (1-4 points), and ramus relationship (1-3 points). All variables were measured twice by the same observer at a minimum interval of one month. Finally, the difficulty index was defined based on the total points scored as slightly difficult (3-4 points), moderately difficult (5-7 points), very difficult (8-10 points), and extremely difficult (11-12 points).
Results: The strength of agreement of the total points scored and difficulty index were 0.855 and 0.746, respectively. Most cases were classified as moderately difficult (73.0%). Although only 13 out of 204 cases (6.4%) were classified as extremely difficult, patients classified as extremely difficult were the oldest ( P <0.05).
Conclusion: For difficulty classification, the authors propose one more difficult category beyond the existing three-step difficulty index: the clinician should consider the patient’s age in the difficulty index evaluation.
Keywords: Third molar, Tooth extraction, Impacted tooth, Classification


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31 December 2019
Vol. 45
No. 6 pp. 301~378

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