J Korean Assoc Oral Maxillofac Surg.  2020 Oct;46(5):328-334. 10.5125/jkaoms.2020.46.5.328.

Development and validation of a difficulty index for mandibular third molars with extraction time

• Ku JK
• Chang NH
• Jeong YK
• Baik SH
• Choi SK

• KMID: 2508257
• DOI: http://doi.org/10.5125/jkaoms.2020.46.5.328

Abstract

Objectives
This study aimed to validate the effectiveness of a recently proposed difficulty index for removal of impacted mandibular third molars based on extraction time and suggest a modified difficulty index including the presence of pathologic conditions associated with third molars.
Materials and Methods
This retrospective study enrolled 65 male patients younger than 25 years with third molars. Extraction time was calculated from start of the incision to the last suture. The difficulty scores for third molars were based on spatial relationship (1-5 points), depth (1-4 points), and ramus relationship (1-3 points) using cone-beam computed tomography. The difficulty index was defined as follows: I (3-4 points), II (5-7 points), III (8-10 points), and IV (11-12 points). The modified difficulty score was calculated by adding one point to the difficulty score if the third molar was associated with a pathologic condition. Two modified difficulty indices, based on the presence of pathologic conditions, were as follows: the half-level up difficulty index (HDI) and the one-level up difficulty index (ODI) from the recently proposed difficulty index.
Results
The correlations between extraction time and difficulty index and or modified difficulty indices were significant (P<0.001). The correlation coefficient between extraction time and difficulty index was 0.584. The correlation coefficients between extraction time and HDI and ODI were 0.728 and 0.764, respectively.
Conclusion
Extraction time of impacted third molars exhibited a moderate correlation with difficulty index and was strongly correlated with the modified indices. Considering the clinical implications, the difficulty index of surgical extraction should take into consideration the pathologic conditions associated with third molars.

Keyword

Computed tomography; Classification; Tooth extraction; Impacted tooth; Third molar

Figure

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  Fig. 1 Photographs of the surgical extractions with operculectomies. A. Preoperative photograph of the patient in Fig. 2. B. Incision for the operculectomy. C. After operculectomy, the impacted mandibular third molar was exposed. D. Odontomy of the third molar was performed. E. Extraction of the third molar was completed. F. Postoperative photograph after suturing with collagen plug packing.

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  Fig. 2 Measurement and classification of the impacted third molars in cone-beam computed tomography according to a previous study conducted by Kim et al.5. The spatial relationship was classified based on the angle measured between the long axis of the impacted third molar and the adjacent second molar (yellow lines and an asterisk mark). Depth was classified based on the line connecting the cementoenamel junction of the adjacent second molar (dotted blue line). Ramus relationship/space available was subcategorized based on the ratio between the distance from the ascending ramus to the distal of the second molar (a) and the diameter of the impacted third molar (b) (pink arrows).

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  Fig. 3 The correlation between the extraction time and the difficulty index. The correlation coefficient was 0.584, suggesting a moderate positive correlation (P<0.001).

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  Fig. 4 The correlation between the extraction time and the modified difficulty indices. A. The correlation between the extraction time and the half-up difficulty index. The correlation coefficient was 0.728, suggesting a strong positive correlation (P<0.001). B. The correlation between the extraction time and the half-up difficulty index. The correlation coefficient was 0.764, suggesting a strong positive correlation (P<0.001).

Reference

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