Mesial Root Tipping of the Maxillary Lateral Incisor to Facilitate Eruption of an Impacted Canine: A Retrospective Study.

Background/

Objectives

The maxillary lateral incisor (U2) root has been proposed to influence the eruption pathway of the maxillary canine. This retrospective study aimed to evaluate the association between mesial root tipping of the U2 and the eruption of impacted maxillary canine (IPU3), and to identify radiographic predictors of eruptive movement.

Methods

Orthopantomograms of 37 IPU3 from 29 patients aged 10-12 years were analyzed in this retrospective responder study; all included cases showed initiation of IPU3 eruption following U2 mesial root tipping, and this design was considered when interpreting potential selection bias and overestimation of effect. U2 and canine (U3) positions were measured at treatment initiation (T0) and at the 1-year follow-up (T1). Positional changes were analyzed using paired t-tests, Pearson's correlation, and multiple linear regression.

Results

Significant positional changes were observed for both U2 and U3 (all p < 0.001). The blockage point on the distal U2 root (2DBlock) shifted mesially by 2.0 mm, and U2 root angulation increased by 5.6° at the distal surface and 6.3° along its long axis. The U3 cusp tip (3Cusp) moved vertically by 3.7 mm, distally by 2.1 mm, and tipped distally by 7.5°. A strong correlation (r = 0.697) was observed between mesial root movement (2DHorz) and vertical cusp displacement (3Vert). Regression analysis identified 2DHorz as the only significant predictor of 3Vert (p < 0.001), explaining 51% of the variance; this indicates moderate explanatory power, while the remaining 49% suggests that additional biological, developmental, and three-dimensional spatial factors may also influence eruptive movement.

Conclusions

Mesial root tipping of the U2 facilitates IPU3 eruption in early adolescents (10-12 years), specifically in cases with non-palpable IPU3 in sector II and fully developed U2 roots. Horizontal repositioning of the U2 root may serve as a clinically relevant radiographic indicator for guiding interceptive treatment; however, these findings should be interpreted as associations rather than evidence of causality.