Incisor liability and its effects among East Asian children

Background/purpose: Incisor liability is the discrepancy in the sum of the mesiodistal crown width between the primary and permanent incisors. Incisor liability affects the integrity and eruption of the permanent incisors during the transition from the primary to permanent dentition. This study investigated the incisor liability in the primary dentition of Taiwanese children. Methods: The digital periapical films of 203 upper arches of 105 boys and 98 girls and 195 lower arches of 119 boys and 76 girls aged between 3 and 6 years were selected in this retrospective study. The mesiodistal crown widths of the primary and permanent incisors were measured using the medical imaging software for both arches. Differences in incisor liability values were statistically analyzed. Results: The mean ± standard deviation of the incisor liability values were 8.32 ± 1.88 and 6.91 ± 1.13 mm for the upper and lower arches, respectively, in all children. The incisor liability was closely related with the total crown widths of the permanent incisors for upper and lower arches. The incisor liability values were higher among boys than girls for the upper but not lower arch. Conclusion: Incisor liability differs depending on ethnicity. In Taiwanese children, incisor liability was closely related with the crown widths of the permanent incisors. The incisor liability values of boys were higher than those of girls in the upper arch but not the lower arch.