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ortho - the international C.E. magazine of orthodontics

18 I I study_ lower incisor stability _Intro Each year in Canada, second-year orthodontic residents are tasked with summarizing their thesis ideas and then converting them to a poster-style format for the scientific session of the annual Cana- dian Association of Orthodontics (CAO). This annual rite of passage does more than simply provide each resident with a rewarding technical experience — it also provides all of orthodontics with some valuable research. Here is one of these resident studies. _Study “Lower Incisor Stability Following Orthodontic Treatment Using a Fixed-Spring Induced Appliance.” Crichton J*, Wiltshire WA, Hechter FJ, Ahing S. De- partment of Orthodontics, University of Manitoba, Winnipeg, Canada. Objectives To evaluate the lower incisor (Li) changes after completion of comprehensive fixed treatment in subjects with different facial patterns who were treated with a FSIA for Class II correction. Hypothesis Once the lower incisor position has been estab- lishedattheendofaFSIAtreatment,theywillremain stable in the same position after fixed treatment. Subjectsandmethods Aretrospectivechartreviewwasundertaken,con- sistingof115subjectswithClassIImalocclusions,43 maleand72female.Theaveragelengthoftreatment wasoneyear andsevenmonths(S.E±0.57).Theaver- ageageofthesubjectsatT1was13.7years(S.E±1.5). Subjectswerethencategorizedintothreegrowth types based on pre-treatment (T0) cephalometric variables (MPA, Y-axis, LFH) with 29 brachycephalic, 53 mesocephalic and 33 dolichocephalic subjects resulting. Data was compiled using digital lateral cephalometric analysis of the post-treatment FSIA subjects’ (T1) and post-treatment comprehensive fixed therapy subjects’ (T2) radiographs. Statistical evaluation used a mixed model re- peated command to calculate marginal means and a post-hoc analysis to determine pairwise differences with the Tukey’s test, reporting least square means. Results Dental changes induced by fixed treatment in- cluded: 1. retroclination of the Li (LI-MP 5.7-9.7°±1.3 p<0.05) 2. retrusion of Li (LI-APo 0.1-1.0mm ±0.3mmp<0.05) There was no significant difference among the different facial groups (p>0.05). There was an in- creasedtrendoflessincisorretroclinationandretru- sion for the dolichocephalic group. Conclusions Incisor proclination resulting from the FSIA is reversed after fixed orthodontic treatment, and Li tendtoretroclineandretrude.Useofzeroornegative torque prescription in the Li bracket and Li upright- ing mechanics throughout treatment ensure the Li returntoapositionbetweentheinitialtreatment(To) and the final position established with the FSIA (T1). Facial growth pattern demonstrate no relation to the amount of Li movement. The dolicocephalic group shows less Li change when compared to the other facial patterns._ ortho1_2014 Abstract thinking

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