Impaction of Lower Third Molars and Their Association With Age: Radiological Perspectives

Methods

The study was approved by the ethical and research committee at the faculty of dentistry, University of Jordan, Approval no. (1558), and has been conducted in full accordance with the world medical declaration of Helsinki.

A total of 4600 orthopantomographs (OPGs) were retrieved, all OPGs taken in the Department of Dentistry at The University of Jordan Hospital between the years 2010 and 2014 were reviewed. A total of 3402 OPGs were excluded for the following reasons; 1) patient age less than 18 years, 2) patient age more than 26 years, 3) patients with craniofacial anomalies or syndromes, 4) poor quality images, 5) presence of orthodontic treatment, 6) fully erupted third molars, 7) third molars with fussed or dilacerated roots, 8) buccaly or lingually angulated third molars, 9) third molars requiring three dimensional assessments. The final sample therefore consisted of 1198 OPGs with 1810 impacted lower third molars (1224 bilateral impactions, 586 unilateral impactions).

During the period of the study all the patients were handled by the same technician and OPGs were taken by the same machine and processed by the same program (Kodak 8000C, France). Standard panoramic exposures are achieved following standard protocol. Two examiners reviewed all the OPGs and performed the following radiographic measurements according to William Sciller,^[8] which is presented and simplified in (Figure 1):

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Figure 1.

Demonstration of radiographic measurements William Sciller ⁸: (1) The retromandibular space, measured between the lines of the anterior border of the ramus to the most distal point of the lower 2nd molar. (2) The length of the horizontal line on the widest area of the crown. (3) The length of the roots. (4) The distance between the highest points of the impacted lower third molar tooth to the occlusal line. (5) Angulation of the third molar refers to the angle formed between dental long axis of the third molar tooth to the occlusal plane

1. The retromolar space. Measured between the lines of the anterior border of the ramus to the most distal point of the lower 2nd molar.

2. The length of the horizontal line on the widest area of the crown.

3. The length of the roots.

4. The distance between the highest points of the impacted lower third molar tooth to the occlusal line.

5. Angulation of the third molar refers to the angle formed between dental long axis and occlusal plane: Horizontal < 20°; Mesioangular = 20–80°, Vertical = 80–100°; Distoangular ≥100°.

The study used the Kodak software that has built in measuring and marking tools that would calculate the determined angles and lines, and made the OPGs a valuable radiographic technique to be used for location assessment of the lower third molars. (Figure 2) shows an OPG with the measurements annotated on it.

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Figure 2.

An orthopantograph (OPG) as an example for the measurements of the lower third molar angles

Statistical analysis was performed using SPSS for Windows release 16.0 (SPSS Inc., Chicago, IL, USA). Descriptive statistics were generated. Student's t-test and Pearson's Correlations test (r) were used to examine differences and correlations between groups. Results were considered significant if P-values were less than 0.05.

BMC Oral Health. 2018;18(58) © 2018 BioMed Central, Ltd.