Figure 4 Measurement of the of impacted canine eruption path length. A line (1) is drawn indicating the shortest distance between the proximal contacts of the lateral incisor and the first premolar. Then a tangent (2) to the incisal edge of the lateral incisor and the buccal cusp tip of the first premolar and finally a perpendicular line (3) is drawn from the midpoint of the first line (1) to the tangent (2). The point where lines (2) and (3) intersect is defined as the correct crown cusp of the impacted canine. The eruption path length is defined as the distance between the cusp tip of the impacted tooth crown and the point of its anticipated correct position.