Alignment of impacted maxillary canines: critical analysis of eruption path and treatment time

The aim of this study was to evaluate a possible correlation between treatment time and the distance covered by the canine tip during forced eruption of impacted maxillary canines. We also addressed the question whether it is possible to estimate the treatment time based on this data.

Orthopantomograms of 57 juvenile patients below 18 years of age with at least one palatally impacted canine were examined. We determined the position of the canine in relation to the neighboring teeth, its axial inclination and distance to the occlusal plane. We also introduced a new linear measurement representing the distance covered by the canine's crown tip during the alignment of the impacted tooth.

The length of overall treatment time and canine alignment, its axial inclination and the distance covered by the canine correlated significantly with the canine's position relative to its neighboring teeth. The newly-introduced linear measurement was the only measure that proved gender specific. With regression analysis we demonstrated that this measure is sufficient to predict the active treatment time for canine alignment (r(2) = 0.391). This indicates that 39.1% of the differences observed in active treatment time can be explained by variation in this new parameter.

The new measure introduced in this study provides a practice-oriented parameter with which to predict the treatment time for aligning impacted canines. Current 2D imaging diagnostics most likely restrict the ability to predict the length of therapy at 40%. Individual bone density and metabolism seem to have a strong influence on treatment time and must be taken into account for a more exact prognosis.