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An In Vitro Study on Aligner Rotational "Lag" with In-Office Clear Aligner Therapy


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The purpose of this study was to investigate the amount of rotational lag in Clear Aligner Therapy (CAT) in reference to maxillary anterior teeth. Methods: A 3D digital model with ideal alignment of maxillary teeth nos. 2-15 with cutouts at teeth nos. 6, 8, and 10 was fabricated. Plastic teeth were set in areas of cutouts in ideal alignment using a stent and then cutouts were filled with wax. A CAT series was created to rotate the plastic teeth from ideal to 9 deg of rotation in 6 aligners (1.5 deg between each aligner) using a hot water bath. Initial and final digital scans were compared via superimposition to calculate the amount of rotation. Lag was calculated by subtracting the amount of achieved rotation from 9 deg. Results: There were significant differences in rotational lag among tooth shapes (F(2, 105) = 13.14, p <.0001). Tooth no. 8 lag (Mean = 3.12, SD = 1.76) was significantly smaller than tooth no. 6 (Mean = 5.46, SD = 2.23)(p <.0001) and tooth #10 (Mean = 4.95, SD = 2.08) (p = 0.0007). No significant difference was found between tooth no. 6 and no. 10 (p = 0.55). Conclusions: The CAT series was significantly more efficient in rotating max central incisors than lateral incisors and canines. None of the teeth tested completed the full 9 deg of rotation.



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