Methods: Eight subjects (five males, 3 females) who required maxillary first premolar extractions had maxillary canines retracted segmentally for 84 days using 4 kPa of stress on one side and 78 kPa on the other. Each subject scored the McGill Pain Questionnaire-Short Form modified for orthodontic patients (MMPQ-SF), Visual Analogue Scale (VAS), and Present Pain Intensity (PPI) for both sides 13 times encompassing 4 phases: baseline, post-placement of separators, early and later tooth-loading. Pain intensity and quality were investigated: over time for differential effects of stress and gender using mixed effects regression models and by treatment phase using single factor repeated measures ANOVA and Fisher-Hayter post-hoc tests.
Results: Time significantly affected pain scores (p=0.0001); in general, reported pain peaked at Day 1 after load initiation, decreasing with time thereafter. Pain intensity (MMPQ-SF, VAS, PPI) and generalized/emotional subscale scores showed no significant differences between stresses (p>0.05) but localized subscale scores were significantly higher for 78 kPa compared to 4 kPa sides (p=0.011). Females reported significantly higher VAS (p=0.024) and PPI (p=0.001) compared to males. Also, significantly higher MMPQ-SF and localized subscale scores (all p≤0.023) were found for post-placement of separators and early tooth-loading compared to baseline.
Conclusions: During tooth translation, significant differences in pain intensity and quality were found over time; however only localized pain quality was different for loads of 4 versus 78 kPa and only pain intensity showed gender differences. Funded in part by the American Association of Orthodontists Foundation.
Keywords: Human, Loading, Orthodontics and Pain