The Journal
E . Torque
The accuracy of incisal torque was 67 %, the anterior torque was 62 % and the posterior torque was 42 % 5 . In the study of Castroflorio ( et al ), 12 upper anterior teeth in six patients were the subjects of research , but only nine teeth showed greater root movement than the crown when analyzed . The results showed that an average torque of nine teeth at T0 ( beginning ) was 20.95 degrees in virtual setup and 21.12 degrees in the scan cast . At T1 ( end ) the average change of torque between T1 and To was 10.4 degrees . This shows that the Invisalign with power ridges is a good alternative for the control of root torque of upper anteriors in some selective cases 13 . According to Djeu G et al the fixed braces had OGS scores significantly higher than the Invisalign scores in labiolingual tip . This suggests that Invisalign can not create the appropriate root torque , especially in the posterior 4 .
F . Rotations
Before rotating the teeth , a space must be created between the teeth by IPR or expansion . The flat surfaces of the incisors labially and lingually support the rotation , while the rounded teeth , like premolars and canines , make rotating movement more difficult . Rotating the teeth with Invisalign showed a difference between the different shapes of teeth . The accuracy of rotation for Invisalign was found to be ranged from 35.8 to 60 % 10 .
AUTHOR
The average accuracy of anterior rotation was 43.2 %. The highest accuracy of rotation was 54.2 % for the maxillary central incisors and the lowest accuracy of rotation was 29.1 % for the mandibular canines . At the rotation more than 15 degrees , the accuracy of the canine rotation decreased significantly , the accuracy of the maxillary canine rotation was only 18.8 %, and the mandibular canine was only 33.2 %. However at the rotation where it was less than 15 degrees , the accuracy increased to 35.8 % for the maxillary canines and 27.9 % for the mandibular canines 9 .
In another study , Kravitz et al . 2008 assessed the influence of attachments and interproximal reduction ( IPR ) on the accuracy of canine rotation with Invisalign , made comparisions on the rotations of canines between the virtual pretreatment model and the virtual posttreatment model using ToothMeasure for model superimposition . The sample was divided into 3 groups : one group using attachments only ( AO ), another group using interproximal reduction ( IPR ) only ( IO ) and the last group received no intervention ( N ). The average amount of programmed rotation was 11.8 degrees . The average accuracy of canine rotation was 35.8 %, in which the IO group had the highest accuracy ( 43.1 %), and the lowest was the N group ( 30.8 %). The AO group had the average accuracy of canine rotation ( 33.3 %). However , there were no significant difference statistically ( P = . 343 ) between the 3 groups in the accuracy of canine rotation between maxillary and mandibular canines 8 .
INTRUSION
Nguyen and Cheng [ 5 ] Incisor 60 % Premolar 47 % Molar 52 %
Kravitz et al . 2009 Anterior 43.2 %
Kravitz et al . 2008 [ 8 ] Canine 35.8 %
7 Vol . 14 No . 1 Jan-Apr 2018