Fig. 4. Ramus relationship/space available. A. Class I. B. Class II. C. Class III. Eruption space was calculated as the ratio of the distance between the ascending ramus to the distal of second molar (a) and diameter of the impacted third molar (b), which was illustrated in Fig. 1. When eruption space (a/b) was larger than two-thirds, it was classified as class I, between one-third and two-thirds, it was classified as class II, and when smaller than one-third, it was classified as class III.
